the kinematics of movements along the insubric line and the emplacement of the ivrea zone schmid sm zingg a and handy m 1987 the kinematics of movements along the insubric line and the emplacement of the ivrea zone in h j zwart m martens i van der molen c w passchier c spiers and r l m vissers editors tectonic and structural processes on a macro meso and micro scale tecta a hys 135 47 66 the insubric line west of locamo is characterized by a 1 km thick greenschist facies mylonite belt east of locamo these mylonites are overprinted by a discrete brittle fault the mylonites are derived from basement units of the central alps sesia zone and the southern alps ivrea zone as well as from the permo mesozoic cover of the southern alps canavese sense of shear criteria indicate that the mylonites accomm ated backt s g followed by dextral strike slip motion mylonitization during backtbrusting was synchronous with backfolding of the central alpine nappes under higher metamorphic conditions a horizontal temperature gradient resulted from the rapid juxtaposition of the warm central alpine block against the cold southern alpine block mylonites formed during the later dextral strike slip event are related to large transcurrent displacements in the central alps deduced from regional kinematic considerations thus both mylo t ation events are contempor eous with deformation to the north and south of the insubric line insubric phase extensively modifying the pre insubric crustal configuration of the alps the insubric phase post dates the bergell intrusion 30 m y the emplacement of the geophysical ivrea body is a combined effect of vertical uplift due to e w directed crustal thinning during the early jurassic and underplating by continental crust associated with late cretaceous compression a deep crustal normal fault pogallo line subsequently rotated during tertiary alpine orogenesis separates deeper parts of the southern alpine crust ivrea zone from intermediate crustal levels strona ceneri zone the rigid ivrea body localir ed large strains within the insubric mylonite belt and is responsible for the present curvature of the insubric line in uetion

prediction of debris flow inundation areas using empirical mobility relationships abstract a method proposed for delineating lahar hazard zones in volcanic valleys is adapted to debris flows the original method is based on two predictive equations that relate the lahar volume to the cross sectional inundated area and to the planimetric inundated area these predictive equations were derived by combining a scaling analysis of lahar kinematics with the statistical analysis of data for 27 historical lahars this paper tests the applicability of this approach to debris flow fans forty debris flow basins in the italian alps were surveyed and data on 27 historical debris flow events were collected in the field or by means of aerial photo analysis collected data reveal that the flow area a and the planimetric area b of a debris flow are linearly correlated to the debris flow volume v on a logarithmic scale with high statistical significance moreover the computed regression equations are very similar to those obtained from other published datasets on debris flows leading to the global fitting equations a 0 08 v 2 3 and b 17 v 2 3 these predictive equations are then implemented in an automated code dflowz that delineates the inundated area on a debris flow fan on the basis of a user specified debris flow volume taking the statistical uncertainty in the prediction into account dflowz is simple reproducible and it can handle both confined and unconfined flow the model is tested against 10 historical debris flow events providing a satisfactory agreement between observed and computed inundated areas in spite of the limitations due to dem accuracy and statistical uncertainty of the regression parameters test results show that the method can be useful for practical applications

numerical study on the entrainment of bed material into rapid landslides the entrainment of channel path material plays an important role during runout of many rapid landslides such a mechanism is able to change the mobility of a flow significantly through rapid chang

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

numerical modelling of entrainment deposition in rock and debris avalanches abstract rock and debris avalanches as well as debris flows are characterized by peculiar behaviour influenced by geometry of the initial failure surface topography involved materials involved and water content during their motion rock avalanches can entrain large volumes of sediments both in a dry and in a saturated state entrained dry material has generally the consequence to reduce the total landslide runout whereas entrainment of almost saturated material can have more complex consequences we use a finite element code to simulate the motion of a moving landslide mass on materials with different properties and along very sharp topographies erosion and deposition can be modelled as well as interaction with obstacles of different characteristics we present two examples of the modelling problems and capabilities we simulated the runout of a rock avalanche on a ground formed by alluvial material under dry and saturated conditions this material can be entrained and plowed by the impacting and running rock avalanche material sensitivity of the erosion and transport mechanisms has been analysed by performing different analyses the simulated case study is the 6 10 5 m 3 arvel rock avalanche 1922 switzerland for which a reliable set of pre and post failure observations is available final geometry mass redistribution velocities and runup are used to validate the model capabilities and study the effects of different material properties

effect of rock mass and discontinuity mechanical properties and delayed rock supporting on tunnel stability in an underground mine abstract in this paper the rock mass stability around the tunnels in an underground mine is investigated using the distinct element method a three dimensional model was developed based on the available geological geotechnical and mine construction information it incorporates the inclined lithologies including a weak interlayer the persistent and non persistent faults and a complex tunnel system the strain softening constitutive model was prescribed for the rock masses in the numerical model the continuously yielding joint model was used to describe the non linear behavior of the faults to account for the deformations occurred between the excavations and rock supporting the delayed installation of supports was implemented by using the stress relaxation method numerical analyses were performed to study the effects of the post failure constitutive parameters of the rock masses the mechanical properties of faults and the delayed supporting on tunnel stability the following results are presented a the rock mass deformations and failure zones around the excavations b the joint shear displacements of the major fault and c the failure conditions of the applied supports satisfactory comparisons are obtained between the predictions based on numerical modeling and the field deformation measurements the analysis procedures presented in this study are applicable for stability assessment of various underground rock excavation projects located in different parts of the world having different geological settings and complex engineering situations

elementary theory of bed sediment entrainment by debris flows and avalanches 1 analyses of mass and momentum exchange between a debris flow or avalanche and an underlying sediment layer aid interpretations and predictions of bed sediment entrainment rates a preliminary analysis assesses the behavior of a coulomb slide block that entrains bed material as it descends a uniform slope the analysis demonstrates that the block s momentum can grow unstably even in the presence of limited entrainment efficiency a more detailed depth integrated continuum analysis of interacting deformable bodies identifies mechanical controls on entrainment efficiency and shows that entrainment rates satisfy a jump condition that involves shear traction and velocity discontinuities at the flow bed boundary explicit predictions of the entrainment rateeresult from making reasonable assumptions about flow velocity profiles and boundary shear tractions for coulomb friction tractions predicted entrainment rates are sensitive to pore fluid pressures that develop in bed sediment as it is overridden in the simplest scenario the bed sediment liquefies completely and the entrainment rate equation reduces toe 2 1gh1 cos 1 1 v 1 where is the slope angle 1 is the flow s coulomb friction coefficient h1 is its thickness 1 is its degree of liquefaction and v 1is its depth averaged velocity for values of 1ranging from 0 5 to 0 8 this equation predicts entrainment rates consistent with rates of 0 05 to 0 1 m s measured in large scale debris flow experiments in which wet sediment beds liquefied almost completely the propensity for bed liquefaction depends on several factors including sediment porosity permeability and thickness and rates of compression and shear deformation that occur when beds are overridden

identifying post earthquake debris flow hazard using massflow catastrophic debris flows are common after large earthquakes and pose a significant risk for recovering communities the depositional volume of these large debris flows is often much greater than the initiation volume suggesting that bulking of the flow plays an important role in determining their volume speed and runout distance observations from recent earthquakes have driven progress in understanding the relationship between triggering rainfall events and the timing of post earthquake debris flows however we lack an adequate mechanism for quantifying bulking and applying it within a hazard context here we apply a 2d dynamic debris flow model massflow that incorporates a process based expression of basal entrainment to understand how debris flow bulking may occur within post earthquake catchments and develop hazard maps focussing on catchments in the epicentral area of the 2008 mw 7 9 wenchuan earthquake we first parameterised the model based on a large debris flow that occurred within the hongchun catchment before applying the calibrated model to adjoining catchments a model sensitivity analysis identified three main controls on debris flow bulking the saturation level of entrainable material along the flow pathway and the size and position of initial mass failures the model demonstrates that the difference between small and very large debris flows occur across a narrow range of pore water ratios below 0 65 flows falter at the base of hillslopes and come to rest in the valley bottom above 0 70 they build sufficient mass and momentum to sustain channelised flow and transport large volumes of material beyond the valley confines finally we applied the model across different catchments to develop hazard maps that demonstrate the utility of massflow in post earthquake planning within the wenchuan epicentral region

erosion of steepland valleys by debris flows episodic debris flows scour the rock beds of many steepland valleys along recent debris flow runout paths in the western united states we have observed evidence for bedrock lowering primarily by the impact of large particles entrained in debris flows this evidence may persist to the point at which debris flow deposition occurs commonly at slopes of less than 0 03 0 10 we find that debris flow scoured valleys have a topographic signature that is fundamentally different from that predicted by bedrock river incision models much of this difference results from the fact that local valley slope shows a tendency to decrease abruptly downstream of tributaries that contribute throughgoing debris flows the degree of weathering of valley floor bedrock may also decrease abruptly downstream of such junctions on the basis of these observations we hypothesize that valley slope is adjusted to the long term frequency of debris flows and that valleys scoured by debris flows should not be modeled using conventional bedrock river incision laws we use field observations to justify one possible debris flow incision model whose lowering rate is proportional to the integral of solid inertial normal stresses from particle impacts along the flow and the number of upvalley debris flow sources the model predicts that increases in incision rate caused by increases in flow event frequency and length as flows gain material downvalley are balanced by rate reductions from reduced inertial normal stress at lower slopes and stronger less weathered bedrock these adjustments lead to a spatially uniform lowering rate although the proposed expression leads to equilibrium long profiles with the correct topographic signature the crudeness with which the debris flow dynamics are parameterized reveals that we are far from a validated debris flow incision law however the vast extent of steepland valley networks above slopes of 0 03 0 10 illustrates the need to understand debris flow incision if we hope to understand the evolution of steep topography around the world

self potential global tomography including topographic effects this paper is an extension of a previous study in which the principles of self potential ground surface tomography were outlined the new arguments which are here set forth are the proper accounting for the topographic effects and a robust approach to global 3d tomography the 2d case is initially considered in order to facilitate a full understanding of the new method in order to gauge the topographic distortions the concepts of slope effect and surface regularization are introduced as suitable means to compute point by point correction factors of the measured self potential data prior to the recognition of the tomographic images of the primary and induced electric sources underground the tomographic approach is then developed by introducing again the concepts of the scanning function and of the charge occurrence probability function which were amply dealt with in the previous paper the new approach to 3d global tomography means here the composition of charge occurrence probability functions related to any two orthogonal surface components of the natural electric field in order to account fully for the total surface component of the self potential field and hence to elicit the greatest amount of information two field examples are presented to show the full effectiveness of the proposed method they refer respectively to a near surface investigation for archaeological purposes and to a very deep investigation in an active volcanic area

post failure stage simulation of a landslide using the material point method abstract traditional numerical methods such as the finite element method are usually used to analyse the slope response in the pre failure and failure stages under the assumption of small deformations however these methods are generally unsuitable for simulating the post failure stage of landslides due to the occurrence of large deformations the material point method mpm is a numerical technique capable to overcome this limitation in the present study mpm is used to carry out a two dimensional analysis of the run out process of the senise landslide that occurred in southern italy in 1986 accuracy of the method is assessed by comparing the final geometry of the landslide observed just after the event and the magnitude of the measured displacements to those provided by the numerical simulation the calculation results match fairly well the observed ones when two slip surfaces detected by the inclinometers are accounted for in the analysis an additional improvement of simulation is achieved taking into account the presence of some buildings and retaining walls existing in that area kinematics of the landslide is also investigated the results show that the senise landslide was a translational slide moving along two planar slip surfaces located in thin layers of clayey silt in addition these results demonstrate that a suitable analysis of the post failure stage can lead to a better understanding of the complex mechanical processes that characterise some landslides and thereby help in establishing the most effective stabilization measures

numerical analysis of dynamics of debris flow over erodible beds in wenchuan earthquake induced area the basal entrainment of debris flows play a significant role in its amplification and the final volume of deposition could be several to hundred times of its initial volume in this paper the shallow water equations coupled with basal material entrainment applied in debris flows have been given to demonstrate the amplification a new basal entrainment model taking advantage of both coulomb and voellmy frictional laws are proposed providing a unified formula to simulate the stop and go process of debris flows both time and space second order maccormack tvd finite difference method is suggested to solve the coupled equations numerical comparisons with usgs flume experiment and hongchun gully debris flow in wenchuan earthquake induced area are carried out to prove its effectiveness it is established that the momentum exchange term between the flows and the basal materials has a significant influence on the dynamic characteristics and the entrainment effects are essential to model the dynamic process of debris flows in an earthquake induced area c 2014 elsevier b v all rights reserved

engineering behaviour of phyllites abstract the physico mechanical behaviour of intrinsically anisotropic rocks cannot be assessed through common engineering experiences due to a number of governing intrinsic factors e g variation of mineral assemblage fabric and physical and mechanical properties the study of such rocks under the stress conditions existing within the drilling reach of the earth s crust has not been given due attention not even in laboratory simulated conditions therefore it seemed worthwhile to undertake a comprehensive study using three varieties of intrinsically anisotropic phyllites obtained from the vicinity of the chamera hydroelectric project site in the himalayan region attention has been paid to their petrographic and petrofabric analyses through thin sections x ray diffraction and scanning electron microscopy and the physical and geotechnical properties with special reference to their anisotropyp compression tests were run from unconfined to a maximum confining pressure 3 of 70 mpa for the three phyllites at specified orientation angles angle between the plane of weakness and the direction of the major principal stress 1 of 0 15 30 45 60 75 and 90 thus the physico mechanical response of the phyllites as a function of confining pressure and the orientation angle has been determined and the degree of anisotropy could be quantified in terms of physically measureable parameters

erosional effects on runout of fast landslides debris flows and avalanches a numerical investigation the mechanism of mass changes in debris transportation process is an important topic in the study of fast landslides debris flows and avalanches basal erosion is recognised as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along their non slip contact surface in this paper we propose a new concept of yield rate and establish the erosional relationship to bridge these two systems a pertinent mathematical model and numerical implementation are formulated parametric numerical experiments are conducted to compare the erosional effects the simulated results are consistent with available experimental and field observations the influence of the involvement of the erosive material on runout behaviour and the global mobility of the moving material are elucidated the proposed method is then employed to analyse a recent debris flow event in northern italy the excellent match to the field data gives it a plausible potential application to the analysis of this type of gravity driven flow with significant erosion defined in a dimensionless form the proposed yield rate can be estimated conveniently in general geotechnical practices

dynamic modelling of entrainment in rapid landslides entrainment of path material is an important feature of many rapid landslides the associated increases in volume and changes in flow character can significantly influence mobility a simple material entrainment algorithm based on the assumption of natural exponential growth with displacement has been incorporated into a new computer model designed to simulate rapid landslide motion across 3d terrain the user controls the growth rate and can also implement a change in rheology at the onset of entrainment a hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions a back analysis of the 1999 nomash river landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment key words landslides debris flows rock avalanches entrainment erosion dynamic modelling

numerical simulation of debris flows a key requirement in the assessment of landslide risk in such densely populated urban areas as hong kong consists of the prediction of potential runout distance or the extent of the subsequent debris flow this paper presents a three dimensional dynamic model of unsteady gravity driven debris flow the lagrangian galerkin finite element method is used to determine the nodal velocity and depth of soil column elements within the sliding mass with the momentum and mass conservation mathematically closed within the soil column elements the numerical solution also features a lumped mass matrix and a volume weighted procedure the method of least squares approximation plays a smoothing role which enhances stability and efficiency of the numerical solution scheme the nodal elevation during sliding is obtained via a dynamic bilinear interpolation of the elevation function for the base of the sliding mass furthermore the accuracy robustness and generality of this method are validated by experimental results

numerical simulation of debris flow behavior incorporating a dynamic method for estimating the entrainment abstract there is a pressing need to estimate debris flow entrainment because several lines of studies have substantiated that the magnitude of a debris flow may grow manyfold due to sediment entrainment in this paper we present a two dimensional numerical model of debris flow behavior for estimating entrainment over complex topography the model is governed by a numerical integration of the depth average motion equations using shallow water approximation the governing equations are numerically solved using the semi lagrangian method in an explicit finite difference grid compared to previous models the presented model highlights the importance of entrainment and incorporates a physically based dynamic method to estimate the entrainment rate the entrainment rate can be predicted using reasonable assumptions regarding the velocity profile of the debris flow and the rapidly changing pore pressure of the bed sediment the stability of the presented model is first illustrated by a hypothesized dam breaking problem the effectiveness of the implemented model entrainment process is subsequently tested on the 2010 yohutagawa debris flow event in japan the test indicates that the presented method can be satisfactorily used to simulate debris flow behavior and the entrainment process a discussion regarding the advantages and limitations of the model concludes the paper

comparison of two depth averaged numerical models for debris flow runout estimation this paper analyses an important aspect of the continuum numerical modelling of rapid landslides as debris flows by using the same rheological parameter values are the results obtained with code

positive feedback and momentum growth during debris flow entrainment of wet bed sediment debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep debris mantled slopes the flows can then grow dramatically in size and speed as they entrain material from their beds and banks but the mechanism of this growth is unclear indeed momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged here we use data from large scale experiments to assess the entrainment of bed material by debris flows we find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows the increased pore pressure facilitates progressive scour of the bed reduces basal friction and instigates positive feedback that causes flow speed mass and momentum to increase if dryer bed sediment is entrained however the feedback becomes negative and flow momentum declines we infer that analogous feedbacks could operate in other types of gravity driven mass flow that interact with erodible beds the mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear large scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed leading to reduced friction and progressive scouring of the base

entrainment of bed material by earth surface mass flows review and reformulation of depth integrated theory earth surface mass flows such as debris flows rock avalanches and dam break floods can grow greatly in size and destructive potential by entraining bed material they encounter increasing use of depth integrated mass and momentum conservation equations to model these erosive flows motivates a review of the underlying theory our review indicates that many existing models apply depth integrated conservation principles incorrectly leading to spurious inferences about the role of mass and momentum exchanges at flow bed boundaries model discrepancies can be rectified by analyzing conservation of mass and momentum in a two layer system consisting of amoving upper layer and static lower layer our analysis shows that erosion or deposition rates at the interface between layers must in general satisfy three jump conditions these conditions impose constraints on valid erosion formulas and they help determine the correct forms of depth integrated conservation equations two of the three jump conditions are closely analogous to rankine hugoniot conditions that describe the behavior of shocks in compressible gasses and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries grain fluid mixtures commonly behave as compressible materials as they undergo entrainment because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow if no bulk density change occurs then only the shear traction jump condition applies even for this special case however accurate formulation of depth integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion

modelling the space time evolution of bed entrainment for flow like landslides abstract the paper discusses the space time evolution of bed entrainment for some typical flow like landslides in three different test areas first the attention is focused on debris avalanches da whose lateral spreading is highly affected by bed entrainment two cases of debris avalanches turning into debris flows df i e channelized flows are then investigated to discuss the potential occurrence of complex bed entrainment scenarios a quasi 3d depth integrated coupled sph smooth particle hydrodynamic model is used the numerical results show that i the eroded thicknesses have maximum values in the intermediate portion of the debris avalanche path and ii the computed time variations of eroded thicknesses and the entrainment rates are consistent with those indicated in recent literature for das at the studied areas in addition the computed scenarios are differentiated in terms of unitary flow discharge identifying the typical behaviour of small volume da landslides propagating inside gullies as dfs and combined dfs and das

marine self potential gradient exploration of the continental margin the self potential sp method for mineral exploration is seldom used on land primarily because of electrode noise problems and nonunique interpretations marine measurements of the horizontal gradient of the sp field on the other hand are relatively simple to make with an array of electrodes towed behind a ship with low ship speeds of 5 to 10 km hour dense spatial sampling 1 m can be obtained with resolution of better than 1 v m in this paper we report on gradient sp data recorded on the continental shelf of south australia by a horizontal array of towed electrodes approximately 20 m above the seafloor ocean waves and swells with periods of 5 to 15 s yielded large amplitude signals 20 v m but subseafloor mineralization produced sp gradient anomalies of 50 v m and widths of 2 km or more in a number of parallel traverses integrating the observed sp gradients along each line delineated sp anomalies of amplitude up to 100 mv self potential and magnetic anomaly data show limited spatial cor

entrainment of debris in rock avalanches an analysis of a long run out mechanism many rock avalanches entrain and liquefy saturated soil from their paths evidence for this includes mud displaced from the margins of rock avalanche deposits substrate material smeared along the base of deposits extrusion of liquefied soil upward through the deposits and increases of volume a hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility although the process has been discussed in the literature for more than 100 years few detailed and quantitative descriptions exist the main purpose of this paper is to describe two recent cases from british columbia canada where rockslides entrained substrate on a very large scale influencing the character of the events estimated volume balance curves based on detailed field mapping are provided for both cases dynamic analyses are carried out using a numerical model and using the same set of rheological parameters the mechanism of material entrainment and displacement is discussed the data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide transitional between rock avalanche and debris avalanche many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate

insights into the catastrophic xinmo rock avalanche in maoxian county china combined effects of historical earthquakes and landslide amplification abstract a large and catastrophic rock avalanche occurred at the xinmo village in the maoxian county of the sichuan province of china on june 24 2017 the avalanche destroyed 64 houses and killed 10 people and 73 people were reported to be missing in this study we focused on the contributions of six historical earthquakes to the collapse of rocks in the source area and the landslide amplification caused by the entrainment of pre existing deposits on the landslide path the historical earthquakes in this area contributed different levels of damage on the source rocks particularly the 1933 diexi earthquake induced a few initial cracks in rocks at the crest of the steep hillslope under the combined time effects of long term weathering and gravity the rock blocks in the source area were detached from the crest along the intersecting cracks and over dip soft layer namely the sliding surface the avalanche was amplified by the entrainment of colluvium on its path the influence of the colluvium on the movement process of the xinmo landslide was modelled by the gpu based parallel discontinuous deformation analysis dda method and the effect of the impact and entrainment in the debris flow was rigorously analysed the results indicate that the impact and entrainment can continuously increase the volume of debris flow and the thickness of the colluvium was established to be in the range of 25 9 33 9 m based on the analysis of the deposit pattern and movement duration of the avalanche there were numerous unstable rocks induced by historical earthquakes at the crests of steep hill slopes in the earthquake stricken area with long term damage caused by environmental factors and gravity the failure of unstable rocks with high potential energy is likely to cause severe disasters the excess pore water pressure likely to be present in the colluvium or deposits during impact and entrainment can considerably reduce the effective stress and degrade friction resistance along the runout path as a result the landslide can be intensively amplified owing to the effect of impact and entrainment under a lower friction resistance

a depth integrated sph model for debris floods application to lo wai hong kong debris flood of august 2005 in this work an approach to representing debris floods and flows is proposed based on a depth integrated mathematical model and smooth particle hydrodynamics numerical technique the main contribu

numerical simulation of the propagation process of a rapid flow like landslide considering bed entrainment a case study abstract bed entrainment plays an important role in the run out process of a flow like landslide a limited number of studies have investigated the influence of entraining loose materials on the mechanical properties of a landslide and some of them have considered bed entrainment either by mechanical or empirical methods in this paper a modified finite difference model was used to analyze the propagation process of a typical flow like landslide with bed entrainment that occurred in the jingyang loess tableland china in this model the mechanical parameters of the sliding mass were modified according to the local entrainment depth triaxial consolidated undrained cu tests and ring shear tests were conducted to obtain the mechanical parameters needed in the numerical simulation the triaxial cu tests were conducted on three intact loess samples taken at the back scarp of the landslide and the ring tests were conducted on gravelly sand samples taken from the first terrace of the jinghe river which includes the landslide deposit the results show that both the simulated run out distance and final covering area agreed well with the field data the modified model revealed the propagation process of this landslide a major contribution of this study is that entraining the saturated gravelly sand contributed to the flow like movement of the landslide the case study investigated here is helpful for better an understanding of the flow like transformation mechanism in addition the numerical model adopted in this paper can be effectively used to assess or predict the propagation processes of similar landslides

interplay of rheology and entrainment in debris avalanches a numerical study flow type landslides are a major global hazard they occur worldwide and are responsible for a large number of casualties significant structural damage to property and infrastructure and economic losses the features of debris avalanches are particularly important as they involve open slopes and affect triangular source areas when initial slides turn into avalanches through further failures or eventual soil entrainment in this paper the propagation stage of debris avalanches is numerically modelled to provide information such as the propagation pattern of the mobilized material and its velocity thickness and run out distance the use of a depth integrated model has the following advantages i it adequately accommodates the irregular topography of real slopes which greatly affects the evolution of the propagation stage and ii it is less time consuming than full three dimensional approaches the model is named geoflow sph and has previously been applied to theoretical experimental and re

parametric study for a large cavern in jointed rock using a distinct element model udec bb parametric studies are performed using the distinct element computer program udec bb for a large cavern in the himalayas the studies provide insights into some important deformation mechanisms in a numerical system of blocks the sensitivity studies involving changes in joint spacings block size revealed that the deformations around an opening are dependent on the size or the number of blocks adjacent to the excavation large size blocks deform mainly through translational shear upon which rotational shear may occur in a model in which the block size is small compared to the tunnel dimensions the tendency to dilation across an increased number of non planar joints may contribute to interlocking of blocks the bb joint behavioural model which allows the modelling of the dilation accompanying shear and hence the build up of higher normal stresses predicts smaller deformations than the mohr coulomb model in which the dilation angle is constant the sensitivity studies involving changes in key bb joint shear strength parameters have shown that within the range of values considered the model output is relatively insensitive to assumed joint strength parameters joint roughness coefficient and r however an increase in the joint wall compressive strength contributes to an increase in the joint shear strength resulting in a marked reduction of displacements around the opening

simulating the xinmo landslide runout considering entrainment effect this paper investigates the setting causes and main dynamic characteristics of the landslide that occurred at xinmo village diexi sichuan province china on june 24 2017 by comparing the pre and post sliding dems the landslide involved the failure of 3 0 106 m3 rock mass from its source area and had a final volume of 6 3 106 m3 the landslide runout extended 2800 m horizontally and 1200 m vertically and covered an area of 143 1 104 m2 field investigation indicates that entrainment was one of the major causes of the increase in volume of landslide to reproduce the behavior of the landslide runout a depth averaged continuum model that takes entrainment into consideration is applied the simulated results generally agree well with the characteristics of the sliding path and distribution of the landslide deposit as observed in the field it is demonstrated that entrainment plays a significant role in landslide mobility and volume the final volume of the landslide is calculated about 6 21 106 m3 which has more than double its initial volume

engineering geological characterization of low strength anisotropic rocks in the himalayan region for assessment of tunnel support abstract a detailed engineering geological assessment of low strength 6 35 mpa anisotropic rocks at an ongoing hydroelectric project in the himalayan region has been carried out the project the nathpa jhakri hydroelectric project will have one of the world s largest and longest water conducting systems consisting of a 10 15 m diameter and 27 3 km long head race tunnel a 942 000 m 3 underground desilting complex and a 20 49 216 m powerhouse cavern in the area because these constructions are made in low strength metamorphosed anisotropic rocks like quartz mica schists biotite schists and muscovite schists it seemed necessary and worthwhile to undertake a comprehensive study of such rocks the studies include petrographic and petrofabric analyses of the rocks geo mechanical properties rock stress measurements rock mass classification using the q system and data concerning joint geometry joint roughness and joint strength the use of mapped geological and geotechnical data along with the experimental and modelling studies have helped to better understand the behaviour of these rocks in underground openings

assessment of dynamic impact force of debris flow in mountain torrent based on characteristics of debris flow landslides and debris flows that occur around residential areas are considered globally as significant disasters that cause damage to human life and property with terrain slope defining the flow characteristics of debris flows flow depth flow velocity and impact force vary by time and distance in particular when a structure is located in the flow path of debris flows the flow characteristics of debris flows vary by terrain slope and direction angle to simulate the flow characteristics of these debris flows the simulation results obtained by flo 2d were analyzed with six stage conditions for the research area in the analysis the flow depth flow velocity and impact force were estimated on the basis of the outlet of the research area in the presence and absence of structure s at certain distances with this the variation of the impact force in accordance with the variation of the flow depth of the debris flows was highly similar to the simulation results obtained by flo 2d when the correction index of the suggested dynamic impact force equation was 0 3 0 4 there were sections where the estimated value of the impact force was overestimated near the outlet and it was judged that the fixed values of the terrain factors width roughness coefficient slope etc caused the impact force to be overestimated however the correlation analysis showed that the correlation index was above the normal ranges in the suggested dynamic impact force equation for debris flows with the application of the terrain factors

a depth averaged two phase model for debris flows over erodible beds mass exchange between debris flow and the bed plays a vital role in debris flow dynamics here a depth averaged two phase model is proposed for debris flows over erodible beds compared to previous depth averaged two phase models the present model features a physical step forward by explicitly incorporating the mass exchange between the flow and the bed a widely used closure model in fluvial hydraulics is employed to estimate the mass exchange between the debris flow and the bed and an existing relationship for bed entrainment rate is introduced for comparison also two distinct closure models for the bed shear stresses are evaluated one uses the coulomb friction law and manning s equation to determine the solid and fluid resistances respectively while the other employs an analytically derived formula for the solid phase and the mixing length approach for the fluid phase a well balanced numerical algorithm is applied to solve the governing equations of the model the present model is first shown to reproduce average sediment concentrations in steady and uniform debris flows over saturated bed as compared to an existing formula underpinned by experimental datasets then it is demonstrated to perform rather well as compared to the full set of usgs large scale experimental debris flows over erodible beds in producing debris flow depth front location and bed deformation the effects of initial conditions on debris flow mass and momentum gain are resolved by the present model which explicitly demonstrates the roles of the wetness porosity and volume of bed sediments in affecting the flow by virtue of extended modeling cases the present model produces debris flow efficiency that as revealed by existing observations and empirical relations increases with initial volume which is enhanced by mass gain from the bed copyright 2017 john wiley sons ltd

rock structure characterization of a magnetite gneiss with foliation parallel discontinuities for footwall slope design abstract the warramboo magnetite iron ore deposit in south australia is predominantly hosted by gneiss design of the footwall slope requires an assessment of the role of foliation parallel discontinuities as planes of weakness parallel to the slope a review of published studies of joint spacing and joint persistence in gneiss shows spacing and persistence of foliation parallel discontinuities relative to non foliation parallel discontinuities varies greatly foliation parallel discontinuities form a spectrum between simply being one joint set in a blocky rock mass through to being a significant anisotropic weakness based on detailed analysis of the characteristics and frequency of foliation in drill core in the warramboo magnetite deposit it is inferred based on analysis of spacing that foliation parallel discontinuities are no more frequent or persistent than other joints therefore the rock mass is blocky rather than anisotropic and footwall slopes steeper than the foliation dip are viable

investigation of a historic and recent landslide area in ultrahelvetic sediments at the northern boundary of the alps austria by ert measurements landslides and earth flows are major dangers in alpine areas therefore determining potential landslide zones and predicting earth flow events are of great importance in these areas

quantitative analysis of debris torrent hazards for design of remedial measures debris torrents which are rapid flows of soil and organic debris down steep mountain channels are a major natural hazard in many parts of british columbia a series of recent occurrences along the

engineering geological characterization and comparison of predicted and measured deformations of a cavern in the italian alps a detailed engineering geological characterization and performance monitoring were carried out at the site of an underground powerhouse cavern in the italian alps in the area of the hydroelectric project consisting of a 4 m diameter and 10 km long diversion tunnel and a powerhouse cavern 20 m wide 39 m long and 30 m high metamorphic anisotropic rocks are present a pervasive foliation whose trend describes an open fold at the cavern site characterizes the geological structure the studies include petrographic analyses and geo mechanical properties of the rocks in situ stress measurements and rock mass classifications for the cavern site as well as the surrounding area based on field investigations two numerical models fem and dem codes were used to investigate the overall stability of the excavation and to predict the expected deformation caused by each excavation phase the measurements of actual deformations by multi base extensometer data are reasonably close to those predicted through the numerical approaches

field experiments and numerical modeling of mass entrainment in snow avalanches 1 snow entrainment alters the speed and hence the run out distance of avalanches yet little is known about this significant process we studied entrainment in snow avalanches using observations from 1 the swiss vallee de la sionne test site 2 the italian pizzac site 3 catastrophic avalanches that occurred during the winter 1998 1999 in switzerland and 4 a medium sized spontaneous avalanche that occurred in 2000 in davos switzerland we determined mass and energy balances for 18 avalanche events on average the mass increased by a factor of 4 the primary mode of entrainment appeared to be frontal ploughing although entrainment behind the avalanche front was also observed step entrainment where a snow cover layer fractures and is entirely consumed by the avalanche also occurred basal erosion was negligible mass availability and snow cover structure were the limiting factors governing entrainment other factors such as track topography and avalanche dimension played a secondary role using the experimental results we introduced an entrainment model into a saint venant type flow model where the internal shear deformation of the avalanche is governed by a bagnold law and the shear stress at the basal layer is treated as a voellmy fluid the model with entrainment not only improves the prediction of the velocities and flow heights in comparison to measurements but also reproduces the variations in run out distances which characterize avalanches with similar terminal velocities but different masses

sph run out modelling of channelised landslides of the flow type abstract rainfall induced channelised landslides of the flow type may reach high velocities and travel large run out distances the proper modelling of the propagation stage is fundamental to risk analysis and management the correct selection of mass rheology is fundamental to this procedure and the variation of pore water pressures and bed entrainment along the landslide path must also be properly taken into account all of these processes can be consistently simulated through a quasi 3d depth integrated coupled sph model in this study such a model is applied to a relevant case history from southern italy for which an advanced dataset is available the numerical results provide a satisfactory back analysis of the case history and clearly indicate that the bed entrainment rate and the extent of the erodible areas affect the propagation paths the velocities and the deposition heights on the basis of the results general insights into this type of landslide are discussed with reference to different hypotheses for propagation modelling

an improved landslide mobility model a relatively simple and versatile numerical model known as dan developed by oldrich hungr for the assessment of landslide mobility has been enhanced to incorporate the consideration of a trapezoidal shaped flow channel for more realistic modelling purposes this enhanced debris mobility model dmm has been programmed to run on a spreadsheet and has been calibrated against detailed landslide data in hong kong in contrast to previous work the enhanced dmm eliminates the limitations inherited from the assumption of a rectangular flow channel with frictionless side boundaries when using dmm no predefined width of landslide is needed the dmm simulates landslide mobility with the flow resistance on the whole wetted perimeter of the channel calculates the surface width of the landslide based on the cross sectional geometry of the channel and is capable of predicting a lobe shaped debris deposition area this technical note presents details of the enhancement to the dan formulation key words landslides

an integrated method for rapid estimation of the valley incision by debris flows abstract valley incision by debris flow is an important process in creating and maintaining the topography of a valley in addition to explaining the significant growth of the magnitudes of debris flow hazards in this paper we introduce a semi empirical method to quantitatively estimate the valley incision process by debris flows over complex bed surface we first reproduce natural bed surface across the valley by a polyline and use a hydrograph of discharge versus time to represent the temporal variation of debris flow process the presented method subsequently predicts the debris flow behavior over an irregular bed surface a dynamic erosion law considers the solved debris flow behavior and estimates an instantaneous erosion rate finally the accumulative incision depth of bed sediment is calculated reshaping the initial bed surface across the valley the presented method is simple and therefore notably beneficial for practical work the performance of the proposed method has been tested using two case study applications results demonstrate that the presented method estimates comparable incision depth as revealed in the in situ survey and the numerical simulation

2d electrical resistivity imaging of some complex landslides in lucanian apennine chain southern italy we use high resolution electrical resistivity imaging to delineate the geometry of complex landslides in the lucanian apennine chain of southern italy to identify the discontinuity between the landslide material and bedrock and to locate possible surfaces of reactivation the lucanian apennine chain is characterized by high hydrogeological hazard and shows a complete panorama of mass movements in this area all typologies of landslides markedly predisposed and tightly controlled by the geostructural characteristics are found rotational and translational slides rototranslational slides earth and mudflows as well as deep seated gravitational slope phenomena with a predominance of rototranslational slides evolving as earthflow slides three test sites characterized by complex geology and a high hydrogeologic hazard are studied the giarrossa and varco izzo earthflow slides are located to the west and east of the town of potenza whereas the latronico slide is located close to the town of latronico

assessing entrainment of bed material in a debris flow event a theoretical approach incorporating monte carlo method entrainment of underlying bed sediment by a debris flow can significantly increase the debris flow magnitude to study this phenomenon a theoretical approach to assessing bed sediment entrainment is presented the approach is based on a static approximation that bed sediment entrainment occurs when the shearing stress of the flow is sufficiently high to overcome the basal resistance of the bed sediment in order to delineate erodible zones in a channel we analyze the critical condition of this static equilibrium model and subsequently propose a new concept of a critical line to detect the entrainment reaches in a channel considering the spatial and temporal uncertainties of the input parameter the approach is further incorporated within a monte carlo method and the distribution of entrainment zones and post entrainment volumes can be analyzed this approach is illustrated by back analysis of the 2010 yohutagawa debris flow event japan results from 10 000 trials of monte carlo simulation are compared with the in situ surveys it is shown that the present approach can be satisfactorily used to delineate erodible zones and estimate possible entrainment volume of the event discussion regarding the sensitivities and limitations of the approach concludes the paper copyright 2015 john wiley sons ltd

a typical earth fissure resulting from loess collapse on the loess plateau in the weihe basin china abstract earth fissures are major geological hazards that frequently occur in the weihe basin in northwestern china and can cause severe damage to infrastructure this paper reports a case study of earth fissures resulting from loess collapse in the village of xibai in the weihe basin a series of geological investigations consisting of a site investigation trench excavation geological drilling exploratory well drilling and geotechnical testing were conducted to determine and analyze the characteristics of the xibai village earth fissures as well as the physical characteristics of the loess in the earth fissure development area the earth fissures were parallel to the village sewage pit and had a total length of 800 m with a maximum depth of 8 5 m the xibai village earth fissures were nearly vertical comparing the results of self weight collapsibility coefficient and three parameters void ratio dry density and water content of loess at different distances from the sewage pit the collapsibility of malan loess in this area and the effects of leakage from the sewage pit were determined the results revealed that a tilted seepage line was generated and the loess below this seepage line underwent varying degrees of self weight collapse deformation the nonuniform collapse settlement and rotation deformation of loess above the seepage line were thus generated while tensile stress was created in the upper part of the loess this rotation of loess similar to the deformation of the cantilever beam caused the formation of the earth fissures at the site with higher tensile stress based on the rotation mechanism this study explained the development process of collapse earth fissures and predicted that the xibai village earth fissures would continue to develop outward in the future

comparison of gpr 2d resistivity and traditional techniques for the subsurface exploration of the oschingen landslide swabian alb germany abstract numerous rotational and translational slides of different sizes cause considerable economic damage in the swabian alb sw germany and are a challenge for risk assessment the oschingen landslide is a typical example for landslides occurring along the escarpment lithology consists of jurassic sedimentary rocks involving clays overlain by marls and limestones a combination of traditional methods drilling mapping inclinometers and geophysical techniques 2d resistivity ert ground penetrating radar gpr was applied to gain knowledge about the thickness and internal structure of the landslide the drillings and penetration tests provided point information on landslide extent structure and material involved in general all inclinometers showed very little movement if at all the gpr results were affected by strong signal attenuation and by overhead reflections from the nearby woods despite these general obstacles for the application of gpr on landslides near surface sediment structures were detected in the 2d resistivity sections higher resistive limestone blocks reaching 10 15 m in thickness could be clearly distinguished from the underlying bedrock the detailed two dimensional data of the electrical resistivity tomography ert along with the rather high survey speed turned out to be the best choice to gain detailed spatial information on thickness and extent of the slope movement the measured profiles coincide with the gpr data and correspond to borehole data surprisingly all results from the applied methods clearly detected the absence of large landslide blocks in the north west of the study area this finding could not be concluded from local geomorphology of this area regarding the current landslide displacement derived from the inclinometer measurements the large landslide blocks seem to be dormant during the measured period

the effect of joint constitutive laws on the modelling of an underground excavation and comparison with in situ measurements the paper discusses the results of a numerical study which examines the influence of joint constitutive models on the response of a specific jointed rock mass mane up of an anisotropic rock slate it presents a comparison between predicted convergences and displacements of rock mass surrounding a pilot gallery and those measured during field investigations to perform this analysis the two dimensional distinct element method code udec is used and three joint laws are compared based on field investigations for site characterisation two models are constructed according to fracture density model a and model b for each of them the influence of joint constitutive law on the stability of the gallery is examined and comparisons between the investigations and predictions are made examination of the results shows that there is no noticeable change in stress magnitudes between laws the displacement magnitudes depend on 1 the constitutive law 2 the input model parameters and 3 the fracture density a parametric study in the case of model a indicates that a relatively good march between predicted and measured displacements around the gallery can be observed in certain areas

pyroclastic flow erosion and bulking processes comparing field based vs modeling results at tungurahua volcano ecuador pyroclastic density currents pdcs are high temperature and high velocity mixtures that threaten populations in the vicinity of many active volcanoes deciphering the cause of their remarkable mobility is essential for volcanic hazard analysis but remains difficult because of the complex processes occurring within the flows here we investigate the effect of bulking on dense pdc mobility by means of a double approach first we estimate the amount of material incorporated into scoria flows emplaced during the august 2006 eruption of tungurahua volcano ecuador for this we carry out a detailed analysis of 3d corrected digital images of well exposed scoria flow deposits componentry analysis indicates that pdc bulking occurs principally on the steep 25 upper slope of the volcano and the deposits typically comprise 40 50 wt of non juvenile i e accessory and accidental material secondly we develop a simple stress related grain by grain equation of erosion combined with two simple depth averaged geophysical mass flow models that compare the bulking mechanism to a non fluidized and a fluidized flow two behaviors based on coulomb and plastic rheologies are used to reproduce on a first order basis the 2006 tungurahua pdcs cross check comparisons between these modeled cases and the erosion pattern inferred from field based data allow us to evaluate the accuracy of our modeling assumptions regardless of the rheological regime the pdc induced erosion pattern of the 2006 tungurahua eruption can only be reproduced by fluctuations of the flow s basal shear stress during emplacement such variations are controlled by flow thinning thickening processes notably through the formation of a thick non erosive flow body that pushes a thin frictional erosive front during pdc emplacement the input volume of juvenile material as well as the thickness of the erodible layer available prior to the eruption are additional key parameters our work highlights complexities in pdc erosion and bulking processes that deserve further study in terms of hazard assessment our findings reveal that incorporation and bulking translate into increased flow mobility i e the augmented flow mass enhances both flow velocity and runout distance up to 20 these outcomes should be considered closely for hazard analysis at many other andesitic volcanoes worldwide where similar pdc events are common

model test on the entrainment phenomenon and energy conversion mechanism of flow like landslides abstract a reduced scale physical model test with a scale of 1 2000 is designed based on the wenjia gully landslides by changing the volume and kinetic energy of the sliding mass we find that the material grading and bed sediment thickness exert an important effect on the movement process of the landslide to investigate the dependence of the entrainment on the grade of the sliding material and bed sediment thickness a series of comparison experiments with sliding masses of different grades and loose sediment bed materials of different thickness values are conducted furthermore a high speed camera is used to record the runout process the experimental results indicate that because of the entrainment effect the erosion depth of the substrate increases when the grade of the sliding mass increases in addition different characters appear in the erosion depth volume of the accumulated area and entrainment length with the increase in bed sediment thickness furthermore the entrainment depth may increase when the bed sediment thickness increases the velocity of the sliding mass is reduced with the increase in basement thickness finally based on the analysis of landslides and the previous experimental results the energy conversion can be calculated to analyze the process of substrate entrainment for each sliding phase

routing debris flows with particle segregation a computer simulation method is developed to predict the temporal variations of debris flow discharge solids concentration and vertical mean particle size distribution a single finite step in the simulation is divided into two stages in the first stage a sediment bed composed of a well graded mixture is eroded by surface water introduced at the head of a channel thereby generating a debris flow in the second stage larger particles in the debris flow move upward because of dispersive force and are then transported forward faster than smaller particles which remain in the lower part of the flow because the velocity is slower in the lower layer another numerical simulation method is also developed to predict simultaneously the shape of the debris deposit area the distribution of the deposit thicknesses within the area and the three dimensional distribution of the mean diameters of the deposited particles both simulation methods are verified using laboratory experiments

three dimensional geophysical anatomy of an active landslide in lias group mudrocks cleveland basin uk a geoelectrical investigation of a slow moving earth slide earth flow in lower jurassic lias group rocks of the cleveland basin uk is described these mudrock slopes are particularly prone to failure and are a major source of lowland landslides in the uk but few attempts have been made to spatially or volumetrically characterise the subsurface form of these slides the primary aim of this study was to consider the efficacy of fully three dimensional geoelectrical imaging for landslide investigation with reference to a geological setting typical of lias group escarpments the approach described here included a reconnaissance survey phase using two dimensional electrical resistivity tomography ert resistivity mapping self potential sp profiling and mapping followed by a detailed investigation of an area of the landslide using three dimensional 3d ert and self potential tomography spt interpretation of the geophysical data sets was supported by surface observations aerial lidar and differential gps geomorphological surveys and intrusive investigations boreholes and auger holes the initial phase of the study revealed the existence of a strong sp signature at the site consistent with a streaming potential source and established the relationships between the main geological units the geomorphologic expression of the landslide and the resistivity of the materials in and around the study area the 3d spt model generated during the second phase of the study indicated drainage patterns across the landslide and preferential flow from the low permeability mud rocks into the underlying more permeable sandstone formation because of favourable resistivity contrasts between the clay rich whitby mudstone formation landslide material and the underlying staithes sandstone formation the volumetric 3d ert image allowed a number of surface and subsurface landslide features to be identified and spatially located these included the lateral extent of slipped material and zones of depletion and accumulation the surface of separation and the thickness of individual earth flow lobes and the dipping in situ geological boundary between the whitby mudstone and staithes sandstone bedrock formations