crack induced anisotropy in crustal rocks predicted dry and fluid saturated thomsen s parameters abstract in upper crustal conditions elastic anisotropy of rocks is mainly due to cracks as long as the anisotropy of the background matrix remains low because in general rock anisotropy remains weak in the sense that hexagonal symmetry may be sufficient to handle it thomsen suggested that a set of three parameters would be convenient to describe it using effective elasticity we derive thomsen s parameters for the case of dry and fluid saturated cracks in a rock of isotropic background in terms of crack density parameters and fluid compressibility these results can be of interest for the interpretation of seismological and seismic data they provide moreover a way to identify the fluid nature gas or liquid and to extract the crack density tensor from elastic wave data frequency effects are discussed when fluid is present so that frequency dependence can be accounted for

kinematic behaviour and velocity characteristics of a complex deep seated crystalline rockslide system in relation to its interaction with a dam reservoir abstract this paper presents the geometry kinematics and temporal deformation characteristics of a deep seated rockslide system the hochmais atemkopf situated above the gepatsch dam reservoir in northern tyrol austria results from surface and subsurface geological investigations and deformation monitoring indicate that the hochmais atemkopf rockslide system involves several sliding masses one on top of the other characterized by different velocity characteristics with displacements being greater for the shallower slide bodies during the initial impounding phases of the gepatsch reservoir uplift forces beneath the foot of the slope led to the activation of one of these shallower slide bodies moving it more than 10 m downslope in 2 years after continuous deceleration of the sliding mass the deformation rates reduced to about 2 to 4 cm per year these were found to show seasonal fluctuations that correlated with reservoir levels and drawdown conditions with induced slope accelerations peaking when reservoir levels were at their lowest this suggests in part a controlling mechanism based on seepage forces where reservoir drawdown drives the episodic rockslide deformation behaviour together the data and analyses presented demonstrate the importance of integrating detailed geology and monitoring data to derive a basic understanding of the kinematics and controlling mechanisms of a deep seated rockslide system in advance of undertaking comprehensive numerical modelling

simulating the process of reservoir impoundment induced landslide using the extended dda method abstract in this work three extensions to the traditional discontinuous deformation analysis dda method are tested to simulate the entire process describing the behavior of landslides induced by reservoir impoundment these extensions include the discretization of the area of interest block gluing and the hm hydro mechanical coupling approach several hydraulic boundary conditions are introduced based on the water level during the dry and rainfall seasons as verification the entire processes for two practical landslides the qianjiangping and the majiagou landslides which occurred in the three gorges reservoir tgr of china are simulated the simulation results agree well with the observed failure modes indicating that the proposed methodology can intuitively reproduce the entire reservoir impoundment induced landslide process

kinematics triggers and mechanism of majiagou landslide based on fbg real time monitoring reservoir landslide as one of the most serious geohazards is worldwide distributed to investigate its triggering factors and mechanisms that underlie its propagations a real time monitoring system based on fiber bragg grating fbg technology was designed for the majiagou landslide in the three gorges reservoir tgr region through analyses of inclinometer data it is found that there are two sliding surfaces existed in the majiagou landslide and that the deeper sliding surface is the critical one it accounts for nearly 80 of the deformation of the landslide this information necessitated the recording of the displacement at the deeper sliding surface together with the rainfall water level pore water pressure temperature of the landslide using a real time monitoring system after analyzing the multi parameter data in detail it is found that observed deformation is mainly governed by reservoir water levels while precipitation has some minor effects the reservoir water level is the determining factor of landslide deformation when it exceeds 160 m or lower than 150 m whereas the reservoir water level varies from 150 m to 160 m the fluctuation velocity plays a dominant role the relationship between the variation of seepage field and kinematic evolution of majiagou landslide is recognized the average displacement rate of majiagou landslide is within 0 1 mm day signifying that the landslide is still creeping presently the results are significant with respect to stability evaluation and formulation of early warning plans for the reservoir landslide

parameter inversion and deformation mechanism of sanmendong landslide in the three gorges reservoir region under the combined effect of reservoir water level fluctuation and rainfall abstract previous studies suggested that the qianjiangping landslide was caused by the combined effect of rainfall and reservoir water after the first water storage of the three gorges reservoir the sanmendong landslide with a length of 830 m an area of 2 49 105 m2 an average thickness of 22 m and a volume of 5 48 105 m3 which is located by the qinggan river a tributary of the yangtze river is only 4 km away from another famous landslide along the same river the qianjiangping landslide based on the experimental data of mechanical parameters of the landslide and displacement monitoring a nonlinear mapping relationship between mechanical parameters of the failure mass and the displacement of landslide were established by using genetic algorithms by means of uniform design numerical calculation and artificial neural networks the mechanical parameters of the failure mass are obtained by the global minimization of the deviation between the calculated displacements and the monitored displacements on this basis the deformation mechanism of the sanmendong landslide under the combined effect of rainfall and reservoir water level fluctuations was analyzed in detail the results indicated that the increase of displacement of sanmendong landslide can be primarily attributed to the combined result of reservoir water level fluctuation and rainfall

landslide deformation behavior influenced by water level fluctuations of the three gorges reservoir china abstract water level fluctuations that occurs during filling drawdown operations in man made reservoirs can result in accelerations or reactivations or even catastrophic failure of large landslides for disaster mitigation a monitoring system comprising manual and automatic gps systems borehole inclinometers and groundwater piezometers was installed to investigate the slope deformation behavior of a large reactivated landslide known as the shuping landslide at the three gorges reservoir china the long term monitoring data 2003 2015 focused on the landslide deformation which was triggered by water level fluctuations is presented in this study the cumulative displacement curves showed a step like behavior suggesting a lower base activity superimposed by phases of acceleration which appeared during reservoir drawdown periods and rainy seasons based on statistical pearson correlation analysis the increase in landslide activity is dominated by reservoir water drawdown rather than rainfall the durations of the slide acceleration phases are much shorter than the reservoir water drawdown durations based on in site piezometer monitoring data and numerical simulation the potential causes are the hydraulic processes in the slope with much smaller groundwater drawdown velocities and hydraulic gradients in the initial stage of the reservoir water drawdown period

modeling elastic anisotropy resulting from the application of triaxial stress abstractelastic wave velocities in rocks vary with stress due to the presence of discontinuities and microcracks within the rock we analytically derived a model to account for stress dependency of seismic velocities when a rock is subjected to triaxial stresses we first considered a linearly isotropic elastic medium permeated by a distribution of cracks with random orientations the geometry of cracks is not specified instead their behavior is defined by a ratio b of their normal to tangential excess compliances when this isotropic rock is subjected to triaxial stresses cracks tend to close depending on their orientation with respect to the applied stresses for small stresses the model predicts ellipsoidal anisotropy and expresses the ratios of thomsen s parameters in the three orthogonal planes of symmetry as a function of the compliance and poisson s ratios it also establishes relationships between anisotropy parameters and stress ratios deriving the model for larger stresses shows that su

poroelastic modeling of seismic boundary conditions across a fracture permeability of a fracture can affect how the fracture interacts with seismic waves to examine this effect a simple mathematical model that describes the poroelastic nature of wave fracture interaction is useful in this paper a set of boundary conditions is presented which relate wave induced particle velocity or displacement and stress including fluid pressure across a compliant fluid bearing fracture these conditions are derived by modeling a fracture as a thin porous layer with increased compliance and finite permeability assuming a small layer thickness the boundary conditions can be derived by integrating the governing equations of poroelastic wave propagation a finite jump in the stress and velocity across a fracture is expressed as a function of the stress and velocity at the boundaries further simplification for a thin fracture yields a set of characteristic parameters that control the seismic response of single fractures with a wide range of mechanical and hydraulic properties these boundary conditions have potential applications in simplifying numerical models such as finite difference and finite element methods to compute seismic wave scattering off nonplanar e g curved and intersecting fractures

seismic characterization of reservoirs with asymmetric fractures variations of reflection amplitude with offset and azimuth are sensitive to the presence of natural and induced fractures we tested inversion for fracture compliance matrix components from wide azimuth noisy synthetic pp reflection data the model was a fractured reservoir with monoclinic symmetry formed by two sets of vertical asymmetric fractures embedded in a vti background the fractures joints were assumed to be vertical with noncircular shape and or with asymmetric shear compliance results of synthetic inversion showed that an incorrect assumption about fracture shear symmetry e g treating asymmetric fractures as rotationally invariant fractures can cause considerable error in estimation of the fracture compliance matrix components of effective second and fourth rank fracture compliance matrices for a medium with monoclinic symmetry which takes into account layering and multiple fracture sets can be used as attributes related to the characteristics of the fractured medium monte carlo simulation was used to test the effect of uncertainties in the a priori information about background vti parameters of unfractured rock as they affect inversion for these attributes according to this analysis the direction of fast shear wave polarization was inverted robustly in the monte carlo simulation although the average values of the components of fracture compliance matrices obtained from monte carlo simulation were in agreement with the actual values used for forward modeling individual values obtained in monte carlo simulation were sensitive to uncertainties in the background properties in general because the elastic properties of background vti media without fractures or other azimuthally variable features do not cause azimuthal changes in reflection coefficient variation with offset simultaneous inversion for background properties and fracture tensor components require additional constraints

seismic anisotropy of fractured rock a simple method for including the effects of geologically realistic fractures on the seismic propagation through fractured rocks can be obtained by writing the effective compliance tensor of the fractured rock as the sum of the compliance tensor of the unfractured background rock and the compliance tensors for each set of parallel fractures or aligned fractures the compliance tensor of each fracture set is derivable from a second rank fracture compliance tensor for a rotationally symmetric set of fractures the fracture compliance tensor depends on only two fracture compliances one controlling fracture compliance normal the other tangential to the plane of the fractures the stiffness tensor which is more useful in the consideration of elastic wave propagation through rocks can then be obtained by inversion the components of the excess fracture compliance tensor represent the maximum amount of information that can be obtained from seismic data if the background rock is isotropic and the normal a

towards a complete understanding of the triggering mechanism of a large reactivated landslide in the three gorges reservoir abstract the primary aim of this study is to research the characteristics of a slide motion and its relationships with environmental triggers with reference to the quchi landslide which is a large slow moving reactivated landslide in the three gorges reservoir region since 2006 this instability has been involved in a slow moving process with clearly visible signs ground fissures cracking of houses and road the landslide consists of 18 mm3 rock masses threatening quchi town and a road that is crucial for local transportation for civil protection purposes a continuous monitoring system has been put into use since 2009 combining four years of meteorological and hydrological data with gps displacement measurements and in situ observations allows a detailed identification of the key processes involved the deformation is thought to be closely related to precipitations and fluctuating reservoir levels slope movements have a highly distinctive pattern that is characterized by high deformation starting in june and lasting into september when the reservoir level drops and rainfall increases followed by a rapid transition to constant deformation until the next wet season in order to investigate in detail the influences of rainfall and fluctuating water levels on the hydromechanical behavior of the landslide a series of two dimensional numerical simulations are performed using the universal distinct element code udec the modeling reveals that precipitation mainly mobilizes the slope materials on the upper part of the slope while the other trigger factor fluctuating water levels destabilizes the foot of the slope into a multistage failure with a remarkable retrogressive evolution the slide is most likely to collapse in a complex pattern characterized by en masse sliding on the upper part of the slope and a retrogressive rupture at its foot

numerical simulation of qiaotou landslide deformation caused by drawdown of the three gorges reservoir china landslides located beside reservoirs tend to be unstable or are characterized by large deformation during the drawdown process this has been accepted by many experts in this paper we use qiaotou landslide which is located beside the three gorges reservoir tgr as a typical case study to investigate and predict the deformation mechanism during the drawdown process of tgr in detail according to field investigation the landslide mass is mainly composed of thick loose silt and clay mixed with fragments of rock bedrock is mainly composed of silty sandstone field and laboratory tests indicate that the landslide mass has a high permeability coefficient if the water level declines fast intense seepage force may result based on these data we establish a three dimensional geological model of qiaotou landslide by flac3d and perform a numerical simulation using the saturated unsaturated fluid solid coupling theory for the simulation we assume that the drawdown from 175 to 145 m takes place with a speed of 25 cm day which is based on the extreme water level regulation program of tgr the simulation shows that this causes a significant deformation in the landslide mass and that the maximum displacement within the landslide is 24 2 cm during the drawdown process the maximum displacement zone is shifting from the upper part of the landslide where bedrock surface is steeper and thickness of loose deposits is less to the middle part of the landslide where bedrock surface is less steep and thickness of loose deposits is higher the deformation mechanism indicates that in the early stage of the drawdown the deformation of the landslide mass is mainly caused by seepage and in the later stage mainly by consolidation

seismoacoustic signatures of fracture connectivity wave induced fluid flow wiff between fractures and the embedding matrix as well as within connected fractures tends to produce significant seismic attenuation and velocity dispersion while wiff between fractures and matrix is well understood the corresponding effects related to fracture connectivity and the characteristics of the energy dissipation due to flow within fractures are largely unexplored in this work we use oscillatory relaxation simulations based on the quasi static poroelastic equations to study these phenomena we first consider synthetic rock samples containing connected and unconnected fractures and compute the corresponding attenuation and phase velocity we also determine the relative fluid displacement and pressure fields in order to gain insight into the physical processes involved in the two manifestations of wiff in fractured media to quantify the contributions of the two wiff mechanisms to the total seismic attenuation we compute the spatial distribution of the local energy dissipation finally we perform an exhaustive sensitivity analysis to study the role played by different characteristics of fracture networks on the seismic signatures we show that in the presence of connected fractures both p wave attenuation and phase velocity are sensitive to some key characteristics of the probed medium notably to the lengths permeabilities and intersection angles of the fractures as well as to the overall degree of connectivity of the fracture network this in turn indicates that a deeper understanding of these two manifestations of wiff in fractured media may eventually allow for the extraction of some of these properties from seismic data

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

a thermomechanical model for saturated clays a thermomechanical model for saturated clays is proposed within the framework of recent extensions of the cam clay model the results of some tests found in the literature are analyzed and the main features of the thermomechanical behaviour of clays are identified the effect of the overconsolidation ratio ocr on the volume change of a soil expansion contraction submitted to heating is well established using experimental data obtained for selected soils by various authors however existing models need to be modified to correctly model this feature for this reason a new volumetric thermal plastic mechanism is developed that allows for the prediction of plastic strains at higher ocr values the overconsolidation effect observed when heating a normally consolidated soil is also modelled particular attention is paid to the coupling and hardening phenomena related to the combined effects of stress and temperature a qualitative validation is made by examining the response of the model under a given th

simple model for downstream variation of median sediment size in chilean rivers a simple theory is developed to account for the observed downstream variation of the median sediment size in chilean rivers based on a reach wise equilibrium sediment transport concept the theory makes use of a bedload transport equation linked with a resistance equation to estimate the median sediment diameter as a function of channel slope with the flow reynolds number and bedload concentration as parameters both meyer peter and muller s and ackers and white s formulas are used alternatively as bedload equations a manning strickler type of formulation is used as a resistance relationship the resulting model is validated against field data corresponding to 150 rivers in central chile covering slopes in the range of 0 04 8 61 with median sediment size in the range of 0 3 250 mm despite the simplicity of the present theory and the somewhat bold assumptions made in its derivation the estimated variation of the median sediment size with channel slope follows the same trend as the field data most of the scatter of these data falls within the theoretical limits given by the estimated range of values of the parameters of the model

in situ monitoring platform and preliminary analysis of monitoring data of majiagou landslide with stabilizing piles abstract reservoir landslide evolution is a complex multi fields dynamic process which involves the interaction of the seepage field stress field displacement field and temperature field after installing the stabilizing structure into landslide the landslide and stabilizing structure will establish the landslide stabilization system and lead to a more complex multi fields evolution process under the reservoir operation to study this complex problem this paper designs and establishes a comprehensive in situ multi fields information monitoring platform which has been installed on majiagou landslide in three gorges reservoir area the multi fields information monitoring platform has four components the landslide stabilization system the in situ multi field monitoring system the data transmission and receiving system and the database management system the landslide stabilization system includes majiagou landslide and two experimental reinforced concrete piles the in situ monitoring system consists of landslide surface deformation monitoring system experimental piles monitoring system and boreholes monitoring system the landslide surface deformation monitoring system includes gps stations and fiber lines the experimental pile monitoring system consists of earth pressure cells around piles stress and strain gauges on steel bars and strain and temperature fiber sensors in piles the borehole monitoring system includes boreholes with inclinometers water pressure and water level gauges fiber sensors therefore the in situ monitoring system can monitor the seepage stress displacement and temperature fields in the landslide as well as the force and deformation in the experimental piles currently the data transmission and management system is under construction and will be finished soon current monitoring results show that the landslide moves along three slip surfaces and the deformation of the experimental piles is influenced by reservoir operation this platform can provide multi fields data for scholars to study the evolution of landslide stabilization system

effects of fracture intersections on seismic dispersion theoretical predictions versus numerical simulations abstract the detection and characterisation of domains of intersecting fractures are important goals in several disciplines of current interest including exploration and production of unconventional reservoirs nuclear waste storage co2 sequestration and groundwater hydrology among others the objective of this study is to propose a theoretical framework for quantifying the effects of fracture intersections on the frequency dependent elastic properties of fluid saturated porous and fractured rocks three characteristic frequency regimes for fluid pressure communication are identified in the low frequency limit fractures are in full pressure communication with the embedding porous matrix and with other fractures conversely in the high frequency limit fractures are hydraulically isolated from the matrix and from other fractures at intermediate frequencies fractures are hydraulically isolated from the matrix porosity but can be in hydraulic communication with each other depending on whether fracture sets are intersecting for each frequency regime the effective stiffness coefficients are derived using the linear slip theory and anisotropic gassmann equations explicit mathematical expressions for the two characteristic frequencies that separate the three frequency regimes are also determined theoretical predictions are then applied to two synthetic 2d samples each containing two orthogonal fracture sets one with and another without intersections the resulting stiffness coefficients thomsen style anisotropy parameters and the transition frequencies show good agreement with corresponding numerical simulations the theoretical results are applicable not only to 2d but also to 3d fracture systems and are amenable to being employed in inversion schemes designed to characterise fracture systems

do seismic waves sense fracture connectivity 1 a defining characteristic of fractured rocks is their very high level of seismic attenuation which so far has been assumed to be mainly due to wave induced fluid flow wiff between the fractures and the pore space of the embedding matrix using oscillatory compressibility simulations based on the quasi static poroelastic equations we show that another important and as of yet undocumented manifestation of wiff is at play in the presence of fracture connectivity this additional energy loss is predominantly due to fluid flow within the connected fractures and is sensitive to their lengths permeabilities and intersection angles correspondingly it contains key information on the governing hydraulic properties of fractured rock masses and hence should be accounted for whenever realistic seismic models of such media are needed

analysis of baishuihe landslide influenced by the effects of reservoir water and rainfall since the impoundment of the three gorges reservoir in june 2003 a number of new landslides have occurred and existing landslides have been made worse the 1 260 104 m3 baishuihe landslide located at 56 km west of the three gorges dam began to deform more noticeably after the first impoundment in early july 2003 the sliding of the two blocks comprising the landslide one an active block and the other a relatively stable block became apparent after approximately 5 years of monitoring field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir these effects have been investigated in the present paper including the deformation characteristics movement pattern direction displacement and velocity earmarking the temporal evolution of the active block based on a practical creep model of a large rock slide alert velocity thresholds for pre alert alert and emergency phases have been computed corresponding to the imminence of failure the alert velocity thresholds are being proposed to be included as a part of an early warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure the emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the three gorges reservoir in the near future

distributed acquisition characterization and process analysis of multi field information in slopes the slope is a multiphase composite system including solid liquid and gas phases slope stability changes under the actions of stress temperature and seepage slopes will be very prone to landslide if in an unstable state in this paper considering the contributions of different fields to the landslide the distributed acquisition characterization and stability analysis of multi field information from slopes was studied systematically using distributed fiber optic sensing dfos technology a sensing system based on dfos was designed and developed for multi field information monitoring including stress temperature seepage and deformation the corresponding methods for data processing identification and methods for characterization description are also proposed on this basis the evolution of the slope is analyzed finally monitoring results of the dfos system from the majiagou landslide are shown as a case study for verification

effective elasticity of rocks with closely spaced and intersecting cracks the noninteraction approximation nia is the simplest effective media theory that describes the overall elasticity of fractured rocks if the nia is used for fracture characterization its accuracy and the range of applicability must be estimated we do it by performing a series of 3d finite element simulations of effective elasticity for models that contain several sets of fractures embedded in otherwise isotropic host rock we intentionally place the cracks close to each other to create strong interactions in their local stress fields in addition we allow the cracks to intersect in such a way that they do not break a rock specimen apart perhaps surprisingly we find that fracture interactions and intersections have little influence on the effective elasticity and the nia performs well in all cases while it has a tendency to slightly underestimate the effective stiffnesses the incurred errors are small their typical magnitudes are just a few percent in the entire range of the crack densities expe

on attenuation of seismic waves associated with flow in fractures heterogeneity of porous media induces a number of fluid flow mechanisms causing attenuation of seismic waves attenuation induced by squirt type mechanisms has previously been analyzed for aspect ratios smaller or equal to 10 3 using a hybrid dimensional modeling approach particularly apt for large aspect ratio conduits we numerically simulated deformation induced fluid flow along two intersecting fractures to investigate the physics of attenuation related to the interaction of fracture induced fluid flow and to leak off attenuation related to fracture flow increases in magnitude with increasing geometrical aspect ratio of the fracture the inherent time scales of both flow mechanisms do not influence each other but the faster process is associated with stronger attenuation than the slower process models relying on simple diffusion equations have rather limited potential for approximation of pressure transients