physical simulation of ground fissures triggered by underground fault activity abstract numerical modeling and physical simulation experiment are two important steps to investigate the stress and strain fields of overlying strata but sometimes it is very difficult to do the test of the physical experiment on a large scale soil sample due to the financial consideration and the available test site to investigate the features of the ground fissures prevailing in xi an city we undertook in this study a series of physical simulation tests on the large scale soil sample to analyze the stress and displacement fields caused by the underlying normal fault activity comparing with the fracturing modes of the ground fissures and the failure patterns of construction building it is evident that the experiment results coincide with the failure patterns of the building but not with the fracturing modes of the ground fissures which indicate that the ground fissures in xi an may be an old fracture surface having already spread to superficial layer covered by a very thin layer of loose soils and the groundwater over pumping is just a factor to make them exposed on the ground surface

dislocation model for radon response to distant earthquakes if radon changes associated with earthquakes are caused by changes in strain within the earth reports of radon signals that are measured at considerable distances from the hypocenters of earthquakes can be understood a simple dislocation model leads to estimates of distances that increase to hundreds of kilometers at earthquake magnitudes of 5 and above the essential components of the theory are that the strain from a dislocation loop varies at large distances x as x 3 while the strains increase with the magnitude of the earthquake represented a threshold sensitivity is inferred from radon measurements associated with earthquakes near blue mountain lake new york the usefulness of a global 222rn monitoring network is inferred

geometrical appearance and spatial arrangement of structural blocks of the malan loess in nw china implications for the formation of loess columns abstract loess as one of the main quaternary deposits covers approximately 6 of the land surface of the earth although loess is loose and fragile loess columns are popular and they can stand stably for hundreds of years thereby forming a spectacular landform the formation of such special column shaped soil structures is puzzling and the underlying fundamentals remain unclear the present study focuses on quantifying and examining the geometrical shape and spatial alignment of structural blocks of the malan loess at different locations in the loess plateau of china the structural blocks under investigation include clay and silt sized particles aggregates fragments lumps and columns which vary in size from microns to tens of meters regardless of their size the structural blocks of the malan loess are found to be similar in shape i e elongated with a length to width ratio of approximately 2 6 the aggregates fragments lumps columns and macropores between aggregates exhibit strong concentration in the vertical or subvertical alignment these phenomena imply that the malan loess is anisotropic and it is composed of a combination of vertically aligned strong units and vertically aligned weak segments based on this vertiloess structure is proposed to denote this combination the vertiloess structure prevents horizontal erosion but favors spalling peeling toppling falling and cracking sliding of vertical loess pieces thereby forming loess columns

hydroconsolidation and subsidence of loess studies from china russia north america and europe abstract various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested these include considerations of rheology thermodynamics phase movements particle packing interparticle bonding pore structure and distribution catastrophe theory topology and simple structural frameworks chinese north american and most european investigators tend to concentrate on mechanisms of loess collapse the russian literature however retains an extra dimension two approaches the syngenetic and the epigenetic approach to the formation of subsiding loess have been defined in the literature most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition some russian writers in contrast promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material which can then suffer from hydroconsolidation and subsidence the basis of the phenomenon is a change in the packing structure of the major loess particles and this can be modelled using simple monte carlo methods to develop appropriate structures this paper aims to review the work done on this important subject serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen forties fifty years ago and this has been reported in a piecemeal manner a detailed critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the united kingdom an attempt is made to describe the process in a phenomenological and a structural sense inherent in this the role of n ya denisov as subsidence pioneer is considered

constraining the age of the last geomagnetic reversal from geochemical and magnetic analyses of atlantic indian and pacific ocean sediments we studied four marine sediment records of the matuyama brunhes geomagnetic reversal from four sites located in the indian atlantic and western pacific oceans the results combine paleomagnetic cosmogenic nuclide beryllium be 10 and oxygen isotope analyses that were performed on the same samples in order to avoid any stratigraphic bias the three records from the equatorial indian ocean and north atlantic ocean did not reveal any offset between the authigenic be 10 be 9 ratio be ratio peak and the interval of low relative paleointensity rpi that characterizes the reversal the lower and upper limits of transitional directions are also concomitant with the increased atmospheric be 10 production that accompanied the geomagnetic dipole intensity decrease in contrast the record from western equatorial pacific ocean sediments was found 18 cm below the be ratio changes as a result of late magnetization acquisition at all four sites maximum be 10 production occurred at the same period soon after the maximum of marine isotope stage 19 mis 19 and therefore indicates its synchronous worldwide character such features are effectively observed from the be ratio signals and their relationship with the magnetic transition interval which further confirms the synchronous character of the transition taking all dating uncertainties 1 6 ka between sites and 5 ka for the age model into consideration our records suggest a mean reversal age of 772 4 6 6 ka the age of the transition in the atlantic ocean record is closer to 774 ka but this difference is within the limit of significance

a review of shear and tensile strengths of the malan loess in china abstract loess deposits cover about 640 000 km 2 of china equivalent to about 6 7 of the total area of the country the loess plateau alone covers approximately 317 000 km 2 making it the largest bulk accumulation of loess on the earth land instability hazards in the loess plateau are frequent and varied among which the cracking sliding beng hua in chinese failure is a typical mode cracking sliding failures commonly occur in the malan loess at volumes of the order of 100 m 3 and cause more than 100 deaths per year as the tension in the upper part of the failure plane and shearing sliding along the lower part mobilize cracking sliding failures this failure mode demands an investigation into the tensile and shear strengths this paper presents a review of these properties based on a large collection of literature both tensile and shear strengths of the malan loess decrease with water content and increase with dry density resulting in close multi regression correlations large differences between undisturbed and disturbed tensile strengths of the loess indicate the significance of its structure shear strength of the loess is direction dependent indicating strong anisotropy of the loess structure test method sample size and loading rate all influence the measured tensile strength

distribution and mechanism of the ground fissures in wei river basin the origin of the silk road wei river basin wrb is the origin of the ancient and new silk road and it is located in southern fen wei graben system china since 1950s hundreds of ground fissures have formed in this affluent basin and these ground fissures have become the main geohazard in wrb this paper used a series of geological investigations such as site investigation trench excavation geological drilling and geophysical survey to understand the distribution and mechanism of formation of the ground fissures in wrb the results are 1 212 ground fissures in wrb were located in xi an xianyang weinan city and they have clear orientations mainly distributed from nee to sww nw to se and e to w moreover the ground fissures are accompanied by active faults along the same directions 2 ground fissures in wrb can be divided into two types some ground fissures display obvious horizontal and vertical separations on the earth surface whereas others only display obvious horizontal separations on the earth surface 3 ground fissures in wrb are triggered by four factors viz basin structure active fault human activities and loess erosion 4 the mechanism for the formation of ground fissures has also been proposed tectonic faulting is the fundamental cause of ground fissures in the wei river basin and imbalances in the man land caused by human actives accelerated the ground fissures activities 5 many effective measures have also been proposed to mitigate the hazards of ground fissures in wrb such as planning engineering measures controlling the exploitation of groundwater and monitoring this research will be helpful in safeguarding the sustainable development of the silk road economic belt

calcrete and near surface geology of kuwait city and suburbs kuwait arabian gulf abstract near surface accumulation of pedogenic carbonate calcrete is a common and characteristic feature of the landscape of kuwait city and its suburbs the principal host material for these calcretes is a thick sequence of unconsolidated quartzose sand a typical fully developed soil profile can be divided into five zones in descending order these are 1 a top calcareous aeolian soil 2 a zone of friable sand with powdery or tightly cemented calcrete lumps nodules 3 a massive calcrete zone 4 a mottled calcrete zone and 5 unaltered parent material episodic formation of calcrete is indicated by the occurrence of multiple profiles in which zones are repeated calcrete ooids and pseudo ooids of accretionary origin are characteristic of the upper calcrete zone the carbonate fraction in the upper calcrete zone consists dominantly of low mg calcite with minor amounts of dolomite replacement was a major process in formation of the massive calcrete and the dominant cementing material is largely low mg calcite and or microcrystalline dolomite aeolian dust is considered to be the major source of ions for calcrete formation in kuwait city and suburbs an earlier introduced model is applied to explain the mechanisms of formation and precipitation of low mg calcite and dolomite the calcrete thickness in the study area is explained by episodic deposition of fluviatile sand and calcrete formation during the oligocene through lower miocene period

an overview of the surface and near surface geology geomorphology and natural resources of kuwait abstract the surface and near surface geology geomorphology and natural resources of kuwait have been reviewed based on the published work the stratigraphy and structure of the near surface sediments of kuwait have been mainly controlled by the tertiary tectonic activity of the arabian shield the shield started separating from the african mainland by the close of the eocene and drifted northeastward towards the asian plate giving rise to the folding and thrusting of the zagros mountains of iran the tectonic activity superimposed a northwest southeast trend over an earlier north south structural trend and gave rise to parallel ridges and valleys trending northwest southeast through differential erosion it has been possible to identify 15 geomorphic zones and 11 morphostructures from analysis of the surface features of kuwait seven of these morphostructures can be attributed to tectonic processes and two to fluvial processes it has not been possible however to explain satisfactorily the origin of the jal az zor escarpment or the ad dalmaniyah cliff the whole of kuwait can be divided into seven drainage zones of these the internal drainage systems of the ar raudhatain umm al aish drainage system and the ad dibdibba drainage system are hydrogeologically most important the clastic deposits of kuwait group sediments often affected by low temperature carbonate calcite and dolomite and sulfate gypsum precipitation form the surface rock of kuwait these are covered by recent aeolian and residual deposits playa deposits in the enclosed basins and near the coast oolitic sediments beach sands and sabkha deposits the surface and near surface deposits of kuwait contain important reserves of construction sand and gravel as well as the only naturally occurring freshwater reserves of the country an understanding of the nature of these surface deposits is required for the management of environmental issues like sand encroachment land use planning and soil and groundwater pollution

evolution and origin of the ground fissures in xian china large scale extraction of ground water in xian has resulted in significant drawdown of the phreatic surface and in land subsidence across this ancient capital of china it has also triggered the rejuvenation of the normal faults in the upper portions of the quaternary deposits underlying the city leading to surface rupturing and the development of ground fissure zones across the city these ground fissure zones are structurally controlled in the sense that they are directly linked to the normal faults in the quaternary deposits all trending in an east northeasterly direction in essence they are the surface expressions of the deeper faults under current drawdown conditions the ground fissures have resulted in extensive property damage along their paths of propagation this paper describes their occurrence their possible causative mechanism and the resultant damage of necessity xian will still be dependent on ground water supply to a large extent in the years ahead however ground water extraction will have to be managed in an environmentally sustainable manner in order to minimize the geological hazards associated with the ground fissures

characterization of macropore structure of malan loess in nw china based on 3d pipe models constructed by using computed tomography technology abstract malan loess is a grayish yellow or brownish yellow clastic highly porous and brittle late quaternary sediment formed by the accumulation of windblown dust the present day pore structure of malan loess is crucial for understanding the loessification process in history loess strengths and mechanical behavior this study employed a modern computed tomography ct device to scan malan loess samples which were obtained from the east part of the loess plateau of china a sophisticated and efficient workflow for processing the ct images and constructing 3d pore models was established by selecting and programming relevant mathematical algorithms in matlab such as the maximum entropy method medial axis method and node recognition algorithm individual pipes within the malan loess were identified and constructed by partitioning and recombining links in the 3d pore model the macropore structure of malan loess was then depicted using quantitative parameters the parameters derived from 2d images of ct scanning included equivalent radius length and aspect ratio of pores porosity and pore distribution entropy whereas those derived from the constructed 3d structure models included porosity coordination number node density pipe radius length length density dip angle and dip direction the analysis of these parameters revealed that malan loess is a strongly anisotropic geomaterial with a dense and complex network of pores and pipes the pores discovered on horizontal images perpendicular to the vertical direction were round and relatively uniform in shape and size and evenly distributed whereas the pores discovered on vertical images varied in shape and size and were distributed in clusters the pores showed good connectivity in vertical direction and formed vertically aligned pipes but displayed weak connectivity in horizontal directions the pipes in vertical direction were thick long and straight compared with those in horizontal directions these results were in good agreement with both numerical simulation and laboratory permeability tests which indicate that malan loess is more permeable in the vertical direction than in the horizontal directions

earth fissures developed within collapsible loess area caused by groundwater uplift in weihe watershed northwestern china abstract earth fissures are geological hazards that frequently occur all over the world and greatly threaten the safety of people s property and lives this paper reports a case from a typical agricultural town in the weihe watershed northwest nw of china dali which has been severely affected from earth fissures in recent years a comprehensive survey was made on the geometric characteristics of the earth fissures developed in the study area through field investigations trial trenches boreholes exploratory wells and laboratory tests the study indicates that fourteen nearly parallel fissures have developed in the area with a fissure to fissure space of 140 350 m and a maximum length of any of the given fissures of 500 m the underlying faults loess joints and the quaternary unconsolidated and collapsible sedimentary loess provide a favorable geological condition for the occurrence of the earth fissures from 2003 to 2012 the groundwater level in the area rose about three meters due to agricultural irrigation and leakage of a water diversion canal collapsible deformation occurred in the loess while seepage erosion expanded the original joints in the soil the earth fissures occurred resulting from multiple geological environmental forces and human activities

stability of loess abstract lutenegger a j and hallberg g r 1988 stability of loess eng geol 25 247 261 the natural stability of loess soils can be related to fundamental geotechnical properties such as atterberg limits water content and void ratio field observations of unstable conditions in loess deposits in the upper midwest u s a show relationships between instability and the in situ moisture content and the liquidity index of the loess unstable loess can attain natural moisture contents equal to or greater than its liquid limit implications of these observations for applied engineering works are described

distribution and generative mechanisms of ground fissures in china abstract in this study 5002 ground fissures in more than 1500 localities across 22 provinces in china are investigated and mapped to reveal their spatial distribution the distribution of these ground fissures in china exhibits six regular patterns assemblages in north china syngenesis in extensional basins clustering along fault zones distributing along geomorphic boundaries developed on the edge of subsidence areas and clustering in large and medium sized cities combined with regional gps numerical simulations physical model test and in sar monitoring the generative processes of ground fissures are analyzed and discussed in relationship to four mechanisms 1 deep dynamic tectonism controls on the location of ground fissures 2 intracontinental dynamic tectonism resulting in ground fissure assemblages 3 fault stress inducing formation of ground fissures and 4 groundwater overmining resulting in the reactivation and expansion of ground fissures the geological environment is thus responsible for the establishment and appearance of ground fissure more importantly ground fissure propagation in china is the result of the synergistic effects of internal geological dynamic including in deep tectonism intracontinental tectoniim and fault movement coupled with anthropomorphic stress this genetic model can be summarized as one that is tectonically controlled stress driven and affected by regional hydrodynamic

geochemical characterization of the luochuan loess paleosol sequence china and paleoclimatic implications abstract chemical major and trace element and isotopic sr nd analyses of the luochuan loess paleosol sequence in china were performed in order to examine the following problems 1 potential source heterogeneity 2 element behavior during pedogenesis 3 paleoclimatic implications and 4 the use of loess data to determine the average composition of the upper continental crust new results clearly indicate that rb sr u and ce abundances are severely depleted in paleosols relative to their parental loess the behavior of these elements is strongly controlled by the breakdown of primary minerals such as carbonate sr or by alteration processes in highly oxidizing environments ce and u the pattern of element variations through the upper section of the luochuan sequence mimics the magnetic susceptibility signal both in position and in intensity thus reinforcing the pedogenesic origin of the enhanced magnetic susceptibility in paleosols all loess samples display highly uniform ree patterns except for ce characterized by the upper continental crust ucc ratios la yb n 10 and eu eu 0 66 the paleosol ree patterns are similar to those of the loess with the same lree hree fractionation but they also show distinct and variable negative ce anomalies nd and sr isotopic compositions are rather uniform in both loess and paleosols and do not vary with stratigraphic position nd 10 5 to 9 2 87 sr 86 sr 0 715 to 0 719 the isotopic homogeneity in the luochuan sequence strongly suggests a uniform source region during the entire period of deposition since 800 ka ago to the present several conclusions may be drawn from the present study 1 1 no geochemical distinction can be made between loess layers l1 to l7 the sources and the dust storm trajectories must have been essendally the same for the last 800 ka 2 2 some elements e g ca rb sr u ce are strongly fractionated by pedogenesis between loess and paleosols ce mobility in soils is clearly demonstrated but the process responsible for this leaching is still poorly understood 3 3 systematic variations of element abundances and ratios between loess and paleosols can be used as chemical indicators for pedogenesic intensity and so for paleoclimatic change these chemical indicators serve a function similar to that of oxygen isotopes in deep sea sediments pelagic foraminifera or that of magnetic susceptibility in loess sequences they are different recorders of paleoclimatic change 4 4 the striking uniformity of ree patterns and la th ratios in the luochuan loess and paleosols as well as in loess worldwide is an excellent starting point for estimating the average composition of the upper continental crust

origin and depositional model of wadi al batin and its associated alluvial fan saudi arabia and kuwait abstract wadi al batin alluvial fan which extends northeastward from hafar al batin in saudi arabia to cover parts of kuwait and southwestern iraq represents the largest of several other non active fans in central and south arabia evidence put forward suggests that like other comparable deposits of varying age in the arabian peninsula the al batin fan was deposited following downdip breaching of a scarp barrier by a large paleoriver further to the west which once flowed southward down the full length of the arabian peninsula the downdip breaching model offers an explanation of how the dibdibba gravels were introduced into kuwait it is postulated that the present southeasterly course of tigris euphrates rivers to the head of the arabian gulf was the last of the easterly diversions of the lower courses of the southward flowing paleoriver as its southern end shifted progressively by a sequence of lateral breaches through the central arabian scarplands it is the postulated existence of this huge former drainage system which is seen as the fundamental explanation for the occurrence of the dibdibba formation in kuwait and comparable gravels elsewhere on the eastern flank of the arabian peninsula after the initial phases of deposition of al batin alluvial fan its surface was dissected by floods from a reduced catchment area no longer carrying the same sediment load and therefore capable of eroding the fan dissection of the fan surface continued until the present wadi ai batin became sufficiently incised into the underlying tertiary bedrock to serve as a permanent outlet this led to the transport and secondary concentration of post dissection gravels along the perimeter of the ancient fan

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

differential compaction mechanism for earth fissures near casa grande arizona precise gravity measurements indicate that earth fissures or tension cracks caused by ground water withdrawal within a 10 km 2 area southeast of casa grande arizona are associated with relief on the buried interface between the alluvial aquifer and underlying bedrock all of the fissure zones which have a cumulative length of 8 7 km occur above either ridges or steps in the bedrock surface intersecting fissure zones overlie intersecting bedrock features and the angle of intersection of the zones accurately reflects the angle between the bedrock features these relations suggest that the fissures are forming in response to localized differential compaction caused by localized variations of aquifer system thickness topographic profiles across fissures on undisturbed desert floor confirm differential compaction proportional to the variations in aquifer thickness the occurrence of the fissures at points of maximum convex upward curvature in profiles of both the topographic and buried bedrock surfaces indicates that the fissures result from tensile strains caused by bending of the strata above the buried bedrock features in response to the differential compaction tensile strains at failure are estimated to range from 0 02 to 0 2 on the basis of modeling of the bending process

ground cracks in ethiopian rift valley facts and uncertainties abstract no accurate relationship has been obtained in this study between ground cracks in ethiopian rift valley and the most common causes of earth fissures such as aquifer system compaction and increased horizontal seepage stresses this is due to the fact that the level of groundwater withdrawal responsible for these processes is still negligible in ethiopia if aquifer system compaction and increased horizontal seepage stresses have a certain role then it should be through the long term effect of groundwater flow from basins to neighboring lakes the ground cracks appeared also not to have a direct link with active faulting or distant earthquakes structurally the ethiopian rift valley is dominated by ne sw trending tensional faults but no evidence is obtained in this study to associate the process of surface cracking with major tectonics however an aseismic elastic strain which originates at depth and propagates upward through sediments without the formation of bedrock faults could result in conditions conducive to the development of cracks then fissures might ultimately be created after heavy rainfalls by near surface processes such as piping and hydrocompaction along water line sources

aeolian processes and sand encroachment problems in kuwait abstract the surface of kuwait is carved in a calcretized clastic sequence of miocene pleistocene age mostly covered by a thin blanket of recent aeolian deposits fast rate of development and increase of human activities contributed to denudation of the vegetative cover and exposure of dry loose sediments to wind action at present kuwait is intensively subjected to aeolian actions manifested by frequent occurrences of sand and dust storms this dictated the need for regional understanding of the magnitude of the aeolian processes their behavior with man made establishments and their long and short term impacts a comparison between the nature and distribution of recent surface sediments in kuwait in 1979 and 1990 shows significant changes that reflect the work of aeolian processes during this period the direct impact of the enhancement of aeolian action is represented by the increase in the rate of sediment transport transportation of fine grained particles in suspension frequently occurs during dust storms usually initiated in southern iraq the particles migrate over kuwait as thick dust clouds and finally settle in the northern part of the arabian gulf bedload transport of sand or saltation frequently occurs during summer whenever wind speed reaches 5 4 m s the average annual sand drift rate in kuwait is about 20 m 3 m width 1 yr 1 the majority of the drift occurring during the period may august to the southeast bedform transport or sand dune movement is also recognized in kuwait sand dunes mostly occur as small barchans of about 3 m height the measured rate of movement of these barchans varies with height a barchan of average height usually moves about 20 m in nine monthes january august the remarkable high rate of sand transport and the increase in development activities in the desert areas are responsible for the enhancement of the sand encroachment problems in kuwait almost all installations roads and farms are significantly affected by the accumulation of considerable amounts of aeolian sand these problems have pronounced adverse environmental and economic impacts

analysis and comparison of two types of ground fissures in dali county in the weihe basin china dali county is located in the eastern weihe basin where frequent ground fissure disasters occur dali ground fissures are macroscopically part of the ground fissure group in the weihe basin and have caused serious damage to infrastructure and agricultural production in this area in this paper 25 ground fissures in dali county are identified through investigation and two typical ground fissures in fengcun and weizhuang are selected for research through field investigation trench excavation geophysical exploration soil water content tests and collapsibility coefficient tests the basic features shallow structural characteristics deep structural characteristics and genetic mechanisms of the two ground fissures are revealed the strike of the fengcun ground fissure is 45 almost parallel to the shuangquan linyi fault the length is 2 km and the profile is ladder like and extends deep with synsedimentary characteristics the weizhuang ground fissures are circular in plan view with a length of 315 m and trumpet shaped in profile they disappear in the paleosol layer the mechanism of the fengcun ground fissure is related to basin extension and fault activity the ground fissures are the surface reflections of deep faults the mechanism of the weizhuang ground fissures is related to loess collapsibility and seepage the malan loess has differential settlement in collapsible and noncollapsible areas and ground fissures are the boundary line for differential settlement of loess finally based on the genetic mechanisms of ground fissures dali ground fissures can be divided into two types tectonic and nontectonic

weak tensile characteristics of loess in china an important reason for ground fissures by means of uniaxial tensile tests we analyzed the tensile characteristics of undisturbed and disturbed loess samples taken from the areas where ground fissures are prevalent the study shows that the tensile strength and ultimate tensile strain of loess are very small no more than 25 kpa and 0 5 respectively water content and dry density are the two important factors for the tensile strength of loess and show a decreasing exponential and increasing exponential relationship with the tensile strength respectively from the results of tensile tests on loess and the mechanism of ground fissure development in loess areas we may draw a conclusion that the weak tensile strength the loose structure and the collapsibility are the important contributing factors to the development of ground fissures in china s loess areas

kuwaiti dolocrete petrology geochemistry and groundwater origin abstract near surface sediments in southern kuwait show extensive development of duricrusts the host materials are siliciclastic sandstones of the post eocene kuwait group inland the duricrusts are dominantly pedogenic calcrete with some silcrete and gypcrete whereas within 10 20 km of the coast dolomite is the dominant duricrust mineral both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate rich nodules develop and coalesce carbonate progressively replacing and displacing detrital grains the dolomite of the dolocretes forms mosaics of crystals typically 10 70 m in size varying from simple rhombs to spherulites an intermediate morphology named artichoke dolomite from its appearance in sem is particularly abundant authigenic palygorskite is associated with the dolomite dissolution of cores or zones within dolomite crystals has occurred calcite is present as sparry crystals always post dating dolomite and is the expected precipitate from present day soil and groundwaters chemical analyses of dolomite show highly negative values of 13 c to 10 7 pdb and 18 o varying from 0 6 to 3 3 pdb the oxygen isotope values are interpreted as reflecting evaporation of a marine based fluid manganese values of around 1000 ppm show that this fluid was reducing strontium data show variability reflecting mineral fluid reactions the general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred given that the duricrusts lack biogenic features the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons the dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today

geomorphological analysis of paleo drainage systems and their environmental implications in the desert of kuwait a well developed drainage network is carved in the hard calcretized and gypcretized gravelly sand of the pleistocene dibdibba formation in northern kuwait the present day aridity suggests that these drainages were developed during pluvial episodes that took place in the post pleistocene time and therefore are considered as paleo drainage detailed morphometrical analysis of the endoeric drainage systems was performed and the degree of correlation among their different morphometric parameters was investigated based on these parameters the studied drainage basins are statistically grouped into three groups such grouping was confirmed by discriminant analysis the categorical data analysis demonstrated the dependence of these groupings on the surface geology regional topography and local geomorphological settings infiltration measurements revealed that the drainage bedrocks have a low infiltration rate 20 cm h 1 whereas the drainage fill deposits have a relatively high infiltration rate 67 30 cm h 1 the impact of the drainage system pattern and morphometry on the hydrological conditions is discussed and potential near surface low salinity to freshwater aquifers is delineated the role of the studied drainage systems in the occurrence of mobile sand and sand dunes rainwater harvesting and land capability are discussed

characteristics and mechanism of the longyao ground fissure on north china plain china abstract among more than 1000 ground fissures developed over the past 30 years having induced severe geohazards in the north china plain the longyao ground fissure in hebei province is famous for its longest length and causing the worst damage and widest influence in this region in order to reveal the origin of its formation the geological background developmental characteristics and genetic mode of the longyao ground fissure were investigated in detail by geological surveys measurements trenching drilling and seismic exploration this fissure has a total length of 39 km and is characterized by normal fault extension left lateral slip and dominant along polyline distribution these characteristics are well consistent with its underlying fault the nei jv fault the fissure causes the damage to buildings structures along a polyline and in the form of a horizontal tensile crack subsidence and shear failure according to the trenching drilling and shallow seismic profiling this fissure possesses the characteristics of synsedimentary faults reflecting the historical stages of fissure activities regarding its genesis this fissure was generated under the coupling action of multiple factors which took shape after the earthquake and was enlarged under the action of groundwater pumping the regional extension first caused a fracture system in the surface strata and then the action of seismic activities started to control the fracture and finally the pumping action of excessive groundwater and other influential factors promoted the formation of the current ground fissure

spheroidal dolomites origin by hydrocarbon seepage spheroidal dolomite cements are a pervasive and distinctive feature in five exposed lithologies of different geological age in kuwait the spheroids range in diameter from 5 350 m have concentric zones and nuclei of fluid inclusions with or without a radial fabric and compositions varying from near stoichiometric to ca56 mg44 all spheroids appear to be primary in origin with no evidence of replacement some concentric zones show selective calcitization and or leaching most of these features are confined to within 30 m of the surface consequently spheroidal dolomites recognizable at depth in ancient sequences may be indicative of a local unconformity the dolomite distributions are areally correlative with known areas of hydrocarbon seepage the latter being confined to prominent oil field anticlinal trends it is proposed that the dolomitization was caused by groundwaters carrying hydrocarbons to the surface which were then oxidized to carbon dioxide the gas bubbles may have acted as nuclei for spheroid growth with a possible inducement by bacteria which have an affinity for hydrocarbons the implication is that the regional distribution of spheroidal dolomites may be an indicator of a potential reservoir facies at depth

an overview of the tertiary geology and hydrogeology of the northern part of the arabian gulf region with special reference to kuwait abstract tertiary sediments constitute the main source of usable groundwater in kuwait tectonics depositional environment lithology and the hydrogeology of these sediments have been reviewed on a regional scale with special reference to kuwait the review showed that kuwait was situated at the boundary of the stable shelf towards southwest and the unstable shelf towards northeast throughout the tertiary period the tertiary sedimentation started in this area with a marine transgression in the palaeocene shallow marine to sabkha conditions prevailed in the area until the end of the eocene a carbonate evaporite sequence umm er radhuma rus and dammam formation was deposited during this period the sea regressed at the end of eocene and a widespread unconformity causing the absence of oligocene deposits over most of the area marked the event the karstification of the dammam limestone formation that provides localized easier pathways for ground water took place during this period the deposition of the clastic sediments of the kuwait group and its equivalents on the stable shelf under mostly continental conditions started in the early miocene the tertiary aquifers of the area are recharged by occasional rainstorms in the outcrops of saudi arabia and iraq the water flows towards the north and east in the direction of the regional dip and discharges along the present day coast of the gulf the water quality deteriorates in the same direction being more mineralized as it flows through the aquifers the aquifers are presently being exploited at a comparatively high rate since the aquifers extend beyond the political boundaries cooperation among the countries of the region is recommended to ensure the optimum utilization of the scarce water resources of this desert environment

morphological and morphostructural features of kuwait abstract morphostructural analysis and interpretation of the geomorphic features of the surface of kuwait are essentially dependant on the recognition of the structural configuration of the top of the upper eocene dammam formation and its influence on the overlying sediments of the kuwait group the top surface of the dammam formation has an undulatory form representing a series of n s to nnw sse trending domal and flexural structures this surface has regulated to a variable extent the depositional regime and thickness of the overlying kuwait group structures of the dammam formation have directly left an impression on the surface as morphostructural forms and also indirectly controlled the geomorphic forms of the overlying sediments fifteen geomorphic zones characterized by distinct physiographic patterns slope gradients and dependant features are presented on a map data based on the recognition of drainage patterns and slope characteristics were incorporated significant deflection in topographic contours was also identified and geomorphic discontinuities and anomalies were delineated further treatment of the geomorphic zonation data with input from existing geological structural and tectonic data has resulted in the construction of the first morphostructural map of kuwait

a method to predict the group fissuring and faulting caused by regional groundwater decline ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers due to differential settlement the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure here we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks which increasingly affect some middle and large sized cities in the world for that purpose the ground loss theory is applied to sediments overlying a sinusoidal shaped graben this analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear it also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues finally when a crack has completely developed the tensile zone shifts towards the center of the graben creating a new area for potential cracking and faulting

recent movement on the garlock fault as suggested by water level fluctuations in a well in fremont valley california water levels have been continuously recorded since march 1978 in a well in fremont valley where several strands of the adjacent garlock fault zone have exhibited both left lateral displacement and components of normal displacement differences in water levels indicate that a fault segment lies between the observation well and a nearby irrigation well during the 4 year recording period six sharp fluctuations or spikes were noted these fluctuations occurring over 2 to 4 day periods have amplitudes of 15 30 cm they appear to be the result of creep events on a nearby fault two types of creep events are plausible 1 normal slip on an en echelon trace of the garlock fault less than 300 m south of the well with the north side up relative to fremont valley or 2 left lateral slip on the same fault because of the nature of the fluctuations we favor the latter interpretation dislocation models utilizing exponential arc tangent and skewed cosine functions were used to analyze the water level fluctuations associated pressure distribution and fault displacements the results suggest that creep on the fault ranges from several millimeters to a centimeter for individual events estimates of cumulative creep for the period 1978 1982 range from 20 to 50 mm depending on the particular model employed