查看更多>>摘要：It is the first time that the fossil footprints of a group of Middle Eocene elephant ances-tors have been discovered in the Gonjo Basin,East Tibet Plateau.The Gonjo Formation is attributed to the Middle Eocene Epoch(U-Pb age=44.7±1.2 Ma)and consists mainly of purplish-red,medium-to coarse-grained sandstones,siltstones interbedded with mudstones,and conglomerates with sedimenta-ry structures like ripple marks,rip-up clasts,and trough-cross bedding,suggesting fluvial-lacustrine systems.The group of fossil footprints has a characteristic oval-concave shape,and the toe impressions are absent.Some fossil footprints arc overstepped with a pockmarked texture resembling Proboscipeda enigmatica.More than 165 fossil footprints of the group are relatively well-preserved with different di-ameters,which is evidence of highly social behavior and trackmakers of different ages,including calves,juveniles,adolescents,and adults.The size frequency of the fossil footprints enabled us to de-duce the body mass,shoulder height,and hip-height distribution of the trackmakers that crossed the East Tibet Plateau 44.7 Ma ago.The trackmakers comprised an estimated average hip-height of 111.8 cm,an average shoulder height of 172.8 cm for males/155.9 cm for females,and an average body mass of approximately 1 218.1 kg for males/907.8 kg for females.The abundance of fossil footprints reveals that in the Middle Eocene Epoch,the environment was extraordinarily conducive for the elephant an-cestors to live in the East Tibet region.
查看更多>>摘要：Conodonts,as a biotic group,next to ammonoids,pollen and spores,crustaceans and ver-tebrates,provide proxy clues for environment and age assessments of the rocks in which they occur.Conodonts are widely used for Triassic marine biostratigraphy.However,there are various discussions about their multielement taxonomy and evolutionary lineages(e.g.,generation,speciation).Although first studies reported that most Triassic conodont species were unimembrate,studies carried out in the following years maintained that all Triassic conodonts were multimembrate.Although statistical recon-structions of a number of Triassic apparatuses were attempted,the discovery of fused clusters and nat-ural assemblages has subsequently demonstrated that Triassic conodonts arc indeed multimembrate,and all of the elements exist together in the same apparatus.The present paper aims to clarify the evo-lutionary relationship and array of some Lower Triassic conodonts.Columbitella dagisi n.sp.is de-scribed.
查看更多>>摘要：Flexural toppling occurs when a series of layered rock masses bend towards their free face.It is important to evaluate the maximum bending degree and the requirement of supports of flex-ural toppling rock mass to prevent rock mass cracking and even failure leading to a landslide.Based on the rock tensile strain-softening model,this study proposes a method for calculating the maximum cur-vature(Cppmax)of flexural toppling rock masses.By applying this method to calculate Cppm-of 9 types of rock masses with different hardness and rock layer thickness,some conclusions are drawn:(1)the in-ternal key factors affecting Cppmax are E*(E*=Egs/E0,where E0 and Ess are the mean deformation moduli of the rock before and after reaching its peak tensile strength,respectively),the strain εt corresponding to the tensile strength of rock,and the thickness(h)of rock layers;(2)hard rock layers are more likely to develop into block toppling than soft rock layers;and(3)thin rock layers are more likely to remain in flexural toppling state than thick rock layers.In addition,it is found that Cppmax for flexural toppling rock masses composed of bedded rocks such as gneiss is related to the tensile direction.
查看更多>>摘要：This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iver-son's method to analyze the influence of the Lisse effect on the fast groundwater pressure(Pw)response and the slope stability.Furthermore,the sensitivities of the driving force and loess soil parameters were investigated.Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well.The depth to water table before rainfall(H0)had a significant impact on the Lissc effect and the slope stability.When the He was less than approximately 1 m,the rainfall trig-gered a significant Lisse effect and decreased the slope factor of safety(Fs).When the rainfall intensity(Ri)was higher than the saturated hydraulic conductivity(Ks),the Lisse effect and the Fs slightly changed with the increase of the Ri,and the slope tended to be unstable with continuous rainfall.With increasing Ks,the Lisse effect noticeably increased,and the minimum Fs quickly decreases.The analysis of the normalized sensitivity coefficient revealed that H0 had a dramatic impact on the Lisse effect and loess slope stability.The different Ri and Ks values had prominent influences on the Lisse effect and slight impacts on F.
查看更多>>摘要：The curve of landslide thrust plays a key role in landslide design.The commonly used transfer coefficient method(TCM)and Morgenstern-Price method(MPM)are analyzed.TCM does not take into account the moment balance between slices.Although MPM considers the moment bal-ance,the calculation is complex,and it does not consider that the force between slices may be less than zero at the back edge of the landslide.The rationality and feasibility of the improved MPM are verified by calculating the landslide stability coefficient and landslide thrust at different reservoir water levels.This paper studies the law of landslide thrust when the reservoir water level changes,and discusses the determination of design thrust,to provide a certain theoretical basis for the design of reservoir land-slides.
查看更多>>摘要：The short-term effect of heavy rainfall on gPhone gravimeter observation at Zhengzhou Seismic Station is investigated.According to the observation data during Jul.17-20,2021,the correct-ed gravity residual reflects the gravimetric response caused by heavy rainfall.The observed gravity change is dominated by the local effect considering topographic effect on gravity.The deduced water depth near the observation station is about 300 mm.
查看更多>>摘要：Anchor reinforced vegetation system(ARVS)comprises high performance turf reinforce-ment mats(HPTRM),vegetation and anchors.It is a new attempt to apply the system in expansive soil slope protection.The goal of this paper was to evaluate the effectiveness of ARVS in protecting newly excavated expansive soil slopes.The field tests on the bare slope,grassed slope and ARVS protective slope were carried out,including natural and artificial rainfall.During the test,the soil water content,soil deformation,and anchor axial force were monitored,and then the slope protection mechanism of ARVS was analyzed.It was found that ARVS can effectively protect expansive soil slopes compared with bare slopes and grassed slopes.The vegetation and HPTRM form a reinforced turf,and the an-chors fix it to the slope surface,thus restraining the expansion deformation.The axial force on the an-chor of ARVS includes frictional resistance and tensile force transmitted by HPTRM,which is maxi-mum at the early stage of support.The neutral point of the anchor of ARVS moves deeper under atmo-spheric action,but the vegetation and HPTRM on the slope surface can limit this movement.
查看更多>>摘要：If progress is to be made toward improving geohazard management and emergency decision-making,then lessons need to be learned from past geohazard information.A geologic hazard report provides a useful and reliable source of information about the occurrence of an event,along with detailed information about the condition or factors of the geohazard.Analyzing such reports,how-ever,can be a challenging process because these texts are often presented in unstructured long text for-mats,and contain rich specialized and detailed information.Automatically text classification is com-monly used to mine disaster text data in open domains(e.g.,news and microblogs).But it has limita-tions to performing contextual long-distance dependencies and is insensitive to discourse order.These deficiencies are most obviously exposed in long text fields.Therefore,this paper uses the bidirectional encoder representations from Transformers(BERT),to model long text.Then,utilizing a softmax layer to automatically extract text features and classify geohazards without manual features.The latent Dirichlet allocation(LDA)model is used to examine the interdependencies that exist between causal variables to visualize geohazards.The proposed method is useful in enabling the machine-assisted inter-pretation of text-based geohazards.Moreover,it can help users visualize causes,processes,and other geohazards and assist decision-makers in emergency responses.
查看更多>>摘要：It is well known that the deformation and damage of reservoir colluvium landslides are often determined by the combined dynamics of reservoir water level change and rainfall.Based on the systematic analysis of the change law of reservoir water level,rainfall and displacements of reservoir colluvium landslide,this paper proposes the compound hydrodynamic action of rainfall and reservoir water as the unload-load parameter,and the landslide displacement as the unload-load response pa-rameter.Based on this,a physical prediction model of the compound hydrodynamic unload-load re-sponse ratio of reservoir colluvium landslide was established,and the quantitative relationship between the compound hydrodynamic unload-load response ratio and its stability evolution was in-depth ana-lyzed and determined.On the basis of the above research,taking Shuping landslide,a typical hydrody-namic pressure landslide as an example,the unload-load response ratio model is used to systematically evaluate and predict the stability evolution law and the change trend of the landslide under compound hydrodynamic action.The prediction result shows that the variation law of the compound hydrody-namic unload-load response ratio is consistent with the dynamic evolution law of its stability.There-fore,the above studies show that the compound hydrodynamic unload-load response ratio parameter is an effective displacement dynamic evaluation parameter for reservoir colluvium landslides,so it can be used in the prediction of the reservoir colluvium landslides.
查看更多>>摘要：Weathered rock(especially granite)slopes are prone to failure under the action of rain-fall,making it necessary to study the response of weathered rock slope to rainfall infiltration for land-slide prevention.In this study,a series of model tests of weathered rock slope under different condi-tions were conducted.The matric suction,volumetric water content,earth pressure and deformation of slope were monitored in real time during rainfall.The response of the slope to rainfall infiltration,fail-ure process and failure mode of slope under different conditions were analyzed,and the early warning criterion for the failure of weathered rock slope caused by rainfall was studied.The results show that the slope deformation evolution process under rainfall condition was closely related to the dissipation of matric suction.When the distribution of the matrix suction(or water content)of slope met the condi-tion that the resistance to sliding of the slip-mass was overcome,the displacement increased sharply and landslide occurred.Three factors including rainfall process,lithologic condition and excavation condition significantly affect the response of weathered rock slope to rainfall.It can be found from the test results under different conditions that compared with intermittent rainfall condition,the rainfall intensity and infiltration depth were smaller when the slope entering accelerated deformation stage un-der the condition of incremental rainfall.The accumulated rainfall when weathered clastic landslide oc-curring was greater than that of weathered granite,which results in greater disaster risk.The excava-tion angle and moisture distribution of a slope were the main factors affecting the stability of a slope.In addition,the evolution processes and critical displacement velocities of slopes were studied by com-bining the deformation curves and matrix suction curves,which can be used as reference for early warning of rainfall-induced weathered rock landslide.
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