Engineering geological classification of the structural planes for hydroelectric projects in Emeishan Basalts

The scale and characteristics of rock mass are important indexes of the rock mass structural plane classification.This paper firstly analyzes the spatial distribution characteristics,the structural plane types(original structural plane,tectonic structural plane and hypergenic structural plane) and the associated features of the Emeishan basalts and then studies the classification schemes of the built hydropower structure planes of different rock areas(the east district,the central district and the west district) in the Emeishan basalt distribution area,Southwest China.Based on the analysis and comparison of the scale and the engineering geological characteristics of the typical structure planes in the basalt hydroelectric Stations,the types of structural planes are used in the first order classification.The secondary order classification is made by considering the impact factors of rock mass quality,e.g.,the state of the structural planes,infilling,joint opening,extending length,the grade of weathering and strength.The engineering geological classification for Emeishan basalt is proposed.Because there are no evidences of a large structure presenting in study area,the first-order(Ⅰ) controlling structural planes do not appear in the classification,there only appear Ⅱ,ⅡⅠ,Ⅳ and Ⅴ grade structural planes influencing the rock-mass quality.According to the different rock-block types in bedding fault zone,the second-grade(Ⅱ) structural planes consisted of bedding fault zone is further classified into Ⅱ_1,Ⅱ_2 and Ⅱ_3.The third-grade(ⅡⅠ) structural planes constructed by intraformational faulted zones are not subdivided.According to the different characteristics of intrusion,alteration and weathering unloading structural planes,the Ⅳ grade structure plane is divided into Ⅳ_1,Ⅳ_2 and Ⅳ_3.According to the development characteristics of joints and fractures,the Ⅴ grade structure plane is divided into fracture Ⅴ_1 and columnar joint Ⅴ_2.In all,the structural planes are classified into four groups with nine subsets.The research proposes the engineering geological classification of the structural plane for the hydropower project in the Emishan basalts,and the result of the study has a potential application in similar regions.     

On the initiation,movement and deposition of a large landslide in Maoxian County,China

At 5 am 24 th June 2017, a catastrophic landslide hit Xinmo Village, Maoxian County, Sichuan Province, China. The slide mass rushed down from an altitude of 3400 m and traveled 2700 m in a high velocity. The 13 million m~3 deposition buried the whole village and caused about 100 deaths. The source area of the landslide is located in a high steep slope, average slope angle is 40o and maximal angle is 65o. The strata are interbedded Triassic Zagunao Formation metamorphic sandstone and slate with the dip slope angle of 45°. Based on high-resolution satellite remote sensing image, UAV image, DEM data, and field investigation, failure mechanism, travel features, and deposit characteristics were analyzed. The results showed that this landslide was influenced by Songpinggou Fault zone. According to the topography before the failure, the landslide is located in the back scarp of an antecedent landslide induced by Diexi Earthquake in 1933. The bedding slope provided potential rupture surface. Historical seismic activities and long-term gravitational deformation caused rock mass accumulated damages. Weathering and precipitation weakened the rock mass and finally induced shearing and tension failure. A huge block detached from the top rock slope, pushed the past landslide deposits in the middle part, rushed out of the slope bottom in a high velocity and buried the Xinmo Village. The rapid movement entrained and brought the soil into the Songping Gully which recoiled with and bounced back from the opposite mountain.     

Indexing the engineering properties of residual soils in the southern slopes of Mashhad,NE Iran

Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. The properties of residual soils are a function of the degree of weathering. A series of index properties, engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran. In the present research, the index properties of residual soils in the south of Mashhad city in Iran are investigated.Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples. Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks.Subsequently, physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards. Also, the mineralogical composition, chemistry, and texture of the soil were evaluated in 51 profiles. The field observations showed the difference in the weathering profile of residual soils deposited on various rocks(igneous, sedimentary, and metamorphic). These profiles mainly consisted of two horizons includingresidual soil on top and saprolite at the bottom. The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth. Moreover, depending on the type of origin rock, the properties are different in various types of residual soils. In most of the samples, the moisture content of soil horizons was also increased by depth. Based on the unified soil classification(USCS), the soils of the upper horizons appeared to be classified as ML(Lean silt) and CL(Lean clay) while the soils of the lower horizons(saprolite zone) fall in SC(clayey sand), SM(silty sand), and SW(wellgraded sand) classes. Moreover, the results demonstrated that the particle size of the soil was increased by depth. Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth, weathering level, and type of parent rock. Considering the concentration of the number of lines and the concentration of the points of intersection, the length and dimension fractal of lineaments in the southeastern part of the study area, it is evident that this zone possesses weathering severity and soil thickness. Fieldwork data from this zone have also verified the severity of weathering conditions. The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development. The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area. Slope inclination and soil thickness are controlled by weathering and erosion processes.     

Geological analysis of gravitational rock slope deformation: a case from Nujiang River,China

This paper presents a study on the gravity-induced rock slope deformation observed along the Nujiang River in China. We performed a comprehensive field investigation and analysis to identify the deformation pattern of the slope and its triggering factors. Moreover, a geological-evolutionary model was developed, and it considers the effects of river incision and rock mass degradation caused by weathering and simulates the mechanisms underlying the initiation and progression of the slope deformation. The results support the proposed failure mechanism in which fractures within the slope are induced by rock mass degradation caused by weathering. Importantly, the modeling reveals that compressional deformation at the toe of the slope results in a tensile failure in the upper portion of the slope, demonstrating that the rock mass in the slope toe is the key factor inducing slope deformation. This analysis of slope deformation and its spatial and temporal correlations with rock weathering and river incision reveal the main triggering factors that control the evolution of the studied slope and provide insights into the deformation process.     

软硬互层顺层岩质边坡破坏试验

软硬互层结构的顺层岩质边坡破坏类型复杂、难于防治, 针对此类边坡地质灾害易发、多发的问题, 从坡面角度、岩层倾向及组合形式、节理分布等方面进行了研究。边坡物理模型试验是揭示边坡变形破坏机理的重要手段, 基于相似理论, 以重庆市万州区孙家滑坡为工程依托, 根据滑坡区地质勘探报告设计了室内边坡物理模型试验; 试验通过顶升模型箱模拟重力加载来探究顺层岩质边坡发生破坏时, 前缘坡角和软弱夹层倾角之间的关系; 结合有限元分析软件Plaxis 2D对物理模型进行了多组数值模拟试验, 以验证软硬互层顺层岩质边坡破坏机制。试验结果表明: 对于顺层岩质边坡, 当软弱夹层的倾角在22°左右, 前缘开挖坡角58°左右时, 顺层岩质边坡容易发生滑动, 滑动面为后缘节理面和软弱夹层的贯通面。因此, 顺层岩质边坡稳定性受层面和节理面密度的控制, 当边坡含多层软弱层面时, 易沿层面和后缘节理贯通面发生破坏, 随着软弱面层数增加, 边坡稳定系数逐渐降低。研究成果可以为公路开挖切坡导致的顺层岩质边坡失稳机理研究及其稳定性评价提供理论依据, 为顺层岩质边坡失稳的预测预报提供支撑。      

济南市南部山区水井北村滑坡成因机制及稳定性研究

2019年8月,济南市南部山区水井北村发生滑坡地质灾害。根据水井北村滑坡的地质背景,针对性布置物探、钻探等勘查手段,研究滑坡工程地质特征,分析水井北村滑坡类型及发生的地质成因机制;采用刚体极限平衡分析法,研究水井北村滑坡整体稳定性。研究认为断裂发育、岩层风化、地势、浅层含水层受降雨影响,是水井北村地质灾害点具备滑坡发生的内在条件。降雨和泉水入渗、耕植等行为是滑坡发生的外在条件。水井北村山体滑坡在天然条件下,稳定系数平均值为1.033,整体属欠稳定状态。暴雨状态下,稳定系数平均值为0.903,坡体处于不稳定状态。     

三峡库区大型-特大型层状岩质滑坡成因模式及地质特征分析

三峡库区大型-特大型滑坡发育，尤以层状岩质滑坡的危害性大。因库区各段地质条件差异使得滑坡成因模式各不相同，这影响了滑坡的运动形式和岩土体解体程度。在收集三峡库区51处典型的大型-特大型层状岩质滑坡调查资料基础上，根据堆积岩体结构和区段地质条件反推该段滑坡破坏成因模式，而不同成因模式下的滑坡坡体渗透性不同，分析已有滑坡对库水位变动存在的复活响应差异，据此得出以下结论:①在成因模式上，除顺层滑移型滑坡在库区中均有分布外，从库首至库尾随着岩层倾角的逐渐减缓，滑坡成因模式从崩塌型、反倾弯曲型逐渐过渡到平推式；②在坡体渗透性上，成因模式造成的岩体结构变化与坡体中的泥质含量共同作用，导致顺层滑移型滑坡前后缘渗透性存在较大差异；反倾型滑坡渗透性则整体变化较小；③在库水位变动影响下，不同坡体渗透性与滑面形态共同决定了滑坡的复活变形差异。      

Characteristics and failure mechanism of an ancient earthquake-induced landslide with an extremely wide distribution area

The Lamuajue landslide is located in Lamuajue village on the right bank of the Meigu River,Sichuan Province, China. This landslide is an ancient landslide with an extremely wide distribution area,covering an area of 19 km~2 with a maximum width of5.5 km and an estimated residual volume of 3×10~8 m~3.The objectives of this study were to identify the characteristics and failure mechanism of this landslide. In this study,based on field investigations,aerial photography, and profile surveys, the boundary,lithology, structure of the strata, and characteristics of the landslide deposits were determined. A gently angled weak interlayer consisting of shale was the main factor contributing to the occurrence of the Lamuajue landslide. The deposition area can be divided into three zones: zone A is an avalanche deposition area mainly composed of blocks,fragments, and debris with diameters ranging from0.1 m to 3 m; zone B is a residual integrated rock mass deposition area with large blocks,boulders and "fake bedrock"; and zone C is a deposition zone of limestone blocks and fragments. Three types of failure mechanism were analyzed and combined to explain the Lamuajue landslide based on the features of the accumulation area. First, a shattering-sliding mechanism caused by earthquakes in zone A. Second,a sliding mechanism along the weak intercalation caused by gravity and water in zone B. Third,a shattering-ejection mechanism generated by earthquakes in zone C. The results provide a distinctive case for the study of gigantic landslides induced by earthquakes, which is very important for understanding and assessing ancient earthquakeinduced landslides.     

基于多源数据的谭家湾滑坡变形机制及稳定性评价

针对2016年5月发生于秭归县西北部的谭家湾滑坡,结合卫星遥感影像、现场勘查资料以及历史资料等多源数据,初步明确了滑坡的影响区域、特征及发生时序;综合采用钻探、槽探、物探等手段,开展室内外相关实验,明确了滑坡区的地层特性以及岩土体物理力学性质指标,通过分析该区裂缝位移及GPS数据,对该边坡的变形机制进行了探讨,并对该区稳定性进行了评价。结果表明:①谭家湾滑坡属于不规则"圈椅形"中型松散层的水库下降型滑坡,滑坡区的地表形态、地质构造及岩性等因素决定了滑坡的形成和发育,库水位和降雨的共同作用激励了滑坡的变形;②滑坡根据时序共分为3级滑体,总体呈现多次、多层、相互影响的演化特点,第三级滑体具有牵引式特征;③滑坡体内地下水位随库水位下降而下降,但下降速率缓于库水位,随之坡体内水力梯度和渗透力显著变大,此时碰到强降雨,将会导致坡体地下水赋存,岩土体软化,加剧滑坡变形,须施加必要的防护措施。④稳定性分析表明,该滑坡现处于临界稳定状态,一旦发生降雨和库水位变化,局部段可能发生失稳滑动。      

呷爬滑坡滑带土蠕变特性及其稳定性

水库滑坡变形破坏受其岩土体蠕变特性及环境因素的影响。当滑坡进入加速变形阶段后,变形骤然增大,失稳概率增加。为了研究滑坡岩土体蠕变特性及其稳定性,选取锦屏一级水电站呷爬滑坡为研究对象,采用坡表位移监测曲线分析与室内三轴蠕变试验相结合的方法,建立了Burgers蠕变模型结合FLAC3D软件进行了滑坡稳定性研究。分析坡表位移-时间曲线发现,坡体变形特征与一般滑坡土体的蠕变特征具有相似性,滑带土室内三轴蠕变试验结果表明,滑带土变形可划分为瞬时蠕变、减速蠕变与稳定蠕变3个阶段,同时其瞬时变形量、稳定蠕变速率均随围压以及应力水平的增大而增大。基于滑带土蠕变特性的Burgers蠕变模型的计算结果,对比了常规强度折减法与考虑蠕变的强度折减法的滑坡稳定性系数,计算结果表明呷爬滑坡目前处于稳定状态,在一个计算周期内考虑蠕变的强度折减法较常规强度折减法的稳定性系数下降了0.04,因此,揭示滑坡土体蠕变特性并在此基础上研究其稳定性具有实际意义。      

Geomechanics of hazardous landslides

A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass （deformation and strength parameters）, is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models.     

宝鸡黄土中的风化壳

根据野外调查,在宝鸡黄土中确定了五个时期的风化壳,它们分别为第1～5层古土壤与其下的风化黄土构成。根据X-射线衍射得知,这些风化壳为水云母和绿泥石等构成的粘土型风化壳。CaCO_3淀积深度和Fe_2O_3、Al_2O_3迁移特征表明第1和3～5层古土壤与其下黄土构成的风化壳发育时处于酸性风化阶段,当时年平均降水量在900mm以上;第2层古土壤与其下风化黄土构成的风化壳发育时处于中性风化阶段,当时年平均降水量为800mm左右。     

The starting mechanism and movement process of the coseismic rockslide: A case study of the Laoyingyan rockslide induced by the “5.12” Wenchuan earthquake

The"5.12"Wenchuan earthquake in 2008 triggered a large number of co-seismic landslides.The rear boundary or cracks of co-seismic landslide are generally located at the steep free surface of thin or thick mountains.Dynamic process of this kind of landslides could be divided into two parts:the seismic dynamic response of the slope and the movement process of rock mass.Taking the Laoyingyan rockslide as an example,the amplification effect was studied by single-degree-of-freedom system analysis method.Besides,the dynamic process of landslide under seismic loading was simulated by the finite difference method(FDM)and discrete element method(DEM).The amplification coefficient of the rockslide to seismic wave is 1.25.The results show that the critical sliding surface of the Laoyingyan rockslide was formed at the 23 th seconds under the action of seismic wave.At the same time,tension failure occurred at the rear edge of the sliding mass and shear failure occurred at the front edge.The maximum displacement was 0.81 m and the initial velocity was 2.78 m/s.During the initiation process of the rockslide,the rock mass firstly broke down along the joints which are along the dip of the rock stratum,and then collapsed bodily along the secondary structural planes.In the process of movement,the maximum velocity of rock mass was 38.24 m/s.After that,the rock mass underwent multiple collisions,including contact,deceleration to 0 and speed recovery after rebound.Finally,due to the constant loss of energy,the rocks stopped and accumulated loosely at the foot of the slope.The longest distance of movement was about 494 m.Besides,the smaller the damping ratio,the farther the rock mass moved.Compared with the results without considering the amplification factor,the movement distance of landslide by considering the amplification factor was more accurate.The study of the Laoyingyan rockslide is helpful to strengthen our field identification of potential co-seismic rockslides.At the same time,understanding its movement and accumulation process can help us better predict the hazard scope of the co-seismic rockslides,and provide a reference for the design of treatment projects.     

基于有限元修正节理岩质边坡稳定性计算的解析解

采用有限元方法探讨在人工开挖或自然侵蚀环境下,岩质边坡体内应力场的变化及节理发育形成机理,并采用有限元强度折减法对后缘具有张节理边坡的稳定性影响因素进行敏感性对比分析,进而得出具有非贯通节理边坡稳定性计算的修正解析解.结果表明:卸荷及风化作用导致边坡体由表及里出现应力重分布及应力集中的现象,使边坡后缘由顶部向下发育一簇...     

辽西凸起斜坡区风化壳油气运移特征及控藏作用

随着勘探程度的提高, 小型复杂断块圈闭已成为当前凸起区油气勘探的重点领域, 为了明确辽西凸起断块圈闭油气差异富集的原因, 利用三维地震、测录井、薄片等数据资料, 通过三维流线定量模拟的方法, 分析凸起斜坡区潜山顶面风化壳特征, 建立"壳-断"耦合油气运移模式, 刻画斜坡区油气优势运移路径, 从而明确风化壳运移对凸起断块油气差异富集的控制作用。结果表明: ①研究区潜山历经多期构造运动, 且潜山岩性主要为下古生界碳酸盐岩和太古界花岗岩, 岩性性质较脆, 易被风化剥蚀, 风化壳溶蚀孔隙及构造裂缝普遍发育, 且分布稳定, 形成斜坡区油气侧向长距离运移的主要通道; ②斜坡中带受反向断层控制形成断隆构造, 油气沿风化壳的运移受斜坡断隆带遮挡, 形成"壳-断"耦合油气运移模式, 断隆带断距大小控制风化壳油气侧向运移能力; ③利用三维流线定量模拟的方法, 刻画出研究区四级油气优势运移通道, 明确不同级别油气运移通道对凸起断块油气富集程度的控制作用。该研究成果有效指导辽西凸起油气勘探实践, 并填补了富油凹陷成熟凸起区油气成藏认识及研究方法。      

兴仁“6·10”彭家洞高速滑坡运动特征与形成机理

2021年6月10日20时30分左右, 贵州省兴仁彭家洞发生高速滑坡, 滑坡体高速运动沿途铲刮坡面崩塌堆积体, 造成3人遇难, 18栋房屋损毁。通过对滑坡发生前后影像资料遥感解译、灾害发生现场详细的地质调查及室内综合分析等技术手段, 对彭家洞滑坡的特征进行了详细描述, 阐明了滑坡发生的运动特征与形成机理。研究表明: 斜坡地形"上陡-中缓-下陡"与岩土结构"上硬下软"是滑坡形成的内在因素, 人类工程活动、强降雨的饱水加载和下渗软化作用是滑坡形成的外在因素; 滑坡平面形态呈折线形, 根据运动特征和堆积结构将滑坡分为滑源区(Ⅰ)、铲刮-流通区(Ⅱ)、铲刮堆积区(Ⅲ)3个区; 滑坡是由危岩带形成、滑坡孕育及斜坡失稳3个阶段孕育形成的挤压-推移式高速滑坡。研究结果对贵州类似的斜坡地带及岩土结构区域开展防灾减灾工作具有较强的指导作用。      

湖北省阳新县基岩滑坡变形因子及其破坏模式

斜坡变形受众多因子综合控制, 不同因子的敏感性与作用规律在变形过程中差异明显。以湖北省阳新县顺层基岩滑坡为研究对象, 通过正交试验结合离散元数值模拟的方法, 研究多个影响因子对应顺层滑坡变形的敏感性并确立主导因素, 随后基于响应面拟合主导因素与滑坡不同部位变形程度间的量化关系, 揭示主导因素交互作用对滑坡变形破坏模式的影响规律。结果表明, 在研究区内坡度与岩层倾角分别为影响顺层滑坡变形的主导与次主导因素, 滑坡的变形破坏模式受控于二者的交互作用。在中-陡倾顺层滑坡中, 当坡度小于岩层倾角时, 滑坡变形主要集中在坡顶, 且变形程度随岩层倾角的增加而增大, 表现出滑移-弯曲的变形破坏模式; 在缓倾顺层滑坡中, 当坡度大于岩层倾角时, 滑坡坡脚位移较坡顶显著, 其坡脚变形程度随坡度的增加而增大, 以滑移-拉裂变形为主。研究成果可为该类滑坡的防治工作提供参考。      

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City,China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow,resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as "instability-translational slide-tension fracture-collapse" and the formation mechanism as "translational landslide induced by heavy rainfall". The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research onpotential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.     

COMPARISON OF QUATERNARY DEPOSIT ENVIRONMENT AMONG LUSHAN,HUANGSHAN AND TIANMU MOUNTAINS

TheQuaternalypaleo--environmentoftheLushan,HuangshanandTianmumountainsisasignificantacademicproblemtowhichmuchattentionhasbeenpaidbymanyresearchersingeosciencecircle.Manyscholarshavestudiedtheproblemandgotalotofachivementsoverthepastyears(Lee,1933;Lee,1936;Lee,1947;Ren,1953;Huang,1963;Li,1974;Shi,1989).HOWever,identicalviewsandconclusionshavenotbeenreachedyetuptillnow,especiallylackingofcomprehensivestudyforsedimentsintheseregions.Inrecentyears,applyingsedimentalcomprehensiveindexgotfromv…     

基于无人机倾斜摄影技术的崩塌隐患早期识别及影响区划分方法

高位危岩崩塌极具隐蔽性、突发性和灾难性,传统的接触式调查方法在安全性方面无法完全保障并且也难以彻底查清边坡上各危岩块体的空间分布及发育特征,因此如何安全快速准确地获取边坡面上关键地质信息,一直是崩塌地质灾害调查及评价研究中的难点之一,也是防灾减灾工作中极为重要的环节。以连云港市某矿区高陡岩质边坡为例,提出了一套基于无人机倾斜摄影技术的崩塌隐患早期识别及影响区划分方法体系,该方法体系通过倾斜摄影技术获取研究区高分辨率影像及构建三维高精度地质模型,在此基础上利用测线法提取并统计边坡优势结构面空间展布特征及相关参数,利用赤平投影法对矿区高边坡关键危岩块体失稳模式进行判别,在完成关键危岩块体稳定性评价并划分稳定等级的前提下使用Rocfall模拟最不利工况下崩落体失稳后的滚落运动特征,从而划分出不同级别的崩塌影响区,为最终的地质灾害防治提供依据。研究表明,无人机倾斜摄影技术在崩塌隐患早期识别、破坏模式分析、稳定性评价以及崩落体威胁范围划定等方面具有显著的可行性和优越性。所提出的基于无人机倾斜摄影技术的崩塌隐患早期识别及影响区划分方法体系具有重要的参考价值。