库水位下降速率对上孝仁村滑坡的稳定性影响

为探寻三峡坝址水库蓄水水位在日降幅(0.6 m/d、0.8 m/d、1.0 m/d、1.2 m/d)的情况下对上孝仁滑坡稳定性的影响.通过监测数据及Geo-Studio数值分析软件模拟出不同工况条件下的滑坡渗流场,在此基础上计算获得了不同工况条件下的滑坡稳定系数.得出的结论表明:上孝仁村滑坡现阶段正处于基本稳定状态,滑坡的稳定性系数随着水库蓄水水位减小而降低,当水库蓄水水位下降到145 m时,滑坡稳定性数值最小.水库蓄水水位下降速率越大,滑坡稳定性数值下降越大.在排除降雨条件的情况下,稳定性系数的下降幅度会随着下降速率的增加而升高.     

基于矢量和法的库水位下降边坡稳定性研究

为了研究库水位的下降对高陡边坡稳定性及变形的影响,以锦屏一级水电站左岸边坡为例,基于饱和渗流理论,以左岸坝头滑移破坏模式为研究对象,利用矢量和稳定性评价方法研究不同库水位下降速度对锦屏一级电站左岸边坡的稳定性影响规律。研究表明:当库水位以1 m/d的速度由1 880 m高程下降至1 800 m高程时,左岸坝头滑移破坏模式的安全系数由1.214降低到1.147,且安全系随着库水位下降趋于稳定,而当库水位下降速度达到2 m/d时,安全系数的降低速度随着库水位的下降逐渐加剧,当库水位达到1 800 m高程时,安全系数降至1.052,左岸坝头滑移破坏模式接近临界状态;库水位下降条件下坡体最大位移处发生在坝头滑移破坏模式潜在滑动面的剪出口位置。     

库水位骤降条件下滑坡稳定性分析

三峡水库蓄水后,库水位消落对库岸滑坡稳定性具有重要影响。在详细调查三峡库区奉节县龙潭滑坡工程地质条件的基础上,分析了滑坡的发育特征、变形破坏机制、诱发因素及形成机理,根据三峡库水位调控方案,运用Ｇｅｏ-ｓｔｕｄｉｏ软件模拟库水位从１７５ｍ降至１４５ｍ的滑坡渗流场,评价了不同库水位下降速率工况（０.６～１.２ｍ／ｄ）的滑坡渗流场特征及其稳定性。研究表明：该滑坡处于稳定状态,稳定性系数随库水位下降速率的增大而减小;浸润线的下降速率慢于库水位下降速率,存在明显滞后性。研究成果对预报三峡水库库岸滑坡灾害具有一定的参考价值。     

库水位上升对古滑坡稳定性的影响

以九甸峡库区坎前古滑坡为例,研究水库蓄水初期对古滑坡稳定性的影响。采用GPS对该边坡进行高精度、连续性的位移监测,结合滑坡具体的工程地质条件,对其变形特征进行分析,并且采用Geo-slope计算不同蓄水速率条件下的库岸边坡的安全系数。结果表明,蓄水初期库岸边坡整体较为稳定,蓄水速率越大对其稳定性越不利,库水上升速率超过0.5 m/d时将会发生局部失稳;滑体中部变形较大,变形速率具有逐渐变小的趋势;变形破坏模式为中后部分块、分级推移前缘的蠕变破坏特征。蓄水初期古滑坡整体较为稳定,库水位快速上升时将会出现局部失稳;采用Geo-slope分析滑坡稳定性变化规律,与采用GPS监测数据分析的规律相符,验证了监测数据的可靠性。     

基于MIDAS GTS的道路风化边坡稳定性分析

针对G318线成都地区某路段涉及的某风化边坡的稳定性问题,采用传递系数法和有限元法对边坡的稳定性进行了计算分析。两种方法得到的计算结果基本一致。长期自然露天的风化土边坡,基岩分布不均,在旱季整体处于稳定状态;在雨季,其稳定系数、位移、应力、剪切应变会发生较大变化,处于不稳定或欠稳定状态。为保证道路安全,应对此类边坡进行加固处理。     

基于FLAC的南平市红桃山边坡稳定性数值分析

对闽西南平市红桃山边坡地质环境条件进行了系统的调查研究,分析了边坡岩土体结构、边坡周界、变形特征等,并结合FLAC数值模拟,绘出竖向应力云图、观测点水平位移图、最大不平衡力变化曲线图等．通过FLAC程序内置的SolveFos求解器求得的边坡安全系数为1．24,说明此边坡整体处于稳定状态,无滑动趋向．     

库水位下降的饱和-非饱和土坝渗流数值模拟

基于非饱和土渗流的理论,借助Geo-slope的有限元数值模拟软件,对库水位下降过程中的饱和-非饱和土坝进行了数值模拟分析,分析结果给出了坝体在库水位下降的过程中,坝体中孔隙水压力的消散状况以及坝体中自由水面位置、形态的变化情况等。结果表明:非饱和-饱和坝体中,在水位下降的各个时刻,由于非饱和区的存在,坝体中的自由水面的形态呈上凸状,且孔隙水压力消散速度变缓。     

蓄水初期库岸边坡稳定性研究

以九甸峡库区某库岸边坡为例,采用GPS对该边坡进行高精度、连续性的位移监测,研究水库蓄水初期库岸边坡稳定性的影响因素。结合滑坡具体的工程地质条件和变形特征,采用边坡熵分析不同库水位条件下的库岸边坡的稳定性。结果表明,蓄水初期库岸边坡受库水位及蓄水速率影响较小,整体上较为稳定;滑体中部变形较大,变形速率具有逐渐变小的趋势;变形破坏模式为中部分块、分级牵引后缘的蠕变破坏特征。针对滑体的变形特征,提出合理的治理措施,对类似工程具有借鉴意义。     

水位变动速度对某库区岸坡堆积体稳定性的影响

水位变动期间库区岸坡堆积体渗流场及稳定性的变化是一个动态过程,如何评价水位变动速度对堆积体稳定性的影响是工程上一个重要课题。采用有限元计算与刚体极限平衡分析相结合的方法,探讨了水位变动速度对堆积体渗流场及稳定性的影响机理和规律,研究成果表明,水位变动速度对堆积体在水位变动期间瞬时渗流场有着较大的影响,较大水位上升速度对堆积体稳定性有利,但水位下降速度增大对堆积体稳定性不利,水位下降速度由0.5增大至5 m/d,堆积体稳定性系数可降低15%～20%,水位下降期间堆积体危险水位往往出现在堆积体坡脚以上1/3～1/5坡高处。     

水位升降对库区非饱和土质岸坡稳定性的影响

针对传统的饱和土理论在分析库岸边坡渗流和稳定问题中存在的不足,以非饱和 饱和渗流分析程序模拟水位升降过程中岸坡内孔压场（包括浸润线以上的基质吸力场）.在此基础上,考虑基质吸力对抗剪强度的贡献及其对安全系数的影响,进行了边坡稳定的极限平衡分析,并对影响岸坡渗流场的主要水力参数进行了敏感性分析.分析结果表明,坡外水位升降时,坡内浸润线及其上的基质吸力场发生显著变化,进而影响岸坡稳定;水位升降过程中,岸坡安全系数的变化规律非常复杂,坡内孔隙水压力、坡外水推力和土体容重对稳定安全系数的贡献规律随水位变化而变化;土体的渗透性能和土 水特征曲线的斜率显著影响了水位升降过程中岸坡稳定安全系数的变化规律.     

Mechanism analysis of landslide of a layered slope induced by drawdown of water level

1 Introduction The instability of slopes on the river banks and the reactivation of ancient slopes, in- duced by drawdown of water level, are great danger for the local residents and for thehydroelectric engineering. A lot of accidents or disasters relating to the drawdown of water level can be found in literatures. In October 1963, the landslide, near the recently constructed Vajont Reservoir dam at that time, caused the failure of the toppest hyper- bolic arching dam in the world, ruined on…     

Q mechanism analysis of landslide of a layered slope induced by drawdown of water level

The frequent drawdown of water level YanYangtze River will greatly influence the stability of the widely existing slopes in the Three Gorges reservoir zone, especially those layered ones. Apart from the fluctuating speed of water level, the different geological materials will also play important roles in the failure of slopes. Thus, it must be first to study the mechanism of such a landsllide caused by drawdown of water level.A new experimental setup is designed to study the performance of a layered slope under the drawdown of water level. The pattern of landslide of a layered slope induced by drawdown of water level has been explored by means of simulating experiments. The influence of fluctuating speed of water level on the stability of the layered slope is probed, especially the whole process of deformation and development of landslide of the slope versus time. The experimental results show that the slope is stable during the water level rising, and the sliding body occurs in the upper layer of the slope under a certain drawdown speed of water level. In the process of slope failure, some new small sliding body will develop on the main sliding body, and the result is that they speed up the disassembly of the whole slope.Based on the simulating experiment on landslide of a layered slope induced by drawdown of water level, the stress and displacement field of the slope are calculated. The seepage velocity, the pore water pressure, and the gradient of pore water head are also calculated for the whole process of drawdown of water level. The computing results are in good agreement with the experimental results. Accordingly, the mechanism of deformation and landslide of the layered slope induced by drawdown of water level is analyzed. It may provide basis for treating this kind of layered slopes in practical engineering.     

水位骤降对土质渠道边坡稳定性影响的弹塑性有限元分析

用抗剪强度折减弹—塑性有限元法研究渗流作用下土质渠道边坡的稳定性问题,在土体本够模型中采用了最适合进行土体稳定分析的Mohr Coulomb准则,同时考虑了土体拉伸屈服及拉伸屈服后强度软化对土体稳定性的影响,完善了屈服准则,并用Fortran90语言编制了相应的计算程序.程序的适应性算例所得的稳定安全系数比简化Bishop法小1 2%～5 8%,证实了其应用于工程的可行性.结合渗流有限元对水位骤降情况下的渠坡稳定进行了计算,结果表明,有限元法可以非常方便地将渗流场和应力场相结合,克服了传统条分法难以结合渗透力的缺点,为复杂情况下渠坡结构设计提供了依据.     

Influences of rainfall infiltration on stability of accumulation slope by in-situ monitoring test

In order to improve the understanding of the fundamental mechanism of rainfall infiltration induced landslides in accumulation slope and to clarify some important characteristics of slope performance, artificial rainfall simulation tests and field synthetic monitoring were carried out on a typical accumulation slope of Shangrui Freeway in Guizhou Province, China. The monitoring results show that the most accumulation landslides caused by rainfall infiltration are shallow relaxation failure, whose deformation zone lies within the top 0–4 m soil layer. The deformation of slope gradually reduces from the surface, where the greatest deformation lies in, to the deep part of slope. The average percentage of infiltration during the first 2 h is 86%, and then it reduces gradually with time because of the increase of the surface runoff. The average percentage of infiltration drop to a relatively stable value (50%) after 6 h. Rainfall infiltration causes obvious increase of pore-water pressure, which may result in a reduction of shear strength due to a decrease in effective stress and wetting-induced softening. The double-effect of rainfall infiltration is the main reason of rainfall infiltration induced landslides in accumulation slope. Foundation item: Project(50678175) supported by the National Natural Science Foundation of China     

降雨条件下土体坡度及含水率对边坡稳定性影响的试验研究

通过对坡度分别为30°、38°、45°的3种土坡进行人工降雨试验,对沿坡面的5个等分观测点进行土坡滑动位移及含水率的观测,并在各土坡靠近坡面的相同位置选取土样进行UU三轴试验,测算出相应的粘聚强度,并对试验过程中采集到的数据进行分析处理,探究土坡滑动的影响因素之间的内在机理。试验结果表明,在试验研究的坡度及含水率范围内,土坡稳定性的影响因素间存在以下规律:坡度较小的土坡沿坡面各分观测点竖向位移变化较小,而坡度较大的土坡竖向位移变化较大,且在上中部位置下滑更为明显;坡体的泥流率与坡度之间存在线性关系,坡度越大,泥流率越大;坡面各分观测点的含水率整体水平与坡度有关,坡度越小,则降雨后含水率越大,且在坡面中下部位置处的含水率变化更大;同等含水率的情况下,随着坡度的增加,土体粘聚强度有增长的趋势。而对于同坡度的土坡而言,含水率越小,则粘聚强度越大。针对试验中发现的规律,通过数值模拟提出了试验降雨条件下“坡度-泥流率”、“坡面位置-含水率”和“含水率-粘聚强度”的关系式。     

Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

1 Introduction The effect of seepage flow is a key problem in the investigation on the landslide fail- ure. Water in landslide comes mainly from the infiltration of rainwater and seepage flow of ground water. Rivers and reservoirs are the dominant sources of ground water in landslide. The infiltration of water will cause variations of the ground water level in landslides, which sometimes play a key role in the landslide stability. In particular, the fluctuation of water level varies remarkabl…     

Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried out to determine the pore pressure during water level fluctuation. The variations of transient pore pressure vs. time at different locations of the simulated rock-soil system were acquired and processed, and meanwhile the deformation and failure of the model are observed. The experiment results show that whether the porous media are saturated or not, the transient pore pressure is mainly dependent on the water level fluctuation, and coupled with the variation of the stress field.     

深层排水孔堵塞对富水岩质高边坡稳定性的影响

高边坡施工或运营期间常因多种因素作用导致排水孔堵塞,从而抬升地下水位,影响边坡稳定性和支护结构的安全。基于渗流折射定律,采用空气单元法模拟排水孔,开展了岩质高边坡渗流应力耦合分析,重点研究了排水孔不同堵塞工况下的坡后地下水位变化及支护结构力学响应。计算结果表明：排水孔堵塞对坡后地下水位影响显著,坡内位移整体变化不大,坡趾位置岩体变形最大;坡体锚杆轴力明显增加,最大增长幅度达到45%。对于布设深层排水孔的岩质高边坡,排水孔堵塞后边坡支护结构的位移变化明显,对支护结构的影响不容忽视,尤其体现在坡趾剪出口位置。此外,排水孔接近完全堵塞时,边坡安全系数显著降低。提出了以框架式格构和锚杆共同作为支护体系的高边坡处理措施,即下部边坡加强格构支护强度,上部边坡增加锚杆锚固长度。