降雨条件下黄土深路堑边坡稳定性分析及加固技术研究

发布时间：2018-06-04 12:41

本文选题：非饱和黄土 + 饱和-非饱和渗流分析　；参考：《兰州交通大学》2017年硕士论文

【摘要】：常年处于干旱地区的黄土通常都是非饱和土,在降雨条件下,由于雨水的入渗往往会导致边坡失稳。究其原因,降雨条件下,黄土边坡表层土体含水量增大,基质吸力逐渐消散,进而引起非饱和黄土抗剪强度减小,从而引发滑坡。降雨是引发滑坡的主要因素,降雨条件下边坡稳定性分析早已成为岩土界的重要课题。研究降雨过程中边坡水分场及稳定性随时间、空间的动态变化对边坡稳定性研究和滑坡预测有重要意义。文章以饱和—非饱和渗流理论为基础,研究降雨条件下边坡水分场的变化规律,分析了不同降雨强度、降雨持续时间、边坡坡高、坡度以及黄土节理对边坡表层土体含水量和孔隙水压力的影响,然后基于瞬态渗流分析结果,结合极限平衡法对边坡稳定性的动态变化过程进行分析,最后对边坡进行了锚杆抗滑桩加固设计,以及对加固后边坡的稳定性进行计算。具体的研究工作如下:(1)归纳总结了饱和—非饱和渗流基础理论。以达西定律和能量守恒定律为基础,归纳总结了饱和—非饱和渗流微分方程以及微分方程的定解条件,用以后续有限元数值计算的基础。(2)考虑降雨条件,进行了非饱和黄土瞬态渗流计算,得到了不同降雨强度、降雨持续时间、边坡坡高、坡度以及黄土节理存在下边坡土体水分场的变化规律,即不同降雨条件对非饱和黄土本体积含水量、孔隙水压力的影响。由计算结果得到:降雨条件下,由于雨水入渗主要影响边坡的表层土体,主要表现为土体含水量增加,出现暂态饱和区,基质吸力(负孔隙水压力)减小;此外,尽管整个边坡表层土体整体变化规律是含水量增加,基质吸力减小,但土体含水量和基质吸力的变化速率和变化幅度因土体位置而异,越靠近坡脚处的表层土体含水量和孔隙水压力变化的速率和幅度越大,坡顶处表层土体含水量和孔隙水压力变化速度和幅度较小。坡脚处最开始土体出现暂态饱和区,随着降雨时间增大,该区沿坡面向上延伸,最终整个边坡表层土体都出现饱和区。降雨过程中,当考虑黄土节理存在时,雨水的入渗速率和深度明显增大,边坡表层土体出现饱和区域时间提早。(3)基于饱和—非饱和渗流计算结果分析了降雨过程中黄土深路堑边坡的稳定安全系数的动态变化。将渗流计算得到的结果和非饱和土抗剪强度理论相结合,运用极限平衡法计算不同降雨强度和降雨持续时间下边坡的稳定安全系数。由计算结果可以看到:降雨条件不同边坡稳定安全系数值不同,同一降雨强度下,稳定安全系数随着时间的增加而减小;相同降雨持时,雨强大,系数越小;边坡高度增大时,边坡表层土体含水量的最大值大致相同,但是雨水的入渗深度则随着坡度的增大而增大,因此受降雨影响的土体去增大了,抗剪强度减小的土体区域增大,导致边坡稳定安全系数有所减小;边坡坡度增大时,边坡稳定安全系数小;当考虑节理存在时,降雨过程中,存在节理区的边坡稳定安全系数减小的幅度逐渐降低,这是由于降雨初期雨水入渗速度快,边坡表层土体含水量增大的速率快,降雨后期土体含水量增大速率较缓,降雨3d后边坡表层土体达到饱和,而均质边坡土体含水量增大幅度差异相较之下没那么明显,因而边坡稳定安全系数增大速率也没明显变化,降雨3d后边坡土体未达到饱和状态。(4)对边坡采用锚杆抗滑桩加固方案的比选以及对支护后边坡稳定安全系数进行了计算。由计算结果可知:当锚杆按与水平面成15°夹角布置时得到的边坡稳定安全系数最大;锚杆加固坡面能够较好的提高边坡的稳定,虽然加固后的边坡稳定安全系数同样会随着降雨而有所减小,但降雨3d后边坡的稳定安全系数依然较大,因而可以保证边坡有较高的稳定性。
[Abstract]:In the arid area, the loess is usually unsaturated soil. Under rainfall conditions, the infiltration of rainwater often leads to the instability of the slope. The reason is that under the conditions of rainfall, the soil water content in the surface of the loess slope increases and the matrix suction gradually dissipates, which causes the decrease of the shear strength of unsaturated loess, thus triggering the landslide. The main factor of landslides, the analysis of slope stability under rainfall has already become an important subject of rock and soil. It is of great significance to study the dynamic changes of slope water field and stability with time and space in the process of rainfall. The paper is based on the theory of saturated unsaturated seepage, and studies the conditions of rainfall. The influence of different rainfall intensity, rainfall duration, slope height, slope and loess joint on the soil water content and pore water pressure on the surface of the slope is analyzed. Then based on the transient seepage analysis results, the dynamic change process of slope stability is analyzed with the limit equilibrium method. The slope is designed by anchor anti slide pile and the stability of the reinforced slope is calculated. The specific research work is as follows: (1) the basic theory of saturated unsaturated seepage is summarized. Based on Darcy's law and the law of conservation of energy, the differential equation of saturated unsaturated seepage and the definite solution of differential equation are summed up. The basis of the subsequent finite element numerical calculation. (2) considering the conditions of rainfall, the transient seepage calculation of unsaturated loess is carried out. The variation rules of different rainfall intensity, rainfall duration, slope height, slope and loess joints under the existence of soil water are obtained, that is, the volume water content of unsaturated loess with different rainfall conditions The effect of pore water pressure. It is obtained from the calculation results: under the condition of rainfall, the main performance of the surface soil of the slope is the increase of the soil water content, the transient saturation area and the matrix suction (negative pore water pressure) decrease because of the rainfall infiltration. In addition, although the whole change law of the whole soil surface is the increase of water content, the substrate is absorbed. The change rate and amplitude of soil water content and matrix suction vary with the soil position. The greater the rate and amplitude of soil water content and pore water pressure change near the foot of the slope, the change speed and amplitude of soil water content and pore water pressure at the top of the slope is small. In the saturated area, with the increase of rainfall time, the area extends along the slope, and eventually the whole slope of the slope is saturated. In the process of rainfall, when the Loess joints are considered, the infiltration rate and depth of the rainwater increase obviously, and the saturated area of the slope surface soil appears early. (3) the calculation results based on saturated unsaturated seepage are divided. The dynamic change of the stability safety factor of the Loess deep cutting slope is analyzed. The result of seepage calculation and the theory of unsaturated soil shear strength are combined to calculate the stability safety factor of the slope under the different rainfall intensity and rainfall duration by the limit equilibrium method. The stability safety factor of slope stability is different, and the stability safety coefficient decreases with the increase of time. When the same rainfall is held, the rain is strong and the coefficient is smaller. When the slope height increases, the maximum water content of the soil surface is approximately the same, but the infiltration depth of the rain is increased with the increase of the slope, so the rain shadow is reduced. The soil area is increased, the soil area of the shear strength decreases and the slope stability safety factor decreases. When the slope increases, the slope stability safety factor is small. When the joints exist, the slope stability safety coefficient decreases gradually during the rainfall process, which is due to the initial rainfall. The rate of soil moisture content in the surface of the slope is faster, the soil moisture content increases slowly in the later period of rainfall, and the soil water content of the slope is saturated after 3D rainfall, and the soil moisture content of the slope is not so obvious as that in the same slope, so the increase rate of the slope stability safety coefficient does not change obviously. After the rainfall, the rainfall is 3D. The slope soil soil is not saturated. (4) the comparison and selection of the anchor anti slide pile for the slope and the stability safety factor of the slope after the support are calculated. The results show that the stability safety factor of the slope is maximum when the bolt is arranged in the angle of 15 degrees with the horizontal plane, and the slope surface can improve the slope better. The stability of the slope is also stable, although the stability safety factor of the slope will decrease with the rainfall, but the stability safety factor of the slope is still large after the rainfall of 3D, so it can guarantee the high stability of the slope.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.14

【参考文献】