降雨是导致边坡地质灾害的主要因素，而雨水渗流作用则是灾害发生的直接原因。由于雨水的作用，结构面强度逐渐降低，导致其切割出的块体稳定性下降，使块体产生塌落或滑动，最终引起边坡地质灾害的发生。由连续强降雨作用导致的崩塌、滑坡等地质灾害，对工程建设和人民生命财产的安全构成了严重的威胁，因此研究降雨作用下岩质边坡块体稳定性具有重要的理论意义及工程研究价值。为研究降雨对块体稳定性的影响，本文以云南省昭通市鲁甸县某边坡工程为研究背景，利用离散元软件进行数值模拟试验建立结构面强度劣化公式，基于坐标投影法提出不同含水率条件下的块体稳定性计算公式，采用有限元法分析边坡块体稳定性并给出块体失稳判据，通过以上研究对降雨作用下岩质边坡块体稳定进行评价。具体内容如下：

（1）采用离散元法进行直剪试验数值模拟，研究不同含水率条件的岩石试样结构面强度变化。采用回归分析法研究结构面抗剪强度参数和孔隙水压力随含水率变化的劣化规律，结合有效应力强度准则，建立结构面抗剪强度随不同含水率变化的劣化数学模型。

（2）基于坐标投影原理，结合渗流-应力耦合作用下块体的受力模型，提出考虑不同含水率对结构面强度劣化的块体稳定性系数计算公式，实际工程表明提出的块体稳定性理论分析公式合理可行。

（3）采用有限元法研究岩质边坡块体在不同降雨条件下的应力、变形及稳定系数的变化。分析发现：降雨强度较大时，边坡孔隙水压力快速增大，随着降雨历时增加，雨水逐渐向下入渗，对边坡较深处应力影响较大；块体位移及稳定系数随降雨强度及降雨历时的增加分别呈现逐渐增大和不断减小的趋势。

（4）采用分项系数的极限状态法分析可能产生滑动块体的稳定系数变化规律；基于降雨过程中块体稳定性系数随降雨强度和降雨时长变化的函数曲线，提出降雨作用下岩质边坡块体失稳判据，为边坡工程灾害防治提供评价方法，具有重要的参考意义。

Rainfall is the main factor leading to geological disasters of slope, and the seepage of rainwater is the direct cause of disasters. Due to the effect of rain, the strength of the structural plane gradually decreases, resulting in the stability of the block cut out of the decline, so that the block collapse or slide, and eventually cause the occurrence of geological disasters of the slope. Geological disasters such as collapse and landslide caused by continuous heavy rainfall pose a serious threat to engineering construction and the safety of people's life and property. Therefore, it is of great theoretical significance and engineering research value to study the stability of rock slope block under the action of rainfall. To study the effect of rainfall on block stability, taking zhaotong city in yunnan province ludian a slope project as the research background, using the discrete element software numerical simulation experiment was carried out to establish the intensity of structural plane degradation formula, based on the coordinate projection method is put forward under the condition of different moisture content block stability calculation formula of the finite element method analysis of block stability of slope instability criterion and block is given, Based on the above research, the stability of rock slope block under rainfall is evaluated. The details are as follows:

(1) The discrete element method was used to conduct numerical simulation of direct shear test to study the changes of structural plane strength of rock samples under different water content conditions. Regression analysis method was used to study the deterioration law of shear strength parameters and pore water pressure with water content. Combined with the effective stress intensity criterion, the deterioration mathematical model of shear strength with different water content was established.

(2) Based on the principle of coordinate projection and combined with the force model of block under the coupled action of seepage and stress, the calculation formula of block stability coefficient considering the strength deterioration of structural plane caused by different water content is proposed. The practical project shows that the theoretical analysis formula of block stability is reasonable and feasible.

(3) The finite element method is used to study the changes of stress, deformation and stability coefficient of rock slope block under different rainfall conditions. The results show that the pore water pressure increases rapidly when the rainfall intensity is high. With the increase of rainfall duration, the rainwater gradually infiltrates downward, which has a great influence on the stress in the deeper part of the slope. With the increase of rainfall intensity and rainfall duration, the block position shift and stability coefficient gradually increased and decreased, respectively.

(4) The limit state method of partial coefficient is used to analyze the variation rule of stability coefficient which may produce sliding block; Based on the function curve of block stability coefficient changing with rainfall intensity and rainfall duration in the process of rainfall, the criterion of block instability of rock slope under rainfall action is proposed, which provides an evaluation method for slope engineering disaster prevention and control, and has important reference significance.

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