考虑降雨条件陕北Q_(2)黄土斜坡稳定性的非线性劣化研究

Nonlinear degradation of stability of Q_(2) loess slopes in northern Shaanxi considering rainfall conditions

降雨致灾是陕北黄土斜坡最常见的灾害之一,揭示降雨对黄土斜坡稳定性影响特征有利于预防滑坡灾害的发生。通过一系列室内试验研究了降雨条件下陕北Q_(2)黄土的力学特性变化特征,并结合数值模拟分析了其对陕北黄土斜坡稳定性的影响。首先设计干湿循环试验(循环路径和次数)以模拟降雨条件(如强度、频次等);其次通过三轴剪切试验获取陕北Q_(2)黄土的力学性质的变化规律;最后以陕北地区某黄土斜坡为例,利用有限元计算并分析不同降雨条件下斜坡安全系数和塑性区的变化特征。结果表明:(1)干湿循环作用后Q_(2)黄土的抗剪强度存在非线性劣化特征。当干湿循环次数超过一定范围后,黄土物理力学性质参数劣化的边际效应减弱,并趋于稳定。(2)降雨作用下黄土斜坡的稳定性呈现出随着降雨频次或降雨强度的增加而降低的趋势。(3)Q_(2)黄土斜坡的塑性区范围随着Q_(2)黄土力学性能的不断劣化而增大,体现了降雨条件对黄土斜坡稳定性影响的非线性特征。研究结果为降雨型滑坡预防提供参考。

[Objective]Rainfall disasters are one of the most common disasters on loess slopes in northern Shaanxi,and revealing the effects of rainfall on loess slope stability is beneficial for preventing and controlling such disasters.[Methods]This research studied the mechanical properties of Q_(2) loess in northern Shaanxi under rainfall conditions through a series of tests.Combined with numerical simulation technology,the influence of these changes on the stability of loess slopes in northern Shaanxi was analyzed.Firstly,the drying-wetting cycles test(cyclic path and the number of cycles)was designed to simulate rainfall conditions(such as intensity,frequency,etc.).Secondly,a triaxial shear test was performed to obtain the variation law of the mechanical properties of the Q_(2) loess in northern Shaanxi.Finally,taking a loess slope in northern Shaanxi region as an example,finite element calculations were carried out,by which the change characteristics of the slope safety coefficients and plasticity zones under different rainfall conditions were analyzed.[Results]The results show that(1)the shear strength of Q_(2) loess after the action of drying-wetting cycles has nonlinear deterioration characteristics.When the number of drying-wetting cycles exceeds a specific range,the marginal effect of the deterioration of the physical and mechanical property parameters of loess is weakened and tends to stabilize.(2)The stability of loess slopes decreases under the effect of rainfall,and it decreases with the increase of rainfall frequency or intensity.(3)The plastic zone of Q_(2) loess slopes in northern Shaanxi increases with the continuous deterioration of the mechanical properties of the Q_(2) loess,which reveals a nonlinear characteristic of the influence of rainfall on the stability of the loess slopes.[Conclusion]The research results can provide a reference for preventing rainfall-induced landslide.