边坡开挖支护时序有限元分析

为研究公路改扩建工程边坡稳定性的影响因素, 寻求科学的支护方法, 以柳州至南宁高速K1456+800处左侧改扩建边坡为研究对象, 利用ANSYS建立了有限元数值模型, 选择未及时支护和及时支护2种支护方式, 模拟计算了改扩建工程中6级边坡开挖过程中坡体的剪应变增量及水平、竖向位移增量; 为定量分析2种支护条件下边坡开挖过程中位移及应力的变化趋势, 选取了6个特殊节点进行监测, 主要监测内容包括测点的位移(包括水平位移和竖向位移)以及主应力(包括最大主应力和最小主应力)随开挖时步的变化情况。分析结果表明: 无论是否及时支护, 每步剪应变增量最大值均位于坡脚, 但及时支护时, 分布面积及数值较未及时支护时小, 边坡发生失稳的可能性较低; 随着开挖推进, 水平位移增量先减小后小幅增大, 竖向位移增量先急剧增大后缓慢减小, 及时支护下各测点最终位移较未及时支护情况要小; 未及时支护时最终开挖安全系数接近1.0, 及时支护后每步安全系数均大幅提高, 基本大于1.35。综上所述, 及时支护能够有效减小边坡剪切应力, 限制水平与竖向位移, 降低整体应力水平, 提高边坡安全系数, 显著改善坡体稳定性。 

Time series finite element analysis of support of slope excavation

In order to study the influence factors of slope stability of highway reconstruction and expansion project and to seek scientific support methods, the Liuzhou to Nanning Expressway K1456+800 left-hand reconstruction expansion slope was selected as the research subject, the finite element numerical model was built by using ANSYS, and two support methods were selected as the late support and timely support. The shear strain increment, horizontal and vertical displacement increments of the slope body during the excavation of 6-grade slope in the reconstruction and expansion project were simulated. For the quantitative analysis of the trend of displacement and stress during the excavation of slope under two support conditions, 6 special nodes were selected for the monitoring. The main monitoring contents include the displacement of measuring point(including the horizontal displacement and vertical displacement), and the change of principal stress(including the maximum principal stress and the minimum principal stress) with the excavation step. Analysis result shows that whether or not it is supported in time, the maximum shear strain at each step is at the foot of slope, however, the distribution area and shear strain increments of timely support are smaller than those of late support, and the probability of slope failure is low. With the excavation, the horizontal displacement increment decreases first and then increases slightly, the vertical displacement increment increases sharply first and then decreases slowly, and the final displacement of each measuring point under the timely support is smaller than the value under the late support. When it isn't supported in time, the safety factor is close to 1.0 finally. In case of timely support, the safety factor increases greatly at each step, basically greater than 1.35. As mentioned above, the timely support can reduce the shear strain of slope, limit the horizontal and vertical displacements, reduce the overall stress level, improve the safety factor, and significantly improve the stability of slope.