主动区溶洞对桩锚支护基坑稳定性的影响

为了研究存在最危险滑移面时主动区溶洞对桩锚支护基坑稳定性的影响,首先运用FLAC3D软件模拟出没有溶洞时基坑最危险滑移面的位置,然后再分别模拟出主动区不同位置、不同大小的溶洞对桩体最大水平位移和弯矩、锚索最大轴力以及地表最大沉降位移的影响规律,最后提出主动区溶洞的处理方法.结果表明:最危险滑移面的剪出口出现在强风化石灰岩与中风化石灰岩的分界线处,最危险滑移面为与基坑内壁夹角约45.方向的弧形面;在同一溶洞中心埋深下,越靠近最危险滑移面的溶洞对基坑稳定性影响越大,当溶洞中心埋深不同但都在最危险滑移面上时,越靠近剪出口的溶洞对基坑稳定性影响越大;溶洞边长越大,对基坑稳定性影响越大,当边长大于等于2 m时,需要对溶洞进行处理,且利用增大锚索预应力的处理方法对主动区溶洞的处理效果比较明显.可见,考虑最危险滑移面的不利影响对研究主动区溶洞对桩锚支护基坑稳定性的影响是必要的.

Study on The Influence of Karst Cave in Active Zone on Stability of Pile-Anchor Supporting Foundation Pit

In order to study the influence of the karst cave in the active zone on the stability of the pile-anchor-supported foundation pit when there is the most dangerous slip surface, FLAC3D software is first used to simulate the position of the most dangerous slip surface of the foundation pit when there is no karst cave, and then the active zone is simulated separately The influence laws of karst caves of different positions and sizes on the maximum horizontal displacement and bending moment of the pile, the maximum axial force of the anchor cable and the maximum settlement and displacement of the ground surface. Finally, the treatment method of the karst cave in the active zone is proposed. The results are listed as follows. First of all, the cutting outlet of the most dangerous slip surface appears at the boundary between strongly weathered limestone and moderately weathered limestone, and the most dangerous slip surface is a curved surface with an angle of about 45° to the inner wall of the foundation pit. Secondly, in the same cave center under the buried depth, the cavern closer to the most dangerous slip surface has a greater impact on the stability of the foundation pit. And when the cave center has different buried depths but all on the most dangerous slip surface, the cave closer to the shear outlet has a greater impact on the stability of the foundation pit. Thirdly, the larger the side length of the karst cave, the greater the impact on the stability of the foundation pit. And when the side length is greater than or equal to 2 m, the karst cave needs to be treated, and the treatment method of increasing the anchor cable prestress is more effective in treating the karst cave in the active zone. It is concluded that it is necessary to consider the adverse effects of the most dangerous slip surface to study the influence of karst caves in the active zone on the stability of pile-anchor foundation pits.