桩前溶洞对抗滑桩嵌固端稳定性影响物理模型试验研究

Experimental study on the effect of the elliptical karst cave in front of the pile on the stability of the fixed end of the sliding pile

随着抗滑桩在工程中的大量运用,岩溶区抗滑桩嵌固端稳定性问题日益突出。当抗滑桩桩前存在溶洞时,溶洞在水平荷载下可能会发生变形,导致抗滑桩嵌固端失去稳定性。本文基于相似模型理论,建立了抗滑桩嵌岩段桩前存在两种不同形状溶洞(长轴方向水平和长轴方向竖直)试验模型。利用水平加载试验,针对椭圆形桩前溶洞对抗滑桩嵌固端的稳定性影响进行了研究,获得以下相关结论:溶洞长轴方向为竖直的试验模型嵌岩体变形分为弹性变形、裂纹稳定扩展及加速扩展三个阶段,加载到破坏荷载时溶洞顶板产生隆起破坏,最终形成的顶板处破坏断面与水平方向成45°左右;桩前溶洞长轴方向为水平的试验模型在达到溶洞长轴方向为竖直的模型破坏荷载增大一级荷载时,嵌固端保持整体稳定;相比于横长轴溶洞,纵长轴溶洞的存在更显著的降低了抗滑桩嵌固端的承载力,且溶洞顶板厚度越小,对抗滑桩嵌固端承载力影响越大,破坏形式为溶洞顶板受压破坏;基于极限平衡法,提出了桩前存在溶洞时嵌固端承载力验算方法,并对验算方法进行了验证。

With the vigorous advancement of China's infrastructure construction and increasing attention to the prevention and control of geological disasters,a large number of horizontal load-bearing anti-slide piles have been set up in karst areas.Due to the existence of karst phenomena such as karst caves,the load-bearing properties of such anti-slide piles have their particularity.Studies on these properties are rarely carried out at home and abroad,which leaves many technical problems to be solved urgently in the arrangement of anti-slide piles in karst areas.When there is a karst cave in front of the anti-slide pile,the karst cave may be deformed under horizontal load,causing the embedded end of the anti-slide pile to lose stability.Based on the indoor similar model test and theoreti⁃cal research,this paper establishes two different shapes of caves(horizontal in the longitudinal direction and verti⁃cal in the longitudinal direction)in front of the rock-socketed section of the anti-slide pile.Using horizontal loading tests,the influence of the karst cave in front of the elliptical pile on the stability of the anti-sliding pile with embed⁃ded end was examined.Results show that the deformation of the rock-socketed body of the test model with the ver⁃tical longitudinal direction of the karst cave can be divided into three stages,elastic deformation,steady crack ex⁃pansion and accelerated crack expansion.When loaded to the failure limit,the roof of the cave will be uplifted and destroyed,and the fracture section of the finally formed roof will be about 45°from the horizontal.In the test mod⁃el with the long axis of the cave in front of the pile,when the failure load of the vertical model increases one degree of load,the embedded end remains stable as a whole.Compared with the horizontal and long axis karst caves,the existence of the longitudinal axis karst caves significantly reduces the bearing capacity of the embedded end of the anti-slide pile.In addition,the smaller the thickness of the cave roof is,the greater the impact on the bearing capaci⁃ty of the anchored end of the anti-slide pile becomes,and the failure form is the collapse of the cave roof under compression.Under the condition that there is a karst cave in front of the pile,the calculation method of the ultimate bearing capacity of the anti-sliding pile in the embedded-solid section of the anti-sliding pile is verified based on the rigid limit equilibrium theory,which can be used as a reference for the design of anti-sliding piles in karst areas.