岩溶区桥基下伏溶腔顶板安全厚度分析

Analysis of Safe Roof Thickness of Karst Cavity under Bridge Load in Karst Area

研究目的:以某客运专线岩溶区大桥为例,结合溶腔实际空间分布形态,对桥基荷载作用下溶腔岩体应力特征进行三维有限元分析,确定溶腔顶板的安全厚度。研究结果可为岩溶地区高速铁路、客运专线桥梁基础设计提供参考。研究结论:溶腔顶板厚度为30m和25m时,桥基附近岩体安全系数均在1.2以上,溶腔顶板安全系数在1.3以上,溶腔顶板是安全的;溶腔顶板厚度20m时,溶腔洞周局部岩体安全系数约1.1,溶腔顶板基本是安全的,但岩体强度储备不足。本工程桥基荷载作用下溶腔顶板最小安全厚度约为20m,对应基础最大埋深为13m;基础设计埋深为8m,溶腔顶板是安全的。

Research purposes：Taking a bridge on one passenger dedicated line in karst area as an example and combining with the distribution pattern of the real space of karst cavity,the stress characteristics of rock mass under bridge load was analyzed with three-dimensional finite element to determine the safe roof thickness of karst cavity.The results could provide the reference to the design of bridge foundation of high speed railway in karst area.Research conclusions：The safety coefficient of rock mass nearby the bridge foundation was over 1.2 and the safety coefficient of the roof of the karst cavity was over 1.3 when the safe roof thickness of karst cavity was 30 m or 25 m,so the roof of karst cavity was in safety.The safety coefficient of local rock mass around the karst cavity was about 1.1 when the safe roof thickness of karst cavity was 20 m,so the roof of the karst cavity was basically in safety,but the stored strength of rock mass was insufficient.The minimum safe roof thickness of karst cavity under bridge load presented in this paper was about 20 m and the maximum buried depth of bridge foundation was 13 m while the design buried depth was 8m,therefore,the roof of karst cavity was in safety.