武汉地区岩溶对桩基承载力影响数值模拟研究

A study of the effect of karst on the bearing capacity of pile foundation in Wuhan district based on numerical simulation

武汉地区覆盖型岩溶发育较为广泛,给桩基础的应用带来不利影响。文章采用ANSYS有限元软件进行了正交数值模拟试验。通过逐一改变溶洞高度、顶板厚度、顶板跨度和岩体强度四个影响因素,研究各因素对桩基承载力的影响。结果显示:桩基承载力对下伏溶洞的洞高不敏感;极限承载力对顶板厚度较敏感,其他因素不变时,极限承载力随顶板厚度增加而增加;极限承载力对洞跨较为敏感,其他因素不变时,极限承载力随洞跨增加而减小;极限承载力对顶板岩体的力学参数较为敏感,其他因素不变时,极限承载力随弹性模量提高而增大。实际工程中,对于坚硬完整的或较完整的岩体,顶板厚度至少为二倍桩径,桩端宜进入中风化岩体。

The covered karst occuring widely in the Wuhan district seriously influences the application of pile foundation. This paper simulates a series of orthogonal experiments by using the ANSYS finite element software. To examine the effect of influencing factors on the bearing capacity of pile foundation in the karst area,this paper changes the height of karst cave,the thickness of roof,the width of karst cave and the rock mass strength by controlling variables. The results show that the bearing capacity of pile foundation is not sensitive to the height of karst cave. The bearing capacity of pile foundation is sensitive to the thickness of roof,and increases apparently as the roof becomes thicker when other factors keep in constant. The bearing capacity of pile foundation is more sensitive to the width of karst cave,and grows plainly as the cave becomes wider when other factors keep in constant. The bearing capacity of pile foundation is more sensitive to the rock mass strength,and rises rapidly as the rock mass strength becomes higher when other factors keep in constant.In practical engineering,the thickness of the roof should be 2 times the pile diameter at least if the roof is hard and complete or fairly complete,and medium weathered rock is strong enough for the pile tip.