外坑支护结构转动时坑间被动区土拱效应分析

为研究支护结构受力与变形特点,分析了坑中坑式基坑坑间区土体的成拱作用。当外坑支护结构绕底端转动时,利用土拱效应分析方法,推导了被动土压力表达式;定义了内外坑支护结构相对位移比,以此描述内坑支护结构位移对外坑支护结构被动土压力的影响,得到土压力呈非线性分布。工程算例对比分析表明土压力分析方法能更好地反映土拱效应及坑间距对作用在外坑支护结构上土压力的影响,以此土压力值用于基坑支护结构设计相比采用库仑理论计算值偏于安全;当内坑支护结构不发生位移时,坑间距越小、支护结构相对位移比越大,外坑支护结构所受到的被动土压力愈大,说明提高内坑支护结构支撑刚度有利于控制外坑支护结构的变形。研究成果对分析基抗支护结构安全问题,具有一定的参考价值。

Soil Arching Effect in the Passive Zone Between Internal Pit and External Pit When the Outer Supporting Structure Rotates

The soil arching effect in the passive zone between the internal pit and external foundation pit was ana-lysed based on the stress and deformation features of supporting structure.A formula of passive soil pressure is es-tablished by using the theory of soil arching effect when the supporting structure of the external pit rotates around the bottom.A conception of the relative displacement ratio is put forward to describe the change of earth pressure in the external pit when the structure of the internal pit has displacement.The calculated earth pressure is nonlinear. The calculation results of engineering example prove that the method in this research could better reflect the impact of soil arching effect and pit-to-pit distance on earth pressure than classical methods.It also shows that this new method is safer than Coulomb’s earth theory when designing the supporting structures.When there is no displace-ment of the internal pit supporting,the smaller distance between two pits,the bigger relative displacement ratio of supporting structures and the bigger passive earth pressure will be,which means that improving the interior support-ing stiffness is beneficial to controlling the deformation of the external pit supporting.