支护结构平移时的坑中坑被动区土拱效应分析

坑中坑式基坑由于相关设计规范对一些关键参数的确定缺乏明确规定,有时因为对内坑开挖引起外坑支护结构土压力的变化估计不足而引发一些工程事故;现有研究成果在坑中坑工程的被动区土压力分析中,没有考虑岩土工程中广泛存在的土拱效应,土压力分析不准确。通过合理的假定,对内坑支撑刚度较大且距离外坑支护结构较近的情况下,建立了无黏性土被动土压力力学模型,分析得到了坑间土体在极限应力条件下基于土拱效应的水平土压力系数和主应力旋转角;利用水平分层分析法求解得到了考虑土拱效应的被动土压力分布、合力大小、合力作用点位置等表达式。通过算例与经典土压力理论分析成果比较表明,研究成果能更好地反映实际土压力分布。

Analysis of Soil Arching Effects in Pit-in-pit Passive Zone as Supporting Structure Parallel Movement

Due to the lack of a clear definition for some key parameters in engineering design specifications, the wrong estimation of earth pressure produced by the inner pit excavation often results in accidents. The existing researches of  earth pressure in the passive zone of pit-in-pit have not considered the soil arching effects, which widely exist in geotechnical engineering. As a result, an accurate analysis on passive earth pressure is impossible. In this paper, an earth pressure mechanical model of cohesionless soil is established by presuming the inner pit support structure with large stiffness and very close to the outer pit support structure. Coefficient of earth pressures and the large principal stress rotation angle are obtained by analysing the horizontal earth pressure between two pit supporting structures at a limit state based on soil arching effects, and then the theoretical formulae and the force point are obtained. The case study shows that this method can better reflect the actual situation by analysing horizontal differential elements comparing to the classical earth pressure theory.