【摘要】 珠三角地区的软土具有含水量大、压缩性高、承载力低等特性,这对基坑工程的设计和施工都提出了更高的要求,因此软土深基坑在复杂环境下的支护设计已成为岩土工程的一个新课题。针对软土基坑的特殊性,本文探讨软土基坑设计的4个关键问题:(1)采用增量法分析支护结构的受力和变形过程;(2)考虑锚杆或锚索等的预应力作用时,预应力使基坑主动侧的土体受压,因此主动侧土体应该等效成弹簧,弹簧是否参与作用要根据结构的位移来判断;(3)当放坡开挖存在软弱下卧层地基时,不仅要验算其整体稳定性,还应验算地基的稳定性或承载力;(4)针对双排桩支护结构的受力和变形的研究,还存在许多问题有待进一步完善,结合具体工程,提出双排桩简化计算方法。很多软基工程事故也说明,这几个关键问题如果没有被考虑和重视,则基坑存在安全隐患。最后,以2个软土深基坑设计为案例,以上述的几个关键问题的解决方法为理论支撑,验证其合理性,并详细分析软土深基坑采用多种支护形式的设计方案,为类似工程提供指导。更多还原

【Abstract】 The soft soil in the Pearl River Delta area has the features of high water content,high compressibility and low carrying capacity,etc.,which has put forward more stricter requirements for the design and construction of foundation pit project.Therefore,the supporting design under complicated environment for deep foundation pit on soft soil has become a new topic for geotechnical engineering.According to the particularities of the soft soil foundation pit,four key problems during the foundation design of soft soil foundation pit are discussed:(1) The force and deformation processes of the supporting structure are analyzed by the incremental method.(2) When considering the impact of the prestresses of the pit anchoring bolts and anchoring cables,the prestress leads the soil on the positive side of the foundation to suffer pressure.Therefore,the soil mass at the positive side shall be equivalent to earth spring.As for whether the earth spring has participated in the impact shall be judged by the displacement of the earth spring.(3) When the soft and weak earth foundation existing during the slope cutting,it is not only need to verify the overall stability of the foundation pit,but also need to verify the stability and carrying capacity of the earth foundation.(4) There are many issues about the forcing and deformation of double-row piles supporting structure needing to be studied further.With the specific engineering,the simplified calculation method of double-row piles is proposed.Many soft foundation engineering accidents have also illuminated that the foundation will have potential hazard risk if the above four key problems have not been thoroughly considered.Finally,based on the design of soft soil deep foundation pit,taking the solving method of the above four key problems as the theoretical support,the rationality is verified;and the common design scheme for adopting multi-supporting techniques for soft soil deep foundation pits are analyzed in detail,so as to provide some guidances for other similar projects.更多还原