摘要
作者对《建筑地基基础设计规范》(GB 50007-2011)、《建筑基坑支护技术规程》(JGJ 120-2012)以及最近改版的一些地方基坑规范中的一些问题进行了系列讨论。本文为第一部分,主要是讨论在基坑设计中应采用什么强度指标。本文作者认为对于粗粒土使用有效应力强度指标;对于黏性土一般采用固结不排水(CU)强度指标较为合理,用不排水(UU)强度指标水土合算计算水土压力符合有效应力原理,但由于cu是随深度增加的,难以准确地计算。UU强度指标在验算坑底隆起和计算超载引起的侧向压力时,是适用的。本文还对一些规范中提出的"在有效压力下预固结的不排水强度指标"提出了质疑,认为对于欠固结土应对其固结不排水强度进行折减;对于"施工挖土速度慢,排水条件好"的基坑,其黏性土应使用有效应力指标,而不是固结不排水强度指标;在软土地基中,计算坑壁地面上的施工超载引起的土压力与验算坑底隆起时,一律用固结不排水强度指标计算土压力和进行稳定分析是错误的。
Some questions and suggestions are proposed for ＂Code for Design of Building Foundation＂（GB 50007-2011）,＂Technical Specification for Retaining and Protection of Building Foundation Excavation＂（JGJ120-2012） and other local codes which are promulgated recently.This paper is the first part of a series of discussion papers.The application of strength parameters of soil in the calculation of earth pressure and stability analysis is discussed and some suggestions are as follows：（1） for granular soil,the CD strength parameters are applicable;（2） for cohesive soil,the CU strength parameters are reasonable.The use of UU strength conforms to the principal of effective stress,but the correct determination of cu value is difficult which increases with the depth;（3） the pre-consolidated UU strength parameters under effective gravity stress is questionable because it is confused in concept and inapplicable in practice;（4） for normal consolidated clay in pit engineering,under slow construction and good drained conditions,rather than CU strength parameters,CD strength parameters is suitable;（5） in soft clay,the calculation of the earth pressure induced by construction overcharge on ground surface and the checking of the heaving of pit bottom should be calculated by using of UU strength parameters not by CU strength parameters.
出处
《工程勘察》
2013年第9期1-6,共6页
Geotechnical Investigation & Surveying
基金
重点基础研究发展计划(973)项目(2010CB732103)
关键词
基坑工程
强度指标
地面超载
坑底隆起
foundation pit engineering
strength parameter
overcharge
heaving of pit bottom
