隧道设计中不同抗剪强度指标对竖向土压力的影响研究

Research on the effect of different shear strength to vertical earth pressure in tunnel design

考虑未来北京地铁的埋深将向更深层发展,在地铁设计时,竖向土压力的计算则必须采用松弛土压力理论。目前常用的全覆土、比尔鲍曼、太沙基、普氏和谢家烋等土压力理论都有其适用条件,其中后四种理论的计算参数都涉及土的抗剪强度指标,而土的抗剪强度指标由于试验条件不同,有天然快剪、CU、CD、UU等多种,因此,在计算竖向土压力时,选用不同的试验指标将会得到不同的土压力值。本文首先分析了抗剪强度指标对竖向土压力的影响,明确比尔鲍曼、太沙基、普氏和谢家烋等公式受强度指标的影响程度,再通过搜集和归纳北京西部和东部地区三种典型地层的不同试验的强度指标,包括天然快剪、CU和UU,来分析上述指标对竖向土压力的影响及其分布规律,从而为地铁设计中竖向土压力计算时选用合适的强度指标,得到合理的计算结果提供参考和依据。

Considering subway burial depth are furthermore deep in Beijing in the future,when subway are designed,vertical earth pressure must use relaxation pressure method.Now the frequent method,such as the equation of Whole-Soil-Column,Bierbaumer,Terzaghi,M.M.Promojiyfakonov and Xie jiaxiu etc.,have their applicable conditions,and most of which are relational with shear strength.But shear strength is different with test condition,having the test results of natural fast shear,CU,CD UU,So different test results used will have effect on the vertical earth pressure.There is the first in the article that the effect of shear strength results to earth pressure is analyzed,the affected extent of above formulas is defined.Hereafter,different shear strength results of three typical strata in west and east of Beijing are collected and concluded,including the test results of natural fast shear,CU UU,to analyze the effect of the results to vertical earth pressure and distribution rules,in order to use the right result to calculate the earth pressure and provide the reference to the tunnel design.