不同强度参数及水土压力计算方法对围护结构变形和内力的影响

Effect of Different Strength Parameters and Calculation Method of Soil and Water Pressure on The Deformation and Internal Force of Retaining Structure

基坑围护结构设计多采用平面竖向弹性地基梁法,但对不同土类型采用何种水土压力计算方法(分算或合算)及相应的强度参数指标仍存在争议,这些因素对围护结构变形和内力的定量影响也不甚清楚。通过在ABAQUS中建立平面竖向弹性地基梁法,分析了均质土中强度参数(黏聚力c和内摩擦角φ)和水土分算与合算对变形和内力的影响。无论是水土分算还是合算,围护结构的最大侧向位移和最大弯矩均随着c和φ的增大而减小,水土合算结果明显小于水土分算。分析了上海软土地区10个基坑工程实例,结果表明,水土分算时,采用直剪固结快剪和三轴固结不排水(CU)总应力强度参数计算得到的最大位移比CU有效应力强度参数结果平均增量约为4.8%,最大水土压力增量约为3%,最大弯矩和剪力增量约在7%~8%。水土合算时,采用直剪固结快剪强度参数计算得到的围护结构变形和内力稍大于CU总应力强度指标计算的结果,但差异平均值仅有1%~2%。同一强度参数下,水土合算的围护结构变形和内力约比水土分算结果小25%。

The plane vertical elastic beam method is widely used in the design of retaining structures.However,the calculation method of soil and water pressure for different soil types and the corresponding strength parameters is still controversial,and the quantitative effect of these factors on the deformation and internal force of the retaining structure is still unclear.By establishing plane vertical elastic beam method in ABAQUS,the influence of strength parameters(cohesion c and internal friction angleφ)and soil and water separation or combination calculation method on deformation and internal force was analyzed.The maximum lateral displacement and bending moment of the retaining structure decrease with the increase of c andφregardless of soil and water separation or combination,and the results of soil and water combination are obviously smaller than that of soil and water separation.The analysis of 10 excavations in Shanghai soft soil area shows,when using soil and water separation method,comparing with that calculated by effective stress strength parameters obtained from consolidated undrained triaxial shear test(CU),the average increment of maximum displacement calculated by direct shear test of consolidated quick shear and CU total stress strength parameters is about 4.8%,the average increment of maximum soil pressure is about 3%,and the average increment of bending moment and shear force is about 7%~8%.When using soil and water combination mehod,the deformation and internal force calculated by direct shear strength parameters are slightly larger than that of the CU total stress strength results,which is only 1%~2%.Under the same strength parameters,the deformation and internal force of the retaining structure calculated by soil and water combination method is about 25%less than that of soil and water separation.