地基回弹变形计算若干问题探讨  

Discussion on some issues of resilient deformation calculation

作　　者：王曙光 李钦锐 李建民 Wang Shuguang;Li Qinrui;Li Jianmin(China Academy of Building Research,Beijing 100013,China;Disaster Prevention Research Center,Ministry of Housing and Urban-Rural Development,Beijing 100013,China)

机构地区：[1]中国建筑科学研究院有限公司,北京100013 [2]住房和城乡建设部防灾研究中心,北京100013

出　　处：《土木工程学报》2020年第8期108-115,共8页China Civil Engineering Journal

摘　　要：《建筑地基基础设计规范》(GB50007—2011)规定采用分层总和法计算地基回弹变形,并给出计算公式。回弹模量的选取和回弹变形计算深度的确定直接影响到计算精度,但是实际应用时很难准确得到计算需要的回弹模量和回弹变形计算深度。通过对不同地区、不同土性的土样的回弹试验结果进行分析发现:土在完全卸荷时的回弹模量Ec0与初始卸荷应力p近似呈线性关系;不同初始卸荷应力下,土的Ec/Ec0-R曲线可以采用对数曲线进行拟合。根据这些规律,提出回弹模量确定方法,按照该方法可得到同一土层不同初始卸荷应力p、不同卸荷比R对应的回弹模量Ec,并对土的回弹试验方法和数量提出建议。此方法解决了采用地基规范方法计算回弹变形时的回弹模量取值的问题。回弹变形计算深度的确定可以采用地基规范规定的应变比方法。对于基底以下土层较均匀时,提出可采用应力比的方法确定回弹变形计算深度,采用卸荷比R为0.4作为确定回弹变形计算深度的标准,提出均质土地基回弹变形计算深度系数表。通过算例证明:对于均质土地基,采用该方法确定的地基回弹变形计算深度与应变比方法得到的计算深度基本一致。According to Code for Design of Building Foundation GB50007—2011,the layer-wise summation method can be used to calculate the resilient deformation,and the corresponding calculation formula is provided.Since it is difficult to determine the resilient modulus and the calculation depth in practical applications,which directly affect the accuracy of calculation.By analyzing resilient test results of samples from different regions and with different kind of soils,it is found that the resilient modulus of complete unloading(Ec0)has approximately linear relationship with the initial unloading pressure(p);the logarithmic curves can be used to fit the curves of Ec/Ec0-R under different initial unloading pressures.Besed on these rules,the method of determining resilient modulus is put forward,which can be used to determine resilient modulus of the same soil layer under different initial unloading pressures and different unloading ratio.Furthermore,some suggestions are given on the procedure and the quantity of resilient tests.Hence,the problem on taking the resilient modulus in Code’s the resilient deformation calcalation can be resolved.The calculation depth for resilient deformation can also be determined by referring to the stain ratio method suggested in the Code for Design of Building Foundation GB50007—2011.When the soil beneath foundation is relatively homogeneous,the stress ratio method may be employed to determine the calculation depth of resilient deformation.The unloading ratio of 0.4 may be used to determine the calculation depth which can be taken as a criterion,and then a coefficient table for the calculation depth is given.Based on some examples,it is observed for the homogeneous subsoil that the calculation depth of resilient deformation determined by the stress ratio method agrees well with that determined by the stain ratio method.

关 键 词：回弹变形 回弹模量 变形计算深度 卸荷比 

分 类 号：TU470[建筑科学—结构工程]