考虑群桩效应的加筋碎石桩复合地基沉降比计算公式

采用非线性有限元分析方法,建立加筋碎石桩群桩性能分析模型,通过模型试验从复合地基沉降和加筋体应变2方面验证了所建模型的可靠性,计算分析不同因素对地基与桩顶沉降的影响。通过单桩与群桩沉降间的关系构建了考虑群桩效应的地基沉降比计算方法。研究结果表明:竖向荷载作用下加筋碎石桩复合地基存在明显群桩效应,在加固区桩间距对群桩性能的影响显著,但对桩端土体影响不大;不同桩土模量比下中心桩桩顶沉降随荷载的变化趋势一致;同一上部荷载下加筋碎石桩能有效减少地基沉降,但当加筋体刚度大于500 kN/m时增加加筋体刚度不能有效减少加筋碎石桩复合地基沉降;桩间距与桩径比在2~4内变化时,群桩和单桩沉降比随着桩土模量比的增加呈抛物线形下降,群桩和单桩沉降比变化范围约在0.6~2.0,且桩间距与桩径比越小时群桩和单桩沉降比变化幅度越大;桩间距与桩径比在5~6内变化时,群桩和单桩沉降比几乎没有变化。

Calculation Formula of Settlement Ratio of Geosynthetic-encased Gravel Pile Composite Foundation Considering Pile-group Effect

The nonlinear finite element analysis method was used to establish the performance analysis model of geosynthetic-encased gravel pile-group.Through model test,the reliability of the model was verified from the settlement of composite foundation and the strain of reinforcement.The influence of different factors on the settlement of foundation and pile top was analyzed.Based on the relationship between the settlement of single pile and pile-group,the calculation method of foundation settlement ratio considering the effect of pile-group was established.The results show that the geosynthetic-encased gravel pile-group composite foundation has obvious pile-group effect under vertical load.In the reinforcement area,the pile spacing has a significant effect on the pile-group performance,but has little influence on the soil mass at the pile end.Under different pile-soil modulus ratio,the settlement of the top of the central pile has the same change trend with the load.Under the same upper load,geosynthetic-encased gravel pile can effectively reduce the foundation settlement,but increasing the rigidity of geosynthetic-encased body cannot effectively reduce the settlement of geosynthetic-encased gravel pile composite foundation when the rigidity of qeosynthetic-encased body is greater than 500 kN/m.When the ratio of pile spacing to pile diameter changes within 2~4,the settlement ratio of pile-group and single pile decreases in a parabolic manner with the increase of pile-soil modulus ratio.The range of settlement ratio between pile-group and single pile is about 0.6~2.0,and the range of settlement ratio between pile group and single pile is larger when the ratio between pile spacing and pile diameter is smaller.When the ratio of pile spacing to pile diameter changes within 5~6,the settlement ratio of pile-group and single pile barely changes.