地震研究

针对如何科学合理地评价液化场地加筋碎石桩复合饱和砂土地基抗液化能力这一问题,利用OpenSees计算平台建立非线性有限元数值模型,并与模型试验进行对比分析,验证数值模型的准确性; 进而研究分析了不同工况下复合地基剪应力折减系数比的变化规律,并修正其计算公式,提出并验证适合评价复合地基抗液化能力的简化方法。研究表明:随着桩径、加筋体强度和桩土剪切模量比的增大,复合地基剪应力折减系数比不断增大; 以桩土剪切模量比作为控制参量,评价单一液化土层条件下沿桩身全长布筋的加筋碎石桩复合场地抗液化能力的简化方法准确可信。

In order to evaluate the liquefaction resistance capability of the composite saturated sandy soil foundation with geosynthetic-encased stone column scientifically and reasonably,the accuracy of the numerical model is verified by the comparative of nonlinear finite element numerical simulation and model test using the Opensees computing platform.Then the variation law of shear stress reduction coefficient ratio of composite foundation under different working conditions is studied and analyzed.The results show that the shear stress reduction coefficient ratio of composite foundation increases with the increase of the pile diameter,reinforced body strength,and pile-soil shear modulus ratio.Also,the calculation method of shear stress reduction coefficient ratio of composite foundation is modified.Finally,a simplified method is proposed and verified to evaluate the liquefaction resistance capability of the geosynthetic-encased stone column in a single liquefied soil layer with the pile-soil shear modulus ratio as the control parameter.

引言
1 振动台试验数值建模
2 加筋碎石桩动力响应参数分析
3 循环应力比折减系数
5 结论

图1 振动台试验示意图<br/>Fig.1 Experimental setup of the shaking table test

图1 振动台试验示意图
Fig.1 Experimental setup of the shaking table test

表1 南京砂土物理性质参数<br/>Tab.1 Physical properties of the Nanjing sand

表1 南京砂土物理性质参数
Tab.1 Physical properties of the Nanjing sand

图2 试验基底激励<br/>Fig.2 Test base excitation

图2 试验基底激励
Fig.2 Test base excitation

图3 三维有限元模型<br/>Fig.3 3D finite element model

图3 三维有限元模型
Fig.3 3D finite element model

表2 砂土与碎石计算参数<br/>Tab.2 Parameters of sand and gravel

表2 砂土与碎石计算参数
Tab.2 Parameters of sand and gravel

表3 筋材物理性质<br/>Tab.3 Physical properties of geosynthetic

表3 筋材物理性质
Tab.3 Physical properties of geosynthetic

图4 试验台面记录的基底激励<br/>Fig.4 Base input motion recorded by the test table

图4 试验台面记录的基底激励
Fig.4 Base input motion recorded by the test table

图5 超孔隙水压力时程试验值与模拟值(埋深1.0 m)<br/>Fig.5 Computed and experimental excess pore pressure time history at 1.0 m depth

图5 超孔隙水压力时程试验值与模拟值(埋深1.0 m)
Fig.5 Computed and experimental excess pore pressure time history at 1.0 m depth

图6 加速度时程试验值与模拟值(埋深1.0 m)<br/>Fig.6 Computed and experimental acceleration time history at 1.0 m depth

图6 加速度时程试验值与模拟值(埋深1.0 m)
Fig.6 Computed and experimental acceleration time history at 1.0 m depth

表4 加筋碎石群桩复合地基模拟分析方案<br/>Tab.4 The numerical simulation scheme of the reinforced gravel pile composite foundation

表4 加筋碎石群桩复合地基模拟分析方案
Tab.4 The numerical simulation scheme of the reinforced gravel pile composite foundation

图7 加筋体刚度对超孔隙水压力的影响<br/>Fig.7 Effect of stiffness of geosynthetic on excess pore pressure ratio

图7 加筋体刚度对超孔隙水压力的影响
Fig.7 Effect of stiffness of geosynthetic on excess pore pressure ratio

图8 加筋体刚度对地表加速度的影响<br/>Fig.8 Effect of stiffness of geosynthetic on ground acceleration

图8 加筋体刚度对地表加速度的影响
Fig.8 Effect of stiffness of geosynthetic on ground acceleration

图9 桩径对超孔隙水压力的影响<br/>Fig.9 Effect of pile diameter on excess pore pressure ratio

图9 桩径对超孔隙水压力的影响
Fig.9 Effect of pile diameter on excess pore pressure ratio

图10 桩径对地表加速度的影响<br/>Fig.10 Effect of pile diameter on ground acceleration

图10 桩径对地表加速度的影响
Fig.10 Effect of pile diameter on ground acceleration

图11 桩土剪切模量比Gr对超孔隙水压力的影响<br/>Fig.11 Effect of shear modulus ratio of column to soil(Gr)on excess pore pressure ratio

图11 桩土剪切模量比Gr对超孔隙水压力的影响
Fig.11 Effect of shear modulus ratio of column to soil(Gr)on excess pore pressure ratio

图12 桩土剪切模量比Gr对地表加速度的影响<br/>Fig.12 Effect of shear modulus ratio of column to soil(Gr)on ground acceleration

图12 桩土剪切模量比Gr对地表加速度的影响
Fig.12 Effect of shear modulus ratio of column to soil(Gr)on ground acceleration

图13 不同加筋体抗拉刚度(a)、不同桩径(b)及不同桩土剪切模量比Gr(c)剪应力折减系数比分布<br/>Fig.13 Shear stress reduction coefficient ratio under different geosynthetic stiffness(a),pile diameters(b)and shear modutus ratio of gravel pile to soil(c)

图13 不同加筋体抗拉刚度(a)、不同桩径(b)及不同桩土剪切模量比Gr(c)剪应力折减系数比分布
Fig.13 Shear stress reduction coefficient ratio under different geosynthetic stiffness(a),pile diameters(b)and shear modutus ratio of gravel pile to soil(c)

图14 地震应力作用下饱和砂土复合地基应力分解<br/>Fig.14 The schematic diagram of stress decomposition under an earthquake

图14 地震应力作用下饱和砂土复合地基应力分解
Fig.14 The schematic diagram of stress decomposition under an earthquake

图15 Gr与γr拟合结果<br/>Fig.15 Fitting curve betweenGr and γr

图15 Gr与γr拟合结果
Fig.15 Fitting curve betweenGr and γr

图16 有限元方法和简化方法计算剪应变比γr<br/>Fig.16 Shear strain ratio γr from finite element method and simplified method

图16 有限元方法和简化方法计算剪应变比γr
Fig.16 Shear strain ratio γr from finite element method and simplified method

图17 简化方法验证<br/>Fig.17 The verification of proposed simplified method

图17 简化方法验证
Fig.17 The verification of proposed simplified method

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备注

引言

1 振动台试验数值建模

2 加筋碎石桩动力响应参数分析

3 循环应力比折减系数

5 结论

期刊信息