砂砾土振动体变评价方法与离心机模型试验验证

Evaluation method for shaking-induced volumetric strain for gravelly soils and validation by centrifuge model tests

2008汶川地震出现了砂砾土大范围液化致灾现象,现场震害调查表明砂砾土场地存在砾石效应影响,现有砂土场地的震后沉降评价方法不适用于砂砾土场地。对此,在“张-社本”振动体变评价方法的基础上进一步发展了考虑砾石含量的砂砾土振动体变评价方法,然后开展动三轴试验确定评价方法中的相关参数,最后开展3组典型砾石含量的砂砾土地基离心机振动台模型试验对评价方法的可靠性进行验证。试验结果表明,砾石含量越高,振动引起的场地沉降变形越小;砂砾土振动体变评价方法可以较为准确地预测新近沉积砂砾土场地的震后沉降,但对存在地震历史影响的砂砾土场地,本文提出的评价方法较为保守,建议进一步发展考虑地震历史效应的砂砾土振动体变评价方法。

Liquefactions of gravelly soils are widely distributed in the 2008 Wenchuan earthquake.Field investigations show that the existing settlement evaluation methods for sands are not applicable to the gravelly soils due to the gravel content effects.It is aimed to develop the evaluation method for shaking-induced volumetric strain for the gravelly soils with consideration of gravel content,which is based on the so-called"Zhang-Shamoto"model.The dynamic triaxial tests are conducted to parameterize the evaluation method,and three centrifuge model tests on the gravelly soil grounds with typical gravel contents are carried out to check the performance of the proposed evaluation method.The test results show that the higher the gravel content,the smaller the shaking-induced settlement.The proposed evaluation method can accurately predict the shaking-induced settlement for recently deposited gravelly soils,but shows a conservative prediction performance in cases with pre-shaking effects,which suggests the need to further improve the proposed evaluation method by considering the pre-shaking effects.