上海软黏土强度固有各向异性

Strength Anisotropy of Shanghai Soft Clay Induced by Inherent Fabric

摘要:

采用室内异形十字板试验对上海淤泥质黏土原生结构导致的不排水抗剪强度的固有各向异性特征进行研究.从基坑中取得筒状土样，然后采用两个具有不同长宽比的矩形板头和三个不同角度（30°，45°和60°）的菱形板头进行室内异形十字板剪切试验，得到了原状土在不同方向破坏面上的不排水抗剪强度.结果表明：由于上海软黏土原生结构的影响，在总应力为零的情况下，其不排水抗剪强度随着破坏面与水平面夹角的增大而增大，即破坏面为水平向时强度最小，竖直向时强度最大.十字板试验结果与直剪试验、无侧限抗压强度试验的结果有很好的一致性.推荐采用Casagrande和Carrillo提出的公式来计算上海软黏土各向异性不排水强度.

关键词:软黏土; 原生结构; 各向异性强度; 十字板剪切试验

Abstract:

The inherent anisotropic of the strength of Shanghai soft clay caused by inherent structure were investigated by vane shear tests. Block soil samples were obtained from pit excavation. Then two rectangular vanes with different length width ratio and three diamond plates with different angle (θ=30°，45°，60°) were used in laboratory to obtain the undrained shear strength at the failure surface in different directions. Test results indicate that the inherent structure of Shanghai soft clay leads to the undrained shear strength increases with the increase of inclined angle between the failure face and horizontal plane; the strength in horizontal plane is minimum and the strength in vertical plane is maximum. These results have good coincidence with the direct shear test results and unconfined compression tests results. The anisotropic strength equation proposed by Casagrande and Carrillo is suggested to be used to calculate the strength anisotropy of Shanghai clay.

Key words:soft clay; inherent fabric; strength anisotropy; vane shear test