黄河冲淤积非饱和高塑性黏土的抗剪性状

Shear property of Yellow River's desposition in unsaturated and high plastic clay

为揭示非饱和土的抗剪性状与强度机理及关键影响因素,将非饱和土三维状态下的的抗剪强度公式简化为二维轴对称应力状态下的总应力强度公式,并采用常规三轴仪对黄河冲淤积非饱和高塑性黏土进行不同含水率、不同压实度下的不固结不排水试验。试验结果表明:黄河冲淤积高塑性黏土颗粒组成及物理性状具有自身的特殊性,粉粒含量高、塑限低,存在可碾压最小含水率临界范围,即高于最佳含水率约4%左右;该含水率范围是强度下降的临界点。该类土在应力作用下的抗剪性状受饱和度影响,表现为固、液、气相之间的相互作用与转换;对抗剪强度贡献最大的是基质吸力,且抗剪强度比其他非饱和类土大。本研究结论可为揭示非饱和高塑性黏土强度形成机理、确定现场碾压控制指标与工艺提供理论参考。

To reveal the unsaturated soil＇s shear property,strength mechanism and main factors affecting them,the shear strength formula for unsaturated soil in three dimensional state was simplified as the total stress strength formula for that in two-dimensional axisymmetric stress state,and also through the unconsolidated-undrained triaxial test of YellowRiver＇s desposition in unsaturated and high plastic clay under different moisture contents and different compactions by conventional triaxial apparatus. The test results showed that Yellow River＇s deposition＇s particle and its physical properties had their particularities： high silt containing,lowplasticity and the critical range for crushing the minimum moisture content,that was,4% higher than the best moisture content,which was the critical point for strength declining. Affected by the degree of saturation,shear property under stress was characterized by the interaction among solid,liquid and gas. The largest contribution to the shear strength of YellowRiver＇s desposition was the matrix suction,and its shear strength was bigger than that of other unsaturated soils. The research conclusion could provide theoretical reference for the formation mechanism of the unsaturated and plastic clay＇s strength,and also for determining the controlling index and process of field rolling.