Research for the Evaluation of Strength of Unsaturated Soil under Seepage Water Accompanied by Volume Change

非饱和土的强度对于边坡和/或河堤的稳定性评估是必要的。本研究的第一个项目是量测在渗流作用下，粉土中发生坍塌时的孔隙水压力。第二种方法是将定压法和定体积法的抗剪强度进行比较，由于粉土中孔压很小，因此不采用有效压力，而采用总压力。获得的结果如下。(1)In通过土层模型试验，将孔隙水压力等效为渗透水作用下土层发生坍塌时的上覆土压力。在改良式土压计试验中，由于孔隙空气不释放，渗流不能进入孔隙，故实测孔隙压力一般为上覆土压力的1/30。（2）利用直剪仪和环剪仪，对“非浸水”和“浸水至非浸水峰值强度的60%水平剪应力”的两个粉土试件进行了抗剪强度试验。 ...更多信息 用恒压和恒容两种方法来测试，如以下结果所示。（1）在试样浸水和坍塌后，剪应力福尔斯立即下降到零，但随着应变的增加，剪应力又略有恢复。（2）当阻力角为20.4°时，浸水强度和恢复强度均小于未浸水时的27.1°。(3)In松散试样的定容试验表明，围限土中平均压力福尔斯大幅度下降，剪应力变小，但强度参数特别是阻力角与非浸水试样在定压条件下的强度参数相当。(4)It剪切强度很大程度上取决于内应力和体积变化。(3)未能建立边坡变形与稳定性分析的数值模拟，以检验上述结果，并希望下一步的评论成为现实。（1）塌陷不是发生在密实的粉土中，而是发生在渗水作用下的松散粉土中，后者的土容易塌陷。（2）由于定容试验遵循水下内应力的变化规律，且压力恒定，故推荐采用定容试验。少

Necessary is the strength of unsaturated soils for the stability evaluation of slopes and/or river levees. In this study, first item is to measure the pore pressure occurred with collapse under seepage water in silt. Second is to compare the shear strength obtained from constant pressure with the one from constant volume, using not effective pressure but total pressure, because pore pressure is very small in silt. Obtained results are following.(1)In soil layer model experiment, the pore pressure is measured equivalent to the overburden pressure when collapse occurred in soil layer under seepage water. In modified Oedmeter test, measured pore pressure is fairly the amount of 1/30 of overburden pressure owing to the difficulties that seepage does not enter soil pore without pore air released.(2)Using the direct shear and ring shear apparatus, two specimens of silt with "the non-submerged one" and "the submerged at the 60% level shear stress of the peak strength of non-submerged", are te … More sted both by constant pressure and constant volume, as is obtained following results.(1)Just after specimen submerged and collapsed, the shear stress falls down to zero but recovered a little with strain increment.(2)The submerged and recovered strength as angle of resistance 20.4° is smaller than the non-submerged one as 27.1°.(3)In constant volume test of loose specimen, average pressure in confined soil falls greatly and then shear stress become small.However, strength parameter especially angle of resistance become equal to the one of non-submerged sample corresponding to constant pressure.(4)It is necessary that the shear strength greatly depends on both inner stresses and volume change.(3) It is failed to establish the numerical simulation of slope deformation and stability analysis which aims to examine the above results, and then next comments are hoped to become true.(1)The collapse occurs not in dense silt but loose silt under seeped water, and the latter soil is easy to collapse.(2)The constant volume test can be recommended because it follows inner stress change under water, and the constant pressure. Less