巴东组第三段含钙质夹层土抗剪强度试验研究

Experimental Study on Shear Strength of Calcareous InterlayerSoil in the Third Member of Badong Formation

选取三峡库区巴东县巴东组第三段灰岩与泥灰岩间的软弱夹层土为研究对象,通过三轴不固结不排水试验(UU)剪切重塑土样,重点研究夹层土中CaCO3含量(0%,2%,4%,6%)对其抗剪强度的影响规律。再结合CT扫描试验,观察土样在三轴试验前后的内部孔隙率和胶结程度变化情况,以此作为依据,分析含钙质夹层土的抗剪强度变化机理。最终得出:随着CaCO3含量的增加,土样抗剪强度增大,这是因为CaCO3通过降低土体孔隙率和改变土颗粒形态增大了土体的内摩擦角,通过增强土体胶结能力增大了土体的黏聚力,从而增大其抗剪强度。此外,黏聚力的变化受CaCO3含量的影响更大,而内摩擦角的变化受CaCO3含量的影响较小。

The weak interlayer soil between the marlstone and limestone in the third member of the Badong formation,which widely exists in Badong County of the Three Gorges Reservoir Area,was taken as research object.The effect of CaCO 3 content(0%,2%,4%,6%)on the shear strength of weak interlayer soil were studied via unconsolidated undrained triaxial test(UU).Moreover,the changes of internal porosity and cementation degree of soil samples before and after the triaxial test were observed using CT scanning.On such basis,the mechanism of shear strength variation of calcium-containing weak interlayer soil was analyzed.Results indicated that the shear strength of interlayer soil increased with the rising of CaCO 3 content in soil samples because CaCO 3 enhanced the internal friction angle of soil by reducing soil porosity and changing soil particle morphology.In the meantime,the cohesion of the soil was strengthened by improving the cementing ability of the soil,thereby increasing the shear strength.In addition,the change of cohesion was more affected by the content of CaCO 3,while the change of internal friction angle was less affected by the CaCO 3 content.