龙川县花岗岩浅表层抗剪强度试验对比研究

以广东龙川县花岗岩残积土层与全风化层为研究对象,采用现场便携式剪切和钻孔剪切原位试验,以及室内重塑样快剪试验,研究不同含水率条件下的抗剪强度。结果表明：花岗岩残积土层与全风化层的抗剪强度均随着含水率的增加而减小。残积土层现场原状样试验所得抗剪强度均高于室内重塑样,二者差异的主要因素为重塑样颗粒间不再具有较强的结构联接；全风化层原位试验所得内聚力大于室内试验,但两种试验内摩擦角近乎一致,造成原位与室内试验结果的差异不仅与重塑样较弱的结构联接有关,还由于剪切边界条件与应力状态不尽相同。花岗岩浅表层无论是残积土层还是全风化层,均具有较强的结构性,室内重塑样试验结果往往不能真实反映土体的抗剪强度,室内重塑土试验所得到的抗剪强度值偏低。

Comparative Study on Shear Strength of Granite Shallow Layer in Longchuan County

Taking the granite residual soil layer and fully weathered layer in Longchuan County, Guangdong Province as research objects, the shear strength under different water content conditions was studied by in-situ portable shear and drilling shear tests as well as in-situ rapid shear tests of remolded samples. The results show that the shear strength of both the granite residual soil layer and the completely weathered layer decreases with the increase of water content. The shear strength obtained from in-situ prototype test of residual soil layer is higher than that of laboratory remolded sample, and the main reason for the difference is that there is no longer strong structural connection between the particles of the remolded sample; The cohesion obtained from in-situ test of fully weathered layer is larger than that obtained from laboratory test, but the internal friction angle of the two tests is close to the same. The difference between in-situ and in-situ test results is not only related to the weak structural connection of the remolded samples, but also to the different shear boundary conditions and stress states. The shallow surface layer of granite, whether residual soil layer or completely weathered layer, has strong structural characteristics. Laboratory remolding test results often fail to reflect the shear strength of soil, and the shear strength obtained from indoor remolded soil test is low.