水对第三系砂质砾岩力学特性影响的试验研究

Test Study on the Influence of Water on Mechanical Properties of the Tertiary Sandy Conglomerate

第三系砂质砾岩胶结性弱,整体性较差,尤其在遇水状态下易软化,会导致岩体承载力显著下降,在隧道开挖时的复杂应力状态下,水对岩体力学特性的影响更不容忽视。文章以我国中西部地区某隧道穿越的第三系砂质砾岩为研究对象,开展了多组大型剪切试验,结果表明:水的作用会降低第三系砂质砾岩的抗剪强度对法向应力的敏感程度;第三系砂质砾岩的抗剪强度参数会随着水浸润冲刷时间的延长而下降,但下降速率随着浸润冲刷时间的增加而降低,第三系砂质砾岩的抗剪强度指标与浸润冲刷时间呈负指数关系;推测第三系砂质砾岩中的胶结物随水流失导致胶结物性能弱化是第三系砂质砾岩抗剪强度下降的重要原因。

Tertiary sandy conglomerate has weak cementation and poor integrity,especially it is prone to softening in contact with water,which can significantly reduce the bearing capacity of the rock mass.Under the complex stress state during tunnel excavation,the influence of water on the mechanical properties of rock mass can not be ignored.A series of large-scale shear tests are carried out on the tertiary sandy conglomerate that a tunnel passes through in the central and western regions of China.The results show that the effect of water will reduce the sensitivity of the shear strength of the tertiary sandy conglomerate to the normal stress.The shear strength parameters of tertiary sandy conglomerate will decrease with the prolongation of water infiltration and scouring time,but the decrease rate will decrease with the increase of infiltration and scouring time.The shear strength index of tertiary sandy conglomerate has a negative exponential relationship with infiltration and scouring time.It is speculated that the weakening of cement performance caused by the loss of cement in tertiary sandy conglomerate with water is an important reason for the decrease of shear strength of tertiary sandy conglomerate.