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为研究泥岩力学参数遇水软化特性,以重庆几江长江大桥隧道锚碇所在遂宁组(Jsn3)紫红色泥岩持力层为研究对象,系统地开展了室内及原位力学试验。结论如下:(1)泥岩天然极限抗压强度5.8 MPa,饱和极限抗压强度4.1 MPa,软化系数0.71,水对泥岩单轴抗压强度弱化作用明显。(2)泡水8 d后,泥岩的变形模量和弹性模量较天然状态下平均降低了31.0%、23.77%,抗变形能力降低;遇水后,孔隙中粘土矿物与水反应,细小岩粒吸附的水膜厚度增加,体积膨胀,导致变形模量及弹性模量下降。(3)相较天然状态,泡水8 d的抗剪断峰值与粘聚力值分别降低了15.12%与2.08%。泡水后,泥岩中微裂隙膨胀软化不均一,内摩擦角与粘聚力不均匀降低,导致力学强度值降低;渗水沿着裂隙浸润,裂隙逐渐延伸并继续向软弱结构纵深发展,时间越长,不规则多边形裂隙面趋向浑圆,起伏不均的结构面变得平整圆润。
In order to study the water softening characteristics of mechanical parameters of mudstone, indoor and in situ mechanics tests were carried out systematically in the purple sandstone bearing layer of Suining Formation (Jsn3) where the anchorage of Chongqing Jingjiang River Yangtze River Bridge tunnel was located. The conclusions are as follows: (1) The natural compressive strength of mudstone is 5.8 MPa, the ultimate compressive strength is 4.1 MPa, and the softening coefficient is 0.71. The uniaxial compressive strength of mudstone weakens obviously. (2) After soaked for 8 d, the deformation modulus and elastic modulus of mudstone decreased by 31.0% and 23.77% on average compared with the natural state, and their anti-deformation ability decreased. After the water was absorbed, the clay mineral reacted with water and fine rock The thickness of the water film adsorbed by the particles increases and the volume expands, resulting in a decrease of the deformation modulus and the elastic modulus. (3) Compared with the natural state, the shearing peak and cohesive value decreased by 15.12% and 2.08% respectively for 8 d of soaking. After soaked in water, the micro-cracks in the mudstone expand and soften unevenly, and the internal friction angle and cohesion decrease nonuniformly, which leads to the decrease of the mechanical strength. The seepage water infiltrates along the crack, and the crack gradually extends and continues to develop in depth to the weak structure , Irregular polygons crack surface tend to rounded, uneven surface roughness become smooth.