含水状态对红层软岩力学特性影响机理

饱水状态下,红层软岩力学特性的劣化直接影响相关工程的变形稳定。考虑干燥、自然和饱水3种状态,对红层软岩抗压和抗拉强度特性、变形破坏特征及微观结构特征进行了比较系统的试验和检测分析。研究表明:①饱水状态下红层软岩的软化特征明显,破坏时的延性特征更加明显,不同围压下岩样的抗压强度软化系数为0.36~0.65,相对于干燥状态,弹性模量和变形模量逐渐降低分别降低了35.60%~75.53%,44.57%~69.64%,而且围压越小,抗压强度和模量降低趋势越明显;②相对干燥状态,饱水状态下岩样的黏聚力、内摩擦角分别下降了47.77%和12.68%,岩样的黏聚力对含水状态更为敏感;③饱水状态下岩样抗拉强度软化系数为0.40,加载线附近局部破坏特征明显;④岩样内部矿物颗粒间泥质胶结物的溶解破坏,伊利石、蒙脱石等黏土矿物吸水膨胀、分解,使得岩体结构由相对密实状态逐渐变得多孔、松散,而且孔隙多被水充填,这些微观结构的改变直接导致了红层软岩力学性质的劣化。

Mechanical properties of red-bed soft rock on saturated state

The degradation of the mechanical characteristics of red bed weak rock at saturated state directly affects the deformation stability of the related engineering structure.The characteristics of compressive strength and tensile strength，and deformation and failure characteristics and microstructure characteristics of red bed weak rock were tested and the test analysis systematically considered the drying，natural and saturated state.The results are as follows：① Softening characteristics of red bed weak rocks at saturated state were significant and the ductility features of failure were more obvious.The softening coefficient of compressive strength of rock specimens under different confining pressures was 0.36-0.65.The elastic modulus and deformation modulus decreased gradually and was reduced by 35.60%-75.53%，44.57%-69.64% respectively relative to the dry state.Also，the smaller the confining pressure was，the more obviously compressive strength and modulus decreased.② The cohesive force and internal friction angle of rock specimen at saturated state fell 47.77% and 12.68% respectively relative to the dry state，and the cohesive force was more sensitive to the moisture state of rock specimen.③ The softening coefficient of tensile strength of rock specimens at saturated state was 0.40，and the characteristic of the local failure near load line was particularly obvious.④ Because of the dissolution damage of argillaceous cement among the mineral particles of the rock specimens and the swell and decomposition of clay minerals such as illite and montmorillonite，rock mass structure changed from dense state to porous and loose state gradually and the pores were filled by water.The microstructure change directly led to the degradation of the mechanical properties of red bed weak rock.