饱水软岩力学性质软化的试验研究与应用

EXPERIMENTAL RESEARCH ON THE SOFTENING OF MECHANICAL PROPERTIES OF SATURATED SOFT ROCKS AND APPLICATION

软岩遇水后力学性质软化规律的研究,是水–岩相互作用研究的重要课题之一,在重大工程的设计与实践中具有重要意义。通过对华南地区广为分布的红色砂岩、泥岩及黑色炭质泥岩等几种不同类型的典型软岩在不同饱水状态的试验设计和力学性质测试,重点探讨了软岩软化的力学规律性。试验按照天然状态、饱水1,3,6和12个月等饱水时间点进行采样分析,测定其不同饱水时间点的单轴抗压强度、劈裂抗拉强度、抗剪强度及其随饱水时间的变化规律。结果表明:软岩与水相互作用后,其抗压强度、抗拉强度及抗剪强度变化的定量表征关系一般服从指数变化规律,各力学强度指标将随着饱水时间的延长而不断降低,最终将趋向稳定;6个月的饱水时间点为软岩力学强度趋于稳定的临界点。以此研究获得的软岩参数为基础,采用非线性有限元强度折减法对广东省东深供水改造工程中BIII2边坡稳定性进行了分析计算,结果表明:在塑性应变区贯通前,该边坡主断面的稳定性系数为0.83,说明BIII2边坡处于不稳定状态。这与实际边坡所处的状态非常一致。表明该试验研究结果用于工程计算中具有较好的意义,亦可为华南地区类似工程的设计、施工和长期稳定性分析等提供具有重要价值的参考。

Research on softening regularities of mechanical properties of saturated soft rocks and their application is one of the important theoretical and practical problems in geotechnical fields. The mechanical regularities of some typical kinds of soft rocks such as red siltstone, red mudstone, and black carbonaceous mudstone, which are widely distributed in South China, are discussed by designing a series of experiments of interaction between soft rocks and water, and their mechanical parameters are correspondingly tested. By sampling according to a time sequences including natural state and saturated states in different time (1 month, 3 months, 6 months, and 12 months) of soft rocks, the uniaxial compressive strength, cleave tensile strength, shearing strength, and their varying regularities along with time developing are analyzed. The results show that the mechanical properties mentioned above probably conform to an exponent curve after different saturated time on which the point in 6 month is the critical time for mechanical properties changing from gradually declining to stable state. On the basis of experimental data, by selecting a main section, the BIII2 slope stability in Water Supply Reconstruction Project from Dongjiang to Shenzhen, Guangdong China, is analyzed by nonlinear strength reduction finite element method (FEM). The calculated safety factor is 0.83, which coincides very well with the actual state of the slope. It means that the test results have an important significance for application to engineering and can provide a scientific reference for designing and construction as well as long term safety monitoring and analysis for other similar engineering problems in South China.