水–岩及风化作用下层状炭质板岩巴西劈裂试验研究

Brazilian tests on layered carbonaceous slate under water-rock interaction and weathering

横观各向同性层状板岩在地质环境及施工裸露后形成的水–岩和自然风化作用下,其物理力学性质将发生退化,由此常引起岩土隧道、边坡等工程产生抗拉失稳破坏。以甘肃岷县木寨岭隧道炭质板岩为研究对象,对其开展即时烘干试样(即试样加工后烘干处理)和静置风化试样(加工后室内常温通风放置60d)巴西劈裂试验,分析了两种条件下炭质板岩的抗拉力学性能。结果表明:两种炭质板岩巴西劈裂试验均表现为脆性破坏,但力学响应及峰值荷载差异极大;炭质板岩抗拉强度均受层理影响显著,但即时烘干试样和静置风化试样的劈裂破坏形态受层理影响程度不同;以即时烘干试样为基础,静置风化试样软化系数为0.11~0.13,体现了水岩作用及其静置风化对岩样具有显著劣化效应,但对层理形成的横观各向同性抗拉性能影响不大。此外,借助SEM对水岩静置风化机理进行分析,具体为水侵入后形成物理化学反应改变矿物微观成分、结构进而结合风化作用表现为矿物骨架承载的累计劣化损伤。

The physical-mechanical properties of transversely isotropic layered slates may be degraded due to water-rock interaction(WRI)and natural weathering,which potentially leads to the instability or collapse of tunnels,slopes and mining.In this study,based on the specimens sampled from the carbonaceous slates of Muzhailing Tunnel,the corresponding drying samples(drying in oven after fabrication)and weathering samples(for 60 days’natural weathering after fabrication)are prepared,respectively.The Brazilian tensile tests are conducted.The test results show that the two kinds of carbonaceous slates are both characterized by brittle failure,but the mechanical response covering failure displacement and the peak load are rather different.Further,the tensile strength are significantly affected by bedding while the cleavage failure patterns are also dominated by bedding.The softening coefficient of the static weathering samples is 0.11~0.13,which implies that the WRI and natural weathering play a vital role in the course of rock failure,but they have few influences on the transverse isotropic tensile properties of bedding.Moreover,the mechanisms of specimen failure are explained by the SEM technique to analyze the micro-components and observe the process of specimen deterioration due to physico-chemical reaction.