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边坡、隧洞、矿井等岩土工程的失稳过程都伴随着岩体的扩容现象,研究各种工程岩体的扩容特性对工程岩体稳定性评价有重要意义。采用TAW-2000电液伺服岩石三轴试验机,通过对8种岩样的单轴、三轴压缩试验结果分析,获得了低围压下的应力–体积应变曲线,寻求不同岩石的扩容起始点的的变化规律,揭示岩石扩容起始特性与峰值点特性的对应关系。研究结果表明:①岩石扩容起始点处的应力随着围压的增大而增大,并且相比峰值点应力变化,扩容起始点的应力随着围压的变化更强烈;②分别定义了岩石的扩容起始点与峰值点的应力比和应变比计算公式,应力比和轴向应变比呈现很强的线性相关性,并且与其岩性和围压无关。如果确定了峰值点的应力应变关系,便可以较方便地找到岩石的扩容起始点。通过岩石扩容起始点与峰值点变化规律的研究,找到了一条确定岩石扩容起始点的新思路,对岩石的长期强度预测提供了理论依据。
The failure process of geotechnical engineering such as slope, tunnel and mine is accompanied by the expansion of rock masses. It is of great significance to study the expansion characteristics of various engineering rock masses to evaluate the stability of engineering rock mass. Using TAW-2000 electro-hydraulic servo triaxial testing machine, the stress-volume strain curves under low confining pressure were obtained by analyzing the uniaxial and triaxial compression tests of eight kinds of rock samples to find the starting point for the expansion of different rocks The relationship between the initial characteristic of rock expansion and the characteristic of peak point is revealed. The results show that: (1) the stress at the initial point of rock expansion increases with the increase of confining pressure, and the stress at the starting point of expansion is more intense with confining pressure than that of peak point; (2) The formulas of stress ratio and strain ratio at the starting point and peak point of expansion are linearly correlated with stress ratio and axial strain ratio, and have no relation with lithology and confining pressure. If we determine the stress-strain relationship at the peak point, we can find the start point of rock expansion more conveniently. Through the study of the change rule of the starting point and the peak value of rock expansions, a new idea to determine the starting point of rock expansion is found, which provides a theoretical basis for the long-term strength prediction of rock.