加载速度对强度和破坏机制的影响

岩体力学实验中,加载速度对岩体力学性质的影响是很重要的。许多岩体力学工作者,利用岩块和模型材料,进行了大量有关室内加载速度对岩体力学性质影响的研究,为室内岩块力学试验和野外原位岩体力学试验选取合理加载速度提供了依据。目前,基本上从应变速率和应力速率两方面去研究加载速度对岩体力学性能的影响。这两方面的研究都认为随着应变速率和应力速率的增加,岩块和岩体的强度、变形模量也相应增加,不同的是峰值强度以后的破坏后效不同。

THE EFFECT OF LOADING RATE ON STRENGTH AND FAILURE MECHANISM OF ROCKS

The loading rate gives an significant effect on the mechanical properties of rocks.That is proved by our tests reported in this paper.The experimental models are made up of cement mortar with a size in 16×20×20cm³.The model material possesses the uniaxial compresseve strength of 177 kg/cm² and the deformation module of 5×104 kg/cm².We fix up 5 holes in the longitudinal central section of model,among which two holes are filled up with radon emanation.The rest three holes are used as measuring holes for monitoring radon emanation.The different stage of loading may be determined by measuring the variation of radon emanation.According to model tests of loading rate,the following conclusions can be constructed:1.The uniaxial compressive strength and modulus of deformation are increasing with the increase of loading rate.It is found that the relationship between the uniaxialt compressive strength and loading rate can be expressed as σ_c=152e^{0.43logσ+0.057(logσ)2} 2.The whole processes from begining of loading to failure of test-pipce underwent through following five stages: 1) compaction,2) elastic deformation,3) constantly fractured propagation,4) unconstantly fractured propagation,5) differential fracture-failure stage.3.The failure mode of specimens varies with the change of loading rate.The specimens begin to failure in tension as the loading rate is higher,on the contrary they are in shear failure as the loading rate is lower and in tension-shear failure as the loading rate is median.