A nonlinear strength criterion for rock- like materials is developed in this paper. Taking α as an angle of micro- failure orientation in rock- like materials, a formulation between α and load is derived from a mixed- mode fracture criterion based on linear elastic fracture mechanics. According to micro- failure experimental phenomena of rock- like materials, a failure characteristic parameter under triaxial compression condition is chosen, which is relevant to confining pressure and is an invariant. A theoretical nonlinear strength criterion is also derived, which is exactly in the same mathematical form as the original Hoek- Brown empirical strength criterion. In addition, it is also found that the coefficient m in the Hoek- Brown criterion has physical meaning which is related to the ratio between the uniaxial compressive strength and the uniaxial tensile strength.

Scanning electronic microscopy(SEM) was employed to investigate fractographs of sandstone in mine roof strata under thermal- mechanical coupled effect. Based on the evolution of sandstone surface morphology in the failure process and fractography, the fracture mechanism was studied and classified under meso and micro scales, respectively. The differences between fractographs under different temperatures were examined in detail. Under high temperature, fatigue fracture and plastic deformation occurred in the fracture surface. Therefore, the temperature was manifested by these phenomena to influence strongly on micro failure mechanism of sandstone. In addition, the failure mechanism would transit from brittle failure mechanism at low temperature to coupled brittle- ductile failure mechanism at high temperature. The variation of sandstone strength under different temperature can be attributed to the occurrence of plastic deformation, fatigue fracture, and microcracking. The fatigue striations in the fracture surfaces under high temperature may be interpreted as micro fold. And the coupled effect of temperature and tensile stress may be another formation mechanism of micro fold in geology.

Whether or not the surface morphologies of conducting polythiophene films with nanotubular structure having a fractal characteristic was investigated based on the scanning electrical microcopy(SEM) images with self- organized nanostructure. Fractal results indicated to be valued in the quantitative characterization of the surface morphologies of electrochemically synthesized polythiophene films. The fractal characterization of surface morphology depended mainly on the grizzly threshold on these SEM images. The relationship between the threshold and the fractal dimensionality can be expressed as a function. Therefore, the fractal dimensionality of surface morphology and nanostructure of these films might relate to the mechanical properties/ behaviors or their electrochemically synthesized process. The fractal dimensionality was also illuminated from the physical point of view based on a binary image analysis. In addition, the effect factors and similarity rule of fractal dimensionality in those SEM images analyzers were discussed. The critical value to affect the determining fractal dimensionality was obtained.

砂岩的热开裂研究具有广泛的工程背景，本文实时在线观察和研究了不同温度作用下平顶山砂岩的热开裂：温度低于150℃时，砂岩几乎不发生热开裂；温度从150℃升高到300℃过程中大量的热开裂发生，而不同的矿物成分发生热开裂的阈值温度不完全相同，因此热开裂的阈值温度或者阈值温度范围只具有统计意义。砂岩热开裂主要与矿物成分的热学与力学性质有关，除了受到矿物热膨胀不匹配及热膨胀各向异性的影响，更重要的还受到矿物颗粒形状的影响，如热开裂多发生在矿物颗粒的短轴方向、优势结晶取向、颗粒奇异界面等，且热开裂的分布具有随机性。实验还观察到砂岩表面微缺陷发生闭合的全过程，在冷却过程也有微裂纹形成等现象。

通过扫描电镜(SEM)研究了煤层顶板砂岩拉伸断裂后的断口形貌图，结合砂岩破坏的表面形貌图，在细观和微观层次对砂岩的断裂机制进行了研究；比较了受不同温度影响后的微观断口形貌差异，特别是高温疲劳断口的出现，证实了温度对砂岩破坏的微观断裂机制产生了影响，即随着温度的升高，砂岩的断裂机制由以局部脆性断裂机制为主向局部脆性和延性耦合断裂机制转变，并观察到大量的塑性变形，这是影响砂岩强度变化的根本原因，并可能是微褶皱。

通过扫描电镜研究温度—拉应力共同作用下砂岩破坏的断口形貌。通过研究不同温度影响后的解理断口、准解理断口、疲劳断口、非主断裂面的二次裂纹和碎裂断口、局部延性断口、沿晶断口及一些奇特的断裂花样，证实温度对砂岩断裂的微观机制产生了影响，随着温度的升高，砂岩的断裂机制由以局部脆性断裂机制为主向局部脆性和延性耦合断裂机制转变。低温下的断口较为光滑平坦，高温下的断口较为粗糙，表明发生过塑性变形，并且高温断口形貌更为多样和更为复杂，这主要是受到高温影响后，岩石内部矿物颗粒、晶体和原子热运动加剧，当岩石受到外部载荷作用时断裂就有可能出现在更大范围的位置。通过一些简单的断裂机制示意图对部分断口形貌进行解释，并报道了一些特殊的岩石断口形貌。综合认为金属断口学研究中所发现的微观断口形貌特征几乎都可以从岩石断口形貌中找到，但由于岩石是多晶体地质材料，高温影响下岩石的断口形貌还将更为多样和更为复杂。

应用DDA数值方法模拟分析了深部煤矿开采中上覆岩层的应力场变化和变形移动规律，并与相似物理模型试验进行了对比。结果表明：DDA法可以有效地模拟出上覆岩层的应力场变化趋势和变化范围、不连续块体的变形和位移、岩层垮落和“离层”现象。数值模拟结果与模型实验结果相吻合。

以淮南潘—矿11- 2槽煤层2171(1)工作面为工程背景，进行了深部开采情况下上覆岩层的移动和地表沉陷相似材料模型实验。将非接触式的光学测量技术数字散斑相关方法引入到该实验中来，对该方法应用于相似材料模型实验的精度进行了分析，通过计算得到了不同推进度下的上覆岩层移动的全场等高线云图，分析了上覆岩层的移动规律。结果表明，数字散斑相关方法不仅克服了传统机械点测量方法的某些缺点，同时具有较高的精度，可用于相似材料的模型实验。

越来越多的煤矿和金属矿进入深部开采。随着开采深度的增加，一系列工程灾害如岩爆、煤与瓦斯突出、顶板垮落、底板突水等日益严重，且深部开采中巷道与采场的维护理论也与浅部有十分明显的区别。人们认识到这种差别的根源在于岩石所处的赋存环境上的差异，深部与浅部在赋存环境上的差别是所谓“三高”即高地应力、高地温和高孔隙水压，尤其是高地应力条件下岩石表现出十分特殊的力学行为。简要介绍了深部开采现状、深部开采面临的技术难题以及深部岩体所处的高地应力环境，在此基础上，综述了深部高地应力条件下有关岩石力学性质的研究进展，包括高应力条件下岩石的脆—延转化特性、岩石的流变特性、岩石的强度特征、岩石的破坏特征尤其是岩爆等。文章最后指出深部条件下热—水—力耦合模型是一个值得关注的研究方向。