在荷载作用下，裂隙岩体的缺陷不断产生、扩展，损伤持续累积，严重威胁岩体工程的安全稳定，揭示裂隙岩体损伤力学特性及破坏机理是解决岩体工程灾害难题的科学基础。本文在试验研究的基础上，采用理论分析、数值计算及智能分析相结合的方法，研究不同裂隙几何特征及围压下岩体力学性状与行为的演变规律，建立反映裂隙岩体变形破坏全过程特征的损伤本构模型，确立裂隙岩体强度预测模型，以期为岩体力学研究及工程稳定性评价提供新的思路和理论依据。主要研究内容及结论如下：
（1）研究不同裂隙几何特征及围压对岩体力学特性及破坏形态的影响。结果表明，岩体抵抗变形破坏能力与围压呈正相关，随裂隙长度、贯穿度及数量的增加而逐渐减弱，随裂隙倾角增加呈现先减弱后增强的趋势。随围压的增大，岩体由脆性向延性转变，完整岩样破坏形态由张拉向剪切演变，不同裂隙贯穿度岩样由拉剪复合型向剪切型转变，不同裂隙长度、数量及倾角岩样均表现为剪切破坏形态。
（2）根据岩体损伤与未损伤部分的受力及变形特点，建立能反映裂隙岩体变形破坏全过程特征的损伤本构模型，理论表征岩体的损伤特性及宏观力学行为。结果表明，岩体的应力-应变曲线、损伤演化曲线与其结构变化所诱发的宏观变形破坏过程均有良好的对应关系。裂隙的存在导致岩体力学特性劣化，其损伤程度随裂隙长度、贯穿度、数量的增加不断加剧，随着裂隙倾角增加呈现先增大后减小的特点。围压增大可以抑制岩体的内部损伤，提高抗压强度，塑性特征显著。
（3）采用离散元方法数值模拟不同裂隙几何特征岩体破裂演化全过程，从细观角度进一步阐述裂隙岩体的破裂机理。结果表明，岩体破坏过程分为裂纹萌生期、裂纹稳定扩展期、峰前裂纹加速扩展期、峰后裂纹加速扩展期4个阶段，岩体破裂形态表现为张拉破坏、剪切破坏及复合贯通破坏3种类型。岩体变形破坏过程及模式模拟结果与室内试验结果基本相同，其中不同裂隙长度对岩体强度影响最为显著。
（4）综合考虑裂隙几何特征、围压、物理及力学参数的相互关系，从试验结果中选取12个影响岩体强度的特征参量，采用机器学习-随机森林算法对裂隙岩体强度进行分类预测，得到多特征参量下岩体强度预测模型，确立强度与参量之间的映射关系，提供一种考虑岩体强度参数随机性与相关性的有效途径。结果表明，岩体强度处于[21~30] MPa的III类、[31~40] MPa的IV类、[41~50] MPa的V类及[51~60] MPa的VI类预测效果最佳，岩体强度处于[11~20] MPa的II类预测效果较好，岩体强度处于[0~10] MPa的I类预测效果次之。所获模型可推广应用于其他岩体强度预测。

~Under the action of load, the defects of fractured rock mass continue to produce and expand, and the damage continues to accumulate, which seriously threatens the safety and stability of rock mass engineering. Revealing the mechanical properties and failure mechanism of fractured rock mass damage is the scientific basis to solve the problem of rock mass engineering disaster. On the basis of experimental research, this paper adopts the method of theoretical analysis, numerical calculation and intelligent analysis to study the evolution law of mechanical properties and behavior of rock mass under the fracture structural characteristics and confining pressure, and establishes a damage constitutive model that reflects the characteristics of the whole process of deformation and failure of fractured rock mass, and the strength prediction model of fractured rock mass was established to provide new ideas and theoretical basis for rock mass mechanics research and engineering stability evaluation. The main research contents and conclusions are as follows:
(1) The influence of different fracture geometry characteristics and confining pressure on mechanical properties and failure modes of rock mass was studied. The results show that the rock mass resistance to deformation and failure is positively correlated with the confining pressure, decreases with the increase of fracture length, penetration and quantity, and decreases first and then increases with the increase of fracture dip angle. With the increase of confining pressure, the rock mass changes from brittleness to ductility, the failure pattern of intact rock samples changes from tensile to shear, the failure pattern of rock samples with different fracture penetration degrees change from tension-shear to shear, the rock samples with different fracture length, quantity, and dip angle show shear failure.
(2) According to the stress and deformation characteristics of the damaged and undamaged parts of rock mass, and a damage constitutive model which can reflect the whole process of deformation and failure of fractured rock mass is established to theoretically characterize the damage characteristics and macroscopic mechanical behavior of the rock mass. The results show that the stress-strain curve and damage evolution curve of rock mass correspond well with the macroscopic deformation and failure process induced by structural changes. The existence of fractures leads to the mechanical properties deterioration of rock mass, and the damage degree intensifies with the increase of fracture length, penetration and quantity, and increases first and then decreases with the increase of fracture dip angle. The increase of confining pressure can inhibit the internal damage of rock mass and improve the compressive strength, with remarkable plastic characteristics.
(3) The whole process of fracture evolution of rock mass with different fracture geometry characteristics is numerically simulated by discrete element method, and the fracture mechanism of fractured rock mass is further expounded from the meso point of view. The results show that the failure process of rock mass can be divided into four stages: crack initiation stage, crack stable growth stage, pre-peak crack accelerated growth stage and post-peak crack accelerated growth stage; There are three types of rock mass fracture form: tensile failure, shear failure and composite through failure. The deformation and failure process and model simulation results of rock mass are basically the same as the indoor experimental results, in which different fracture lengths have the most significant effect on rock mass strength.
(4) Comprehensively consider the relationship between fracture geometric characteristics, confining pressure, physical and mechanical parameters, 12 characteristic parameters affecting rock mass strength are selected from the experimental results, and the strength of fractured rock mass is classified and predicted by machine learning-random forest algorithm, the prediction model of rock mass strength under multi-characteristic parameters is obtained, and the mapping relationship between strength and parameters is established, which provides an effective way to consider the randomness and correlation of rock mass strength parameters. The results show that the prediction effect of rock mass strength in class III of [21 ~ 30] MPa, class IV of [31 ~ 40] MPa, class V of [41 ~ 50] MPa and class VI of [51 ~ 60] MPa is the best; the prediction effect of rock mass strength in class II of [11 ~ 20] MPa is good; the prediction effect of rock mass strength in class I of [0 ~ 10] MPa is the second. The model can be extended to other rock mass strength prediction.