Study On Mechanical Response Characteristics And Damage Mechanism Of Water-containing Muddy Rock Mass Under Dynamic Load

As resource extraction moves deeper,the stability of engineering activities in deeper rocks becomes a key issue.Especially in muddy rock masses,hydration phenomena can lead to a decrease in the strength and stability of the rock masses,while engineering dynamic load disturbances such as underground mining,excavation,drilling and blasting can further aggravate their damage and destruction,thus leading to engineering disasters.Therefore,it is necessary to study the stability of muddy rock masses under dynamic loads,which can help improve the safety and science of coal mining.At the same time,the research results can also be applied to the engineering construction and geological disaster prevention of other water-containing muddy rock masses.In view of this,this thesis takes water-containing argillaceous soft rocks as the research object and carries out macroscopic mechanical properties tests and fine damage evolution simulation studies on mud rocks under cyclic dynamic loading,revealing the mechanical response characteristics and damage destabilisation mechanism of mud rocks under dynamic loading coupled with water-rock action.The main research contents and results are as follows:（1）The mechanical response characteristics of water-containing argillaceous soft rocks under dynamic load disturbance were elucidated.The results show that the increase of water content can cause the decrease of peak strength of mudstone,and the increase of dynamic load rate can improve the bearing performance of mudstone.The effects of different water content,dynamic load rate and dynamic load strength on the mechanical properties and deformation and damage characteristics of the mudstone were investigated.The results show that with the increase of water content,the damage effect of dynamic load on the mudstone is more significant,and the resistance to dynamic load disturbance of mudstone decreases with the increase of dynamic load rate and decreases with the increase of dynamic load strength.（2）The evolution of mudstone acoustic emission characteristics under cyclic dynamic loading is clarified.The relationship between the stress-time curve and AE energy,cumulative event number and other acoustic emission characteristics of mudstone under the influence of water content,dynamic loading rate and dynamic loading intensity is investigated.Based on the acoustic emission characteristics of mudstone with different water content at each loading stage,four periods of fracture evolution,namely initial damage,increasing damage,silent damage and developing damage,were delineated.（3）The mechanical behaviour of mudstone under cyclic dynamic loading is systematically studied.The deformation behaviour,modulus change pattern,fracture pattern and fine structure evolution of the mudstone under cyclic dynamic load disturbance are compared and analysed at multiple levels of water content,dynamic load rate and dynamic load intensity.（4）A damage model for mudstone under specific working conditions was constructed.Based on the assumption that the strength of mudstone micro-elements obeys the Weibull statistical distribution,a damage model for mudstone under cyclic action was firstly established,which better reflects the stress-strain relationship between the initial,intermediate and final loading and unloading of mudstone in the cyclic dynamic loading stage.Secondly,sensitivity analyses were carried out on the damage model parameters m and F₀.The results show that parameter m is the key influencing factor on the strength distribution characteristics of mudstone micro-elements,and parameter F₀ is the main influencing factor on the macroscopic strength of mudstone.Finally,the relationship between parameters m and F₀ and the loading strain in each cycle during the dynamic loading phase were clarified respectively,based on which the mudstone damage model was modified.（5）The fine-scale mechanical behaviour and damage evolution mechanism of mudstone under dynamic load disturbance are revealed.The fine-scale parameters of mudstones with different water contents were calibrated based on conventional single-load mechanical tests in laboratory mudstones,and reasonable dynamic loading rates were determined.The mechanical model of cyclic loading was constructed by numerical simulation of PFC particle flow against cyclic dynamic load perturbation tests,and an effective linkage between the fine-scale parameters of the contact model and the macroscopic properties of the specimens was achieved.The damage evolution of mudstone specimens under the influence of water content,dynamic loading rate and dynamic loading intensity was simulated,and the spatial and temporal distribution of cracks,particle cohesion and energy evolution during the loading process of mudstone under different conditions were analysed to explain the damage mechanism of mudstone from the fine viewpoint.This thesis has 64 figures,8 tables and 98 references.