Water-Solid Coupling Mechanism And Mechanical Properties Of Weakly Cemented Argillaceous Rock Mass With Recombined Structures

Argillaceous weakly cemented rocks were widely distributed in coal fields forming in late Cretaceous.The stability of surrounding rocks was declined heavily when excavated,due to its late diagenesis and argillaceous cementation between mineral particles,which was bad to mine coal safely and efficiently.The stability of argillaceous weakly cemented rock mass is not only related to the crustal stress,but also water migration caused by excavation.However,the disturbed argillaceous rock mass can realize structural reorganization under certain conditions,which is beneficial to the stability of surrounding rock.Therefore,it is of great significance to study the hydraulic properties of argillaceous weakly cemented rock mass and the mechanical properties of damaged mudstone after subjected to structure recombination for the stability control of surrounding rock.In order to reveal the deformation mechanism of argillaceous weakly cemented rock mass when subjected to excavation,the mudstone drilled from the floor of 3-3 coal seam in Xiyi Coal Mine in eastern Mongolia was taken as the research object,and laboratory tests,theoretical analysis and numerical simulation were combined to study the hydraulic properties of original rock and the mechanical properties of damaged mudstone after suffering from structure recombination.The main research contents and contributions of this paper are shown below:(1)The basic physical characteristics such as mineral composition,particle size distribution,moisture content and density of mudstone are revealed by XRD,screening,pycnometer and drying methods.The microstructure and pore distribution characteristics of weakly cemented mudstone are revealed by SEM,MIP and gas adsorption apparatus.The size effect and environment effect of mechanical response of mudstone are revealed by performing strength test on mudstone samples with different size and water content.The rock mass presents obvious weak cementation.(2)The weathering tests of mudstone under high/low surrounding humidity were carried out by using the high-precision weathering test system and low-field nuclear magnetic resonance(NMR)equipment,and the pore water migration under different environmental conditions were revealed.The water absorption test under different initial water content and lateral restraint is carried out by using self-designed water absorption test device.The effect of weathering on mechanical properties of weakly consolidated mudstone was revealed by strength test.(3)The feasibility of structural recombination of damaged mudstone is analyzed.Different types of structural recombination samples were made by using the reconsolidation device to simulate different engineering conditions in the field.The gravity impact type disturbance rheological test device was designed independently,and static and disturbance rheological mechanical tests were carried out to reveal the static and dynamic properties of the recombined mudstone.By changing the recombination conditions and applying certain impact,the stability of the reorganized rock mass in the disturbed area can be enhanced.(4)The mesostructures of reconstituted mudstone are revealed by means of the microscope.According to the process of structure recombination,a healing model of damaged mudstone is established,and the bearing mechanism of recombination mudstone is revealed.Based on the particle size distribution,porosity,particle contact characteristics and cementation strength of recombinant mudstone,a discrete element model of recombinant mudstone was established to reveal the influence of mesostructures on the mechanical properties of recombinant mudstone.Based on elastic-plastic theory,damage theory and thermodynamics theory,the coupling elastic-plastic damage constitutive model is established by constructing thermodynamic potential function,which can reflect the influence of recombination conditions,and the stress and deformation rules of recombination mudstone are revealed.(5)Taking roadways of the 1302 working face as the research subject,the measuring techniques such as geological radar and drilling core were used to reveal the large deformation of roadway surrounding rock.Combined with hydraulic properties and restructuring mechanical properties of the weak cementation mudstone,the deformation mechanism of the surrounding rock was revealed.Finally,control countermeasures of surrounding stress and environment combination are put forward.This dissertation includes 154 figures,41 tables and 205 references.