MEASUREMENT AND RESEARCH OF SURROUNDINGROCK PRESSURE OF DEEP SHAFT

The whole depth measuring plan and its implementation method of surrounding rockmass pressure on the wall‘s of a shafts are described, which is in Suncun Coal Mine with a depth of 1 000 m. Then with the combination of data processing, it is discussed the effects of such factors on the distribution law of shaft surrounding rock pressures as rock quality, .burying depth,end effect due to excavating, rock stratum dip, shaft wall structure form and regression fornfulae relating to .the shafts‘ surrounding rock pressures as well as to several other factors. And finally,the measured results were verified according to the comparison between analyses of stress-strain of side-walls and side-wall strain measurements.     

Analytical large deformation shear strength for bolted rough discontinuous rock

Presented a new analytical model for studying the shear-tensile large deformation behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global shear strength for bolted joints under shearing-tensile loads. The analytical strength curves of bolts contribution on reinforced discontinuous rocks as the function of joint displacements or deformation angle of a bolt at rock joints was obtained. Based on Barton‘s equation on JRC roughness profiles, the theoretical shearing strength of bolted rough joints was also established. Test results on bolted granite and marble specimen confirm the validity of the analytical approach.     

THE FEM ANALYSIS OF SHAFT UNDER THE NON-AXIAL SYMMETRICAL LOAD

The changes of stress and strain around the shaft under the non-axial symmetrical loads during the excavation are analyzed with the finite element semi-analytical method based on the separated variable method. The change laws of deformation and stress of surrounding rocks are obtained. Moreover, an optimum method of the design and construction of the shaft lining is developed, which presents a new train of thought of the design and construction of the shaft and has important theoretical value and extensive application prospects.     

The improved neutral network and its application for valuing rock mass mechanical parameter

The artificial neutral network（ANN） has the ability that self-study and self-remember, its 3 layers BP network has been applied extensively, but sometimes because of serious multi-correlation between the variables, and a few observations while many variables, there usually will result into paralyzing in study, and the neutral network further development is restricted in the system to some extent. The partial least square regression（PLS） has its advantage of building the calculation model between the variables with strong multi-correlation, especially much effective on a few data and many variables. So a new and effective method-improved neutral network has been introduced-the neutral network based on the PLS. The results of example show the improved method has a few calculations and high accuracy, and provide a new way for valuing the rock mass mechanical parameters.     

A CUSP CATASTROPHE, PRECURSORS PATTERN ANDEVOLUTION PROCESS OF ROCKBUST OF COAL PILLARUNDER A HARD ROCK SUBJECT TO ELASTIC SUPPORT

The rockburst of the coal pillar under a thick hard roof stratum is modelled as the instability failure problem of coal pillars under strata subject to elastic support. The instability mechanism of rockburst is studied by applying cusp catastrophic theory. The effects of the stiffness ratio of the system and loads imposed on the system on the rockburst are explicated.The factors affecting rockbursts are discussed. Based on them, the “evolution process, the forewarning regularity and forewarning sings of rockbursts are studied. It is indicated that the subsidence velocity of roof stratum, which increases quickly and tends to infinity, is the forewarning measurable signs of the rockbursts of coal pillar.     

On the excavation-induced stress drop in damaged coal considering a coupled yield and failure criterion

Investigating the stress drop of abutment pressure is the key to a deep quantitative analysis of the discontinuous stress redistribution under mining.In the present study,uniaxial and triaxial compression tests are carried out separately to determine the bulk and shear moduli,the cohesion,and the internal friction angle of the coal samples.By extending the meaning of Mohr’s circle referring to yield stress instead of the maximum principal stress,a yield line is introduced to illustrate the stress drop of Mohr’s circle referring to yield stress instead of the maximum principal stress at the elastoplastic boundary.Furthermore,a theoretical solution of the stress drop as a function of the damage is proposed to investigate how the abutment pressure differs considering the yield line and failure line.In addition,applying the stress drop at the yield line in non-pillar mining,top coal mining,and protective coal mining shows that the damage has a nonlinearly positive influence on the stress drop.The results shows that the bulk modulus and internal friction angle have a more sensitive influence on the stress drop than do the shear modulus and cohesion.Finally,the stress drop is divided into a discontinuous stress drop at the yield line and a structural stress drop at the failure line.The stress drop is effective in describing the discontinuous stress redistribution and shows a clear difference in the movement direction of Mohr’s circle considering the unloading pressure.     

Effect of flow rates of gases flowing through a coal bed during coal heating and cooling on concentrations of gases emitted and fire hazard assessment

The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air.These concentrations differ in coal heating and cooling phase which was proven in the study.This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating(50–250°C)and cooling(250–35°C)phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed.The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines.Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index.In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane,ethylene,propane,propylene and acetylene,while in the cooling phase these ratios increased systemically.The effect of air(in heating phase)and nitrogen(in cooling phase)flow rate on the self-ignition index CO/CO2 was also determined.     

DEEP COLLIERY PRESSURE BUMPS AND ITS PREVENTIONS UNDER THE ACTION OF ABUTMENT PRESSURE

Based on field measurement, the relations was introduced between mining depth and the peak value places of abutment pressures in long wall face of the deep colliery with caving method to handle goaf, and the reasons and kinds of pressure bumps are analysed under the action of the moving and constant abutment pressures formed by the method of long wall caving or room and pillar mining, and the relative precautions were put forward to prevent the pressure bumps in deep mining.     

The concept, structure and characteristics of the distributed virtual coal-mine geographical environment

Distributed virtual coal-mine geography environment（CM-DVGE） researches the virtual reality simulation of coal-mine environment in cyberspace and the performance of coal production process. The goal is to deal with the practical safety problems of observation, analysis, design and training during the underground coal production process. This paper first probed into the evolution of CM-DVGE from a historical point of view, then respectively analyzed the characteristics of its physical progressive levels according to the cognitivd law and its logical structure of data on the basis of data flow, and concluded by putting forward the prospect of the application of CM-DVGE, thus enriched and developed the method of synthetic study of coal mine.     

MECHANISN ON PROGRESSIVE INTRUSION OF PRESSURE WATER UNDER COAL SEAMS INTO PROTECTINE AQUICLUDE AND ITS APPLICATION IN PREDICTION OF WATER INRUSH

This article proposes a water inrush mechanism of progressive intrusion of pressurewater up into the coal floor aquiclude according to injection tests and observations. A numericalmodel and a criterion of water inrush are established based on the mechanism. The theory is suc-cessfully used in predictions of water inrush.