Mapping coalmine goaf using transient electromagnetic method and high density resistivity method in Ordos City, China

The research about subsurface characteristics by using transient electromagnetic method（TEM） and high density resistivity method（HDRM） were already conducted in Ordos. The objective of this research is to detect coalmine goaf areas based on rock resistivity. The data processing using wavelet transform, three point smoothing, RES2 DINV and Maxwell processing software to obtain 2D resistivity structure. The results showed that the layers with maximum resistivity values（30e33 U m on Line 1, 30e31 U m on Line 2, 32e40 U m on Line3） are founded at station 1e7, and 14e20 on Line 1,13e18 on Line 2, and 8e13 and 16e20 on Line 3 which is predicted as goaf layer, and the minimum resistivity values（20e26 U m of TEM, 45e75 U m of HDRM） at the other layers. This resistivity difference was caused by the geology and characteristics of the study area which is located close by the cleugh with rich coal, so the goaf area distinguishable with aquifer layer and coal seam. The results were also significant accidents and serious destruction of ecological environment.

Stability of roadways in coalmines alias rock mechanics in practice

This paper describes the procedures for design of supports and stabilization measures in the roadways.The procedures are based on the system developed in Ostrava-Karvina coal basin in Czech Republic.The calculation of load bearing capacity of roadway supports contains the period of roadway construction and mining in the vicinities,based on the size of the natural rock arch.The loading of supports during mining comes from a stress wave in the rock mass in the forefront of coalface and the caving area of mined-out panel.The input data for the calculation method are deduced according to in-situ measurements of convergence and displacement in the roadways.

New Discovery of Post-Magmatic Pyrite in Natural Coke at Yangliu Coalmine,Northern China

Objective Material exchange between magma and coal has recently received much attention, with published studies dedicated mainly to intrusion-related geochemical anomalies(An et al., 2017). It is found that magmatism not only alters the chemical compositions of coal seams, but also brings new minerals to natural coke. Although some studies have related magmatic water to secondary minerals in the natural coke, the mineral formation

A New Life Near Coalmine

New industries and an infusion of cultural heritage combine to offer opportunity for residents in

Consolidating the Coalmines

Shanxi Province Will readjust the structure of its coalmining industry to address a series of efficiency and environmental

Risk assessment of CO_2 injection processes and storage in carboniferous formations:a review

Over the last decades,people from almost all over the world have realized that it is necessary to quickly develop strategies for the control and reduction of greenhouse gases (GHG) emissions.Among various GHGs,carbon dioxide (CO2) is the most abundant GHG.Its underground storage involves less risk and lower levels of dangerousness.The paper briefly describes the most effective technologies available in the market for background processes to storage (capture and transport) CO2,as well as the more secure solutions for its storage,in particular for the geological storage in carboniferous formations.This paper also outlines the methodologies for the risk assessment involved in storage of CO2,with a particular focus on cases where the injection is made into unminable coal seams and in abandoned coalmines.Methodologies used for risk analysis are described in detail with particular emphasis on Bayesian network (BN).Some applications regarding the risk assessment of CO2 injection processes and CO2 storage in carboniferous formations and contamination of aquifers are presented and analyzed.Finally,based on the applications of BN,several conclusions are drawn.

Effects of CO2-water interaction with coal on mineral content and pore characteristics

There are a large number of abandoned coalmines in China,and most of them are located around major coal-fired power stations,which are the largest emission sources of carbon dioxide(CO2).Considering the injection of CO2 into abandoned coalmines,which are usually in the flooded condition,it is necessary to investigate the effect of CO2-water-coal interaction on minerals and pore structures at different pressures,temperatures and times.It reveals that the CO2-water-coal interaction can significantly improve the solubility of Ca,S,Mg,K,Si,Al,Fe and Na.By comparing the mineral content and pore structure before and after CO2-water-coal interaction,quartz and kaolinite were found to be the main secondary minerals,which increased in all samples.The structures of micropores and mesopores in the range of 1.5-8 nm were changed obviously.Specific surface areas and pore volumes first increased and then decreased with pressure and time,while both increased with temperature.By using the Frenkel-Halsey-Hill model,the fractal dimensions of all samples were analyzed based on D(s1)and D(s2),which reflected the co mplexities of the pore surface and pore volume,respectively.The re sults show that fractal dimensions had very weak positive correlations with the carbon content.D(s1)had a positive correlation with the quartz and kaolinite contents,while D(s2)had a negative correlation with the quartz and kaolinite contents.

Experiment and Simulation for Controlling Propagation Direction of Hydrofracture By Multi-Boreholes Hydraulic Fracturing

Hydraulic fracturing has been applied to enhance CBM production and prevent gas dynamical hazard in underground coal mines in China.However,affected by in situ stress orientation,hydrofracture can hardly continuously propagate within coal seam but may easily extend to the adjacent roof-floor strata,causing ineffective permeability enhancement in coal seam and increasing the risk of gas transfinite during mining coal.Thus,it is very necessary to artificially control the propagation direction of hydrofracture and make it well-aligned in large scale in coal seam.In this study,a method for controlling propagation direction of hydrofracture by multi-boreholes is investigated by theoretical analysis,laboratory experiment and numerical simulation.And this is followed by an on-site test in an underground coal mine to verify this method.Firstly,stress intensity factor at the hydrofracture tip is analyzed where pore pressure is taken into consideration.Results show that the pore pressure is able to increase the stress intensity factor and reduce hydrofracture propagation pressure.Based on this,a method of hydraulic fracturing using multi-boreholes to control hydrofracture direction is proposed.Afterwards,laboratory experiments are conducted to explore the impact of pore pressure on hydrofracture propagation.The experimental results agree with the theoretical analysis very well.Later on,a series of numerical simulations are performed to examine the influence of principal stress difference,the angle between assistance drillholes and the maximum principal stress,and the fluid pressure of the assistance drillholes on hydrofracture propagation.Finally,an on-site test in an underground coalmine is practiced where this proposed method is used to enhance the CBM production.Results show the scope of the hydro-fracture resulting from the multi-boreholes hydraulic fracturing method increases 2.7 times compared with that of conventional hydraulic fracturing.And gas production rate also increases 4.1 times compared with that of conventional hydraulic fracturing and 12.3 times compared with direct borehole extraction without fracturing.

Research on Robotized Advance Support and Supporting Time for Deep Fully Mechanized Excavation Roadway

To keep coal workers away from the hazardous area with frequent accidents such as the roof fall and rib spalling in an underground coalmine,we put forward the solution with robotized self-moving anchor-supporting unit.The existing research shows that the surrounding rock of the roadway has self-stability,and the early or late support is not conducive to the safe and reliable support of the roadway,so there is a problem of support opportunity.In order to study the supporting effect and the optimal supporting time of the above solution,we established the mechanical coupling model of surrounding rock and advance support,and investigated the surrounding rock deformation and advance support pressure distribution under different reserved roof subsidence by using the numerical simulation software FLAC3D.The results show that the deformation of surrounding rock increases and finally tends to a stable level with the increase of pre settlement of roadway roof,and when the pre settlement of roof is between 8-15 mm,the vertical pressure of the top beam of advance support reaches the minimum value,about 0.58 MPa.Based on the above research,we put forward the optimum supporting time in roadway excavation,and summarized the evaluation method based on the mechanical coupling model of surrounding rock-advance support.

Time-lapse geophysical technology-based study on overburden strata changes induced by modern coal mining

To study the impact of modern coal mining on overlying strata and its water bearing conditions,integrated time-lapse geophysical prospecting integrating 3D seismic,electrical and ground penetrating radar method were used.Through observing and analyzing the geophysical data variations of all stages of pre-mining,mining and post-mining as well as post-mining deposition stable period,impacts of coal mining on stratigraphic structure and its water bearing were studied and modern coal mining induced stratigraphic change pattern was summarized.The research result shows that the stratigraphic structure and the water bearing of surface layer during modern coal mining have self-healing pattern with mining time;the self-healing capability of near-surface strata is relatively strong while the roof weak;water bearing selfhealing of near-surface strata is relatively high while the roof strata adjacent to mined coal beds low.Due to integrated time-lapse geophysical prospecting technology has extra time dimension which makes up the deficiency of static analysis of conventional geophysical methods,it can better highlight the dynamic changes of modern coal mining induced overburden strata and its water bearing conditions.