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2007, 26 (5): 0-0 doi:

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2007-05目录

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EXPERIMENTAL STUDY ON ROCKBURST PROCESSES OF GRANITE SPECIMEN AT GREAT DEPTH

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2007, 26 (5): 865-865 doi:

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Rockburst is a nonlinear dynamical phenomenon when large amounts of energies release along free surface during excavation within underground rock masses at great depth. An experimental system has been designed to reproduce such a natural rockburst phenomenon by means of two processes，one is true triaxial stress loading process to simulate in-situ stresses；and the other is surface unloading process with unloading one direction stress fast to produce a free surface. During the process of one direction unloading，the stresses in other two directions are kept original or the loads in one direction increase with the other steady. Ten of granite plate specimens are tested. The relation curves of stress and time in the entire process of granite rockbursts are acquired based on the results of collected data. The experimental results show that the process of granite rockburst includes four stages—calm period，small grains ejection，rock flakes and /or grains ejection and collapse entire fracture. Rockburst intensity is defined by the ratio of maximum principal stress s1 to uniaxial compression strength sc. According to the time between the unloading and the beginning of the rockburst，three types of rockbursts are classified，instant rockburst，standard rockburst and delayed rockburst. The microcosmic characteristic of the granite after rockburst fracture is analyzed. Three fracture styles of rockburst are classified—local grains ejection failure，flake spalling failure and block collapse failure. The mechanism of rockburst is preliminarily discussed. It is of great importance to study rockburst mechanism and to prevent rockburst in deep coal mine engineering.

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ZONAL FRACTURING MECHANISM IN DEEP TUNNEL

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2007, 26 (5): 877-877 doi:

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The mechanical behaviors of rock mass in deep tunnel are different from those in shallow tunnel. The surrounding rock in shallow tunnel is classified into loose zone，plastic zone and elastic zone；while the surrounding rock in deep tunnel is classified into fractured zone and non-fractured zone，which occur alternatively. The mechanism of the alternative occurrence of fractured zone and non-fractured zone in deep tunnel is studied. It is assumed that the outer boundary of the deep tunnel is subjected to an in-situ far-field stress field，whose inner surface is subjected to an internal pressure which changes during tunnel excavation. As a result，the tunnel excavation process is related to dynamic problem. The motion equation expressed by displacement potential function is established，which determines the release of pre-existing stress upon excavation of the opening. The general solution of motion equations is obtained by using Laplace transform. Based on the elastic theory and boundary condition，the near-field stress redistribution and displacement field around circular opening induced by excavation are determined. If the elastic stress fields satisfy the failure condition of rock mass，failure of rock mass occurs. It results in the discontinuous displacement，and the fractured zone is formed，and the deformation localization occurs. On the basis of the deformation localization theory，the support reaction acted on the elastic zone is defined. Then，the fracture mechanics theory is applied to analyzing residual strength of the rock mass and the time of onset of fractured zone. Width and quantity of fractured zone and non-fractured zone are given. It is found from numerical results that the width and quantity of fractured zone and non-fractured zone depend on the strength of rock mass and the velocity of tunnel excavation. The quantity of the fractured zone increases with increase of tunnel excavation velocity. The width of the fractured zone decreases with increase of tunnel excavation velocity. The quantity and width of the fractured zone increase with decrease of the rock mass strength.

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DYNAMIC COMPREHENSIVE MONITORING AND ASSESSMENT OF STABILITY OF COLLAPSED AREA AFTER SUPPORTING IN MAIN TRANSPORT ROADWAY IN LINGLONG GOLD MINE

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2007, 26 (5): 886-886 doi:

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There are two parallel main transport roadways in Linglong Gold Mine in which one is old and the other is new. They are apart about 10 m and both cross the mined-out area of a stripe-shaped mineral vein. Due to illegal mining under the roadways，which leads to the safety pillar at the bottom of the roadways being mined out，serious collapsing deformation and subsidence appeared in both transport roadways. In order to maintain normal production and safe operation，the collapsed area of the old transport roadway was firstly treated to recover its normal transport capacity. Some special reinforcing techniques were used for the treatment. After the completion of the reinforcement，the working transport line was moved from the new transport roadway to the old one. At the meantime，the large scale of collapsed area in the new transport roadway was not treated due to financial difficulty，which would give strong influence on stability of the old transport roadway. In order to monitor the stability of the working transport roadway，multipoint displacement measurement，cross-section convergence measurement，leveling measurement，stress measurement and acoustic emission measurement were carried out. The monitoring results showed that the stability of the old transport roadway was quite well in 4 years after it was put into operation，which indicates that the support effect of the special reinforcing techniques used for the old transport roadway is excellent. Due to lasting influence of collapsed area in the new transport roadway，remarkable deformation and local damage were later found in the old transport roadway. An assessment on stability status and its developing tendency was made out based on coupling analysis of monitoring information obtained by different monitoring measures. It provided a reliable basis for decision-making of further reinforcement of the main transport roadway.

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RESEARCH ON SPACE-TIME ACTION RULE OF BOLT-NET-ANCHOR COUPLING SUPPORT FOR DEEP GATEWAY

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2007, 26 (5): 895-895 doi:

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Aiming at the characters of nonlinear mechanical process for surrounding rock in deep gateway excavation and support，the space-time action rule of bolt-net-anchor coupling support is researched by numerical simulation method and engineering application. The result indicates that，after the gateway surrounding rock is reinforced by the bolt-net coupling support，the optimal secondary support time to realize the space-time coupling among anchor，bolt-net and surrounding rock is that when the obvious deformation stage of the surrounding rock is completed or almost completed. Its main character is the transformation from high stress concentration to low stress zone through mobilizing the strength of inner surrounding rock by anchor coupling support. The gateway with bolt-net-anchor coupling support can meet the requirements of the stability control during gateway excavation and coal extraction.

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INVESTIGATION ON MECHANISM OF COAL MINE BUMPS BASED ON MESOSCOPIC EXPERIMENTS

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2007, 26 (5): 901-901 doi:

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The investigation on the mechanism of coal mine bumps is always one of the hot topics in the field of mining engineering and rock mechanical study all over the world. Coal mine bumps，which may expel large amounts of coal and rock into the face area and cause damages to underground openings and equipments，are sudden failures near the mine entries. Persistent bump problems not only threaten the safety of mine works，but also have caused the abandonment of large coal reserves. Researchers have made a large efforts to understand，anticipate，and control this kind of hazard and have achieved lots of helpful results. The characteristics and induced factors of coal mine bumps are briefly described based on the investigation of recent bumps accidents happened in China. According to the theory of non-equilibrium thermodynamics and dissipation structure，the process of energy accumulation and dissipation in the coal-surrounding rock system is discussed during the propagation of coal mine bumps. Moreover，a series of experiments are conducted to analyze the relationship between bump-proneness and microstructureal characteristics of coal. The process of coal mine bumps induced by propagation of fractures and deterioration of coal mass properties are also analyzed systematically.

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STUDY ON ELECTROMAGNETIC EMISSION CHARACTERISTIC FOR COAL SAMPLE DEFORMATION AND FAILURE DURING PRE- AND POST-PEAKING PHASES

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2007, 26 (5): 908-908 doi:

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The phenomenon of electromagnetic emission(EME) is caused during the deformation and failure processes of rock and coal. The experiments for seven types of rocks and coals such as hard coal，soft coal，concrete and so on collected from different collieries have been studied in the laboratories. The experimental results show that the EME strength is closely related to the rock and coal stress state. It usually increases with the stress increasing during the pre-peaking phase. The EME strength becomes most powerful when the stress level is 85%–95% during the pre-peaking phase. However，the EME strength rises firstly and then falls with the stress decreasing gradually during the post-peaking phase. During the post-peaking phase，the EME strength comes to the maximum value when the stress level is about 60% during the post-peaking phase，then falls with the stress deceasing. The EME index of rock burst tendency can be defined as the ratio of EME strength in post-peaking phase and that in the pre-peaking phase. It includes two indexes，namely，EME energy index and EME pulse index of rock burst tendency. Both the EME indexes have closely linear relation with the index of rock burst tendency used at present，i.e. the higher both the EME indexes are，the more the liability of rock burst is. It can be used as an EME index to evaluate the liability of coal and rock burst. The classifications of the two indexes for evaluating the liability of rock burst have been established based on the results of experiments. The EME index becomes an important parameter for the EME method to forecast the rock and coal burst tendency and danger. The research results lay a good foundation for rock and coal burst prevention.

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NUMERICAL SIMULATION OF INSTABLE FAILURE OF DEEP ROCK TUNNEL TRIGGERED BY DYNAMIC DISTURBANCE

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2007, 26 (5): 915-915 doi:

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The dynamic disturbance may trigger the instable failure of rock mass when the high elastic strain energy is accumulated in the deep underground rock mass；and in turn it leads to occurrence of rockbursts. By considering the effect of different lateral pressure coefficients，the failure process of deep rock tunnels，which is triggered by dynamic disturbance，is simulated in order to clarify the failure mechanisms of tunnels at depth. The numerical results indicate that the triggering action of dynamic disturbances is closely pertinent to the static in-situ stress condition and the waveforms of the dynamic disturbance. In general，it brings about greater influences on the stability of underground tunnels with the increasing magnitude and with the prolonged duration of dynamic disturbance. Therefore，it is of theroetical and practical significance to investigate the effect of dynamic disturbance on the stability of underground tunnels.

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STUDY ON MECHANICAL RESPONSE OF HIGHLY-STRESSED PILLARS IN DEEP MINING UNDER DYNAMIC DISTURBANCE

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2007, 26 (5): 922-922 doi:

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The mechanical response of highly-stressed pillars under the propagation of stress wave in deep mining is discussed by assuming that the pillars are disturbed by different peak values of dynamic stress. By using an explicit finite difference program FLAC3D，a model of numerical calculation is established for a deep mining pillar with dynamic disturbance under high stress. A cylinder pillar with a ratio of 4 between height and diameter is studied in the numerical calculation processes. The dynamic response characters of the pillar are obtained by changing the preloaded static stress. And then the effect of disturbance intensity on the stability of highly-stressed pillars is reflected by changing the different peak value of the dynamic stress wave. Through the numerical analysis of the pillar in deep mining，it is found that the stability of high stress rock mass is more distinctly influenced by the outside dynamic disturbance with the original static stress increased. Especially when the pillar is endured very high static stress，even a small dynamic disturbance may lead to its plastic destroying and result in a domino effect in the deep mining.

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RESEARCH AND APPLICATION OF IN-SITU STRESS MEASUREMENT
IN DEEP MINES

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2007, 26 (5): 929-929 doi:

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There are many kinds of in-situ stress measurement methods at present，which can be classified into mechanical，geophysical and geological structure information methods. Based on the analysis of the features of various stress measurement methods，a new method—hydraulic fracturing in-situ stress measurement with small borehole，which is suitable for rapid in-situ stress measurement in deep coal mine roadways，is introduced. The in-situ stress measurement principle，device and technical properties are introduced. Nine points of in-situ stress measurement have been completed in underground roadways in typical deep coal mining area，Xinwen coal mining area in China. There are 5 measurement points with buried depth more than 1 000 m，and the maximum is 1 220 m. The measurement results indicate that：(1) there are 7 measurement points with the maximum horizontal principal in-situ stress more than the vertical principal stress；(2) the value of the maximum horizontal principal stress amounts to 42.1 MPa；(3) the ratios of the maximum horizontal principal stresses to the vertical principal stress are 1.004–1.550；and (4) the in-situ stress field in Xinwen coal mining with buried depth more than 1 000 m is dominated by horizontal stress；and the orientations of the maximum horizontal principal stresses mainly concentrate on N3°E–N43.5°W. The in-situ stress states and the distribution law in the measured area have been determined through the measurement results. It is also proved that the hydraulic fracturing in-situ stress measurement with small borehole can provide an effective and rapid stress method for deep mines and can offere reliable basic parameters for roadway layout and support design.

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SOFTWARE SYSTEM FOR LARGE DEFORMATION MECHANICAL ANALYSIS OF SOFT ROCK ENGINEERING AT GREAT DEPTH

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2007, 26 (5): 934-934 doi:

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Up to now，there is no finite element software including nonlinear large deformation theory based on S-R decomposition theorem，in which the deformation gradient F is decomposed into the addition of the deformation and the rotation by a co-moving coordinate system method. In this work，such a software system waw developed，which is named as A Software on Large Deformation Analysis of Soft Rock Engineering at Great Depth. Two work groups，worked together on the software by using finite element program generator(FEPG) developed by FEGEN Software Company. The software has the following features：(1) it includes large deformation theory based on S-R decomposition theorem first time as well as one based on polar decomposition theorem for comparison，the latter is included by most commercial finite element software；(2) three design methods for nonlinear mechanical problem，i.e. countermeasure design，procedure design and parameter design，are fulfilled here for large deformation analyses；(3) it includes generally used elastoplastic constitutive models for geomaterials and element types for supports，and therefore is fit for large deformation mechanical analyses for slope，foundation and underground engineering；and (4) it has a copyright of our own country. At present，the interface of the software has accomplished and programs of elastic and elastoplastic constitutive models based on two large deformation theories in two-dimension have been fulfilled，tested and implemented into the interface. Representative numerical examples confirm the rationality of the programs. The software will be a useful numerical tool for large deformation analyses and nonlinear mechanical design for soft rock engineering at great depth.

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STUDY ON CRACK DYNAMIC PROPAGATION PROCESS OF ROCK SAMPLES BASED ON ACOUSTIC EMISSION LOCATION

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2007, 26 (5): 944-944 doi:

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Acoustic emission(AE)，which is produced by the micro-cracks occurrence or growth，is a ubiquitous phenomenon associated with brittle fracture in many materials. AE technique can be used to monitor the micro-cracks development in the rock sample continuously and in-real-time，which is better than other methods. AE location technique is employed to study rock failure process. It is investigated using granite samples with different precut cracks；and AE sensors are mounted on the surface of the sample. A Geiger location algorithm allows AE event location from first arrival times to be determined by AE sensors，which is applied to study the crack initiation and propagation process，also to analyze the crack spatial evolution mode with stress changing during the total loading process. The experimental results show that AE activity represents different characters with stress-strain changing during the total loading process；the quantity of the AE events is very little from the initial loading to crack initiation；when the initial crack generates，AE events apparently increase；AE events are in quiet period after crack initiation up to the time before crack propagation；AE activity sharply increases from crack stable propagation up to crack unstable propagation，especially in crack unstable propagation step，AE events reach to the most quantity in the division strain. There is “void space” of AE events during the AE location results；the “void space” of AE events is the position of macroscopic crack breakthrough，which can be used to predict the crack breakthrough position of rock samples. Meanwhile，AE location results are also direct reflection of interior stress field propagation process. AE location results also reflect directly the spatial position，direction and spatial curved face of crack propagation in the rock sample，which is very significant to study the mechanism of rock failure.

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COMPARISON OF THEORETICAL AND EXPERIMENTAL ANALYSES OF DYNAMIC CHARACTERISTICS OF BLOCK ROCK MASS

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2007, 26 (5): 951-951 doi:

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Because the blocks in deep rock mass exist in the form of tectonic order，therefore continuous medium mechanics as the analytic foundation of rock mechanics lacks basis. It is very important to explain and testify the experimental phenomena of ultra-low friction，because the influence of ultra-low friction among rock mass is the main reflection of the dynamic characteristics of block rock mass. The law is referred to describing the experimental phenomena of ultra-low friction and organizing the experimental data；then the dynamic model of block rock mass is established；and the theoretical and the numerical values are worked out to testify the correctness of ultra-low friction. By making such effort，the conclusion has been drawn as follows：the redistribution of vertical force and transformation of coefficient of kinetic friction are the fundamental factors of ultra-low friction. Furthermore，the tendency of experimental phenomena is consistent with that of the numerical results. The capability of storage and energy conversion is related with friction coefficient for the deep rock mass with tectonic level. A new branch of rock mechanics，nonlinear deep rock mechanics，is established. According to the static and dynamic characteristic phenomena and the characteristics of deep rock，the tectonic，deformation and failure problems of deep rock such as the block structure feature，the state of high earth stress，the stored energy and the nonlinearity，discontinuity and incompatibility of deformation，are suggested.

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STUDY ON SUPPORTING DESIGN FOR LARGE AREA SERIOUS ROOF CAVING OF DEEP SOFT ROCK ROADWAY IN XING¢AN COAL MINE

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2007, 26 (5): 959-959 doi:

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The support countermeasure of common small area roof caving has been studied and mastered，but the large area serious roof caving is difficult to be controlled，because the support method is very complicated and needs further study. By field investigation，the roadway of loaded-car line in Xing¢an Coal Mine was seriously destroyed. The length of roof fall is about 150 m and the maximum height of roof caving is 8.6 m. Supporting condition of serious roof fall in Xing¢an Coal Mine loaded-car line was investigated and studied by laboratory test and theoretical analysis. The cause of its failure was summarized as follows：(1) the intensity of wall rock is low；(2) original support is irrational；(3) water effect；(4) road way is deep；(5) structure stress effect. According to geological condition，rock character and destruction features，deformation mechanism of soft rock were ascertained as swell under high stress，and the supporting technology of double-arch flexible layer with rigid gap was put forward. The roadway is formed into double-chamber in space. Engineering effects indicate that double- arch flexible layer truss technique，as an effective method can be used to control the distortion of surrounding rock at the intersection successfully.

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EXPERIMENTAL STUDY ON ACOUSTIC AND THERMAL INFRARED CHARACTERISTICS OF BUMP-PRONE COAL

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2007, 26 (5): 965-965 doi:

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The acoustic and thermal infrared(TIR) characteristics of bump-prone coal are briefly described with different loading tests. The experimental system is designed，which is composed of the TIR observation system，the stress and strain measurement system and the acoustic emission monitoring system. It can be used to achieve different kinds of forewarning messages before the failure of rock or coal samples. The uniaxial compression loading test and the cyclic loading test are carried out to observe the features of TIR，acoustic emission and strain forewarning messages. Moreover，the response speed and the sensitivity of different monitoring systems to the cracking events in the samples are also studied under different loading conditions；and the physico-mechanical characteristics of bump-prone coal are obtained. The statistical investigation on the forewarning stress points is conducted based on the TIR images，infrared radiation temperature，acoustic emission and strain data. The analytical results show that the stress of ninety percent of strength should be regarded as the stress-caution-point for the failure of bump prone coal，which is much higher than the stress of seventy percent of strength as the stress-caution-point for the general coal samples. So it is more difficult to forecast the failure of the bump-pone coal under different loading conditions.

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STUDY ON EFFECT OF GEOELECTRIC FIELD ON SEEPAGE PROPERTIES OF LEACHING SOLUTION IN FRACTURED ROCK BLOCK

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2007, 26 (5): 972-972 doi:

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According to the properties of influences of geoelectric field on solution seepage，a model of electro-dynamic seepage has been established；and the influences have been investigated through experiments. The results indicate that it is obvious that the geoelectric field affects the seepage properties；and the electro-dynamic seepage properties are affected by factors such as the intensity of geoelectric field，the permeability of rock mass，the characters of leaching solution and so on. Under the same pressure gradient，the seepage velocity of leaching solution well increases with the intensity of positive electric field，and decreases with the negative electric field. The seepage diffusibility of leaching solution and its wetting ability to fractured rock mass can be enhanced or weakened by the electric field.

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NUMERICAL SIMULATION OF COAL-BED METHANE
SEEPAGE FLOW UNDER MULTI-WELL EXPLOITATION CONDITIONS

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2007, 26 (5): 977-977 doi:

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Adoption of multi-well mining technology to exploit coal-bed methane is still under the preliminary trial stage in China. Theoretical research on the multi-well mining technology is also insufficient，fortunately the numerical simulation can be able to provide certain theoretical guidance for coal-bed methane multi-well exploitation. The model of permeable equation considering multi-well exploration conditions is set up；and the pressure field distributions under single well and multi-well exploration conditions are simulated with finite element method. The influence of well space changes on the distribution of pressure field is studied under the well group exploration conditions；and the velocity field of coal-bed methane distribution under nonlinear seepage condition is investigated with the coal-bed methane permeable equation. The conclusions display the change rule of the seepage field and the coal-bed methane production under the multi-well exploitation conditions，and the numerical simulation result demonstrates the superiority of multi-well exploitation. The achieved results can provide significant references to the enhancement of the coal-bed methane output and coal-bed methane industrialization mining.

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ELASTOPLASTIC ANALYSIS OF CRACKED SURROUNDING ROCKS IN DEEP CIRCULAR OPENINGS

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2007, 26 (5): 982-982 doi:

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With the increase of mining depth of a lot of coal mines，exerted by the high in-situ stress，the surrounding rocks in openings is fractured frequently. At the same time，the region of the cracked surrounding rocks enlarges；and the surrounding rocks re-crack. For a long and circular mine opening，the surrounding rocks are divided into three regions，i.e. the cracked region，the plastic region and the elastic region. With Mohr- Coulomb yield criterion，the mechanical behavior of the surrounding rocks is simulated by an elastoplastic model. The closed-form analytical solutions for the stress，strain and displacement in the three regions are derived in a theoretically consistency way by using a non-associated flow rule. According to the conditions that the stresses are continuous at the elastoplastic interface and that the radial strains are continuous at the plastic-cracked interface，the computational formulae to determine the radii of cracked and plastic regions are obtained. Finally，an example is analyzed to show the characteristics of stress and strain distributions in the cracked and plastic regions and the influence of cracked region radius on them. It provides theoretical foundations for the stability analysis of mine openings and reinforcement of the cracked surrounding rock.

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DEFORMATION AND DAMAGE MECHANISMS AND COUPLING SUPPORT DESIGN IN DEEP COAL ROADWAY WITH COMPOUND ROOF

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2007, 26 (5): 987-987 doi:

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As the mining depth increasing，geological and mechanical conditions of roadway become more complicated compared with those in shallow roadway. Consequently，the nonlinear mechanical phenomena occur with high frequency，which brings about great difficulties for deep engineering support during excavation and mining. These problems caused by the deep mining engineering are the focuses in the fields of mining engineering and rock mechanics. A lot of achievements have been obtained by scholars through theoretical study，experimental test，and in-situ test. The loose and cracked compound roof of working face 2442 in Jiahe Coal Mine is difficult to control by using traditional support measures which increase the walls shrink and the floor heave and greatly affect the normal excavation and safe production. Based on the in-situ investigation，experimental test，analysis of engineering geological conditions，geomechanical evaluation and numerical simulation，the deformation and damage mechanisms of the roadway are analyzed；and then the bolt-mesh-cable coupling support design is put forward. The result of in-situ test shows that the new design can ultimately guarantee the stability of deep coal gateway. The design scheme of bolt-mesh-cable coupling support is feasible and efficient for the stability control of surrounding rock in deep mining engineering.

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NUMERICAL SIMULATION OF DEEP COAL-BED METHANE MULTI-WELL EXPLOITATION UNDER FLUID-SOLID COUPLING

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2007, 26 (5): 994-994 doi:

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Aiming at the characteristics of deep coal-bed considerably low permeability and coal-bed methane non-Darcy seepage transport and obvious fluid-solid interaction because of the considerably high porosity pressure and in-situ stress in the deep coal bed methane exploitation，a fluid-solid coupling mathematical model of gas-water two-phase flow with low permeability is established based on characters of deep low permeability coal-bed and properties of methane flow. Deep coal-bed methane multi-well exploitation with low permeability is researched systematically using fluid-solid coupling model by numerical simulation. The change laws of reservoir pressure，gas-water production，pressure drop funnel，water saturation，coal-bed methane concentration and wells interference are obtained under different permeabilities and different well spaces. The numerical simulation results of coupling interaction of higher geostress and coal bed deformation condition are smaller than the results obtained by fluid-solid coupling model with consideration of the influence of reservoir deformation when geostress are smaller than those without consideration of the fluid-solid coupling. The effect of fluid-solid coupling on the output of deep coal-bed methane must be taken into account；and the reasonable production system and well scheme should be established to guarantee minimum damage of the reservoir permeability. The results have important significances for deep coal-bed methane exploitation.

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STUDY ON ROCKBURST MONITORING AND ORIENTATION SYSTEM AND ITS APPLICATION

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2007, 26 (5): 1002-1002 doi:

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In order to ascertain time，position and magnitude of rockburst occurrence，considering the actual situation of coal mine，rockburst monitoring and orientation system is developed. This system can monitor destructive rockburst in kilometer dimension of mining area and has the independent intellectual property right in China. Four substations composed of three-component acceleration sensors are laid in the mining area floor，collecting vibration wave signal. In order to guarantee the time accuracy of rockburst data of four substations，GPS network time service can be achieved. Based on the characteristics analysis of the vibration wave frequency and amplitude，rockburst wave is identified automatically；and vibration signals of shooting and so on are eliminated. The rockburst signals of every substation are transmitted to the center measuring and controlling computer by the network. The center measuring and controlling computer manages every substation by remote control，monitoring working condition of every substation. At the same time，by the center measuring and controlling computer，the data is analyzed and managed；the time of rockburst occurrence is calculated；and the rockburst magnitude is computed by duration of rockburst wave. Three methods for computing the location of rockburst are adopted. This system provides a basis for prompt and accurate disaster relief and decrease of loss in the mine. At the same time，the statistic analysis of the time，frequency，location and magnitude of rockburst occurrence is carried out every day with the system；and the future trend of rockburst occurrence can be forecasted. The operation of this system in a year shows that the monitoring results are fully identical with the actual rockburst；and the orientation results are smaller than the error of upper limit.

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A DISTANCE DISCRIMINANT ANALYSIS METHOD FOR PREDICTION OF POSSIBILITY AND CLASSIFICATION OF ROCKBURST AND ITS APPLICATION

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2007, 26 (5): 1012-1012 doi:

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Rockburst is one of the main engineering geological hazards at deep high geostress zone and is influenced by many factors. The prediction of possibility and classification of rockburst are important issues in many underground engineering. Based on the principle of Mahalanobis¢ distance discriminant analysis(DDA)，a distance discriminant analysis model to predict the possibility and classification of rockburst is established. The main control factors of rockburst，such as values of in-situ stresses sq，uniaxial compressive strength sc and uniaxial tensile strength st of rock，elastic energy index of rock Wet，are chosen in the analysis. Three discrimination factors including sq /sc，sc/st and Wet are regarded as the discriminant factors of the DDA model. A series of underground rock projects in domestic and abroad are taken as the training and testing samples；and the ratio of mistake-distinguish is considerably low zero after the DDA model is trained. Rockbursts of Qinling Tunnel along Xi¢an—Ankang Railway and Dongguashan deep-buried hard rock mine are used to verify this model. The results show that the DDA model can be used to predict the possibility and classification of rockburst in deep underground engineering；and the prediction accuracy is acceptable.

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STUDY ON RULE OF BLOCK DEFORMATION AND MOVEMENT UNDER EXPLOSION LOADS

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2007, 26 (5): 1019-1019 doi:

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As a geological body，rock is considered as discontinuity. The mechanism of block deformation and movement is studied firstly. Theoretical methods to calculate the block deformation and movement are summarized by introducing theoretical calculating model. Secondly，the basic rules of block deformation and movement under explosion loads are studied by numerical simulation；and the process of block deformation and movement is shown. At last，the effects of correlative parameters are discussed. These parameters include the distance from explosion center，the thickness of interlayer and the strength characteristic of filler in the fault.

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STUDY ON PHYSICAL SIMULATION OF JOINTED ROCK MASS AND ULTRASONIC EXPERIMENTS

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2007, 26 (5): 1026-1026 doi:

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The mathematical-physical model is established based on the elastic wave equations of three-dimensional anisotropy media. The different jointed rock masses with typical joint sets are simplified as transversely isotropic media and monoclinic anisotropic media. When the elastic waves propagate through joint sets，the elastic wave velocity in different directions can be calculated. According to the mathematical-physical model，physical model of jointed rock mass is made. The related testing system of ultrasonic velocity is set up and the ultrasonic experiments are conducted. Experimental results show that the ultrasonic velocity is sensitive to the influence of joint sets and changes a lot when propagating through joint sets. In the ultrasonic experiment on physical model of monoclinic anisotropic media，the results are much complicated than those of experiment on physical model of transversely isotropic media. If survey points are located correctly，the existence and direction of joint sets can be recognised. The relationship between the elastic wave velocity and the distribution of joint sets in physical model is analysed. In practical engineering，the dominant orientation of joint sets and rock mass anisotropy can be judged using the ultrasonic tests. The results can provide abundant data for the practical engineering.

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MONITORING AND ANALYSIS OF FRACTURE DEVELOPMENT IN PRE-SPLITTING HOLE OF CAVE INDUCEMENT OF ROOF

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2007, 26 (5): 1034-1034 doi:

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Based on continuous mining technology，cave inducement of roof is a nontraditional，safe and high-efficiency method，which is widely used in mining of inclined，gently inclined large-scale barren orebody and processing technique to mined stope. In order to study the relationship between the evolvement of fracture and discontinuity in rock mass and mechanism of cave inducement of rock mass，the monitoring on development of fracture on the wall of pre-splitting boreholes in cave inducement of roof is put into practice by panoramic borehole television. According to monitoring results，the development situation of original fracture and discontinuity in rock mass under the artificial disturbance is reflected by the images. Consequently，a qualitative and intuitional evaluation to cave inducement can be provided；and the controllability of cave inducement roof is increased. The monitoring and analytical results show that a fractured zone comes into being in the range of 5 m in the direct roof during the cave inducement process. Relatively，the surrounding rock represents fragmentation circumstance. A ring-shaped fracturing zone is formed in the range of 10 m from the roof simultaneously. Then，with the farther development of quantity and density of fracture，the cave inducement of roof is formed ultimately.

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COMPREHENSIVE ANALYSIS AND APPLICATION STUDY ON GROUND DEFORMATION PREDICTION PARAMETERS OF FULLY-MECHANIZED MINING WITH SUBLEVEL CAVING

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2007, 26 (5): 1041-1041 doi:

[PDF] 271 KB (1015)

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In order to offer more scientific references to ground movement and deformation prediction of fully- mechanized mining face with sublevel caving in Yanzhou mine area，based on field survey data and through theoretical study and mathematical analysis，some conclusions are drawn as follows. A formula for relationship between subsidence factor and the ratio of mining width to basement rock thickness is obtained；and a series of formulas for relationships among displacement factor，tangent of main effect angle，displacement distance of inflection point and the ratio of mining width to mining depth are also achieved. It is pointed that，when mining width increases to a certain value(the ratio of mining width to basement rock thickness is about 1.0)，the subsidence factor will increase obviously. As the ratio of mining width to mining depth increases，the change of displacement factor decreases firstly and then increases. When the ratio of mining width to mining depth is about 0.5，the displacement factor reaches to the minimum value. The modified formulas of subsidence prediction value over boundary of fully-mechanized mining face with sublevel caving，which is applicable to Yanzhou mine area，are also gained.

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DETESTABILITY MECHANISM OF DEEP ROCK LATENT CRACK
USING ELECTROCHEMICAL METHOD

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2007, 26 (5): 1048-1048 doi:

[PDF] 402 KB (1196)

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There are many different mechanical phenomena in deep rock engineering comparing with shallow- buried rock engineering. To research the microcrack of deep rock，the relative size and stable conditions of microcracks are analyzed；and the microcracks can be classified into latent crack and overt crack with the reference of the static and variable states. The mechanical phenomena of nucleation and expansion of deep rock microcracks are studied. Based on the basic theory of electrochemistry，the interface properties of rock microcrack and its solution are analyzed；and the electric double layer structure composed of rock microcrack and solution is studied. The change law of the electric double layer capacitance and its macroscopic impedance due to expansion of rock crack are researched. The relations between the specific parameter of rock AC impedance spectroscopy and the nucleation and expansion of rock microcrack are investigated. The result shows that the electrochemical method is effective to test expansion of rock crack. It is a new method to study rock fracture behavior.

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STABILITY ANALYSIS OF SURROUNDING ROCK OF MULTI-ARCH TUNNEL BASED ON COUPLED FLUID-SOLID THEOREM

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2007, 26 (5): 1056-1056 doi:

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Along the freeway from Changde to Jishou in Hunan Province，some large span multi-arch tunnels have been built to meet the need of engineering. Based on the coupled fluid-solid theorem，numerical analysis for the stability of surrounding rock has been done with fast Lagrangian analysis of continua in three-dimension(FLAC3D) by considering the multiple factors including surrounding rock classes，tunnel depths，groundwater tables，construction methods and initial supporting systems. According to the numerical analysis of surrounding rock with classes III，IV，V under all kinds of calculation cases，the results of principal stresses，displacements，plastic zones，pore pressure distribution and the mechanical characters of supporting system including anchors and shotcrete，have been obtained. The seepage mechanism of multi-arch tunnel has been discussed；and the pore pressure distribution of deep-buried tunnel has been studied. The achieved results are successfully applied to guidance of the tunnel construction for waterproofing of this freeway. Furthermore，the study results can provide a theoretical basis for the design of multi-arch tunnel in aquifer strata.

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STUDY ON PHYSICAL SIMULATION OF FULL-SEAM MINING FOR A
20 m VERY THICK AND MEDIUM HARD SEAM BY SUB-LEVEL CAVING MINING WITH HIGH BOTTOM CUTTING HEIGHT

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2007, 26 (5): 1065-1065 doi:

[PDF] 476 KB (1393)

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Based on the condition of No.6–1 coal seam of Suancigou Coal Mine，the caving characteristics of the top coal and roof，the bulk increase property and the stacking angle of the caved rock behind the powered support，the working resistances of the powered support and the coal face recovery etc. of the fully-mechanized sub-level caving full-seam mining with high bottom cutting height for the 20 m very thick and medium hard seam have been studied by 1∶30 physical simulation. Some conclusions can be drawn as follows. (1) It is feasible in technology to use full-seam mining for the 20 m very thick and medium hard seam by fully-mechanized sub-level caving mining with high bottom cutting height. (2) According to the top-coal caving and drawing characteristics，the mining process of working face may be divided into the initial mining stage，the transition stage and the top-coal normal caving stage in which the face coal recovery ratio n increases in a logarithmic form within certain distance of the face advance. (3) The coal face recovery may reach to 75% in the normal top-coal caving stage and the face coal recovery changes with the roof rock beam breaking periodically. (4) There are the phenomena of the full top coal cantilevering towards mined-area and then suddenly cutting down over the bottom working face wall. The front-rear stability of the powered support must be considered when designing and electing the support. (5) In order to ensure safety and top coal caving in time，the measures of pre-blasting or water pre-infusion to weaken top coal should be adopted.

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SUPPORT TECHNOLOGY OF POLYPROPYLENE FIBER CONCRETE SHOTCRETE LAYER AND ITS APPLICATION TO GUQIAO COAL MINE

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2007, 26 (5): 1073-1073 doi:

[PDF] 230 KB (1194)

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According to mechanical principle of polypropylene fiber concrete structure，the applicability of polypropylene fiber concrete in the coal mine spray tunnel protection is researched. Combined with the typical anchor spray tunnel of Guqiao Mine，the reasonable proportion，tension，resistance of compression and shear of polypropylene fiber concrete spray layer are completed by laboratory test. Compared with the general concrete spray layer，the stress distribution is more homogeneous and the yield capacity is better. Industrial experiment shows that the tensile strength and toughness of the polypropylene fiber concrete spray layer are higher than those of general one. The rebound of the polypropylene fiber concrete is low and the construction technology is simple. Therefore，it has wider application.

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徐光苗博士论文摘要

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2007, 26 (5): 1078-1078 doi:

[PDF] 104 KB (1490)

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徐光苗博士论文摘要

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孔位学博士论文摘要

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