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2005, 24 (08): -0 doi:
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2005-08期目录

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ANISOTROPIC YIELD CRITERION FOR JOINTED ROCK MASSES BASED ON A TWO-ORDER DAMAGE TENSOR

2005, 24 (08): -1275 doi:
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In order to include the geometrical characteristics of jointed rock masses in its constitutive relations，a two-order tensor is adopted as damage variable. Joint connectivity at any direction of jointed rock masses is expressed as a continuum function of its normal vector and the damage tensor. Consequently，shear strength parameters of jointed rock masses，i.e.，friction factor and cohesion are weighted average of those of entire rock and entire fissures respectively according to joint connectivity，and implicit anisotropic yield criterion for jointed rock masses can be obtained through the Mohr-Coulomb yield condition for plane in every direction. In principal stresses space，the damage tensor is divided into two parts：the isotropic part and deviatoric part. According to rigor analytical solution to critical normal vector of the most disadvantage section for isotropic damage tensor，explicit yield criterion for isotropic joint rock masses is obtained，and an approximate analytical solution with one order precision to critical normal vector of the most disadvantage section for general damage tensor is obtained. The explicit anisotropic yield criterion for jointed rock masses is a form of quadratic equation of principal stresses in which its coefficients are functions of the damage tensor. The anisotropic yield criterion can be fully determined by the two-order damage tensor which has six independent variables，i.e.，the three principal values of damage tensor and the three Euler angles which represent the relations of principal vectors of damage tensor and those of principal stresses. In four examples，how the six variables affect the anisotropic properties of rock yield stresses in principal stresses space is analyzed by figuring out yield curve in deviatoric plane and meridian plane through the implicit and the explicit anisotropic strength criterion respectively. It is concluded that the explicit anisotropic yield criterion for jointed rock masses which is obtained by approximate analytical method has high precision.

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STUDY ON CHEMICAL DAMAGE EFFECT AND QUANTITATIVE ANALYSIS METHOD OF MESO-STRUCTURE OF LIMESTONE

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2005, 24 (08): -1283 doi:
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The change of rock meso-structure under chemical corrosion is the reason of change of rock mechanical properties，so it is important to study chemical damage effect of rock meso-structure and chemical damage quantitative analysis method. By the analysis of the change of rock meso-structure under chemical corrosion，corrosive and damage effect of chemical solutions on rock meso-structure is studied. Based on the variety of void ratio，computational formulation of chemical damage variable is set up，and the calculation method of damage measurement parameter is put forward. The chemical corrosive damage test in different time segment can continuously be performed on the same sample without destruction when applying this method. So error caused by the difference of rock microstructure of different samples can be avoided.

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ANALYSIS OF BREAKAGE AND COLLAPSE OF THICK KEY STRATA AROUND COAL FACE

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2005, 24 (08): -1289 doi:
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The regular behavior of weighting and caving of well-layered strata around coal face，with many thin overlying layers，is studied，and the rock pressure caused by the caving is relatively easy to control. But the caving and rock pressure of very thick sand overlying strata，the thick key strata，is very complicated and needs further study. The breakage and collapse of thick key strata(super thick roof of sand rock ) around coal face，with real geological conditions from a coal mine borehole columnar section，is studied by a computer grogram，rock fracture process analysis(RFPA). The results show that there are basic differences of the breakage and collapse between thick key strata and thin strata (or long beams). The shape of the first breakage and collapse of thick key strata is an arch，and the periodic breakage and collapse is in short blocks with different lengths. The roof of thick key strata weights stochastically，and the effects on the coal face support are different. The sliding of large blocks，which is the most dangerous of rock weighting to the support observed in this paper，is a new and severe challenge to the rock pressure control. The results can provide theoretical reference for mining design and strata control.

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RESEARCH ON CHAOS AND INTELLIGENT IDENTIFICATION OF ACOUSTIC EMISSION IN ROCK MASS

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2005, 24 (08): -1296 doi:
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Acoustic emission(AE) in rock specimen was tested under loading and breakage，and AE in rock engineering was surveyed. Action laws of AE in rock mass were researched with chaotic kinetics，and chaotic attractors of AE in different stages were calculated during deformation and breakage in rock engineering. By coupling chaos with neural network，a prediction model of AE was established. According to characteristics of AE in different stages，an intelligent identification model for analyzing stability in rock engineering was created. Research results show that there are four different stages in AE activities，i. e.，stable period，earlier active period，intensely active period，and reversal period. Breakage occurs in the reversal period with abnormal AE and diminishing value of chaotic attractor. In-situ case verifies that chaotic kinetics can reflect the characteristics of and the intelligent identification model proposed in this paper is able to predict and analyze stability in rock engineering，especially in deep mining.

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PENETRATION ANALYSIS OF LONG ROD PROJECTILES ON ROCK TARGETS

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2005, 24 (08): -1301 doi:
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A cylindrical cavity expansion model for rock targets with penetration of long rod projectile is presented by using the unified strength theory which consists of a generic of convex piecewise linear yield criteria. The relationship of cavity expansion pressure and cavity expansion velocity is obtained. The analytical equation of penetration depth is given and the penetration depth of long rod projectiles when impacting rock targets at 450 ～
1 400 m/s is calculated. The results are compared with experimental data. The influences of the weighting coefficient b of the unified strength theory on the penetration depth are investigated.

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APPLICATION OF STEREO-ANALYTICAL METHOD FOR BLOCK THEORY TO THE STABILITY OF LONGTAN HYDROPOWER STATION UNDERGROUND POWER-HOUSE

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2005, 24 (08): -1308 doi:
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There are a lot of discontinuous planes in rock mass of Longtan hydropower station underground power-house，so it is of practical value to make certain whether there are unstable blocks on excavation planes where faults and joints interlace with each other. Block theory is an effective and reliable engineering analysis method for the stability of faulted and jointed fractured rigid rock masses. This paper deals with the stability of Longtan hydropower station underground power-house with stereo-analytical method for block theory on the basis of detailed investigation of its rock mass data，and systematically calculates the numbers of possible moveable rock masses which are induced by all rock discontinuous plane and every excavation plane of cavern groups. The obvious statistical distribution result is obtained to offer basis on designing effective reinforcement option.

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THEORETICAL ANALYSIS AND EXPERIMENTS OF ROCK FRAGMENTATION UNDER COUPLING DYNAMIC AND STATIC LOADS

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2005, 24 (08): -1315 doi:
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According to the fracture characteristics of rock under indenter，the relations between the length of the median，radial and lateral cracks and the loading parameters of impact hammer，impact speed and static pressure were determined. The cutting effects of rock influenced by impact frequency were also analyzed. On the multifunctional testing device，the indentation and cutting test under coupling dynamic and static loads were conducted on granite. Experimental results show that the cutting effects of rock can be improved greatly under the combined loads，the special energy consumption of rock fragmentation varies with the ratio of impact point space to cutting depth，and has an optimum value at which the cutting effects of rock are optimum. The reasonable method of fragmenting rock is that enough large crack area is caused firstly by impact load and then rock is cut by cutting load and static load. High energy，high frequency and small impact space have good effect on cutting the brittle hard rock.

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RESEARCH ON ANCHORAGE CALCULATION METHOD FOR UNSTABLE ROCK

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2005, 24 (08): -1321 doi:
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As one of the typical disasters in the Three Gorges reservoir region，unstable rock can be classified as three types in views of unstable mode，i.e.，fall unstable rock，slide unstable rock and topple unstable rock with failure mechanism of shear，compression-shear and tension-shear respectively. Support，anchorage and filling etc. are used extensively in controlling of unstable rock in which anchorage is in most commonly used. Loads on unstable rock mass usually include weight，fissure water pressure，and earthquake force，of which fissure water pressure exists in natural condition and rainstorm condition respectively，and three load combinations are made. Taking stability safety factor that greater than 1.5 to fall unstable and topple unstable rock and 1.3 to slide unstable rock as control object，the authors establish anchorage calculation method for every type of unstable rock reinforced with anchorage and pre-stressed anchorage based on equilibrium theory and failure mechanism of every type of unstable rock.，and the minimum anchors needed can be obtained. The proposed methods have been successfully applied in control of hundreds of unstable rocks in the Three Gorges reservoir region，which will be valuable in revision of the local standard of Chongqing city.

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MECHANICAL STATE OF JOINTED ROCK MASS AND SUPPORT STRUCTURE OF LARGE TUNNEL DURING CONSTRUCTION PROCESS

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2005, 24 (08): -1328 doi:
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Numerical research on the interaction between the jointed rock mass and the support structure of a tunnel of large section and the mechanical state of the whole tunnel system in the sequential process of the excavation and construction is carried out by adopting the discrete element method(DEM). By using the universal distinct element code(UDEC) built-in structure model and a new developed method—de- and reactivating method，simply D-R method，the support structure which is sequentially constructed in steps and sections is simulated. The interaction and mechanical state of the surrounding rock and the support structure in a sequential construction process for a tunnel of large section are systematically studied，and the numerical results conform very well to the reality.

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CONSTRUCTION MONITOR AND DYNAMIC DESIGN OF HIGHWAY DEEP ROAD CUT SLOPE

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2005, 24 (08): -1335 doi:
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In the construction process of a highway deep road cut slope(81 m high)，combined with survey the stability of the slope is studied and the excavation and reinforcement design is conducted before construction，the construction monitor and dynamic design is carried out in the construction process，and systematic summing-up is made after construction. A dynamic design method of high way deep road cut slope including the procedures is proposed.

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IMPROVED CONVERTING PERMEABILITY COEFFICIENT METHOD AND VARIABLE PERMEABILITY COFFICIENT METHOD FOR SEEPAGE CALCULATION IN KARST REGION

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2005, 24 (08): -1341 doi:
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Based on summarizing all kinds of methods used to calculate karst groundwater seepage，aiming at the seepage characteristics in karst region，two methods considering Darcy and non-Darcy fluid simultaneously are put forward：(1) improved converting permeability coefficient method. In this method，a formula suitable for solving the stream wise head loss coefficient l of three turbulence zones is deduced from Colebrook C. F. formula，which can integrate flows in karst conduits with voids as well as cracks；and (2) variable permeability coefficient method. It expresses the permeability coefficient of karst conduits as the function of water head to be solved and the exponent of flow regime，which can integrate the non-Darcy flow in karst conduits with the Darcy flow in other media. To overcome the disadvantage of converting permeability coefficients method，the formulas to calculate tensor of karst conduit in global coordinate system are deduced. According to the basic differential equation for karst seepage，the finite element method(FEM) equations applied for calculating karst seepage are developed on the basis of Galerkin FEM. Verified by examples，the two methods are reasonable and feasible.

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FORMATION OF ARCH AND ROCKBOLTING OF UNDERGROUND POWERHOUSE ROOFS

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2005, 24 (08): -1348 doi:
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For supporting roof of underground powerhouse，a proper design of rock bolts should be based on a clear understanding of both formation and characteristics of the rock roof arch structure and the effect of rock bolt reinforcement. For this purpose，the mechanism of a rock cavern roof arch is studied and effects of different types of rock bolts are evaluated. Numerical modelling of rock bolt support of the Xiaolangdi powerhouse cavern is carried out and applications of arching theory are studied with the purpose to look into the effects of fully grouted rock bolts and tensioned cable anchors in reinforcing the cavern roof. It is concluded that a stable roof arch may be formed after excavation，systematic fully-grouted rock bolting is necessary in reinforcing the roof arch. However，the systematic tensioned cables should be used with caution since they may not be efficient after bolting，and further，they may create upward force to the arch，which counteracts the arch forming and possibly causes instability problems.

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FRACTAL STUDY ON THE REPRESENTATIVE ELEMENTARY VOLUME OF JOINTED ROCK MASSES

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2005, 24 (08): -1355 doi:
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The scale effects of the jointed rock masses are the external behaviors of the inherent complexity of the structure，and could be attributed to the fracture network inside. The paper determines representative elementary volume on the basis of the evaluation of statistical homogeneity of rock mass structure. The study shows that the rock masses structure has statistical self-similarity，and the fractal dimension of the rock structure decreases with the size of the specimen increasing; but when the specimen dimension increases to a certain value，the fractal dimension varies no more. This certain value is named the structural representative elementary volume (SREV). That’s to say，once the size of the specimen reaches SREV，then it is representative of the structure of the homogeneity. According to the definition of REV，only when the size of the specimen reaches REV，is the mechanical behavior of the rock mass representative. Because the similarity of structure is the prerequisite of the similarity of mechanical behavior，this means the SREV must be the lower bound of REV.

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THEORY OF PILE VIBRATION CONSIDERING TRUE THREE-DIMENSIONAL WAVE EFFECT OF SOIL AND ITS CHECK ON THE APPROXIMATE THEORIES

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2005, 24 (08): -1362 doi:
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By modeling soil as a three-dimensional axisymmetric continuum and taking its radial and vertical displacement into account，the interaction between a soil layer and an integral end bearing pile undergoing vertical harmonic load is theoretically investigated. The pile is assumed to be vertical，elastic and of uniform cross-section，and the soil is considered as a linear visco-elastic layer with hysteretic type damping. With the aid of two potentials，the displacement of soil layer is decomposed and then its dynamic equilibrium equation is uncoupled and solved first. Thus the resistance factor and vibration modes of the soil layer are obtained and used to analyze the pile response. By considering the interaction between the soil layer and the pile with boundary condition of displacement continuity and force equilibrium at the interface of them，the dynamic equilibrium equation of pile is solved and an analytical solution for the pile response in frequency domain is yielded，which is used to define complex stiffness of the pile head and the soil local complex stiffness. When governing parameters are varying，a comparison is made with simplified solutions obtained at the condition of plane strain hypothesis or neglecting radial displacement. The comparison involves the soil resistance factor，the soil local complex stiffness and the complex stiffness of the pile head. It proves that in the case of low frequency，stiff soil and slender pile，there can be significant discrepancies between them，but with frequency increasing，the simplified solutions converge to the same.

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STUDY ON THE STABILITY OF PEBBLY CLAY SLOPES WITH PIPE DRAINAGE SYSTEM

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2005, 24 (08): -1371 doi:
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Landslides often develop in pebbly clay slopes as toe cutting or surface loading. The mechanism of this kind of landslide is concerned with the change of mechanical condition and with the change of hydro-geological condition. Groundwater pipe drainage system usually develops in pebbly clay slopes. It is important to restrict groundwater level from rising in a slope. Therefore，the pipe drainage system is an important factor to keep a pebbly clay slope from failure. When local failure of a slope takes place by cutting at slope toe or loading on slope surface，the pipe drainage system may be destroyed. As a result，the ground water level will rise obviously and a landslide may take place. The effect of pipe drainage system on slope stability is studied by investigation and calculation of a landslide，and a physical model is used to uncover the development of groundwater pipe drainage system.

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FUZZY METHOD FOR THE STABILITY ANALYSIS OF CAVE ROOF UNDER PILE TIP IN KARST REGION

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2005, 24 (08): -1376 doi:
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Based on the fuzzy sets theory，combined with the exploration data of karst of a canal-spanning bridge in Hunan province，the model of two-stage fuzzy synthetic judgment and the fuzzy limit-equilibrium-analysis model for the cave roof stability under pile tip are set up. The corresponding fuzzy sets of analysis parameters are constructed and evaluation methods are developed as well. Finally，these two methods are applied to an engineering example showing that these methods are effective for stability evaluation of cave roof under pile tip in karst region.

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STUDY ON THE STABILITY OF SHUIWENZHAN SLOPE IN A LARGE HYDROSTATION AFTER IMPOUNDMENT BY USING 3D NUMERICAL MODELING

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2005, 24 (08): -1384 doi:
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The stability of Shuiwenzhan slope after impoundment is very important to each correlative department because it affects the dam safety and its usage. The results by 3D numerical modeling indicate that there are three failure planes in the slope，a major failure plane and two secondary ones. The connectivity of the major one is low and the others are high. The results also indicate that its deformation is little and it is stable in general in the primary stage；With the impounded water level rising，its deformation increases. There is a large local deformation or damage while the impounded water level reaches 1 850 m. The deformation and damage become bigger and wider leading to partial failure while the impounded water level is up to 1 880 m，but in a whole，it is still stable，and it could only slide in middle-superficial layer.

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TRIAXIAL REAL-TIME OBSERVATIONS OF SANDSTONE UNDER SEEPAGE BY X-RAY CT SCAN

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2005, 24 (08): -1390 doi:
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By using the mid-low-pressure multi-function CT special seepage experiment equipment，the experimental study on real-time CT observation of sandstone under seepage and 3D stress is carried out. Considering the comparability of test results，the normal triaxial tests on dry specimens and triaxial tests on seepage specimens are observed by X-ray CT scan in real-time，respectively，and the initial results that the seepage affects the sandstone damage evolution are obtained. In accordance with the stress and strain curves，the strength calculation formulas of test specimens and deformation discount rate are introduced，and the relative relations of CT value of dry test specimens and seepage test specimens with stress are analyzed. At the same time，the image measuring method to determine the width of cracks is proposed. The paper also introduces the numerical calculation method with which the width of cracks is determined according to the relative relations between the average CT data and measuring areas

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EFFECT OF GEOENVIRONMENTAL CHARACTERISTICS OF CLAY ON STANDARD OF LANDFILL LINER

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2005, 24 (08): -1396 doi:
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Using 1D flow and transport model，the effect of geoenvironmental characteristics of clay soil on landfill liner is evaluated. And the results are used to analyze the effectiveness of the standard of landfill liner. Two types of liner，i. e.，clay liner and single-layer composite liner，are studied. And three index，breakthrough time，leaching rate and leaching contaminant quantity are calculated，respectively. The results show that the type of liner must meet the special needs of field condition in droughty or rainy area. And the composite liner can limit the spread of pollutants more effectively than clay liner in rain-belt of South China. Among all the parameters，the effect of ks on landfill liner is the highest. Thus，it is reasonable to use ks as the design parameter of liner. But the effect of diffusion and adsorption of ion in clay cannot be ignored. And the leaching contaminant quantity adopted as control index is more suitable than breakthrough time.

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SEISMIC RESISTANCE OF PILE FOUNDATION IN LIQUEFACTION LAYER

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2005, 24 (08): -1402 doi:
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The behavior of the model pile in the liquefying saturated sand layer during shake is studied through the shake table test，and some results about the soil-pile dynamic interaction are obtained. According to the test results，the dynamic and static behavior of reaction force and displacement of the saturated sand in different depth is analyzed and compared. The lateral resistance of the soil decreases after the sand has liquefied，but it does not lose completely. So it is conservative that the lateral resistance of the liquefied soil is not considered when the pile in the liquefied soil is designed.

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PARAMETER STUDY ON SLOPE VEGETATION PROTECTION IN RED BED OF SOFT ROCK

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2005, 24 (08): -1407 doi:
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Aiming at the fact that many slope vegetation protections in red bed isn′t ideal，combined with the construction of express highway from Chongqing Liangping to Changshou，parameters correlated to slope vegetation protections for red bed area are studied. Some conclusions are put forward，which provide a basis for slope vegetation protection design in red bed. Also，they have significant values to improve reliability of slope vegetation protections in red bed.

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INVERSING SOIL MECHANICAL PARAMETERS OF EMBANKMENT DAM USING ANT COLONY ALGORITHM

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2005, 24 (08): -1411 doi:
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The principle and the main characteristics of ant colony algorithm(ACA)，a new simulating evolutionary algorithm proposed recently for solving hard combinatorial optimization problems，are introduced. For the purpose of applying ACA to the soil mechanical parameters inversion of embankment dam，the search space of parameters to be inversed is discretized and the inversion problem is transformed into a combinatorial optimization problem. And then ACA is modified by replacing tour length and visibility in ACA with objective function value and standard deviation of objective function value，respectively. At last，the modified ACA is implemented to inverse the soil mechanical parameters of an embankment dam. The results of a simple example show that modified ACA can solve the inversion problem efficiently.

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LOAD STRESS ANALYSIS OF PRESTRESSED CONCRETE PAVEMENT

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2005, 24 (08): -1417 doi:
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The method of the finite-infinite element is suggested to calculate the stress and deformation of prestressed concrete pavement according to its structural characteristics. The iteration model of friction force at slab bottom is adopted，which is coincident much more with the working condition of PCP than the others before. Multi-direction mapped infinite element is adopted to reflect that zero displacement in infinite. The calculating results show that the analytical model is correct. The investigation is valuable for the design and construction of prestressed concrete pavement.

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DISCUSS ON SOFT SOIL STRENGTH FOR SLOPE STABILITY ANALYSIS BASED ON VANE SHEAR STRENGTH

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2005, 24 (08): -1422 doi:
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Tianjin New Harbor is covered with a soft clay layer of about 20 m thick. The vane shear testing is frequently performed to determine shear strength for slope stability analysis. However，even with the use of in-situ vane shear strength，the safety factors of stable slopes are often under estimated，suggesting that the in-situ vane shear strength may not represent the shear strength mobilized along the analyzed sliding surfaces. This study presented a method of converting in-situ vane shear strength into undrained shear strength parameters. The shear strength parameters determined for in-situ vane shear strengths were subjected to statistical regression analysis to take into consideration of the possible effect of non-homogeneity in the soft clay deposit. Using the regressed shear strength parameters，slope stability analyses were performed for five existing soil slopes. Based on the results of the study，it can be concluded that the presented method is effective to convert in-situ vane shear strength into undrained shear strength parameters for slope stability analysis.

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ANALYSIS OF STABILITY FAILURE FOR PIPELINE DURING LONG DISTANCE PIPE JACKING

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2005, 24 (08): -1427 doi:
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When the resistive moment of surrounding soil is less than the torsional moment of eccentric jacking force，stability failure of pipeline occurs and pipes deviates from the designed axes. The reciprocal action between pipes and soil during long-distance linear pipe jacking is analyzed. It is considered that rotational moment arises when pipeline is diagonally loaded. When the maximal soil counterforce of tail pipeline exceeds its bearing capacity，soil fails and pipeline loses stability. The macroscopic model of pipe-soil interaction at failure of pipeline is put forward by assuming that the joints act as hinges. The pipe-soil interaction in the traditional curved pipe jacking is analyzed. The soil counterforce distribution model and load bearing model for the heading and the latter pipelines are set up. By considering displacement for calculating circular earth pressure，the maximal earth counterforce formulas for the heading and the latter pipelines are deduced. The calculation of an example shows that the heading pipeline is apt to lose stability. Finally，several control measures are proposed to avoid failure for long-distance linear and curvilinear pipe jacking construction.

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DYNAMIC RESPONSE OF PILE GROUP IN SATURATED SOIL SUBJECTED TO HORIZONTAL LOADS

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2005, 24 (08): -1433 doi:
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The dynamic responses of pile groups in saturated soil subjected to horizontal harmonic load are researched. By adopting Biot′s three-dimensional wave theory for the half space saturated soil and the pile being simplified as one-dimensional elastic bar，the fundamental solutions are obtained by Hankel integral transform and numerical inverse transform. The second kind of Fredholm′s integral equation of pile groups in saturated soil can be obtained by using compatibility condition between piles and soil and the superposition method. The dynamic impedances of pile groups in saturated soil subjected to horizontal loads are determined by using dynamic interaction factors，and the horizontal impedances，moments and pore pressures are presented. The method can be used to calculate horizontal dynamic response of pile groups in multilayered saturated soil.

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EFFECTS OF DRAWDOWN OF RESERVOIR WATER LEVEL ON LANDSLIDE STABILITY

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2005, 24 (08): -1439 doi:
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Landslide is one of the most serious geological hazards in the Three Gorges reservoir regions. Since the reservoir was in operation in 2003，both reservoir water level descending and rainstorm infiltration have become major factors that affect the stability of landslide. According to the water level operation options considering the case of extreme rainfall in the Three Gorges reservoir region，transient seepage due to the descending of reservoir water level from 175 to 145 m and rainstorm infiltration is calculated using the finite element method. The transient pore water pressures are then used for limit equilibrium analyses of landslides considering the effects of suction on shear strength of unsaturated soils. The effects of different rainfall speed，various rainfall events on landslide stability are discussed. The results of stability analysis show that the stability of landslides by the drawdown of reservoir water level depends on permeability coefficient of landslides and the structure of landslide. The critical declining velocity of Hongshibao Landslide III is 1 m/d when the rainstorm intensity is 100 mm/d，which will provide scientific basis for the treatment of landslide in Three Gorges reservoir.

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ANALYSIS ON DEFORMATION MONITORING AND TENDENCY OF XUJIADONG LANDSLIDE

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2005, 24 (08): -1445 doi:
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In October 2000，the Xujiadong landslide was activated by cutting slope. The landslide was reinforced by means of antisliding piles and prestressed anchorages. In the course of construction and operation，long term monitoring of deformation in depths was carried out. The displacement information was analyzed and fed back in time. The influence factors of landslide deformation were researched and the deformation trend was predicted. It has been proved that the observed data can correctly reflect the deformation of the landslide and meet the requirement for the timely treatment.

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康健博士论文摘要

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2005, 24 (08): -1449 doi:
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康健博士论文摘要

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STUDY ON MECHANISM AND CONTROL OF SOFT ROCK ROADWAY FLOOR HEAVE IN GEQUAN COAL MINE

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2005, 24 (08): -1450 doi:
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Serious floor heave of the haulage tunnel at the southern –190 m level was a great problem in Gequan coal mine in China. The main physical and mechanical properties of surrounding rocks around the roadway are tested. On the basis of the study of large range of rock mass around the roadway，the factors resulting in the floor heave are analyzed. Through numerical modeling with UDEC3.1，the plastic region and stresses distribution around the roadway are understood under the original support. Thus，the principal factors resulting in floor heave i.e.，the properties of surrounding rock，water，and support form，are released. With the recognition of the mechanism of the floor heave，the control scheme that whole section grouting is combined with side and corner bolt reinforcement is put forward. Through numerical modeling，the support parameters of the new scheme are optimized. In-situ measurement shows that good result of controlling the floor heave is obtained with the scheme.