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  --2002, 21 (02)   Published: 15 February 2002
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Artiles

EXPECTED SLIDE PATH METHOD FOR STABILITY
ANALYSIS OF ROCK MASS BASED ON STATISTICS MODEL
OF JOINTS AND STRESS FIELD

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 2002, 21 (02): 151-157 doi:
Full Text: [PDF 360 KB] (896)
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A searching method of expected slide path in rock mass based on domain-divided statistics model of joints and the rock mass stress field is presented. Firstly the treating techniques to produce domain-divided statistics model of joints on interfaces between sub-domains are described. Then the formulas of slide resistance reserve in specified orientation and local location in rock mass based on Einstein’s theory and rock mass stress field are developed. Finally,the expected slide path based on searched slide paths,the deviation estimation in the sense of probability,and some numerical results are shown.

DEM ANALYSIS ON THE THIRD PERIOD LONGITUDINAL COFFERDAM OF THE THREE GORGES UNDER BLAST LOADING

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 2002, 21 (02): 158-162 doi:
Full Text: [PDF 204 KB] (1023)
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The responses of the second period RCC of Qingjiang under blasting loading are analyzed by DEM first. The material parameters are obtained by comparing the numerical results and those of the experiments. And then,with these material parameters and some data obtained from experiments,the decaying rules of the vibration velocities with distance and time of the three period longitudinal cofferdam of the Three Gorges under blasting loading are analyzed. It is shown that the vibration safety of blast dismantlement for the third period longitudinal cofferdam of the Three Gorges is the most important problem. Therefore,it is practical and important to study the responses of vibration of the third period longitudinal cofferdam under blast loading.

CREEP CHARACTERISTIC AND LONG-TERM STABILITY OF ROCK MASS IN SHIP LOCK HIGH SLOPE OF THE THREE GORGES PROJECT

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 2002, 21 (02): 163-168 doi:
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The results of creep test in site for rock mass and discontinuity in shiplock area of the Three Gorges Project are introduced. Considering the effects of construction excavation and seepage pressure,the rheological analysis on the stability of shiplock slope is made during construction and running. The analysis results are validated by measured data in site.

ADAPTIVE ELASTO-VISCO-PLASTIC FINITE ELEMENT ANALYSIS OF THE STABILITY OF DAYANTANG SLOPE

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 2002, 21 (02): 169-175 doi:
Full Text: [PDF 420 KB] (995)
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The deformation and stability of Dayantang slope are studied with adaptive elasto-viscoplastic finite element method. In the calculation,if local unstability happens,the edges of tension yield areas will be simulated with Goodman joint elements,meanwhile the mesh will be adjusted and refined. The results show that the local unstability of Dayantang slope will not occur,and the minimum safety factor of the entire slope is about 1.143.

FRACTURE-DAMAGE MODEL OF JOINTED ROCKMASS AND ITS APPLICATION TO THE NUMERICAL PARAMETES PREDICTING OF THE DAM-BED-ROCK OF THE THREE GORGES PROJECT

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 2002, 21 (02): 176-179 doi:
Full Text: [PDF 282 KB] (1086)
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Based on a fracture-damage model,the equivalent compliance tensor and mechanics parameters for jointed rock mass are numerically predicted,and the dam-bed-rock masses of the Three Gorges Project are analyzed by this model. The comparison of this model with the other two models,joint stiffness model and inclusion model for jointed rock mass,show a good coincidence. The results are also verified by the displacement-back-analysis in the field. The simulated parameters provide a reference for the stability analysis of the Three Gorges Project.

MONITOR OF DISTURBED ZONE FOR ROCK SLOPE BY SLIDING DEFORMETER

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 2002, 21 (02): 180-184 doi:
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The monitoring work and related observations were conducted in the north slope of the permanent shiplock of the Three Gorges Project by sliding deformeter. The interpretation of the observed data indicates that:(1) the rock mass in the slope deformed mainly in a shallow belt underneath the excavation surface,termed as disturbed zone,(2) the deformation of the rock mass in disturbed zones was mainly composed of “opening displacement” of primary structure planes,constituting 66.7% of the total accumulative deformation on average,(3) the magnitude of deformation is closely related to the excavation intensity,(4) the slope is stable in the monitoring region based on the analysis of deformation trend.

STUDY ON THE FORMING MECHANISM OF DISPLACEMENT VECTOR ANGLE AND STABILITY EVOLUTION RELATION OF ACCUMULATIVE-FORMATION SLOPES

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 2002, 21 (02): 185-192 doi:
Full Text: [PDF 275 KB] (898)
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Through the analysis on deformation property and the basic constitution of different stability evolution stages of the accumulative-formation slope,it is found that the surface displacement vector angles of slope are constituted of whole sliding vector angle,compressive displacement vector angle,plastic deformation vector angle and creeping deformation vector angle. And the ratio of its constitution is varied with different position and the different stability evolution stage. The formation mechanism of displacement vector angles in different stability evolution stages of the accumulative-formation slope is deeply analyzed and explored. The quantitative relationships among surface displacement vector angles,displacement velocity,the other parameters in the stages of the compressive deformation and the plastic deformation are established,respectively. The variation laws of displacement vector angles in the different evolution stages and different positions are also summarized. Finally,based on the analysis on the actual displacement monitoring data of the different evolution stages of Xitan landslides,it is found that the displacement vector angles of the slope are of different variation laws in different stability evolution stages,and these dynamic variation laws are coincided well with the actual landslides stage.

THEORETICAL AND EXPERIMENTAL STUDY ON TIME-TEMPERATURE EQUIVALENT PRINCIPLE FOR ROCK

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 2002, 21 (02): 193-198 doi:
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Based on the theory of irreversible process thermodynamics,non-linear thermodynamic analysis is engaged in,and non-linear stress-strain-temperature equations are established. Thus,general expression for time-temperature equivalent principle is theoretically obtained.

STUDY ON DETERMINATION OF SHEAR FRACTURE TOUGHNESS(KIIc)

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 2002, 21 (02): 199-203 doi:
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As shear force is applied to the specimen with a crack,the crack extends and deviates from original crack plane. Measured and calculated shear fracture toughness,KIIc is less than KIc. Theoretical study shows that the crack extension under shear loading is caused by tensile stress,and it does not belong to shear fracture. To restrain or eliminate tensile stress,compressive stress should be applied to the specimen. Thus pure shear fracture caused by shear stress is obtained. Calculated shear fracture toughness KIIc is larger than KIc. The study shows that the occurrence of mode II fracture requires its prerequisite. A prerequisite for mode II fracture is frθmax / fθmax>1 and frθmax / fθmax>KIIc / KIc,where frθmax is the maximum dimensionless shear stress intensity factor,fθmax is the maximum dimensionless circumferential tensile stress intensity factor.

STUDY ON FRACTAL INTERFACE EFFECT AND DYNAMIC PROBLEM OF GRAVITY-TYPE FRACTURE SURFACE SLIDING

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 2002, 21 (02): 204-209 doi:
Full Text: [PDF 472 KB] (869)
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Fractal interface effect and dynamic character of gravity-type fracture surface sliding befween upper and lower pan of the fracture surface slip under the gravity are studied. The fractal character of the geologic fracture surface is studied. The gravity fracture surface sliding model with self-affine fractal character is established. The fractal interface effect of fracture plane sliding is analyzed by physical and numerical stimulations. The empirical quantitative relationship between the distance of fracture surface sliding and fractal dimension of fracture surface is obtained. The dynamic character of gravity fracture surface sliding is considered and the stiffness criterion of fracture surface sliding is proposed. In the end,the research direction of this special subject is given.

ELASTO-PLASTIC MODEL OF SOFT CLAY UNDER REVERSAL LOAD

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 2002, 21 (02): 210-214 doi:
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A generalized constitutive theory of the boundary surface of soft clay with plastic deformation is established,based on the characteristics of soft soil deformation and variation of pore pressure under reversal loading. The boundary surface model is capable of simulating plastic deformation under low stress level. The linear elastic unloading process is improved and becomes an elasto-plastic one. Through comparison of numerical simulation results with tri-axial test data,its reliability is verified.

EXPERIMENTAL AND THEORETICAL STUDY ON SIZE EFFECT ON STRAIN SOFTENING OF ROCK MATERIALS

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 2002, 21 (02): 215-218 doi:
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The sandrock specimens of different diameters and heights in stress-strain test are adopted. The size effect on rock strain softening is found. The rock brittleness increases after postpeak with the height of the specimen. To this result,the theoretical analysis and experimental result reach a good agreement by using the gradient plastic theory.

STUDY ON THE CO-RELATION LAW OF FRACTAL DISTRIBUTION OF CRACK IN ROCK STRATUM

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 2002, 21 (02): 219-222 doi:
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The statistical research results of fractal distribution of crack in rock stratum is introduced. The rock samples are taken from the rock cores of length about 1000 m of three geological drilling holes. Under the condition of identical geological mass,a co-relation law is found between fractal dimension of fissure and production of strength and elastic modulus in different rock strata. The physical mechanism of rock deformation and split affected by ground stress is discussed.

CALCULATION ON ENERGY RELIEF AND LOAD EFFECT CAUSED BY BRITTLE FAILURE OF PRESSED POST

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 2002, 21 (02): 223-227 doi:
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During the weakened deformation stage of pressed opst,the energy variation relationship of press-
pressed post system is analyzed. The expressions are obtained for the displacement of stopping point of pressed post with unstable failure,the elastic energy relief amount of press and the inertial force imposed on press with brittle failure of pressed post and the largest displacement of press. These mechanic parameters are calculated and analyzed by quoting the load-displacement expression of pressed concrete post with high strength. The deeper knowledge is obtained for rockburst and rockburst strength of pillar,alley wall of mining and coal wall of stope.

3-DIMENSIONAL NON-LINEAR FINITE ELEMENT SIMULATION OF TUNNEL STRUCTURE FOR MOVING-FORWARD SHIELD

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 2002, 21 (02): 228-232 doi:
Full Text: [PDF 348 KB] (1669)
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The simulation methodology of tunnel construction with shield moving forward by 3-D non-linear finite element method is proposed. A transferring stiffness method is put forward to imitate moving-forward shield process and the weighted stiffness is used to modify Goodman element for the case of two types of materials. An example of underground project is studied and the laws of displacements of ground surface and disturbance to the soil are analyzed. It is proved that the shield going-forward will heavily disturb the soil and induce upheaval and settlement of ground.

STUDY ON MECHANICAL BEHAVIOR OF JOINTED ROCK MASS AFFECTED BY TEMPERATURE AND SATURATED WATER

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 2002, 21 (02): 233-237 doi:
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The mechanic function is theoretically described with the relationship between effective elastic moduli of saturated cracks of jointed rock mass and elastic moduli of rock,derived by O′Connell.According to the implication of the crack-density parameter in the relationship,the mathematical relationship is derived between the crack-density and the fracture tensor introduced by Oda under temperature effect.On the basis of the experiment results,under the effects of temperature and saturated water the regression expression of stress-strain and the compressive strength are obtained for the rock mass with single joint.The model is demonstrated by the results of test. The mechanical model can be used for THM coupling analysis on jointed rock mass.

SEEPAGE FIELD CHANGES OF SHIPLOCK SLOPE OF TGP UNDER RAINING AND PERCOLATION

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 2002, 21 (02): 238-241 doi:
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The unsteady changes of seepage field of slope of TGP shiplock under raining and percolation are anlyzed by saturated seepage model. The computation suggests that raining and percolation do have some effect on the seepage field of high slope,but they don’t lead to high pressure water head in the shallow slope and vicinity of vertical wall of shiplock for the existence of drainage holes. Therefore, raining and percolation have slight influence on the stability of high slope.

NUMERICAL ANALYSIS ON REINFORCED CONCRETE LINING FOR OUTLET MANIFOLD OF YELLOW RIVER DIVERSION PROJECT

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 2002, 21 (02): 242-246 doi:
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In order to verify the feasibility and reasonableness of design for the reinforced concrete lining of outlet manifold of general pump stations of Shanxi Yellow River Diversion Project,3-D numerical analysis is made based on field investigations. The stress distribution and width of cracks of reinforced concrete lining are obtained. Furthermore,the shape of reinforced concrete and reinforcement ratio of the manifold are suggested to control the width of cracks in concrete and keep stability of the engineering.

DESIGN METHOD OF RETAINING PILE WITH PRESTRESSED CABLE

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 2002, 21 (02): 247-250 doi:
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The method of elastic foundation beam with restriction of transverse deformation is recommended to design of retaining pile with prestressed cable. According to deformation consistence principle,the tensive force of prestressed cable,displacement and internal force of the pile are calculated. Also,with the method,the retai-
ning pile with prestressed cable is first designed for a high slope in weak rockmasses in Nankun Railway. Field testing results show that this calculation method is reasonable and easy to use.

MODEL TESTING RESEARCH ON THE VARIATION OF TENSION FORCE OF ANCHOR CABLE WITH TIME IN REINFORCEMENT OF SOFT ROCKS

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 2002, 21 (02): 251-256 doi:
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The creep equation of simulated material of soft rocks is given through model testing research on soft rocks reinforced by prestressed anchor cable. The characteristics of prestress of anchor cable varied with time are discussed in particular. Then the relationship between the initial prestress and the stable prestress in anchor cable is analyzed. Based on above results,an estimating method of pulling force of anchor cable decreased with time is finally proposed.

STRESS ANALYSIS AND INSTALLATION PROCEDURES OF ROCK
BOLT FOR PERMANENT SHIPLOCK OF TGP

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 2002, 21 (02): 257-260 doi:
Full Text: [PDF 179 KB] (1153)
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The construction inquirements and structural arrangement of the high strength rock bolts on vertical wall are introduced during the second-stage construction of permanent shiplock of TGP. The installation procedures and technology of rock bolts under field conditions are described. The observation results from testing and monitoring show that the constructive quality of the rock bolts with high strength is good enough to effectively strengthen the rock slope along both sides of the shiplock.

STABILIZATION TECHNOLOGY ON THE HIGH-STEEP ROCK SLOPE
IN THE THREE GORGES PROJECT SHIPLOCK

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 2002, 21 (02): 261-267 doi:
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The permanent shiplock is one of the main structures of TGP. The stability and deformation control of the shiplock slope are the key technical problems of the TGP. According to the characteristics of the slope,the technical path is discussed for the research,design and construction,and then the slope scale,rock support,drainage and seepage-prevention,construction procedures,blast control and monitoring measures during construction are presented. The conclusion is that the stability and deformation up to now have been controlled in the range of design.

UTILIZATION AND STRENGTHENING OF ROCK MASS
OF DIVISION PIER AT TGP PERMANENT SHIPLOCK

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 2002, 21 (02): 268-272 doi:
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The reserved rock mass between two lines of TGP permanent ship lock is used as their division pier,which is obviously superior in economy to the scheme of removing the rock mass and constructing a concrete division pier at its location. The rock mechanics problems encountered in the course of excavating the lock chambers,such as cracking on the surface of reserved rock mass,the potential movable rock blocks on the top of vertical excavated wall,and the large faults,were all solved through engineering treatment measures developed by field dynamic design,and the reserved rock mass is strengthened.

STUDY ON KEY TECHNOLOGY OF FULLY-MECHANIZED SUB-LEVEL CAVING MINING FOR SPECIAL THICK
AND HARD COAL SEAM

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 2002, 21 (02): 273-279 doi:
Full Text: [PDF 429 KB] (1040)
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After analyzing fully-mechanized sub-level caving technology in the case of special thick and hard coal seam,it is presented that the increment of cavability of hard roof coal and available control of gas are the main difficult technology problem to be faced. The structure and breaking characteristic of hard roof coal are analysed,and the main technology approach and measurements to increase cavability of hard roof coal are proposed. The technology has been successfully applied in Baijigou colliery,Ningxia,where the coal seam is thicker than 20 m,with hard coal,hard roof,intensive gas and shallow oveburden. The annual output of coal there is 1.5 million tons. The proposed technigue is a breakthrough to sub-level caving mining technique,and anticipative effect has been obtained.

MECHANISM ANALYSIS ON GEOLOGICAL HAZARDS TRIGGERED BY EXTERNAL DISTURBANCE

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 2002, 21 (02): 280-284 doi:
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The forming mechanism of geological hazards triggered by external disturbance such as earthquakes,rainstorms and engineering activities,etc.,is analyzed deeply by means of nonlinear science. And the forming mechanism is summarized to two effects:effect of micro-disturbance under critical condition and effect of macro-disturbance under near critical condition. A lot of phenomena about geological hazards can be explained perfectly using the two effects. The results of studies show that when the evolution of geological bodies is to the critical state,the micro-disturbance can trigger geological hazards,while if the evolution of geological bodies is near the critical state,the macro-disturbance can trigger geological hazards in advance.

CAUSE ANALYSIS AND QUASI-QUANTITATIVE PREDICTION ON THE COLLAPSE OF KARST OVERBURDEN

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 2002, 21 (02): 285-289 doi:
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In the karst district,the collapse of overburden has been become one of major geological hazards met in engineering construction. In the light of overburden collapses occured in the three large-scale highway construction projects in Guangdong Province,the general topography configuration,engineering geology and hydrologic geology condition,and collapse circumstance of the three projects are summarized. The mechanism and cause of collapse are analyzed in detail. On this foundation,the basic condition and geology function to affact collapse are summed up. The corresponding power weight is assigned according to different factor levels. Finally,on the basis of collapse mechanism of karst overburden,the treatment measure in the practice is briefly put forward to guide practice.

RESEARCH ON RELATIONSHIP AMONG LONGITUDINAL AND TRANSVERSE WAVE VELOCITIES AND TEMPERATURE OF ARTIFICIALLY FROZEN CLAY

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 2002, 21 (02): 290-293 doi:
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The longitudinal and transverse wave velocities of frozen clays are measured by UVM-2 ultrasonic instrument and 500 kHz broadband ultrasonic transducer at the temperature of -1°C,-3°C,-5°C,-7°C,-10°C,-12°C,-15°C,-17°C and-18°C. As indicated by the results,the lower the temperature is,the greater the wave velocity is. At the temperature higher than -4°C,the relationship between wave velocity and temperature is linear. At the temperature about-17°C,the increment of wave velocity is very small. The relationship between the wave velocity and temperature is analyzed theoretically. By means of elasticity theory,elastic modulus and Poisson′s ratio are calculatied.

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 2002, 21 (02): 295-295 doi:
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 2002, 21 (02): 296-296 doi:
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PURE SHEAR FRACTURE OF BRITTLE ROCK
——A THEORETICAL AND LABORATORY STUDY

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 2002, 21 (02): 297-297 doi:
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The determination of pure shear (Mode Ⅱ) fracture toughness,KIIc,for brittle rock is studied. Three types of specimens,which are anti-symmetric four-point bending specimen,direct shearing specimen and shear-box specimen,are experimentally investigated. A new criterion is established for either Mode I (tensile) or Mode Ⅱ (shear) fracture of brittle rock,which clearly distinguishes the fracture mode from the loading mode.
With guiding-grooves in both the anti-symmetric four-point bending and the direct shearing specimens,Mode Ⅱ fracture can be successfully created. Numerical calculations show that the guiding-grooves in the notch plane can depress the tensile stresses at the notch tips and enable the crack to propagate along the notch plane. The value of KIIc obtained in this case is 2~3 times as high as the magnitude of KIc,which is considered as the true Mode Ⅱ fracture toughness of rock.
Mode Ⅱ fracture can be easily created in a shear-box loaded square specimen.The compressive stress in the two directions can completely depress the tensile stresses around the notch tips and makes it easy for the crack to initiate and propagate along the notch plane,leading to Mode Ⅱ fracture. The shear-box test is suggested as a method for determining the Mode Ⅱ fracture toughness of rock.
Both theoretical and laboratory studies of shear-box test show that the apparent Mode Ⅱ fracture toughness ,i.e. Mode Ⅱ fracture toughness under the compressive stress,linearly increases with the compressive stress on the notch plane. The intercept of straight line of versus (i. e. = 0) is defined as the Mode II fracture toughness KIIc. In some cases,it is not KIIc but that needs to be known. For instance,the pre-existing cracks and discontinuities in rock and rock masses are subjected to compressive loading in most cases. What is useful in this case is the Model II fracture toughness under the in-situ compressive stress, ,instead of KIIc.
The size effect on the determination of KIIc has been experimentally studied. The examined dimensions include the specimen thickness B,the dimensionless notch length a /W,and the notch inclination angle a. Test results show that KIIc decreases with the increment of the specimen thickness B and becomes a constant when B is equal to or larger than the specimen height W for both the single- and double-notched specimens. When the dimensionless notch length a /W increases,KIIc decreases and approaches a limit if a /W is in the interval of 0.5~0.6 for single-notched specimens and 0.3~0.35 for double-notched specimens. The notch inclination angle has a significant effect on the failure pattern of the specimen. Too small or too large a will lead to either local crushing or Model I fracture. The favorable range for a is 60°~75° for Model Ⅱ fracture.
Finally,a new criterion is established based on the examination of the Mode Ⅰ and Model Ⅱ stress intensity factors,KI(q ) and KII(q ). The criterion can predict either Model I or Model Ⅱ fractures,no matter what kind of loading condition is applied. Model Ⅱ fracture occurs when the ratio of KIImax to KImax is larger than that of KIIc to KIc and KIImax reaches its critical value,KIIc.

RESEARCH ON THE LOADING TEST AND STRUCTURAL MODELS OF PREFABRICATED SEGMENT REINFORCED BY SECONDARY LINING

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 2002, 21 (02): 298-298 doi:
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