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2003, 22 (11): -0 doi:
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CONSTITUTIVE MODEL OF POROUS ELASTOVISCOPLASTIC MATERIALS SUBJECTED TO SHOCK
——PART II：DISTORSIONAL BEHAVIOR OF POROUS
ELASTOVISCOPLASTIC MATERIALS

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2003, 22 (11): -1763 doi:
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[PDF 182 KB] (1064)

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Continuing the study performed in the first part put in the issue 2003-9 of this journal，the second part of the paper researches the distorsional behavior of porous elastoviscoplastic materials subjected to shock. The influence of strain rate on material strength is considered，and a unified strain rate dependent strength model of competition between thermal activation mechanism and macro-viscosity mechanism is proposed. The influences of stress state，strain hardening，distorsional deformation damage，and damage related with porosity change are considered. And furthermore，on the basis of thermal activation mechanism，a relaxation type relation between distorsional stress tensor and distorsional strain tensor is given，and the model follows the second thermodynamic law.

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ANALYSIS ON BLASTING EXTRUSION CHARACTERISTIC
OF SOIL AND ROCK

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2003, 22 (11): -1767 doi:
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[PDF 177 KB] (958)

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Based on the mechanism analysis of blasting extrusion with linear charges，elasto-plastic model of soil and rock under blasting is established in this paper. In terms of state equation of blasting and conservation law of mass，the elasto-plastic calculation formula is provided to calculate extrusion coefficient. 3 types of soil and 2 kinds of explosive are taken as examples to analysis. It is illustrated that blasting extrusion coefficient of soil and rock is related to the density and strength of material. The density and detonation speed of explosive are two additional factors affecting blasting extrusion coefficient.

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TIME DEPENDENT DAMAGE MODEL OF ROCK
UNDER DYNAMIC LOADING

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2003, 22 (11): -1771 doi:
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[PDF 270 KB] (1555)

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The current studying status of dynamic constitutive model of rock is reviewed. Based on analysis of measured dynamic constitutive curves，and combining statistic damage model and viscoelastic model，a time dependent damage model of rock under dynamic loading is established. There is a good coherence between stress-strain curves calculated from the proposed model and that from experimental data directly.

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ENERGY DISSIPATION OF ROCK DAMAGE UNDER IMPACT LOADING

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2003, 22 (11): -1777 doi:
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[PDF 207 KB] (1390)

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Dynamic damage of brittle rocks is an evolution process of inconvertible energy dissipation. The damage dissipation energy can be calculated through the area between Rayleigh line and Hugoniot shock adiabatic curve. The shock-induced damage experiments are carried out by means of a gas gun. The stress wave curves are measured using the planar impact techniques. Based on the experiment results and the Rankine-Hugoniot conservation equations，the damage energy dissipation of brittle rock under impact loading is calculated. The rock damage evolution rules are fairly delineated，which contribute to establish the new rock damage model.

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LEAST ENERGY PRICIPLE OF DYNAMICAL FAILURE OF ROCK MASS

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2003, 22 (11): -1781 doi:
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[PDF 196 KB] (1405)

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Based on the fact that the released energy of dynamical failure of rock mass is more than induced energy，the inhomogeneity and anisotropy of rock mass are discussed，and the least energy principle of dynamical failure of rock mass is proposed. Different failure manners correspond to different consuming energy and stress states. The consuming energy of rock mass failure in reality is destroy energy under 1D stress state. Some engineering and laboratory cases are presented，and the study results will be beneficial to defence engineering and underground engineering.

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TIME-STRESS HISTORY ON INTERFACE BETWEEN CRACKED AND UNCRACKED ZONES UNDER ROCK BLASTING

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2003, 22 (11): -1784 doi:
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[PDF 254 KB] (1175)

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Applying the theory of cavity expansion，the characteristics of cracked zones under rock blasting are studied according to the behavior of blasting-induced deformation and damage of rock. The expansion and squeeze course of cavity wall under the explosion gas，the crack limits and the time history of stress on the interface between cracked and the uncracked zones are presented. The radium of blasting cavity，stress peak value and action time of stress waves are validated by the theory of classical explosion mechanics and the way of curve regression. The results of numerical calculation analysis keep good consistence with that given by traditional mechanics.

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DISCUSSION ABOUT MECHANISM OF STRAIN-RATE EFFECT AND ANISOTROPY OF SATURATED ROCKS

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2003, 22 (11): -1789 doi:
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[PDF 189 KB] (1289)

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Uniaxial compressive experiment of Nanjing sandstone and Dali marble is conducted on MTS with strain rate varied from to /s. It can be found that sandstone and marble are of obvious characteristics of anisotropy，but the anisotropy of marble is weaker than that of sandstone. And they are of obvious strain-rate effect，that is，strength increases with strain rate. Saturation liquid can promote the character of anisotropy and strain rate effect，and under the same strain rate，the viscosity of saturation liquid can only affect rock strength. As strain rate rises，the influence of viscosity on rock strength reduces.

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X-RAY CT APPROACH ON ROCK-INTERIOR CRACK EVOLUTION UNDER LOW STRAIN RATE

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2003, 22 (11): -1793 doi:
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[PDF 297 KB] (1078)

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By X-ray CT method，it is found that rock experiences condensation，dilatancy，evolution of CT crack and rapture process in turn under uniaxial compression，which shows the meso-mechanism of rock deformation and rapture. CT image analysis and density damage increment analysis are two approaches based on X-ray CT. Through CT image analysis，the width，length and direction of crack are gained. The values of density damage at any stress state and position are gained by analysis of density damage increment. At the process of CT crack and rapture evolution，the acoustic emission can not precisely reflect the meso-mechanism of rock deformation and rapture because of localization of damage.

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RESEARCH ON SHPB TESTING TECHNIQUE FOR
BRITTLE MATERIAL

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2003, 22 (11): -1798 doi:
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[PDF 217 KB] (1594)

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The dynamic characteristics in higher strain rate of brittle materials，such as hard rock，concrete， mortar and ceramics with high strength，and the non-homogeneous structural materials consisting of brittle material are researched using SHPB device. The progress is brought about in SHPB testing technique. The problems are discussed briefly of gimbals，pulse shaper，non-uniform linear projectile，soft medium on the impacted end of the input bar，artificial joint sample and structural material sample.

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TESTING STUDY ON LONGITUDINAL WAVE CHARACTERISTICS
OF GRANITE AFTER HIGH TEMPERATURE

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2003, 22 (11): -1803 doi:
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[PDF 189 KB] (1319)

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The longitudinal wave velocities are measured for 25 granite samples before and after high temperature. With the ultrasonic and conventional compression methods，the Young¢s moduli of granite after high temperature are determined. The longitudinal wave velocities and Young¢s moduli after high temperature are analyzed. The results show that the velocities of longitudinal wave decrease with temperature. The Young¢s modulus gained by ultrasonic method decreases more than that gained by conventional method. This means that the change of physical characteristics of granite is much severer than that of its mechanical characteristics after high temperature.

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STRAIN RESPONSE OF CYCLIC HARDENING UNDER FATIGUE LOADING ON SATURATED ROCK

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2003, 22 (11): -1807 doi:
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[PDF 259 KB] (1579)

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Through the cyclic loading (0.5～25 Hz) experiment on Nanjing and Hefei sandstone，it is found that the unstable behavior of hysteresis is mainly caused by micro-damages growing in processing-hardening period. It is observed that hysteresis loops become small and stable as frequency or cyclic number increasing. The effects of strain hardening and softening are suggested on the basis of strain-amplitude decreasing under constant stress，strain-amplitude increasing with stress-amplitude increasing，and modulus decreasing with strain-amplitude increasing.

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CALCULATION PRINCIPLE FOR PENETRATION AND
PERFORATION OF PROJECTILES INTO ROCK

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2003, 22 (11): -1811 doi:
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[PDF 298 KB] (1142)

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The deformation and failure models of rock are presented according to the characteristics of local deformation and failure of rock. The formula of stress on the projectile is obtained from relation of momentum conservation on the wavefront and continuum condition of the surface of projectile. The results are different from the existing formulae both in China and abroad. The scale relation of penetration and perforation is clarified by the relation of energy transfer in the process of fragmentation zone to radial crack zone. A generalized formula for the penetration depth and the perforation process on a sound physical background are obtained from the non-deformable projectile with conical nose. By comparison with current empirical equations， the proposed formula is validated.

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ON MECHANISM OF SLENDER PROJECTILE PENETRATING
INTO CONCRETE

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2003, 22 (11): -1817 doi:
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[PDF 517 KB] (976)

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In this paper the mechanism of slender projectile penetrating into concrete is gained by using the scale penetration experiments. The whole penetrating process can be divided into the phase of funnel crater’s formation and the phase of penetration under the crater. The calculation methods for predicting penetration of slender projectile into concrete are suggested and its reliability is verified.

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NUMERICAL SIMULATION ON PENETRATION AND EXPOLOSION EFFECT IN ROCKS

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2003, 22 (11): -1823 doi:
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[PDF 442 KB] (1060)

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Nonliner finite element method and blast wave theory are applied to simulate the destruction effect of blast in rocks，such as propagation of blast wave and crater effect under penetration and explosion. Dynamite elements are used directly in the calculation. Numerical examples show that the proposed method is efficient.

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FREE-FIELD STRESS WAVE PROPAGATION INDUCED BY UNDERGROUND CHEMICAL EXPLOSION IN GRANITE

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2003, 22 (11): -1827 doi:
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[PDF 256 KB] (1061)

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The test data are interpreted of the free-field stress wave of a series of chemical explosion from 1 to 150 kg TNT in granite. The stress wave attenuation law is found for different rock conditions，in which the ground motion parameter is of stronger regularity. Compared with the result of nuclear explosion，the stress wave attenuation of the chemical explosion is faster，because it is more sensitive to the local rock condition in small charge. According to the test result，under given rock condition and engineering construction status，the reason why the measured stress is low and scattered is analyzed. Some problems about in-situ measurement of stress wave are discussed. The conclusion is given out that the peak stress calculated from the particle velocity can reflect the stress field more clearly than the stress measured directly.

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STUDY ON REGULATION OF STRESS WAVE PROPAGATION
IN ROCKMASS WITH COMPOUND STRUCTURES

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2003, 22 (11): -1832 doi:
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[PDF 254 KB] (1332)

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The compound structures are of clear superiority in resisting dynamic loading and can absorb more shock energy than ordinary structure. Based on the test results by blasting simulation equipment with diameter of 2.5m and the calculations by dynamic finite element method，the stress wave propagation in rockmass with underground compound circle structure surrounded by the soft backfill and the interaction between the stress wave and compound structures are studied. The regulations of the stress wave propagation in rockmass with the underground compound structure are obtained.

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TESTING STUDY ON RELATIONSHIP BETWEEN ULTRASONIC
WAVE VELOCITIES AND PHYSICO-MECHANICAL
PROPERTY OF FROZEN SOILS

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2003, 22 (11): -1837 doi:
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[PDF 184 KB] (1328)

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Ultrasonic wave velocity traveling in media reflects the physico-mechanical properties of the media. Velocities of the ultrasonic (dilatational and shear) waves in frozen fine sand，silt (loess) and clay with different densities are measured at different temperatures by UVM-2 ultrasonic measuring system. Then，the variation tendency of ultrasonic wave velocities with densities and temperatures is analyzed. The following results are obtained. (1) The ultrasonic wave velocities are influenced by soil particle size and soil composition which affect the variation of the bound water content and then the variation of unfrozen water content after the soil is frozen. Therefore，in terms of the ultrasonic wave velocities versus temperature and unfrozen water content versus temperature， the relationship can be set up between ultrasonic wave velocities and unfrozen water content. (2) The variation of dilatational and shear wave velocities is related to that of densities of soils，especially of frozen loess. (3) Different type of the frozen soil is of different scope of dilatational and shear velocities. The ratio of dilatational to shear velocities which express the relative range of compression and shear can be used to determine the type of frozen soils. Generally，the ratios are 1.07，2.15 and 0.7 for frozen clay，frozen loess and frozen fine sand，respectively. In terms of elastic theory，the Poisson¢s ratio is related to wave velocity ratio，so that the property of strength and deformation can be determined by measuring the velocity ratio.

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MEASUREMENT OF S-WAVE VELOCITY WITH
PROBES FOR P-WAVE

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2003, 22 (11): -1841 doi:
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[PDF 149 KB] (1532)

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There is P-wave in the rock simultaneously in S-wave measurement. The amplitude of P-wave is lower，but its velocity is higher than that of S-wave，so that it is difficult to decide the initial time of S-wave reaching. However，the velocity of S-wave in a rock block with a large plane can be measured with the probes for P-wave. Two probes for P-wave are parallelly coupled in a distance on the same plane of the rock block with grease. The transmitting probe produces a pulse which causes a P-wave in the normal direction of the plane and a S-wave in its shear direction. The vibration direction resulted from the S-wave is perpendicular to the plane，which is received by the probe for P-wave. For the end of probe is a circle，but not a point，the value is the upper limit of S-wave velocity obtained from the distance between the central points of two probes，and the lower limit can be obtained from the distance between the inner boundary of two probes.

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DISTRIBUTION，TYPE，MECHANISM AND PREVENTION
OF ROCKBRUST IN CHINA

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2003, 22 (11): -1844 doi:
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[PDF 591 KB] (1938)

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Based on the study of rockburst distribution in China，the rockbursts are classified to the coalmass compressible type，roof crack type and fault dislocation type. The mechanism of every rockburst type is studied respectively. Based on these study，the effective measures preventing rockbursts are put forward. The measures preventing rockburst of coalmass compressible type are to change properties of coalmass by coal seam effusion，unloading by exploding，mechanical vibration for rockmass crack and so on. The measures preventing rockburst of roof crack type are to change roof movement rules by mining liberation layer，high-pressured water-jet cutting for liberating coal seam itself，pillar remaining and so on. The measure preventing rockburst of fault crack type is to confine fault movement.

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STUDY ON THE RELATIONS AMONG COAL BUMP，ROCKBURST AND MINING TREMOR WITH NUMERICAL SIMULATION

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2003, 22 (11): -1852 doi:
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[PDF 728 KB] (1665)

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After a brief introduction to the phenomena of coal bump，rockburst and mining tremor，their definientia are brought forward in detail and their relations are indicated. The phenomena of coal bump and rockburst are analyzed contrastively by numerical simulation. And the similarities and differences between coal bump and rockbust are put forward. Based on the presented study，it is suggested that the terms of coal bump， rockburst and mining tremor should be applied distinctively.

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ANALYSIS ON FAULT ROCKBURST CONSIDERING STRAIN
RATE AND STRAIN GRADIENT

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2003, 22 (11): -1859 doi:
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[PDF 238 KB] (1368)

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Dynamic shear instability of fault rockburst is analyzed with considering the effect of strain rate and interaction among microstructures. The second shear strain gradient and the function reflecting the effect of strain rate are introduced into the yield function of classical elastoplastic theory. The fault rockburst is simplified as the one-dimensional dynamic shear problem and shear localization is initiated at the peak shear stress. Symmetry of local plastic shear strain in shear band is considered and in the boundary of the band the strain is zero. In addition，the thickness of band is determined according to the maximum local plastic shear strain. Local plastic shear strain and local plastic shear displacement analytically obtained show that these two local parameters increase with strain rate. Beyond the peak shear stress，the structural response of the system composed of fault band and elastic rock outside the fault is proposed. If the post-peak stiffness of the structural response is infinity，the critical loading strain rate of rockburst can be deduced. Once the critical value is achieved，the rock burst occurs certainty. It is found that the critical parameter is dependent on both constitutive parameters of rock materials and the size of structure. Larger strain rate can lead to snap-back of instability of the system. Besides，if the effect of strain rate is neglected，the static results based on gradient-dependent plasticity by Wang et al. can be obtained by simplifying the present theoretical results.

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CORRELATIVITY OF ROCK INHOMOGENEITY
AND ROCK BURST TREND

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2003, 22 (11): -1863 doi:
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[PDF 164 KB] (969)

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The index E/l of rock burst trend is an import parameter which reflects possibility of rock brust，type of rock burst and intensity of rock burst. Based upon a great deal of numerical tests，the stress-strain curve of inhomogeneity rock is studied. It is found that the relation of rock burst trend index E/l and inhomogeneity parameter m is exponential function，and rock burst trend index decreases as inhomogeneity parameter m increases.

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HAZARDS OF ROCK BURST IN ISLAND COAL FACE
AND ITS CONTROL

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2003, 22 (11): -1866 doi:
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[PDF 323 KB] (1316)

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At the island coal face and its surrounding roadways，the stress concentration is at a very high level，the movement of the roof is also drastic，and the influence of the geological tectonics is significant. The more the mining depth is，the more the hazard degree of rock burst is. So the rock burst can be rendered easily near the island coal face，and monitoring，forecasting and controlling of the hazard are necessary. Firstly，the hazard extent of rock burst is analyzed to determine the index of the hazard of rock burst and to present the incipient forecast. Secondly，the rock burst can be forecasted instantaneously with electromagnetic emission (EME) and drillings. Finally，the island coal face should be handled with relieving shot，and the effect of control measures can be proved with EME and drillings. The practices prove that the presented technology can assure the safety and high production efficiency of the coal face.

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IDENTIFICATION WITH ARTIFICIAL NEURAL NETWORK OF LOAD PARAMETERS FROM UNDERGROUND EXPLOSION

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2003, 22 (11): -1870 doi:
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[PDF 220 KB] (1171)

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The artificial neural network model is used to identify the loads parameters from underground explosion according to the field measurement data of ground vibration and computed data with finite element method. The convergence rate of the artificial neural network is improved by using Levenberg-Marquardt optimization method. The influence of measurement noise on identified results is studied. The results of numerical computation show that the proposed identification method is of robustness and ability against measurement noise.

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WAVELET ANALYSIS METHOD OF SURFACE WAVE DETECTION
FOR STEEL TUBE CONCRETE

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2003, 22 (11): -1874 doi:
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[PDF 170 KB] (998)

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The spectral variation mechanism of the transmitted pulse when surface wave meets a defect in steel tube concrete is explained by using the diffraction theory. The characteristic index for quantitatively evaluating the degree of defect damage is given through the method of wavelet analysis. Model tests are carried out，and the results of tests show that the method of surface wave detection and wavelet analysis for evaluating the integrity of steel tube concrete is effective，quick and more accurate.

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WAVELET IDENTIFICATION FOR ROOF-FAILURE-
INDUCED SEISMIC WAVE FEATURE

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2003, 22 (11): -1874 doi:
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[PDF 199 KB] (945)

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Roof is composed of heterogeneous rock. When roof failure happens，a large amount of energy would release in the form of seismic wave. There are many common methods，such as Fourier transformation，filter technique，etc. to identity the abnormal signal of seismic wave，but the identification accuracy is quite low. Multi-resolution wavelet technique is used to identify the first and second variation point，based on the Lipschitz. An example analysis shows that multi-resolution wavelet technique can identify the abnormal signal of seismic wave effectively in different scales，and the omen of roof fall can be grasped accurately. The presented study provides a new idea for the prediction of catastrophe of rock engineering.

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WAVELET ANALYSIS METHOD OF SURFACE WAVE DETECTION
FOR STEEL TUBE CONCRETE

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2003, 22 (11): -1878 doi:
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[PDF 170 KB] (869)

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The spectral variation mechanism of the transmitted pulse when surface wave meets a defect in steel tube concrete is explained by using the diffraction theory. The characteristic index for quantitatively evaluating the degree of defect damage is given through the method of wavelet analysis. Model tests are carried out，and the results of tests show that the method of surface wave detection and wavelet analysis for evaluating the integrity of steel tube concrete is effective，quick and more accurate.

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ROCK DYNAMICS IN CHINA：PAST，PRESENT AND FUTURE

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2003, 22 (11): -1881 doi:
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[PDF 211 KB] (1556)

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The past and present states of some key aspects of the studies on rock dynamics are summarized from eight aspects. The further developments of related research are also discussed.

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SOME PROBLEMS ABOUT SAFTY ANALYSIS OF ROCK ENGEERING UNDER DYNAMIC LOAD

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2003, 22 (11): -1887 doi:
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[PDF 185 KB] (1587)

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Landslides，damage of bedrock，and failure of underground rock structure are the usual disasters induced from blasting and earthquake. It is very important to study the response and stability of rock structure under dynamic load. The present research work on this topic is briefly presented in order to give some suggestions for the further studies.

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TESTING STUDY OF PROTOTYPE AND MODEL COMPARISON ON RESISTING DYNAMICAL LOAD WITH SOIL NAIL SUPPORTING

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2003, 22 (11): -1892 doi:
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[PDF 364 KB] (959)

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The field test results are summarized on the critical resisting force of the loess cavern supported with the soil nails under the isolated top explosion condition. Based on the model simulation law，the model test is conducted. With the test results of the critical resisting force，comparison is made between prototype cavern and the model.

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DYNAMICAL CALCULATION AND ANALYSIS ON
XUANWU LAKE TUNNEL

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2003, 22 (11): -1898 doi:
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[PDF 292 KB] (941)

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Based on the analysis of hydrogeology and structural configuration for the Xuanwu Lake tunnel，the carrying capacity of the tunnel is calculated and analyzed in every selected typical section. From the calculated moment and shearing force，it is known that the structural design is reasonable，and the main structure can meet the request of people's air defence. The presented study results provide a foundation of evaluation on the benefit of tunnel’s combat readiness.

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NUMERICAL ANALYSIS ON DYNAMIC RESPONSE OF
ROCK BOLTS IN MINING ROADWAYS

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2003, 22 (11): -1903 doi:
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[PDF 336 KB] (1163)

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The rock bolts in mining roadways are always subjected to dynamic loading，such as blasting，rock burst and seismic loading. There has been little research into the response of rock bolts to dynamic loading. In this paper，a 2D fast Lagrangian analysis of continua (FLAC) code is used to analyze the influence of seismic loading on bolts (end-anchored and fully grouted). With the numerical analysis，the variation of axial force of bolt with dynamic loading time is obtained. The installation angle of bolts affects the dynamic response of axial force. The max dynamic stress in the bolts induced by seismic loading should be below the yield strength of bolt shank (steel). End-anchored bolts are of more ductibility and can be well suited to dynamic loading than fully grouted bolts. As a result，end-anchored bolt should be used in mining roadways to undergo dynamic loading.

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STUDY ON MEASUREMENT OF BLAST-INDUCED SEISM AND
BUILDING SAFETY CRITERIA

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2003, 22 (11): -1907 doi:
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[PDF 322 KB] (1442)

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The rationality of using particle vibration velocity to describe blast-induced seismic effect is testified by using the stress-strain relation of rock and soil，and characteristics of wave propagation. A lot of seismic wave diagrams and frequency spectrograms are obtained from a lot of blast-induced seism. The propagation law and parameters of seismic wave in different places are studied. The regulations of blasting safety in China are compared with criteria used abroad，and it is theoretically interpreted that the limit value of vibration velocity and vibration frequence should be related to each other and put into the building safety criteria. Some improved methods and optional criteria of vibration velocity of blast seism are proposed.

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STUDY ON RESPONSE OF CONCRETE STRUCTURE AND EMBANKMENT FOUNDATION OF CHANGJIANG RIVER TO BLASTING

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2003, 22 (11): -1912 doi:
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[PDF 209 KB] (872)

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According to the blasting vibration monitoring，the response of concrete structure and embankment foundation of Changjiang river to blasting is analysed. A simple method is presented to determine the safety threshold of embankment foundation of Changjiang river under blasting. The presented study results can be a good reference for the similar engineering.

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ANALYSIS ON BLASTING VIBRATION EFFECT ON PRSTRESSED CABLE OF HIGH SLOPE IN ZIPINGPU PROJECT

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2003, 22 (11): -1916 doi:
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[PDF 216 KB] (934)

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The curves of displacement-time are obtained from multi-point extensometers to analyze the blasting vibration effect of rock excavation of high slope in Zipingqu Project. Based on this，the relation between prestressed cable and rock excavation blast of high slope is gained. The study results are presented for the prestressed cable design in Zipingpu Project，and can be used to guide the construction there as a theoretical basis.

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HORIZONTAL SLICE METHOD OF SLOPE STABILITY ANALYSIS UNDER SEISMIC LOAD BASED ON GENETIC ALGORITHM

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2003, 22 (11): -1919 doi:
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[PDF 296 KB] (1083)

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The computing method for the stability analysis of slopes composed of horizontal layers under seismic load is studied. According to the characteristics of such slopes，horizontal slice method (HSM) is developed and applied to search for the critical slip surface in combination with genetic algorithm (GA) which is of the capability of global convergence. The analysis results of some slopes by the proposed method and the comparisons between the proposed method and other ones show that the proposed method is accurate，reliable and able to find out the global optimal solution.

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TESTING STUDY ON CONTROL STANDARD OF VIBRATION FOR LAYERED ROCK SLOPE BLASTING

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2003, 22 (11): -1924 doi:
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[PDF 200 KB] (891)

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Taking the excavation blasting of a layered rock cutting as background，testing study is made for six lamination blasting. The vibration velocities of particles at different positions away from the explosion sources are measured and the rock mass before and after blasting are detected by wave method. Coupling analysis is made on measured results of both vibration velocity and P-wave velocity，The researches show that the wave velocity of rock mass decreases obviously after blast and the decrement rate of wave velocity increases with the particle vibration velocity of slope when the rock mass of slope is of blast-induced lamination. The greater the particle vibration velocity is，the more serious the degree of rock lamination is. When the particle vibration velocity of slope is smaller than a critical value，the lamination of rock mass can¢t occur. The critical particle vibration velocity is 25.3 cm/s by calculation，which can be used as the control standard of vibration in the layered rock slope blasting.

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STUDY ON BLASTING VIBRATION CONTROL OF CREEP
MASS SLOPE OF LONGTAN HYDROPOWER STATION

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2003, 22 (11): -1929 doi:
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[PDF 196 KB] (1039)

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The blasting vibration of creep mass slope of Longtan hydropower station is observed，interpreted and analyzed. The experiential formula of decay for the blasting earthquake wave is obtained. According to the features of creep mass slope of the hydropower station，the damage standards of the blasting vibration are given. On the basis of the experiential formula of decay and damage standards，the blasting safety control parameters of new cast-in-situ concrete support of the creep mass slope are gained. At last，in the light of construction characteristics of the creep mass slope，the control measures of the blasting vibration are proposed. The presented research achievements have been better applied in practical project，and satisfactory results are obtained.

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EFFECT OF BLAST-INDUCED GROUND MOTION IN LOESS SITES

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2003, 22 (11): -1933 doi:
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[PDF 331 KB] (1025)

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Geomorphologic characteristics in loess areas are closely related to earthquake disasters. Based on the analysis of characteristics of blast-induced ground motion in loess sites，the amplification effect of blast-induced ground motion in different geomorphologic units is revealed. Through comparison of numeric analysis and in-situ test，the inherent relation between blast-induced ground motion and earthquake ground motion is studied. The research shows that blasting test method is feasible in simulating the earthquake response characteristics of loess.

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DYNAMIC STABILITY ANALYSIS OF GRAVITY RETAINING WALLS UNDER BLAST-INDUCED VIBRATION

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2003, 22 (11): -1939 doi:
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[PDF 0 KB] (806)

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Based on the X. Zeng and R. S. Steedman¢s rotation block method，the dynamic stability analysis of gravity retaining walls under blast-induced vibration is conducted. The relationship among the earth acceleration，vibration frequency and the displacement of gravity walls is discussed. The sensitive character of the acceleration threshold to the parameters of gravity walls is studied. Taking account of the accumulated deformation under repeated blast-induced vibration and the site measured data，the earth velocity threshold is estimated. A blasting engineering example shows that the gravity retaining wall is safety，if the blast-induced vibration velocity is lower than the velocity threshold.