Mechanical Characteristics Of Rock Mass Research Articles

Research on rock triaxial cyclic loading and unloading characteristics based on PFC3D

Numerical methods provide a new way for solving complex geotechnical engineering problems. Firstly, we review the emergence and development of numerical methods, and introduce the basic principles of particle flow discrete element and its application in geotechnical engineering. After that, a method of servo combination of cylinder and loading plate is used, the numerical simulation of the three-dimensional rock in triaxial loading and unloading test is carried out by PFC3D software, and the loading and unloading mechanical characteristics of rock mass under the linear elastic contact constitutive model and parallel bonded contact constitutive model are studied respectively, and we obtain the triaxial loading and unloading stressstrain curves of rock under the elastic constitutive model and elastoplastic constitutive model. The residual strains and hysteresis phenomena of the rock under the two constitutive models are analysed, and the feasibility of the particle flow discrete element method in studying the mechanical characteristics of rocks is demonstrated.

Study on Rock Mass Classification Methods Used in the Geological Disposal of High-level Radioactive Waste

The conventional methods of rock quality classification mainly focus on the constructability of rock mass, while the long-term safety requirements of the high-level radioactive waste (HLW) disposal are not considered. Therefore, two rock suitability classification methods for geological disposal projects, the Rock Suitability Criterion (RSC) and the QHLW methods were systematically compared by evaluating the rock suitability of the ONKALO site for geological disposal in Finland. The suitability of the ONKALO site was analyzed by evaluating the permeability, geochemical condition, and integrity of rock mass, according to the RSC method. Meanwhile, the QHLW method was used to evaluate the rock mass suitability by analyzing the fault zone influence, hydrogeochemical characteristics, temperature influence, permeability, strength-stress ratio, and integrity of rock mass. Then, the advantages and disadvantages of the two methods were discussed. We found that the results obtained with RSC are consistent with those with QHLW. While RSC gives more detailed chemical properties of groundwater and mechanical characteristics of rock mass, QHLW performs better in evaluating the permeability of rock mass. Besides, RSC is a qualitative or semi-qualitative method with some site-specific criteria, while the QHLW is a quantitative method with higher universality. Based on the above results and conclusions, a new version of QHLW at the tunnel scale was finally proposed by incorporating the advantages of RSC.

The Dynamic Response and Failure Model of Thin Plate Rock Mass under Impact Load

The layered rock mass widely exists in mining, construction, transportation, and water conservancy projects, and the damage phenomena of plate crack and spalling often occurs in the process of coal and rock dynamic disaster in deep mining. Therefore, the rock mass nearby excavation surface is usually considered to be composed of layers of thin plate rock mass to reveal the damage and failure mechanism of rock mass. In the whole dynamic process of mining and coal and rock dynamic disaster, rock mass would bear the dynamic disturbance from mine earthquake, and at present, the mechanical characteristics of rock mass are mainly studied under static load, while dynamic mechanical response characteristics and the mechanisms of dynamic damage, failure, and disaster-causing are still unclear. This study mainly focused on the dynamic response characteristic and failure mechanism of rock mass based on a rectangular thin plate model. The frequency equations and deflection equations of the thin plate rock mass with different boundary conditions (S-F-S-F, S-C-S-C, and C-C-C-C) were established under free vibration by the thin plate model and the dual equation of the Hamilton system, and the deflection equations under impact load were derived based on the Duhamel integral. And then, the effective vibration modes of the thin plate rock mass with different boundary conditions and their natural frequencies were obtained by Newton’s iterative method. Based on the third-strength theory and the numerical simulation results by LS-DYNA, the maximum shear of the effective vibration modes and the processes of damage and failure under impact load were analyzed. The research results showed that the initial position of damage and failure may be determined by effective vibration mode with the lowest frequency; the develop tendency of which by the combined actions of other effective vibration modes and the effective vibration modes with lower frequency could have greater influence on the process of damage and failure of the thin plate rock mass, which are beneficial to revealing the mechanism of coal and rock dynamic disaster.

Mechanical Characteristics of Rock Mass under Loading for Retrofit of Underground Fallout Shelters for Protection of Civil Population

Nowadays there’s still the questions in context of global strategy about prevention and protection of civilian population and critical infrastructure even when in the present doctrine the global powers "forgets" about the old strategy of nuclear warfare. That means that we still should think about retrofit those of underground spaces that was decommissioned in last years and to start thinking about reuse of mining shafts in rock mass as a fallout shelters for protection of civil population. By rock mass we mean the volume of rock necessary to represent a model of the structure of the rocks enclosed in it and determined by a specific task related to the impact of external forces (boundary conditions) on this volume. Currently, there is no universally accepted point of view on the possibility of an approach to the processes of massifs deformation; rocks being under load in various geological conditions from a single common point, the question now arises of creating the most realistic mechanical model of the massif. In this paper were summarizing some mathematical apparatus for rocks mechanical characteristics within the massif loading processes for underground structures model.

Cancelling ore pillars in large-scale coastal gold deposit: A case study in Sanshandao gold mine, China

According to the actual conditions in Sanshandao Gold Mine, the cancelling ore pillars mining method was researched. Firstly, a series of tests for the physical and mechanical characteristics of rock mass were carried out and a quality classification system of rock mass applied in coastal metal deposit was established. Secondly, the reasonable demarcation depth of cancelling ore pillars was simulated using the finite element method, and the simulation results show that the ore pillars can be cancelled below the level of −555 m. Thirdly, a novel layer-backfill mining method of room-pillar alternation was designed to reduce the disturbance and settlement of terrain in mining area. Engineering practice shows that the new mining method enhanced the mining output and relieved rock disturbance. Furthermore, the settlement of the roof strata was small and no disaster occurred. The new mining technology effectively controlled the deformation of the terrain, indicating that the mining of the large-scale gold coastal deposit in Sanshandao Gold Mine was achieved safely, efficiently, and with a low loss rate.

Influence Mechanism of Grouting on Mechanical Characteristics of Rock Mass

Grouting technology has been widely used in all fields of geotechnical and civil engineering. Prospective engineering objectives including reinforcement of rock mass and groundwater leakage treatment can be achieved by grouting which will change the mechanical parameters of rock mass such as strength, elastic modulus, and coefficient of permeability. In this paper, rock mass is assumed as a composite material consisting of rock particles and random microcracks initially. Since part or all of the cracks will be filled with cement slurry after grouting, rock mass consists of rock particles, grout condensate, and some or no random microcracks after grouting. The damage constitutional law of the mesoscopic element is established based on the theory of mesoscopic damage mechanics. With the heterogeneity of the components of rock mass considered, the variation of mechanical characteristics of rock mass is studied before and after grouting. And the influence mechanism of grouting on rock mass is investigated at mesoscale level.

Study on the Constitutive Model of Visco-Elasticity-Plasticity Considering the Rheology of Rock Mass

Considering the rheological mechanical characteristics of rock mass, a viscous-plastic model of rock mass which can describe the acceleration creep stage of rock mass was proposed. Moreover, combining with viscous-elastic shearing rheological model of rock mass in series, a new constitutive model of visco-elasticity-plasticity considering the rheology was constructed. Due to the shearing rheological curves of granite, the model of visco-elasticity-plasticity considering the rheology was identified and the rheological parameters of the model were obtained. The comparison between the viscous-elastic-plastic rheological model of rock mass and experimental result of granite shows that the accelerating rheological properties of rock mass can be depicted effectively by the constitutive model of visco-elasticity-plasticity considering the rheology.

Undersea safety mining of the large gold deposit in Xinli District of Sanshandao Gold Mine

The exploration of undersea resources becomes popular as land resources decrease. Researches were conducted with emphasis on the safety and efficiency of undersea mining of the large gold deposit in Xinli District of Sanshandao Gold Mine. A series of tests for the physical and mechanical characteristics of rock mass were carried out, and the three-dimensional geo-stress distribution was tested in the mining area. Further, a similar experimental simulation platform, which revealed the mechanism of water inrush and ascertained the reasonable thickness of the safety isolate layer, was established for the undersea mining. Meanwhile, the feasibility of cancelling the ore pillars and the safety conditions was checked by numerical simulation. The simulation results show that it is safe to exploit the ore body below the −85 m level (presently, the exploitation level is below −160 m in Xinli District), and the ore pillars can be cancelled below the −560 m level. Furthermore, a novel backfill method was designed to reduce the rock strata disturbance and settlement, and the settlement of roof strata was monitored during the mining process. Engineering practice shows that the settlement of roof strata was small and that no disaster happened. This indicates that the undersea safety mining technology of the large gold deposit is achieved in Xinli District.

Structural Plane of Rock Mass Strength Characteristics and its Impact on Groundwater

The strength characteristic of discontinuity is one of the most important mechanical characteristics of rock mass, and its strength dominates the strength and deformation of joint rock mass. The underground water has an important influence on the strength of discontinuity. In this paper, the strength theory of joint rock mass was summarized and analyzed; further, two kinds of failure mode of joint rock mass which are joint shear failure and rock shear failure were proof. Considering the impact of underground water, the effective stress principle was introduced, and base on it, the joint shear failure strength rule of the saturated rock mass was built. When the influence of underground water on joint strength is studied, the shear strength formula has important theoretical and realistic significance.

Experimental Study on Mechanical Characteristics of Deformation of Red Sandstone

For geotechnical engineering, it has great significance to research the mechanical characteristics of rock mass under three dimensional stresses. Through triaxial compression failure test, the characteristics of stress-strain curve and deformation of red sandstone from Sichuan under different confining pressures has been analyzed. The results show that: with the increment of confining pressure, the failure mode of rock mass changes from brittle failure to ductile failure gradually, and an obvious yield platform appears near the peak strength of stress-strain curve; the elastic modulus, deformation modulus, peak strain and residual strain of rock sample increase with the increment of confining pressure, the elastic modulus and deformation modulus are not a fixed value, and the relation between deformation parameter and confining pressure can be fit through quadratic curve.

Effect of fissure water on mechanical characteristics of rock mass

In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we prepared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydrodynamic pressure is the lowest.

The impact of mechanical properties of rock to the collision of rock piece

The paper presents the analytical solution of the rock piece motion considering influences of geometrical and mechanical characteristics of rock mass on the arbitrary slope. The main objective of the paper is to determine the motion of the rock piece considering possibility of rock piece failure due to collision. Brief description of the analytical solution of the rock piece motion on a steep slope is given. The laboratory tests were performed to determine uniaxial compressive strength and elastic properties of the considered rock mass. Further, velocities that cause rock piece failure were determined. These maximum velocities indirectly belong to certain mass of rock piece and can be lower than velocities calculated in rock-fall analysis for certain slope geometry. Consequently, the energy magnitude is limited, because at certain velocity and mass of rock piece bigger pieces crash at collision.