Stochastic Three-Dimensional Joint Geometry Model and the Properties of REV for a Jointed Rock Mass

2014 ◽  
Vol 1079-1080 ◽  
pp. 266-271
Author(s):  
Wen Hui Tan ◽  
Zhong Hua Sun ◽  
Ning Li ◽  
Xiao Hong Jiang
Keyword(s):  
Rock Mass ◽  
Probability Distributions ◽  
Three Dimensional ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Open Pit ◽  
Mechanical Parameters ◽  
Geometry Model ◽  
Joint Geometry ◽  
3D Network

The lithology of rock mass isnon-homogeneity，anisotropy, andexists size effect. The mechanical parameters of rock mass gotten by engineeringapproaches cannot reflect these properties. Therefore, a newmethod of determining the mechanical parameters of jointed rock mass isproposed: gneiss in Shuichang open-pit mine was selected as a case, thefracture system of the rock mass was measured and analyzed by non-contactmeasuring system of 3GSM and probabilisticmethod,the probability distributions of geometry parameters were analyzed and a 3Djoint geometry model was made by using the program of 3D network modeling.Cubes with different sizes were selected to be tested by tri-axial compressionof numerical simulation with 3DEC based on the 3D network model of joints,thus, the REV and its mechanical parameters were determined, which providedcredible parameters for slope stability analysis.

scholarly journals Primary Investigation on Equivalent Anchoring Method of Jointed Rock Mass Tunnel and Its Engineering Application

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Min Gao ◽  
Shanpo Jia
Keyword(s):  
Rock Mass ◽  
Three Dimensional ◽  
Engineering Application ◽  
Friction Angle ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Reinforcement Effect ◽  
Rock Bolts

Rock bolts, one of the main support structures of the tunnel, can improve the stress state and mechanical properties of the surrounding rocks. The rock bolts are simulated by bar or beam elements in present numerical calculations for most 2D tunnel models. However, the methods of simulating rock bolt in three-dimensional models are rarely studied. Moreover, there are too many rock bolts in the long-span tunnel, which are hardly applied in the 3D numerical model. Therefore, an equivalent anchoring method for bolted rock masses needs to be further investigated. First, the jointed material model is modified to simulate the anisotropic properties of surrounding rock masses. Then, based on the theoretical analysis of rock bolts in reinforcing mechanical properties of the surrounding rock masses, the equivalent anchoring method of the jointed rock mass tunnel is numerically studied. The equivalent anchoring method is applied to the stability analysis of a diversion tunnel in Western China. From the calculation results, it could be found that the reinforcement effect of rock bolts could be equivalently simulated by increasing the mechanical parameter value of surrounding rocks. For the jointed rock mass tunnel, the cohesion and internal friction angle of the surrounding rocks are improved as 1.7 times and 1.2 times of the initial value, which can simulate the reinforcement effect of rock bolts. Comparing with analytical results, the improved internal friction angle is nearly consistent with analytical result. The reinforcement effect of rock bolts is simulated obviously when the mechanical parameters of surrounding rocks are increased simultaneously. The engineering application shows that the equivalent anchoring method can reasonably simulate the effect of rock bolts, which can provide reference for stability analysis of three-dimensional tunnel simulations.

scholarly journals Initiation of residual stress zone during blasting in jointed granite rock mass in operation of Priargunsky Industrial Mining and Chemical Union

2020 ◽  
pp. 60-64
Author(s):  
V. N. Tyupin ◽  
Keyword(s):  
Rock Mass ◽  
Experimental Studies ◽  
Confining Pressure ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Open Pit ◽  
Initiation Mechanism ◽  
Technical Literature ◽  
Short Delay ◽  
Granite Rock

Russian and foreign technical literature says that blasting in jointed rock mass induces zones with altered physical properties and geomechanical behavior beyond the perimeter holes. These zones are identified as the crushed zone, radially fractured zone, spalling zone and shattered zone. The shattered zone lacks scientific attention although this zone can reach the width of (30–170)db (db—blasthole diameter) in open pit mines and (25–75)db in underground mines. The earlier implemented research answers the question on quantitative change in the stresses and strains of a jointed rock mass during blasting. The initiation mechanism of the shattered zone remains unclear. This study aims to find the initiation mechanism of the shattered zone in jointed rock mass and to determine its stress state after blasting. Three series of full-scale experimental studies have been performed in jointed granite rock mass using acoustic emission methods, ultrasonic techniques and deformation measurements. It is found that in the shattered zone, blocks in the jointed rock mass displace radially from the blast holes with deformation of the joint surfaces and with elastic strains preserved after blasting. For this reason, this zone is qualified as the zone of blast-induced residual stresses. The article gives the formula for the residual radial compressive stresses under short-delay multi-row blasting. The numerical calculation using this formula and the actual mine data prove the formula validity. The method of destressing blasting is proposed to unload rockburst-hazardous rock mass from stresses in the areas of the confining pressure phenomena such as spalling and sloughing. This method has been trialed in Priargunsky’s mines in granite rock mass (1400 m long area was unloaded from stresses in mines). The authors highly appreciate participation of I. I. Shishkin, B. M. Belyaev, V. M. Pankov and V. A. Pazdnikova in the experimental research.

Study on the Strength of Jointed Rock Mass

2007 ◽  
Vol 353-358 ◽  
pp. 381-384 ◽  
Author(s):  
Zhi Gang Zhang ◽  
C.S. Qiao ◽  
Xiao Li
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Reduction ◽  
Mechanical Parameters ◽  
Highway Tunnel ◽  
Geometric Configurations ◽  
Under Construction

Based on the structure of the rock mass surrounding a highway tunnel under construction, a new methodology for defining the strength of jointed rock mass is proposed. The laboratory experiments and numerical simulations of rock samples, including both intact rock and rock with a single typical joint, are carried out to ensure that the mechanical parameters of the rock and the joint can be obtained. In addition, the strength of the rock mass surrounding the tunnel, without resorting to the difficult task of sampling and testing of large-scale rock mass, is evaluated by using the proposed method. It is shown that the strength reduction of rock mass is governed by the geometric configurations as well as the mechanical properties of the joints, and that the presence of joints results in the non-linearity of the pre-peak region.

Geomechanical behavior of jointed rock mass in the large-scale blast impact zone

2020 ◽  
pp. 11-14
Author(s):  
V. N. Tyupin ◽  
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Measurement Data ◽  
Ground Surface ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Open Pit ◽  
Velocity Versus ◽  
Research Findings ◽  
Seismic Impact

The review of literature sources has allowed determining the mechanism of seismic blasts waves in jointed rock mass. The author presents the theoretical formulas for calculating stresses, relative strains and displacement velocities induced in rock mass by large-scale blasts. The formulas take into account the detonation characteristics of explosives, the borehole diameter, the length of explosive charges, the number of simultaneously blasted charges per groups and the factor of explosion energy redistribution to rock throw. Moreover, the formulas include the properties of rocks between the blasting point and a guarded object, and on the exposed surface of a guarded object. The compressive stresses, relative strains and displacement velocities in rocks are calculated from the formulas. The theoretically found change in the displacement velocity versus distance agrees with the field measurement data obtained in an open pit mine of Polyus company. The formulas of stresses and relative strains were used to define seismic impact exerted by large-scale blasts on the barrier of dry dock No. 1. Based on the calculated results, the recommendations are developed on reduction of seismic impact of blasts during dredging in the dock. The research findings are applicable to developing blasting regulations toward reduction in seismic impact of large-scale explosions on exposed surfaces in rock mass, as well as on the ground surface structures and buildings.

Numerical Research on Anisotropy Mechanical Parameters of Fractured Rock Mass

2012 ◽  
Vol 524-527 ◽  
pp. 310-316 ◽  
Author(s):  
Pei Feng Sun ◽  
Tian Hong Yang ◽  
Qing Lei Yu ◽  
Wei Shen
Keyword(s):  
Rock Mass ◽  
Elastic Modulus ◽  
Scale Effects ◽  
Fractured Rock ◽  
Deformation Modulus ◽  
Reference Value ◽  
Fracture Network ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Mechanical Parameters

With ShapeMetriX3D rock non-contact measuring technology, structural planes’ distribution of MiaoGou iron mine slope is got. Then, the Mont-Carlo method is used to create equivalent fracture network, with that scale effects and anisotropic properties of rock mass are studied by RFPA2D, considering different scales and directions in statistical window. The results show that both deformation modulus and the strength of the rock mass’s REV are 2.5 m. Furthermore, the strength ratio of filler to rock (K) and the strength of the rock mass fit the logarithmic relationship in rough, while the elastic modulus ratio of filler to rock (M) and the strength of the rock mass fit the linear relationship in rough. The strength of no joints rock mass is much stronger than three times of the strength of jointed rock mass, but the rock mass elastic modulus of no joints is less than 1.6 times of the elastic modulus of jointed rock mass. The research results are directive and have reference value for the study of anisotropy mechanical parameters of rock mass engineering.

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