Influence exerted by underground excavation shape and by effective stresses on the formation of a tensile strain zone at a depth greater than 1 km

2020 ◽  
pp. 67-75
Author(s):  
Van Min Nguyen ◽  
V. A. Eremenko ◽  
M. A. Sukhorukova ◽  
S. S. Shermatova
Keyword(s):  
Rock Mass ◽  
Cross Sections ◽  
Tensile Strain ◽  
Rock Fracture ◽  
Strain Analysis ◽  
Surrounding Rock ◽  
Underground Excavation ◽  
Secondary Stress ◽  
Principal Stresses ◽  
Mining Depth

The article presents the studies into the secondary stress field formed in surrounding rock mass around underground excavations of different cross-sections and the variants of principal stresses at a mining depth greater than 1 km. The stress-strain analysis of surrounding rock mass around development headings was performed in Map3D environment. The obtained results of the quantitative analysis are currently used in adjustment of the model over the whole period of heading and support of operating mine openings. The estimates of the assumed parameters of excavations, as well as the calculations of micro-strains in surrounding rock mass by three scenarios are given. During heading in the test area in granite, dense fracturing and formation of tensile strain zone proceeds from the boundary of e ≥ 350me and is used to determine rough distances from the roof ( H roof) and sidewalls ( H side) of an underground excavation to the 3 boundary e = 350me (probable rock fracture zone). The modeling has determined the structure of secondary stress and strain fields in the conditions of heading operations at great depths.

Seepage Stability Analysis for Surrounding Rock Mass of Diversion Tunnel by FEM

2013 ◽  
Vol 787 ◽  
pp. 622-625
Author(s):  
Yun Feng Xu ◽  
Zhen Zhong Shen ◽  
Chao Xin Shao
Keyword(s):  
Finite Element Method ◽  
Rock Mass ◽  
Working Conditions ◽  
Cross Sections ◽  
Surrounding Rock ◽  
The Other ◽  
Seepage Field ◽  
Diversion Tunnel ◽  
Pressure Method ◽  
Seepage Model

Based on the actual conditions of the project and related experience, the seepage model of diversion tunnel and its surrounding rock mass was built to analyze its seepage stability. The seepage field was calculated by using finite element method (FEM) and cut-off negative pressure method. Two typical cross-sections and working conditions were chosen to evaluate the seepage stability of the surrounding rock mass. According to the results, the seepage gradient is larger when one tunnel is filled with water while the other is empty. The maximum seepage gradient is less than the allowable seepage gradient, so the surrounding rock mass of the diversion tunnel can meet the demand of seepage stability.

scholarly journals Blast Induced Damage to Surrounding Rock Mass in an Underground Excavation

2014 ◽  
Vol 2 (1) ◽  
Author(s):  
Harsh Kumar Verma ◽  
Narendra Kumar Samadhiya ◽  
Mahendra Singh ◽  
Vilugundam Venkat Ramana
Keyword(s):  
Rock Mass ◽  
Surrounding Rock ◽  
Underground Excavation

scholarly journals STRESS-STRAIN BEHAVIOR OF ROCK MASS AROUND CYLINDRICAL EXCAVATIONS WITH THE PRESET CAUCHY STRESS STRESSES AND DISPLACEMENTS AT THE BOUNDARIES

2021 ◽  
Vol 2 (4) ◽  
pp. 158-163
Author(s):  
Anvar I. Chanyshev ◽  
Igizar M. Abdulin
Keyword(s):  
Rock Mass ◽  
Symmetry Axis ◽  
Strain Analysis ◽  
Polar Angle ◽  
Surrounding Rock ◽  
Rotation Vector ◽  
Cauchy Stress ◽  
Stress Strain ◽  
Strain Behavior

The authors solve the problem on the stresses and strains of rock mass around a cylindrical excavation with the preset vectors of the Cauchy stresses and displacements at the boundary. It is assumed that the surrounding rock mass is elastic. Along the cylindrical excavation (free of stresses), displacements are measured as functions of two surface coordinates (polar angle and length along the symmetry axis of the excavation). These measurements are used to determine all components of tensors of stresses and strains at the boundary, and all coordinates of rotation vector. It is shown how this information can be used in the stress-strain analysis of rock mass farther from the excavation.

Experimental Study on Creep of Surrounding Rock Mass in Argillaceous Soft Rock Tunnel

2012 ◽  
Vol 193-194 ◽  
pp. 826-830 ◽  
Author(s):  
Qiu Yan Fan ◽  
Jia Yan Lu ◽  
Zhen Zhu
Keyword(s):  
Rock Mass ◽  
Rock Fracture ◽  
Soft Rock ◽  
Creep Damage ◽  
Surrounding Rock ◽  
Laboratory Simulation ◽  
Creep Process ◽  
Laboratory Model ◽  
Accelerated Creep ◽  
Rock Tunnel

Due to the complexity of underground engineering, study on creep characteristics of surrounding rock mainly adopts laboratory simulation experiment. Recently, the similar materials are used to do the experiment both at home and abroad, yet it can't reflect the original nature and others of rock fissure in original rock mass. Through the field collection of undisturbed sample of Tertiary mudstone, the conclusions are made by laboratory model test on surrounding rock of underground tunnel and creep process regularity and failure mechanism in the surrounding rock in this paper as follows: there are three obvious stages of creep under certain stress levels, which is measured on the surface of surrounding rock mass in argillaceous soft rock tunnel--decay creep ,steady creep and accelerated creep. The surrounding rock will produce the accelerated creep damage when the stress level is over a threshold value. Creep damage of surrounding rock mainly includes the forms of roof sinking, floor working up, and forming a macro- fracture surfaces etc. Test results showed that the undisturbed surrounding rock fracture would be dissimilar to the homogeneous surrounding rock without fracture in damage model, and original fissure have a larger effect on creep damage of surrounding rock.

scholarly journals Stability Analysis of Surrounding Rock in Multi-Discontinuous Hydraulic Tunnel Based on Microseismic Monitoring

2021 ◽  
Vol 12 (1) ◽  
pp. 149
Author(s):  
Xiang Zhou ◽  
Biao Li ◽  
Chunming Yang ◽  
Weiming Zhong ◽  
Quanfu Ding ◽  
...  
Keyword(s):  
Rock Mass ◽  
Shear Failure ◽  
Rock Fracture ◽  
Source Parameters ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Lateral Migration ◽  
Diversion Tunnel ◽  
Structural Plane ◽  
The Stability

The diversion tunnel of a hydropower station is characterized by low quality surrounding rock and weak structural planes. During excavation, rock mass spalling and cracking frequently occur. To evaluate the stability of a rock mass during tunnel excavation, high-precision microseismic monitoring technology was introduced to carry out real-time monitoring. Based on the temporal and spatial distribution characteristics of microseismic events, the main damage areas and their influencing factors of tunnel rock mass were studied. By analyzing the source characteristic parameters of the concentration area of microseismic activities, the rock fracture mechanism of the concentration area was revealed. The 3D numerical model of diversion tunnel was established, and the deformation characteristics of the rock mass under the control of different combination types of weak structural planes were obtained. The results showed that the microseismic event was active between 29 October 2020 and 6 November 2020, and the energy release increased sharply. The main damage areas of the rock mass were located at Stakes K0 + 500–K0 + 600 m. Microseismic source parameters revealed that shear failure or fault-slip failure induced by geological structures had an important influence on the stability of the surrounding rock. The numerical simulation results were consistent with the microseismic monitoring results and indicated that among the three kinds of structural plane combination types, including “upright triangle”, “inverted triangle” and “nearly parallel”, the “upright triangle” structure had the most significant influence on the stability of the surrounding rock. In addition, the maximum displacement of the surrounding rock had a trend of lateral migration to the larger dip angle in the three combined structural plane types. The research results will provide significant references for the safety evaluation and construction design of similar tunnels.

scholarly journals Enhancement of rock bolt performance through “active” ground control

2021 ◽  
pp. 27-30
Author(s):  
E. A. Razumov ◽  
◽  
S. I. Kalinin ◽  
V. G. Venger ◽  
E. Yu. Pudov ◽  
...  
Keyword(s):  
Rock Mass ◽  
Rock Fracture ◽  
Ground Control ◽  
Structural Components ◽  
Rock Bolts ◽  
Mining Depth ◽  
Rock Bolting ◽  
Geological Conditions ◽  
Roof Rocks ◽  
Roof Support

The research has proved that rock mass stability can be ensured using steel resin rock bolting including rods, fast-setting resin capsules, bearing plates, strapping and tension nuts. Interaction of these structural components with roof rocks and sidewalls involves obligatory displacement of rocks. The article presents the studies into applicability of steel resin rock bolting in difficult geological conditions in coal mines in Kuzbass. The steel resin rock bolting is considered in this case as the method of ‘active’ ground control. The ‘active’ ground control consists in the capacity of steel resin rock bolts to alter main strength characteristics of rocks, to increase their resistance and stability, and, thereby, to ensure efficiency of roof support. It is found that horizontal and vertical stresses in underground excavations depend on the mining depth. It is proved that rock bolts installed in the roof rocks can prevent or confine rock fracture.

scholarly journals Study on Mechanical Properties and Control Technology of Surrounding Rock in the Fracture Zone of a Roadway

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yushun Yang ◽  
Zhiming Fang ◽  
Guangying Ji ◽  
Baigao Zhao ◽  
Sijiang Wei
Keyword(s):  
Rock Mass ◽  
Fracture Zone ◽  
Rock Fracture ◽  
Industrial Test ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Three Dimensional Model ◽  
Silty Mudstone ◽  
Fracture Development ◽  
Fault Fracture Zone

We aim at the problem of the large deformation and difficult control of surrounding rock when passing through a fault fracture zone in the centralized rail transportation lane along the south wing of Xinyi Coal Mine; the stress environment and failure mechanism of surrounding rock are analyzed through field investigation, numerical simulation, and field industrial test. The instability of the surrounding rock in the fault fracture zone was considered to be the result of the joint effect of the surrounding rock fracture development, lithology differences, water gushing occurrences, low strength of the original support, high in situ stress, and fault-related tectonic stress. Rock blocks are collected on site at the fracture zone, and the remoulded samples are prepared for mechanical experiments in the laboratory. The basic mechanical parameters of the roadway passing through silty mudstone, sand-mudstone interlayer, and fine sandstone were analyzed. A three-dimensional model is established to analyze the distributions of the stress, deformation, and plastic area in the surrounding rock mass after the tunnel passes through, considering both a single-rock mass and a multilayer-rock mass. Based on the above analysis, the “closed support + shotcrete + grouting + anchor mesh cable coupling support” is proposed. Three stations were arranged on site to observe the mine pressure, and the field industrial test shows that, within the 100 days of observation, the maximum roof-to-floor convergence is 38 mm, while the maximum horizontal convergence is 56 mm. The overall reinforcement effect of the roadway is good, the surface is smooth, and there is no phenomenon of concrete cracking and bolt fracture.

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