scholarly journals Mechanism of Strain Burst by Laboratory and Numerical Analysis

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Manchao He ◽  
Fuqiang Ren ◽  
Cheng Cheng
Keyword(s):  
Rock Mass ◽  
In Situ Stress ◽  
Rock Material ◽  
Brittle Rock ◽  
Strain Burst ◽  
Young’S Moduli ◽  
Key Factor ◽  
Released Energy ◽  
Type Of Failure

Strain burst is often considered to be a type of failure related to brittle rock material; therefore, many studies on strain burst focus on the brittleness of rock. However, the laboratory experiments show that strain burst can not only occur in hard brittle rock-like granite but also in the relatively ductile rock-like argillaceous sandstone. This result proves that behavior of rock material is not the only factor influencing the occurrence of strain burst. What must also be considered is the relative stiffness between the excavation wall/ore body and the surrounding rock mass. In order to further studying the mechanism of strain burst considering the whole system, the engineering geomechanial model and numerical model of strain burst due to excavation are built, respectively. In a series of numerical tests, the rock mass involving the excavation wall as well as roof and floor is biaxially loaded to the in situ stress state before one side of the excavation wall is unloaded abruptly to simulate the excavation in the field. With various system stiffness determined by the microproperties including the contact moduli of particles and parallel bond moduli in the models of roof and floor, the different failure characteristics are obtained. Based on the failure phenomenon, deformation, and released energy from the roof and floor, this study proves that the system stiffness is a key factor determining the violence of the failure, and strain burst is prone to happen when the system is soft. Two critical Young’s moduli ratios and stiffness ratios are identified to assess the violence of failure.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

A Novel Method to Determine the Drilling Fluid Density for Gypsum-Salt Layer

2021 ◽  
Author(s):  
Jitong Liu ◽  
Wanjun Li ◽  
Haiqiu Zhou ◽  
Yixin Gu ◽  
Fuhua Jiang ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Shrinkage Rate ◽  
Fluid Density ◽  
Salt Layer ◽  
Rock Creep ◽  
Key Factor ◽  
Well Abandonment

Abstract The reservoir underneath the salt bed usually has high formation pressure and large production rate. However, downhole complexities such as wellbore shrinkage, stuck pipe, casing deformation and brine crystallization prone to occur in the drilling and completion of the salt bed. The drilling safety is affected and may lead to the failure of drilling to the target reservoir. The drilling fluid density is the key factor to maintain the salt bed’s wellbore stability. The in-situ stress of the composite salt bed (gypsum-salt -gypsum-salt-gypsum) is usually uneven distributed. Creep deformation and wellbore shrinkage affect each other within layers. The wellbore stability is difficult to maintain. Limited theorical reference existed for drilling fluid density selection to mitigate the borehole shrinkage in the composite gypsum-salt layers. This paper established a composite gypsum-salt model based on the rock mechanism and experiments, and a safe-drilling density selection layout is formed to solve the borehole shrinkage problem. This study provides fundamental basis for drilling fluid density selection for gypsum-salt layers. The experiment results show that, with the same drilling fluid density, the borehole shrinkage rate of the minimum horizontal in-situ stress azimuth is higher than that of the maximum horizontal in-situ stress azimuth. However, the borehole shrinkage rate of the gypsum layer is higher than salt layer. The hydration expansion of the gypsum is the dominant reason for the shrinkage of the composite salt-gypsum layer. In order to mitigate the borehole diameter reduction, the drilling fluid density is determined that can lower the creep rate less than 0.001, as a result, the borehole shrinkage of salt-gypsum layer is slowed. At the same time, it is necessary to improve the salinity, filter loss and plugging ability of the drilling fluid to inhibit the creep of the soft shale formation. The research results provide technical support for the safe drilling of composite salt-gypsum layers. This achievement has been applied to 135 wells in the Amu Darya, which completely solved the of wellbore shrinkage problem caused by salt rock creep. Complexities such as stuck string and well abandonment due to high-pressure brine crystallization are eliminated. The drilling cycle is shortened by 21% and the drilling costs is reduced by 15%.

Study on Deformation and Damage of Rock Mass Subject to High In Situ Stress by Using a Elastoplastic Damage Model and Considering the Impact of Weak Planes

2013 ◽  
Vol 838-841 ◽  
pp. 705-709
Author(s):  
Yun Hao Yang ◽  
Ren Kun Wang
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Damage Model ◽  
Back Analysis ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
High In Situ Stress ◽  
Underground Caverns ◽  
The Impact

Large scale underground caverns are under construction in high in-situ stress field at Houziyan hydropower station. To investigate deformation and damage of surrounding rock mass, a elastoplastic orthotropic damage model capable of describing induced orthotropic damage and post-peak behavior of hard rock is used, together with a effective approach accounting for the presence of weak planes. Then a displacement based back analysis was conducted by using the measured deformation data from extensometers. The computed displacements are in good agreement with the measured ones at most of measurement points, which confirm the validities of constitutive model and numerical simulation model. The result of simulation shows that damage of surrounding rock mass is mainly dominated by the high in-situ stress rather than the weak planes and heavy damage occur at the cavern shoulders and side walls.

The Application of Hydraulic Fracturing in Storage Projects of Liquefied Petroleum Gas

2006 ◽  
Vol 306-308 ◽  
pp. 1509-1514 ◽  
Author(s):  
Jing Feng ◽  
Qian Sheng ◽  
Chao Wen Luo ◽  
Jing Zeng
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Stress Measurement ◽  
Test Procedure ◽  
In Situ Stress ◽  
Test System ◽  
Petroleum Engineering ◽  
Liquefied Petroleum Gas

It is very important to study the pristine stress field in Civil, Mining, Petroleum engineering as well as in Geology, Geophysics, and Seismology. There are various methods of determination of in-situ stress in rock mass. However, hydraulic fracturing techniques is the most convenient method to determine and interpret the test results. Based on an hydraulic fracturing stress measurement campaign at an underground liquefied petroleum gas storage project which locates in ZhuHai, China, this paper briefly describes the various uses of stress measurement, details of hydraulic fracturing test system, test procedure adopted and the concept of hydraulic fracturing in arriving at the in-situ stresses of the rock mass.

scholarly journals Rock Mass Behavior under Tunnel Widening in Asymmetric and Symmetric Modes Considering Different Shapes and Parametric Conditions

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 518
Author(s):  
Babar Khan ◽  
Syed Muhammad Jamil ◽  
Jung Joo Kim ◽  
Turab H. Jafri ◽  
Jonguk Kim
Keyword(s):  
Rock Mass ◽  
In Situ Stress ◽  
Design Parameters ◽  
Tunnel Widening ◽  
Tunnel Support ◽  
Mass Behavior ◽  
Rock Types ◽  
The Difference ◽  
Support Conditions

To accommodate traffic volume on roads due to ever-increasing population growth, the widening of highways and motorways is in high demand. Nevertheless, the widening of tunnels on these road networks is quite complex due to the presence of numerous rock types, in situ stress, and different widening modes. To overcome these complexities, eight different tunnel shapes were simulated under varying support conditions for asymmetric and symmetric widening. It was found that the tunnels with a round shape, such as horseshoe and semicircular with flatbed, are more effective for asymmetric widening, whereas the provision of a rounded invert in these shapes can reverse the widening option to symmetric. Furthermore, an insignificant effect of the difference in asymmetric and symmetric widening of regular tunnel shapes, such as box, rectangular, and semi-elliptical, was found. A full factorial design statistical analysis confirmed the decrease in tunnel deformation by using various tunnel support systems and showed a significant deformation difference according to monitoring locations at the tunnel periphery. The deformation difference in the case of both tunnel widening modes was also analyzed according to different design parameters. This study provides a comprehensive understanding of rock mass behavior when the widening of any underground opening is carried out.

Effects of sample disturbance on the stress-induced microfracturing characteristics of brittle rock

1999 ◽  
Vol 36 (2) ◽  
pp. 239-250 ◽  
Author(s):  
E Eberhardt ◽  
D Stead ◽  
B Stimpson
Keyword(s):  
Crack Initiation ◽  
Elastic Stiffness ◽  
In Situ Stress ◽  
Brittle Rock ◽  
Stress Threshold ◽  
Fracture Crack ◽  
Sample Disturbance ◽  
Underground Research Laboratory ◽  
Stress Domains

The effects of sampling disturbance on the laboratory-derived mechanical properties of brittle rock were measured on cored samples of Lac du Bonnet granite taken from three different in situ stress domains at the Underground Research Laboratory of Atomic Energy of Canada Limited. A variety of independent measurements and scanning electron microscope observations demonstrate that stress-induced sampling disturbance increased with increasing in situ stresses. The degree of damage was reflected in laboratory measurements of acoustic velocity and elastic stiffness. Examination of the stress-induced microfracturing characteristics during uniaxial compression of the samples revealed that the degree of sampling disturbance had only minor effects on the stress levels at which new cracks were generated (i.e., the crack initiation stress threshold). Crack-coalescence and crack-damage thresholds, on the other hand, significantly decreased with increased sampling disturbance. The presence of numerous stress-relief cracks in the samples retrieved from the highest in situ stress domains was seen to weaken the rock by providing an increased number of planes of weakness for active cracks to propagate along. A 36% strength decrease was seen in samples retrieved from the highest in situ stress domain (sigma1 - sigma3 approximate 40 MPa) as compared with those taken from the lowest in situ stress domain (sigma1 - sigma3 approximate 10 MPa).Key words: sample disturbance, brittle fracture, crack initiation, crack propagation, material properties, rock failure.

Dynamic response of rock mass induced by the transient release of in-situ stress

2012 ◽  
Vol 53 ◽  
pp. 129-141 ◽  
Author(s):  
Wenbo Lu ◽  
Jianhua Yang ◽  
Peng Yan ◽  
Ming Chen ◽  
Chuangbing Zhou ◽  
...  
Keyword(s):  
Rock Mass ◽  
Dynamic Response ◽  
In Situ Stress

Microseism Induced by Transient Release of In Situ Stress During Deep Rock Mass Excavation by Blasting

2012 ◽  
Vol 46 (4) ◽  
pp. 859-875 ◽  
Author(s):  
Jianhua Yang ◽  
Wenbo Lu ◽  
Ming Chen ◽  
Peng Yan ◽  
Chuangbing Zhou
Keyword(s):  
Rock Mass ◽  
In Situ Stress ◽  
Deep Rock Mass ◽  
Deep Rock
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