scholarly journals Research on the escape mechanism and influencing factors of harmful gas induced by blasting excavation in deep rock tunnel

2021 ◽  
Author(s):  
Yi Luo ◽  
Hangli Gong ◽  
Dengxing Qu ◽  
Xinping Li ◽  
Shaohua Hu ◽  
...  
Keyword(s):  
Coupling Effect ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Water Soluble ◽  
Damage Effect ◽  
Escape Mechanism ◽  
Blasting Excavation ◽  
Deep Rock ◽  
Explosion Load

Abstract The escape of toxic and harmful gases is a common disaster effect in tunnel engineering. Frequent drilling and blasting excavation disturbances under high in-situ stress environment will inevitably lead to cumulative damage effect on surrounding rock, which will increase the permeability coefficient of surrounding rock, increase the risk of toxic and harmful gas escape, and seriously endanger construction safety. In this paper, based on real-time monitoring data of harmful gases during blasting and excavation of Yuelongmen Tunnel on Chengdu-Lanzhou Railway, this study summarized laws and distribution characteristics of harmful gas escape intensified by the blasting excavation, and the effectiveness of shotcreting and grouting for water blocking to inhibit gas escape is verified. Then, taking water-containing and gas-containing voids as carriers, considering the influence of different in-situ stress, explosion load and void parameters (including void pressure, void diameter and distance between void and tunnel), to carry out research on the escape mechanism of water-soluble (H 2 S) and insoluble (CH 4 ) toxic and harmful gases under the coupling effect of stress-seepage-damage. The relationship between the amount of harmful gas escaped and the damage degree of the surrounding rock of the tunnel is analyzed, and the functional relationship between it and the in-situ stress, explosion load and cave parameters is established. The results further demonstrate that the amount of escaped harmful gases, such as methane and H 2 S is closely related to lithology of surrounding rock, occurrence conditions of the deep rock mass, development degree of structural fractures and void parameters. The damage of surrounding rock caused by dynamic disturbance during blasting excavation is the main reason of aggravating harmful gas escape. The research results can provide a theoretical reference for preventing harmful gas from escaping in the similar engineering construction.

scholarly journals Experimental Study on the Effects of In Situ Stress on the Initiation and Propagation of Cracks during Hard Rock Blasting

2021 ◽  
Vol 11 (23) ◽  
pp. 11169
Author(s):  
Guangliang Yan ◽  
Qibo Yang ◽  
Fengpeng Zhang ◽  
Qiqi Hao ◽  
Xiulong Wang ◽  
...  
Keyword(s):  
Hard Rock ◽  
Morphological Characteristics ◽  
In Situ Stress ◽  
Static Stress ◽  
Rock Blasting ◽  
Crack Network ◽  
Initiation And Propagation ◽  
Blasting Excavation ◽  
Deep Rock

In situ stress is one of the most important factors affecting rock dynamic fractures during blasting excavation of deep rock mass that generally is hard rock. In this research, crater blasting experiments on hard rock under different uniaxial static stresses were conducted to investigate the initiation and propagation process of crack networks that were induced by coupled dynamic and static loads. Furthermore, the effects of anisotropic static stress fields on the initiation and propagation of crack networks during hard rock blasting, and the crack network morphological characteristics were analyzed and elucidated. The experimental results showed that the static stress field changed the process of crack network initiation and propagation during hard rock blasting, and then control the crack network morphology. Under uniaxial static stress, the crack network was elliptical with the long axis parallel to the static stress. In addition, the larger the anisotropic static stress is, the more obvious the elliptical morphology of the crack network. Moreover, the static stress lead to the delay of crack formation which indicates that the delay time during millisecond blasting excavation of deep rock mass should be adjusted appropriately according to the in situ stress. A stress-strength ratio (SSR) of 0.15 is the threshold value where static stress may have a significant effect on the initiation and propagation of a crack network. Meanwhile, the strain field prior to crack initiation during rock blasting controlled the morphological characteristics of the crack network. Finally, the mechanism of static stress affecting propagation and morphology of crack network was revealed theoretically.

Development of a model to predict vibrations induced by transient release of in-situ stress

2015 ◽  
Vol 23 (11) ◽  
pp. 1828-1843 ◽  
Author(s):  
Wenbo Lu ◽  
Yong Fan ◽  
Jianhua Yang ◽  
Peng Yan ◽  
Ming Chen
Keyword(s):  
Correlation Coefficient ◽  
Finite Impulse Response ◽  
Amplitude Spectrum ◽  
Multivariate Regression Analysis ◽  
In Situ Stress ◽  
Proposed Model ◽  
Blasting Excavation ◽  
Negative Effect ◽  
Deep Rock

During the process of deep rock mass excavations by drill and blast, transient release of in-situ stress (TRIS) induced vibrations have a negative effect on the safety and stability of nearby structures. However, little attention has been focused on the prediction of peak particle velocity (PPV) of TRIS induced vibrations. To forecast the PPV of TRIS induced vibrations, a new model was set up by dimensional analysis method based on an analysis of PPV influencing factors. To train and test the prediction model proposed in this paper, firstly, TRIS induced vibrations were identified and separated from the recorded vibrations during a blasting excavation of deep rock masses in the Jinping II hydropower station by the methods of amplitude spectrum analysis and finite impulse response digital filter, and then, unknown coefficients in the proposed model were calculated via multivariate regression analysis from the collected data of upper part excavation. Finally, for the lower part excavation, the separated and predicted PPV of TRIS induced vibrations were compared. In addition, the correlation coefficient and root mean square error (RMSE) were compared between the proposed model and the other commonly used model. Results seem to indicate that the proposed model with a higher correlation coefficient and a smaller RMSE is the better option for predicting the PPV of TRIS induced vibrations.

scholarly journals Development of a Model to Predict Vibrations Induced by Blasting Excavation of Deep Rock Masses under High In Situ Stress

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yong Fan ◽  
Xianze Cui ◽  
Zhendong Leng ◽  
Yurong Zhou ◽  
Junwei Zheng ◽  
...  
Keyword(s):  
Prediction Model ◽  
In Situ Stress ◽  
Rock Masses ◽  
Vibration Data ◽  
High In Situ Stress ◽  
Dimension Analysis ◽  
Proposed Model ◽  
Blasting Excavation ◽  
Deep Rock

During the process of blasting excavation of deep rock masses under high in situ stress, energy produced by the explosive and the strain energy released by rock mass excavation constitute the energy source of vibration. However, in traditional Sadov’s empirical formula, the energy produced by explosive explosion is only considered which makes the error higher when it is used to predict the blasting-induced vibration peak under the condition of high in situ stress. In this study, energy transformation and distribution mechanisms caused by excavation of deep rock masses were analyzed at first. Then, a prediction model of vibration peak based on the principle of energy balance was established by dimension analysis. Finally, the proposed model was trained and tested with the vibration data monitored during the blasting excavation of deep buried tunnel in Jinping II hydropower station. The result shows that compared with the traditional prediction model, the proposed model has higher fitting correlation coefficient and lower root-mean-square error, which can be better applied to the prediction of vibration induced by blasting excavation of deep rock masses under high in situ stress.

scholarly journals Numerical Simulation of Blast Vibration and Crack Forming Effect of Rock-Anchored Beam Excavation in Deep Underground Caverns

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
XinPing Li ◽  
JunHong Huang ◽  
Yi Luo ◽  
Qian Dong ◽  
YouHua Li ◽  
...  
Keyword(s):  
Rock Mass ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Vibration Velocity ◽  
Blasting Vibration ◽  
Finite Element Software ◽  
Underground Cavern ◽  
Underground Caverns ◽  
Blasting Excavation

Aiming at surrounding rock damage induced by dynamic disturbance from blasting excavation of rock-anchored beam in rock mass at moderate or far distance in underground cavern, numerical model of different linear charging density and crustal stress in underground cavern is established by adopting dynamic finite element software based on borehole layout, charging, and rock parameter of the actual situation of a certain hydropower station. Through comparison in vibration velocity, contour surface of rock mass excavation, and the crushing extent of excavated rock mass between calculation result and field monitoring, optimum linear charging density of blast hole is determined. Studies are also conducted on rock mass vibration in moderate or far distance to blasting source, the damage of surrounding rock in near-field to blasting source, and crushing degree of excavated rock mass under various in situ stress conditions. Results indicate that, within certain range of in situ stress, the blasting vibration is independent of in situ stress, while when in situ stress is increasing above certain value, the blasting vibration velocity will be increasing and the damage of surrounding rock and the crushing degree of excavated rock mass will be decreasing.

scholarly journals Study on Energy Release of Surrounding Rock under the Multiple Unloading Disturbance during Tunnel Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yong Fan ◽  
Junwei Zheng ◽  
Xinyi Hu ◽  
Xianze Cui ◽  
Weiping He
Keyword(s):  
Energy Release ◽  
Strain Energy ◽  
Dynamic Change ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Adjustment Process ◽  
Rock Masses ◽  
Blasting Excavation ◽  
Storage Limit

During excavation of deep rock, the release of strain energy plays an important role in geologic hazards caused by excavation. However, in the previous studies, the influence of transient unloading of in situ stress caused by blasting excavation has been ignored, and the blasting excavation of a tunnel is regarded as a single blast process. In this paper, the dynamic adjustment process of strain energy and the energy storage limit of surrounding rocks caused by transient unloading of in situ stress under elastic conditions were firstly analyzed. Then, the brittle-ductile-plastic transition model based on the Hoek–Brown strength criterion was simulated in FLAC3D. Finally, the dynamic release process of strain energy of surrounding rocks caused by multiple unloading disturbances was analyzed during the excavation of 2# Underground Laboratory of Jinping II Hydropower Station employing the newly proposed index, energy release coefficient (ERC). Results show that the strain energy of surrounding rock masses firstly decreases, then increases, next reduces, and finally stabilizes under the transient unloading of in situ stress. In the process of dynamic change of strain energy, when the strain energy exceeds its storage limit, a large amount of strain energy will be released and thus will lead to damage of the surrounding rock masses. Because the cut holes and the first circle of breaking holes are far away from the final excavation boundary, the unloading disturbance to the strain energy of surrounding rock masses is small. Furthermore, the energy release of surrounding rock masses is mainly caused by the unloading of the last circle of breaking holes and perimeter holes, and the closer to the final excavation boundary, the more intense the energy release.

Analysis of Casing Strength after Casing Wear in Ultra-Deep Rock Salt Formation

2012 ◽  
Vol 616-618 ◽  
pp. 538-542 ◽  
Author(s):  
Fu Xiang Zhang ◽  
Wei Feng Ge ◽  
Xiang Tong Yang ◽  
Wei Zhang ◽  
Jian Xin Peng
Keyword(s):  
Rock Salt ◽  
Coupling Effect ◽  
Equivalent Stress ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Attrition Rate ◽  
Salt Formation ◽  
Salt Creep ◽  
Casing Wear

To alleviate the problems of casing collapse induced by the coupling effect of rock salt creep and casing wear, the effects of salt creep, attrition rate and casing abrasive position on the equivalent stress on casings in non-uniform in-situ stress field is analyzed by finite-difference model with worn casing, cement and salt formation. It indicates that, creep reduces the yield strength of worn casing to a certain extent; Equivalent stress on casings is bigger and more non-uniform when the abrasion is more serious; Wear position obviously changes the distribution of equivalent stress on casing, and when the wear located along the direction of the minimum in-situ stress, equivalent stress on casing could be the largest that leads to the casing being failed more easily. Equivalent stress on casings increases gradually with creep time increasing and will get to balance in one year or so; In addition, new conclusions are obtained which are different from before: the maximum equivalent stress on casings is in the direction of the minimum horizontal stress, only when the attrition rate of the casing is little; otherwise, it is not. This method could help to improve the wear prediction and design of casings.

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.

scholarly journals Exploring Deep-Rock Mechanics through Mechanical Analysis of Hard-Rock In Situ Coring System

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jianan Li ◽  
Heping Xie ◽  
Ling Chen ◽  
Cong Li ◽  
Zhiqiang He
Keyword(s):  
Rock Mechanics ◽  
Hard Rock ◽  
Design Method ◽  
Drill Pipe ◽  
In Situ Stress ◽  
Drilling Depth ◽  
Innovative Design ◽  
The Core ◽  
Deep Rock

Exploration of deep-rock mechanics has a significant influence on the techniques of mining and rock mechanics. Rock coring technique is the basic method for all rock mechanics study. With the increase of the drilling depth and increasing strength of the hard rock, how to obtain high-quality rock core through various coring techniques is an eternal work. Here an innovative method is applied to design the new coring system to maximize the efficiency of operation. The stress conditions or parameters of rock core in the coring are analyzed, and the mechanism of the core with in situ stress is shown in this paper. The conflict of the core and coring tool chamber is proposed for the innovative design. The innovative design method is fulfilled by the theory of inventive problem solving (TRIZ). An improved coring system for the full-length core with in situ stress was obtained with the solutions of improved coring mechanism, cutting mechanism, and spiral drill pipe.

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