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.

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.

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.

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.

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

scholarly journals Mechanical Mechanism of Hydraulic Fracturing Effect Caused by Water Inrush in Tunnel Excavation by Blasting

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Quan Zhang ◽  
Jiong Wang ◽  
Longfei Feng
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
In Situ Stress ◽  
Confined Water ◽  
Shear Damage ◽  
Splitting Factor ◽  
Blasting Excavation

When the deep tunnel is excavated, the pressure of the confined water is relatively high, causing the water inrush to have a hydraulic fracturing effect. The method of theoretical analysis was adopted to study this effect. A mechanical model for fracturing water inrush under blasting excavation conditions was established. The water inrush under this condition is the result of the combined action of static load (water pressure and in situ stress) and dynamic load (explosive stress wave). According to whether the normal stress on the hydraulic crack surface was tensile stress or compressive stress, two types of water inrush were proposed: water inrush caused by tensile-shear damage and water inrush caused by compression-shear damage. These two types of critical water pressures were calculated separately. The relationship between critical water pressure, in situ stress, and blasting disturbance load was given, and a pore water pressure splitting factor was introduced in the calculation process. The theoretically obtained critical water pressure had been verified in the case of water inrush in a deep-buried tunnel. The established theory can guide field practice well.

scholarly journals Study of the Rock Crack Propagation Induced by Blasting with a Decoupled Charge under High In Situ Stress

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Xudong Li ◽  
Kewei Liu ◽  
Jiacai Yang
Keyword(s):  
Crack Propagation ◽  
Radial Crack ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Crack Evolution ◽  
Deep Mining ◽  
Nonlinear Fracture ◽  
High In Situ Stress ◽  
Initiation And Propagation

The high in situ stress can significantly affect the blast-induced rock fragmentation and cause difficulties in deep mining and civil engineering where the drilling and blasting technique is applied. In this study, the rock crack propagation induced by blasting under in situ stress is first analyzed theoretically, and then a numerical model with a decoupled charge in LS-DYNA is developed to reveal how the initiation and propagation of rock cracks are under high in situ stress. Through simulation, the mechanisms of blast-induced crack evolution under various hydrostatic pressures and nonhydrostatic pressures are investigated, and the differences in crack evolution with specific decoupling coefficients are compared. According to the simulation, three damage zones, i.e., the crushed zone, the nonlinear fracture zone, and the radial crack propagation zone, are formed, and the radial crack evolution is greatly suppressed by the high in situ stress which has no much influence on the crack propagation in the crushed and the nonlinear fracture zones. The velocity of crack propagation is slightly reduced, and the process of crack propagation is stopped early when the rock is subjected to high in situ stress. Furthermore, the numerical analysis indicates that the crack grows preferentially in the direction of maximum principal stress, and the radial crack propagation is predominantly controlled by the preloaded pressure, which is vertical to the crack propagation direction. Based on the numerical results, it is suggested that the optimal decoupling coefficients for rock cracking are 2.65, 1.87, 1.37, and 1.22 for 0, 10, 20, and 30 MPa, respectively. This study provides not only an analysis of the rock crack evolution under high in situ stress but also a reference for resolving excavation difficulties in deep mining.

scholarly journals A Method for Making Transparent Hard Rock-Like Material and Its Application

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jinjin Ge ◽  
Ying Xu
Keyword(s):  
Model Experiment ◽  
Hard Rock ◽  
Cement Mortar ◽  
Physical And Mechanical Properties ◽  
Model Material ◽  
Rock Blasting ◽  
Similar Model ◽  
Similar Material ◽  
Deep Rock ◽  
Blasting Test

At present, a similar material most commonly used in the similarity model experiment of rock blasting is cement mortar. However, it is not transparent, which leads to the problem that the cracks in the model made of cement mortar after the test cannot be observed directly. Therefore, a kind of transparent hard rock-like material that can replace the existing model material to solve the above problem was developed in this study. This transparent hard rock-like material is made of a mixture of rosin saturated solution (RSS), epoxy resin (ER), and curing agent (CA), and its physical and mechanical properties are similar to those of hard rock through relevant tests. In addition, it is found through the blasting model test that the model specimen made of transparent hard rock-like materials has the characteristic of “direct observation” after blasting test, which conforms to the rock blasting fracture mechanism. Hence, it can replace the existing nontransparent model materials to be applied in rock blasting similar model experiment. The results from this study are helpful to the further experimental study of blasting crack propagation in deep rock mass.

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