scholarly journals Study on the Damage Process and Numerical Simulation of Tunnel Excavation in Water-Rich Soft Rock

2021 ◽  
Vol 11 (19) ◽  
pp. 8906
Author(s):  
Wenqi Ding ◽  
Shi Tan ◽  
Rongqing Zhu ◽  
He Jiang ◽  
Qingzhao Zhang
Keyword(s):  
Progressive Failure ◽  
Water Immersion ◽  
Failure Process ◽  
Soft Rock ◽  
Simulation Method ◽  
Surrounding Rock ◽  
Constitutive Relationship ◽  
Water Softening ◽  
Deformation And Failure ◽  
Tensile Damage

The weakening effect is one of the most important causes triggering large deformation and failure of soft-rock engineering; however, few studies paid attention to damage evolution and constitutive relationship of rock in tensile damage in the excavation unloading and water-weakening process, not to mention the coupling process of unloading and water-weakening. In this paper, the mechanism and engineering characteristics of unloading softening and water-softening of water-rich soft rock are analyzed and summarized. Then with the aid of the strain equivalent principle, the damage of surrounding rock caused by unloading softening and water-softening is coupled, and the compression shear damage and the tensile damage of surrounding rock under the unloading process are analyzed. A damage constitutive model of rock subjected to excavation unloading and water-weakening is proposed considering the influence of water immersion time, and the proposed model is applied in a newly established finite element simulation method, which is suitable for excavation in the water-rich soft rock. Based on the mechanical-hydraulic-damage coupled method, the progressive failure process of surrounding rock under the dual softening effects can be reflected by the deteriorated parameters of damage elements. Finally, the field monitoring data of a typical section in the Xujiadi tunnel is used to verify the applicability and accuracy of the proposed dual softening model and simulation method.

scholarly journals Research on the Law of Large-Scale Deformation and Failure of Soft Rock Based on Microseismic Monitoring

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Feng Chen ◽  
Tianhui Ma ◽  
Chun’an Tang ◽  
Yanhong Du ◽  
Zhichao Li ◽  
...  
Keyword(s):  
Monitoring System ◽  
Large Scale ◽  
Failure Process ◽  
Soft Rock ◽  
Microseismic Monitoring ◽  
Surrounding Rock ◽  
Deformation And Failure ◽  
Microseismic Events ◽  
Rock Tunnel ◽  
Microseismic Event

Based on the existing Canadian ESG microseismic monitoring system, a mobile microseismic monitoring system for a soft rock tunnel has been successfully constructed through continuous exploration and improvement to study the large-scale nucleation and development of microfractures in the soft rock of the Yangshan Tunnel. All-weather, continuous real-time monitoring is conducted while the tunnel is excavated through drilling and blasting, and the waveform characteristics of microseismic events are analysed. Through the recorded microseismic monitoring data, the variation characteristics of various parameters (e.g., the temporal, spatial, and magnitude distributions of the microseismic events, the frequency of microseismic events, and the microseismic event density and energy) are separately studied during the process of large-scale deformation instability and failure of the soft rock tunnel. The relationship between the deterioration of the rock mass and the microseismic activity during this failure process is consequently discussed. The research results show that a microseismic monitoring system can be used to detect precursors; namely, the microseismic event frequency and energy both will appear “lull” and “active” periods during the whole failure process of soft rock tunnel. Two peaks are observed during the evolution of failure. When the second peak occurs, it is accompanied by the destruction of the surrounding rock. The extent and strength of the damage within the surrounding rock can be delineated by the spatial, temporal, and magnitude distributions of the microseismic events and a microseismic event density nephogram. The results of microseismic analysis confirm that a microseismic monitoring system can be used to monitor the large-scale deformation and failure processes of a soft rock tunnel and provide early warning for on-site construction workers to ensure the smooth development of the project.

scholarly journals Research on Supporting Method for High Stressed Soft Rock Roadway in Gentle Dipping Strata of Red Shale

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 423
Author(s):  
Chunde Ma ◽  
Jiaqing Xu ◽  
Guanshuang Tan ◽  
Weibin Xie ◽  
Zhihai Lv
Keyword(s):  
Failure Process ◽  
High Stress ◽  
Soft Rock ◽  
In Situ Stress ◽  
Mechanical Parameters ◽  
Deformation And Failure ◽  
Deep Mine ◽  
Plastic Energy ◽  
Roadway Stability ◽  
Phosphate Mine

Red shale is widely distributed among the deep mine areas of Kaiyang Phosphate Mine, which is the biggest underground phosphate mine of China. Because of the effect of various factors, such as high stress, ground water and so on, trackless transport roadways in deep mine areas were difficult to effectively support for a long time by using traditional supporting design methods. To deal with this problem, some innovative works were carried out in this paper. First, mineral composition and microstructure, anisotropic, hydraulic mechanical properties and other mechanical parameters of red shale were tested in a laboratory to reveal its deformation and failure characteristics from the aspect of lithology. Then, some numerical simulation about the failure process of the roadways in layered red shale strata was implemented to investigate the change regulation of stress and strain in the surrounding rock, according to the real rock mechanical parameters and in-situ stress data. Therefore, based on the composite failure law and existing support problems of red shale roadways, some effective methods and techniques were adopted, especially a kind of new wave-type bolt that was used to relieve rock expansion and plastic energy to prevent concentration of stress and excess deformation. The field experiment shows the superiorities in new techniques have been verified and successfully applied to safeguard roadway stability.

Numerical Analysis of Faults on Deep-Buried Tunnel Surrounding Rock Damaged Zones

2011 ◽  
Vol 90-93 ◽  
pp. 74-78 ◽  
Author(s):  
Jun Hu ◽  
Ling Xu ◽  
Nu Wen Xu
Keyword(s):  
Numerical Analysis ◽  
Mechanical Response ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Factors Affecting ◽  
Rock Failure Process ◽  
Tunnel Instability

Fault is one of the most important factors affecting tunnel instability. As a significant and casual construction of Jinping II hydropower station, when the drain tunnel is excavated at depth of 1600 m, rockbursts and water inrush induced by several huge faults and zone of fracture have restricted the development of the whole construction. In this paper, a progressive failure progress numerical analysis code-RFPA (abbreviated from Rock Failure Process Analysis) is applied to investigate the influence of faults on tunnel instability and damaged zones. Numerical simulation is performed to analyze the stress distribution and wreck regions of the tunnel, and the results are consistent with the phenomena obtained from field observation. Moreover, the effects of fault characteristics and positions on the construction mechanical response are studied in details. Some distribution rules of surrounding rock stress of deep-buried tunnel are summarized to provide the reasonable references to TBM excavation and post-support of the drain tunnel, as well as the design and construction of similar engineering in future.

The Bench Method Numerical Simulation of Soft Rock Tunnel

2013 ◽  
Vol 438-439 ◽  
pp. 949-953
Author(s):  
Hao Bo Fan ◽  
Jin Xing Lai ◽  
Dan Dan Hou
Keyword(s):  
Numerical Simulation ◽  
Measurement Data ◽  
Soft Rock ◽  
Simulation Method ◽  
Internal Force ◽  
Surrounding Rock ◽  
Supporting Structure ◽  
Highway Tunnel ◽  
Tunnel Design ◽  
Rock Tunnel

This paper based on Chaoyang tunnel by bench method excavation, using the finite element numerical simulation method, simulates the surrounding rock displacement of soft rock tunnel and the stress characteristics of supporting structure to get the various stages of tunnel surrounding rock stress, strain and the internal force changes of tunnel supporting structure. After the analyses of the numerical simulation results and field monitoring measurement data, the safety and rationality of the method are determined. The research provides certain reference for highway tunnel design and construction.

Model Test Study on Failure Mechanism of Unsupported Tunnels Constructed in Soft Rock Masses at Different Cross Section

2011 ◽  
Vol 90-93 ◽  
pp. 2282-2285
Author(s):  
Cheng Bing Wang ◽  
He Hua Zhu ◽  
Hua Lao Wang
Keyword(s):  
Cross Section ◽  
Failure Process ◽  
Ground Surface ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Test Study ◽  
Gravitational Stress ◽  
Section Type ◽  
Failure Conditions ◽  
Full Face

The failure conditions of tunnel surrounding rock under different cross section after full face excavation were studied through a number of model tests. The simulation of unsupported tunnel failure process under gravitational stress is carried out successfully in the tests. The test results show that failure of surrounding rock initiates from the upper part of the tunnel and develops upward progressively. Failure form of tunnel is different under different cross section type. Comparing with two-lane tunnel, the surrounding rock of three-lane tunnel keeps shorter stabilization, failure develops to the ground surface more rapidly, the stress changing amplitude of those beside tunnel is larger, and the rock mass on the top of the tunnel slides downward more clearly.

Simulation Analysis of the Soft Rock Inclined Shaft Surrounding Rock Control with Different Bolt Support Patterns

2014 ◽  
Vol 988 ◽  
pp. 377-382 ◽  
Author(s):  
Peng Fei Jiang
Keyword(s):  
Compressive Stress ◽  
Simulation Analysis ◽  
Soft Rock ◽  
High Strength ◽  
Surrounding Rock ◽  
Tension Stress ◽  
Deformation And Failure ◽  
Stress And Deformation ◽  
Rock Strata ◽  
Bolt Support

Taking +150 inclined shaft going through the soft rock strata at Muchengjian mine as the background, and based on the analysis of the deformation and failure feature of the roadway surrounding rock in the soft rock strata, this paper makes X-Ray Differaction (XRD) phase analysis of the soft rock; using finite difference numerical software FLAC3D, it stimulates and makes comparative analysis of the stress and deformation distribution characteristics of the roadway surrounding rock with bolt support with different intervals, and the support of the high-strength bolt with high pre-tension stress in the inclined shaft through the soft rock strata. The results show that the roadway surrounding rock in the +150 inclined shaft at Muchengjian mine is swelling soft rock prone to softening, degradation and swelling in water, which is bad for the roadway support; different types of rock strata have significant different impact on the stress and deformation of the roadway surrounding rock; for the soft rock roadway, the increased pre-tension stress of the bolt can cause higher compressive stress in the roadway surrounding rock and reduce the tension failure of the surrounding rock;compared with the end anchorage, the full-size anchorage with high pre-tension stress can cause the overlap of the conical compressive stress zone and enhance the roadway overall support.

scholarly journals Instability Mechanism and Key Control Technology of Deep Soft Rock Roadway under Long-Term Water Immersion

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wei Jing ◽  
Xu Wang ◽  
Pengwei Hao ◽  
Laiwang Jing ◽  
Weipei Xue
Keyword(s):  
Water Immersion ◽  
Soft Rock ◽  
Surrounding Rock ◽  
The Self ◽  
Instability Mechanism ◽  
Roadway Support ◽  
Soft Rock Roadway ◽  
Bearing Structure ◽  
Rock Roadway

More and more attention has been paid to the supporting problem of deep soft rock roadway floor with long-term water immersion in recent years. However, the existing soft rock roadway support technology rarely takes into account the influence of the immersion softening phenomenon of the roadway floor and the self-supporting structure characteristics of the surrounding rock on the stability of the surrounding rock at the same time, and the influence of the creep characteristics of rock on the deformation zone of the surrounding rock requires further research on the nature and division of the self-supporting structure of the surrounding rock. In response to the issues mentioned, based on the loading and unloading properties of the surrounding rock of the soft rock roadway, a new concept of the internal and external self-bearing structure was proposed. The fact of water-immersed mudstone softening in the soft rock roadway floor was revealed through the field practice, and the shape of the internal and external bearing structure was determined based on the in situ monitoring results. Then, the instability mechanism of the internal and external self-bearing structure of the surrounding rock was analyzed, the position of the critical control point was calculated, and the key control technology based on the method of controlling floor heave by using double-row anchor cables to control the deformation of the roadway sides was put forward. Finally, the field industrial test showed that this support technology can effectively control the deformation and failure of soft rock roadway in the case of water immersion on the floor. This work can provide a technical reference for similar roadway support designs.

Investigation on Deformation and Failure Characteristics and Stability Control of Soft Rock Roadway Surrounding Rock in Deep Coal Mine

2011 ◽  
Vol 255-260 ◽  
pp. 3711-3716 ◽  
Author(s):  
Ju Cai Chang ◽  
Guang Xiang Xie
Keyword(s):  
Coal Mine ◽  
Plastic Region ◽  
Soft Rock ◽  
Stability Control ◽  
Surrounding Rock ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Deep Coal Mine ◽  
Soft Rock Roadway ◽  
Rock Roadway

Numerical simulation and field measurement were carried out to investigate into laws of deformation and movement and the evolving characteristics of the plastic region around the roadway based on engineering conditions of deep soft rock roadway in Wangfenggang colliery, Huainan Mining area. The mechanism of controlling the surrounding rock stability of soft rock roadway in deep coal mine was demonstrated. The supporting of soft rock roadway in deep coal mine must be compatible with deformation and failure characteristics of surrounding rock, and it can keep the stability of surrounding rock. The combined supporting with high strength and prestress bolting-anchoring and integral surrounding rock grouting reinforcement can effectively control the surrounding rock deformation of soft rock roadway in deep coal mine. But every working step must be pay attention to sequence on the time and space so that it can play an integral supporting effect. Research results are put into practice accordingly and good control effect has been achieved.

scholarly journals Physical and Mechanical Characteristics of Soft Rock Tunnel and the Effect of Excavation on Supporting Structure

2019 ◽  
Vol 9 (8) ◽  
pp. 1517 ◽  
Author(s):  
Yimo Zhu ◽  
Liang Chen ◽  
Heng Zhang ◽  
Zelin Zhou ◽  
Shougen Chen
Keyword(s):  
Large Deformation ◽  
Rational Design ◽  
Rock Sample ◽  
Water Immersion ◽  
Soft Rock ◽  
Mechanical Tests ◽  
Surrounding Rock ◽  
Economic Losses ◽  
Free Expansion ◽  
Weak Support

The problem of large deformation is very prominent in deep-buried tunnel excavation in soft rock, which brings serious potential safety hazards and economic losses to projects. The knowledge of deformation law and support measures is the key to ensure the rational design and safe construction in a large deformation tunnel of soft rock. This paper describes rock physical and mechanical tests and field monitoring is employed to investigate the cause and development process of large deformation in Dongsong hydropower station in Sichuan Province, China. The results show that the free expansion rate of the rock sample is 20.0%, the average expansion stress of the rock sample is 11.0 kPa, and the expansibility of the rock is low. Large deformation of surrounding rock mainly comes from the dilatancy effect with high geostress and relaxation deformation with weak support. Shotcrete sealing exposed surrounding rock, and early strength support avoiding water immersion are useful to deal with the three main factors (weathering, water and confining pressure) that affect the strength of surrounding rocks. The second lining applied in time can effectively limit the further development of stress and deformation of initial support, and prevent the cracking and large deformation of concrete. Clearance convergence is suggested to be the main monitoring work in construction, because of its advantages of intuitive results, easy quality assurance of instrument installation and high accuracy.

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