In situ seepage testing method for fractured zones of rock mass

2020 ◽  
Vol 54 (1) ◽  
pp. qjegh2020-050
Author(s):  
Sihong Liu ◽  
Siyuan Xu ◽  
Bin Zhou
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Hydropower Station ◽  
Permeability Characteristics ◽  
Critical Hydraulic Gradient ◽  
Testing Method ◽  
Natural Stress ◽  
Stress States

The permeability characteristics of rock mass discontinuities are important in the stability of hydropower station projects. We propose a large-scale in situ seepage testing method and use this method to test gently dipping bedding faults (C3 zone) and steep faults (F14) in a hydropower station construction field in China. The in situ test results are compared with those of both undisturbed and reconstituted specimens. The comparison indicates that the largest critical hydraulic gradient and the smallest seepage permeability coefficient are obtained via in situ tests because they are performed under stress states that simulate the natural stress of the surrounding rock mass. The natural stress of the surrounding rock mass cannot be reflected in tests of undisturbed and reconstituted specimens.

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.

Analysis on Factors Influencing Deformation of the Underground Cavities during the Construction Period

2012 ◽  
Vol 446-449 ◽  
pp. 2722-2726
Author(s):  
Chun Yu Gao ◽  
Jian Hui Deng ◽  
Fan Li Meng
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Hydropower Station ◽  
Construction Period ◽  
Underground Caverns ◽  
Underground Cavities ◽  
Rock Mass Deformation ◽  
Mass Deformation

The underground cavities of the Guandi Hydropower Station are Complex large-scale underground caverns. The quality of the surrounding rock masses of the underground cavities of the Guandi Hydropower Station is good and the deformation is normally less than 30mm. The structure surfaces have noticeable action for controlling the surrounding rock mass deformation. The time characteristic of the surrounding rock mass deformation is not noticeable.

In Situ Tests on Creep Behavior of Rock Mass with Joint or Shearing Zone in Foundation of Large-Scale Hydroelectric Projects

2004 ◽  
Vol 261-263 ◽  
pp. 1097-1102 ◽  
Author(s):  
Jian Liu ◽  
Xia Ting Feng ◽  
Xiu Li Ding ◽  
Huo Ming Zhou
Keyword(s):  
Rock Mass ◽  
Creep Behavior ◽  
Large Scale ◽  
Time Dependent ◽  
Three Gorges Project ◽  
Three Gorges ◽  
The Three Gorges ◽  
The Three Gorges Project

The time-dependent behavior of rock mass, which is generally governed by joints and shearing zones, is of great significance for engineering design and prediction of long-term deformation and stability. In situ creep test is a more effective method than laboratory test in characterizing the creep behavior of rock mass with joint or shearing zone due to the complexity of field conditions. A series of in situ creep tests on granite with joint at the shiplock area of the Three-Gorges Project and basalt with shearing zone at the right abutment of the Xiluodu Project were performed in this study. Based on the test results, the stress-displacement-time responses of the joints and basalt are analyzed, and their time-dependent constitutive model and model coefficients are given, which is crucial for the design to prevent the creep deformations of rock masses from causing the failure of the operation of the shiplock gate at the Three-Gorges Project and long-term stability of the Xiluodu arc dam.

scholarly journals Key Factors Affecting the Deformation and Failure of Surrounding Rock Masses in Large-Scale Underground Powerhouses

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Meng Wang ◽  
Jia-wen Zhou ◽  
An-chi Shi ◽  
Jin-qi Han ◽  
Hai-bo Li
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Surrounding Rock ◽  
Rock Masses ◽  
Affecting Factors ◽  
Key Factors ◽  
Underground Powerhouse ◽  
Deformation And Failure ◽  
Factors Affecting ◽  
Geological Conditions

The stability of the surrounding rock masses of underground powerhouses is always emphasized during the construction period. With the general trends toward large-scale, complex geological conditions and the rapid construction progress of underground powerhouses, deformation and failure issues of the surrounding rock mass can emerge, putting the safety of construction and operation in jeopardy and causing enormous economic loss. To solve these problems, an understanding of the origins and key affecting factors is required. Based on domestic large-scale underground powerhouse cases in the past two decades, key factors affecting the deformation and failure of the surrounding rock mass are summarized in this paper. Among these factors, the two most fundamental factors are the rock mass properties and in situ stress, which impart tremendous impacts on surrounding rock mass stability in a number of cases. Excavation is a prerequisite of surrounding rock mass failure and support that is classified as part of the construction process and plays a pivotal role in preventing and arresting deformation and failure. Additionally, the layout and structure of the powerhouse are consequential. The interrelation and interaction of these factors are discussed at the end of this paper. The results can hopefully advance the understanding of the deformation and failure of surrounding rock masses and provide a reference for design and construction with respect to hydroelectric underground powerhouses.

scholarly journals In-situ rock tests for fault gouge zone：A case in Fengman hydropower station, China

2021 ◽  
Vol 293 ◽  
pp. 03008
Author(s):  
Xinchuan Xu ◽  
Zhaoyue Yu ◽  
Fangfang Xue ◽  
Xiaogang Long ◽  
Xinyu Mao ◽  
...  
Keyword(s):  
Large Scale ◽  
Scientific Basis ◽  
Test Point ◽  
Actual Condition ◽  
Hydropower Station ◽  
Bearing Plate ◽  
Dam Site ◽  
Fault Gouges ◽  
The Stability

The existence of faults in the dam site area threatens the stability and safety of large-scale hydropower projects in China. The fault argillaceous zone is the worst kind of fault fracture zone, and the determination of its deformation and strength parameters is the key point of rock engineering investigation. In this study, the in-situ bearing plate test and direct shear test were carried out on the gouge zone of F67 fault in the dam site of Fengman Hydropower Station. The test results show that the deformation and shear law of each test point is good, which is basically consistent with the actual condition of the measured rock mass. However, due to the limited number of measurements, the results are limited in terms of macroscopic representation. The experimental results provide scientific basis for subsequent engineering design and further enhance the understanding of mechanical properties of fault gouges.

scholarly journals Comparative Study of the Excavation Damage and Rockburst of the Deeply Buried Jinping II Diversion Tunnels Using a TBM and the Drilling-Blasting Method

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jing Yang ◽  
Xing-Guo Yang ◽  
Jia-Wen Zhou ◽  
Yong Liu ◽  
Bao-Shun Dong ◽  
...  
Keyword(s):  
Rock Mass ◽  
Stress Concentration ◽  
High Stress ◽  
Tunnel Boring Machine ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
High In Situ Stress ◽  
Damaged Zone ◽  
Blasting Method

The rock mass failure induced by high in-situ stresses during the excavation of deep diversion tunnels is one of the key problems in the construction of the Jinping II Hydropower Station. Based on the results of acoustic wave tests and rockburst statistical analysis conducted, this study focuses on the excavation damaged zone (EDZ) and rockburst events in the Jinping II diversion tunnels excavated using the tunnel boring machine (TBM) method and the drilling-blasting method. The unloading failure mechanism and the rockburst induced by the two different excavation methods were compared and analyzed. The results indicate that, due to the different stress adjustment processes, the degree of damage to the surrounding rock mass excavated using the drilling-blasting method was more serious than that using the TBM method. The EDZ induced by the TBM was usually distributed evenly along the edge of the excavation surface. While, the drilling-blasting method was more likely to cause stress concentration, resulting in a deeper EDZ in local areas. However, the TBM excavation method can cause other problems in high in-situ stress areas, such as strong rockbursts. The drilling-blasting method is more prone to structural controlled failure of the surrounding rock mass, while the TBM method would induce high stress concentration near the edge of excavation and more widely distributed of stress adjustment induced failure. As a result, the scale and frequency of the rockburst events generated by the TBM were significantly greater than those caused by the drilling-blasting method during the excavation of Jinping II diversion tunnels. The TBM method should be used carefully for tunnel excavation in high in-situ stress areas with burial depths of greater than 2000 m. If it is necessary to use the TBM method after a comprehensive selection, it is suggested that equipment adaptability improvement, advanced prediction, and prediction technology be used.

Geo-Stress Direction Evaluation Method Based on Numerical Simulation

2014 ◽  
Vol 580-583 ◽  
pp. 2011-2014
Author(s):  
Su Chao Xu ◽  
C Y. Jin
Keyword(s):  
Numerical Simulation ◽  
Evaluation Method ◽  
Maximum Shear Stress ◽  
Local Stress ◽  
Surrounding Rock ◽  
Hydropower Station ◽  
Local Stress Concentration ◽  
Stress Direction ◽  
Baihetan Hydropower Station

The phenomenon of spalling at Baihetan Hydropower Station is influenced by such factors as the stress redistribution in surrounding rock, the local stress concentration and also poor properties of disturbed belt. In this paper, a series of numerical simulation were carried out and some beneficial conclusions were gained as follows: 1) the ratio of maximum shear stress and uniaxial compressive strength is more rational in the prediction of spalling and can give confident explanation for “V” shape pits; 2) the in-situ geo-stress direction is in accordance with NNE and NE.

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