scholarly journals Mechanical Anisotropy and Failure Characteristics of Columnar Jointed Rock Masses (CJRM) in Baihetan Hydropower Station: Structural Considerations Based on Digital Image Processing Technology

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3602 ◽  
Author(s):  
Yingjie Xia ◽  
Chuanqing Zhang ◽  
Hui Zhou ◽  
Chunsheng Zhang ◽  
Wangbing Hong
Keyword(s):  
Rock Mass ◽  
Crack Propagation ◽  
Structural Characteristics ◽  
Jointed Rock ◽  
Hydropower Station ◽  
Defect Structures ◽  
Failure Characteristics ◽  
Included Angle ◽  
Baihetan Hydropower Station ◽  
Columnar Joints

The columnar joints in Baihetan hydropower station are primary tensile joints since they were formed during the process of lava condensation. Understanding the influence of columnar jointed rock mass (CJRM) on the mechanical response and failure modes is the basis for designing of associated engineering works. Hence, the structural characteristics of Baihetan CJRM were analyzed by carrying out a geological survey at first. Three groups of numerical models capable of reflecting the structural characteristics of CJRM were then established to analyze the mechanical and failure characteristics. The results in this study showed that: (1) Irregularity of columnar basalt restricted crack propagation on columnar joints and also led to stress concentration in the distorted parts, and thus, damage of basalt columns; (2) when the included angle between direction of concentrated defect structures in CJRM and uniaxial stress was large, the defect structures can prevent crack propagation on columnar joints, and the failure of defect structure can cause the overall failure of the rock mass; and (3) under the condition of same columnar structure and included angle, the peak strength of models with microcracks and structural plane was low and the irregular shape of columnar joints decreased the anisotropy of mechanical parameters.

scholarly journals Rock Mass Classification for Columnar Jointed Basalt: A Case Study of Baihetan Hydropower Station

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shiyue Zhang ◽  
Mingjie He ◽  
Jinjian Gu ◽  
Zhihao Cui ◽  
Jian Wang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Classification Scheme ◽  
Jointed Rock ◽  
Rock Mass Classification ◽  
Classification Systems ◽  
Hydropower Station ◽  
Columnar Jointed Basalt ◽  
Baihetan Hydropower Station ◽  
Mass Classification

Rock mass classification is important in preliminary design of geotechnical engineering projects. Using the columnar jointed basalt at the foundation of Baihetan Hydropower Station as an example, this paper presents a classification scheme of the columnar jointed rock. Unlike many common rock masses, an obvious characteristic of columnar jointed rock is that it is discontinuous in geometry while continuous in mechanics. Due to the inapplicability of existing rock mass classification systems, a classification scheme, combined with rock mass integrity, weak plane tightness, and permeability, is proposed. The new classification system has five grades with quantitative factors, which takes into account the features of columnar joints. As an easy-to-use scheme and case study, it would be helpful as a reference in the rock mass classification of similar problems.

Failure Characteristics and Support Optimal Design of Columnar Jointed Rock Mass at a Diversion Tunnel

2013 ◽  
Vol 353-356 ◽  
pp. 1680-1684
Author(s):  
Xiang Dong Zhu ◽  
Lian Xing Hu ◽  
Jiang Quan ◽  
Shao Jun Li ◽  
Jun Li
Keyword(s):  
Rock Mass ◽  
Optimal Design ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Basaltic Lava ◽  
Diversion Tunnel ◽  
Failure Characteristics ◽  
Support Measures ◽  
Columnar Jointed Rock Mass ◽  
Columnar Joints

Columnar joints are native rupture structures which are ordered columnar forms in basaltic lava. The cracks and joints inside them are well-developed which lead to the weak self-supporting ability after excavation. At present, loose and collapse of columnar rock mass are the main problem in the hydraulic diversion tunnel. Based on field observation and test, this paper studied the failure characteristics of columnar joints in the diversion tunnel and simulated the failure mechanism. Based on this discussion, optimized support measures have been taken to ensure the safe construction of the diversion tunnel.

A New Method to Determining the Strength Parameters of Fractured Rock Mass

2014 ◽  
Vol 898 ◽  
pp. 378-382
Author(s):  
Yun Hua Guo ◽  
Wei Shen Zhu
Keyword(s):  
Rock Mass ◽  
Mechanical Response ◽  
Fractured Rock ◽  
Fracture Network ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Constitutive Relationship ◽  
Hydropower Station ◽  
Rock Masses ◽  
Fractured Rock Mass

A Hydropower Station is located in the middle reach of the Dadu River in southwest China. The natural slope angles are generally 40°~65° and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. Many abutment slopes were formed during construction of the abutments. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the hydropower station. According to the statistical distribution of joints and fractures at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model which is close to the real state of the fractured rock mass are established by the Monte-Carlo method. The mechanical response of fractured rock masses with different sizes of numerical models is studied using FLAC3D. The REV characteristic scale is identified for rock masses in the slopes with stochastic fracture network. Numerical simulation is performed to obtain the stress-strain curve, the mechanical parameters and the strength of the jointed rock mass in the zone. A constitutive relationship reflecting the mechanical response of the jointed rock mass in the zone is established. The Comparison between the traditional method and the method in this paper has been made at the end.

scholarly journals Seepage Flow Properties of a Columnar Jointed Rock Mass in a True Triaxial Experiment

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Yanxin He ◽  
Zhende Zhu ◽  
Wenbin Lu ◽  
Yunjin Hu ◽  
Xinghua Xie ◽  
...  
Keyword(s):  
Rock Mass ◽  
Principal Stress ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Intermediate Principal Stress ◽  
True Triaxial ◽  
Minimum Principal Stress ◽  
Baihetan Hydropower Station ◽  
Columnar Jointed Rock Mass ◽  
Seepage Characteristics

A columnar jointed rock mass is a type of rock mass with strong geometric anisotropy and high interface permeability. Its seepage characteristics pose new challenges to the construction and maintenance of the Baihetan Hydropower Station on the Jinsha River. The research object in this study is the columnar jointed rock mass (basalt) in the dam area of Baihetan Hydropower Station. Similar-material model samples of the columnar jointed rock mass with different column dip angles ( α = 0 ° ~90°) were prepared following a similar principle. A true triaxial seepage–stress coupling test was conducted to evaluate the seepage characteristics of similar-material samples with different dip angles under intermediate principal stress and minimum principal stress. The experimental results showed that the columnar jointed rock mass exhibited apparent seepage anisotropy. The relationship curve between the volume flow rate Q and the pressure gradient − d P / d L of the samples with different dip angles showed evident nonlinear seepage under intermediate principal stress, which could be well expressed using the Forchheimer equation. It shows the characteristics of a typical linear Darcy flow under minimum principal stress. The law of variations in the permeability of the samples with different dip angles under intermediate principal stress can be well expressed using the one-dimensional quadratic function equation k = a + b σ 2 + c σ 2 2 , and the law of variations in the permeability of the samples with different dip angles under minimum principal stress can be well expressed using the logarithmic function k = a + b ln σ 3 . The permeabilities of the columnar jointed rock mass with dip angles of 0°, 15°, 30°, and 60° were most sensitive to changes in stress, and the seepage characteristics increased in complexity after changes in stress.

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