Probabilistic stability assessment of tunnel-support system considering spatial variability in weak rock mass

AbstractWater tunnels built for hydropower passing through weak and heterogeneous rock mass pose challenges associated to slaking and disintegration, as they are first exposed to dry condition during excavation and are then filled with water to produce hydropower energy. Over the period of operational life, these tunnels are drained periodically for inspections and repair leading to drainage and filling cycles. The weakening of rock mass caused by cycles of drying, saturation and drainage may lead to the propagation of instabilities in the tunnels. Therefore, it is important to study the slaking and disintegration behavior of the weak rock mass consisting of clay and clay-like minerals. This paper assesses the mineralogical composition of flysch and serpentinite from the headrace tunnel of Moglicë Hydropower Project in Albania. Further, to determine the slaking and disintegration behavior of these rocks, extensive testing using both the ISRM, Int J Rock Mech Min Sci Geomech Abstr 16(2):143-151, (1979) suggested test method and a modified variant of this test are performed. Finally, comprehensive assessments, discussions and comparisons are made. It is found that the modified slake durability test better suits for the tunnels built as water conveying systems such as hydropower tunnels.

Download Full-text

Early Stage Tunnel Lining Experimental Study of Jinhuashan Railway Tunnel Construction within Soft and Weak Rock Mass

Geological Engineering: Proceedings of the 1 ◽

10.1115/1.802922.paper153 ◽

2010 ◽

pp. 1-8

Author(s):

Hua Yuan ◽

Zhou Taiquan ◽

Lv Baohua

Keyword(s):

Experimental Study ◽

Rock Mass ◽

Early Stage ◽

Tunnel Lining ◽

Tunnel Construction ◽

Weak Rock ◽

Railway Tunnel ◽

Weak Rock Mass

Download Full-text

Automatic Drilling Process Monitoring (DPM) for in-situ characterization of weak rock mass strength with depth

Rock Mechanics: Meeting Society's Challenges and Demands ◽

10.1201/noe0415444019-c25 ◽

2007 ◽

pp. 199-206 ◽

Cited By ~ 1

Author(s):

Z Yue ◽

J Chen ◽

W Gao

Keyword(s):

Rock Mass ◽

Process Monitoring ◽

Weak Rock ◽

Drilling Process ◽

In Situ Characterization ◽

Rock Mass Strength ◽

Weak Rock Mass

Download Full-text

Analysis of Support Design in Weak Rock Drift Using a Systematic Approach

Advances in Civil Engineering ◽

10.1155/2020/8874081 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Xingdong Zhao ◽

Shujing Zhang ◽

Huaibin Li ◽

Guoju Chen ◽

Pengqiang Zhang

Keyword(s):

Rock Mass ◽

Plastic Zone ◽

Rock Mechanics ◽

Support System ◽

Systematic Approach ◽

Wire Mesh ◽

Weak Rock ◽

Support Design ◽

Cable Bolt ◽

Q System

The aim of this study is to develop a systematic approach for support design of weak rock drift based on empirical, analytical, and numerical method, which is employed to estimate weak rock support demand and design support system. Detailed engineering geological investigations and rock mechanics test have been carried out in weak rock drift. The Q-system and GSI-system were used to determine the primary support design and rock mass properties, respectively. The numerical model of RS2 finite element program has been calibrated by analyzing the relation of falling height observed in the field to the frictional angles obtained from empirical method, rock mechanics test, and calculated rock mass parameters, respectively. In an attempt to check the validity of sophisticated support, support suggested by Q-system, and the combination support system proposed by analytical approach, the RS2 program was employed to analyze the depth of plastic zone and total displacement surrounding the weak rock drift. Numerical results show that the depths of plastic zone and total deformation surrounding the weak rock drift supported by the combination support system significantly descended 87% and 90% of those of sophisticated support. In particular, the rock bolt and cable bolt provide enough frictional and interlocked forces to resist weak rock falling which change the weak rock mechanicals properties and the surface holding function reinforced by the shotcrete, wire mesh, and steel strap. The factor of safety (FOS) of 8.28 of the combination support system is much more than the FOS of 1.5 for permanent drift. The combination support system with rock bolts, cable bolt, shotcrete, wire mesh, and steel straps has been applied to stabilize the weak rock drift and found to be successful to prevent further deformations surrounding the drift.

Download Full-text

Study on Center Hole Deformation Test of Rigid Bearing Plate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.33-37.1187 ◽

2008 ◽

Vol 33-37 ◽

pp. 1187-1194

Author(s):

Jian Guo Zhang ◽

Qiang Yong Zhang ◽

Wen Dong Yang ◽

Ying Zhang

Keyword(s):

Rock Mass ◽

Deformation Modulus ◽

Hydropower Station ◽

Weak Rock ◽

Bearing Plate ◽

Deep Rock ◽

Weak Rock Mass ◽

Deformation Test ◽

Test Points ◽

Dagangshan Hydropower Station

The center hole deformation test of rigid bearing plate is an important method for understanding deformation properties of deep weak rock mass. According to the center hole deformation test of rigid bearing plate in dam zone of Dagangshan hydropower station, this paper detailedly recommends test method of this experiment, and the settlement deformation formula of deep rock mass under circular rigid bearing plate is deduced, which could be used to calculate deformation modulus and equivalence deformation modulus of different deep rock mass at test points. According to curves of depth-deformation under different pressures at test points in dam zone, we have analyzed deformation characteristics of deep weak rock mass. By the center hole deformation test of rigid bearing plate, stratum properties in dam zone of Dagangshan hydropower station could be understood further, and it provides important references for the study of creep speciality of weak rock mass in dam zone.

Download Full-text