Deformation Behaviors and Control Measures of Tunnels in Jointed and Altered Granite Rock Mass with High In Situ Stress: A Case Study

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.

Download Full-text

Coring damage extent of rock cores retrieved from high in-situ stress condition: A case study

KSCE Journal of Civil Engineering ◽

10.1007/s12205-017-1660-0 ◽

2017 ◽

Vol 21 (7) ◽

pp. 2946-2957 ◽

Cited By ~ 3

Author(s):

Peng Yan ◽

Qi He ◽

Wenbo Lu ◽

Yanli He ◽

Wei Zhou ◽

...

Keyword(s):

Stress Condition ◽

In Situ Stress ◽

High In Situ Stress ◽

Rock Cores ◽

Damage Extent

Download Full-text

A displacement-based back-analysis method for rock mass modulus and horizontal in situ stress in tunneling – Illustrated with a case study

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2005.12.001 ◽

2006 ◽

Vol 21 (6) ◽

pp. 636-649 ◽

Cited By ~ 55

Author(s):

L.Q. Zhang ◽

Z.Q. Yue ◽

Z.F. Yang ◽

J.X. Qi ◽

F.C. Liu

Keyword(s):

Rock Mass ◽

Back Analysis ◽

In Situ Stress ◽

Analysis Method ◽

Rock Mass Modulus ◽

Displacement Based

Download Full-text

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

Advances in Civil Engineering ◽

10.1155/2020/8876214 ◽

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.

Download Full-text

Effects Of Different Empirical Design Approaches For Size Galleries On The Behaviour Of Rock Masses During The Excavation Operation: Excavation Case At BAE Well

Turkish Journal of Computer and Mathematics Education (TURCOMAT) ◽

10.17762/turcomat.v12i5.1781 ◽

2021 ◽

Vol 12 (5) ◽

pp. 1167-1177

Author(s):

Ismail Zaki, Et. al.

Keyword(s):

Rock Mass ◽

Support Systems ◽

Resistance Index ◽

In Situ Stress ◽

Tunnel Excavation ◽

High In Situ Stress ◽

Rock Mass Quality ◽

Empirical Approaches ◽

Empirical Design

The characterization of rock massifs is a delicate job; indeed, it is possible to understand the behaviour of intact rocks individually by laboratory tests but it is difficult to characterize them on the whole rock mass, which has undergone a complex geological history. Empirical approaches play an important role in the excavation of galleries and the design of support systems. These approaches are considered very effective in optimizing the tunnel excavation process. Several reliable empirical approaches have been developed, but the selection or use of an appropriate empirical method to design the tunnel excavation remains a difficult task. Therefore, in this work, the analysis of four approaches, the most used, of different empirical design was carried out to determine the behaviour of the rock mass during its excavation in a state of high in situ stress. This study was carried out on the scale of the ST2 rock mass of the worksite (BAE well 3) at the Bouazzer mine. These approaches include the AFTES classification, rock mass index (RMR), rock mass quality (Q) and geological resistance index (GSI). Based on the simulated statistical results obtained from said empirical approaches, through the finite element calculation, it was found that the application of the rock mass quality approach is very efficient in the excavation of the rock mass. gallery of size because it makes it possible to take into account the equivalent dimensions of the gallery, the stress condition in situ due to the excavation and the heights of overburden which are considered as major elements of the stability of the gallery. The method provides an optimized reinforcement and support design. In addition, this study will serve as a valuable basic document for the geotechnical engineer to design and plan support systems in the excavation of galleries under high in-situ stress.

Download Full-text