scholarly journals Numerical Simulation and Analysis of the Three-Step Excavation of an Extra-Large Cross-Section and a Low Flat-Ratio Railway Tunnel

2021 ◽  
Author(s):  
Wenxing Huo ◽  
Xue Shifeng ◽  
Zongzhi Zhao ◽  
Zhiyu Gao ◽  
Mingyue Shao
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Cross Section ◽  
Axial Force ◽  
Side Wall ◽  
Vertical Deformation ◽  
Large Cross Section ◽  
Railway Tunnel ◽  
Geological Conditions ◽  
Deformation Section

Abstract The Xinbaishiyan tunnel in the reconstruction Chengdu-Kunming railway Ermeishan-Mipan section mainly runs through dolomite with dolomitic limestone, with an excavation area of 260 m2, a maximum span of 22.3 m, a maximum height of 14.4 m, a vector height of 7 m, and a rise-span ratio of 0.31. The tunnel has an extra-large cross-section and it is a low flat-ration railway tunnel. This paper mainly describes the the finite element analysis for this tunnel excavation that was used to guide the construction. Finite element software was used to model the tunnel according to the engineering geological conditions of the tunnel. These engineering geological conditions included the rock mass, system bolts, middle pipe shed, steel arch and shotcrete, grouting layer, second lining and so on. Nonlinear construction phase analysis was adopted. The results showed that the maximum vertical deformation of the tunnel vault and the middle of the invert was about 34 mm. The vertical deformation of the tunnel could be divided into an acceleration deformation section, linear deformation section, deceleration deformation section, and stable deformation section. The maximum horizontal deformation in the middle of the side wall was about 12.3 mm. Under the effect of the initial support, the equivalent stress of the side wall gradually increased with the excavation of the steps and the increase of the support structure. The axial force of the bolt in the middle of the side wall was larger than that in other places and the axial force of the middle pipe shed went along with the excavation of the tunnel in waves. The steel arch and the shotcrete had the maximum effective stress at the arch shoulder, which played the role of the deformation and pressure for the surrounding rock. During the construction, the length and height of the three-step method had to be set reasonably. The middle pipe shed and the system bolt supported the rock mass together. In the construction of the extra-large cross section and the flat tunnel, there was no need to set up temporary support, which was convenient for mechanical excavation.

scholarly journals Tunnel support design by comparison of empirical and finite element analysis of the Nahakki tunnel in mohmand agency, pakistan

2016 ◽  
Vol 38 (1) ◽  
pp. 75-84
Author(s):  
Asif Riaz ◽  
Syed Muhammad Jamil ◽  
Muhammad Asif ◽  
Kamran Akhtar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Rock Mass ◽  
Support Systems ◽  
Classification Systems ◽  
Geological Strength Index ◽  
Support Design ◽  
Element Analysis ◽  
Tunnel Support ◽  
Geological Conditions

Abstract The paper analyses the geological conditions of study area, rock mass strength parameters with suitable support structure propositions for the under construction Nahakki tunnel in Mohmand Agency. Geology of study area varies from mica schist to graphitic marble/phyllite to schist. The tunnel ground is classified and divided by the empisical classification systems like Rock mass rating (RMR), Q system (Q), and Geological strength index (GSI). Tunnel support measures are selected based on RMR and Q classification systems. Computer based finite element analysis (FEM) has given yet another dimension to design approach. FEM software Phase2 version 7.017 is used to calculate and compare deformations and stress concentrations around the tunnel, analyze interaction of support systems with excavated rock masses and verify and check the validity of empirically determined excavation and support systems.

The Comparison and Selection of the Solutions for Liuyang River Tunnel’s Inclined Shaft Entering to the Main Hole and the Key Points of Construction

2012 ◽  
Vol 197 ◽  
pp. 149-153
Author(s):  
Zhi Min Xiang ◽  
Ren Ai Yuan
Keyword(s):  
Cross Section ◽  
Geological Condition ◽  
Large Cross Section ◽  
Transition Section ◽  
Advantages And Disadvantages ◽  
Construction Scheme ◽  
Key Points ◽  
Geological Conditions ◽  
Efficient Construction ◽  
Selection Of

The construction geological condition is complex in the transition section from the inclined shaft to the main hole. There are two kinds of construction schemes. After the comparison of the advantages and disadvantages of the two different construction schemes, it has selected the construction scheme of the rectangular pilot tunnel vertical to the main hole. This paper solve the construction problem of the transition section from the inclined shaft to the main hole of large cross section tunnel of passenger dedicated line under complicated geological conditions. According to the previous research results, the method can be used to large-cross section tunnel. The scaffold design and auxiliary construction measures is detailed. Compared with the expected duration, it completed the transition construction ahead of time with the speed superior to the ones of other similar works, and forming a safe and efficient construction situation.

scholarly journals Engineering geological investigations for evaluation of excavation method and stand-up time of the DK99-DK100 Jakarta – Bandung high-speed railway tunnel, Indonesia

2021 ◽  
Vol 325 ◽  
pp. 01005
Author(s):  
Linda Ali ◽  
I Gde Budi Indrawan ◽  
Hendarto Hendarto
Keyword(s):  
Rock Mass ◽  
High Speed ◽  
Poor Quality ◽  
Geological Strength Index ◽  
Rock Masses ◽  
Railway Tunnel ◽  
Tunnel Excavation ◽  
High Speed Railway ◽  
Geological Conditions ◽  
Subsurface Engineering

This paper presents the investigation of surface geology and subsurface engineering geology to analyze the excavation method and stand-up time of the DK99-DK100 Jakarta-Bandung high-speed railway Tunnel, Indonesia. Rock mass quality, tunnel excavation method, and stand-up time determined using Geological Strength Index (GSI), Basic Quality (BQ) systems, converted to Rock Mass Rating (RMR) and The Japan Society of Civil Engineering (JSCE) for comparison. The result shows that the study area consists of slightly to completely weathered andesite breccia and slightly weathered andesite lava. The rock masses at the tunnel elevation had very poor to poor quality and were associated with high weathering degrees. The recommended rock excavation method based on the GSI is digging. The recommended tunnel excavation method based on RMR is multiple drifts, top heading, and bench, while based on JSCE is bench cut method. The tunnel stand-up time is 30 minutes - 2 hours based on the RMR, while it is predicted to be unstable without support based on the BQ. The recommended design is expected to be applied effectively according to the geological conditions. It is expected to understand better the tunnel excavation method in poor rock masses, especially in Indonesia.

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