Interaction of longitudinal surface settlements for twin tunnels in shallow and soft soils: the case of Istanbul Metro

2012 ◽  
Vol 69 (5) ◽  
pp. 1673-1683 ◽  
Author(s):  
Ibrahim Ocak
Keyword(s):  
Soft Soils ◽  
Surface Settlements ◽  
Twin Tunnels

Effects of the construction sequence of twin tunnels at different depths on an existing pile

2014 ◽  
Vol 51 (2) ◽  
pp. 173-183 ◽  
Author(s):  
C.W.W. Ng ◽  
H. Lu
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Pile Capacity ◽  
Tunnel Excavation ◽  
Construction Sequence ◽  
Pile Shaft ◽  
Different Depths ◽  
Pile Settlement ◽  
Surface Settlements ◽  
Twin Tunnels

Any tunnelling process inevitably induces changes in stress in the ground and may adversely affect nearby pile foundations. The interaction between tunnelling and an existing pile has been investigated by researchers and a certain amount of fundamental understanding has been gained. However, the effects of different tunnel excavation sequences on an adjacent pile remain to be understood. In this paper, a series of three-dimensional centrifuge model tests and numerical back-analyses were carried out to investigate the effects of construction sequence of twin tunnels on an existing pile in dry sand. Two tunnelling sequences were investigated: (i) a sequence involving tunnelling near the pile toe followed by tunnelling near the mid-depth of the pile shaft (i.e., test TS); (ii) sequence involving tunnelling near the mid-depth of the pile shaft followed by tunnelling near the pile toe (i.e., test ST). The measured cumulative pile settlement was about 33% larger for tunnelling sequence ST than for tunnelling sequence TS. Due to different tunnelling sequences, the apparent losses of pile capacity were 40% and 29% for sequences ST and TS, respectively. Although the computed reductions in normal stress acting on the pile induced by twin tunnelling were almost the same in tests TS and ST, tunnelling near the pile toe induced a larger decrease in the end-bearing and shaft resistances at the lower part of the pile in test ST than in test TS. In contrast to the measured pile head settlements, different tunnelling sequences had a limited effect on measured ground surface settlements and additional bending moments in the pile.

Surface Settlements Caused by Three-Bench Seven-Step-Excavation of Large Span Twin Tunnels

2015 ◽  
Vol 744-746 ◽  
pp. 988-991
Author(s):  
Li Yan ◽  
Jun Sheng Yang ◽  
Kang Nan
Keyword(s):  
Cross Section ◽  
Ground Surface ◽  
Weak Rock ◽  
Construction Time ◽  
Large Span ◽  
Cross Section Area ◽  
Section Area ◽  
Weak Rock Mass ◽  
Surface Settlements ◽  
Twin Tunnels

As a new method, the three-bench seven-step-excavation method is more and more adopted by the construction of large span tunnel in weak rock mass. At the portal of Yunyangshan tunnel, there is a long section of the mild clay stratum. Considered that the whole excavated cross section area is very large, the three-bench seven-step-excavation method was adopted. In order to investigate the surface settlements caused by the construction of twin tunnels, three typical cross-section were selected. At each section, the ground surface settlements were monitored. It is shown that the depth of tunnel and the construction time of twin tunnels have influence on the surface settlement curves, and the three-bench seven-step-excavation is effective in the mild clay stratum.

Determining The Minimum Distance Between Centers of Two Parallel Tunnels to Apply The Law of Super Position in Order to Calculate Subsidence by Using The Software FLAC 3D

2015 ◽  
Vol 1 (1) ◽  
pp. 13-20
Author(s):  
Hamid Reza Samadi ◽  
Mohammad Reza Samadi
Keyword(s):  
Minimum Distance ◽  
Surface Subsidence ◽  
Urban Traffic ◽  
Underground Structures ◽  
Rapid Population Growth ◽  
The North ◽  
Flac 3D ◽  
The Law ◽  
3D Software ◽  
Twin Tunnels

Due to the development of cities as well as rapid population growth, urban traffic is increasing nowadays. Hence, to improve traffic flow, underground structures such as metro, especially in metropolises, are inevitable. This paper is a research on the twin tunnels Of Isfahan's metro between Shariaty station and Azadi station from the North towards the South. In this study, simultaneous drilling of subway's twin tunnels is simulated by means of Finite Difference Method (FDM) and FLAC 3D software. Moreover, the lowest distance between two tunnels is determined in a way that the Law of Super Position could be utilized to manually calculate the amount of surface subsidence, resulted by drilling two tunnels, by employing the results of the analysis of single tunnels without using simultaneous examination and simulation. In this paper, this distance is called "effective distance". For this purpose, first, the optimum dimensions of the model is chosen and then, five models with optimum dimensions will be analyzed separately, each of which in three steps. The results of analyses shows that the proportions (L/D) greater than or equal 2.80, the Law of Super Position can be applied for prediction of surface subsidence, caused by twin tunnels' construction

Granular Pile Anchors For Soft Soils

2014 ◽  
Vol 4 (3) ◽  
pp. 15-24 ◽  
Author(s):  
O. Eswara Reddy ◽  
◽  
Madhav. M.R ◽  
Saibaba Reddy.E ◽  
Vidyaranya Bandi ◽  
...  
Keyword(s):  
Soft Soils ◽  
Granular Pile

Stability Analysis of the Nanjung Water Diversion Twin Tunnels based on Convergence Measurement

2019 ◽  
Vol 1 (1) ◽  
pp. 49-60
Author(s):  
Simon Heru Prassetyo ◽  
Ganda Marihot Simangunsong ◽  
Ridho Kresna Wattimena ◽  
Made Astawa Rai ◽  
Irwandy Arif ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Convergence Rate ◽  
Critical Strain ◽  
Convergence Rates ◽  
Strain Analysis ◽  
Water Diversion ◽  
Tunnel Face ◽  
Tunnel Stability ◽  
The Stability ◽  
Twin Tunnels

This paper focuses on the stability analysis of the Nanjung Water Diversion Twin Tunnels using convergence measurement. The Nanjung Tunnel is horseshoe-shaped in cross-section, 10.2 m x 9.2 m in dimension, and 230 m in length. The location of the tunnel is in Curug Jompong, Margaasih Subdistrict, Bandung. Convergence monitoring was done for 144 days between February 18 and July 11, 2019. The results of the convergence measurement were recorded and plotted into the curves of convergence vs. day and convergence vs. distance from tunnel face. From these plots, the continuity of the convergence and the convergence rate in the tunnel roof and wall were then analyzed. The convergence rates from each tunnel were also compared to empirical values to determine the level of tunnel stability. In general, the trend of convergence rate shows that the Nanjung Tunnel is stable without any indication of instability. Although there was a spike in the convergence rate at several STA in the measured span, that spike was not replicated by the convergence rate in the other measured spans and it was not continuous. The stability of the Nanjung Tunnel is also confirmed from the critical strain analysis, in which most of the STA measured have strain magnitudes located below the critical strain line and are less than 1%.

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