SURFACE SETTLEMENT INDUCED BY TUNNELING IN GREENFIELD CONDITION THROUGH PHYSICAL MODELLING

2015 ◽  
Vol 76 (2) ◽  
Author(s):  
Aminaton Marto ◽  
Mohamad Hafeezi Abdullah ◽  
Ahmad Mahir Makhtar ◽  
Houman Sohaei ◽  
Choy Soon Tan
Keyword(s):  
Relative Density ◽  
Physical Modelling ◽  
Diameter Ratio ◽  
Surface Settlement ◽  
Ground Movement ◽  
Outer Diameter ◽  
Tunnel Excavation ◽  
Tunneling Method ◽  
Relative Density Of Sand ◽  
Tunnel Shield

Geotechnical conditions such as tunnel dimensions, tunneling method and soil type are few factors influencing the ground movement or disturbance.  This paper presents the effect of tunnel cover to diameter ratio and relative density of sand on surface settlement induced by tunneling using physical modelling. The aluminum casing with outer diameter of 50 mm was used to model the tunnel shield. The size of the casing was 2 mm diameter larger than the tunnel lining. The tunnel excavation was done by pulling out the tunnel shield at constant speed with a mechanical pulley. The tested variables are cover to diameter ratio (1, 2 and 3) and relative density of sand (30%, 50% and 75%). The results demonstrated that the surface settlement decreased as the relative density increased. Also, as the relative density of sand increased, the overload factor at collapse increased. The surface settlement was at the highest when the cover to diameter ratio was 2.  It can be concluded that in greenfield condition, the relative density and cover to diameter ratio affect the surface settlement.

3D Numerical Analysis of Soil Structure Interaction Behaviors of Pipe Jacking Construction

2012 ◽  
Vol 204-208 ◽  
pp. 534-538 ◽  
Author(s):  
Wen Tsung Liu ◽  
Xu Yan Lu
Keyword(s):  
Numerical Analysis ◽  
Soil Structure ◽  
Soil Improvement ◽  
Ground Movement ◽  
Science Park ◽  
Tunnel Excavation ◽  
Contraction Ratio ◽  
Pipe Jacking ◽  
Interaction Behaviors ◽  
Plaxis 3D

This study is analyzed by numerical analysis using finite element method program of Plaxis-3D Tunnel at Kaohsiung Science Park in Taiwan. It probes the risk of tunneling procedure adopting pipe jacking construction (PJC) with man–made excavation. The main parameters of numerical calculation in this research include advancement size, soil improvement ratio and void contraction ratio, etc. Those parameters are calculated to displacement and stress distribution and we get ground movement, settlement at crown and heave at invert of tunnel excavation to assess the security. This study finds that it is safe by excavation using PJC with man-made while the gap has to be less than 38mm. Actually, the gap is 100 ~ 150mm under PJC with man-made, and it will result in high risk. Therefore, the PJC with shield has more security than other methods through monitoring ground settlement.

scholarly journals Ground deformation mechanism due to deep excavation in sand: 3D numerical modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 741-747
Keyword(s):  
Relative Density ◽  
Deformation Mechanism ◽  
Ground Deformation ◽  
Ground Movement ◽  
Soil Stiffness ◽  
Maximum Settlement ◽  
Hypoplastic Model ◽  
3D Numerical Modelling ◽  
Path Dependent ◽  
Underground Transportation

In densely built areas, development of underground transportation system often involves excavations for basement construction and cut-and-cover tunnels which are sometimes inevitable to be constructed adjacent to existing structure. Inadequate support systems have always been major concern as excessive ground movement induced during excavation could damage to neighbouring structure. A detailed parametric analysis of the ground deformation mechanism due to excavation with different depths in sand with different densities (Dr=30%, 50%, 70% and 90%) is presented. 3D finite element analyses were carried out using a hypoplastic model, which considers strain-dependent and path-dependent soil stiffness. The computed results have revealed that the maximum settlement decreased substantially when the excavation is carried out in the sand with higher relative density. This is because of reason that sand with higher relative density possesses higher stiffness. Moreover, the depth of the maximum settlement of the wall decreases as the sandbecome denser.The ground movement flow is towards excavation in retained side of the excavation. On the other hand the soil heave was induced below the formation level at excavation side. The maximum strain level of 2.4% was induced around the diaphragm wall.

scholarly journals Effects of different processes of tunneling on displacements soil using 3D Finite Element Method

2021 ◽  
Vol 16 (2) ◽  
pp. 203-217
Author(s):  
Nawel Bousbia
Keyword(s):  
Three Dimensional ◽  
Urban Site ◽  
Tunnel Excavation ◽  
Excavation Process ◽  
Tunneling Method ◽  
The Stability ◽  
Full Face ◽  
Ground Stability ◽  
3D Finite Element Method ◽  
Underground Constructions

Abstract The excavation process of tunnels induces stresses and deformation in the surrounding soil. The method of excavation is one of the major problems related to the safety of the operators and the ground stability during the construction of underground works. So, it is necessary to choose an ideal method to minimize the displacements and stresses induced by tunneling. The main aim of this study is to simulate numerically the effect of different processes of tunneling on ground displacements, the settlements at surface soil and the internal efforts induced in the lining tunnel; in order to select the best process of excavation, which gives us a less effects on displacements generated by tunneling, thus, ensuring the stability and the solidity of the underground constructions. In addition, this study allows us to control and to predict the diverse movements generated by tunneling (displacements, settlements, efforts internes) exclusively for the shallow tunnel nearby to the underground constructions in the urban site. This modeling will be done by employing five different processes for tunnel excavation using the NATM (New Austrian Tunneling Method) method. The first process, the modeling of the excavation tunnel, is done almost in the same way as in reality; the partial face excavation, with seven slices, made by the excavation. The second process, by partial face excavation, is divided into eleven slices, next, we used the partial face excavation by nine slices, and then in thirteen slices. Finally, the dig is made by full-face excavation. The paper contributes to the prediction of the response of the soil environment to tunnel excavation using the NATM method and to minimize the diverse movements generated by tunneling. The appropriately chosen methodology confirms that displacements and subsidence are strongly influenced by the tunneling method. The three-dimensional Finite Elements Method using Plaxis3D program has been applied in the numerical simulation. The study resulted in the recommendation of a process that minimizes the effect of excavation on subsidence and ground displacement for a particular Setiha tunnel.

Electrically-Launched mm-sized Hypervelocity Projectiles

2019 ◽  
Author(s):  
W. Casey Uhlig ◽  
Paul R. Berning ◽  
Peter T. Bartkowski ◽  
Matthew J. Coppinger
Keyword(s):  
Transmission Lines ◽  
Hypervelocity Impact ◽  
Diameter Ratio ◽  
Outer Diameter ◽  
Proof Of Concept ◽  
Copper Anode ◽  
Mhd Simulations ◽  
Electromagnetic Launch ◽  
Series Of Experiments ◽  
Launch Systems

Abstract A series of experiments and simulations were performed as proof of concept that an electrically powered research gun could propel small cylindrical projectiles to hypervelocities. Although small-caliber electrothermal accelerators and other electromagnetic launch systems have been utilized for some years for laboratory hypervelocity impact and other studies [1-5], we developed a simple, reproducible device that allows impact studies and direct comparison to magnetohydrodynamic (MHD) simulations for design considerations, efficiency improvements, and validation studies. This work focusses on 4.8 mm cylindrical 7075-T6 aluminum projectiles with a length to diameter ratio of one (nominally a mass of 0.24 grams) and a 150-mm long, 25-mm outer-diameter 4043 steel barrel with a 4.8-mm diameter bore and 9.5-mm chamber that acts as the electrical cathode. The anode consists of a 6.3-mm diameter copper rod that is reduced to 2.9 mm then tapered to a point with the tip length over diameter ratio (L/D) varying from 2 to 5. The tip is placed at the chamber/bore junction. The copper anode is insulated by a polyethylene sleeve and epoxy surrounding the electrode such that the arc initiates only at the very tip. A 191 μF capacitor was used as the power source for all experiments. The applied voltage was varied from 10 kV to 20 kV, and the resulting inductance of the system varied from approximately 320 nH to 450 nH (due to varying separation in the copper transmission lines). Fits to the current pulse using an LRC circuit resulted in resistance on the order of 10 mΩ to 15 mΩ. Typically the portion of the electrical pulse responsible for the bulk of the acceleration of the projectile occurs within the first 15 μs; however, the projectile is accelerated during the entirety of the time it remains in the barrel, which is on the order of 40 μs to 50 μs.

Surface Settlement Law Induced by Shield Tunnel Excavation Using Modified Gap Model

2012 ◽  
Vol 170-173 ◽  
pp. 1515-1519
Author(s):  
Wen Bo Li ◽  
Wen Pei Wang ◽  
Lian Jin Tao ◽  
Yin Tao Zhang
Keyword(s):  
Critical Value ◽  
Surface Settlement ◽  
Shield Tunnel ◽  
Gap Model ◽  
Tunnel Excavation ◽  
Maximum Settlement ◽  
Maximum Surface ◽  
Adjacent Buildings ◽  
Maximum Surface Settlement ◽  
Tunnel Depth

GAP model will be modified and programmed by FISH language, which can be used in FLAC2D programs. The modified GAP model is used to study the variation of surface settlement shape with depth, the variation of the maximum settlement value with depth, and the variation of settlement gradient with depth. The results show that: the settlement shape is narrow and deep with the conditions of shallow buried depth of tunnel; on the contrary, the settlement shape is wide and shallow; When the tunnel depth is less than the critical value, the tunnel depth and the maximum surface settlement is approximately linear; when the tunnel depth is greater than the critical value, the curve of maximum surface settlement value with depth becomes flat and with the increase of the tunnel, the surface settlement gradient gradually decreases and eventually tends to zero. It is more reasonable to assess the influence of tunnel excavation near adjacent buildings, using the maximum surface settlement and the settlement gradient as a control standard.

Sign in / Sign up

Export Citation Format

Share Document