Effects of tunnel face distance on surface settlement

2016 ◽  
pp. 323-326
Author(s):  
A Marto ◽  
H Sohaei ◽  
M Hajihassani ◽  
A Makhtar
Keyword(s):  
Surface Settlement ◽  
Tunnel Face

scholarly journals Displacement Characteristics of an Urban Tunnel in Silty Soil by the Shallow Tunnelling Method

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Shaobing Zhang ◽  
Siyue He ◽  
Junling Qiu ◽  
Wei Xu ◽  
Rodney Sheldon Garnes ◽  
...  
Keyword(s):  
Soil Surface ◽  
Surface Settlement ◽  
In Situ Monitoring ◽  
Good Effect ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Face Surface ◽  
Silty Soil ◽  
Construction Methods ◽  
Jet Grouting

The urban shallow tunnelling process in silty soil is easy to cause large displacement of surface and tunnel. Obviously, if the strata and the tunnel face are not treated by reasonable reinforcement method, instability and collapse phenomenon will be encountered during the tunnel excavation. There are a series of studies on construction methods of shallow tunnels, but these methods have limitations in silty soil. In this study, a comprehensive construction plan of the urban shallow tunnel in silty soil was proposed and applied to a case study in Fuzhou, Fujian Province in South China. The in situ monitoring tests and numerical simulation were employed to address displacement characteristics of surface and tunnel. Results indicated that the urban shallow tunnelling process could achieve good effect by dewatering of silty soil, reinforcing surface by vertical jet grouting piles, and advanced small pipes and circumferential grouting in the tunnel face; surface settlement during dewatering process accounted for about 30% of total surface settlement in silty soil; the excavation of the top heading, the middle, and lower benches had great effect on displacement of surface and tunnel for three-bench seven-step excavation method in silty soil; surface settlement troughs in silty soil were deeper and wider; lock-feet bolts had good effect on restricting horizontal convergence; and ratio of total crown settlement and total horizontal convergence was in range of 1.43∼1.59 when b/h was 0.88 in silty soil. The construction plan proposed in this paper is helpful for further study of shallow tunnel tunnelling process in silty soil.

Effects of tunnel face distance on surface settlement

2016 ◽  
pp. 321-326
Author(s):  
A. Marto ◽  
H. Sohaei ◽  
M. Hajihassani ◽  
M.A. Makhtar
Keyword(s):  
Surface Settlement ◽  
Tunnel Face

Analysis on Ground Settlement Induced by Shallow Buried Cross Channel of CRD Method under Artificial Filling

2013 ◽  
Vol 353-356 ◽  
pp. 1519-1524
Author(s):  
Jin Kui Li ◽  
Jing Jing Li ◽  
Liu Jie Du
Keyword(s):  
Surface Deformation ◽  
Settling Tank ◽  
Ground Surface ◽  
Surrounding Rock ◽  
Surface Settlement ◽  
Ground Settlement ◽  
Tunnel Face ◽  
Underground Tunnel ◽  
The Cross ◽  
The Stability

The shallow underground tunnel is near to the ground; its many construction procedures are complicated, supporting and excavation are intertwined. The ground surface deformation is complex during construction. Through the analysis of the cross passage surface settlement data of Dalian metro Line 1High-tech zone Street station, we found that the ground surface caused by artificial filling integrally sinks during excavation, the shape of its sinking is like a flat funnel, the characteristics of settling tank are obvious. The influence of faces constructing is obvious on surface settlement, and the transverse influence range is about 30m; the longitudinal influence range is about 15m. The results of the paper show that the place of monitoring points should be held at 15m ahead from the tunnel face, effectivemonitoring period is 70d. The monitoring results are enough and safe for the stability requirement of the surrounding rock.

scholarly journals Prediction and analysis of surface settlement due to shield tunneling for Xi’an Metro

2017 ◽  
Vol 54 (4) ◽  
pp. 529-546 ◽  
Author(s):  
Caihui Zhu ◽  
Ning Li
Keyword(s):  
Influence Factors ◽  
Estimation Method ◽  
Prediction Method ◽  
Surface Settlement ◽  
Upper And Lower Bounds ◽  
Support Pressure ◽  
Shield Tunneling ◽  
Tunnel Face ◽  
Tunneling Method ◽  
Gp Model

This study describes a new modified prediction method of surface settlement (SS) for Xi’an Metro. The estimation method of SS and its characteristic parameters, volume loss (VL), maximal SS, and settlement trough width (STW) are reviewed and discussed in this paper. The gap parameter (GP) is applied to estimate VL; however, the calculation method of GP and its influence factors have not been clarified entirely. In this study, six influence factors are introduced into the new GP model, and the detailed solutions are presented. This estimation method is able to take into account the support pressure of the shield head at the tunnel face, the lining support pressure around the tunnel opening, the filling effect of tail grouting, yawing, and pitching of the shielding machine, and the long-term deformation of the remoulded surrounding soil. Based on Xi’an Metro line 2, the soil behaviors and measured SS characteristics are deeply investigated. The upper and lower bounds of the total GP of the 15 cases are predicted. Comparison of the predicted SS troughs with field observations can show reasonable agreement. It is suggested that the new estimation method can be used effectively in estimating the SS induced by the shield tunneling method.

scholarly journals Evaluating the effect of EPBM operational parameters on surface settlement in soft ground

2020 ◽  
Author(s):  
Ali Naghi Dehghan ◽  
Ehsan Bagheri ◽  
Meysam Khodaei ◽  
Rouzbeh Imani Kalehsar
Keyword(s):  
Ground Surface ◽  
Coupled Model ◽  
Earth Pressure ◽  
Surface Settlement ◽  
Ground Settlement ◽  
Operational Parameters ◽  
Pressure Balance ◽  
Tunnel Face ◽  
Earth Pressure Balance ◽  
Parametric Analyses

Abstract The present study investigates the effects of some essential earth pressure balance machine (EPBM) operational parameters, including face, annulus and grout pressures, on ground surface settlement during tunnel excavation. A numerical soil-tunnel-fluid coupled model was developed using the finite difference method (FDM) in FLAC3D for the basis of this research. Hence, the effects of geostatic stress in the tunnel face and annulus and the grout pressure behind the segment on ground settlement were investigated by parametric analyses. The results indicated that a reduction in the boundary pressure (from 508 to 335 kPa) on the face and annulus space did not change the settlement significantly, altering the settlement from 1.18 to 1.48 mm. The results of parametric grout pressure analysis showed that applying a grout pressure equal to the vertical geostatic stress (i.e. 335 kPa) had a larger effect than applying horizontal geostatic stress (i.e. 357 kPa) to the tunnel face on controlling the ground settlement—i.e. 1.45 and 1.20 mm, respectively. A lateral earth pressure of below 1 (K0 < 1) led to the estimation of horizontal geostatic stress value that was lower than the vertical geostatic stress value, thereby applying a lower effect to controlling the ground settlement. Grout pressure increment relative to the vertical geostatic stress considerably reduced the ground settlement. However, an excessive rise in the grout pressure could lead to deformation and upward displacements in the form of ground heaving at a transverse distance of above 20 m from the tunnel axis.

scholarly journals Seepage in Water-Rich Loess Tunnel Excavating Process and Grouting Control Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhengde Wei ◽  
Yanpeng Zhu
Keyword(s):  
Moisture Content ◽  
Surrounding Rock ◽  
Gansu Province ◽  
Surface Settlement ◽  
High Moisture Content ◽  
Control Effect ◽  
High Moisture ◽  
Tunnel Face ◽  
Construction Methods ◽  
Curtain Grouting

The tunnel passing through the loess stratum with high moisture content can easily lead to the seepage and mud burst accident and the instability and collapse of the tunnel face. Under the condition of high groundwater level, the seepage situation is more complicated, it is difficult to control the groundwater seepage, and the excavation progress is very slow. In order to solve the various disasters when the tunnel passes through the water-rich loess stratum, taking a water-rich loess tunnel in Gansu Province as an example, the method of comprehensive prevention and control of seepage and mud inrushing disaster by basement grouting and curtain grouting was introduced. Firstly, the basic situation of the Yulinzi tunnel is introduced, including site conditions, seepage collapse accident, and its cause analysis. On this basis, the design and construction methods of basement grouting and curtain grouting are introduced, and the effect of grouting reinforcement is evaluated in detail through on-site monitoring. The results show that the basement grouting and curtain grouting can effectively control the deformation of surrounding rock and the surface settlement, the decrease of the deformation of surrounding rock can reach 36%-71%, and the decrease of the surface settlement can reach 55%. After grouting, the deformation of the surface and surrounding rock can be controlled within the allowable value in the code. Grouting plus solid can effectively block the seepage of groundwater and prevent the surface cracks, water gushing, mud gushing, collapse, and other disasters in the process of tunnel excavation. It can be seen that the basement grouting combined with curtain grouting technology has a good reinforcement effect, which has significant engineering value for quickly and efficiently passing through high moisture content loess strata.

scholarly journals Characteristics of Stress Transfer and Progressive Fracture in Overlying Strata due to Mining-Induced Disturbances

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Xiang-feng Lv ◽  
Hong-yuan Zhou ◽  
Ai-wen Wang ◽  
Chun Feng ◽  
Xiao-chun Xiao
Keyword(s):  
Numerical Simulation ◽  
Underground Mining ◽  
Ground Surface ◽  
Stress Transfer ◽  
Surface Settlement ◽  
Stress Concentrations ◽  
Tunnel Face ◽  
Working Face ◽  
Ground Surface Settlement ◽  
Overlying Strata

In this study, based on the mining of the 13210 working face in the Yima coal mine of the Gengcun village, China, a simplified mechanical model for the analysis of dynamic destabilization of the overlying strata during underground mining was constructed. The numerical simulation was used to analyze the stress patterns in the advanced abutments of the tunnel face and the characteristics of dynamic failures in the overlying strata. Furthermore, similitude experiments were conducted to study the process of stress release and deformation in the overlying strata, and to analyze the effects of overburden destabilization on the ground surface settlement. The theoretical analysis indicated that if the geometric parameters of a working face are fully determined, a stiffness ratio no greater than 1 is required for dynamic destabilization to occur. The numerical simulation results show that the stress in the overlying strata decreases with a decrease in distance from the tunnel face. The stresses in the advanced abutments initially increase with an increase in distance from the tunnel face, followed by a decrease in stress, and an eventual stabilization of the stress levels; this corresponds to the existence of a “stress build-up zone,” “stress reduction zone,” and “native rock stress zone.” In similitude experiments, it was observed that a “pseudoplastic beam” state arises after the local stresses of the overlying strata have been completely released, and the “trapezoidal” fractures begin to form at stress concentrations. If the excavation of the working face continues to progress, the area of collapse expands upward, thereby increasing the areas of the fracture and densification zones. Owing to the nonuniform settlement of the overlying strata and the continuous development of bed-separating cracks, secondary fractures will be generated on both sides of the working face, which increase the severity of the ground surface settlement.

Effect of Geocell Reinforcement above Buried Pipes on Surface Settlement

2018 ◽  
Vol 9 (2) ◽  
pp. 86 ◽  
Author(s):  
Mohammed Yousif Fattah ◽  
Waqed Hameed Hassan ◽  
Sajjad E. Rasheed
Keyword(s):  
Surface Settlement ◽  
Buried Pipes ◽  
Geocell Reinforcement
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