• Title, Summary, Keyword: Surface settlement

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A Trend of Back Ground Surface Settlement of Braced Wall Depending on the Joint Dips in Rocks under the Soil Strata (복합지반 굴착 시 암반층 절리경사 각도별 흙막이 벽체 배후 지표침하의 경향)

  • Bae, Sang-Su;Lee, Sang-Duk
    • Journal of the Korean Geotechnical Society
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    • v.32 no.11
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    • pp.83-96
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    • 2016
  • The surface settlement of the back ground of a braced wall due to the ground excavation has the great influence on the safety of the surrounding area. But it is not easy to predict the settlement of the surrounding area due to proud excavation. Estimation of the settlement of the surface ground induced by the deformation of the braced wall is performed by FEM and empirical method (Peck, Clough etc). In this research, surface settlement of the back ground braced wall depending on the joint dips in rocks during excavating the composit ground was measured at the large scale model test (standard: $0.3m{\times}0.3m{\times}0.5m$). The scale of model test was 1/14.5 and the ground was excavated in ten steps. Earth pressure on the braced wall and ground surface settlement on the back ground of a braced wall were investigated. The surface settlement during the excavation depended on the joint dips in rocks on of the ratio of rock layer. Maximum earth pressure and maximum surface settlement were masured at the same excavation step. In accordance with the increase of the rock layer dips and rock layer ratio, the ground surface settlement increased. The maximum ground surface settlement was 17 times larger at 60 degree joint dips in rocks than that of the horizontal ground conditions. And the position of the maximum surface settlement by empirical method was calculated at the point, which was 17%~33% of excavation depth. In accordance with the increase of the rock layer dips and rock layer ratio, the ground maximum surface settlement increased. The ground surface settlement of composite ground is smaller than that of the empirical.

Critical face pressure and backfill pressure in shield TBM tunneling on soft ground

  • Kim, Kiseok;Oh, Juyoung;Lee, Hyobum;Kim, Dongku;Choi, Hangseok
    • Geomechanics and Engineering
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    • v.15 no.3
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    • pp.823-831
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    • 2018
  • The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.

Research on surface settlement prediction based on the combination prediction model of S-shaped growth curves

  • Su, Ying;Wang, Xiaoqin;Fu, Yuanyuan;Zheng, Xianjun;You, Gaoshuai
    • Geosystem Engineering
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    • v.21 no.4
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    • pp.236-241
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    • 2018
  • After studying the development law of surface settlement induced by excavation of foundation pit and the characteristics of the settlement curve, the paper introduces the idea of combination forecasting based on S-shaped growth curves and establishes the weight combination prediction model, which is applied to the actual project to verify the rationality of the model. Results show that the model cannot only reflect the settlement development process along with time, but also predict the surface settlement accurately. In addition, the combination prediction model is more superior to other single ones, and provides an effective and practical method for surface settlement forecasting.

Determination of effective parameters on surface settlement during shield TBM

  • Kim, Dongku;Pham, Khanh;Park, Sangyeong;Oh, Ju-Young;Choi, Hangseok
    • Geomechanics and Engineering
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    • v.21 no.2
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    • pp.153-164
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    • 2020
  • Tunnel excavation in shallow soft ground conditions of urban areas experiences inevitable surface settlements that threaten the stability of nearby infrastructures. Surface settlements during shield TBM tunneling are related to a number of factors including geotechnical conditions, tunnel geometry and excavation methods. In this paper, a database collected from a construction section of Hong Kong subway was used to analyze the correlation of settlement-inducing factors and surface settlements monitored at different locations of a transverse trough. The Pearson correlation analysis result revealed a correlation between the factors in consideration. Factors such as the face pressure, advance speed, thrust force, cutter torque, twin tunnel distance and ground water level presented a modest correlation with the surface settlement, while no significant trends between the other factors and the surface settlements were observed. It can be concluded that an integrated effect of the settlement-inducing factors should be related to the magnitude of surface settlements.

지하수 채수에 따른 지반침하 사례분석

  • 정하익;구호본
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.168-171
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    • 2001
  • It is a common practice to extract water from the ground for domestic, agricultural or industrial uses or to lower the groundwater level for construction work. An accurate prediction of ground settlement Is sometimes crucial when groundwater is pumped. This case study have shown that drawdown of the groundwater table may cause ground subsidence. Many settlement gauges was installed in the vicinity of a pumped well to measure the surface settlement. The relationships between the level of groundwater drop and surface settlement is investigated In this research.

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Prediction methods on tunnel-excavation induced surface settlement around adjacent building

  • Ding, Zhi;Wei, Xin-jiang;Wei, Gang
    • Geomechanics and Engineering
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    • v.12 no.2
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    • pp.185-195
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    • 2017
  • With the rapid development of urban underground traffic, the study of soil deformation induced by subway tunnel construction and its settlement prediction are gradually of general concern in engineering circles. The law of soil displacement caused by shield tunnel construction of adjacent buildings is analyzed in this paper. The author holds that ground surface settlement based on the Gauss curve or Peck formula induced by tunnel excavation of adjacent buildings is not reasonable. Integrating existing research accomplishments, the paper proposed that surface settlement presents cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics when the tunnel is respectively under buildings, within the scope of the disturbance and outside the scope of the disturbance. Calculation formulas and parameters on cork distribution curve and skewed distribution curve were put forward. The numerical simulation, experimental comparison and model test analysis show that it is reasonable for surface settlement to present cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics within a certain range. The research findings can be used to make effective prediction of ground surface settlement caused by tunnel construction of adjacent buildings, and to provide theoretical guidance for the design and shield tunnelling.

Numerical simulation for surface settlement considering face vibration of TBM tunnelling in mixed-face condition (복합지반에서 TBM 굴진 진동을 고려한 지표침하에 대한 수치모델링)

  • Kwak, Chang-Won;Park, Inn-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.3
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    • pp.333-339
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    • 2015
  • In this paper, the surface settlement resulted from the shallow TBM tunnelling has been numerically simulated. TBM tunnelling is especially used in urban area to avoid serious vibration and noise caused by explosion in NATM. Surface settlement is one of the most important problems encountered in all tunnelling and critical in urban areas. In this study, face vibration of TBM excavation is considered to estimate surface settlement trend according to TBM extrusion. The dynamic excavation forces are calculated by total torque on the TBM cutterhead in mixed-face of soil and weathered rock condition with shallow depth. A 3-dimensional FDM code is employed to simulate TBM tunnelling and mechanical-dynamic coupling analysis is performed. The 3D numerical analysis results showed that dynamic settlement histories and trend of surface settlement successfully. The maximum settlement occurred at the excavation point located at 2.5D behind the face, and the effect of face vibration on the surface settlement was verified in this study.

Evaluation of Foundation Settlement of Gyungbu High Speed Concrete Track Under Construction (건설 중인 경부고속철도 콘크리트궤도 기초침하 평가)

  • Kim, Dae-Sang;Yoo, Chung-Hyun;Kim, Hwan-Ki
    • Proceedings of the KSR Conference
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    • pp.365-370
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    • 2007
  • Foundation settlements(settlements at the embankment surface and ground) has been evaluating to satisfy the strict allowable residual settlement level from the start of the construction of Gyungbu high speed railway. This is because both embankment and ground settlement could be important to minimize the residual settlement after the construction of concrete track. Ground settlement is caused by the increase of effective stress resulting from embankment. The causes of embankment settlement could be come from different sources, for example, the increase of effective stress, rainfall, creep behaviors. Based on the field measured data, this paper analysed the settlement of ground and embankment settlement. The biggest settlement at the embankment surface was 9.7mm during 246days at the STA 000k922.5. The calculated settlement of embankment itself was 8.6mm at the same places. These results conclude that the compressive settlement of embankment could not negligible.

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Analysis of Peripheral Surface Settlement during Subway Excavation (지하철 굴착공사에 따른 인접지반의 침하 해석)

  • 문준석;권강오;김홍석;장연수
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.621-628
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    • 2000
  • In this study, the influence of groundwater variation and surface settlement adjacent to the excavation site of subway station on $\bigcirc$$\bigcirc$ Gas station and the $\bigcirc$$\bigcirc$ building is analized. Measurement data of surface settlement, horizontal deformation and groundwater level are used to verify the results of Caspe analytical method and FLAC numerical analysis. Variation of groundwater level adjacent to the excavation site is modelled by the 3-D groundwater flow program, MODFLOW. The results of both the analytical method and the numerical method were quite close to the measurement data of surface settlement.

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A simple model for ground surface settlement induced by braced excavation subjected to a significant groundwater drawdown

  • Zhang, Runhong;Zhang, Wengang;Goh, A.T.C.;Hou, Zhongjie;Wang, Wei
    • Geomechanics and Engineering
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    • v.16 no.6
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    • pp.635-642
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    • 2018
  • Braced excavation systems are commonly required to ensure stability in construction of basements for shopping malls, underground transportation and other habitation facilities. For excavations in deposits of soft clays or residual soils, stiff retaining wall systems such as diaphragm walls are commonly adopted to restrain the ground movements and wall deflections in order to prevent damage to surrounding buildings and utilities. The ground surface settlement behind the excavation is closely associated with the magnitude of basal heave and the wall deflections and is also greatly influenced by the possible groundwater drawdown caused by potential wall leakage, flow from beneath the wall, flow from perched water and along the wall interface or poor panel connections due to the less satisfactory quality. This paper numerically investigates the influences of excavation geometries, the system stiffness, the soil properties and the groundwater drawdown on ground surface settlement and develops a simplified maximum surface settlement Logarithm Regression model for the maximum ground surface settlement estimation. The settlements estimated by this model compare favorably with a number of published and instrumented records.