Top-down Excavation of a Metro Station in Soft Clay

2011 ◽  
Vol 368-373 ◽  
pp. 2866-2869
Author(s):  
Ye Lu ◽  
Yong Tan
Keyword(s):  
Soft Clay ◽  
Field Measurements ◽  
Top Down ◽  
Metro Station ◽  
Vertical Movements ◽  
Steel Columns ◽  
Axial Forces ◽  
Clay Deposits ◽  
Diaphragm Walls

This study examines the performance of a deep metro excavation constructed by top-down technique in Shanghai clay deposits. The monitoring items included deflections of diaphragm walls, vertical movements of steel columns, and axial forces of the struts. Based on analysis of the field measurements, some interesting findings were obtained, which will be useful for both practitioners and researchers.

Measured performance of a 26 m deep top-down excavation in downtown Shanghai

2011 ◽  
Vol 48 (5) ◽  
pp. 704-719 ◽  
Author(s):  
Yong Tan ◽  
Mingwen Li
Keyword(s):  
Soil Removal ◽  
Top Down ◽  
Metro Station ◽  
Steel Columns ◽  
Axial Forces ◽  
Floor Slabs ◽  
Earth Pressures ◽  
Diaphragm Walls ◽  
Lower Depth

Via a long-term comprehensive instrumentation program, the performance of a 26 m deep metro station excavation constructed by the top-down method in downtown Shanghai was extensively examined. The measured excavation responses included diaphragm wall deflections, wall settlements, ground settlements, uplifts of interior steel columns, axial forces of propping struts, groundwater table levels, and settlements of adjacent buildings and utility pipelines. Based on the analyses of field data, the following major findings were obtained: (i) the concrete struts along with the floor slabs effectively suppressed later wall movements and consequently reduced the chance that the maximum wall deflections would occur above the excavation surfaces, (ii) with the progress of excavation to a lower depth, the diaphragm walls underwent a serrated settlement pattern over time, (iii) no significant post-excavation wall deflection occurred, (iv) the relationship between the interior column uplifts and the maximum wall deflections can be described by a linear equation, and (v) most system loads due to soil removal were carried by the concrete struts along with the floor slabs. The struts sustained mainly the released earth pressures due to the exposure of the adjacent portions of diaphragm walls, and the soil removal distant from the struts imposed limited effects on the strut axial forces.

scholarly journals Penggunaan Dinding Silang Pada Galian Dalam Di Tanah Sangat Lunak: Studi Kasus Proyek Apartemen DI Jalan Kebun Sirih Jakarta

2020 ◽  
Vol 4 (2) ◽  
pp. 257
Author(s):  
Oktaffian Widjaja ◽  
Chaidir Anwar Makarim
Keyword(s):  
Retaining Wall ◽  
Soft Soil ◽  
Soft Clay ◽  
Good Choice ◽  
Cross Wall ◽  
Deep Excavation ◽  
Top Down ◽  
Adjacent Buildings ◽  
Clay Deposits ◽  
Lateral Resistance

Deep excavation in areas with very soft clay deposits need a good soil retaining system and excavation method. Using a diapraghm wall as a soil retaining system for deep excavation is a good choice can be done. Diapraghm wall is expected to limit the movement that occurs in the retaining walls and avoid leaks that occur in walls, this is needed to minimize damage to adjacent buildings. The top down excavation method by utilizing the basement floor as lateral resistance can be carried out to reduce the movement that occurs on the ground. In very soft soil areas with excavation distances to neighbors very close, the movement on the ground must be limited to minimize damage to adjacent buildings. Cross walls can be used to reduce the movement that occurs on the ground. Analysis of finite element with using the Plaxis program was carried out to investigate the performance of the retaining wall. From the results of the analysis conducted shows that using a cross wall at a location below the raft pile can be reduced the movement that occurs in the retaining wall and the excavation stages can be reduced. Keywords: cross wall; deep excavation; diapraghm wall; very soft soil ABSTRAKGalian dalam pada daerah dengan endapan tanah liat sangat lunak yang cukup dalam diperlukan sistem penahan tanah dan metode galian yang direncanakan dengan baik. Menggunakan dinding dipraghm sebagai sistem penahan tanah untuk galian dalam merupakan pilihan yang dapat dilakukan. Penggunaan dinding diapraghm diharapkan dapat membatasi pergerakan yang terjadi pada dinding dan menghindari kebocoran yang yang terjadi pada dinding penahan tanah karena sistem pengecoran yang saling mengunci dan pertemuan antara panel dinding dapat dipasang waterstop, hal ini diperlukan untuk menghindari kerusakan pada bangunan yang berdekatan dengan daerah galian. Metode galian top down yaitu galian bertahap dengan memanfaatkan lantai besmen sebagai tahanan lateral dapat dilakukan untuk mengurangi pergerakan yang terjadi pada tanah. Pada daerah tanah sangat lunak dengan jarak galian dengan tetangga sangat berdekatan pergerakan pada tanah harus dibatasi untuk meminimalkan kerusakan pada bangunan yang berdekatan. Dinding silang merupakan sistem tahanan lateral yang dapat dipergunakan untuk mengurangi pergerakan yang terjadi pada tanah. Analisis elemen hingga menggunakan program Plaxis 2D dilakukan untuk mengetahui kinerja dinding penahan tanah dan pergerakan yang terjadi. Dari hasil analisis yang dilakukan diperoleh hasil bahwa dengan menggunakan dinding silang yang terletak pada di bawah raft pile dapat menurunkan pergerakan yang terjadi pada dinding penahan tanah dan tahapan galian dapat dikurangi. 

scholarly journals Large scaled field tests on soft Bangkok clay

2021 ◽  
Vol 44 (4) ◽  
pp. 1-23
Author(s):  
Arumugam Balasubramaniam
Keyword(s):  
Ground Improvement ◽  
Large Diameter ◽  
Soft Clay ◽  
Field Tests ◽  
Field Measurements ◽  
Deformation Analysis ◽  
Residual Soil ◽  
Kuala Lumpur ◽  
Vertical Drains ◽  
Clay Deposits

In this lecture the interpretations of fully instrumented tests embankments and their role in the development of appropriate ground improvement techniques for highways, motorways and airfields on soft clay deposits is illustrated through well documented case studies in Bangkok, Thailand and Muar Flat Site in Kuala Lumpur. For the Bangkok Plain and with sand backfills the performance of embankments with different schemes of vertical drains was evaluated over a period of 25 years. Aspects such as recharging effects due to the drains, inadequate measures in maintaining vacuum during vacuum applications and possible hydraulic connections with large diameter drains are discussed. For the Muar test embankments, the role of fill strength in residual soil embankment and the field deformation analysis in separating consolidation settlement from immediate settlement and creep settlements is presented. Novel interpretations of settlement from pore pressure dissipations, secondary settlement from field measurements and decay of lateral deformation rate with time were also made.

scholarly journals Prefabricated vertical drains (PVDs) in soft Bangkok clay: a case study of the new Bangkok International Airport project

2002 ◽  
Vol 39 (2) ◽  
pp. 304-315 ◽  
Author(s):  
Dennes T Bergado ◽  
A S Balasubramaniam ◽  
R Jonathan Fannin ◽  
Robert D Holtz
Keyword(s):  
Soft Clay ◽  
Field Measurements ◽  
Full Scale ◽  
Maximum Height ◽  
Vertical Movements ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
International Airport ◽  
Prefabricated Vertical Drain ◽  
Test Embankment

This paper presents the performance of a full-scale test embankment constructed on soft Bangkok clay with prefabricated vertical drains (PVDs) at the site of the new Bangkok International Airport in Thailand. The embankment was square in plan with a maximum height of 4.2 m, 3H:1V side slopes, and base dimensions of 40 m by 40 m. The piezometric level with depth is characterized by negative drawdown starting at around 8-10 m depth caused by excessive withdrawal of groundwater. Instrumentation was provided to monitor both horizontal and vertical movements of the test embankment. The measured increases in undrained shear strengths with depth are in agreement with the values calculated from the SHANSEP technique. The secondary compression ratio, Cα, was 0.018, or within the normal values for marine clays. The coefficient of horizontal consolidation measured in the field, Ch(field), was higher for soil at 4 and 10 m depths than for the weakest soil at 6 m depth. The back-calculated Ch(field) values range from 3 to 8 m2/year, and the ratio of Ch(field) to Ch(lab) ranges from 4 to 5, where Ch(lab) is the coefficient of horizontal consolidation measured in the laboratory. The degree of consolidation estimated from the pore-pressure dissipation measurements agreed with those obtained from settlement measurements. The water-content reductions from field measurements were also in good agreement with the values computed from the consolidation settlements. The full-scale study confirmed that the magnitudes of consolidation settlements increased with the corresponding decrease of PVD spacing at a particular time period. Lastly, the results of the full-scale study have proven the effectiveness of PVDs for the improvement of soft Bangkok clay.Key words: soft clay, consolidation, prefabricated vertical drain, preloading, test embankment.

scholarly journals The Performance of Tied-Back Sheet Piling in Clay

1972 ◽  
Vol 9 (2) ◽  
pp. 206-218 ◽  
Author(s):  
G. C. McRostie ◽  
K. N. Burn ◽  
R. J. Mitchell
Keyword(s):  
Field Measurements ◽  
Triaxial Tests ◽  
Deep Excavation ◽  
Sheet Pile ◽  
Vertical Movements ◽  
Field Situation ◽  
Stress Changes ◽  
Temporary Support ◽  
Current Design ◽  
Horizontal Displacements

In Ottawa in 1969 a tied-back sheet pile wall was installed to provide temporary support in one side of a 12 m deep excavation through Champlain Sea deposits to shale bedrock. The wall was designed to permit as little yield as possible in order to safeguard the vital operation of an adjacent transformer building.To assess the performance of this structure, measurements of vertical movements of the surface adjacent to the wall, horizontal displacements of the wall, tendon loads and ground-water pressures were made as the excavation progressed.A series of triaxial tests was carried out in the laboratory to determine the form and magnitude of soil deformations under stress changes approximating those derived from the field measurements. Reasonable correlation is obtained when the results of these tests are used to estimate soil displacements in the field situation. The measured tendon loads are compared with those that would be expected using current design methods.

Ormen Lange Gas Field, Immediate Settlement of Offshore Rock Supports

2007 ◽  
Author(s):  
Guus de Vries ◽  
Joop van der Meer ◽  
Harald Brennodden ◽  
Stein Wendel
Keyword(s):  
Continental Shelf ◽  
Soft Clay ◽  
Back Analysis ◽  
Processing Plant ◽  
Gas Field ◽  
Clay Deposits ◽  
Calculation Results ◽  
The Uk ◽  
Rock Supports ◽  
Norwegian Continental Shelf

Located approximately 120 km offshore, Ormen Lange, with an estimated 400 billion m3 of natural gas, is the second-largest gas discovery on the Norwegian shelf. The water depth is up to 850 meters, making Ormen Lange the first deepwater project on the Norwegian Continental Shelf. The development of Ormen Lange is under shared operatorship between Norsk Hydro and Shell. Ormen Lange’s untreated well stream will be transported to shore in two 120 km long, 30-inch diameter pipelines to a processing plant at Nyhamna, Norway. From there, gas will be exported via a 42” 1200 km sub sea pipeline (Langeled) to Easington at the east coast of the UK. The pipelines have to pass over the Storegga slide edge which rises 200–300 meters toward the continental shelf in very steep slopes, which are also encountered in the nearshore Bjo¨rnsundet area. The uneven and steep seabed conditions require the use of approximately 2.8 million tons of rock to support and stabilize the pipelines. The sea bottom conditions on the Norwegian continental shelf are characterized by many outcrops as well as very soft clay deposits. The immediate settlement of the rock supports during installation form a significant amount of the total required rock volume. In this paper a procedure is presented on how to assess these immediate settlements recognizing four contributing components all being discussed separately. The calculation results are compared to a back-analysis, performed during the execution of the Ormen Lange rockworks, proving the suitability of the calculation method.

scholarly journals Prediction of spudcan penetration resistance profile in stiff-over-soft clays

2016 ◽  
Vol 53 (12) ◽  
pp. 1978-1990 ◽  
Author(s):  
J. Zheng ◽  
M.S. Hossain ◽  
D. Wang
Keyword(s):  
Bearing Capacity ◽  
Soft Clay ◽  
Bottom Layer ◽  
Design Approach ◽  
Rate Dependency ◽  
Soft Clays ◽  
Perfectly Plastic ◽  
Clay Deposits ◽  
Additional Resistance ◽  
Elastic Perfectly Plastic

Spudcan punch-through during installation and preloading process is one of the key concerns for the jack-up industry. This incident occurs in layered deposits, with new design approaches for spudcan penetration in sand-over-clay deposits reported recently. This paper reports a novel design approach for spudcan penetration in stiff-over-soft clay deposits. Large-deformation finite element (LDFE) analyses were carried out using the Coupled Eulerian–Lagrangian (CEL) approach. The clay was modelled using the extended elastic – perfectly plastic Tresca soil model allowing strain softening and rate dependency of the undrained shear strength. A detailed parametric study was undertaken, varying the strength ratio between bottom and top soil layers, the thickness of the top layer relative to the spudcan diameter, and degree of nonhomogeneity of the bottom layer. Existing data from centrifuge model tests were first used to validate the LDFE results, and then the measured and computed datasets were used to develop the formulas in the proposed design approach. The approach accounts for the soil plug in the bottom layer, and the corresponding additional resistance. Where there is the potential for punch-through, the approach provides estimations of the depth and bearing capacity at punch-through, the bearing capacity at the stiff–soft layer interface, and the bearing capacity in the bottom layer. Comparison shows that the punch-through method suggested in ISO standard 19905-1 provides a conservative estimate of the bearing capacity at punch-through, with guidelines provided to improve the method.

Effect of pile driving on adjacent piles in clay

1994 ◽  
Vol 31 (6) ◽  
pp. 856-867 ◽  
Author(s):  
H.G. Poulos
Keyword(s):  
Structural Damage ◽  
Tensile Failure ◽  
Pile Driving ◽  
Bending Moments ◽  
Depth Of Penetration ◽  
Vertical Movements ◽  
Concrete Piles ◽  
Axial Forces ◽  
Model Pile ◽  
Soil Movements

When a pile is driven into clay, horizontal and vertical movements are developed in the soil surrounding the pile. These movements will tend to develop axial forces and bending moments in adjacent piles that have already been installed. Possible consequences for these piles are (i) structural damage or cracking (of concrete piles) arising from the induced bending moments, (ii) tensile failure of the piles due to the induced axial forces, and (iii) lifting-off of the pile tip from the bearing stratum due to the axial induced movements. This paper describes the results of a theoretical analysis of the bending moments and axial forces developed in a pile due to driving of an adjacent pile in clay. The analysis uses approximate distributions of horizontal and vertical soil movements caused by pile driving, developed from a "strain-path" analysis, together with inferences from model pile test data. An examination is made of various factors that may influence the induced bending moments and forces, including pile spacing, depth of penetration of the adjacent pile, and number of piles driven. For a number of published case histories comparisons are made between theoretical and measured axial and lateral pile movements. In general, satisfactory agreement is found. Key words : foundations, lateral movements, pile driving, settlement, soil displacement.

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