Vibro Replacement Stone Columns Research Articles

Study on slope stability and reinforcement measures of an earth-rock cofferdam on deep overburden foundation

Slope stability and reinforcement measures of an earth-rock cofferdam on deep overburden foundation are studied in the paper. Slope stability is analysed by using FEM strength reduction method, considering seepage, based on ABAQUS. Two different reinforcement measures are taken: vibro-replacement stone columns and concrete anti-sliding piles. As a result of the research, conclusions are made: overflow happens on the slope near bottom of the foundation pit in layer Qal-1, where permeability coefficient is quite large compared to that of other layers; Both the vibro-replacement stone columns and concrete anti-sliding piles increase the stability; Vibro-replacement stone columns should be used as the final reinforcement measure, since vibro-replacement stone columns can be constructed before the foundation pit excavation and they can also conduce to drainage in foundation pit. This deep overburden foundation is characterized by complex geological conditions and poor mechanical properties. Therefore, the successful construction of the project has a certain reference and application value.

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

Creep improvement factors for vibro-replacement design

Although the vibro-replacement stone column technique is being deployed increasingly in soft cohesive soil deposits in which creep settlements may be significant/dominant, the majority of existing stone column settlement design methods are either non-specific or pertain to primary settlement only. Consequently, in the absence of further guidance, designers sometimes apply the same settlement improvement factor to creep settlements that they have estimated for primary settlements. In this paper, Plaxis 2D finite-element analyses carried out in conjunction with the elasto-viscoplastic soft soil creep model have indicated that settlement improvement factors are lower when creep is considered and therefore the design of stone columns ignoring creep is unconservative. These analyses were used to establish the impact of a range of relevant variables on ‘primary’, ‘total’ and ‘creep’ settlement improvement factors, leading to the development of a simplified empirical approach for predicting creep settlement improvement factors for use in conjunction with an existing primary settlement design method.

Vibro-Replacement Stone Column Treating Silty Sand Soil Subgrade

To improve the wet soft silty sand bearing capacity, vibro-replacement stone column was used. Compared with the practical construction, this paper introduces the vibro-replacement stone column strengthening soft foundation. The principle of the construction, quality control, and inspection technology were discussed. Based on Drucker - Prager elastic-plastic model, different high wet soft foundation was simulated with the numerical analysis software. Results show that vibro-replacement stone column can significantly reduce the roadbed horizontal displacement. The displacement of the subgrade reinforced by stone columns decreases respectively 0.1, 0.2, 0.6, 2.3 cm than the other. If the subgrade is 4 m in height, the displacement reaches 0.2, 0.5, 0.7 cm when the length of stone column is 5, 10, 15m, respectively. To sum up, five - metre long pile is more economic and reasonable.

Study on Composite Model for Vibro-Replacement Stone Column Foundation by Finite Element Method

On the base of studying on mechanism of the deformation and bearing capacity of vibro-replacement stone column foundation thoroughly, the assumptive conditions are presented. The composite 2-dimension numerical model of the stone column is established, this model considers the couple of stress-strain with Biot consolidation and the reinforced efficiently, the finite element analysis program is developed according to this model. The reliability and validity of APOSE is verified by a simple example. The results show that APOSE can be applied to analyze the consolidation and subsiding for vibro-replacement stone column, etc

Ground Improvement by Deep Vibratory Methods

1. Ground Improvement Methods 2. History of Vibratory Deep Compaction 3. Deep Soil Improvement by Vibratory Methods 4. Compaction of Granular Soils 5. Improvement of Fine Grained and Cohesive Soils by Vibro Replacement Stone Columns 6. Method Variations and Related Processes 7. Environmental Considerations 8. Contractual Implications

Numerical model verification and calibration of George Massey Tunnel using centrifuge models

Dynamic soil–structure interaction analyses were carried out for the seismic retrofit design of the immersed George Massey Tunnel, both to predict and study soil liquefaction and related tunnel movements and to design ground improvement. The proposed ground improvement included ground densification using vibroreplacement stone columns along both sides of the tunnel and seismic gravel drains adjacent to the outer edge of the densified zones. The den sification and drainage were proposed to locally mitigate soil liquefaction and reduce displacements of the tunnel to tolerable levels. Centrifuge model tests with base shaking to simulate earthquake effects were conducted to verify and calibrate the numerical models. This included simulating the effects of ground densification and drainage on reme diating tunnel movements. This paper presents the principal results from the dynamic analyses, the centrifuge model design and testing procedure, the class A predictions of the centrifuge tests, and discussions of the centrifuge test results and numerical model calibrations.Key words: immersed tunnel, seismic retrofit, soil liquefaction, design verification, centrifuge testing, numerical calibration.

Shear-Wave Velocity to Determine Vertical Stress Share on Column-Sand Samples

Abstract The increased rigidity of vibro-replacement stone columns in liquefiable soils offers the potential for liquefaction mitigation. This paper proposes a laboratory method to facilitate an investigation of this parameter. Shear-wave velocity data are used to obtain the vertical load distribution between loose sand and gravel column in composite columnar triaxial samples under static and cyclic loading. Significant reductions in cyclic stresses applied to the loose sand are obtained, offering the potential for the optimization of the design of vibro-systems to include load share benefits.

New A557, Widnes—alternative embankment foundations

The new 1·8 km long A557 Widnes eastern bypass (southern section) is the last link in a length of continuous dual carriageway between the M62 motorway and the Runcorn bridge over the River Mersey. The area through which the route passes is flat and has been occupied by industrial development since the middle of the nineteenth century. Most of this new length of road is on embankments up to 8 m high over soft and contaminated ground. This paper is a case history of a project which, in respect of earthworks, was constructed adopting an alternative design proposed by the contractor. By using vibro-replacement stone columns, driven precast concrete piles and an alternative pavement foundation, this avoided the need to excavate, and remove to licensed tips, a large volume of soft and contaminated material. This alternative approach resulted in a reduced cost to the Highways Agency compared with the conforming design and produced a solution with equivalent or better performance. The construction of this alternative was completed several months ahead of programme. Several other alternatives also proposed by the contractor further minimized the environmental impact of the construction works. The paper addresses the development of the alternative scheme from conceptual design through to completion. It examines the ways in which the environmental impact of the project was minimized, and the successful management methods adopted by the contractor to minimize the unforeseen risks. The benefits that can be secured by clients in permitting alternative tenders and a cooperative approach, by all parties, are also be considered.

Liquefaction Failure and Remediation: King Harbor Redondo Beach, California

Liquefaction failure, including large lateral displacements and associated settlement, severely damaged marina facilities at Redondo Beach King Harbor during the Northridge Earthquake of January 17, 1994. Although minor ground deformation apparently occurred in several areas of the harbor, severe damage was restricted to the central portion of mole B, one of four offshore fills constructed as a part of marina improvements in 1960–61. Local ground conditions and methods used to remediate liquefaction are presented and discussed. Two ground modification techniques were used to mitigate the liquefaction potential of the reconstructed mole b facilities. The major portion of the failure area was treated with vibroreplacement stone columns. Vibratory displacement and installation of the gravel columns not only densified the foundation soils, but also provide additional strength and drainage capacity. Compaction grouting was used to densify foundation soils in the vicinity of existing improvements that were considered sensitive to construction-induced ground vibrations. These ground improvement techniques effectively reduced the liquefaction potential and allowed the marina improvements to be reconstructed on shallow foundations similar to the original design.