Quality Control Indexes Study of Vacuum Combined with Fill Surcharge Preloading Method

2012 ◽  
Vol 209-211 ◽  
pp. 1459-1462
Author(s):  
Shang Yu Han ◽  
Li Hong
Keyword(s):  
Vacuum Pressure ◽  
Soil Consolidation ◽  
Vertical Load ◽  
Foundation Soil ◽  
Load Pressure ◽  
Surcharge Preloading ◽  
Soil Settlement ◽  
Consolidation Effect ◽  
Preloading Method

The consolidation effect of vacuum combined with fill surcharge preloading always influenced by many factors including vacuum pressure, vertical load pressure and vertical drainage depth. As the way to improve the reliability of the method, based on the soil consolidation mechanisms and actual data getting from the laboratory test and in-situ test, the main indexes of the method were studied in this paper. The test results show that the ratio of the vacuum pressure and vertical load pressure can cause difference soil settlement-deformation, if the ratio close to 1 the consolidation effect of the foundation can be gradually advanced. The soil outside the embankment always has displacement to reinforcement region in the upper depth of the foundation soil when the vacuum pressure equals to the vertical load pressure.

Soil improvement for a storage yard using the combined vacuum and fill preloading method

2005 ◽  
Vol 42 (4) ◽  
pp. 1094-1104 ◽  
Author(s):  
S.-W Yan ◽  
J Chu
Keyword(s):  
Ground Improvement ◽  
Soil Improvement ◽  
Undrained Shear Strength ◽  
Foundation Soil ◽  
Surcharge Preloading ◽  
Clay Slurry ◽  
Degree Of Consolidation ◽  
Preloading Method ◽  
Undrained Shear

This paper presents a case study of using the combined vacuum and fill surcharge preloading method to improve the foundation soil for a storage yard at Tianjin Port, China. A vacuum load of 80 kPa was applied for 4-8 weeks before fill surcharge was added in stages. The site to be improved was recently reclaimed using dredged clay slurry. Both the consolidated clay slurry fill and the seabed soils were very soft. After the combined vacuum and fill surcharge preloading, the ground settled more than 1 m. The average degree of consolidation achieved was more than 80%. The undrained shear strength of the soil increased twofold. The water content of the soil also decreased substantially. The soil improvement procedure using the combined vacuum and fill surcharge preloading method and the instrumentation scheme are described, the field monitoring data are presented and analyzed, and methods to estimate the degree of consolidation and several other issues related to the combined preloading method are discussed.Key words: case history, consolidation, ground improvement.

scholarly journals Analysis of the Effectiveness of the Step Vacuum Preloading Method: A Case Study on High Clay Content Dredger Fill in Tianjin, China

2020 ◽  
Vol 8 (1) ◽  
pp. 38 ◽  
Author(s):  
Jinfeng Li ◽  
Huie Chen ◽  
Xiaoqing Yuan ◽  
Wenchong Shan
Keyword(s):  
Fine Particles ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clay Content ◽  
Vacuum Pressure ◽  
Vacuum Preloading ◽  
Drainage Pipe ◽  
Consolidation Effect ◽  
Dredger Fill ◽  
Preloading Method

As a solution to avoid the blockage of the drainage pipe by traditional vacuum preloading, step vacuum preloading (SVP) has been progressively studied. However, the effectiveness of this technique has yet to be systematically analyzed. In this study, an indoor model test was conducted in which vacuum pressure was applied in five stages (10, 20, 40, 60, and 80 kPa) to dredger soil with high clay content at a reclamation site in Binhai New Area, Tianjin, China. The extent of the consolidation effect of the soil was determined, and the effectiveness of the step vacuum preloading method to address drainage pipe blockage was evaluated. The results indicate that soil settlement increases at each stage of vacuum pressure treatment and the degree of vertical consolidation at each stage exceeds 90%. At the end of the treatment stage with vacuum pressure of 80 kPa, the weakly bound water was discharged. Dissipation of pore water pressure occurred in all stages. On the basis of these results, it is shown that SVP can efficiently reinforce dredger fill. Moreover, after SVP, the grain size of the soil and void ratio are still uniformly distributed. Regardless of their location from the drainage pipe, soil exhibits permeability coefficients within the same order of magnitude. The consolidation effect of soil in each stage and the increased drainage rate in the initial stage of vacuum preloading with 80 kPa indicate that the test in the current study can decrease the horizontal displacement of fine particles and can avoid drainage pipe blockage.

Evaluation on Features of Soft Foundation Engineering and Bearing Layer of Pile in Jiaxing City

2011 ◽  
Vol 90-93 ◽  
pp. 217-221
Author(s):  
Jin Long Zhou ◽  
Qiao Li ◽  
Wei Zhong Cai
Keyword(s):  
Soil Mass ◽  
Shallow Foundation ◽  
Silty Clay ◽  
Foundation Engineering ◽  
Foundation Soil ◽  
Cone Tip Resistance ◽  
Soft Foundation ◽  
Tip Resistance ◽  
Bearing Layer

Through the investigation into composition of major shallow foundation soil mass and the correlation of mechanical indicators in this study, the regression equation of mechanical indicators of the features of local foundation soil mass and the data of in situ testing was obtained. Based on massive quantities of exploration materials, this study analyzed engineering features, distribution status, and the feasibility of silty clay to be used as the bearing layer of the pile in Layer ④2 . The analytical results showed that the silty clay with the uniform depth of over 3.5m and the cone tip resistance in static sounding of over 400MPa could be used as bearing layer of the pile. This study could provide the reference for the accurate understanding of the engineering features of soil mass, and the design and evaluation of foundation in Jiaxing City.

scholarly journals Discussion on Reinforcement Mechanism and Construction Technology of Pressurized Vacuum Preloading

2019 ◽  
Vol 136 ◽  
pp. 01036
Author(s):  
ZHUGE Ai-jun
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Field Tests ◽  
Good Effect ◽  
Construction Technology ◽  
Soil Consolidation ◽  
Vacuum Preloading ◽  
Pressure Transmission ◽  
Soil Settlement ◽  
Sand Cushion

Based on the basic theory of vacuum preloading, this paper proposes an good effect of pressurized vacuum preloading in which the high pressure gas results in tiny cracks between the air pressurized pipe and band drain. Therefore additional drainage paths are introduced to improve the permeability of soil and accelerate soil consolidation. But field tests show that the advantages of pressurized vacuum preloading are not obvious compared with conventional vacuum preloading, and the soil settlement, soil properties and vane shear strength are slightly lower than those by conventional vacuum preloading. The vacuum pressure transmission is analysed in the air pressurized pipe and band drain as well as the dissipation of pore water pressure in the soil during the pressurization process, it is concluded that the unsatisfactory reinforcement effect is mainly due to the sealing problem between the top of the air pressurized pipe and the sand cushion, and the overlap problem between the booster pipe and band drain.

3D Simulation of Tunnel Collapse Consolidation and In Situ Monitoring Analysis

2011 ◽  
Vol 243-249 ◽  
pp. 3551-3555
Author(s):  
Zhi Min Chen ◽  
De An Zhao
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
In Situ Monitoring ◽  
3D Simulation ◽  
Actual Situation ◽  
Consolidation Effect ◽  
Tunnel Collapse ◽  
Simulation Results ◽  
Shallow Buried Tunnel

A shallow buried tunnel was collapsed during construction. According to the actual situation of the tunnel, different collapse consolidation schemes were put forward and corresponding three-dimensional finite difference numerical models were established and analyzed using FLAC3D software. Base on the 3D Simulation results, a collapse consolidation scheme was determined and constructed. The in-situ monitoring results of vault subsidence and convergence displacement were consistent approximately with the 3D Simulation results. The in-situ measured results were in line with the specification’s allowance and show that the consolidation effect of reinforced concrete casing arch and ahead grouting method is good. This could be referenced for similar engineering.

Application of In Situ Direct Shear Test for Obtaining Soil Shear Strength Indexes in Projects

2013 ◽  
Vol 788 ◽  
pp. 615-618
Author(s):  
Yu Jun Lu ◽  
Xin Sheng Ge
Keyword(s):  
Shear Strength ◽  
Direct Shear Test ◽  
Shear Test ◽  
Soil Condition ◽  
Direct Shear ◽  
Foundation Pit ◽  
Foundation Soil ◽  
Material Resources ◽  
Building Foundation

In order to provide precise shear strength indexes for a building foundation pit supporting project, the second layer and the third layer of foundation soil were in-situ direct shear test. In-situ direct shear test has its own advantages in projects, and it simulates the real soil condition and reflects practical shear strength. But in-situ shear test requires lots of manpower, material resources and financial resources, so it is not convenient to carry out a lot in practical projects.

scholarly journals Consideration of soil strata heterogeneity influence on differential foundation settlements of overpasses for high-speed railways

2019 ◽  
Vol 265 ◽  
pp. 02003 ◽  
Author(s):  
Sergei Kudryavtsev ◽  
Vladimir Ulitskii ◽  
Sergei Alekseev ◽  
Stanislav Kondrat'ev
Keyword(s):  
Calculation Method ◽  
High Speed ◽  
Shallow Foundations ◽  
Foundation Soil ◽  
Ballastless Track ◽  
Soil Settlement ◽  
Design Solutions

The implementation of projects for the construction of high-speed railways actualizes the search of effective approaches to accounting the influence of soil strata heterogeneity along the course of the track on differential foundation settlements of overpasses. Russian special technical conditions prescribe sufficiently stringent regulation limits of absolute values of overpasses' foundation soil settlements (20 mm for ballastless track) and angles of break in profile (the differential foundation soil settlement), which should not exceed 1 ‰ for ballastless track. These requirements make it necessary to develop the calculation method, which is based on the criterion of deformation. To ensure compliance of design solutions to the specified regulations it is appropriate to use the method of the predefined equated soil settlements for design of shallow foundations of overpasses for high-speed railways. Several features of application of this method are presented in this article.

On Ground Settlement Rate Approach of Preloading Method

2013 ◽  
Vol 353-356 ◽  
pp. 258-264
Author(s):  
Ming Lei Shi ◽  
Rui Kun Zhang ◽  
Hao Zhang
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Settlement ◽  
Settlement Rate ◽  
Excess Pore Water Pressure ◽  
Surcharge Preloading ◽  
The Relationship ◽  
Preloading Method ◽  
Linear Compressibility ◽  
Excess Pore

Based on the theory of the Terzaghi 1-D consolidation and the linear compressibility of soil, a rational method for regionalization of recompression and compression in the distribution of the excess pore-water pressure under overloading-unloading was presented. A simple generalized expression of the ground settlement rate applied to insufficient-load preloading, equal-load preloading, surcharge preloading and a time expression of insufficient-load preloading, surcharge preloading relative to equal-load preloading were further derived. The relationship mechanism of settlement rate and time of insufficient-load preloading, surcharge preloading relative to equal-load preloading are discussed based on the same allowed post-construction settlement.

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