scholarly journals Laboratory Model Tests on Consolidation Performance of Soil Column with Drained-Timber Rod

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
X. J. Chai ◽  
K. Deng ◽  
C. F. He ◽  
Y. F. Xiong
Keyword(s):  
Precast Concrete ◽  
Ground Improvement ◽  
Soft Soil ◽  
Soil Column ◽  
Water Discharge ◽  
Soft Clay ◽  
Economic Benefits ◽  
Laboratory Model ◽  
Engineering Practice ◽  
Timber Piles

Timber pile is an ancient technology applied in soft ground improvement for more than 1000 years. With the rise of many high-rise buildings, many types of modern mechanized-construction piles are widely developed and applied; for example, steel pile, precast concrete pile, sand pile, and gravel pile are widely used instead of timber piles. Yet, in some special conditions, timber piles have certain advantages due to their environment-friendly characteristics, which result in obvious economic benefits and suitability. To overcome the weakness of the traditional timber pile technology and expand its application in engineering practice, a drained-timber pile technique was put forward. This technology is to wrap the permeable filter-type drainage geotextile around the timber pile, so that the timber pile not only has the replacement function to strengthen the foundation but also has the drainage function, can accelerate the pore water discharge, and speeds up the soft soil foundation consolidation. The reduced scale soil-column consolidation model was designed to perform the consolidation tests for the soil column with a drained-timber rod. In total, eight types of soil-column consolidation tests were carried out to verify the feasibility and effectiveness of the drained-timber pile technique. The results revealed that, under the same loading and consolidation time, the drained-timber rod can obviously increase the degree of consolidation when compared with traditional timber rod. It can be expected that the drained-timber pile technique has a good application prospect for the construction of medium-small hydraulic structures and for the treatment of super soft clay.

On the Construction Technology and Quality Control of Vacuum Combined Surcharge to Foundation Reinforcement

2014 ◽  
Vol 1030-1032 ◽  
pp. 827-829 ◽  
Author(s):  
Ze Jun Liu ◽  
Ya Guo ◽  
Qi Wang Yuan ◽  
Bao Hai Chen ◽  
Xiang Yang Gu ◽  
...  
Keyword(s):  
Soft Soil ◽  
Soft Clay ◽  
Engineering Application ◽  
Economic Benefits ◽  
Engineering Practice ◽  
Strengthening Effect ◽  
Construction Technology ◽  
Soil Consolidation ◽  
Vacuum Preloading ◽  
Soft Clay Subgrade

The vast area of distribution of soft clay with poor engineering property of our country, on the soft clay subgrade treatment by drainage consolidation method. As a kind of drainage consolidation method, vacuum preloading consolidation of soft soil foundation in recent years have been widely used, and achieved very good engineering and economic benefits. The theory research about vacuum preloading behind the engineering practice, restricted the further development of the technology and engineering application, it is necessary to make a systematic study. Through the comparative analysis of the test results, the vacuum causes soil consolidation, on this basis, the surcharge preloading and vacuum preloading contrast of the vacuum preloading mechanism, analyzes various factors foundation reinforcement finally strengthening effect by vacuum preloading.

Uplift and Settlement Prediction Model of Marine Clay Soil e Integrated with Polyurethane Foam

2019 ◽  
Vol 9 (1) ◽  
pp. 481-489
Author(s):  
D.C. Lat ◽  
I.B.M. Jais ◽  
N. Ali ◽  
B. Baharom ◽  
N.Z. Mohd Yunus ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Clay Soil ◽  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Effective Thickness ◽  
Marine Clay ◽  
Uplift Pressure ◽  
Pu Foam ◽  
Improvement Method

AbstractPolyurethane (PU) foam is a lightweight material that can be used efficiently as a ground improvement method in solving excessive and differential settlement of soil foundation mainly for infrastructures such as road, highway and parking spaces. The ground improvement method is done by excavation and removal of soft soil at shallow depth and replacement with lightweight PU foam slab. This study is done to simulate the model of marine clay soil integrated with polyurethane foam using finite element method (FEM) PLAXIS 2D for prediction of settlement behavior and uplift effect due to polyurethane foam mitigation method. Model of soft clay foundation stabilized with PU foam slab with variation in thickness and overburden loads were analyzed. Results from FEM exhibited the same trend as the results of the analytical method whereby PU foam has successfully reduced the amount of settlement significantly. With the increase in PU foam thickness, the settlement is reduced, nonetheless the uplift pressure starts to increase beyond the line of effective thickness. PU foam design chart has been produced for practical application in order to adopt the effective thickness of PU foam within tolerable settlement value and uplift pressure with respect to different overburden loads for ground improvement works.

Three-Dimensional Numerical Analysis of Tunnel Seepage Based on the Iteration Method

2012 ◽  
Vol 479-481 ◽  
pp. 2441-2445
Author(s):  
Fu Sheng Liu ◽  
Guo Yuan Xu ◽  
Sheng Bin Hu ◽  
Wen Tong Huang ◽  
Min Hu
Keyword(s):  
Ground Water ◽  
Water Level ◽  
Iteration Method ◽  
Water Discharge ◽  
Seepage Flow ◽  
Economic Benefits ◽  
Ground Water Level ◽  
Engineering Practice ◽  
The Impact ◽  
Saturated Surface

The groundwater can cause a significant threat to the safety of the tunnels excavated in water-rich areas. To investigate the impact of seepage to tunnels, the most important issues are calculations of the saturated surface and seepage flow. According to the great similarity between temperature field and seepage field in the theoretical foundation, differential equations and boundary conditions, the thermal analysis function of ANSYS could be used to calculate the non-pressure stable seepage based on the iteration method. The saturated surface and seepage flow through the lining are obtained by take a tunnel as an example, under using iteration method programming in ANSYS software. Additionally, on the basis of the correlation analysis, with the reduction of ground water level, the seepage discharge through the lining decreased sharply at the beginning, and then, the reduction trend gets inconspicuous. It has no obvious effect to decrease the water discharge by reducing the ground water level under this condition. Therefore, taking economic benefits into account, it is unadvisable to lower water level blindly. The optimal analysis of the actual conditions should be carried out in engineering practice. It has a certain reference value to the design and construction of tunnels in water-rich areas.

INNOVATIVE SOFT SOIL IMPROVEMENT BY VACUUM DE-WATERING AND DYNAMIC COMPACTION

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Tuncer B. Edil
Keyword(s):  
Large Scale ◽  
Ground Improvement ◽  
Soft Soil ◽  
High Vacuum ◽  
Cohesive Soil ◽  
Soil Improvement ◽  
Economic Benefits ◽  
Dynamic Compaction ◽  
Environmental Benefits ◽  
Improvement Method

Recently, an innovative soft soil improvement method was advanced in China by integrating and modifying vacuum consolidation and dynamic compaction ground improvement techniques in an intelligent and controlled manner. This innovative soft soil improvement method is referred to as “High Vacuum Densification Method (HVDM)” to reflect its combined use of vacuum de-watering and dynamic compaction techniques in cycles. Over the past ten years, this innovative soft soil improvement technique has been successfully used in China and Asia for numerous large-scale soft soil improvement projects, from which enormous time and cost savings have been achieved. In this presentation, the working principles of the HVDM will be described. A discussion of the range of fine-grained, cohesive soil properties that would make them ideal for applying HVDM as an efficient ground improvement method will be discussed. The economic benefits and environmental benefits of HVDM are elucidated.

Field performance of the port of Sepetiba test fills

1995 ◽  
Vol 32 (1) ◽  
pp. 106-121 ◽  
Author(s):  
Vinod K. Garga ◽  
Luciano V. Medeiros
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Field Performance ◽  
Stone Columns ◽  
Field Investigations ◽  
Large Program ◽  
Soil Deposits ◽  
Load Tests ◽  
The Cost

The design of the industrial port of Sepetiba, 50 km south of Rio de Janeiro, Brazil, required a detailed evaluation of the underlying soft soil deposits. Initially, on the basis of laboratory tests, it was proposed to remove approximately 3.7 × 106 m3 of the very soft deposits in the stockpile area by dredging and substitute with hydraulic sand fill. Subsequently, in view of the cost of such a measure, a large program of field investigations was initiated to study the in situ characteristics of the soft clay to evaluate whether replacement of this material and (or) ground improvement was necessary. As part of this investigation, two large identically instrumented test fills (test fills B and D), each 65 m2 in plan and 5 m high, with 3:1 slopes were constructed. Test fill B was constructed over natural ground, whereas the subsoil beneath test fill D was treated with stone columns. The instrumentation for each test fill consisted of piezometers, deep settlement plates, surface settlement plates, and inclinometers. This paper provides a description of the field investigations, observations on installation of stone columns, analysis of instrumentation, a comparison of the behaviour of the two test fills, and a discussion on load tests on individual stone columns. Key words : case history, embankment, ground improvement, instrumentation, soft clay, stone columns.

scholarly journals Geosynthetic Encased Columns Supporting Rail Infrastructure – Perspectives on Research and Case Studies

2020 ◽  
Author(s):  
Erol Guler ◽  
Cihan Cengiz ◽  
Oliver Detert
Keyword(s):  
Case Studies ◽  
Ground Improvement ◽  
Soft Soil ◽  
Academic Research ◽  
Major Effect ◽  
Economic Benefits ◽  
Shaking Table ◽  
Stone Columns ◽  
Soil Conditions ◽  
Rail Network

Significant investments are being made towards enhancing the reach of the railway infrastructure due to the vast economic benefits it brings. An inevitable consequence of the expansion of the rail network is the soft soil conditions encountered in the alignment. Geosynthetic encased columns (GEC) is a proven ground improvement technology which can be adapted as soil remediation technique for such conditions. In this paper, first an introduction to the concept of GECs will be given. Then the recent advances in the academic research on the GECs will be elaborated. As it is known, earthquakes are one of the most devastating disasters and certainly also have a major effect on transportation infrastructure. In this paper results of shaking table tests to compare ordinary stone columns and GECs behavior under earthquake loading conditions will also be presented. The brief recap of the state of the art on the geosynthetic encased columns including their earthquake behavior will be followed by case studies on three major projects where the site conditions and project requirements will be discussed. The significant benefits of geosynthetic encased columns in relation to project requirements will also be elaborated.

scholarly journals Design and construction of a deep excavation in soft soils adjacent to the Shanghai Metro tunnels

2003 ◽  
Vol 40 (5) ◽  
pp. 933-948 ◽  
Author(s):  
Z F Hu ◽  
Z Q Yue ◽  
J Zhou ◽  
L G Tham
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Theoretical Method ◽  
Horizontal Displacement ◽  
Deep Excavation ◽  
Construction Methods ◽  
Diaphragm Walls ◽  
Shanghai Metro ◽  
Design And Construction

This paper presents the design and construction of a deep excavation for building foundations in saturated soil. This deep excavation was of particular interest because it was located above and beside the Shanghai Metro tunnels. The twin Shanghai Metro tunnels had to be in full operation during the deep excavation. Potential large deformation of the twin tunnels was one of the main concerns during the design and construction for the deep excavation. The paper discusses in detail the criteria and measures for controlling the soil and tunnel deformation. The measures included cast-in-place concrete diaphragm walls with bracing structural members, pumping consolidation, cement–soil mix pile systems, and rational excavation procedures. A simplified theoretical method was proposed to estimate the increment in undrained shear strength in a soft clay layer due to pumping consolidation. Furthermore, conventional finite element methods were used to predict the soil vertical and horizontal displacements induced by the excavation. Using the design and construction methods discussed in the paper, the settlement and horizontal displacement of the tunnels were successfully controlled within 5.0 mm and 9.0 mm, respectively. The curvature of longitudinal deformation curve of the tunnels was less than 1/15 000. The horizontal displacement of the braced diaphragm walls was less than 0.12% of the total excavation depth. Key words: Metro tunnels, saturated soft soil, deep excavation, design, construction, ground improvement, case studies.

scholarly journals Settlement Behaviour of Soft Clay Bed Reinforced with Stone Column under Sustained Loading

2019 ◽  
Vol 9 (2) ◽  
pp. 1744-1749
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Reinforced Soil ◽  
Sustained Load ◽  
Stone Column ◽  
Sustained Loading ◽  
Settlement Behavior ◽  
High Area ◽  
Area Replacement Ratio

This research paper investigates the behaviour of soft clay reinforced with stone column under sustained loading. Experiments were conducted in the laboratory on stone column reinforced prepared soft soil bed of kaolin having strength of 7.5 kPa with aggregate of size 2.5 to 10 mm as column material. The stone column with four diameters of 38.1, 50.8, 63.5 and 76.2mm were constructed which correspond to low to high area replacements ratios (i.e. 6.93% - 26.49%). The plain and reinforced soft clay beds were subjected to a sustained load of 150, 200, 250 and 300 kPa where each applied load has been maintained for 24 hours and the settlement behavior of composite ground was taken into account. The test results represent the settlement of reinforced soil bed decreases with increase of column diameters. The settlement reduction ratio is a measure of ground improvement which increases with area replacement ratio. The experimental and theoretical results values were compared as per IS15284 (Part 1): 2003 with reference of stress concentration ratio ‘n’(The ratio of stress in the column to the stress of surrounding ground area). The % variation in theoretical and experimental results is in the range of 50% and therefore the theoretical procedure needs to be revised.

scholarly journals Colloid effect on clogging mechanism of hydraulic reclamation mud improved by vacuum preloading

2019 ◽  
Vol 56 (5) ◽  
pp. 611-620 ◽  
Author(s):  
Yongfeng Deng ◽  
Li Liu ◽  
Yu-Jun Cui ◽  
Qi Feng ◽  
Xianglong Chen ◽  
...  
Keyword(s):  
Size Distribution ◽  
Pore Water ◽  
Colloidal Particles ◽  
Soil Column ◽  
Soft Clay ◽  
Laboratory Model ◽  
Vacuum Preloading ◽  
Natural Foundation ◽  
Tail Water ◽  
Continuous Vacuum

Many cases of artificial soft clay foundation constructed by hydraulic filling and improved by the vacuum preloading show the clogging phenomenon in the surrounding soil, which compromises the improvement quality. To clarify the clogging mechanism and the formation of soil columns, the vacuum process was tracked from macro to micro by laboratory model tests. Results show that the soil column with higher strength (density) and lower water content was formed surrounding the prefabricated vertical drainage (PVD). Mercury intrusion porosimetry (MIP) tests revealed that the pore-entrance diameter of the soil column after 50 and 43 days of vacuum application ranged from 100 to 600 nm, and that at peak it is 300 nm. However, the mean diameter of the colloidal particles in tail water decreases from 1000 to 100 nm with continuous vacuum application, and then becomes stable at about 100 nm after 43 days. After re-visiting the vacuum process of the hydraulic reclamation mud, the pore-size distribution of surrounding soils and particle-size distribution of the tail water, the clogging was explained by the filling of the pores of the soil column by the colloidal particles in pore water. This mechanism differentiates the artificial foundation improved by vacuum preloading from the natural foundation for the presence of rich colloidal particles in pore water.

Ground movements due to pile driving in an excavation in soft soil

1999 ◽  
Vol 36 (1) ◽  
pp. 152-160 ◽  
Author(s):  
I H Wong ◽  
T S Chua
Keyword(s):  
Precast Concrete ◽  
Soft Soil ◽  
Soft Clay ◽  
Ground Movement ◽  
Pile Driving ◽  
Deep Excavation ◽  
Ground Movements ◽  
Concrete Piles ◽  
Recent Project ◽  
Story Building

An excavation in soft clay for the construction of a deep basement frequently is accompanied by large ground movements that may damage piles preinstalled at the base of the excavation. In a recent project involving the construction of a 10 m wide, 3.7 m deep drain, the construction method adopted entailed excavating the site soils and then driving precast concrete piles. The excavation was supported by steel sheet piles braced by one level of struts. Large settlements and horizontal movements of the ground were observed during pile driving. These movements exceeded those occurring during the excavation phase. Concrete aprons outside a one-story building adjacent to the excavation were badly damaged during excavation and pile driving. However, the building supported on steel piles was undamaged.Key words: deep excavation, sheet piles, pile driving, ground movement, basement construction.

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