Consolidation theory for a composite foundation considering radial and vertical flows within the column and the variation of soil permeability within the disturbed soil zone

2010 ◽  
Vol 47 (2) ◽  
pp. 207-217 ◽  
Author(s):  
Meng-Meng Lu ◽  
Kang-He Xie ◽  
Biao Guo
Keyword(s):  
Soil Column ◽  
Composite Foundation ◽  
Stone Column ◽  
Governing Equations ◽  
Soil Zone ◽  
Disturbed Soil ◽  
Variation Patterns ◽  
Present Solution ◽  
Actual Design ◽  
Continuity Assumption

To remedy the contradiction between the equal strain assumption and the flow continuity assumption at a soil–column interface, the traditional flow continuity assumption was abandoned and the radial and vertical flows within a stone column were incorporated to consider the column consolidation and deformation in a coupled fashion. Moreover, two possible variation patterns of the horizontal permeability coefficient of soil within the disturbed soil zone were included, to reflect the detrimental influence on the surrounding soil due to column construction. In addition, a linearly changed total vertical stress along the column depth was assumed, to achieve a more realistic stress distribution in practice. By considering the above mentioned characteristics, the governing equations for this type of consolidation problem were developed. The solutions for the governing equations were subsequently derived by using a new initial condition obtained from the equilibrium condition and equal strain assumption. On the basis of this, the average degree of consolidation of the composite foundation was obtained and discussed. Finally, a parametric study was performed and an application example was introduced to help engineers better utilize the present solution when applied to an actual design.

scholarly journals Consolidation Theory for a Stone Column Composite Foundation under Multistage Loading

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Shenggen Huang ◽  
Yingtao Feng ◽  
Hao Liu ◽  
Wenbing Wu ◽  
Guoxiong Mei
Keyword(s):  
Separation Of Variables ◽  
Special Property ◽  
Composite Foundation ◽  
Stone Column ◽  
Consolidation Theory ◽  
Present Solution ◽  
Long Time ◽  
Degree Of Consolidation ◽  
Site Test ◽  
Multistage Loading

The consolidation theories considering instant load cannot fully reveal the consolidation mechanism of a stone column composite foundation used in the expressway embankments due to the time effect of loading; that is, the expressway embankments are often constructed in several stages for a long time. Meanwhile, owing to the special property that the pile-soil stress ratio is larger than 1, the consolidation theory for sand drain well foundation cannot be used directly in the consolidation analysis of stone column composite foundation. Based on the principle that the vertical load applied on the composite foundation is shared by the stone column and the surrounding soil, the governing solutions for the stone column composite foundation under a multistage load are established. By virtue of the separation of variables, the corresponding solutions of degree of consolidation for loading stage and maintaining load stage are derived separately. According to the Carrillo theorem, the solution for the average total degree of consolidation of entire composite foundation is also obtained. Finally, the reasonableness of the present solution has been verified by comparing the consolidation curve calculated by the present solution with that measured by site test.

scholarly journals Enhanced Removal of Contaminants of Emerging Concern through Hydraulic Adjustments in Soil Aquifer Treatment

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2627
Author(s):  
Jana Sallwey ◽  
Anna Jurado ◽  
Felix Barquero ◽  
Jens Fahl
Keyword(s):  
Soil Column ◽  
Treated Wastewater ◽  
Management Technique ◽  
Soil Aquifer Treatment ◽  
Contaminants Of Emerging Concern ◽  
Removal Capacity ◽  
Soil Zone ◽  
Cycle Lengths ◽  
Wetting And Drying Cycle ◽  
Operational Modes

Water reclamation through the use of soil aquifer treatment (SAT) is a sustainable water management technique with high potential for application in many regions worldwide. However, the fate of contaminants of emerging concern (CECs) during the infiltration of treated wastewater during SAT is still a matter of research. This study investigates the removal capacity of 27 CECs during SAT by means of infiltration experiments into a 6 m soil column. Additionally, the influence of the hydraulic operation of SAT systems on the removal of CECs is investigated by changing the wetting and drying cycle lengths. Sixteen out of 27 CECs are efficiently removed during SAT under various operational modes, e.g., bezafibrate, diclofenac and valsartan. For six substances (4-methylbenzotriazole, amidotrizoic acid, benzotriazole, candesartan, hydrochlorothiazide and sulfamethoxazole), removal increased with longer drying times. Removal of amidotrizoic acid and benzotriazole increased by 85% when the drying cycle was changed from 100 to 444 min. For candesartan and hydrochlorothiazide, removal improved by 35%, and for 4-methylbenzotriazole and sulfamethoxazole, by 57% and 39%, respectively. Thus, enhanced aeration of the vadose soil zone through prolonged drying times can be a suitable technique to increase the removal of CECs during SAT.

Behavior of Sand Compaction Columns Installed in Cohesionless Deposits

2020 ◽  
Vol 14 (2) ◽  
Author(s):  
N. Aarthi
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Internal Friction ◽  
Critical Appraisal ◽  
Diameter Ratio ◽  
Composite Foundation ◽  
Stone Column ◽  
Fe Model ◽  
Angle Of Internal Friction ◽  
Settlement Behavior

A critical appraisal of the reviewed literature revealed that there are very limited studies avail-able on the strength characteristics focusing on the load-settlement behavior of sand compaction col-umns (SCCs) when installed in cohesionless deposits. The method, though contemporary to the reputed stone column technique, is not yet studied rigorously in the available past studies, more precisely on the load-bearing characteristics when compared to the latter. Therefore the present study focuses on studying the behavior of multiple column composite foundation supported by sand compaction columns installed in loose to medium dense sands on a lab-scale numerical model. The study is carried out using commercially available finite element (FE) code 3D PLAXIS. Spacing to diameter ratio (S/D) ranging from 1.5 to 3.5 and initial relative density (RD) from 30 to 60% was adopted to study the changes in the load-settlement behavior of the improved deposit. Extending the FE model to further parametric study, the effect of angle of internal friction of the column sand and diameter of the column on the bearing capacity and settlement characteristics were analysed with and without normalization. From the results obtained, it is found that, for the considered FE model, the improved deposit with 3D spacing between the SCCs behaves distinctly different from all other cases analyzed.

Reinforcement Effect of Vibration Replacement Stone Column Test in Test Pile Area for One Crude Oil Business Reserve Base

2014 ◽  
Vol 584-586 ◽  
pp. 1922-1932
Author(s):  
Shun Xiang Meng ◽  
Shi Ming Xiao ◽  
Wei Liang ◽  
Qian Kun Gao
Keyword(s):  
Crude Oil ◽  
Bearing Capacity ◽  
Composite Foundation ◽  
Engineering Properties ◽  
Stone Column ◽  
Foundation Soil ◽  
Oil Storage ◽  
Foundation Treatment ◽  
Deformation Properties ◽  
Foundation Pile

The crude oil storage tank foundation is always treated by using vibration replacement stone column composite foundation treatment, mainly to improve the engineering properties of foundation soil and the deformation properties of soil, improving the bearing capacity of composite foundation, and to ensure the normal use of tank in the superstructure loads from damage or excessive deformation. Before construction to carry out the vibration replacement stone column composite foundation pile test, the test shows that strengthening the foundation bearing capacity characteristic value of vibration replacement stone column can meet the design requirements.

scholarly journals Comparative Study of Existing Cement Fly Ash Gravel pile and Encased Stone Column Composite Foundation

2021 ◽  
Vol 1197 (1) ◽  
pp. 012002
Author(s):  
N. B. Umravia ◽  
C.H. Solanki
Keyword(s):  
Fly Ash ◽  
Lateral Displacement ◽  
Ground Improvement ◽  
Pile Group ◽  
Composite Foundation ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Seismic Load ◽  
Total Settlement ◽  
Lateral Behavior

Abstract The Cement Fly Ash and Gravel (CFG) Pile and Encased Stone Column (ESC) are the ground improvement techniques. The main object of the study is to the numerical analysis of the Both techniques pile group were used to support the Embankment with and without the geotextile both techniques composite foundation by the Finite Element method under static and dynamic load analysis. Numerical simulation has been carried out in Plaxis 3D. A case study from china’s highspeed embankment supported by CFG and ESC have investigated the load caring capacity by soil and pile. While the failure behaviors, settlement, excess pore pressure, and lateral behavior with variable embankment loading and number of geosynthetic effect moreover, the diameter of CFG piles and ESC at various locations in an embankment has been varied to study its influence on the load distribution among the CFG piles/ESC and lateral load displacement of the pile group. The results show that increasing the diameter of both techniques reduced the total settlement and differential settlement of embankment. It observed that the seismic load has a significant effect on the vertical and lateral displacement.

Calculation Method of Soil-Column Area Replacement Ratio in the Composite Foundation

2013 ◽  
Vol 405-408 ◽  
pp. 216-220
Author(s):  
Jing Qin ◽  
Wei Lu ◽  
Yun Zhao
Keyword(s):  
Soil Column ◽  
Engineering Application ◽  
Composite Foundation ◽  
Replacement Ratio ◽  
Pile Diameter ◽  
Error Ratio ◽  
Spacing Ratio ◽  
Pile Arrangement ◽  
Area Replacement Ratio ◽  
Two Parameters

The calculation equations of soil-column area replacement ratio (m) recommended by Chinese code Technical Code for Ground Treatment of Buildings (JGJ79-2012) have many limits in the practice. In this document, general equations of m value are derived by subdividing the composite soil element under the different pile arrangements. The results show that m value is determined by the two parameters: interval number among piles (n) and pile diameter-spacing ratio (d/s). m value greatly decreases with the increase of d/s at the constant n, whereas m slightly decreases with the increase of n at the constant d/s, and the larger n, the smaller drop of m value. Under triangular pile arrangement, the Chinese code recommended equations can be used with less than 10 percent of error ratio of m value when the width of composite foundation is above 10 m, but the general equations should be applied when the width is below 10 m. Under square pile arrangement, the recommended equations can be used when the width of composite subgrade is above 15 m, but the general equations should be applied when the width is below 15 m. The general calculation equations of m value derived in this paper can provide certain reference for theoretical calculation and engineering application.

scholarly journals Dynamic Characteristics of Saturated Silty Soil Ground Treated by Stone Column Composite Foundation

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Yongxiang Zhan ◽  
Guanlu Jiang ◽  
Hailin Yao
Keyword(s):  
Performance Improvement ◽  
Shear Displacement ◽  
Composite Foundation ◽  
Shaking Table ◽  
Stone Column ◽  
Amplification Coefficient ◽  
Silty Soil ◽  
Acceleration Amplification ◽  
Table Model ◽  
Shaking Table Model Test

A shaking table model test was carried out to develop an understanding of the performance improvement of saturated silty soil ground using stone column composite foundation as reinforcement. It is found that at less than 0.161 g loading acceleration, soil between piles has not yet been liquefied, the response acceleration scarcely enlarges, and the shear displacement almost does not appear in silty soil. At 0.252 g loading acceleration, as a result of liquefaction of soil between piles, the response acceleration increases rapidly and reaches its peak, and the shear displacement of silty soil increases significantly. At 0.325 g loading acceleration, the integral rigidity of foundation decreases greatly, which reduces its capability of vibration transmission and result in the response acceleration amplification coefficient is less than that at the former loading acceleration, but the shear displacement of silty soil further increases. The stone column composite foundation can greatly reduce both the shear displacement and the settlement of ground compared with untreated foundation. Under the condition of 7-degree seismic fortification, the design meets seismic resistance requirements.

scholarly journals Model Testing of Encased Stone Column Composite Foundations under Traffic Loads

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yongquan Yuan ◽  
Minghua Zhao ◽  
Yao Xiao ◽  
Chaowei Yang
Keyword(s):  
Stress State ◽  
Cyclic Load ◽  
Soft Soil ◽  
Composite Foundation ◽  
Stone Columns ◽  
Stone Column ◽  
Laboratory Model ◽  
Test Results ◽  
Efficient Treatment ◽  
Traffic Loads

In soft soil foundations, geogrid encased stone column composite foundation technology has been widely applied and developed in recent years due to its efficient treatment. In this study, eight groups of laboratory model tests were performed in a large-scale testing tank to investigate the bearing mechanism and stress characteristics of the composite foundation of geogrid encased stone columns under traffic loads with different cyclic load ratios. The stress at the bottom of the stone column and settlement of the composite foundation were measured and analysed. The test results show that cyclic shearing will cause the rearrangement of the soil particles at the column-soil interface, which will cause changes in the face pressure and effective stress state of the column-soil boundary. The cyclic load has a substantial influence on the accumulation settlement of the composite foundation and the development of the lateral stress state of the column. Based on the test results, the development law of the cumulative settlement is summarized, and the change mechanism of the column stress state is analysed and discussed.

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