Peat Soils

The purpose of this paper is to advance the knowledge on peat soil stabilization by critically examining and documenting the current state of practice. Deep Mixing method is emphasised on column type techniques using lime/cement. This paper is essentially a comprehensive review of available academic literature on deep soil stabilization utilizing this approach. Deep mixing with lime or lime-cement column and combined soil stabilization with vertical columns (CSV) methods are discussed and to illustrate applications of these methods in a variety of conditions, several case histories are presented. © 2008 ejge.

ejge.com/2008/Ppr0860/Ppr0860.pdf

Characterized by high initial void ratio, organic content and water holding capacity, fibrous peat exhibits high compressibility and low shear strength. Consequently, formation of deep fibrous peat layer often poses difficulties in construction. In practice, compressibility of deep fibrous peat layer can be reduced by deep soil stabilization technique. The technique is developed in such a way that dry binders are mixed with in situ peat soil to form columnar reinforcement in the deep peat ground prior to preloading. Preloading simulations of both untreated and stabilized peats were carried out in laboratory by loading of both soils using standard oedometer consolidation apparatus. Ordinary Portland cement, ground granulated blast furnace slag and siliceous sand were used to stabilize the soil. Analysis on the time-compression curves from the tests revealed that coefficients of vertical consolidation (cv of both soils were best predicted using square root of t52.6 method when compared to those evaluated using conventional curve fitting methods. Main reason for this is the experimental time-compression curves for the method best fit its theoretical curve. In addition, the method predicts cv of soil at 52.6% average degree of consolidation, which is less likely to be affected by secondary compression that usually occurs concurrently at the later stage of soil primary consolidation. © 2008 ejge.

ejge.com/2008/Ppr0862/Ppr0862.pdf

A field model study has been carried out to stabilise peat soil using various types of binder by deep mixing method and to investigate its effect on engineering properties. Some soil-cement model columns have been constructed at site and different mechanical properties of stabilised peat, like undrained shear strength, unconfined compressive strength and shear strength was determined after 14 days of curing time. Scanning Electron Micrograph (SEM) and Energy Dispersive X-Ray (EDX) test were also conducted to observe the microstructure of stabilised peat soil. From the test result it was observed that the engineering properties of peat soil can be improved by stabilisation using additives. © 2008 ejge.

www.ejge.com/2008/Ppr0897/Ppr0897.pdf

Peaty soils are not suitable as foundation soils as they are weak and highly compressible. This paper describes a study on peat soil stabilisation to improve its physical and engineering properties. It investigates the effect of additives (binder amount 5%, 10% and 15% (85%cement, 15% bentonite) and range of sand 5% to 25% on the index properties as well as, pH, compaction, California Bearing Ratio and unconfined compressive strength of tropical peat soils. The amount of additives added to the peat soil sample was investigated in terms of the percentage of the dry soil mass. The results showed that of the additive admixtures altered the engineering properties of tropical peat soils. The soil liquid limit was found to decrease with increase of the additive content. The pH was found to increase with increase binder. The maximum dry density was found to increase while the optimum moisture content was found to decrease with the increase of the additive content. The California Bearing Ratio of the soil was found to increase significantly with increase in the additives. © 2008 ejge.

ejge.com/2008/Ppr0834/Ppr0834.pdf

The main objective of this study is to stabilize peat soil by deep mixing method using cement, sand, benlonite and calcium chloride as binder and to determine the effect on bearing capacity using proving ring hand operated cone penetrometer. Eight soil-binder columns have been constructed by mixing auger and prebored and premixing method using two different combination of binder. Bearing capacity of the columns has been evaluated by hand operated cone penetrometer after 1, 3, 7, 14 and 28 days of curing time. From the test results it was observed thai bearing capacity of peal column increased considerably after stabilization. © 2009 Asian Network for Scientific Information.

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