Bearing Capacity Assessment of Collapsible Soils Improved by Deep Soil Mixing Using Finite Element Method

Problematic soils usually cause considerable problems to engineering projects. As an example, soil structure collapse caused by moisture increment or rising underground water level results in huge settlements. This type of problematic soil, named collapsible soil, can cause dramatic problems and should be amended where exists. Today, the use of different techniques for soil reinforcement and soil improvement is widely used to treat soil properties. One of these methods is Deep Soil Mixing (DSM) method. This method becomes more important in the cases of studying and examining collapsible soils. In this research, the settlement of amended collapsible soils, applying deep soil mixing method, is examined. The experiments show that soil amendment using this method, well prevents the settlement of collapsible soils giving rise to bearing capacity.

Evaluation of the Collapsibility of Soils in the Semiarid Region of Pernambuco, Brazil

Some unsaturated soils may undergo volumetric changes when submitted to an increase in its water content or are inundated under applied loads. This behavior is related to the volumetric instability when the water content is changed. Natural collapsible soils in Brazil are generally found in alluvial, colluvial and residual soils. There are known occurrences of natural collapsible soils in many states of Brasil. In the last two decades, many public projects have been developed in areas where the occurrence of collapsible soils has been associated to geotechnical problems. The present paper devoted to study the collapsible soils in the state of Pernambuco which has been associated with large engineering projects such as housing and irrigation canals. The geotechnical investigation program included test with a field apparatus, called Expanso-colapsometer, which allows the measurement of the field settlements of a small 0.10 m of diameter plate inserted at any depth inside an auger boring hole. Reconnaissance borings with SPT （standard penetration test）, investigation pits with undisturbed block sampling and disturbed samples for laboratory tests were also made in order to assess the type and characteristics of the soil. Field tests used the Expanso-colapsometer to measure the settlement of the soil in selected depths under controlled flooding. Laboratory work included double and standard oedometer tests with a controlled rate of water inflow of 1.0 mL/s. It was found that the volume change of the soils when flooded depends on their natural stress state （vertical stress, suction head and structure of soil）.

Enhancing mechanical behaviors of collapsible soil using two biopolymers

This study aims to investigate the possibility of using biopolymer(environmental friendly material) to enhance the mechanical behaviors of collapsible soil.Two types of biopolymers were(xanthan gum and guar gum) used in this study due to their stable behaviors under severe conditions and their availability with reasonable prices.The experimental program focused on three major soil properties,i.e.compaction characterizations,collapsible potential and shear parameters.These three properties are essential in process of soil improvement.Different biopolymer concentrations were used in this study and the experimental program was performed at two curing periods(soon after mixing the soil with the biopolymer and after one week curing time).Shear parameters were measured for the treated specimens under both soaked and unsoaked conditions,while a collapsible potential test was performed under different mixing conditions(wet mix and dry mix).A numerical model was built to predict the behavior of the treated collapsible soil after and before water immersing.The results indicated that the ability of both xanthan gum and guar gum can be used as improvement materials for collapsible soil treatment.The collapsible potential has been reduced from 9%to 1%after mixing the soil with 2%biopolymer concentration in the wet case.After one week curing,the cohesion has been increased from 8.5 kPa to105 kPa by increasing the xanthan gum concentration from zero to 2%,leading to an overall improvement in soil shear strength.It also proves that the guar gum is superior to the xanthan gum.The shear strength of soil can be increased by about 30%when using the guar gum in comparison with the xanthan gum at the same conditions;however,the collapsible potential of soil material will be reduced by about 20%.

Utilization of Marble Dust for Improving The Geotechnic Characteristics Of Collapsible Soil

An environment friendly and cost effective factor of collapsible soilstabilization with the help of industrial waste has been widely adoptedin this research. Buildings which are constructed on collapsible soils aresubjected to large deformations and shear failure. Collapsible soil can bebroadly categorized as those soils susceptible to a large reduction in volumeupon wetting. The mechanism usually involved in rapid volume reductionentails breaking of bonds at coarse particle contacts by weakening of finegrainedmaterials brought there by surface tension in evaporating water.This research presents the effects of using marble dust on the geotechnicalproperties of Collapsible soil as a new stabilizing technique. A series ofexperimental tests are carried for samples of collapsing soil with andwithout stabilization using marble dust for dry and soaked conditions.The collapsible soil was mixed with marble dust at different contents of(0, 10, 20, 30%,40% and50%). The results indicated that, The optimumwater content decreases by 20.67% at marble content of 50%, liquidlimit decreses by35.41% at marble content of 50%and frictional angle forsoaked soil decreases by 66.09% at marble content of 50% while un soakedsoil decreases by54.68% at marble content of 50%. The maximum drydensity increases 5.91% at marble content of 50% and cohesion for soakedincreases314.2% at marble content of 50% while un soaked soil increases206.7% at marble content of 50%. It has been found that the adoptedmarble has a good effect in controlling the collapsing potential which isreduced by as much as 64.32% at marble content of 30%.

Effects of land uses on soil physic-chemical properties and erodibility in collapsing-gully alluvial fan of Anxi County,China

the National Key Technologies R＆D Program of China during the 12th Five-Year Plan period （2011BAD31B00）

A Systematic Study of Soil Collanses for Railway Slopes

A set of soil collapse prediction and prevention swtem for railway slopes is builtis this paper. Based on the field investisation, Oreen-Ampt model, the quantitytheory and computeraided decision-making sgutem, convereion tables ofworking rainfall ,grading tables of resistant ability to rainfall, and the warningrairifall levels are made, forming the chief part of a practical computer-aideddecisionmaking system. Usins the system, the danser degree of railway slopescan be predicted, and the reinforcins ensineerins and the flood control workcan also be arranged ratiofially.

A new method of studying collapsibility of loess

A new triaxial testing system that could control suction in wetting-induced collapsible tests was success-fully developed to study the suction effects on wetting-induced collapsible deformation.The pedestal of the triaxial cell was made up of two parts,and the equipment not only could control suction but also could make water accessible to soil.A pressure/volume-controlled equip-ment was combined with the triaxial system to measure the water volume absorbed by samples accurately and to add pressure on water to filtrate into the sample.The apparatus could measure volume change precisely and keep the deviator stress unvaried,as well as measure the volume of water filtrating into the samples exactly.A triaxial collapsible testing procedure was described using the new apparatus for undisturbed collapsible loess with controlled suction.Furthermore,a series of double triaxial collapsible tests were conducted under different suctions and the same net cell pressure,and tests under different net cell pressures and the same suction were also done.It was indicated that the collapsible deformation increased with the increasing suction,and the effect of the net cell pressure on collapsible deformation was remarkable.The new triaxial apparatus was a useful facility to study the collapsible behavior of loess.