Geotechnical Properties Of Soft Soil Research Articles

Effect of nano-gypsum on mechanical properties cement admixed marginal silty soil

Even though the chemical stabilization is by far the most common ground improvement technique, very few studies have been conducted on the joint incorporation of two or more additives (cement-nanogypsum mix) to stabilise soft soil. This study investigates the effect on the mechanical properties of cement-stabilised silty soft soil (CSS) using nano-gypsum (NG). Unconfined compression strength (UCS) test trials were conducted to achieve soft soil conditions. The effect of NG and cement on soft soil was investigated by performing Atterberg limit, compaction, UCS, and Direct shear tests. The soil was treated with four percentages (10%, 15%, 20%, and 25%) of cement and with three percentages (1%, 1.5%, and 2%) of NG by its dry unit weight. The test results showed that the plasticity index of the soil was reduced significantly by the addition of stabilizers (Cement-NG mix) making the soil stiffer. The compaction tests suggested that optimum cement content was 20% for CSS and for cement-NG mix maximum strength was achieved at cement: NG proportion of 20:1. The unconfined compression strength (UCS) was increased by 9.11 times in comparison to untreated soft soil at cement: NG proportion of 20:1.5. The direct shear test (DST) suggested that there was an increase in cohesion by 4.44 times in comparison to the untreated sample at the soil–cement-NG combination of 78.5: 20: 1.5. However, the angle of internal friction remained almost unchanged. The development of cementitious substances was confirmed through XRD spectroscopy. Microstructural and chemical properties were observed using combined FESEM-EDAX analysis and Fourier transform infrared spectroscopy (FTIR). The multivariate linear regression (MLR) predictive model was developed for the unconfined compressive strength and failure strain as a function of various parameters considered in the study. The test results demonstrated that the combination of cement and NG can result in remarkable improvement in the geotechnical properties of soft soil. The use of NG may also reduce the demand for cement in deep cement mixing technique, which eventually reduces the carbon footprint and renders the ground improvement technique, ecologically beneficial.

Effect of several patterns of floating stone columns on the bearing capacity and porewater pressure in saturated soft soil

One of the common geotechnical problems is the construction on soft soil and the improvement of its geotechnical properties to meet the design requirements. A stone column is one of the well-known techniques used to improve the geotechnical properties of soft soils. Sometimes thick layers of soft soil imposed the designer to use floating stone columns for improvement of such soil; in this case, the designer will be lost the end bearing of the stone column. In this study, the effects of several patterns of floating stone columns distribution under footing on the bearing capacity of soil and the distribution of excess porewater pressure are investigated. The soft soil used in this study has a very low undrained shear strength (cu) of 5.5 kPa and improved by several patterns of stone columns (single, two linear, triangular, square, and quadrilateral). The stone column has a length of 180 mm and a diameter of 30 mm. The material of the stone column is poorly graded sand has an angle of internal friction (48.5°) at a relative density of 65%. The results indicated a significant increase in the ultimate bearing capacity of soft soil when treated with floating stone columns despite the small ratio of area replacement and reducing the excess porewater pressure and settlement. Also, the ultimate bearing capacity of soil calculated from experimental work is compared with the corresponding values obtained from the proposed equations in the previous studies to evaluate the validity of using such equations.

Solidification and field assessment of soft soil stabilized by a waste-based binder using deep mixing method

In an effort to reduce energy consumption and protect environment, developing an alternative to reduce or replace the use of cement in soil stabilization has been a topic research since long. This paper presents a novel binder (called GS agent, G and S are the initials of gypsum and slag, respectively) for stabilizing soft soil based on industrial solid wastes. A series of laboratory tests and a field test adopting deep mixing method was conducted to compare and analyze the geotechnical properties of soft soils by the GS binder and cement. Scanning electron microscopy (SEM) was performed to reveal the micro-mechanism of the stabilized soft soils. The results showed that the stabilized soil had permeability approximately 1 order lower in magnitude than the untreated soil, and significantly increased the unconfined compressive strength and cohesion of the untreated soil. The novel agent produced more hydration products and its stabilized soil formed a relatively firm reticular structure as compared to the cement-stabilized soil. An empirical design method was developed for determining the mechanical properties of GS agent-stabilized soil. Its feasibility was verified through comparing the predictions with the test datum.

Influence of Fly Ash Addition on Behavior of Soft Clayey Soil

This paper investigates the impact of the fly Ash addition on the Geotechnical properties of soft soil as well as chooses the optimum percentage added of fly ash. To understand the behavior of fly ash mixed with soil, a number of laboratory experiments testing conducted on clayey soil-fly ash mixture in several percentages (5,10,15,20,25, and 30%) as Atterberg test, Specific gravity test, compaction test, California Bearing Ratio (C.B.R) Test, Unconfined Compressive Strength (UCS) Test, Consolidation Test. Test results indicate rising in plastic limit and liquid limit as fly ash adding. Specific gravity decreased essentially by adding fly ash. Whereas there was falling on the Dry unit weight value with the contract to the decreasing in the water content. The CBR and UCS values were increased with increasing fly ash content. 20% was the optimum fly Ash content. This study also benefits the effective use of fly ash and thus a cost-effective method for improving the soil properties.

POTENTIAL OF GRANITE DUST TO IMPROVE THE ENGINEERING PROPERTIES OF SOFT SOILS FOR ROAD CONSTRUCTION

Soft soils such as clay soils, mostly if they comprise swelling minerals may produce great damage to structures, particularly when these soils are exposed to wetting and drying situations. The geotechnical properties of soft soils could be enhanced by utilizing chemical additives. In this paper, granite waste dust was used to adjust the properties of clay soils. This paper investigates the effect of granite rock dust on the geotechnical properties of soft soil. The particle size distribution, Atterberg limits, compaction, California bearing ratio (CBR) and direct shear strength characteristics of the soil when blended with various percentages of granite dust were evaluated. The findings show a great increase in the maximum dry density, optimum water content, direct shear strength and CBR with increasing the amount of granite dust. The best results obtained for CBR values were when the soils mixed with 8% granite dust. Although these findings indicate great improvement in the geotechnical parameters of clayey soils, the higher strength established is not enough for the enhanced soil to be utilized as a base material in the construction of heavily-trafficked flexible pavements. However, this modified material can be used as a base material for moderate traffic roads and as a sub-base material for high traffic roads.

An analysis of freeze-thaw cycles on geotechnical properties of soft-soil

Soft-soil structural having more porous that effects on the index, chemical, and engineering properties of soil. These porous presents in soft soils lead to changes in geotechnical properties and more impact on freeze-thawing cycling that must have taken into consideration when selecting soil properties for settlement, seepage, and stability of geotechnical structures. This paper presents determine the index and engineering properties of soft soil and the influence of freeze-thaw 1, 3, 5, and 7 cycles of soft –soil and check the effect of geotechnical properties. Tests for geotechnical properties are Atterberg’s limits, Compaction, Permeability, Unconfined compressive strength (UCS), XRF, and Consolidation test. Effect of freeze-thaw cycles on soft-soil, it results in the permeability of soil increase desperate the change in void ratios and decreases the shear strength of soft soil. Also, increasing freeze-thaw cycles shows more ductility nature in soil.

Improvement of Geotechnical Properties of Cohesive Soil Using Crushed Concrete

Some natural resources such as gravel are not renewable, therefore, it is necessary to reduce the use of such resources and replace them with other recycled, economic, and environmentally friendly materials. Recycled crushed concrete aggregates demolished from old buildings and blocks of waste concrete can be used to replace the natural aggregates. The present study focused on using recycled crushed concrete in improvement the chemical and geotechnical properties of soft soil having undrained shear strength of 6.78 kPa. The soft soil samples were mixed with 5, 10, and 15% of crushed concrete. The blocks of waste concrete are grinded by mills to get crushed concrete which passing sieve no. 4. Such aggregates are lighter than natural aggregates and provide a good deformation modulus when mixed with soil. In Iraq, there are hundred thousand tons of concrete blocks used as fences and now considered wastes after removing these security fences, so it’s important to interest from recycling of such materials to be used in the improvement wide region of soft soils in Iraq. The results of tests showed increasing the undrained shear strength of soft soil by 175-193.5% and reduced the compressibility of soft by 25-31% measured in terms of compression index.

Comparative Study on Geotechnical Properties of Soft Soils Considering Depositional Environment

Comparative Study on Geotechnical Properties of Soft Soils Considering Depositional Environment

The use of alkali activated waste binders in enhancing the mechanical properties and durability of soft alluvial soils

This paper presents recent work in utilising industrial by-products as sustainable binders for use in deep soil mixing, to enhance the geotechnical properties of soft soils. The study has used geotechnical and mineralogical tests to determine the performance of the binders when incorporated into an artificial silty sand soil. Comparisons with the strength and durability of untreated and stabilised soils have been made. The study indicates that from the by-products tested, soils stabilised with alkali activated blast furnace slag resulted in the greatest strength and durability improvements; with other materials tested showing smaller improvements. The addition of alkali activators has been observed to allow pozzolanic reactions to occur, which has led to improved mechanical properties; primarily strength, which increased with time. The durability of the soil was improved by the additions of by-products, though alkali activation did not cause significant additional increase in durability.

Sludge ash/hydrated lime on the geotechnical properties of soft soil

In this study, an effort to improve the properties and strength of soil, sewage sludge ash (SSA) and hydrated lime are applied to stabilize soft cohesive subgrade soil. Five different ratios (in weight percentage), 0%, 2%, 4%, 8%, and 16%, of sludge ash/hydrated lime are proposed for mixture with cohesive soil. Then, the effects of the different proportions of SSA/hydrated lime on soft cohesive soil are studied. Test results indicate that the unconfined compressive strength of specimens with additives was raised from three to seven times better than that of the untreated soil, and swelling behaviors were also effectively reduced for those specimens. Results of triaxial compression test indicate that the shear strength parameter, c, rose with an increased amount of additives and improved from 30 to 50–70 kPa. On the whole, SSA/hydrated lime could particularly improve the geotechnical properties of cohesive subgrade soil.