Shear strength behaviour of liquefiable sand of petobo on treated by agarose under direct shear test

Liquefaction process is associated with the loss of the shear strength of the saturated loose sands caused by strong earthquakes. Due to mitigitation of liquefaction hazard, an appropriate mitigation of liquefaction using environmentally friendly methods is critical and becoming increasingly important and unavoidable. The laboratory investigation was carried out to study the shear strength behaviour of liquefiable sand of Petobo treated by agarose on different concentration 1%,3% 5%. A series of direct shear test were conducted under three level of vertical stress 10 kPa, 20 kPa, and 30 kPa on the specimen. It was found that the optimum content of agarose which can be considered is at 1%-3%, using stress ratio (τ/σv) analysis shows that stress ratio decreases with increasing the vertical stress on the same agar content. The implication this result that the application of this method must consider variation of material source and characteristic, and the suitable level of vertical stresses.

Shear strength characteristics of Jerash expansive soil

The results of the direct shear test on Jerash expansive soil show the effect of the initial water content on the cohesion (c) and on the angel of internal friction ( ) [shear strength parameters].it show that, as the initial water increase, the cohesion (c) of Jerash expansive soil also increase up to the shrinkage limit, after that increase of water even small amount, decrease the cohesion of the soil. On the other hand, the results of direct shear test show also that as the water content increase, the angle of internal friction ( )remain unchanged up to shrinkage limit , any increase of water cause a large decrease on the angle of internal friction of Jerash expansive soil.

Investigation of the Shear Mechanical Behavior of Sandstone with Unloading Normal Stress after Freezing–Thawing Cycles

Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone samples after a freezing–thawing cycle in this paper. The failure shear displacement (Dsf), the failure normal displacement (Dnf), the shear displacement of unloading (Dsu), and the normal displacement of unloading (Dnu) were analyzed to describe the evolution of shear and normal deformation during the test. The results indicated that the shear displacement increased as the freezing–thawing cycle duration increased in a direct shear test under unloading normal stress. The unloading rate and the number of freezing–thawing cycles affected the failure pattern of the rock sample significantly in both the direct shear test under unloading normal stress and the direct shear test. The three-dimensional inclination angle, the distortion coefficient, and the roughness correlation coefficient of the fracture surface are dependent on the number of freezing–thawing cycles and the unloading rate. The surface average gradient mode of the fracture surface decreased as the freezing–thawing cycle times and unloading rate rose.

Landslide Mitigation through Biocementation

Landslide and other geo-disasters are causing a great damage to people and the resources all over the world. An environment friendly countermeasure of landslide disasters is necessary. Microbially induced calcite precipitation (MICP) is a bio-cementation process that can improve the geotechnical properties of granular soils through the precipitation of calcium carbonate (calcite) at soil particle contacts. This MICP can be an environment friendly solution for the biocementation of soil. In this study, an evaluation of biocemented soil has been carried out through direct shear test and direct simple shear test. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) and X-ray Computed Tomography (X-ray CT) tests were conducted to analysis the calcite precipitation inside the biotreated soil by bacteria by using Toyoura sand and silica sand no. 4. It was observed that the amount of calcite generated in silica sand was larger than Toyoura sand. The particle shape influences the result of calcite precipitation and consequent strength of the bio-cemented sand. The amount of strength which was obtained by direct shear test and direct simple shear test indicated the granular soil became bio-stabilized within 7 days of application of nutrients from the surface. However, the amount of generated calcite was not uniformed in different layers while applying the nutrients and bacterial from the surface which was revealed by X-ray CT scan test.

Investigating the Shear Strength Characteristic of Clayey Soil by Using Coir Fiber & Brick Dust

Soil is main part of every building and structure, without soil no structure could stand up. Soil plays a vital role in the constructure of every structure. If soil is strong in shear strength the building above it will also safe from failure/collapse. So, strength of soil is necessary is the construction of foundation, piers, dams, roads and multistory buildings.To increase the strength of soil we have different choices as to replace the weak soil with the strong soil, or to add other materials in soil to increase its strength like cement, lime etc. This study helps in increasing the shear strength of soil by using brick dust and coir fiber which are waste material but can provide sufficient strength.We use the clayey soil from Nandipur, which is weak in nature. Brick dust obtain from a kiln in Faisalabad and coir fiber which are easily available and economical. Direct shear test is performed to find shear strength and its parameters, CBR is performed to find the bearing capacity of soil and Modified proctor test is used to find out the optimum moisture content and maximum dry density of soil. We perform direct shear test at different percentages of brick dust to find optimum percentage of brick dust and then at this optimum brick dust percentage we vary the percentage of coir fiber to find its optimum value and also CBR for the varying percentage of coir fiber.

A Review of Sand–Clay Mixture and Soil–Structure Interface Direct Shear Test

Natural soils are usually heterogeneous and characterized with complex microstructures. Sand–clay mixtures are often used as simplified soils to investigate the mechanical properties of soils with various compositions (from clayey to sandy soils) in the laboratory. Performing laboratory tests on a sand–clay mixture with definite clay fraction can provide information to understand the simplified soils’ mechanical behavior and better predict natural soils’ behavior at the engineering scale. This paper reviews previous investigations on sand–clay mixture and soil–structure interface direct shear test. It finds that even though there are many investigations on sand–clay mixtures and soil–structure interfaces that consider pure sand or pure clay, limited data on the mechanical behavior of the interface between sand–clay mixture and structure materials are available. Knowledge is missing on how the clay content influences the mechanical behavior of interface and how the soil particles’ arrangement changes as the clay content increases. Further study should be performed to investigate the interface in terms of a reconstituted sand–clay mixture and structure by interface direct shear test, to highlight the influence of clay fraction on the interface response, under various loading conditions.