Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 5

direct shear Related Abstracts

5 Calculating Shear Strength Parameter from Simple Shear Apparatus

Authors: G. Nitesh

Abstract:

The shear strength of soils is a crucial parameter instability analysis. Therefore, it is important to determine reliable values for the accuracy of stability analysis. Direct shear tests are mostly performed to determine the shear strength of cohesionless soils. The major limitation of the direct shear test is that the failure takes place through the pre-defined failure plane but the failure is not along pre-defined plane and is along the weakest plane in actual shearing mechanism that goes on in the field. This leads to overestimating the strength parameter; hence, a new apparatus called simple shear is developed and used in this study to determine the shear strength parameter that simulates the field conditions.

Keywords: direct shear, simple shear, angle of shear resistance, cohesionless soils

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4 Influence of Yield Stress and Compressive Strength on Direct Shear Behaviour of Steel Fibre-Reinforced Concrete

Authors: Mostefa Hamrat, Bensaid Boulekbache, Mohamed Chemrouk, Sofiane Amziane

Abstract:

This study aims in examining the influence of the paste yield stress and compressive strength on the behaviour of fibre-reinforced concrete (FRC) versus direct shear. The parameters studied are the steel fibre contents, the aspect ratio of fibres and the concrete strength. Prismatic specimens of dimensions 10x10x35cm made of concrete of various yield stress reinforced with steel fibres hooked at the ends with three fibre volume fractions (i.e. 0, 0.5, and 1%) and two aspects ratio (65 and 80) were tested to direct shear. Three types of concretes with various compressive strength and yield stress were tested, an ordinary concrete (OC), a self-compacting concrete (SCC) and a high strength concrete (HSC). The concrete strengths investigated include 30 MPa for OC, 60 MPa for SCC and 80 MPa for HSC. The results show that the shear strength and ductility are affected and have been improved very significantly by the fibre contents, fibre aspect ratio and concrete strength. As the compressive strength and the volume fraction of fibres increase, the shear strength increases. However, yield stress of concrete has an important influence on the orientation and distribution of the fibres in the matrix. The ductility was much higher for ordinary and self-compacting concretes (concrete with good workability). The ductility in direct shear depends on the fibre orientation and is significantly improved when the fibres are perpendicular to the shear plane. On the contrary, for concrete with poor workability, an inadequate distribution and orientation of fibres occurred, leading to a weak contribution of the fibres to the direct shear behaviour.

Keywords: Concrete, Orientation, Strength, fibre, direct shear, yield stress

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3 Using Biopolymer Materials to Enhance Sandy Soil Behavior

Authors: Abdelazim Negm, Mohamed Ayeldeen

Abstract:

Nowadays, strength characteristics of soils have more importance due to increasing building loads. In some projects, geotechnical properties of the soils are be improved using man-made materials varying from cement-based to chemical-based. These materials have proven successful in improving the engineering properties of the soil such as shear strength, compressibility, permeability, bearing capacity etc.. However, the use of these artificial injection formulas often modifies the pH level of soil, contaminates soil and groundwater. This is attributed to their toxic and hazardous characteristics. Recently, an environmentally friendly soil treatment method or Biological Treatment Method (BTM) was to bond particles of loose sandy soils. This research paper presents the preliminary results of using biopolymers for strengthening cohesionless soil. Xanthan gum was identified for further study over a range of concentrations varying from 0.25% to 2.00%. Xanthan gum is a polysaccharide secreted by the bacterium Xanthomonas campestris, used as a food additive and it is a nontoxic material. A series of direct shear, unconfined compressive strength, and permeability tests were carried out to investigate the behavior of sandy soil treated with Xanthan gum with different concentration ratios and at different curing times. Laser microscopy imaging was also conducted to study the microstructure of the treated sand. Experimental results demonstrated the compatibility of Xanthan gum to improve the geotechnical properties of sandy soil. Depending on the biopolymer concentration, it was observed that the biopolymers effectively increased the cohesion intercept and stiffness of the treated sand and reduced the permeability of sand. The microscopy imaging indicates that the cross-links of the biopolymers through and over the soil particles increase with the increase of the biopolymer concentration.

Keywords: Sand, Permeability, Shear Strength, biopolymer, direct shear, xanthan gum

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2 Experimental Investigation on the Shear Strength Parameters of Sand-Slag Mixtures

Authors: Amin Chegenizadeh, Hamid Nikraz, Ayad Salih Sabbar

Abstract:

Utilizing waste materials in civil engineering applications has a positive influence on the environment by reducing carbon dioxide emissions and issues associated with waste disposal. Granulated blast furnace slag (GBFS) is a by-product of the iron and steel industry, with millions of tons of slag being annually produced worldwide. Slag has been widely used in structural engineering and for stabilizing clay soils; however, studies on the effect of slag on sandy soils are scarce. This article investigates the effect of slag content on shear strength parameters through direct shear tests and unconsolidated undrained triaxial tests on mixtures of Perth sand and slag. For this purpose, sand-slag mixtures, with slag contents of 2%, 4%, and 6% by weight of samples, were tested with direct shear tests under three normal stress values, namely 100 kPa, 150 kPa, and 200 kPa. Unconsolidated undrained triaxial tests were performed under a single confining pressure of 100 kPa and relative density of 80%. The internal friction angles and shear stresses of the mixtures were determined via the direct shear tests, demonstrating that shear stresses increased with increasing normal stress and the internal friction angles and cohesion increased with increasing slag. There were no significant differences in shear stresses parameters when slag content rose from 4% to 6%. The unconsolidated undrained triaxial tests demonstrated that shear strength increased with increasing slag content.

Keywords: slag, Shear Strength, direct shear, UU test

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1 The Effect of Zeolite on Sandy-Silt Soil Mechanical Properties

Authors: Shahryar Aftabi, Saeed Fathi, Mohammad H. Aminfar

Abstract:

This is well known that the cemented sand is the one of the best approach for soil stabilization, In some case, a blend of sand, cement and other pozzolan materials such as zeolite, Nano-particles and fiber can commercially be available and effectively used in soil stabilization especially in road construction this research is based on the geotechnical characteristics of zeolite composition with sandy silt soil so that the effect of CaO content in zeolite texture on soil resistance were investigated. Zeolites have low amount of CaO in their structures (3-10%) in which by removing cement paste if it could supply a basic environment pH > 10.5, we would see an improvement in the strength of soil samples and make calcined zeolites. In this research, experiments are concentrated on various weight percentages of zeolite in the soil to examine the effect of the calcined zeolite on drainage shear strength and California bearing ratio (CBR) with curing and without curing, and investigate their liquid limit and plastic limit behavior and make comparative results by fall cone (cone penetrometer) by Feng's and Wroth-Wood's methods and also the SEM images results have been presented. The results show that by increasing the percentage of zeolite in without curing samples due to the grain-intermediate filling properties and the grain agglomeration properties, the fine zeolite particles increase the soil's strength a little bit, but in the curing state due to low capacity of alkaline material, it is unsuccessful in supplying the basic environment pH > 10.5 to perform a pozzolanic reaction, but we can see a relatively higher strength toward without curing state. also, the results Show that zeolites have no plastic behavior, it can be concluded that the pozzolanic property of zeolites plays a much higher role than cementing properties which is better to combine with cement or lime and can achieve strong results much higher.

Keywords: Zeolite, SEM, CBR, California bearing ratio, direct shear, fall-cone, sandy silt

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