Department of civil engineering geotechnical engineering lab. Laterally confined compression test, also known as the triaxial compression test. The apparatus consists of a square brass box split horizontally at the level of the center of the soil. Determination of youngs modulus from direct shear test. Procedure for performing direct shear and sliding friction testing using a portable direct shear device introduction this procedure is under the jurisdiction of the materials engineering and research laboratory, code 8668180, technical service center, denver, colorado. Lecture 11 shear strength of soil ce240 slideshare.
A free powerpoint ppt presentation displayed as a flash slide show on id. The purpose of the direct shear test of soil is to obtain its ultimate shear resistance, its angle of internal friction, its cohesion, and its shear stress deformation characteristics. Chapter 5 engineering properties of soil and rock 5. Then a shear force is applied to the top half of the shear box to cause failure in the sand. Apr 16, 2015 civil engineering texas tech university direct shear test direct shear test is quick and inexpensive shortcoming is that it fails the soil on a designated plane which may not be the weakest one used to determine the shear strength of both cohesive as well as noncohesive soils astm d 3080 19. The equipment for the direct shear test consists of a square or a circular shear box made of brass or gun metal. In this video i have talked about the field conditions that affect the values of shear strength parameters like drained or undrained conditions and i.
Consolidation test determination of compression index and coefficient of consolidation. Firstly, the different total stress paths followed by dds devices that impose constant crosssectional area using a stiff external boundary, and those that use a constant total stress lateral boundary condition are explored. For this purpose triaxial tests are most appropriate. Shear envelopes obtained by direct shear tests a shear stress vs. The procedure is issued under the fixed designation usbr 6255. Mar 14, 2017 ceen 341 lecture 19 intro to shear strength and the direct shear test office hours. This paper investigates two aspect of the direct simple shear dss using threedimensional finite element analysis. The two halves of the shear box are held together by locking pins to. Advanced soil mechanics 4th edition pdf free download direct.
The box shear test, though simple in principle, has certain shortcomings which will be discussed later on. Indian institute of technology, kanpur 1 module 4 lecture 21 pore water pressure and shear strength 5 topics 1. How to download notes directly in pdf format from nptel. Direct shear test is most widely used for the determination of shear. This test is also useful to study friction between two materials, one material in lower half of box and another material in the upper half of box. The soil sample in this shear mould is loaded vertically under different vertical loads and.
Civil and environmental engineering, school of mining and petroleum engineering 2,169 views. Mine 323 uniaxial compressive strength test lab 4 duration. Class 6 shear strength direct shear test geotechnical. An an example calculation with the direct shear test is performed to develop a mohrcoulomb failure. The shear strength of soil is usually determined experimentally by one of the following methods. To facilitate the remoulding purpose, a soil sample may be compacted at optimum moisture content in a compaction mould. The 305mm 12 square direct shear was specifically designed for testing large soil sample sizes with soil and geosynthetics for testing coefficient of friction. Experimental and numerical analysis of direct shear test. In many engineering problems such as design of foundation, retaining walls, slab bridges, pipes, sheet piling, the value of the angle of internal friction and cohesion of the soil involved are required for the design. Pdf shear strength parameters from direct shear tests. The sand is placed in a shear box that is split into two halves. Then specimen for the direct shear test could be obtained using the correct cutter provided. The advanced soil mechanics 4th edition pdf free download file has been uploaded to our online repository for the safer downloading of the file.
Threedimensional finite element analysis of the direct. Civ e 353 geotechnical engineering i direct shear test 2006 page 3 of 5 department of civil engineering 8. Now the laboratory test, the laboratory test for determination of shear strength parameters, so first we will discuss about direct shear test. Shear strength of soil is basic parameter in the studies like liquefaction, slope stability and shallow foundation design, etc. The dynamic shear rheometer dsr figure 1 and figure 2 is used to characterize the viscous and elastic behavior of asphalt binders at medium to high temperatures.
An experimental and numerical investigations of the direct shear test have been performed under constant vertical stress q const and constant sample volume h const. So, directly we are trying to force the soil plane on that plane. Standard test method for direct shear test of soils under. This equation can also be written in terms of effective stresses. Flexure shear crack flexuretension crack v at formation of shear cracks is actually larger than for web shear cracks. Cone penetrometer tests test method d5778 and unconsolidated undrained triaxial compression d2850 tests are most often performed for direct comparison to. To determine the shearing strength of the soil using the direct shear apparatus. Direct shear test these are simplest and easiest of the plane shear test a soil sample of size 6cm x 6 cm x 2 cm in size is confined in a direct shear box which have 2 detachable halves of same size. In the direct shear test, the shear stresses and displacements are nonuniformly distributed within the soil specimen. Standard test method for field vane shear test in saturated.
Direct shear testing is covered in astm standard d3080, standard method for direct shear test on soils under consolidated drained conditions. In order to take into account the effect of direct shear and change in coil curvature a stress factor is defined, which is known as wahls factor k wahl s factor and is defined as where c spring index dd if we take into account the wahls factor than the formula for the shear stress becomes. In this article, our main focus will be on direct shear test. As thinner specimens are used in shear box, they facilitate drainage of pore water from a saturated sample in less time.
The most commonly used laboratory devices available to measure the strength of aggregates are the direct shear ds and triaxial tx tests, with ds being the simplest and most regularly used test. In order to promote public education and public safety, equal justice for all, a better informed citizenry, the rule of law, world trade and world peace, this legal document is hereby made available on a noncommercial basis, as it is the right of all humans to know and speak the laws that govern them. May 18, 2017 in this video i have talked about the field conditions that affect the values of shear strength parameters like drained or undrained conditions and i have also discussed the direct shear test to. Dry sand can be conveniently tested by direct shear tests. Friction angles of opengraded aggregates from largescale. B v s viswanadham, department of civil engineering, iit bombay.
Procedure for performing direct shear and sliding friction. During the direct shear test, there is a rotation of the principal stress, which may or may not model field conditions. The test results are applicable to assessing strength in a field situation where complete consolidation has occurred under the existing normal stress. Gds large automated direct shear system gdslads is an electromechanical direct shear testing device for large samples, up to 300mm square or round. As with other superpave binder tests, the actual temperatures anticipated in the area where the asphalt binder will be placed determine the. Shear strength of soil, direct shear test, merits and demerits, triaxial tests. Based on the american association of testing materials astm standards, the maximum particle sizes for ds and tx testing are 110th and 16th of. Attaullah shah shear failure soils generally fail in shear shear failure shear failure mechanism shear failure of soils soils.
Repeat steps 1 to 7 for the other two samples and apply the appropriate normal load for each. For simple beams, support reactions for statically determinant beams, relationship between bending moment and shear force, shear force and bending moment diagrams. An insitu direct shear test apparatus, in both small and large sizes, and its testing. Alternatively, sand sample can be placed in a dry state. Gds large automated direct shear system 300mm gdslads. Why does internal angle of friction vary an annular ring figure 4, subjected to a constant normal stress, is confined laterally, and ultimately caused to rapture on a plane of relative motion. Shear strength parameters from direct shear tests influencing factors and their significance. Since vane shear strength values are most always higher than field strengths for analyses 5. Pure bending theory of initially straight beams, distribution of normal and shear stress, beams of two materials.
So, because of that it is called actually direct shear test and then there is a direct shear test will be. So this direct shear and triaxial shear test on soil usually fall. This paper deals with the factors affecting the results of direct shear tests. A square box of internal dimensions 6 x 6 cm is more commonly used. Feb 01, 2015 direct shear test direct shear test is quick and inexpensive shortcoming is that it fails the soil on a designated plane which may not be the weakest one used to determine the shear strength of both cohesive as well as noncohesive soils astm d 3080 25. Mohrs stress circle, theory of failure for soils, determination of shear strength direct shear test, triaxial compression test, unconfined compression test, van shear test, shear characteristics of cohesionless soils and cohesive soils. A comparison between the shear strength measured with direct. In order to investigate the possible effects of two main factors stress level and wetting on a rockfill material, a number of mediumscale direct shear tests have been conducted with different. General configuration of the direct shear device a cross section through a typical direct shear device is shown in fig. During the determination of soil shear strength in a laboratory by different test methods soil is loaded in a different way. Civ e 353 geotechnical engineering i direct shear test. A proving ring is used to indicate the shear load taken by the soil initiated in the shearing plane. This information is necessary for substructure analyses, in determining the bearing capacity of the soil, in stability calculations of earth slopes, in pile.
Large v shear force, small m bending moment little flexural cracking prior to formation of diagonal cracks. This characterization is used in the superpave pg asphalt binder specification. Oct 09, 2019 nptel has changed the links of pdf lecture notes since august 2019. The test is carried out on either undisturbed samples or remoulded samples.
Large v shear force, large m bending moment formation of flexure cracks precedes formation of shear cracks. The influence caused by different test devices and user influences are pointed out. As such, an appropriate height cannot be defined for the calculation of shear. The test is performed by deforming a specimen at a controlled strain rate on or near a single shear plane determined by the configuration of the apparatus. Ceen 341 lecture 19 intro to shear strength and the. Now, in this section of the article, you will be able to get access to the advanced soil mechanics 4th edition pdf free download file in. The shear box is split into two halves, along the horizontal plane, at its midheight. Nevertheless, direct shear tests are mostly performed to determine the shear strength of soils. Image shows the shear machine with a pc, which is not included in the standard specification.
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