8.5.3 INTERPRETATION
Comment on the properties of the soil
GENERAL REMARKS:
This test is useful when the soil is soft and its water content is near liquid limit.
The following precautions are necessary when using field vane shear tests:
1. The vane must be rotated soon (within 5 minutes) after insertion into the depth to be tested as delays of one (1) hour to one day may lead to overestimation of strength by 10% to 20% respectively.
2. Standard rate of rotation is 6 degrees per minute.
3. Correct calibration chart for the torque and right vane size must be used.
9.0 DIRECT SHEAR TEST Standards ASTM D3080; BS 1377
9.1.1 Objective
Laboratory determination of the shearing strength of a soil using the direct shear method
9.1.2 …show more content…
The concept is used by geotechnical engineers in estimating the bearing capacity of foundations and in assessing the stability of retaining walls, slopes and embankments and the design and construction of highway and airfield pavements. The shear strength of a soil can be regarded as its intrinsic capacity to resist failure when forces act on the soil mass. The strength is a function of the type as well as the physico-chemical make-up of the soil.
Soils generally fail in shear. At failure, shear stress along the failure surface (mobilized shear resistance) reaches the shear strength, Holtz and Kovacs (1981). The soil grains slide over each other along the failure surface. No crushing of individual grains. At failure, shear stress along the failure surface (t) reaches the shear strength (tf). Using the Mohr – Coulomb criterion, Figure 10.1, we have in terms of effective stresses that 9 where = shear strength, the maximum shear stress the soil can take without failure, under normal effective stress of s’ = effective …show more content…
A constant strain rate is applied to a single shear plane under a normal load, and the load response is measured. If this test is performed with different normal loads, the common shear strength parameters can be determined. The soil is sheared along a predetermined plane by placing it in a box and then moving the top half of the box relative to the bottom half. The box may be square or circular in plan and of any size. However, the most common shear boxes are square, 60 mm x 60 mm. A load normal to the plane of shearing may be applied to a soil specimen through the lid of the box. Provision is made for porous plates to be placed above and below the soil specimen. The direct tests are usually performed by placing the soil sample in a shear box which is split into two halves, Figure
Comment on the properties of the soil
GENERAL REMARKS:
This test is useful when the soil is soft and its water content is near liquid limit.
The following precautions are necessary when using field vane shear tests:
1. The vane must be rotated soon (within 5 minutes) after insertion into the depth to be tested as delays of one (1) hour to one day may lead to overestimation of strength by 10% to 20% respectively.
2. Standard rate of rotation is 6 degrees per minute.
3. Correct calibration chart for the torque and right vane size must be used.
9.0 DIRECT SHEAR TEST Standards ASTM D3080; BS 1377
9.1.1 Objective
Laboratory determination of the shearing strength of a soil using the direct shear method
9.1.2 …show more content…
The concept is used by geotechnical engineers in estimating the bearing capacity of foundations and in assessing the stability of retaining walls, slopes and embankments and the design and construction of highway and airfield pavements. The shear strength of a soil can be regarded as its intrinsic capacity to resist failure when forces act on the soil mass. The strength is a function of the type as well as the physico-chemical make-up of the soil.
Soils generally fail in shear. At failure, shear stress along the failure surface (mobilized shear resistance) reaches the shear strength, Holtz and Kovacs (1981). The soil grains slide over each other along the failure surface. No crushing of individual grains. At failure, shear stress along the failure surface (t) reaches the shear strength (tf). Using the Mohr – Coulomb criterion, Figure 10.1, we have in terms of effective stresses that 9 where = shear strength, the maximum shear stress the soil can take without failure, under normal effective stress of s’ = effective …show more content…
A constant strain rate is applied to a single shear plane under a normal load, and the load response is measured. If this test is performed with different normal loads, the common shear strength parameters can be determined. The soil is sheared along a predetermined plane by placing it in a box and then moving the top half of the box relative to the bottom half. The box may be square or circular in plan and of any size. However, the most common shear boxes are square, 60 mm x 60 mm. A load normal to the plane of shearing may be applied to a soil specimen through the lid of the box. Provision is made for porous plates to be placed above and below the soil specimen. The direct tests are usually performed by placing the soil sample in a shear box which is split into two halves, Figure