We offer a comprehensive UKAS accredited advanced testing service at Igne and can deliver all types of in-situ geotechnical engineering testing services.
The term advanced testing can be interpreted in different ways, it usually generally relates to tests which include triaxial testing, consolidation, permeability, shear box and effective stress.
All of these tests are interlinked in some way and are all used in conjunction with each other. The advanced tests are very important for engineering purposes and give the engineer/client an idea of how the soil will react under certain loadings and pressures over long periods of time.
This is particularly important in engineering considerations such as bearing capacity, slope stability, foundation design amongst others.
We offer a comprehensive UKAS accredited advanced testing service at Igne and can deliver all types of in-situ geotechnical engineering testing services, including:
This test can be carried out on undrained specimens, where it is tested under all round pressure to simulate that under which the soil would be naturally. The sample is then placed under stress at pre-determined load(s) at a specific rate of strain. The results that are obtained are then used to calculate the shear strength, deviator stress(as) at failure and strain(s) at failure.
Used to determine the hydraulic conductivity (coefficient of permeability) of water saturated porous materials. Essentially, used to measure the rate at which the soil allows water to flow through it. Soil permeability depends on the type of material, grain structure and the void spaces in the soil. The duration of the test is also dependent on the above factors.
Common uses for these tests is to assess materials used in landfill clay liners or dam stability.
The shear box test is used to determine the peak effective shear strength parameters of soils it is also known as a direct shear test. There are two common sizes of shear box – small (nominally 60mm x 60mm) which is appropriate for material types <2mm and large (nominally 300mm x 300mm) and suitable for material <20mm in size. This test is often used in slope stability design.
Ground movements and instabilities can be caused by changes in total stress (such as loading due to foundations or unloading due to excavations), but they can also be caused due to changes in pore pressures (slopes can fail after rainfall increases pore pressures).
It is the combined effect of total stress and pore pressure that controls soils behaviour such as shear strength, compression, and distortion. The difference between the total stress and the pore pressure is called the effective stress. For these reasons, the results produced in this type of testing are particularly useful in foundations design.
When a soil is in-situ and pressure is placed on it, the pore pressure increases (pressure caused by moisture in the pores in the soil being squeezed out). Pore water leaves the soil and the solid material fills the voids left. This process is called consolidation; it takes time over which the settlement of the soil decreases.
The test itself can be explained thus: A cylindrical specimen of soil is enclosed in a metal ring to prevent lateral movement. The load on the specimen is increased the thickness of the sample changes over time. This means we can monitor the compressibility of the soil.
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