Soil mechanics testing is a fundamental element of geotechnical engineering. It is used to obtain information on the physical properties of soil used in earthworks and foundations, as well as the stress applied to these structures by surface and subsurface conditions. Soil mechanics provides the theoretical basis for analysis of soils in geotechnical engineering. These tests are used to analyze the deformation of the soil and the flow of fluids within natural and man-made structures that are supported on or made of soil, including structures that are buried in soils. Example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems. The principles of soil mechanics are also used in related disciplines such as engineering geology, geophysical engineering, coastal engineering, agricultural engineering, hydrology and soil physics.
Humboldt’s soil mechanics section on this website and in our catalog covers the following testing procedures: consolidation, direct and residual shear and triaxial testing. It also includes Humboldt’s data acquisition devices, accessories and software.
Soil Consolidation Testing
Consolidation testing is a fundamental part of any soil mechanics testing program. It is a process in which a soil sample undergoes a volumetric change due to the application of some type of loading. Placing a load on a soil sample results in a reduction in the void space within the soil. In the laboratory, this load can be applied pneumatically or by simply placing weights on the sample. This process simulates the effects of real-world forces placed on soil whether from simple compaction or building structures on the soil. Incremental consolidation tests can be conducted by applying load increments to a soil sample for predetermined lengths of time. Generally, the load increments are arrived at by doubling the previous load.
The reason for performing incremental consolidation tests may vary, however in most cases, the test is done to determine settlement properties of a particular soil. For example, when a building is constructed, the underlying soil is impacted by the load that has been applied and expels water from its voids. As water is expelled, the soil starts to settle, which affects the building above. In this scenario an engineer is interested in the magnitude and rate of settlement. In some cases a building load may cause the soil to settle a number of feet. A consolidation test predicts the amount and rate of settlement. Consolidation testing is covered under ASTM D2435 and D4546, as well as AASHTO T216.
Humboldt Consolidation Solutions:
Humboldt provides an extensive offering of consolidation testing equipment to satisfy the needs of any soils testing laboratory.
Humboldt ConMatic IPC— The HM-5470.3F is a fully-automated, incremental pressure controller for performing consolidation and one-dimensional swell tests, which run automatically, freeing up technicians for other tasks and significantly reducing testing time.
Humboldt Pneumatic Consolidation Machine— The HM-5432.3F is a compact and easy-to-use, pneumatic consolidation load frame is used to estimate the rate and amount of settlement anticipated for a proposed structure. The unit applies loads instantly without impact for stress-controlled consolidation testing.
Humboldt Dead-Weight Consolidation Frame— The HM-1100A is a reliable, heavy-duty consolidation frame for dead-weight determinations of soil consolidation.
Humboldt Consolidation-Specific Software— Humboldt provides our NEXT software in a consolidation-specific application, which provides consolidation-specific setup, operation and control of the consolidation testing process with our testing machines. This software also provides extensive presentation and reporting capabilities
Humboldt Consolidation Cells— Humboldt provides consolidation cells in Fixed Ring, Floating Ring and Fixed Ring Permeability configurations. We also provide weights for dead-weight setups and a complete offering of consolidation accessories and replacement parts for machines and cells.
Direct Shear Soil Testing:
The direct shear test plays an important part in soil mechanics testing and is a method for determining the consolidated drained shear strength of soils. The direct shear test is performed by placing a vertical load on the sample which is in a horizontally split box. After the vertical load has consolidated the sample, the two halves of the box are “pulled” apart relative to each other, which causes a shear load to be measured on a load measuring device. Once the soil has been sheared to its shear strength, there is failure and the load rapidly drops off. This procedure is repeated (usually three times) under different vertical loads. A “failure envelope” can then be drawn on a graph, which allows engineers to design slopes, dams, foundations, etc.
The direct shear test is used to assess what soil strength might be in a field situation where complete consolidation has occurred under the existing normal stresses. Failure is reached slowly under drained conditions so that excess pore pressures are dissipated. The results from several tests may be used to express the relationship between consolidation stress and drained shear strength. Direct shear testing is often used when trying to determine the shear strength of sandy materials.
Direct shear devices can also be used to measure residual shear strength. Residual strength is the shear strength of the material that is exhibited after a failure (exceeding of initial shear strength) has occurred. Residual shear strength testing is very important in earthquake prone areas. Direct Shear testing is covered under ASTM D30805 and AASHTO T236.
Humboldt Direct Shear Solutions:
Humboldt Automated, Pneumatic Direct Shear Machine— The HM-5760.3F is an automated, pneumatic-loading direct/residual direct shear machine, which utilizes pneumatic loading to automatically apply vertical loads to a soil sample, eliminating the need for loading weights.
Humboldt Semi-Automatic Direct Shear Machines— The HM-5755.3F provide direct shear testing utilizing pneumatic loads, which are controlled by manual valve controls located on the front panel for easy use. It provides the same features as the HM-5760.3F except that loads are applied manually.
Humboldt Dead-Weight Direct Shear Machines— The HM-5750 Series of Dead-weight Direct-shear machines, come in three configurations — analog, digital and manual gauge measuring devices. These machines feature Humboldt’s touch-screen monitor for test control.
Humboldt Direct Shear-Specific Software— Humboldt provides our NEXT software in a direct shear-specific application, which provides direct shear-specific setup, operation and control of the direct shear testing process with our testing machines. This software also provides extensive presentation and reporting capabilities
Humboldt Shear Boxes, Accessories and Replacement Parts— Humboldt provides shear boxes in both round and square configurations. We also provide weights for dead-weight setups and a complete offering of direct shear accessories and replacement parts for machines.
Triaxial Testing for Soils:
As part of a soil mechanics testing regiment, Humboldt Triaxial Testing Systems provide state-of-the-art systems specifically designed to control and monitor triaxial testing, such as: unconsolidated undrained (UU), consolidated undrained (CU), unconfined compression (UC), consolidated drained (CD) tests. These tests cover the following ASTM standards: ASTM D2850, ASTM D2166 and ASTM D4767. Humboldt provides an extensive selection of load frames, which can be used in triaxial testing applications. Humboldt’s Elite Series Load Frames provide the materials testing lab with a choice of three, highly-versatile and precision-built loading systems covering a range of testing applications.
The HM-5030 Masterloader is the workhorse of the group, capable of handling any testing need up to 50kN or 11,000 lbf.
The HM-5020 Triaxial Loader is a machine designed specifically for triaxial testing and other testing requirements up to 15kN or 3,000 lbf.
The HM-5040 Grand Loader is a heavy-duty machine capable of handling testing requirements up to 100kN or 22,000 lbf.
Humboldt also provides the HM-2850 Multi-speed Loader, a simple, multi-purpose load frame that can be used for triaxial testing. It is designed for those who want a high-quality load frame without built-in data acquisition capabilities or digital control accessories.
Also available are our Triaxial Distribution Panels in both automated and manual configurations. Used in conjunction with the HM-5240.3F pressure controller, Humboldt automated control panels provide an accurate and easy-to-operate solution for providing the controls necessary for distributing compressed air, water, de-aired water and vacuum within an air/water bladder-type triaxial testing system.
We also offer our FlexPanels, which provide an accurate and easy-to-operate solution for controlling compressed air, water, de-aired water and vacuum without the need for air/water bladder interfaces to produce the pressures necessary for triaxial testing. FlexPanels utilize a set of three burettes to control cell, top cap and base pedestal pressures for a triaxial cell and can be configured to handle up to 6 triaxial cells.
Complete triaxial sample prep and triaxial test consumable items are also available here. These products can help in test setup, as well as keeping your triaxial testing program running without interruption.
Software:
Humboldt’s NEXT software provides test-specific software programs for soil mechanics testing applications. These programs include test software for Consolidation; Direct Shear; Unconsolidated Undrained (UU), Consolidated Undrained (CU); Unconfined Compression (UC) and Consolidated Drained (CD). This software provides machine control, calibration, monitoring and report generation for soil mechanics testing.
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