Laboratory Testing
Knowing the prevailing ground conditions acts as an important basis when it comes to planning, building, and constructing infrastructure projects. As such, it becomes important to ensure that a geotechnical investigation gets carried out. Such an investigation is bound to include various lab tests.
Conducting Laboratory Testing within the Investigation
Laboratory testing involves completing the following sets of tests:
Index Property Tests
The main purpose of this type of testing is to determine a soil classification. Here, the following are considered:
• Soil moisture content—it aims to determine the moisture content in the soil in relation to the overall percentage of the soil’s oven-dried weight.
• Particle size distribution—it looks at the size of the particles present in the soil as well as their overall distribution.
• Unit weight—determining the overall dry and moist densities of the soil samples in terms of their unit weights.
• Attenberg limits—determining the plasticity, liquid index, and plastic limit indexes of the samples
• Specific gravity—looking at the soil gravity of soil samples that can pass through the 4.75mm sieve
Engineering Property Tests
The second set of tests are known as engineering property tests. Their purpose is to determine the deformation and strength parameters.
Lab tests conducted under this cluster include:
• Consolidated undrained triaxial compression—it involves looking at the stress and strength relationships pertaining to the cohesive soils when the soil samples get sheared during compression. It is something that occurs without any kind of drainage getting observed. Information from the first compression set is then used in geotechnical engineering analysis. The purpose of this analysis is to help determine how this material will react when used in large scale applications. A good example would involve looking at how a soil specimen will perform when placed on a slope. The soil can either support the stresses applied by the slope or collapse under its sheer weight. Undrained compression exams have to occur alongside other tests to assist in determining how the soil will behave when large scale engineering applications are put into work.
• Consolidation tests—it seeks to look at the consolidation rate as well as the magnitude of the consolidation when the soil gets drained in an axial manner or laterally restrained. Information obtained during these tests is applied when estimating the total settlement or differential rate of an earth hill or structure. Such estimates are important when evaluating the performance and design of engineering structures.
• Unconfined compression strength—determining the unconfined compressive strength of soil based on its axial load.
Rock Strength Property Testing
Two types of test are conducted here. They include:
• Uniaxial compression strength test—used to establish the unconfined compressive strength related to intact rock core samples.
• Point load test—used to establish the paint load strength related to a given rock index
Chemical Analysis of Earth/Ground Water
Last but not least is the chemical analysis test. The test seeks to look at the chemical composition of groundwater.
• Chloride content, sulfate content, and pH value tests—it is a test that seeks to look at the aggressiveness of groundwater to steel and concrete structures.
Summary
When the laboratory testing process comes to an end, a detailed report gets prepared by the project investigator. The tailor-made report will look at different aspects of each test depending on the project scope. The investigator will normally use a standard table of content when preparing the report. The table will list the description of tests performed including the report derived from each of the tests conducted above. It is important to pay attention to each aspect of the report to gain a better insight.
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