Geotechnical investigation
Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. This type of investigation is called a site investigation.[1] Additionally, geotechnical investigations are also used to measure the thermal resistivity of soils or backfill materials required for underground transmission lines, oil and gas pipelines, radioactive waste disposal, and solar thermal storage facilities.[2]
Importance
Geo technical Investigation is very important before any structure is built - whether it is a dream house, an industrial shade, a multiplex, a shopping mall, a warehouse, a multi storeyed building or even small and big infra projects like bullet train. metros and so on.[3] There are many organizations like ACTS and Durocrete construction material testing lab and Geo-Engineering firm who carry out the Geo-technical investigation world wide with their own team of experts - man and machine.
Soil Sampling
Borings come in two main varieties, large-diameter and small-diameter. Large-diameter borings are rarely used due to safety concerns and expense but are sometimes used to allow a geologist or an engineer to visually and manually examine the soil and rock stratigraphy in-situ.[4] Small-diameter borings are frequently used to allow a geologist or engineer to examine soil or rock cuttings or to retrieve samples at depth using soil samplers, and to perform in-place soil tests.
Laboratory Tests
A wide variety of laboratory tests can be performed on soils to measure a wide variety of soil properties. Some soil properties are intrinsic to the composition of the soil matrix and are not affected by sample disturbance, while other properties depend on the structure of the soil as well as its composition,[5] and can only be effectively tested on relatively undisturbed samples. Some soil tests measure direct properties of the soil, while others measure "index properties" which provide useful information about the soil without directly measuring the property desired.[6]
Geophysical Exploration
Geophysical methods are used in geotechnical investigations to evaluate a site's behavior in a seismic event. By measuring a soil's shear wave velocity, the dynamic response of that soil can be estimated.[7] There are a number of methods used to determine a site's shear wave velocity:
- Crosshole method
- Refraction microtremor (ReMi)
- Surface wave reflection or refraction
- Spectral analysis of surface waves (SASW)
- Multichannel analysis of surface waves (MASW)
- Downhole method (with a seismic CPT or a substitute device)
- Suspension logging (also known as P-S logging or Oyo logging)
References
- ↑ Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils
- ↑ Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils
- ↑ Standard Practice for Thin-Walled Tube Sampling of Fine-Grained Soils for Geotechnical Purposes
- ↑ Geotechnical services, CBR testing, Plate bearing test | IBEX Consulting Engineers
- ↑ Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
- ↑ Standard Test Method for Expansion Index of Soils
- ↑ Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials
