What is Geotechnical investigation?
Before any measure for design and construction or strengthening of civil or industrial structures and also obtaining enough primary information in order to Feasibility and economic estimates to present proposals for projects, it is necessary to provide geology and geotechnical investigation with sufficient accuracy. Geotechnical investigation consists of information about engineering and physical properties of soil in the intended area. This information obtained by engineers using numerous in-situ and laboratory tests. Geotechnical and soil mechanics investigation should be collected by experienced experts in collaboration with geotechnical engineers and geologists.
ASACO engineering company with its laboratory and in-situ equipment tests and also experienced experts in soil and geology field, is able to do all experiments and geotechnical investigations in accordance with modern standards in world.
Geotechnical investigation cost
In foundation and soil engineering subjects, soil investigation is essential for a safe and economical design. The cost of this operation depending on the type of project is about 0.5-1% of the total project cost.
The reason of geotechnical investigation importance
An Accuracy and suitable design for civil and industrial projects on the ground or buried in the ground, needs to accurate and sufficient knowledge from soil subsurface conditions and groundwater location in intended site. As noted, the cost required for these investigations is only a partial part of the whole project cost and eliminating it, results in much higher costs. Because in case of encountering with unforeseen problems, it is necessary to review the completed designs and replace them with new plans. Also, in many cases ignoring the geotechnical and geological investigations has resulted to collapse during excavations or constructions and caused Irreparable financial and human losses. All these cases show the importance of geotechnical investigation before any measures for projects construction.
Necessary items in geotechnical investigations
For doing subsurface soil identifications, following items are necessary:
Area, depth and thickness recognizability for each layer to the depth range involved in structure construction and its loading.
Determine the depth and bedrock characteristics such as lithology, joints spacing, fault existence, weathering and crushed area.
Engineering properties of stone and soils in site, such as shearing resistance, permeability and compressibility.
Groundwater location and its changes and also existence and determination of artesian pressures.
Information obtained from geotechnical investigation
According to analysis of information obtained from the relevant experiments in each project, the following should be clearly appreciable:
– Determine the type of soil strengthening
– Determine the groundwater level in project site in different seasons
– Determine the allowable bearing capacity of shallow and deep foundation
– Estimate the settlements that will be created in foundation
– Determine the foundation type and estimate its dimensions
– Identify problems of adjacent structures and resolve them with suitable methods
– Identify environmental problems and its solutions
Geotechnical investigation sequences
Identifications related to geotechnical investigation are performed as follows:
Geotechnical investigation methods
Identification operation consists of direct and undirect methods. In direct methods, drilling, boring and exploratory holes and in indirect methods aerial and satellite pictures are used to identify region.
Drilling and boring
exploratory holes could be made by hand and mechanical tools, but the use of mechanical methods is more common.
The first method for drilling Exploratory holes was to excavate using a pick and shovel. But due to economics and saving time, today, drilling is done using power equipment and machinery and then the sampling is done by hand tools for in-situ and laboratory tests.
For numerous borings to greater depths and collect undisturbed samples, the only practical method is to use power equipment. the Methods of Drilling using power drills are as follows:
– Wash boring
– Rotary drilling
– Continues-flight auger
– Percussion drilling
some engineering properties of soil is Determined using laboratory tests. After completion of sampling, the required tests are performed on samples. Resistance, compressibility and permeability of soil are among the most important properties of soil that are determined from results of tests on undisturbed samples. obtaining an undisturbed sample is usually difficult. So, an undisturbed sample is defined as a sample that has the least amount of disturbance. Other properties of soil are obtained by primary tests.
ASACO engineering company is one of the pioneer companies in performing geotechnical investigation, in-situ and laboratory tests of soil with modern equipment and experienced experts of country. Laboratory and in-situ tests are as follows:
Laboratory tests of ASACO
– primary tests (soil particle size distribution, Atterberg limit, moisture content, compaction, unit weight)
– Triaxial compression test
– Direct shear
– Uniaxial compression test
– Chemical tests
– Point load test
A part of soil identification is done by laboratory tests. But usually due to following reasons, the results of these tests are not enough lonely:
– It is difficult to take completely undisturbed samples with high quality for laboratory tests
– It is impossible to generalize the results of laboratory tests to whole soil mass in site
– due to limitations of Laboratory equipment, providing a situation similar to real situation in site is difficult and, in some cases, impossible.
According to items above, today, in-situ tests has become very important in geotechnical investigations and most of the geotechnical measures is done in accordance with these tests.
The most common in-situ tests consist of standard penetration test, cone penetration test and vane shear test. tests such as dilatometer test, pressure meter test and plate load test are other in-situ tests.
In-situ tests of ASACO
– Standard penetration test
– In-situ direct shear test
– Vane shear test
– Pressure meter test
– Plate load test
– Geophysics tests