What is Soil Investigation? Geotechnical Methods Used in Soil Investigation

Geotechnical Methods

Many engineering applications are done during the of a building. Also, some engineering work must be carried out on the ground before the building is constructed. It is possible to predict the effects of the earthquake on the ground in which the building will be constructed. Therefore, we can obtain how the building behaves during an earthquake. This estimate can only be revealed by geological and geophysical studies. In this way, what kind of damage the building will receive during an earthquake is determined in advance. This allows us to a building according to the ground we have. A ground survey is simply a study that allows us to understand the response of the ground during an earthquake. The  used in soil investigation also provide us the necessary physical parameters.

First of all, geophysical methods are applied during field studies, while geomechanical methods can be applied both in the field and in the laboratory. Many geomechanical tests are carried out in the field to obtain quick and practical results.

Second, the geological maps of the region are examined before the field study. As a result of this examination, the geology of the region is revealed. This allows us to get some ideas first. The geology of an area gives us information about ground layers and possible faults. Besides, geological studies allow us to understand the mineralogical of the rocks that form the ground.

Another important data source is seismic data. Possible active fault maps close to the research area should be examined. Because earthquakes in the past are also an important source of data. 

Thus, we should say that geotechnical methods used in soil investigation should be determined properly.

Geomechanical Applications Are Important Geotechnical Methods Used In Soil Investigation

Geomechanical applications are significant geotechnical methods used in soil investigations. Geomechanics provides an understanding of the mechanical properties of the ground. For this, the compressibility and strength properties of the ground are important. 

Standard Penetration Test

The compressibility of the soil can be determined by this test. A hollow cylinder is hammered into the ground. Then, a certain number of strokes are made to the soil through this cylinder. There should be a ratio between the blows struck from above and the amount of soil compaction. The number value obtained gives us the penetration resistance of the soil. The strength of the floor and its pressure resistance are also among the information obtained.

This experiment is done to understand the interaction of grains of geological units in the ground. Thus, the movement of water between the ground grains is observed. A relationship is established between the water permeability and grain size of the rock units in the ground. The sample taken from the ground is squeezed between two porous rock units in the laboratory. As a result of the test, the shortening of the sample after the compression of the soil material is detected. After all, comments can be made about the relationship between water and porosity.

This method is a significant application among important geotechnical methods used in soil investigation. It is done to understand the water content in the samples taken from the ground. After the vertical pressure is applied to the sample, the behavior of the material is examined. In the analysis here, the dry and wet weights of the soil sample are important.

Water content in the ground reduces internal friction forces. This causes the S waves emerging during the earthquake to reach a great destructive force on the ground. 

Geophysical Applications Are Compulsory Among Geotechnical Methods Used In Soil Investigation

Geophysical applications are the most important methods among geotechnical methods used in soil investigation. Geomechanical methods might give us important details and features about the ground. However, these pieces of information are constrained by geological estimates. Besides, these tests are restricted by shallow . On the contrary, the geophysical methods suggest engineers certain pieces of information for shallow and deep layers. 


Seismic methods are mostly applied in engineering geophysics. Oil exploration, , and other engineering purposes can be handled by seismic methods. The seismic method is applied by sending seismic signals beneath the ground. These signals reflected from the ground's layer. Obtained signals are recorded by geophones located on the ground. Each record received by geophones then calculated by basic physical equations. 

Seismic signals give information about the layers beneath the ground. This information includes S and P waves which suggest some ratios about the ground. These ratios are Young modulus, Poisson ratio, bulk modulus, shear modulus, and the density of the ground. Each parameter is calculated by seismic data. 

Parameters derived from seismic data show the detachability, compressibility, porosity, strength, stiffness, and non-compressibility characteristics of the ground. In addition to these features, the ground coefficient is calculated and the shaking conditions that may occur during an earthquake are defined.

Wave speeds give us an idea of the bearing capacity of the ground. The data obtained from geomechanical experiments also have an important place here.

Geophysical methods must be used as an application of geotechnical methods used in soil investigation. Because geophysical engineering allows us to see and predict what cannot be seen and unpredictable under the ground. No method is as useful and precise as geophysical methods.

Gathering Geotechnical Methods Used In Soil Investigation

Gathering the data obtained by geotechnical methods used in soil investigation takes an important place in the ground surveys. Although geophysical methods give precise and consistent results, they should be interpreted together with geomechanical methods. Correlation between the data is expected. However, errors may occur due to human influence. Therefore, the results of the two disciplines are correlated and presented to civil engineers. Civil engineers design the building according to the condition of the ground. The important point here is that the communication between different disciplines must be continuous. Soil investigations are indispensable studies for civil engineering. This reason should be pursued meticulously. Otherwise, loss of life will be high in a possible earthquake.

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