Evaluation of the location and laboratory tests are two of the most critical aspects of any construction and mining project and have a direct impact on the technical feasibility and optimization of project costs. Geotechnical data is the information related to land that is used in planning, exploration, design, construction, and operation of engineering structures and civil and mining projects and ensures their effective safety and efficiency. This information includes a wide range of data, in the fields of soil mechanics, rock mechanics, water resources, seismicity, civil engineering, and geology. Geotechnical studies are local surveys of general geology, soil characteristics, and groundwater levels, and in particular should determine the presence and depth of problematic soils. Technical recommendations on the type of foundation, allowable strength of the soil under the foundation, the expected settlements, and design parameters of retaining walls are other essential parts of the soil mechanics report. One of the undeniable necessities of the designer and executor of the project in designing and executing any kind of geotechnical operations is to conducting detailed studies. At the geotechnical design of each structure, allowable strength, settlement coefficients, elasticity coefficient and soil resistance and seismic parameters are determinant and the achievement of this information is not possible except with detailed geotechnical studies.
Soil shear strength is the main factor in determining soil behavior. Soil shear strength is the internal strength of the unit of the soil surface, which can be expressed to withstand rupture and slippage along any inner plate.
In urban projects, the use of supplementary soil mechanics studies, which mainly focuses on in-site experiments, reduces the costs of the project implementation and increases the safety of excavations and geotechnical projects.
The main purpose of the in situ shear test
In-site experiments are of great importance in geotechnical and soil mechanics studies. The reason for this is that the soil and rock are intact in situ situation, which will lead to more accurate results.
By conducting accurate field experiments and benefiting from the exact soil characteristics of the project site, a clear view of the optimal design of the desired structure can be achieved. By correctly defining the local soil type classification, project time and cost are saved.
Two commonly used in situ experiments:
Plate Load Test:
This experiment is one of the most widely used experiments in geotechnical studies. The the results of this experiment are used in the design of the foundations of structures and the estimation of settlement after the construction of the structure. In this experiment, an attempt is made to determine the strength and hardness of the ground according to the type of project site. Of course, building a foundation with real size and loading it is undoubtedly the best way to determine the strength of the ground, but due to some problems such as the high cost of building a foundation of real size, etc., this is not desirable. In this case, by performing the experiment on a small screen and generalizing the results, the desired features and results can be obtained.
In-situ Direct Shear Test:
In situ direct shear test is used to determine the maximum shear strength of soil in situ as a function of the stress perpendicular to the shear surface. To perform the experiment, three soil cubes with dimensions of 60 × 60 × 30 cm in the floor of the galleries dug in the trench are prepared. The intactness of the soil despite the presence of rubble in the soil must be carefully considered. Each of these 9 samples is then completely enclosed by a metal mold. The surface roughness of the sample is eliminated using local soil and its surface is leveled. In this experiment, a vertical jack with a capacity of 60 tons and a horizontal jack with a load capacity of 60 tons with a displacement of 7 cm are used. It should be noted that in the in situ shear test, the internal friction angle and soil adhesion are similar to the in vitro direct shear test, although the results obtained from the in situ test are much more accurate because of the use of a larger intact specimen.
Other in-site tests include:
Dutch Cone Penetration Test
Pile Loading Tests
Pull Out Tests and Anchorage Tests
Concrete Ultrasonic Test
Geophysical tests including Geoelectric and Down Hole test
Peyban Geotechnical Services Company
Peyban Company, while having the technical equipment of field operations, in-situ tests, as well as the technical services of laboratory tests, is ready to cooperate and provide specialized services in the field of performing laboratory tests throughout Iran.