Ground survey ensures that building safety is addressed through accurate site assessment at the very first stage of the construction process. The structure of the ground directly affects many decisions, from project design to foundation selection.
For this reason, technical examination of land conditions before starting construction is important for a construction process that is both safe and in compliance with the legislation.
What is Soil Survey?
Soil survey is the process of technically examining the geological and geotechnical properties of the land on which the building will be built. With this study, the bearing capacity of the ground, ground water level, soil class, liquefaction risk and conditions affecting the foundation design are determined. The data obtained is very important in terms of designing the structure in accordance with the ground and choosing a safe foundation system.
The report prepared as a result of the ground survey directly affects both the architectural aspect and the engineering and security aspects of the construction project. For this reason, the technical characteristics of the ground must be evaluated before starting construction in new buildings, urban transformation, apartments, villas or projects of different scales.
How to Perform a Soil Survey?
Soil investigation is a technical process that progresses through field studies, laboratory tests and engineering evaluations. Soil and Foundation Survey Application Principles and Report Format published by the Ministry of Environment, Urbanization and Climate Change, these studies; It is based on preparation by taking into consideration field surveys, laboratory studies, groundwater data, local earthquake effects and engineering properties of ground units.
The process usually proceeds with these steps:
- First of all, the location of the land, zoning status, project type and building features are examined.
- By drilling in the field, the structure of the ground at different depths is investigated.
- Samples are taken from the ground and necessary field tests are carried out.
- The samples taken are examined in the laboratory and the strength, firmness, water content and bearing capacity of the soil are evaluated.
- Data concerning building safety, such as groundwater level, liquefaction risk and earthquake effects, are analyzed.
- All the information obtained is interpreted from an engineering perspective and a soil survey report is prepared, which will be the basis for the foundation design.
In the annexed principles of the Turkish Building Earthquake Regulation, it is stated that soil and foundation studies may consist of two parts: Data Report and Geotechnical Report. For this reason, ground survey should be considered as a comprehensive engineering study in which the necessary technical data is collected and reported for the safe project design of the structure.
What is a Soil Investigation Report?
The soil survey report is a technical document that shows the suitability of the ground for construction as a result of land investigations and laboratory tests. The report includes engineering recommendations for the bearing capacity of the ground, ground water level, soil class, liquefaction risk and foundation design. This report is taken into consideration to prepare the construction project safely and in accordance with the legislation.
How many days does it take for the Soil Investigation Report to be issued?
Preparation time of the ground investigation report; It varies depending on the size of the land, number of drillings, ground structure, laboratory tests to be performed and project scope. Field work and sampling can often be completed within a few days; However, it is possible for the process to be prolonged due to laboratory analyses, technical evaluation and reporting stages.
In small-scale projects, you can get the report in a shorter time. Additional inspections may be required in large parcels, multi-storey buildings or areas where ground conditions are risky. Therefore, to find out the exact duration, you need to evaluate the authorized company you will work with, the municipal processes and the technical features of your project.
What Tests Are Performed in Soil Investigation?
The tests to be carried out in the ground survey are determined according to the ground structure of the land, project type, building characteristics and risks in the field. It is stated in the Soil and Foundation Survey Reports Format and Application Principles that field tests, laboratory tests, groundwater measurements and geophysical studies can be used to determine soil properties. In addition, the tests must be carried out in accordance with Turkish standards or internationally accepted standards. The main tests and examinations used in this process are:
- Drilling works: The distribution, physical and mechanical properties of soil units at different depths are examined.
- Standard penetration test (SPT): Data is obtained about the firmness, density, consistency and engineering properties of the soil.
- Cone penetration test (CPT/CPTU): In soft clay, silt and sandy soils, the soil profile can be determined in more detail.
- Pressuremeter experiment: The stress-deformation relationship, bearing capacity and settlement behavior of the soil are evaluated.
- Groundwater measurements: The water level is determined, which can affect the foundation design, excavation process and structure safety.
- Soil classification and grain size analysis: It is determined what structure the ground consists of, such as sand, clay, silt and gravel.
- Atterberg limits and water content tests: The consistency, plasticity and water behavior of fine-grained soils are examined.
- Shear box, triaxial pressure and unconfined pressure tests: The shear strength and bearing capacity of the soil are evaluated.
- Oedometer / consolidation test: The settlement potential and compressibility properties of the soil are determined.
- Permeability experiments: Water permeability and drainage behavior of the ground are measured.
- Geophysical measurements: Additional data is obtained on the continuity of soil layers, wave speeds and local ground conditions.
Is Soil Survey Mandatory?
Soil survey is mandatory for buildings and building-type structures. In the principles of practice published by the Ministry of Environment, Urbanization and Climate Change, it is stated that ground and foundation surveys are mandatory for the design, project planning, construction and inspection of buildings and building-like structures. For this reason, if a new structure is to be built, the properties of the ground, its bearing capacity, groundwater status and earthquake effects should be technically examined.
How Many Years is the Soil Investigation Report Valid?
There is no fixed year period for the validity of the soil investigation report to be applied in all cases. Availability of the report; It is handled according to whether the current status of the land has changed, the scope of the project, the municipality's evaluation and current legislation. The report may need to be updated in case of excavation on the parcel, changes in the construction in the surrounding area, changes in the ground water level, revision of the project or new regulation provisions.
Since ground investigation is a technical process that directly affects building safety, it should be carefully evaluated before starting construction. A correctly prepared ground investigation report; It helps you make safer decisions in terms of foundation selection, project design and construction in accordance with the legislation.
Frequently Asked Questions
Can construction be done without ground survey?
It is not appropriate to start the construction process in buildings and building-like structures without a ground survey. Soil investigation is one of the mandatory technical studies taken into consideration for building permit and safe foundation design.
Who does the ground survey?
Soil investigation is carried out by authorized teams consisting of geological engineers, geophysical engineers and engineers specialized in geotechnical fields. Since field studies, tests and technical evaluations require expertise, the process must be carried out by authorized individuals and companies.
How many meters is the ground survey done?
Drilling depth in ground survey; It is determined according to the type of building, number of floors, foundation system and ground properties. For this reason, instead of talking about a fixed depth for each project, engineering calculations and relevant standards are taken as basis.
Does ground survey indicate earthquake risk?
Ground survey provides important information about the behavior of the ground under earthquake effects. Data such as liquefaction risk, local soil class, underground water level and bearing capacity are evaluated in terms of earthquake safety.
