According to what, the site categories are divided into four categories?

According to the thickness of the covering layer of the construction site, the site is divided into four categories: I, II, III and IV, where I is divided into i0 and i 1. For the specific division method, please refer to Article 4. 1.6 of Code for Seismic Design of Buildings.

Architecture is the general name of buildings and structures, and it is an artificial environment created by people to meet the needs of social life by using the material and technical means they have mastered and applying certain scientific laws, geomantic concepts and aesthetic laws.

These four categories are as follows:

Grade I site soil: rock and dense gravel soil.

Class II site soil: medium-dense and loose gravel soil, dense and medium-dense gravel, coarse sand and medium sand; Cohesive soil with allowable bearing capacity of foundation soil > 150kpa.

Class III site soil: loose gravel, coarse sand and medium sand, dense and medium dense fine sand and silt, cohesive soil, allowable bearing capacity of foundation soil [σ0] ≤ 150kPa, and filling soil [σ0]≥ 130kPa.

Class Ⅳ site soil: muddy soil, loose silty sand and recently deposited cohesive soil; Allowable bearing capacity of foundation soil [σ 0] < 130kPa filling.

The engineering importance, site complexity and foundation complexity are all Grade III.

Note: For the first-class project built on rock foundation, the geotechnical engineering survey grade can be classified as Grade B when the site complexity grade and foundation complexity grade are Grade III.

For example, the importance level of the proposed building is Grade II, the foundation level is Grade III, the site level is Grade II, and the geotechnical engineering survey level is comprehensively judged as Grade B. No adverse geological structures such as faults are found in the site, and the overall stability of the site is good, and there are no major engineering geological disasters that seriously threaten the safety of the site and the project.

There are no buried objects such as rivers, ditches, graves and air-raid shelters that are unfavorable to the project, which is suitable for the construction of this project.