【Haichuan Construction Technology】What are the requirements for soil backfilling, and what is the standard approach? ?
Thread Content
According to the relevant standards, soil backfilling must be carried out in layers, with each layer being compacted and inspected separately. In building projects, this primarily involves backfilling of trenches for foundations and other structural elements; in municipal engineering, it mainly refers to backfilling of trenches for various pipelines. The corresponding acceptance standards specify requirements regarding the thickness of each layer and the compaction degree. The main standard used as a reference is the \"Code for Acceptance of Construction Quality of Building Foundation Engineering\" GB50202-2018. In fact, the layer thickness for soil backfilling and the number of compaction passes should be determined through on-site testing, based on the specific soil properties, compaction coefficients, and compaction equipment used in a particular project. However, in the absence of such testing data, Table 9.5.2 of the \"Code for Acceptance of Construction Quality of Building Foundation Engineering\" GB50202-2018 provides general guidelines. It is important to note that the layer thickness referred to in the code denotes the thickness of the uncompacted soil, not the thickness after compaction. Many construction sites misunderstand this value as the thickness after compaction, resulting in excessive backfilling and insufficient compaction. In some cases, no layers are created at all; the soil is backfilled in one go before being compacted, which leads to frequent settlement problems.
How to control the layer thickness at the construction site? Before the earthbackfilling work begins, the height lines for each layer are marked on municipal pipeline projects at inspection wells, on the protective layer of the exterior walls in building foundation projects, on the columns in building foundation works, or at other stable and visible locations. These lines serve as a basis for controlling the thickness of the backfill, thereby preventing issues such as insufficient compaction caused by excessive backfill thickness. The following three textbook-style project examples illustrate the practices for controlling the layer thickness when backfilling soil in municipal engineering trench works, foundation backfilling in building construction projects, and shaft backfilling in building construction projects. They are provided for reference: https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/e570b7ea81ba4a52a924e34cbb34f950~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1761899300&x-signature=FfIlofi90IE213FbPmm82%2FWOBkE%3D https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/bd28de256a32435fbf064aa6bd3859bc~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1761899300&x-signature=TDY1ekjvnCg106dLim59IGaHxts%3D Example of a municipal project by CCCC First Highway Engineering Bureau: https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/8c9e81b134614d82a8cc01a7627fcc9d~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1761899300&x-signature=KMdzODxqJoUgt%2FsAyyNByH4qtHQ%3D Example of a building construction project by CCCC First Highway Engineering Bureau: https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/d37c5c63724a40b797a6a504b507aad4~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1761899300&x-signature=k7gna0H22t5GT%2Fx8%2B%2BzCch1UBVM%3D Example of a building construction project by Yongan Chengfa. In accordance with the control lines for layer thickness, backfilling and compaction are carried out layer by layer in line with regulatory requirements. The compaction coefficient is tested using methods such as the ring cutter test, sand filling method, or water filling method at each layer, and it must meet the design specifications. Currently, the ring cutter test is commonly used; samples are taken from the lower half of each compacted layer, and the number of samples per layer is as follows: for foundation pits and indoor backfilling, 1 set per 100–500㎡, with no less than 1 set ； Backfilling of column bases: 10% of the total number of column bases, with a minimum of 5 sets ； Backfilling of foundation trenches or ducts: 1 set per 20–50 m, with a minimum of 1 set ； Outdoor backfilling: 1 set per 400–900㎡, with a minimum of 1 set.
【Ten Years of Rapid Development in Chemical Engineering Equipment】From 2765 to 2025: CGN Group’s technology for the utilization of high-salinity unconventional water resources recognized as internationally leading https://bbs.hcbbs.com/thread-5703353-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】From 2765 to 2025: CGN Group’s technology for the utilization of high-salinity unconventional water resources recognized as internationally leading https://bbs.hcbbs.com/thread-5703353-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】China’s first **-class deep-sea oil and gas emergency rescue base was put into use in Hainan from 2767 to 2025 https://bbs.hcbbs.com/thread-5703425-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Equipment】The world’s first production facility capable of manufacturing thousand-ton quantities of rubidium and cesium salts has reached full capacity at the Anyi County production site of Jiangxi Jinde Lithium New Energy, 2768-2025. https://bbs.hcbbs.com/thread-5703443-1-1.html (Source: Haichuan Chemical Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】The first international standard formulated by China in the field of oil and gas metering was officially released: https://bbs.hcbbs.com/thread-5703582-1-1.html (Source: Haichuan Chemical Industry Forum)
【Ten Years of Rapid Development in Chemical Engineering Equipment】2771-2025: The helium cryocooler with the highest cooling capacity currently in use in China’s fusion field is operating stably. https://bbs.hcbbs.com/thread-5703623-1-1.html (Source: Haichuan Chemical Engineering Forum)