Legal analysis: The Technical Specification for Highway Subgrade Construction stipulates that the loose paving thickness is not more than 30cm, and the compaction thickness is subject to the loose paving coefficient. Generally, the thickness after compaction is 20cm, because the maximum thickness of compacted layer detected by sand filling method is 20cm. The cleaning thickness of topsoil is not less than 50cm, and the planting soil is stored in the soil storage yard for subgrade slope greening.

Legal basis: Article 62 of the Law of People's Republic of China (PRC) on Work Safety states that the local people's governments at or above the county level shall, according to the situation of work safety within their respective administrative areas, organize relevant departments to conduct strict inspections on production and business units prone to major production safety accidents within their respective administrative areas according to the division of responsibilities. The emergency management department shall, in accordance with the requirements of classified supervision and management, formulate an annual supervision and inspection plan for production safety, and carry out supervision and inspection according to the annual supervision and inspection plan. If hidden dangers of accidents are found, they shall be dealt with in time.