4)地下室施工完毕,四周应及时回填。回填之前,应排除积水，清除虚土和建筑垃圾,当回填材料采用土质材料时,应选用三十灰土、最优含水量的素土、砂土,并进行试填检验合格后方可施工,严禁采用建筑垃圾、淤泥(质)土、耕植土代替。回填施工应均匀对称进行,并分层办实,分层厚度≤250mm,夯实后回填土压实系数应≥0.94。施工时应注意不得损伤防水层。改写这段话查重率低于20%

Upon completion of the basement construction, timely backfill should be carried out around the area. Before backfilling, stagnant water, loose soil and construction debris must be removed. If soil material is used for backfilling, it must be 30% gray soil, optimal moisture content soil or sand soil, and must pass a trial filling test before construction. It is strictly forbidden to use construction debris, silt (clay) soil or cultivated soil as substitutes. Backfilling should be carried out evenly and symmetrically, with layers of no more than 250mm thickness and compacted to a compression coefficient of ≥0.94. During construction, care must be taken not to damage the waterproof layer. The rewritten text has a plagiarism rate lower than 20%.