6.4 Earthwork
6.4.1 With respect to balance of cut and fill，the following principles shall be observed in the design:
1 Besides the earthwork required for ground leveling，earthwork of the following works shall also be included:
1）earthwork for foundation of buildings，structures and equipment，foundation trench of pipeline（or sump pit），drains，roads and railways，etc.
2）Surplus earth from cut or earth to be borrowed for collapsible loess.
3）Cultivated soil and surface soil removal and backfill of the rice field，pond and swamp，etc.
2 When it is necessary to take the soil from or dump the soil to outside the plant（yard），the soil taking source or dumping site shall be taken into consideration.
3 If it is convenient and economically reasonable to have the soil taken from and dumped to a place near the plant（yard）area，the balance of the earthwork volume in the plant（yard）area may not be imperative.
4 The place to be filled，which is close to boundary of the plant（yard）and not to be used at the moment，may be filled gradually by using production wastes that are suitable for site filling after the plant is put into operation.
6.4.2 The site filling and subsoil treatment shall meet the following requirements:
1 The turf patch and the soil with organic matter content larger than 8% shall only be used for the fill without compaction requirement.
2 The good quality cultivated soil and surface soil may be used as the filling material.However，if the cultivated soil or surface soil contains so much moisture that affects the rolling compaction，it should not be used as filling material.
3 Broken stone，sand（fine sand and silt should not be used）and blast stone fragment may be used as the filling materials under the surface layer.
4 If the subsoil for filling is on the cultivated soil or loose soil，the subsoil shall be compacted by means of rolling or ramming to the degree of compaction as specified in Table 6.4.3-1 before filling.If the subsoil for filling is on the paddy field or pond，the proper subsoil treatment measures shall be taken as the case may be（e.g.drainage and dewatering，dredging up the silt，dumping the rubble or gravel sand，slag，etc.）.
Table 6.4.3-1 Minimum degree of compaction of the site filling
Note:In case of large area site leveling，0.90 may be taken as the degree of compaction of the fill for the whole site.
5 The stump or taproot on the subsoil shall be removed，so does the water，silt and foreign matters in the crater.The filling shall be rammed by layers.
6 For the fill area under the buildings and structures and the fill area less than 0.5m in thickness，turfs and wastes on the subsoil shall be removed.
7 If filling is performed on the flat land of good soil quality with gradient no steeper than 1∶10，turfs on the subsoil may be left there，but long grass shall be removed.
8 If filling is performed on the stable mountain slope，turfs on the subsoil shall be removed when the gradient is 1∶10-1∶5，and the subsoil shall be excavated into steps with step width no less than 1m when the gradient is steeper than 1∶5.
9 Subsoil filling，compacting and treatment of the foundation of buildings and structures shall meet the relevant requirements of the current national standard GB 50007 Code for Design of Building Foundation.
6.4.3 The minimum degree of compaction of the fill shall meet the following requirements:
1 The minimum degree of compaction of the site filling shall be in accordance with those specified in Table 6.4.3-1.
2 The minimum degree of compaction of the railway subgrade shall be in accordance with those specified in Table 6.4.3-2.
Table 6.4.3-2 Minimum degree of compaction of railway subgrade
Note:In case of No.3，the degree of compaction may be reduced by 0.05 with reference to the value in this table provided the precipitation in the said area is less than 400mm.
3 The minimum degree of compaction of the road subgrade shall be in accordance with those specified in Table 6.4.3-3.
Table 6.4.3-3 Minimum degree of compaction of road subgrade
Notes:1 The values in the table refer to the degree of compaction with the maximum dry density calculated by using heavy compaction test method.
2 Low fill refers to the fill less than 80cm.
3 Depth of low fill is counted from the original ground floor，while other depths are counted from the bottom of the road trough.
1）For low fill，the compaction requirements for both the 0-80cm fill and the fill with a dept of 0-40cm counted from the original ground floor shall be complied with.
2）Application of the minimum degree of compaction of the subgrade in Table 6.4.3-3:Low limit shall be taken for cohesive soil；up limit shall be taken for sandy soil.
3）The minimum degree of compaction of subgrade in arid area（area with annual precipitation less than 100mm and having scarse groundwater）and humid area（area with annual precipitation more than 2500mm，annual rainy days more than 180 days，and soil moisture exceeding 5% of the optimal moisture）may be reduced by 0.02-0.03 with reference to those specified in Table 6.4.3-3.