4.2　Cohesive Fill and Lime-soil Fill

4.2.1　The soil materials of cohesive fill and lime-soil fill shall meet the following requirements：

1　For cohesive fill，clay or silty clay can be used，of which the organic content shall not be greater than 5%and which shall be sieved；frozen soil or expansive soil shall not be included；topsoil，mud and muddy soil and unengineered fill shall be strictly forbidden.

2　For lime-soil fill，clay or silty clay can be used，of which the organic content shall not be greater than 5% and which shall be sieved with the particle size not greater than 15mm；freshly slaked lime，with the particle size not greater than 5mm and not including unslaked lime particles，should be used；the mix proportion of lime soil by volume should be 2∶8 or 3∶7，and the lime soil shall be mixed uniformly.

4.2.2　For cohesive fill and lime-soil fill，the water content during construction should be controlled within the range of±2% optimum water content，which can be determined either through compaction test or according to local experience.

4.2.3　The construction method，backfilling lift thickness and compaction requirements of cohesive fill and lime-soil fill subgrades should be determined through field tests；the backfilling lift thickness should be taken as 200mm-300mm and shall be compacted at each lift.Where the base of fill is soft soil，the bottom portion of the fill should be reinforced.

4.2.4　The cohesive filll and lime-soil fill subgrade should be constructed by sections in which the sectional joints shall not be under column foundation，wall corners and load-bearing walls between windows.The distance between joints for adjacent upper and lower layers shall not be less than 500mm，and additional compaction efforts should be madeat joints.

4.2.5　When hard-soft heterogeneous subsurface conditions such as caves and invisible creeks（ponds）exist below foundation base，special treatments shall be performed in accordance with the design requirements.

4.2.6　The inspection of cohesive fill and lime-soil fill construction shall meet the following requirements：

1　Each lift shall be inspected and the upper lift soil shall be filled only when the compaction coefficient for the present lift meets the design requirements.

2　The cutting ring method，penetrometer，static cone penetration test，light dynamic penetration test or standard penetration test and other methods may be used，and the inspection standard shall meet the design requirements.

3　Where the cutting ring method is used to inspect construction quality，the sampling points shall be at 2/3 depth of the thickness of each lift.For raft and box foundations，the number of inspection points shall not be less than 1 for every 50m2-100m2；for strip foundations，the number of inspection points shall not be less than 1 for every 10m-20m；the number of inspection points shall not be less than 1 for each isolated foundation.

4　Where the penetrometer or light dynamic penetration test is used to inspect construction quality，the spacing between inspection points for each lift shall be less than 4m.