In the construction of construction projects, dynamic compaction method as a common foundation reinforcement method, in essence, is to strengthen the foundation, make the soil compact, improve the soil bearing capacity, so as to provide a stable guarantee for the future construction. Therefore, the quality inspection of dynamic compaction is very important.
1、 Machinery and equipment
Rammers can be divided into two types: integral rammer and combined rammer, which are made of steel plate. Rammers generally use round hammer marks because they are easy to overlap. The hammer bottom area depends on the soil surface: sandy soil is generally 3 ~ 4m2; cohesive soil should be less than 6m2. The hammer weight is generally 8, 10, 12, 16, 25, 30t, etc. In the process of hammering, a number of ventilation holes with diameter of 60 ~ 200 mm are arranged at the hammer head and hammer bottom to reduce the suction during hammering.
2. Lifting equipment
a. Generally, crawler crane or other lifting equipment (such as special tripod, gantry, etc.) is selected, with lifting capacity of 15, 30 and 50 t. The lifting height of lifting equipment must meet the requirements of dynamic rammer. Choose the active hook hammer equipment, the lifting capacity should be greater than 1.5 times of the hammer weight.
B. The decoupling device shall have the required strength and sensitivity to ensure that the shooting distance of each rammer is the same.
c. When the lifting capacity of the crane is insufficient, the support rod can be installed on the suspender to increase the lifting capacity.
2、 Key points of quality inspection in construction process
1. Content of view
Hammer weight, drop hammer distance, location of tamping point, tamping times and spacing between tamping times.
2. Quality control
a. Before construction, according to the planning requirements of hammer weight, drop, tamping point layout and number of tamping points, on-site compaction test is carried out to determine the technical parameters used in formal construction.
b、强夯基础场地按预先定好的地面标高，用推土机进行平整。地面时细土,地下水位高,表层应铺约0.5 ~ 2米的砂、碎石或砂砾,以形成一个硬层表面上,避免设备抑郁和容易消散孔隙水压力的动态压实,并能增加地下水和外表面之间的间隔,以避免捣固功率下降。当局部较低水位低于地表2m且地表为非饱和土时，可直接进行夯实。
b. The dynamic compaction foundation site shall be leveled with bulldozer according to the pre-determined ground elevation. When the ground is fine soil and the underground water level is high, the surface layer should be paved with 0.5 ~ 2m sand, gravel or gravel to form a hard layer on the surface to avoid equipment depression and dynamic compaction which is easy to dissipate pore water pressure, and can increase the interval between groundwater and external surface to avoid the reduction of tamping power. When the local low water level is 2m lower than the surface and the surface is unsaturated soil, it can be directly compacted.