The brand of rapid impact compaction is “夯神” brand, model is HC, and it is widely used in Shandong, Guangdong, Gansu, Henan, Hebei, Jiangsu and other parts of the country. The effect of rapid impact compactor on the subgrade on the back of the platform is usually used to comment on the basic theory of driving force preloading for L.Menard roadbed reinforcement. The basic theory of L.Menard driving force preloading can be simply described as the following aspects:

(1) The pores in the subgrade soil are reduced;

(2) Partial evaporation of subgrade soil;

(3) There are cracks around the tamping point of the rapid compactor, which provides a better drainage safety channel for the pore water in the soil, and the soil quickly causes preloading.

(4) With the gradual change of time, the compressive strength of damaged soil is slowly restored.

The actual details are as follows:

(1) Subgrade soil reduction link

The main components of subgrade backfill are gas, water and soil particles. When the rapid compactor works on the subgrade soil, the subgrade soil is in the shrinking stage. With the continuous development of compaction, a small amount of pore water and gas in the subgrade soil is continuously discharged, and the compaction degree of the subgrade soil is continuously improved.

(2) Vaporization of subgrade soil

The second whole process of the effect of the rapid compactor on the roadbed is the whole process of the evaporation of the roadbed soil. Through the compaction effect of the fast compactor, the pore water and gas in the subgrade soil are discharged, and then the subgrade soil is reduced until the compaction degree of the subgrade is specified. During this link, the pore water pressure will continue to expand, and when it balances with the longitudinal internal stress, the soil will liquefy. Since the subgrade backfill contains a certain amount of water, the effect of the rapid compaction machine will cause the subgrade to vibrate and increase the ambient temperature of the subgrade, so the water will be dispersed into free water, which will reduce the adhesion between the subgrade soil and the compressive strength of the subgrade.

(3) Subgrade soil pore water discharge link

When the subgrade soil structure liquefies, the pore water pressure of the subgrade soil gradually decreases when the rapid compactor stops working. Since the ramming kinetic energy of the fast compactor is relatively large, the excess pore water pressure formed in the middle of the subgrade soil evaporating the subgrade soil particles is the same as the transient pore water pressure, which provides a safe channel for the pore water of the subgrade soil and improves the coverage of the subgrade soil. Rate. With the change of time, the pressure of pore water in the subgrade soil gradually decreased. When its vertical working pressure is weaker than that of the subgrade soil, the safe passage for pore water removal will be closed, and the pore water in the subgrade soil will recover.

(4) Subgrade soil repair link

When the rapid tamping machine performs the tamping effect on the roadbed, the tensile strength of the roadbed soil is continuously weakened due to the liquefaction of the roadbed soil. Due to the reduction of the tensile strength, cracks will appear in the soil, and the water adsorbed in the soil will be converted into free water. . With the subsidence of pore water pressure, the deformation modulus and tensile strength of subgrade soil have increased to a certain extent. Therefore, soil particles absorb the dispersed free water, creating a cyclic system of deformation reaction of all subgrade soils. The compressibility of subgrade soil varies with the mechanical properties of the soil structure.