The strength of slope protection soil of old highway is slightly low. After excavating the steps according to the specifications, the thick and thin soil that must be compacted at one time at the junction of the new and old subgrade is the height from the subgrade bed or the top surface of the top ladder to the subgrade material, at least a few meters, and the compaction equipment and compaction technology should be adapted.

Traditional rollers (including small rollers) have a small impact depth and belong to surface (shallow) compaction equipment. T up and down rollers are suitable for layered rolling. The reinforcement effect of 32~36t heavy-duty small rollers on the new subgrade is obvious, and the reinforcement effect on the old and new subgrade is very small. The compactness of 32~36t small rollers with an exciting force of more than 5000 kn can reach more than 96% after reinforcement. When in use, when the hc36  Rapid Impact Compaction is reinforced again, the settlement is still more than 200mm.

The impact roller shall be mainly tamped, and the compaction equipment shall be combined with tamping and rolling. The compaction strength and influence depth depend on the driving speed. The reinforcement effect of 1m effective depth is obvious, which is better than 32~36t small roller. However, there are many widening periods, uneven progress, more bridges and culverts, fewer hundreds of meters of continuous subgrade, and the total width of widening on both sides is insufficient. After the embankment is completed, the subgrade continues. The soil thickness of the joint part of the new and old subgrade has reached several meters, which exceeds the effective compaction depth of the impact roller, and is easy to interfere with the existing subgrade. The impact roller is not suitable for the reinforcement of roadbed and wet and soft embankment.

The dynamic compaction strength is large, and the subgrade construction is mostly 10~20t medium-sized dynamic compaction machine. The medium-sized dynamic compaction machine has a good effect on soft soil such as subgrade materials, and the layered pressure effect on the joint part of new and old subgrade is not ideal. One of the main reasons is that the grounding area is large, the grounding (surface dense soil) immediately produces air cushion effect, and the exhaust and drainage are poor after grounding. When a part of the heavy hammer falls on the strong new subgrade, the impact on the weak subgrade (ladder) will be weakened or blocked. The shock wave of dynamic compaction machine disturbs the existing subgrade greatly, and the impact on adjacent structures is also one of the shortcomings.

Rapid Impact Compaction is the inheritance and development of manual tamping in ancient China. It is a kind of geotechnical machinery that combines contemporary machinery, electromechanical and liquid technology. The structure type and action mechanism on soil are combined with the subgrade inspection of high-speed railway, and EVD dynamic deformation modulus detector is used. The dynamic compaction method of soil by Rapid Impact Compaction is an improvement of traditional ramming technology. It can not only improve the density and symmetry of formed subgrade structure and adjacent structures, but also cut and switch weak soil. In recent years, Rapid Impact Compactions are widely used in bridge and culvert backfill and high fill solutions, and the effect is excellent. In the reconstruction and expansion projects of expressways, ordinary highways and municipal roads, the reinforcement solutions of old and new subgrade also show certain technical advantages. Hc36 Rapid Impact Compaction is equipped with a ramming plate with a diameter of 1m as standard, and the impact depth is more than 4m. It is suitable for the special requirements of one-time reinforcement of several meters thick soil at the junction of new and old subgrade of Expressway and reinforcement of bridge and culvert back.

Yang Shiji, a researcher from the Academy of road Sciences of the Ministry of communications, proposed that the Rapid Impact Compaction with 3-level 9-hammer is generally used for rolling the qualified Subgrade of the new expressway, and the center distance of the compaction point is 1.5m. The proposal has both subgrade quality and construction economy. Most of the construction refers to the suggestions of researchers Yang Shiji, or appropriate adjustments on this basis. Fill every 2 layers and reinforce every M.

Hc36 Rapid Impact Compaction is equipped with a grounding circle with a diameter of 1m, and the width of the excavated top step is mostly 1.2~1.5m. After the single row or double row overlapping compaction steps, continue to compact the joint part of the steps and the new subgrade. When the subgrade of the new building is weak, the reinforcement category should cover at least the lower steps. When the top surface of the step is not filled or the filling is not more than 500 mm, the reinforcement effect is the best from time to time.