Dynamic compaction is a physical method in foundation treatment. It is a typical dynamic problem to compact the deep soil by impact. Its principle is to use the powerful compaction energy to force the deep soil to liquefy and dynamically consolidate, so as to make the soil compact, so as to improve the strength of foundation soil, reduce the compressibility, and eliminate the collapsibility, expansion and contraction and liquefaction of soil.

强夯法有三种不同的加固机理

There are three different strengthening mechanisms of dynamic compaction

1、动力固结：当强夯法应用于处理细颗粒饱和黏土时，其加固机理则是动力固结理论。强夯时，巨大的冲击能量在土中产生很大的应力波，破坏土体的原有结构，使土体局部发生液化并产生许多裂隙，增大了排水通道，使孔隙水顺利逸出，待超孔隙水压力消散后，土体固结。由于软土的触变性，强度得到恢复。（安利一下，触变性是指含水率不变情况下黏土因为重塑而软化，强度降低，软化后随着静置时间延长而硬化，强度增长的性质）

1. Dynamic consolidation: when dynamic consolidation method is used to treat fine-grained saturated clay, its reinforcement mechanism is dynamic consolidation theory. During dynamic compaction, the huge impact energy produces a large stress wave in the soil, destroys the original structure of the soil, liquefies the soil locally and produces many cracks, increases the drainage channel, and makes the pore water escape smoothly. After the excess pore water pressure dissipates, the soil consolidates. Because of the thixotropy of the soft soil, the strength is restored. (for Amway, thixotropy refers to the property that clay softens due to remolding under the condition of constant moisture content, and its strength decreases. After softening, it hardens with the extension of standing time, and its strength increases.)

2、动力密实：采用强夯法加固多孔隙、粗颗粒、非饱和黏土是基于动力密实的机理，即冲击型动力荷载，使土体中的孔隙减小，土体变得密实，从而提高地基土强度。非饱和土的夯实过程，就是土中的气相（空气）被挤出的过程，其夯实变形主要是由于土颗粒的相对位移引起。

2. Dynamic compaction: the dynamic compaction method is used to reinforce porous, coarse-grained and unsaturated clay based on the mechanism of dynamic compaction, that is, the impact dynamic load reduces the pores in the soil and makes the soil dense, so as to improve the strength of foundation soil. The compaction process of unsaturated soil is the process in which the gas phase (air) in soil is squeezed out, and the compaction deformation is mainly caused by the relative displacement of soil particles.

3、动力置换：动力置换可分整式置换和桩式置换。整式置换是采用强夯将碎石整体挤入淤泥中，其作用机理类似于换土垫层。桩式置换是通过强夯将碎石填入土中，部分碎石桩（或墩）间隔地夯入软土中，形成桩式（墩式）的碎石桩（墩），其作用机理类似于振冲法形成的碎石桩，整体形成复合地基。

3. Dynamic replacement: dynamic replacement can be divided into integral replacement and pile replacement. Integral replacement uses dynamic compaction to squeeze the gravel into the silt, and its mechanism is similar to that of soil replacement cushion. Pile replacement is to fill gravel into soil by dynamic compaction, and part of gravel piles (or piers) are rammed into soft soil at intervals to form pile (pier) gravel piles (piers). Its mechanism is similar to that of gravel piles formed by vibroflotation method, forming composite foundation as a whole.