The dynamic compaction method can be applied to gravel soil, sandy soil, silt and cohesive soil with low saturation, collapsible loess, miscellaneous fill and plain soil. It is widely used in airport runway, expressway, industrial and civil building foundation treatment construction. This paper introduces its working principle and construction technology.

一、工作原理      强夯法加固原理如下:土是由固体颗粒,水和气体三部分组成的三项体系。土体在重锤的作用下将土体中气体排出,在夯点周围出现径向裂缝,形成软土中空隙水的渗透通道,为超静水压力的消散创造了条件,相当大的夯击能转化为土体的压缩变形,随夯击能积累,土体强度获得提高。

1、 The principle of dynamic compaction is composed of three parts: solid and gas. Under the action of the heavy hammer, the gas in the soil is discharged, and the radial cracks appear around the tamping point, forming the infiltration channel of the pore water in the soft soil, which creates conditions for the dissipation of the excess hydrostatic pressure. A considerable amount of compaction energy is transformed into the compression deformation of the soil body. With the accumulation of the compaction energy, the strength of the soil body is improved.

在具体施工中必须根据现场实际情况,采用试夯确定强夯参数。

In the specific construction, dynamic compaction parameters must be determined by trial compaction according to the actual situation on site.

.有效加固深度。强夯的有效加固深度可采用Menard经验公式估算:   式中:WH-锤重×落距;K-为影响深度折减系数;D-加固深度。

. effective reinforcement depth. The effective reinforcement depth of dynamic compaction can be estimated by Menard empirical formula, where: wh - hammer weight × drop distance; K - is the reduction factor of influence depth; D - reinforcement depth.

也可按表确定:   .单击夯击能:单击夯击能等于锤重×落距,在具体施工中是由有效加固深度确定的。实际施工中表明,在相同单击夯击能的条件下,重锤低落距较轻锤高落距加固效果好,故在起吊能力许可情况下,宜采用较重的夯锤。

It can also be determined according to the table: the energy of single click ramming is equal to the weight of hammer × drop distance, which is determined by the effective reinforcement depth in concrete construction. The actual construction shows that the reinforcement effect of heavy hammer with low drop distance is better than that of light hammer with high drop distance under the condition of the same single tamping energy. Therefore, the heavier rammer should be used when the lifting capacity is allowed.

强的夯击能:强能时,空气被排出,土体压缩,孔隙水压变化,当地基土中的孔隙水压力达到土的自重压力时,即认为土体接收的能量达到饱和,该能量为强夯击能。

Dynamic compaction energy: in case of strong energy, the air is discharged, the soil is compressed, and the pore water pressure changes. When the pore water pressure in the local foundation soil reaches the self weight pressure of the soil, the energy received by the soil is considered to be saturated, which is the dynamic compaction energy.

实际施工中夯击能的确定一般有两种办法:

There are two ways to determine the tamping energy in practical construction

一是通过埋设在地基中的孔隙水压力计测得的孔隙水压力变化判断适宜的基数,当在两击或三击测得的孔隙水压力接近时即可判定达到夯击能;

The first is to judge the appropriate base number by the pore water pressure measured by the pore water pressure gauge embedded in the foundation. When the pore water pressure measured by the last two or three blows is close, the optimal compaction energy can be determined;

二是通过夯击数和夯击沉量关系曲线确定夯击能,相邻两击之间的夯击沉量的差值在~mm,且夯坑周围隆起,即认为达到夯击能。

The second is to determine the best ramming energy through the relationship curve between the number of tamping and the amount of tamping settlement. The difference between the two adjacent blows is ~ mm, and the surrounding of the tamping pit is uplifted.

施工中测夯击沉量比测土中水压力简单,一般在工程中以夯击数和夯沉量关系曲线确定夯击能,有经验的工程师也可直接从夯坑周围地面隆起程度判断。   .

In construction, the measurement of tamping settlement is simpler than the measurement of water pressure in soil. Generally, the best ramming energy is determined by the relation curve of tamping number and tamping settlement. Experienced engineers can also judge directly from the uplift degree of the ground around the tamping pit. .

夯击遍数：夯击遍数国内一般为~遍,但还要根据地基土的性质确定,地基土渗透系数低,含水量高,需再增加一次,一遍为低能量满夯。

Tamping times: the number of tamping times in China is generally ~ times, but it should be determined according to the nature of foundation soil. The permeability coefficient of foundation soil is low and the water content is high, so it needs to be increased again. The last time is full compaction with low energy.

夯击间隔时间。夯击间隔时间是指主副夯施工时间的间隔,主要根据孔隙水压力消散的情况而定,一旦孔隙水压力消散,即可进行副夯作业。可以通过试夯过程中的孔隙水压力测量确定。当缺少实测资料时,可根据地基土的渗透来定。

Tamping interval. The interval time of tamping refers to the construction time interval of main and auxiliary tamping, which is mainly determined according to the dissipation of pore water pressure. Once the pore water pressure dissipates, auxiliary compaction can be carried out. It can be determined by the measurement of pore water pressure in the process of trial compaction. In case of lack of measured data, it can be determined according to the infiltration of foundation soil.

夯点布置及夯点间距:夯击点可按方形或梅花形布置。遍的夯点间距要远,使得深层土得到加固,然后中间补插副夯点。夯点间距通常是~米,考虑到地基的应力扩散作用,夯点布置范围则宜比基础范围大H/(其中H为加固的深度)。当土质差、软土层厚时应适当增大夯点间距,增加夯实遍数达到加固目的,当软土层较薄而有砂类土夹层或土夹石填土时可适当减小夯距。

Layout and spacing of tamping points: tamping points can be arranged in square or plum shape. The distance between the first tamping points should be far, so that the deep soil can be reinforced, and then the auxiliary tamping points should be inserted in the middle. The spacing of tamping points is usually ~ M. considering the stress diffusion effect of the foundation, the range of tamping points should be larger than the scope of foundation H / (where h is the depth of reinforcement). When the soil quality is poor and the soft soil layer is thick, the spacing of tamping points should be appropriately increased and the tamping times should be increased to achieve the purpose of reinforcement. When the soft soil layer is thin and there is sand soil interlayer or soil with stone filling, the tamping distance can be appropriately reduced.