Factors Affecting Field Compaction of Soil

There are many factors which influence the degree of compaction in the field. Some are compactor dependent and some depend on the soil being compacted. The factors which affect the degree of compaction are given below.

1.土壤类型

土壤类型对其压实特性有很大影响。通常，重的粘土，粘土和淤泥具有更高的抗压实阻力，在砂土和粗粒或砾石土壤中可容易压实。与粘土相比，粗粒土壤产生更高的密度。良好的分级土可以压实到更高的密度。

2.努力努力/作文能源

术语专业努力或专有的能量仅仅意味着用于压实的设备或机器类型。更大的压力努力，更大将是压实。用于土壤压实的设备可以广泛地分为以下类别

1. Kneading type equipment
2. Static type equipment
3. Dynamic or impact type equipment
4. Vibratory type equipment

Type of compaction equipment to be used is mainly dependent upon the type of soil to be compacted. The following table can be used as a reference to decide type of equipment for different type of soil.

土壤类型	Suggested Equipment / machinery
Crushed rock, gravelly sand	Smooth wheel roller
Gravels, sand	Rubber tyred roller
沙子，砾石，粉质土壤，粘土土壤	Pneumatic tyred roller
Silty soil, Clayey soil	Sheepfoot roller
土壤s in confined zone	Rammer
沙子	Vibratory roller

3.Layer Thickness / Thickness of Lift

Degree of compaction is inversely proportional to the layer thickness, i.e. for a given compactive energy, thicker layer will be less compacted as compared to thin layer. The reason is, for thicker soil layer the energy input per unit weight is less. Therefore it is very important to decide the right thickness of each layer to achieve the desired density. Thickness of layer is dependent upon several other factors such as

• 土壤类型
• 滚筒的类型
• Weight of roller
• 滚筒接触压力
• So on …..

通常，在该领域中使用200至300mm层厚度以实现均匀的压实。

4.Number of Roller Passes

It is obvious that density increases as the no of roller passes increases. But there are two important things we have to remember.

1. 经过一定数量的滚子通过，密度没有进一步增加
2. 更多数量的滚子通过意味着更多的项目成本。

So it is very crucial to determine the number of roller passes for a given type of equipment, for a given type of soil at optimum moisture content. Therefore field compaction trial is carried out to economise compaction aspect of earthwork, while achieving desired level of density based on Lab tests (Heavy compaction test, IS:2720-Part-8 and relative density test, IS:2720-Part -14).

5。水分含量

Proper control of moisture content in soil is necessary for achieving desired density. Maximum density with minimum compacting effort can be achieved by compaction of soil near its OMC (optimum moisture content). In the field the natural moisture content (NMC) of soil is either less than OMC or above OMC. If NMC of the soil is less than OMC, calculated amount of water should be added to soil with sprinkler attached to water tanker and mixed with soil by motor grader for uniform moisture content. When NMC of the soil is more than OMC, it is required to be dried by aeration to reach up to OMC.

6。接触压力

接触pressure depends on the weight of the roller wheel and the contact area. In case of pneumatic roller, the tyre inflation pressure also determines the contact pressure in addition to wheel load. A higher contact pressure increases the dry density and lowers the optimum moisture content.

7。Speed of Rolling

Speed of rolling has a very important bearing on the roller output. There are two important things we have to consider.

• First, the greater the speed of rolling, the more length of embankment can be compacted in one day.
• 其次，在更大的速度下，可能不充分的时间来进行所需的变形，并且可能需要更多的通过以实现所需的压实。

So we need to make a balance between these two things. Generally the speed of all rollers is limited to about 5 km/hour. In case of vibratory roller speed was found to be significant factor because its number of a vibration per minute is not related to its forward speed. Therefore, the slower the speed of travel, the more vibrations at a given point and lesser number of pass required to attain a given density.