Different Methods Of Boring For Soil Sampling For Soil Investigation
In the soil Investigation when the depth of exploration is very large, in such conditions we use the boring method for the exploration.
In the boring method, we drill a borehole and collect the soil sample and determine the different properties of the soil in the lab.
Boring Method Of Soil Exploration
The method of Soil boring mainly depends on the characteristics of the soil and the purpose of boring. Here is the 4 soil bore method of soil exploration:
- Auger Boring
- Wash Boring
- Rotary Drilling
- Percussion Drilling
The auger boring is may be manually operated or mechanically operated and it is used for the soft cohesive soils.
In the auger boring soil exploration, the soil sample is badly disturbed.
The cylindrical or helical drills are used in the auger boring method.
It is suitable for shallow foundations and it can be used for gravels also.
More Read- Auger Boring For Soil Exploration- Method, Advantages & Disadvantages
The wash boring method is suitable when exploration is to be done below the groundwater table.
The wash boring is suitable for all types of soils.
The casing is provided into the hole and water is forced by means of a drill rod which is alternatively raised and dropped.
As a result, cuttings are forced upward to the ground surface in the form of soil water slurry.
More Read- Wash Boring Method Of Soil Exploration-Procedure, Advantages & Disadvantages
The rotary boring does not require casing but drills are of big diameter and rotate continuously at the high speed, so we can prepare big holes in a very short time by using rotary drilling.
In the rotary drilling, a hollow drill rod is used which has a cutting bit at its lower end.
The cutting of soil starts when the drilling rod is starting rotating by using power.
A drilling fluid is introduced to the bottom of the hole through the hollow drill rod and this fluid comes up with the cutting of soil to the surface through the annular space between the drilling rod and the walls of the hole.
During the time of taking the soil sample, we simply replace the drilling bit with the sampler and easily collect soil samples for further investigation of soil.
Advantages Of Rotary Drilling–
1- The main advantage of rotary drilling is it is used for clay, sand, and rocks and rotary drilling is the fastest method in the case of drilling holes in the rocks.
2- The second advantage of rotary drilling is it does not require any casing and we can easily take the soil sample.
Disadvantages Of Rotary Drilling-
1- The main disadvantage of rotary drilling is the soil sample is madly disturbed and this method is not well suitable for the material that contains a large number of particles of gravel size and larger.
In the percussion boring or drilling, we use a heavy chisel for breaking the boulders and rocks by repeating numbers of blows.
Procedure of percussion drilling-
First, we provide casing if needed after that we alternatively lift and drop the heavy chisel in a vertical hole.
In this process, the heavy chisel is suspended with the help of a rope or chain.
By repeating the blow of the heavy chisel the soil inside the hole gets reduced into fine particles.
If the striking point of the heavy chisel is above the water table then we have to add water to the hole to facilitate the breaking of soil.
The water forms the slurry with the breaking soil which is removed by a sand pump or bailer at intervals.
Advantages Of Percussion Drilling-
1- The main advantage of using percussion drilling is that it is used for making holes in the rocks, boulders, and other hard strata.
2- it can be used for all types of materials for making holes.
Disadvantages Of Percussion Drilling-
1- The main disadvantage of percussion drilling is the material at the bottom of the hole is disturbed by the heavy blow of the chisel so the collected soil sample is highly disturbed.
2- The percussion drilling method is more expensive than other methods.
3- In this method, the changes in the properties of the strata penetrated difficult to detect.
Frequently Asked Questions (FAQ)
Here are the different methods of boring.
The main difference between rotary drilling and percussion drilling is that in rotary drilling the cutting of soil starts when the drilling rod is starting rotating by using power, whereas in percussion drilling the cutting of soil starts by alternatively lifting and dropping the heavy chisel in a vertical hole.
The main difference between wash boring and auger boring is that in the wash boring the cutting of soil started by the action of water jet and chopping whereas in the auger boring the cutting of soil is done by manually applying thrust in a downward direction or by mechanical method.