What are the Different Soil Boring Methods?

October 28, 2016


When soil exploration is needed, there are different boring methods that can be used, depending on many variables. The various techniques include the following:

  • Displacement Boring
  • Wash Boring
  • Auger Boring
  • Auger and Shell Boring
  • Rotary Boring or Drilling
  • Percussion Boring or Drilling

Displacement Boring

Displacement boring consists of sampling and boring. It is an easy and economic method, as long as excessive caving does not occur A piston style sampler, bottom sampler or slit cup is forced in the ground up to the correct depth. The holes are 25mm to 75mm. The sampler is then removed from the soil by rotating the piston to release it. This process is then repeated. This method also entails somewhat continuous sampling in dense and stiff soil.

Wash Boring

Wash boring is one of the most popular methods because it is fast, easy, inexpensive and uses minimal equipment. However, rocks and boulders cannot be diffused by this method. The process is comprised of driving a casing through to make a hole in the ground. This enables drilling and soil sampling below the hole. The hole is then progressive by a twisting and chopping motion with a light bit. For cutting, forced water jets are used through the rods within the hole. The water also helps disintegrate the soil.

Auger Boring

This method of boring is quick and economical. It uses flexible and lightweight equipment for small and large holes. It is the ideal method to establish a ground water table and for soft to stiff cohesive soils. Although the soil is disturbed, the method is better than wash boring, rotary or percussion drilling. However, auger boring is not equipped for very hard soils or extremely soft soils because flow into the hole can happen. As well, this method is not recommended for fully saturated non-cohesive soil. Moreover, samples from this method are best used for identification purposes because they are greatly disturbed. Yet, the explorations of trial borrow pits and shallow depths are somewhat satisfactory.

Auger and Shell Boring

This method uses a variety of tools for boring. Shells with teeth or a cutting edge and cylinder-shaped augers are utilized to make in-depth borings. Mechanical rigs are generally used for depths up to 50 mm, hand operated are for depths up to 25 mm. the augers are good for soft to stiff clays, whereas the shells are good for hard and stiff clays. In addition, drill rods can be used to as a chisel for cemented gravel or thin soft strata. For soft to stiff clay, a hand rig with a cylindrical auger is used and can create vertical boring up to 200 mm in diameter and 25 m in depth.

Rotary Boring or Drilling

This method is very fast and can penetrate both soil and rocks. It uses a drill bit that is attached to the lower portion of the drill rod. Keeping in firm contact with the bottom of the hole, it rotates by proper chuck. While the drill rod is operating, a water solution of bentonite is typically used. When the mud solution returns upward the cuttings are brought to the surface.

Percussion Boring or Drilling

This method uses continual blows of a heavy chisel or suspended bit to the soil and rock structures. During boring, water is added to the hole and the slurry of disintegrated material is removed intermittently. This method is good for all types of soil, rocks and boulders. However, the soil and rock structures are generally disturbed.

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