Foundations on Bored Piles – Pros, Cons, Installation

Pros and cons of bored piles

Good bearing capacity and versatility have made the bored pile foundation technology one of the most popular. But, like any method, it has its characteristics.

For your information. The bearing capacity of bored piles ranges from 200 to 400 tons, but if new construction technologies are used, this figure can increase significantly and reach 600 tons.

Bored piles have several advantages:

• increase the strength of the foundation, reducing uneven settlement;
• reduce the volume of earthworks, as well as concrete works;
• withstand heavy loads;
• allow the use of low-mobility soil, located at depth, as a foundation;
• have an affordable price;
• allow the use of piles with a large diameter;
• make it possible to erect a foundation, regardless of weather conditions;
• reduce the time of use of transport and machinery;
• it is possible to erect a foundation without damaging nearby structures.

Pro Tip: “Looking for reliable residential foundation services in Jamaica Plain, MA? Our expert team ensures strong, durable foundations for your home. Contact us today for a free estimate!”

List of disadvantages inherent in bored piles:

• difficulties during installation work;
• when the soil is unstable, it is very difficult to control the production of piles;
• highly paid manual labor is significantly used;
• a large consumption of concrete is required during the installation of the pile;
• it is difficult to calculate the bearing capacity of the foundation on bored piles;
• careful strengthening of the borehole walls, as well as the soil near the base of the pile, is required by cementing.

Construction of a foundation on bored piles.

Before starting the design, it is necessary to conduct a thorough analysis of the soil at the site. It is best to order a professional geological survey. As a result, it is possible to accurately determine:

• soil type (the method of installing piles depends on this (without casing, with clay or pipe casing, using the FUNDEX method);
• its features (the type of grillage depends on this):
• the depth of the stable earth layer (the depth of the well and the length of the piles will depend on this).

After the soil study and based on its results, the necessary calculations are made, taking into account the load from the future task.

Construction technology using the example of construction using casing pipes.

1. First, the area is marked out with pegs, and then the location of the piles is marked with a stretched string.
2. The markings are checked to make sure they are correct (the holes are drilled at the intersection of the strings stretched along the installation line).
3. A plumb line must be used to mark the location of the well with a peg.
4. Having marked the exact locations of the drilling holes, the marking string is removed.
5. The wells are equipped with a garden drill; in some cases, a gas-powered drill is used.
6. A casing pipe is installed at the bottom of the shaft.
7. After this, the cavity is filled with a concrete mixture by 1/3.
8. The concrete in the well is compacted, and a new portion is poured by 1/3 of the volume.
9. Reinforcement is performed. The reinforcing frame must be higher than the future pile and protrude above it. This is necessary for a better connection of the pile column with the grillage.
10. After compaction, the pile head is arranged.

Features of installation works

The piles must be driven into the ground to a depth of at least 30 cm (the freezing point of the soil). First, the wells are drilled, then they are filled with concrete. The difficulty may arise when drilling the pit, the previous pit may crumble.

Important! When preparing the concrete mixture, use grade B 15 (compressive strength), W 6 (water resistance), and crushed stone (fraction 5-30 mm) as a filler.

The borehole can be widened at the base by half a meter using a TISE drill. Another method, which is often used in private construction, can also be used. This will require a bayonet shovel with an edge width of 10 cm, the handle of which should be extended to reach the bottom of the borehole. Using such a tool, the soil on the walls of the shaft should be cut to the size in diameter that is necessary for the arrangement of a bored pile.

Pro Tip: “Expert residential foundation services in West Roxbury, MA. Strengthen your home’s foundation with our trusted team. Get your free estimate today!”

Main characteristics for calculating bored piles:

• load-bearing capacity (the larger the size of the column, the greater the load it can withstand);
• the optimal distance depends on the mass of the structure and the load-bearing capacity of the pile;
• strength depends on the grade of concrete (it is recommended to use grade M 200).

Reinforcement allows to give strength to the structure, to increase the bearing capacity of the foundation. In manufacturing the reinforcing frame, reinforcement rods with a diameter of up to 12 mm are used, in the required quantity, fixed by welding or knitting wire in places of the transverse ligament of vertical pins.

The number of reinforcing rods on a pile depends on the future load and the diameter of the pile (can reach 1.5 m), and the number of transverse ties depends on its length.

The reliability and durability of bored piles depend on compliance with construction technology and the quality of the materials used. As well as on the degree of accuracy of calculations and correct design.