What Are Screw Piles?

Steel spiral pile is currently the most widely used type of spiral pile. Steel spiral piles are very suitable for practical production in terms of technical indicators and economics, and can be recommended for general use. Steel spiral piles include cylindrical hollow piles and solid round or polygonal piles. ^[1]

Steel spiral piles are divided into cylindrical hollow piles and round or polygonal solid piles. Steel spiral piles have excellent strength properties, are economical and durable, and are widely used today. This spiral pile length is used to strengthen and fix the bridge.

Reinforced concrete hollow pipe joints are twisted by special steel hooks inside the pile body. The twisting torque of the winch is transmitted to the pile at the level of the rotary blade.

In order to increase the strength of the pile, the hollow pipe joint must be

The theoretical bearing capacity of spiral piles must be checked during actual project construction.

This inspection is of great significance to spiral piles, because the calculation formula of the bearing capacity of spiral piles is an approximate value. The individual coefficients and parameters listed in these formulas are not always correct.

The bearing capacity of the spiral pile and the torsional moment in the final stage of screwing are linear. The larger the torsional moment in the final stage, the greater the bearing capacity of the spiral pile. However, between these two values, no theoretical relationship has been specified so far. Therefore, it is practically impossible to determine the bearing capacity of the screw pile by torsional moment.

In this way, the bearing capacity of the spiral pile is still basically checked by the static load test. The allowable bearing capacity of the spiral pile is part of the ultimate soil stress obtained by the static load test:

_tolerance = _limit / K

In the formula:

KSafety factor, generally used 2.

If the number of piles in the cap is small, for a building, its stability is greater than the number of piles in the cap. The larger the number of piles in the cap, the easier it is for the load to be evenly distributed between the piles, which is obvious.

According to this point, it can be concluded that the screw pile (the number of roots in the pier is much less than the number of driven piles) should be added to the safety factor according to the number of roots in the pier.

For example, when the number of spiral piles of each bridge pier is from 4 to 8 (in the engineering experience of screw piles; this situation is often encountered), this coefficient is between I.35 ~ 1.50, which is the total safety The coefficient has been increased from 2 to 3.

However, for screw piles, the supplementary safety factor is not fully justified. Compared with other types of pile foundations, it is a disadvantageous condition to make it.

Engineering experience has shown that a safety factor of 2, even under the most unfavourable conditions, is sufficient to ensure the safety of a building for any type of pile.

Therefore, for screw piles, there is no need to increase the stacking factor. In fact, the method used to calculate the screw piles has a safety factor that is sufficiently large, although no additional safety factors are added. ^[1]

The results of the spiral pile static load test performed on many bridges are shown in Figure 2. The materials listed in the figure are data from 12 spiral pile tests on five bridges.

figure 2