What Is The Significance of Pile Testing before Pile Foundation Construction?

There are three types of test piles, design test piles, pre-construction test piles and post-construction test piles.

------------------------- Design test piles -------------------------

Based on the geological report and local experience, the pile type and the characteristic vertical bearing capacity of a single pile are selected.

Purpose

1， is to further determine the construction feasibility of the selected pile type, so as to avoid that the pile type is not suitable for the construction of this site or the pile bearing capacity is found to be much smaller than the calculated value provided by the geological report after the pile driving machine is fully installed on the site, in which case the change of the pile type will cause delay in the construction period and increase the cost.

2， Determine the characteristic value of vertical bearing capacity of single pile according to vertical static load test of single pile. Since the values provided by the geological report are often conservative, the pile bearing capacity can be increased and the number of piles can be reduced according to the static load report. When using static pile construction method, the construction pressure pile force is related to the characteristic value of single pile bearing capacity, but it is not absolute, according to the experience and local standards, it can be 1.5~2.5 of the characteristic value, as long as the static loading test meets the requirements, the construction pressure pile force can be used in full-scale construction with the standard of test pile.

------------------------- Pre-construction test piles -------------------------

Decide whether to do pre-construction test piles or not according to the actual situation of the project. Pre-construction test pile can be reserved for engineering piles.

Among them, there are the following three cases in which preconstruction test piles must be done according to the specification.

1, Pile foundation with design grade A or B.

2、Complicated geological conditions and low reliability of pile construction quality.

3、New pile type or new technology adopted in this region.

Test pile after construction: According to the geological report and local experience, select pile type and single pile vertical bearing capacity characteristic value, randomly select a certain number of piles for dynamic and static load test after full-scale construction, verify the quality of the pile body that the single pile vertical bearing capacity characteristic value meets the design requirements, and take reinforcing measures when it doesn't meet the requirements. Generally, test piles should be designed first in inexperienced or important projects. All projects are required to carry out construction test pile after pile foundation construction is completed, and quality assessment and acceptance will be carried out according to the test pile report.

------------------------- Significance of test pile -------------------------

1， To further determine the construction feasibility of the selected pile type, so as to avoid that the pile type is not suitable for the construction of this site or the pile bearing capacity is found to be much smaller than the calculated value provided in the geological report after the pile driving machine is fully installed on the site, and then the change of the pile type will delay the construction period and increase the cost.

2， Is to obtain the characteristic value of single pile bearing capacity. Since the value provided by the geological report is often conservative, it is possible to increase the pile bearing capacity and reduce the number of piles according to the static load report.

Trial piling is to provide first hand information on first time construction parameters for large scale pile driving operation, including effective pile length, rock penetration depth, slagging, filling degree, pile welding and bearing capacity.

1. When selecting pile type, pile length and pile end holding layer of engineering piles for test pile driving, the following provisions shall be complied with:

1) The engineering geological conditions at the location of test driven piles shall be representative.

2) In the process of test pile driving, tests shall be carried out one by one according to the soil layer that the pile end enters; when the holding layer is thicker, tests shall be carried out several times in the same soil layer.

2., The holding layer at the pile end shall be determined according to the bearing capacity and penetration relationship of the test pile driving results, combined with the geotechnical investigation report of the site.

END