Proposal for calculating the bearing capacity of screw displacement piles in non-cohesive soils based on CPT results

Abstract

Screw displacement pile technology is relatively new and is still being developed. A specific characteristic of those piles is their very considerable influence on soil properties during the installation, which renders classical bearing capacity calculation methods insufficient. Some methods for calculating the bearing capacity of screw displacement piles have already been presented in literature, for example, by Bustmante and Gianesselli [2], [3], Van Impe [17], [18], Maertens and Huybrechts [15], Ne Smith [16] as well as Basu and Prezzi [1]. This paper proposes a new method of calculating the bearing capacity of screw displacement piles in non-cohesive soil which is based on CPT results. It has been devised as a result of research project No. N N506 432936 [11], carried out in 2009-2011. At 6 experimental sites screw displacement pile static loading tests were carried out together with CPTU tests of the subsoil. The results allowed us to establish soil resistances along the shaft ts as well as under the pile base qb and their correlations to the CPT soil cone resistances qc. Two approaches, both adapted to the general guidelines of Eurocode 7 (EC7) [20], were proposed: a classical approach and the second approach with load transfer functions application.

The Analysis of Soil Resistance During Screw Displacement Pile Installation

“…On the base of it, we will be able to know what energy of piling machine is required to install the designed screw displacement pile. This prediction method can be applied to design screw displacement piles together with the author's own method for pile bearing capacity calculation [7] or with other calculation methods, proposed, for example, by Bustamante and Gianeselli [1], [2], Maertens and Huybrechts [8] or by NeSmith [9].…”

Vibro piles performance prediction using result of CPT

“…Classical transformation functions, whose idea is to fit the settlement curve to the calculated ultimate bearing capacity, enable to plot the hyperbolic characteristics of settlement [9,[12][13]. The hyperbola does not represent the actual shape of the Q-s curve for Vibro piles.…”

“…Pile deformation is described in terms of elastic solutions, whereas load-settlement relationship is determined by iterative procedure. Load-transfer functions method enables the evaluation of entire range of settlement curves using the results of CPT [9,[12][13].…”

Integrated data-driven and mechanics-based modeling framework for pile design

“…A number of empirical axially loaded pile load-transfer curves (also termed as t-z curves) have been developed for various the soil types, pile types, installation methods, etc. The major load-transfer curves include but are not limited to the linear curve [25,29], tri-linear curve [9], hyperbolic curve [3,7,12], and root curve [3,18,30]. To better understand the key parameters involved in the load-transfer curves, these empirical curves are standardized and listed in Table 1.…”