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Identification of residual force in static load tests on instrumented screw displacement piles

Krasiński Adam, Wiszniewski Mateusz

Studia Geotechnica et Mechanica

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2021

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Vol. 43, nr 4

438--451

EN

Occurrence of the so-called residual force of an unknown value significantly disturbs interpretation of static load tests performed on piles equipped with additional measuring instruments. Screw displacement piles are the piling technology in which the residual force phenomenon is very common. Its formation mechanism is closely related to the installation method of this type of piles, which initiates generation of negative pile skin friction without any additional external factors. Knowledge of the value and distribution of a residual force (trapped in a pile shaft before starting the load test) is a necessary condition for the proper interpretation of instrumented pile test results. In this article, a clear and easy-to-use method of residual force identification, based on the analysis of shaft deformations recorded during pile unloading is presented. The method was successfully verified on two pile examples and proved to be effective and practical.

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Displacement piles - classification and new methods for the calculation of bearing capacity

Gwizdała Kazimierz, Więcławski Paweł

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2020

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Vol. 29, No. 3

308--318

EN

The paper presents technological changes concerning not only the method of construction, but also the materials used. Another aspect is the methods of calculating the load-bearing capacity and settlement of piles. With acceptance for use the PN-EN:1997-1:2008 standard in 2010, it was necessary to change the approaches applied that based on many years of experience and tradition. The best method in this case is to forecast the full load-settlement characteristics. On the basis of the collected data, a comparative analysis of particular displacement piles technologies was made. The usefulness of individual methods of load-bearing capacity calculation depending on the pile technology was determined.

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

Krasiński A.

Studia Geotechnica et Mechanica

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2012

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Vol. 34, nr 4

41--51

EN

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.

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Zastosowanie przemieszczeniowych pali wkręcanych w podłożu uwarstwionym na przykładzie realizacji obiektu w warunkach gruntowych delty Wisły

Gwizdała K., Krasiński A.

Inżynieria i Budownictwo

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2009

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R. 65, nr 3

133-136

PL

Przedstawiono rozwiązanie posadowienia budynku na palach oraz wyniki statycznych badań zastosowanych pali. Zaobserwowano, że pale wkręcane charakteryzują się nietypowymi warunkami wykonania oraz specyficzną pracą w gruncie. Do opisu krzywych osiadania zastosowano analizę z wykorzystaniem funkcji transformacyjnych oraz wyników sondowań CPT. Poprawność rozwiązań projektowych została potwierdzona pomiarami geodezyjnymi osiadań budynku.

EN

The example of experience regarding construction founded on full displacement screwed piles in highly layered subsoil near Gdańsk is presented and discussed, together with static load test results of the piles. It is found that full dispfacement strewed piles behave in different way during its installation as well as its regular service than typical piles. For the determination of settlement curve, load-transfer functions formula for piles together with CPT results were applied. The survey measurements performed on the structure during its operational period confirmed correctness of the applied foundation solutions.