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Use of the laboratory tests of soil modulus in modelling pile behaviour

Dyka I.

Studia Geotechnica et Mechanica

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2012

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Vol. 34, nr 3

53--61

EN

This article deals with the question of theoretical description of behaviour of a single pile rested in a layered soil medium. Particular attention is paid to soil modulus which is used in calculation method for pile load-settlement curve. A brief analysis of the results obtained by laboratory tests to assess soil modulus and its nonlinear variability has been presented. The results of tests have been used in triaxial apparatus and resonant column/torsional shear device. There have also been presented the results of load-settlement calculation for a single pile under axial load with implementation of different models of soil modulus degradation. On this basis, possibilities of using particular kinds of laboratory tests in calculation procedure of foundation settlement have been presented as well as further developments of them.

2

Analityczna metoda prognozowania krzywej osiadania pala pojedyńczego

Gwizdała K., Dyka I.

Inżynieria i Budownictwo

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2001

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R. 57, nr 12

729-733

PL

Przedstawiono metodę prognozowania krzywej osiadania pala pojedynczego, umożliwiającą wiarygodny opis pracy pala w dowolnie uwarstwionym podłożu gruntowym. Metoda uwzględnia zmianę modułu odkształcania warstw gruntowych w funkcji mobilizowanego oporu gruntu na pobocznicy i pod podstawą pala. Uzyskiwane wyniki zweryfikowano wykorzystaniem próbnych obciążeń pali.

EN

The method for prediction of load settlement curve of a single pile has been presented. This method enables to reliable description of single pile behaviour in freely layered soil profile. The propose method takes into account the non-linear change of soil deformation modules with soil resistance mobilized along the shaft and under the base of a pile.

3

Spoluposobenie vodorovne zatazenej osamelej piloty so zemnym prostredim

Tothova D., Duraj J.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2000

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z. 32[180], cz.1

563-570

EN

Foundation design is based on providing a means of transmiting the loads from a structure to the underlying soil without a soil shear failure or causing excessive settlements of the soil under imposed loads. For that reason in many cases is necessary to found the structure on piles. The resultant of imposed load may be generally oriented in space. The action on the pile head we can replace by its three components: vertical force, horizontal force and applied moment. The calculation model depends on loading mode and idealization of soil medium. For the model based on modulus of horizontal subgrade reaction we consider constant or linear increasing proportionality between the stress and displacement in each point of the pile - soil system. The remaining problem in the lateral-pile solution is to input a reasonable (or correct if known) value of lateral subgrade modulus. More suitable is to model a soil medium like linear homogeneous isotropic half-space. The solution of the problem is based on the application of approximate numerical methods. The continuous contact between the pile and soil surface is replaced by a system of single bonds in the discrete points. It means that instead of continuously distributed reactions we consider the uniformly distributed horizontal pressure on rectangular area from the side of the subsoil. The problem leads to the solution of statically indeterminate structure. The system for determination of unknowns consists of the deformation conditions which express the same displacements in the corresponding discrete points of slab structure and subsoil surface and conditions which express the equilibrium of contact forces and acting loads. These mixed conditions can be written in matrix form. The displacements according to the computation level and internal forces of the pile we determine by using the finite element method. The stiffness matrix and the load parameter vector of the finite element we derived for the pyramidal bar shape due to linearly changing perpendicular action. The determination of horizontal displacements of the soil due to uniformly distributed load we derived from formula. On the base of described calculation model we worked up the program. On illustrative example we present some results of laterally loaded pile with prismatic or pyramidal shape. From diagrams is evident the better resistance of pyramidal pile with the same volume of material as prismatic one.