DESIGN OF CFA PILES IN GRANULAR SOILS

Design of CFA piles in granular soils



Abstract

This paper is the Review of the main provisions of CFA piles: “geotechnical engineering.” In the presentation we tried to convey the spirit of the document, to emphasize its similarities and differences with the domestic regulations of United Kingdom.

Design of CFA piles in granular soils

Introduction

In different aspects, the static capacity of a well structured continuous flight auger (CFA) pile can be considered to fall among that of a shaft that is to be drilled and pile which is driven. This concept is usually related to different variations in lateral stress among the settlement and installation of different types of pile. During the phase of making a drilled shaft, the stress soil may tend to reduce or stay unchanged in the vicinity of the pile excavation.

During the process of a pile which is driven, the process of pile driving delocalizes the soil in lateral direction by increasing the stress on the surrounding soil. In the scenario of a typical CFA based pile construction, the stresses in the soil try to remain close to the pre construction stress value which is usually similar to the shaft which has been drilled. This all is performed while the making of drilled displacement (DD) of piles tends to enhance the stress in the surroundings of the soil which is similar to the pile which is driven.

It is understandable to CFA pile capacity by using the techniques made particularly for driven piles and shafts due to the load settlement behavior of CFA piles are similar. But, some techniques have been made particularly for CFA piles (Geotechnical Engineering, 2007).

General Provisions

Geotechnical impact of CFA piles

The load on the structure of the soil, backfill or groundwater; comparative experience

Reliable information about the behaviour of similar structures in similar soils, soil

Rocky or discontinuous rock or mound before construction; structure

Organized by the combination of components, including backfill, designed for strength and rigidity, the derived value

The value of geotechnical parameters obtained theoretically or empirically correlation of experimental results.

Fundamentals of geotechnical engineering

The characteristic value of the index of ground is the value of a confidence level of 95%. In most practical cases, the statistics cannot be used because of the lack of experimental data. In these cases, the EC 7 defines the characteristic value as a “conservative estimate of the indicator.” The intrinsic value of this parameter may be a lower value that is less than the most probable value or upper value of which is greater than the most probable value. Each calculation should use the most unfavourable combination of lower and upper values of the independent parameters.

The Project geotechnical parameter value is determined by dividing (multiplication) of the characteristic (representative) value to the private safety factor. All private safety factors greater than unity and introduced into the formula (in either the numerator or the denominator) in the most unfavourable combination enhance the safety ...