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

2012 ◽  
Vol 34 (4) ◽  
pp. 41-51 ◽  
Author(s):  
Adam Krasiński

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.

2016 ◽  
Vol 53 (4) ◽  
pp. 696-707 ◽  
Author(s):  
Hai-lei Kou ◽  
Jian Chu ◽  
Wei Guo ◽  
Ming-yi Zhang

A large-scale field testing program for the study of residual forces in pre-stressed high-strength concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m in embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with fiber Bragg grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual force on the interpretation of the load transfer behavior is discussed. The field data show that residual force along the installed pile increases approximately exponentially to the neutral plane and then reduces towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles significantly affect the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane and underestimate the shaft resistance at positions below the neutral plane, and the toe resistance for an open-ended PHC pipe piles founded in stratified soils.


2015 ◽  
Vol 37 (4) ◽  
pp. 83-93 ◽  
Author(s):  
Bogumił Wrana

Abstract The article is a review of the current problems of the foundation pile capacity calculations. The article considers the main principles of pile capacity calculations presented in Eurocode 7 and other methods with adequate explanations. Two main methods are presented: α – method used to calculate the short-term load capacity of piles in cohesive soils and β – method used to calculate the long-term load capacity of piles in both cohesive and cohesionless soils. Moreover, methods based on cone CPTu result are presented as well as the pile capacity problem based on static tests.


2018 ◽  
Vol 55 (5) ◽  
pp. 653-665 ◽  
Author(s):  
Young-Eun Jang ◽  
Jin-Tae Han

The waveform micropile is an advanced construction method that combines the concept of the conventional micropile with the jet grouting method. This new form of micropile was developed to improve shaft resistance, and has enabled a higher bearing capacity and greater cost efficiency. Two field tests were conducted to examine field applicability and to verify the effects of bearing capacity enhancement. In particular, waveform micropile construction using the jet grouting method was performed to evaluate the viability of waveform micropile installation. After testing, the surrounding ground was excavated to check the shape of the waveform micropile. The result showed that waveform micropiles can be installed by adjusting the grouting time and pressure. In the loading tests, the bearing capacity of the waveform micropile increased by 1.4–2.3 times that of the conventional micropile, depending on the shape of the micropile. The load transfer analysis using the strain gauge data showed that the waveform micropile increases the shaft resistance in the soil layer. This not only decreases pile settlement, but also contributes to the increase of overall bearing capacity. The overall results clearly demonstrate that the waveform micropile is an enhanced construction method that can improve bearing capacity.


1989 ◽  
Vol 26 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Marius Roy ◽  
Luc Tanguay

The penetrometer test has been used to determine the bearing capacity of driven and jacked-in single piles in sensitive clays. The cases presented in this paper were carried out on two sites with steel, concrete, and wooden piles. The bearing capacities calculated on the basis of the results of penetrometer tests show that this approach has a good potential and at the same time is simple and fast. It has been possible to obtain a calibration by a comparison with the loading tests carried out on each of the piles. Taking into account the low strength of some of our clays, experience has to be gained in order to adapt the lateral unit friction curves to our clays. This approach also has the advantage of allowing the determination of the bearing capacity of wooden piles and of taking into account the conical effect when determining the lateral friction component. Key words: penetrometer test, piles, bearing capacity, cohesive soils, point resistance, lateral friction, steel, concrete, wood. [Journal translation]


2014 ◽  
Vol 20 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Andrzej Olchawa ◽  
Andrzej Zawalski

Abstract Bearing capacity of cohesive soils was calculated based on PN-B-03020:1981P and Eurocode 7. Strength parameters of cohesive soil modified by the authors: shear strength in undrained conditions cu, effective cohesion c' and effective friction angle φ' were adopted for calculations acc. to Eurocode 7. Values of these parameters depend on a leading parameter - liquidity index IL. Bearing capacity was calculated for two pad foundations of a size B × L = 2.0 × 3.0 m and 1.5 × 2.0 m and for one 2.0 × 14.0 m strip foundation. The capacity calculated acc. to EC 7 was reduced by multiplying by a factor α = 0.87 to account for different bearing capacity coefficients in Polish Norms and Eurocodes. Performed calculations showed comparable bearing capacity of substratum irrespective of adopted norms EC 7 and PN for foundation pads. In all analysed cases, however, the bearing capacity of foundation strips calculated acc. to Eurocode 7 was higher than those calculated acc. to PN-B-03020:1981P. The reason is in the values and ways of accounting partial security coefficients and in differences in the values of shape coefficients used in the equation for ultimate bearing resistance of soil substratum.


2019 ◽  
Vol 9 (17) ◽  
pp. 3468 ◽  
Author(s):  
Yongrui Wang ◽  
Junwu Xia ◽  
Renwei Ma ◽  
Bo Xu ◽  
Tonglei Wang

Modular buildings have the highest levels of precasting in the current building system. There are some defects in present modular connections, such as the difficulties of construction, the weakening of the bearing capacity of beams or columns, and damage to decorations. This paper presents an innovative modular connection with installed bolts in the columns. Two symmetrical monotonous static loading tests were conducted to explore the flexural behavior of the innovative connection. Meanwhile, the moment–rotation relations, destruction process, ultimate bearing capacity, stiffness classification and internal stress distribution were analyzed. The results showed that the specimen S1 with smaller diagonal stiffeners lost its bearing capacity due to the failure of the welding seam, and the extreme moment was 169 kN·m. The failure mode of S2 with large diagonal stiffeners was beam buckling, and the extreme moment was 209 kN·m. The stress of diagonal stiffeners and the join between the upper beam and stiffeners increased rapidly. Stiffeners can increase the stiffness and load-bearing capacity. The connection failures occurred on the beam or beam–column joints, while the connection between modules remained undamaged, which showed that the new connection has a good bearing capacity under the action of bending moment and pressure.


Author(s):  
Е.Г. Хитров ◽  
Е.В. Котенев ◽  
А.В. Андронов ◽  
Г.С. Тарадин ◽  
В.Е. Божбов

Статья посвящена выявлению взаимосвязей физико-механических свойств, конусного индекса и несущей способности различных типов связных грунтов и почвогрунтов. Материалом для исследования служат справочные данные и теоретические формулы для расчета несущей способности и физико-механических свойств грунта. Методы исследования – вычислительный эксперимент, аппроксимация расчетных данных, метод наименьших квадратов. Использована отечественная методика расчета несущей способности деформируемого массива грунта, находящегося под воздействием штампа, учитывающая мощность слоя, геометрию пятна контакта, сцепные свойства и удельный вес грунта, отклонение направления воздействия штампа от нормали к поверхности грунта. Согласно результатам расчетов несущая способность связного грунта определяется удельным сцеплением и углом внутреннего трения и выражается степенным уравнением независимо от типа связного грунта. На втором этапе исследования проведено сопоставление модуля деформации и конусного индекса связного грунта со сцепными его свойствами и несущей способностью. Значения модуля деформации, модуля сдвига, удельного сцепления и угла внутреннего трения получены расчетным путем для грунтов различной пористости и консистенции в зависимости от типа грунта. Значения конусного индекса определены по теоретическому решению задачи о вдавливании конического индентора в полупространство. Установлено, что расчетное значение несущей способности глины, суглинка, супеси, лесного и заболоченного почвогрунтов связано с модулем деформации также степенной зависимостью, коэффициенты которой зависят от типа грунта. Расчетное значение несущей способности глины, суглинка, супеси, лесного и заболоченного почвогрунтов можно получить по конусному индексу, который определяется зондированием, а также при помощи степенного уравнения, коэффициенты которого определяются типом связного грунта. The article devotes to studying the relationship of mechanical properties, cone index and bearing capacity of various types of cohesive soils. The material for the study are reference data and theoretical formulas for calculating the bearing capacity and mechanical properties of the soil. Research methods include computational experiment, approximation of the calculated data, the least squares method. The article uses domestic method of calculating the bearing capacity of a deformable soil layer under influence of a stamp, taking into account the layer thickness, geometry of the contact patch, cohesive properties and specific weight of the soil, deviation of stamp direction from the normal to the soil surface. According to the results of calculations, bearing capacity of cohesive soils is determined by the inner cohesion and angle of internal friction and expresses by a power equation regardless of the cohesive soil type. At the second stage, the study makes comparison of the deformation modulus and the cone index of cohesive soil with its cohesive properties and bearing capacity. The values of deformation modulus, shear modulus, inner cohesion and angle of internal friction obtained for soils of different porosity and consistency, depending on the soil type. The values of the cone index are determined by theoretical solution of the problem of penetration of conical indenter into half-space. It has been established that calculated value of bearing capacity of clay, loam, sandy loam, forest and marshy soil is associated with the deformation modulus also by power dependence, the coefficients of which depend on the type of soil. The calculated value of bearing capacity of clay, loam, sandy loam, forest and marshy soil can be obtained by the cone index, which is determined by sounding, also using a power equation, the coefficients of which are determined by the type of cohesive soil.


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