Capacity Of Single Pile Research Articles

Finite Element Analysis of the Vertical Bearing Capacity of Single Piles in Tianjin Soft Soil Areas

The ABAQUS finite element software is used to calculate the vertical bearing capacity of single piles in Tianjin, and the finite element results are compared with the data gained through the in-situ static load pile foundation tests. It is found that the Young’s modulus of the soil at the bottom of the pile could have a important role in improving the vertical bearing capacity of single piles.

Research on Time Effect of Bearing Capacity of Jacked Pile in Soft Soil

Through the study on the characteristics of bearing capacity of jacked pile in soft soil, it is found that the increment of ultimate bearing capacity of the single pile is mainly determined by pile side resistance. The end resistance has little influence on the time effect of bearing capacity of pile. The relationship between ultimate bearing capacity and time can be expressed with logarithmic curve. According to penetration mechanism of jacked pile, the expansion of a series of spherical cavities in semi-infinite space is used to simulate the process of pile installation. Soil is assumed as Mohr-Coulomb material. Based on the theory of spherical cavity expansion, estimating formulas were proposed to calculate the ultimate side frictional resistance. Then the ultimate bearing capacity of single pile in different time can be obtained. Analyses show that the calculation results are close to the measured data and the error between computed and measured value is little. So it is acceptable for the formula to forecast bearing capacity of jacked piles.

Study on Vertical Bearing Capacity and Time Effect of the Jacked-in PHC Pipe Pile in the Cohesive Soil Area

The static load test of 34 jacked-in PHC pipe piles of medium length are performed in the cohesive soil area, the relationship between the vertical ultimate bearing capacity and the final pressure, and the time effect of vertical bearing capacity of the jacked-in PHC pipe pile are studied. The data of static load test is analyzed statistically with software SPSS, the regional empirical coefficient about the vertical ultimate bearing capacity and final pressure, and the time effect formula about vertical bearing capacity of the jacked-in PHC pipe pile in the cohesive area are obtained. According to the regional empirical coefficient, the pile pressing machine and counterweight can be chosen reasonably and the vertical ultimate bearing capacity of single pile can also be estimated rapidly, then we can instruct the design and construction of the jacked-in PHC pipe pile. According to the time effect formula, the vertical bearing capacity at different periods of the jacked-in PHC pipe pile can be obtained, the cost of the foundation engineering can be reduced by considering the time effect influence to the vertical bearing capacity of the jacked-in PHC pipe pile.

Research on Application of Seismic Piezocone Penetration Tests in Pile Foundation

According to the characteristics of installation about the penetrometer of seismic piezocone penetration tests (SCPTu) and the pile, a theoretical relationship between ultimate bearing capacity of single pile, time-effect of shaft bearing capacity of single pile, excess pore water pressure around the pile during pile driven and the data measured from SCPTu is developed based on the cavity expanded theory, the Terzaghi one-dimensional consolidation theory and effective stress theory. The result of field test in KunShan and the calculated result which used the theoretical relationship mentioned above are compared. The results indicate that the analytical solutions agree well with the in-situ tests, which show that the application of seismic piezocone penetration tests have wide range in the pile foundation.

Numerical Analysis of the Influence of Vertical Load on the Horizontal Bearing Capacity of Single Pile

It is a complicated progress of interaction between pile and soil when pile is under both vertical load and horizontal load. This paper analyzes the variation of stress, strain, deformation and deflection of the pile body by finite element numerical simulation of single bored concrete pile under vertical load together with horizontal load. Based on the existing research results, conclusions could be that the vertical load can increase horizontal bearing capacity of the pile in sandy soils, but horizontal bearing capacity of the pile in clayey soils is more complicated. Hope that the simulation can provide some references for the design of pile foundation.

Experimental investigation on seismic behavior of single piles in sandy soil

This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.

Predicting the Ultimate Bearing Capacity of Single Piles Based on CPTU

Six methods to determine axial pile capacity directly based on piezocone penetration test (CPTU) data are presented and evaluated. Analyses and evaluation were conducted on three types piles that were failed during pile load testing. The CPT methods, as well as the CPTU methods, were used to estimate the load carrying capacities of the investigated piles (Qp ). Pile load test were used to determine the measured load carrying capacities (Qm). The pile capacities determined using the different methods were compared with the measured pile capacities obtained from the pile load tests. Two criteria were selected as bases of evaluation: the best fit line for Qp versus Qm and the arithmetic mean and standard deviation for the ratio Qp /Qm. Results of the analyses showed that the best methods for determining pile capacity are the CPTU methods.

Corrected Cone Penetration Test Method for Predicting the Load Capacity of Single Pile

Based on the end bearing capacity and friction capacity obtained from high strain dynamic test, an adjusted equation was provided to calculate the pile load capacity. The equation was corrected again by pile load test results. Therefore, a suggested equation was finally established. Practical experience showed that, the corrected equation of cone penetration test method to estimate the load capacity of single pile performed better than that in the national code.

SVM Model Based on the Influencing Factors Evaluation and Prediction of Ultimate Bearing Capacity of Statically-Pressured Pipe Pile

The prediction accuracy of vertical ultimate bearing capacity of statically-pressured pipe pile is difficult to ensure with traditional methods, because it is influenced by comprehensive factors, such as pile body, soil around pile and construction conditions. In this paper, a support vector machine (SVM) model based on the influencing factors importance evaluation was established to predict the vertical ultimate bearing capacity of single pile. This method would consider grey relational analysis and variable projection importance analysis as the attribute preprocessor facilities, which could determine the vertical bearing character in typical geological conditions through the analysis results of these two methods. Then, the SVM model was established with the main factors influencing ultimate bearing capacity as input to predict ultimate bearing capacity of single pile. The results showed that this method would have better precision of prediction, and the established model would have better generalization ability, which would open up a new way for the theoretical analysis of bearing characters of statically-pressured pipe pile and provide references for future relevant research.

Reliability Analysis of Vertical Bearing Capacity of Pile Based on Static Load Tests

Based on the sample range theory in Mathematical Statistics, the general standard variance of vertical capacity of single piles is evaluated according to the data from static load tests, and a method is presented to evaluate the reliability of vertical bearing capacity of pile, of which distribution obeys normal distribution. Finally, results from the case study indicate that it is effective to evaluate the reliability using the method presented in this paper, and the number of tested piles specified in Technical Code for Testing of Building Foundation piles and determining sample range can be interpreted reasonably in theory. Meanwhile, it can give good references to designers to determine the design parameters according to testing piles.

Prediction Method of Vertical Ultimate Bearing Capacity of Single Pile Based on Support Vector Machine

By comprehensively analyzing the main factors affecting vertical ultimate bearing capacity of single pile, a prediction model of Support Vector Machine (SVM), which discusses the nonlinear relationship between vertical ultimate bearing capacity of single pile and influencing factors and analyzes the parameters on the performance of the model through sample knowledge learning, is established in this paper. The research results indicate that, SVM model, which is compared with BP neural networks model, possesses simple structure, flexible adaptability, high precision and powerful generalization ability, and can accurately reflect the actual mechanical characteristics of pile, therefore, SVM is an effective method for predicting vertical ultimate bearing capacity of single pile.

Effect of pile cap elevation below ground surface on lateral resistance of pile groups-experimental study

This paper presents the results of experimental study on model piles to show the effect of pile cap elevation below the ground surface and pile spacing on lateral resistance of single pile and pile groups driven in sand. Thirty five tests were performed on single piles and 2 x 2, 3 x 3, 4 x 4 pile groups at pile spacing equal to 3<i>D</i> and 5<i>D</i> with pile cap located at different elevation below the ground surface. Five cases for pile cap elevation were considered: case 1, bottom of pile cap in contact with the ground surface; case 2, top of pile cap at the ground surface elevation; case 3, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 2; case 4, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 3.33; and case 5, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 6.67. In all the studied cases, the pile tips located at the same elevation. The results of the tests show that the lateral carrying capacity of single pile and pile groups increase as the pile cap depth below the ground surface, <i>D_f</i>, increases and as the spacing between piles in the group increases.

Application of the catastrophe theory in ascertainment of vertical bearing capacity of single pile

PurposeCatastrophe theory can directly deal with discontinuity without any connection with the special inner mechanism, which makes it suitable for system research, whose inner action is unknown but outer one can be observed. There are many inner factors, which affect the bearing capacity of pile, it is different to ascertain bearing capacity of pile. The purpose of this paper is to present a new calculation method of bearing capacity of pile by the catastrophe theory.Design/methodology/approachThe cusp model of catastrophe theory and its expression are discussed in this paper. By means of mechanical model analysis, bearing capacity of pile is systematically studied coupling catastrophe steady mechanism with equilibrium conditions of single pile. The settlement of top pile is transformed into the normal form of cusp catastrophe. The relationship between the settlement of top pile and vertical bearing capability of pile is built.FindingsVertical bearing capacity of single pile was deduced by means of energy principle and catastrophe theory based on settlement of critical instability of pile.Research limitations/implicationsAccessibility and availability of the constitutive equation of concrete of pile and parameter are the main limitations which model will be applied.Practical implicationsA very useful reference for design processes engineers.Originality/valueThe estimated results of the example correspond to one of practical experience, which provides a basis for design of vertical bearing capacity of single pile.

Study and Application on Computational Methods for Ultimate Bearing Capacity of Single Pile

It is difficult and important to accurately calculate single pile ultimate bearing capacity during pile foundation design. Typical computational methods on single pile ultimate bearing capacity are contrastively analyzed in this paper. Contact element method on single pile ultimate bearing capacity is relatively accurate and economical, but it isn’t used in practical projects until now because its computational process is complicated. 343 different single pile ultimate bearing capacities are calculated with the contact element method in order to study a simple computational formula based on the contact element method. All data calculated are analyzed with a linear recursive multi-analysis program which is programmed with Fortran90. A simple computational formula on the contact element method is presented based on the analysis results. The simple computational formula, the experiential formula in the code, the contact element method and the static load experiment method are respectively used to calculate single pile ultimate bearing capacity in two practical projects in order to test the simple computational formula. The results show that the simple computational formula is relatively accurate. Some advice is presented based on the analysis results.

Analysis of static axial load capacity of single piles and large diameter shafts using nonlinear load transfer curves

A modified analytical model is proposed in this study for the analysis of pile axial load capacity with the load transfer method using nonlinear T-z and Q-z curves to model soil-pile behavior in skin friction or side shear and end bearing respectively. The method uses a three-dimensional (3D) pile model using solid finite elements with nonlinear load transfer curves resolved into components and mobilized around the pile perimeter. The use of multiple T-z component springs is demonstrated to accurately capture the total side resistance of the pile. The 3D pile method produces results of predicted pile axial load capacities from the load-settlement curves comparable to the one-dimensional analysis (1D) method. For a combined vertical and lateral loading on the pile, the proposed 3D pile method can address the limitation of the 1D pile method having vertical and lateral springs only acting at the pile center without rotational springs, which neglects the contribution of the side shear in the computation of pile bending moments. In the case of 3D pile model the moment or couple developed by the side shear around the perimeter can be taken into account, where this moment can be significant especially in strong soil material or in the case of large diameter pile/shafts.

Full-scale pile tests in sand and development of a computer program for predicting load capacity

An interactive computer program GLAMPILE has been developed for predicting the static load capacity of single piles formed in any soil profile. A variety of well-known prediction methods have been incorporated into the program, including (i) soil mechanics based formulae; (ii) direct and indirect cone penetration test (CPT) based methods with and without accounting for scale effects of the cone on pile base capacity; and (iii) a new CPT-based method that considers the effects of “critical depth” and shaft resistance distribution, although the method has only been calibrated for relatively short piles. GLAMPILE can cope with different pile types installed with or without a permanent casing. The program has been applied to predict the axial capacities of 11 piles that were recently installed in sand and statically loaded to failure. Results from the soil mechanics procedures indicate increases, on the in situ value, of the earth pressure coefficient by up to 37%, which lies within the range 0%–100% recommended in the literature. The best CPT-based prediction method applied yields a mean (µ) and coefficient of variation (COV) of predicted to measured pile head capacity (Puh(p)/Puh(m)) of 0.83 and 0.12, respectively. Scale effects are shown to be nominal for the cases analysed. An improved method is recommended, which yields µ = 1.00 and COV = 0.10, implying higher accuracy and reliability compared with the other methods.Key words: piles, cone penetration test, static and dynamic load test, modular program.

Prediction of Bearing Capacity of Friction Piles in Soft Louisiana Soils by Cone Penetration Test

A comparison of four different methods for predicting the axial compression capacity of single piles using cone penetration test (CPT) results is presented. Nineteen pile load tests and parallel CPT soundings conducted close to the piles were identified and documented from the Louisiana Department of Transportation and Development archives. Piles with different sizes and lengths were investigated. The four prediction methods selected were the Schmertmann method, the de Ruiter and Beringen method, the French Central Bridge and Pavement Laboratory (LCPC) method, and the Tumay and Fakhroo method. An evaluation scheme was performed using these methods to assess their capability to reliably predict the axial compression capacity of piles installed in soft Louisiana soils. The predicted pile capacities obtained by the different methods were compared with the measured pile capacities obtained from pile load tests. Analysis of the results showed that the Schmertmann, de Ruiter and Beringen, and Tumay and Fakhroo methods predicted the ultimate compression capacities of piles installed in soft Louisiana soils with a reasonable accuracy. The LCPC method underpredicted the measured capacities of these piles.

Estimation of Vertical Capacity of Single Piles Considering Uncertainty

The uncertainty in soil parameters and the models that are used for predicting the vertical load-carrying capacity of single piles are addressed. The uncertainty is expressed in terms of fuzzy numbers and incorporated explicitly in the solution process. A new approach is developed by which the model uncertainty, the uncertainty associated with different empirical methods for predicting pile capacity, is reduced through the use of an aggregation technique. The weights used in the aggregation are determined on the basis of sensitivity analysis of each pile-capacity prediction model. Case studies are presented to illustrate the new approach and the developed computer program. The comparison between the predicted and the measured ultimate pile capacity indicates that the predicting capability of the developed computer program is very good.

Discussion of “ Model for Capacity of Single Piles in Sand Using Fuzzy Sets ” by C. H. Juang, J. L. Wey, and D. J. Elton (December, 1991, Vol. 117, No. 12)

Discussion of “ <i>Model for Capacity of Single Piles in Sand Using Fuzzy Sets</i> ” by C. H. Juang, J. L. Wey, and D. J. Elton (December, 1991, Vol. 117, No. 12)

Closure to “ Model for Capacity of Single Piles in Sand Using Fuzzy Sets ” by C. H. Juang, J. L. Wey, and D. J. Elton (December, 1991, Vol. 117, No. 12)

Closure to “ <i>Model for Capacity of Single Piles in Sand Using Fuzzy Sets</i> ” by C. H. Juang, J. L. Wey, and D. J. Elton (December, 1991, Vol. 117, No. 12)