Negative Skin Friction on Piles Based on Finite Strain Consolidation Theory and the Nonlinear Load Transfer Method

김형주,Jose Leo C. Mission 대한토목학회 2009 KSCE JOURNAL OF CIVIL ENGINEERING Vol.13 No.2

The development of dragload and downdrag on single piles in consolidating ground is investigated in this study with a simplified one-dimensional soil-pile model that combines the nonlinear load transfer method and finite strain consolidation theory to analyze soil-pile interaction under the effects of negative skin friction. In order to directly relate the soil settlements and effective stresses through the strain as a function of time and depth during the consolidation process, the prediction of the soil settlements imposing downdrag are based on Mikasa’s generalized one-dimensional consolidation theory that are formulated in terms of finite strain. An illustrative example and a case study of test pile were analyzed and predicted results of dragload and pile shortening by the presented model were shown to be in fair agreement with measured reference data. The model presented in this study offers a simple and flexible method for the analysis of a variety of soil-pile interaction problems under negative skin-friction that can account for nonlinearity of the soil and pile, a rigid and deformable bearing stratum, and can be applicable for the analysis of floating and endbearing piles as well as for shafts socketed in rocks. The development of dragload and downdrag on single piles in consolidating ground is investigated in this study with a simplified one-dimensional soil-pile model that combines the nonlinear load transfer method and finite strain consolidation theory to analyze soil-pile interaction under the effects of negative skin friction. In order to directly relate the soil settlements and effective stresses through the strain as a function of time and depth during the consolidation process, the prediction of the soil settlements imposing downdrag are based on Mikasa’s generalized one-dimensional consolidation theory that are formulated in terms of finite strain. An illustrative example and a case study of test pile were analyzed and predicted results of dragload and pile shortening by the presented model were shown to be in fair agreement with measured reference data. The model presented in this study offers a simple and flexible method for the analysis of a variety of soil-pile interaction problems under negative skin-friction that can account for nonlinearity of the soil and pile, a rigid and deformable bearing stratum, and can be applicable for the analysis of floating and endbearing piles as well as for shafts socketed in rocks.

A Program Development for Prediction of Negative Skin Friction on Piles by Consolidation Settlement

김형주,Jose Leo C. Mission 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.9

The microcomputer program PileNSF (Pile Negative Skin Friction) is developed by the authors in a graphical user interface (GUI) environment using MATLABⓇ for predicting the bearing capacity of a pile embedded in a consolidating ground by surcharge loading. The proposed method extends the one-dimensional soil-pile model based on the nonlinear load transfer method in OpenSees to perform an advanced one-dimensional consolidation settlement analysis based on finite strain. The developed program has significant features of incorporating Mikasa’s finite strain consolidation theory that accounts for reduction in the thickness of the clay layer as well as the change of the soil-pile interface length during the progress of consolidation. In addition, the consolidating situation of the ground by surcharge filling after the time of pile installation can also be considered in the analysis. The program analysis by the presented method has been verified and validated with several case studies of long-term test on single piles subjected to negative skin friction. Predicted results of negative skin friction (downdrag and dragload) as a result of long term consolidation settlement are shown to be in good agreement with measured and observed case data.

Analysis of Static Axial Load Capacity of Single Piles and Large Diameter Shafts using Nonlinear Load Transfer Curves

Hyeong Joo Kim,Jose Leo C. Mission,Il Sang Park KOREAN SOCIETY OF CIVIL ENGINEERS 2007 KSCE JOURNAL OF CIVIL ENGINEERING Vol.11 No.6

<P>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.</P>

Analysis of Axial Load Capacity of Single Piles and Shafts Using Nonlinear Load Transfer Curves

김형주(Kim Hyeong Joo),Jose Leo C. Mission 대한토목학회 2007 대한토목학회 학술대회 Vol.2007 No.10

Stochastic cost optimization of ground improvement with prefabricated vertical drains and surcharge preloading

Kim, Hyeong-Joo,Lee, Kwang-Hyung,Jamin, Jay C.,Mission, Jose Leo C. Techno-Press 2014 Geomechanics & engineering Vol.7 No.5

The typical design of ground improvement with prefabricated vertical drains (PVD) and surcharge preloading involves a series of deterministic analyses using averaged or mean soil properties for the various combination of the PVD spacing and surcharge preloading height that would meet the criteria for minimum consolidation time and required degree of consolidation. The optimum design combination is then selected in which the total cost of ground improvement is a minimum. Considering the variability and uncertainties of the soil consolidation parameters, as well as considering the effects of soil disturbance (smear zone) and drain resistance in the analysis, this study presents a stochastic cost optimization of ground improvement with PVD and surcharge preloading. Direct Monte Carlo (MC) simulation and importance sampling (IS) technique is used in the stochastic analysis by limiting the sampled random soil parameters within the range from a minimum to maximum value while considering their statistical distribution. The method has been verified in a case study of PVD improved ground with preloading, in which average results of the stochastic analysis showed a good agreement with field monitoring data.

Spatial interpolation of SPT data and prediction of consolidation of clay by ANN method

Kim, Hyeong-Joo,Dinoy, Peter Rey T.,Choi, Hee-Seong,Lee, Kyoung-Bum,Mission, Jose Leo C. Techno-Press 2019 Coupled systems mechanics Vol.8 No.6

Artificial Intelligence (AI) is anticipated to be the future of technology. Hence, AI has been applied in various fields over the years and its applications are expected to grow in number with the passage of time. There has been a growing need for accurate, direct, and quick prediction of geotechnical and foundation engineering models especially since the success of each project relies on numerous amounts of data. In this study, two applications of AI in the field of geotechnical and foundation engineering are presented - spatial interpolation of standard penetration test (SPT) data and prediction of consolidation of clay. SPT and soil profile data may be predicted and estimated at any location and depth at a site that has no available borehole test data using artificial intelligence techniques such as artificial neural networks (ANN) based on available geospatial information from nearby boreholes. ANN can also be used to accelerate the calculation of various theoretical methods such as the one-dimensional consolidation theory of clay with high efficiency by using lesser computation resources. The results of the study showed that ANN can be a valuable, powerful, and practical tool in providing various information that is needed in geotechnical and foundation design.