Geomechanics of Soft Ground Improvement by Perforated Piles: Review and Case Study

Civil Infrastructure built on soft and compressible soil is likely to collapse due to undrained shear failure or unacceptable settlement of supporting foundations. Incorporation of adequate ground improvement technique with the aim of upgrading the strength and stiffness of the weak soil is essential in such cases. Amongst various established methods adopted worldwide for improving soft ground, using perforated piles is a relatively emerging technique. Such piles not only transmit the structural load into the subsoil beneath in a manner similar to the conventional piles, but also assist in radial consolidation of soft soil due to perforated side walls. This paper presents a brief overview on the investigations carried out on this new technique. Also, a typical case study has been presented. As observed, the axial pile capacity progressively increased while settlement reduction took place, with accelerated radial consolidation.

Factors Influencing Pile Friction Bearing Capacity: Proposing a Novel Procedure Based on Gradient Boosted Tree Technique

In geotechnical engineering, there is a need to propose a practical, reliable and accurate way for the estimation of pile bearing capacity. A direct measure of this parameter is difficult and expensive to achieve on-site, and needs a series of machine settings. This study aims to introduce a process for selecting the most important parameters in the area of pile capacity and to propose several tree-based techniques for forecasting the pile bearing capacity, all of which are fully intelligent. In terms of the first objective, pile length, hammer drop height, pile diameter, hammer weight, and N values of the standard penetration test were selected as the most important factors for estimating pile capacity. These were then used as model inputs in different tree-based techniques, i.e., decision tree (DT), random forest (RF), and gradient boosted tree (GBT) in order to predict pile friction bearing capacity. This was implemented with the help of 130 High Strain Dynamic Load tests which were conducted in the Kepong area, Malaysia. The developed tree-based models were assessed using various statistical indices and the best performance with the lowest system error was obtained by the GBT technique. The coefficient of determination (R2) values of 0.901 and 0.816 for the train and test parts of the GBT model, respectively, showed the power and capability of this tree-based model in estimating pile friction bearing capacity. The GBT model and the input selection process proposed in this research can be introduced as a new, powerful, and practical methodology to predict pile capacity in real projects.

Three Dimensional Analysis of Pile-raft Foundations on Clay, Menteng-Jakarta

Piled-raft foundation is a combination of pile foundation and raft foundation. Bearing capacity of piled-raft foundation yielded from contribution of both pile capacity and raft capacity. Most of the time, design of pile foundation is assumed that all load is solely carried by pile and the capacity of raft is ignored. In this study, three-dimensional finite element analysis was applied to analyze the load percentage that can be carried by raft. A case study, which is located in Central Jakarta, Indonesia, was modeled to investigate this issue. This project was instrumented with two pressure cells where the data were used to verified the model and the load distribution. The analysis results showed good agreement with the measurement data, where the load carried by the raft is around 33-42%.

OPTIMIZATION OF GROUTING METHOD AND AXIAL PERFORMANCE OF PRESSURE GROUTED HELICAL PILES

Pressure grouted helical pile (PGHP) is an innovative piling system that allows a significant increase in helical pile capacity with relatively low additional cost. The pile is constructed by applying pressurized grout during the installation of conventional helical piles. The grout is injected into the ground through two nozzles welded to the hollow pile shaft. This paper presents a comprehensive laboratory study to investigate the effect of three different nozzles configurations on the shape and axial performance of PGHP. The results reveal a significant increase in the PGHP shaft resistance over that of the un-grouted helical pile due to the formation of a continuous grout column with a larger diameter, higher friction angle at the pile/soil interface, and higher lateral earth pressure around the pile. The shape and diameter of the created grout column depend on the nozzles configuration used for grout injection. An increase in the end-bearing resistance is observed due to grout dissipation into the supporting soil voids. The study also shows that PGHPs installed with the third nozzles configuration have the fastest installation rate and the highest compression and pullout resistances. Thus, the third nozzles configuration is recommended for PGHP construction.

Analisis Kekuatan Struktur Bangunan Dermaga Kayu di Babo Teluk Bintuni, Papua Barat

Analysis of structural strength to the conditions of the jetty Port Babo of Teluk Bintuni, West Papua is important to ensure the stability of the against external loads and forces. The purpose of this research is to analyse and evaluate the strength of structures, as well as assess the durability of jetty structures. Modeling using the SAP2000 program corresponds to as built drawing. The results of the calculation of the working load include dead loads, live loads, ship berth, ship mooring force, current force, wave force, and earthquake force. Energy due to ship collision loads and vessel berthing force can be reduced using a fender designed using rubber fenders seibu V300H. The results of the structural analysis show that the number of combined variants is sufficient up to the shape mode 12. The dynamic earthquake shear forces in the x and y directions are still smaller than the static shear forces, so it needs to be multiplied by a scale factor of 2,9. The deviation that occurs in the structure is still smaller than the allowable deviation of 350 mm. Beams are designed using reinforcement with diameter 22 mm and 25 mm. The stress ratio value at the pile meets the pile capacity. It can be said that overall the Babo Teluk Bintuni wharf is safe from the working load.

The Effect of w/c Ratio of Compacted Bored Pile to Friction Resistance of Unjani Clay

The small scale physical model of drum type was set-up to obtain the effect of water cement ratio (w/c) to pile capacity and original soil. The simulation of the process of providing bored piles model, soils model, installation and tests (pile loading tests and direct shear tests) under different water cement ratio of mortar and various moisture content of clay were done. The results reveal that the higher water content of original clay the bigger friction resistance, α value as clay soil is softer and the optimum w/c-ratio (w/c = 0,4) provides more pile capacity. It is understandable that water plays an important role, contributes to the change of surrounding clay properties. The improvement of Su ( % increase) due to compaction of concrete in bored pile, migration of moisture and reaction with surrounding clay leads to take benefit of design and construction of bored pile in clay soil for the sake of efficiency and stability.