Model test on the axial capacity of displacement ribbed piles

The capacity, hence the load-settlement behaviour of a pile is governed by the collective behaviour of the base and shaft. It is highly desirable, sustainable and economical to accommodate the increasing demand for deeper and wider foundations through the use of higher capacity piles. This research investigated the performance of preformed displacement ribbed piles in a unit gravity model test. Four tests were carried out to replicate the constant rate of penetration (CRP) test in the field. Two lengths corresponding to short and long piles for each of plain and ribbed piles were employed. Compacted Kaolin S300 type was employed as the model soil. The failure load of the piles was determined using six different methods. An increased capacity of 32% and 20% was obtained in the short and long ribbed piles, respectively. Also, it was observed that the closer the distance between the ribs, the higher the capacity produced for equal number of ribs. The ribbed piles gave higher capacities through the increase in their shaft capacity which is associated with the presence of ribs along their lengths. An increase in the axial capacity of displacement piles can be attained by modifying the profile of the pile shaft through the use of ribs

Utilisation of transparent synthetic soil surrogates in geotechnical physical models: a review

Efforts to obtain non-intrusive measurement of deformations and spatial flow within soil mass prior to the advent of transparent soils have perceptible limitations. The transparent soil is a two-phase medium composed of both the synthetic aggregate and fluid components of identical refractive indices aiming at attaining transparency of the resulting soil. The transparency facilitates real life visualisation of soil continuum in physical models. When applied in conjunction with advanced photogrammetry and image processing techniques, transparent soils enable the quantification of the spatial deformation, displacement and multi-phase flow in physical model tests. Transparent synthetic soils have been successfully employed in geotechnical model tests as soil surrogates based on the testing results of their geotechnical properties which replicate those of natural soils. This paper presents a review on transparent synthetic soils and their numerous applications in geotechnical physical models. The properties of the aggregate materials are outlined and the features of the various transparent clays and sands available in the literature are described. The merits of transparent soil are highlighted and the need to amplify its application in geotechnical physical model researches is emphasised. This paper will serve as a concise compendium on the subject of transparent soils for future researchers in this field

Assessment of disturbance impact of hydraulic jacked-in pile penetration in artificial clayey soil

The jacked-in pile method provides a substitute procedure that permits the installation of pre-formed piles with negligible vibration in a noiseless manner, thereby reducing noise impacts in marine and urban environments. This research was carried out by using a small-scale physical modelling approach to examine the movement of soil during pile installation. The model soil was formulated from a mix of amorphous silica and mineral oils; the resulting mixture was subjected to consolidation in a transparent chamber. The model pile was driven vertically down the mid-point of the soil model at different vertical speeds using a strain control device. The array of soil displacement dispersal was obtained by utilising the close-range photogrammetry and particle image velocimetry techniques. The deformation of soil during pile installation was found to decrease with progressive increase of the penetration rate. This result can be employed in the assessment of the disturbance effects of pile installation on underground services and archaeological relics beneath the ground in both urban and marine environments

Enhancement of soft soil behaviour by using floating bottom ash columns

The current disposition worldwide is for sustainable construction, and the application of by-products is one of the ways to achieve it. In this research, bottom ash was used as a substitute material in a granular column to decrease settlement and enhance the bearing capacity of soft soil. Bottom ash is a derivate of the coal burning process, it has similar engineering properties to sand and fine gravel. A set of reduced scale physical modelling tests were performed on floating bottom ash columns to assess the improvement in the bearing capacity of the composite ground. The results clearly showed that the bearing capacity of the model soil was greatly improved with the installation of bottom ash column sand. There was an obvious enhancement of the load capacity of the granular columns when they were encased. The usage of bottom ash instead of aggregate or sand for granular columns will reduce the project cost and it aligns with the goal of sustainable construction development

Settlement evaluation of soft soil improved by floating soil cement column

This study focuses on the settlement of soft soil improved by floating soil cement columns in a small-scale physical test. The effect of area improvement ratio (ap) and column height (Hc) on the improved ground under design load (Wd) were investigated via small-scale physical modeling tests. The area improvement ratios of 21.7, 32.5, and 43.4% and column heights of 50 and 100 mm were examined. The models were instrumented to measure displacements and soil pressures. Two loading scenarios were applied on treated and untreated soils. The first series was conducted under strain controlled mode to identify the failure mechanism. The second series was conducted under design load to evaluate the stress distribution, settlement, and failure pattern. The settlements also were measured using particle image velocimetry (PIV) technique. The PIV showed that the final settlement of the improved ground decreases as the area improvement ratio (ap) increases and the column height (Hc) increases. For controlling the distribution of stresses, an intermediate range of area improvement ratio is recommended. In addition, this study proved that the PIV technique is an effective optical method to simulate ground deformations at the lowest strain without performing a full-scale test

Predicting the effective depth of soil stabilization for marine clay treated by biomass silica

Reclamation and development towards the oceanic area had become a trend of modern days, where the marine soil need to be treated prior construction. The increase in unconfined compressive strength of marine clay treated by Biomass Silica, ‘SH-85’ has been demonstrated by several investigations. This paper studies the stress-strain behavior of marine clay treated with 12% of SH-85 with different curing periods and confining pressures. The results show that the strength parameters of the stabilized soil are greatly improved during the early stage of the curing period under higher confining pressures. In addition, the XRD analysis and microstructure study confirm the appearance of a new reflection peak at 29° in the treated soils indicating the formation of Calcium Silicate Hydrate (CSH). The curing period of 7 days at a confining pressure of 400 kPa was found to be an optimum combination for in situ stabilization. The effective stabilization depth predicted at each location can be defined as the depth ensuing the mentioned confining pressure. The approach of this research can be applied in construction activities associated with marine clay to help engineers in risk assessment, feasibility study and planning of the development