R. J. Jardine

Stresses Developed around Displacement Piles Penetration in Sand

Establishing the stress conditions developed around displacement piles in sands is crucial to improving the understanding and modeling of their behavior. High-quality experiments and theoretical analyses are providing new insights into the effects of penetration on stress conditions. This paper synthesizes the findings from three independent experimental studies on normally consolidated silica sands and a trio of numerical analyses that tackle the problem from different perspectives. The significant degrees of uncertainty in the measurements and predictions are recognized and significant differences between data sets are discussed and largely resolved. Applying a consistent normalized interpretive framework leads to clear common trends regarding how installation affects the stress regime. While the main emphasis is placed on the radial effective stresses developed around pile shafts, the circumferential and vertical stress states are also considered.

Field testing of large diameter piles under lateral loading for offshore wind applications

The nature-inspired concept of self-healing materials in construction is relatively new and has recently attracted significant attention as this could bring about substantial savings in maintenance costs as well as enhance the durability and serviceability and improve the safety of our structures and infrastructure. Much of the research and applications to date has focused on concrete, for structural applications, and on asphalt, with significant advances being made. However, to date no attention has been given to the incorporation of self-healing concepts in geotechnical and geo-environmental applications. This includes the use of concrete and other stabilising agents in foundations and other geotechnical structures, grouts, grouted soil systems, soil-cement systems and slurry walls for ground improvement and land remediation applications. The recently established Materials for Life (M4L) project funded by EPSRC has initiated research activities in the UK focussing on those applications. The project involves the development and integration of the use of microcapsules, biological agents, shape memory polymers and vascular networks as healing systems. The authors are exploring development of self-healing systems using mineral admixtures, microencapsulation and bio-cementation applications. The paper presents an overview of those initiatives to date and potential applications and presents some relevant preliminary results.By contrast to studies in petroleum geology and, despite their world-wide occurrence, geotechnical studies of ancient fluvial sediments are rare. This paper introduces the main characteristics of these sediments by reference to a classic UK example. Attention is then drawn to a number of major overseas examples where, although the principal features can be recognised, large differences arise as a result of factors such as the tectonic setting, the volume and mineralogy of the source material and the climate at the time the sediments were deposited. The first, over-riding problem for their engineering evaluation comes during the site investigation phase with the difficulty of deducing the geological structure and distribution of the widely varying lithologies.ABSTRACT: nEarthen construction and soil-based construction materials (SBCMs) are expanding areas of interest worldwide. They offer nthe potential for low carbon and embodied energy, sustainability through recycling and an alternative to high energy materials such as fired nmasonry. The materials that are generally used in earthen construction can be identified as manufactured unsaturated soils. Until recently, nhowever, these materials have rarely been studied using a geotechnical approach, and there is a general lack of recognition of the key nmechanisms at work mechanically and hydraulically. In this paper we review geotechnical aspects of soil-based construction materials examining nthe effects of suction and environmental conditions, and demonstrating behaviour in shear, compression and fracture. We cover nmaterials which are both unstabilised, where the primary source of strength is suction, and materials which are stabilised with cement, lime nor fibres. The review is backed up by experimental results from laboratory and field testing undertaken over a number of years at Durham nand UWA. n nRESUME: nConstruction en terre (en utilisant des materiaux de construction a base de sol - ») est une extension du domaine de linteret ndans le monde entier en raison de faibles emissions de carbone potentiel et lenergie intrinseque , et la durabilite a travers le recyclage , et il nest possible d utiliser beaucoup plus pour remplacer les materiaux de haute energie tels que la maconnerie tire . Les materiaux qui sont generalement nutilises dans la construction en terre peuvent etre identifies comme les sols non satures fabriques . Jusqua recemment, toutefois n, ces materiaux ont rarement ete etudie en utilisant une approche geotechnique , et il ya un manque general de reconnaissance des principaux nmecanismes a loeuvre mecaniquement et hydrauliquement . Dans cet article, nous examinons les aspects geotechniques des materiaux nde construction a base de sol - examinant les effets de la succion et des conditions environnementales , et le comportement en cisaillement ndemontrer , la compression et de fracture. Nous traitons des materiaux qui sont a la fois stabilisees , ou la premiere source de force daspiration nest , et les materiaux qui sont stabilises avec du ciment , de la chaux ou de fibres . La revue est soutenue par experimentales re- sultats nde tests en laboratoire et sur le terrain entrepris depuis un certain nombre dannees a Durham et lUWA .Strain accumulation in granular soils due to dynamic loading is investigated through long term cyclic triaxial tests and cyclic triaxial tests according to ASTM D 3999-91. Soil parameters, test equipment and loading conditions have a significant influence on strain accumulation, therefore a parameterization of the silica sand and a description of the cyclic triaxial test device are explained. Cyclic triaxial tests are performed and test results are presented illustrating the evolution of Young’s modulus during long term cyclic loading. The influence of the width of the stress-strain loop and the initial void ratio on strain accumulation is investigated and validated with existing accumulation models. The usefulness of Miner’s rule on sand subjected to cyclic loading is demonstrated by two tests with different packages of loading cycles.

Assessment of standard research sand for laboratory testing

tandard soils are used worldwide as reference materials with which new model or single element experiments may be performed, assessed and calibrated. The testing databases associated with these are valuable resources that are particularly important when developing new procedures. However, the finite extent and variability of all natural deposits creates the possibility that standard soils may vary, or become unavailable, over time. The Ham River Sand (HRS), from the Thames Valley in the UK has been researched continuously and comprehensively in a series of studies since the 1940s, leading to a large database that includes recent advanced hollow cylinder, stress path triaxial and dynamic testing. Fresh samples are now unavailable and the paper describes a study of alternative sampling sources within the Thames Valley. Microscopic visual inspections, index measurements, direct shear, high pressure oedometer, bender element and stress path triaxial test data are presented in the paper, focusing on the natural variability and the ranges seen in material test response. A replacement for the original HRS is identified, so allowing those developing new tests the possibility of conducting experiments on material that is compatible with the existing HRS database. Reference is also made to advances in bender element testing achieved as part of the study.

PISA: New Design Methods for Offshore Wind Turbine Monopiles

Improved design of laterally loaded monopiles is central to the development of current and future generation offshore wind farms. Previously established design methods have demonstrable shortcomings requiring new ideas and approaches to be developed, specific for the offshore wind turbine sector. The Pile Soil Analysis (PISA) Project, established in 2013, addresses this problem through a range of theoretical studies, numerical analysis and medium scale field testing. The project completed in 2016; this paper summarises the principal findings, illustrated through examples incorporating the Cowden stiff clay profile, which represents one of the two soil profiles targeted in the study. The implications for design are discussed.

Field Behavior of Driven Prestressed High-Strength Concrete Piles in Sandy Soils

AbstractDriven piles are used widely both offshore and onshore. However, accurate axial capacity and load-displacement prediction is difficult at sand-dominated sites, and offshore practice is moving towards cone penetration test (CPT) based design methods developed from instrumented pile research and database studies. However, onshore use of these methods remains limited; there is a paucity of high quality case histories to assess their potential benefits clearly, and application in layered profiles may be uncertain. This paper presents new tests on prestressed concrete (PHC) pipe piles driven in sands for a major new Yangtze River bridge project in China, assessing the performance of the ‘new CPT’ and conventional capacity approaches, considering the influence of weak sublayers on base resistance and noting the marked changes in shaft capacity that apply over time.

Closure to “Stresses Developed around Displacement Piles Penetration in Sand” by Z. X. Yang, R. J. Jardine, B. T. Zhu, and S. Rimoy

Z. X. Yang; R. J. Jardine; B. T. Zhu; and S. Rimoy Associate Professor, Key Laboratory of Soft Soils and Geoenvironmental Engineering of Ministry of Education, Research Center of Coastal and Urban Geotechnical Engineering, Dept. of Civil Engineering, Zhejiang Univ., Hangzhou 310058, China (corresponding author). E-mail: zxyang@ zju.edu.cn Professor, Dept. of Civil and Environmental Engineering, Imperial College, London SW7 2AZ, U.K. E-mail: r.jardine@imperial.ac.uk Principal Engineer, NOMAConsulting Pty Ltd., 10 Sackville Close, Brisbane, QLD 4018, Australia. E-mail: bitang.zhu@noma-consulting.com Lecturer, Dept. of Transportation and Geotechnical Engineering, Univ. of Dar es Salaam, Dar es Salaam, Tanzania. E-mail: rimoy@udsm.ac.tz

The ICP Design Method and Application to a North Sea Offshore Wind Farm

This paper outlines the Imperial College Pile (ICP) approach for developing reliable predictions for the axial capacity of driven piles. The ICPs advantages over traditional design methods have led to widespread use in offshore oil and gas developments. The methods are now playing a critical role in major Northern European offshore wind projects. Hundreds of large steel tubular piles are being driven in the North and Baltic seas and improving design efficiency is crucial to the industrys economic success. This paper provides an overview of the development of the ICP design methods and summarizes their key features, together with experience-based guidance on their application. Their application is illustrated by reference to the North Sea Borkum West II wind farm, where 40 turbines have been installed on steel tripods founded on large diameter steel piles driven in very dense sands. The paper reports how the significant effects of axial and lateral cyclic loading were addressed for Borkum West II through the ICP design methodology.