Mark Randolph

Bio: Mark Randolph is an academic researcher from University of Western Australia. The author has contributed to research in topics: Pile & Bearing capacity. The author has an hindex of 79, co-authored 561 publications receiving 21349 citations. Previous affiliations of Mark Randolph include Curtin University & Australian Research Council.

Analysis of deformation of vertically loaded piles

Abstract: An approximate closed-form solution has been obtained to the problem of a vertically loaded pile in a linear elastic soil. This solution has been derived by uncoupling the load-transfer for the pile into separate shaft and base components. Throughout the development of the analysis, well-proven numerical techniques have been used to verify that the assumptions made are reasonable. The final form of the solution gives the load-settlement ratio of the pile in terms of the pile geometry and stiffness and soil stiffness. The analysis has been used to back-analyze pile tests, enabling immediate estimates of the soil stiffness profile to be made from the measured load-settlement curve of the pile. The application of the method to pile design is demonstrated—design curves being sketched for piles of different geometries in two typical soft clay deposits.

The response of flexible piles to lateral loading

Abstract: The majority of piles encountered in practice may be regarded as ‘flexible’ under lateral loading. That is, the induced deformations and bending moments are confined to the upper part of the pile and the overall length of the pile does not significantly affect the response of the pile. The results of a parametric study, conducted using the finite element method and treating the soil as an elastic continuum with a linearly varying soil modulus, are presented as simple algebraic expressions. These expressions are similar in form to those which arise from a Winkler idealization of the soil, enabling immediate estimates to be made of: the active length of the pile; the ground level deformations; and the maximum bending moment down the pile. In addition, expressions are presented quantifying the effect of interaction between neighbouring piles. from which the behaviour of groups of piles subjected to lateral loading may be deduced. Application of the solutions is demonstrated by the analysis of lateral loading...

The limiting pressure on a circular pile loaded laterally in cohesive soil

Abstract: In the analysis of the undrained loading of laterally loaded piles an important quantity is the ultimate lateral resistance at depth to purely horizontal movement. If the soil is modelled as a perfectly plastic cohesive material then the calculation of this quantity reduces to a plane strain problem in plasticity theory, in which the load is calculated on a long cylinder which moves laterally through an infinite medium. An exact calculation of the load on such a cylinder is presented. If this load is non-dimensionalized with respect to the soil strength and the diameter of the pile, it is found that the load factor varies between for a perfectly smooth pile and for a perfectly rough pile. This result is discussed in the context of previous calculations for the lateral load capacity of piles and is compared with approximate calculations using cavity expansion theory and a wedge failure near the soil surface. La resistance laterale limite en profondeur au seul mouvement horizontal represente un parametre im...

Science and empiricism in pile foundation design

Abstract: Scientific approaches to pile design have advanced enormously in recent decades and yet, still, the most fundamental aspect of pile design—that of estimating the axial capacity—relies heavily upon empirical correlations. Improvements have been made in identifying the processes that occur within the critical zone of soil immediately surrounding the pile, but quantification of the changes in stress and fabric is not straightforward. This paper addresses the degree of confidence we can now place (a) on the conceptual and analytical frameworks for estimating pile capacity, and (b) on the quantitative parameters required to achieve a design. The discussion is restricted to driven piles in clays and siliceous sands, with particular attention given to extrapolating from design approaches derived for closed-ended piles of relatively small diameter to the large-diameter open-ended piles that are used routinely in the offshore industry. From a practical viewpoint, we need design approaches that minimise sensitivity...

Catalogue of scaling laws and similitude questions in geotechnical centrifuge modelling

Abstract: Some forty years ago, when geotechnical centrifuge modelling had been rediscovered and was being developed once more after the early work of Phillips (1869), only a few studies were devoted to the questions and concerns about scaling laws and similitude conditions. During the first decades, it was relatively easy for researchers to keep themselves informed about the main outcomes of these studies and to take them into account when designing new centrifuge model tests. This is obviously not true today following the welcome growth in terms of the large number of centrifuge facilities now in operation around the world. It is increasingly difficult, but yet absolutely essential, to know about the relevant developments concerning studies into the scaling laws and, furthermore, into the limits of the domains of the use of centrifuge modelling. On the other hand, new media offers a significant opportunity to provide this resource to the physical modelling community. New topics are investigated by many researcher...

Soil Behaviour and Critical State Soil Mechanics

Abstract: Soils can rarely be described as ideally elastic or perfectly plastic and yet simple elastic and plastic models form the basis for the most traditional geotechnical engineering calculations. With the advent of cheap powerful computers the possibility of performing analyses based on more realistic models has become widely available. One of the aims of this book is to describe the basic ingredients of a family of simple elastic-plastic models of soil behaviour and to demonstrate how such models can be used in numerical analyses. Such numerical analyses are often regarded as mysterious black boxes but a proper appreciation of their worth requires an understanding of the numerical models on which they are based. Though the models on which this book concentrates are simple, understanding of these will indicate the ways in which more sophisticated models will perform.

Microbially Induced Cementation to Control Sand Response to Undrained Shear

Abstract: Current methods to improve the engineering properties of sands are diverse with respect to methodology, treatment uniformity, cost, environmental impact, site accessibility requirements, etc. All of these methods have benefits and drawbacks, and there continues to be a need to explore new possibilities of soil improvement, particularly as suitable land for development becomes more scarce. This paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand. Microbially induced calcite precipitation (MICP) was achieved using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits. The microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source. Subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix. The results of both MICP- and ...

Bio-mediated soil improvement

Abstract: New, exciting opportunities for utilizing biological processes to modify the engineering properties of the subsurface (e.g. strength, stiffness, permeability) have recently emerged. Enabled by interdisciplinary research at the confluence of microbiology, geochemistry, and civil engineering, this new field has the potential to meet society's ever-expanding needs for innovative treatment processes that improve soil supporting new and existing infrastructure. This paper first presents an overview of bio-mediated improvement systems, identifying the primary components and interplay between different disciplines. Geometric compatibility between soil and microbes that restricts the utility of different systems is identified. Focus is then narrowed to a specific system, namely bio-mediated calcite precipitation of sands. Following an overview of the process, alternative biological processes for inducing calcite precipitation are identified and various microscopy techniques are used to assess how the pore space volume is altered by calcite precipitation, the calcite precipitation is distributed spatially within the pore space, and the precipitated calcite degrades during loading. Non-destructive geophysical process monitoring techniques are described and their utility explored. Next, the extent to which various soil engineering properties is identified through experimental examples. Potential advantages and envisioned applications of bio-mediated soil improvement are identified. Finally, the primary challenges that lie ahead, namely optimization and upscaling of the processes and the education/training of researchers/practitioners are briefly discussed.

Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil

Abstract: An experimental program was undertaken to investigate the effects of discrete short polypropylene fiber (PP-fiber) on the strength and mechanical behavior of uncemented and cemented clayey soil. In the present investigation, 12 groups of soil samples were prepared at three different percentages of PP-fiber content (i.e. 0.05%, 0.15% and 0.25% by weight of soil) and two different percentages of cement content (i.e. 5% and 8% by weight of soil), and unconfined compression and direct shear tests were carried out after 7-, 14- and 28-day curing periods. The test results indicated that the inclusion of fiber reinforcement within uncemented and cemented soil caused an increase in the unconfined compressive strength (UCS), shear strength and axial strain at failure, decreased the stiffness and the loss of post-peak strength, and changed the cemented soil's brittle behavior to a more ductile one. The interactions at the interface between fiber surface and soil matrix were analyzed by using scanning electron microscopy (SEM). It is found that the bond strength and friction at the interface seem to be the dominant mechanism controlling the reinforcement benefit. The behavior at the interface in fiber-reinforced uncemented soil was different from that in fiber-reinforced cemented soil. The micromechanical properties of fiber/matrix interface were influenced by several factors, e.g. binding materials in soil, normal stress around the fiber body, effective contact area of the interface and fiber surface roughness, etc.

Soil Mechanics and Foundations

Abstract: Introduction to Soil Mechanics and Foundations. Physical Characteristics of Soils and Soil Investigations. Stresses, Strains and Elastic Deformations of Soils. One--Dimensional Consolidation Settlement of Fine--Grained Soils. Shear Strength of Soils. A Critical State Model to Interpret Soil Behavior. Bearing of Capacity of Soils and Settlement of Shallow Foundations. Pile Foundations. Two--Dimensional Flow of Water Through Soils. Stability of Earth Retaining Structures. Slope Stability. Appendices. Answers to Selected Problems. References. Index.