The bearing capacity and settlement of gravel piles in clay

Includes bibliography.The writer has been interested in the subject of gravel piles for a number of years and has been suprised at the lack of rational design methods. When the piles are inserted in sand their purpose is mainly one of densification and their effectiveness is usually measured by a Dutch Cone Penetrometer with an increase in cone resistance as the sand is densified. For clays the above method is clearly not applicable and a conservative approach has generally been adopted with regard to the pile length and spacing. There appears to be only one paper which is often quoted as a design method (Hughes and Withers 1974) and at least one contractor used this method as a basis for design (Cementation •1977). The State of the Art was advanced in .1976 when a symposium on ground treatment was held. Again the basic design philosophy adopted was that of Hughes and Withers, and numerous case histories appeared to back up the design approach. The writer was therefore interested in formulating a new design method which could act as a check on the traditional method. Also, it was felt that an understanding of the stress-strain behaviour of the pile was needed to fully appreciate the implications of any design method. However, prior to the submission of the thesis the writer was made aware of work undertaken in Australia (Balaam and Booker 1979) which used elastic methods to establish the stress-strain behaviour of a pile. This approach is valuable as the sensitivity of design to various parameter changes can quickly be checked by reference to the numerous graphs presented. As this work is little known the relevant graphs have been reproduced in Ch. 8 of this thesis. It is intended that this thesis will act as a concise guide to column behaviour and design, as well as to the uses to which they may be put. Also, a new design method is proposed which. has been developed from a basic understanding of the stress-strain behaviour of a pile. The sequential approach used in developing this thesis is outlined in the next section

Geotechnical state-of-the-art in Guatemala -- Ground stabilization

History provides an understanding of the present and in a way, a guide for the future. The state-of-the-art is often referred to as a snapshot of the most significant works and contributions made in a field of study; In this case the focus is on Guatemalan geotechnical engineering. This study presents a comprehensive description of the different events that impulse geotechnical engineering in Guatemala. As part of the description of the state-of-the-practice an investigation of the different human (engineers/contractors) and physical resources (laboratories/field equipment) and their capabilities are presented. An overview of the civil engineering programs is presented. Then, the advances in the graduate program in geotechnical engineering are discussed. Select comprehensive case studies are presented. Project selection was based on relevance and project\u27s interest for geotechnical engineers. Privileged data and information, such as design, construction, and performance data are presented, giving a full range of point of views of the selected projects. Selected projects include topics such as slope stabilization, ground improvement, liquefaction, deep excavations, dams, grouting and foundations. A perspective on the quality of the solutions adopted in tropical and volcanic areas is discussed. For each case study, a review of the degree at which geotechnical engineering processes were followed: subsurface investigation, analytical or computational tools, empirical relationships, field testing, and/or measurement of performance (monitoring behavior). The study concludes by identifying the lessons learned; areas of improvement and recommendations in the different fields of education, resources, and practice --Abstract, page iii

Geotechnical Challenges in Highway Engineering in Twenty First Century: Lessons from the Past Experiences and New Technologies

The Transportation Authorities and Highway Engineers around the world are facing different types of challenges today than their counterparts in the nineteenth and twentieth centuries. These challenges include developing new highways and bridges as well as retrofitting of existing roads and bridges deteriorated due to aging or increased vehicle loading. Frequencies of deterioration of existing roads and imminent bridge failures forced many Highway Authorities to evaluate the existing roads and bridges and prioritize their retrofitting to comply with current specifications and future conditions. The new challenges of today include, but not limited to: a) Construction over poor foundation materials such as organic soils, old landfills, expansive and collapsing soils and non-availability of alternative routes; b) Right-of-way restrictions including construction in urban areas and proximity of existing structures; c) Dealing with environmental concerns that were not considered critical in the past and complying with stricter environmental and safety regulations.; d) Utilization of certain native on-site materials (considered problematic such as shale) in back fills and embankments; e) Higher vehicle loading as well as increase in size and number of vehicles; f) Expectations of the road users for better driving conditions, safety improvements and riding quality. These challenges can be overcome by applying innovative ideas and using modern technology during planning, design and construction stages of highway development. This paper identifies some of the new challenges of today based on past history and presents various tools to meet these challenges. With better and faster methods of analysis, use of new construction materials (such as low density fill materials, geo-synthetics, geo-foam, tensors), utilization of new procedures (such as soil stabilization, reinforced earth, soil nailing ) and implementation of effective planning, execution and quality control, these challenges can be overcome in an efficient and cost effective manner. This paper also identifies various current geotechnical practices, which may be considered inadequate for modern-day highway design and construction, but have not been updated for decades. In conclusion, recommendations for revisions to inadequate geotechnical practices are presented in this paper in order to provide safe and sound design and construction guidelines from geotechnical viewpoint

Assessment of rapid impact compaction for transportation infrastructure applications

Despite being identified as a geoconstruction technology applicable to transportation infrastructure applications, rapid impact compaction (RIC) has yet to be utilized on a transportation infrastructure project. Both technical and nontechnical obstacles, such as a lack of performance data, have impeded the introduction of RIC into the transportation sector. Each obstacle requires mitigation before RIC can be incorporated into the transportation sector. The goal of this research was to evaluate RIC for civil engineering applications in the transportation sector and mitigate the obstacles impeding the use of RIC within the transportation sector. The objectives that were sought to achieve this goal include expanding the RIC knowledge base; presenting a detailed case history of a commercial RIC project; and assessing the applicability of RIC\u27s design, QC/QA, and specification procedures to transportation infrastructure projects. RIC is a well established technique within the commercial sector. An ample amount of commercial case histories and data pertaining to RIC performance, induced vibrations, and cost are currently in existence. The current procedures for design, QC/QA, and specification within the commercial sector will require improvement before application to transportation infrastructure projects. This research has addressed each of the obstacles preventing use of RIC within the transportation sector and has either partially or fully mitigated each obstacle. Additional future strategies for partially mitigated obstacles have been proposed. With fewer obstacles and a greater knowledge base, transportation agencies will have greater confidence in employing RIC for transportation projects

Ground Improvement by Deep Vibratory Methods

Vibro compaction and vibro stone columns are the two dynamic methods of soil improvement most commonly used worldwide. These methods have been developed over almost eighty years and are now of unrivalled importance as modern foundation measures. Vibro compaction works on granular soils by densification, and vibro stone columns are used to displace and reinforce fine-grained and cohesive soils by introducing inert material. This second edition includes also a chapter on vibro concrete columns constructed with almost identical depth vibrators. These small diameter concrete piles are increasingly used as ground improvement methods for moderately loaded large spread foundations, although the original soil characteristics are only marginally improved. This practical guide for professional geotechnical engineers and graduate students systematically covers the theoretical basis and design principles behind the methods, the equipment used during their execution, and state of the art procedures for quality assurance and data acquisition. All the chapters are updated in line with recent developments and improvements in the methods and equipment. Fresh case studies from around the world illustrate the wide range of possible applications. The book concludes with variations to methods, evaluates the economic and environmental benefits of the methods, and gives contractual guidance

Ground Improvement by Deep Vibratory Methods

Vibro compaction and vibro stone columns are the two dynamic methods of soil improvement most commonly used worldwide. These methods have been developed over almost eighty years and are now of unrivalled importance as modern foundation measures. Vibro compaction works on granular soils by densification, and vibro stone columns are used to displace and reinforce fine-grained and cohesive soils by introducing inert material. This second edition includes also a chapter on vibro concrete columns constructed with almost identical depth vibrators. These small diameter concrete piles are increasingly used as ground improvement methods for moderately loaded large spread foundations, although the original soil characteristics are only marginally improved. This practical guide for professional geotechnical engineers and graduate students systematically covers the theoretical basis and design principles behind the methods, the equipment used during their execution, and state of the art procedures for quality assurance and data acquisition. All the chapters are updated in line with recent developments and improvements in the methods and equipment. Fresh case studies from around the world illustrate the wide range of possible applications. The book concludes with variations to methods, evaluates the economic and environmental benefits of the methods, and gives contractual guidance

Evaluation of the electrical density gauge for in-situ moisture and density determination

Densification of soil during construction of earth structures is achieved through the process of compaction by application of mechanical energy to obtain the required engineering properties of the soil for a particular project such as hydraulic conductivity, soil strength and compressibility. These properties are dependent on attainment of high compaction densities normally achieved at specific moisture contents for a given compactive effort. The optimum moisture content and maximum dry density for a particular soil is determined by means of Proctor tests in the laboratory. A relative compaction index is then used to correlate the laboratory values with the field compaction values obtained using in-situ tests. The Sand Cone (SC) and Nuclear Density Gauge (NDG) are the common field tests used to the dry density and moisture content of the soil for purposes of quality control of the compaction process. The sand cone is a laborious test that involves excavation of part of the compacted layer and requires a 24-hour waiting period to obtain the moisture content of the soil through the laboratory oven method. The NDG on the other hand is less laborious, however it uses a radioactive source that is a potential health hazard and therefore requires strict handling, storage and maintenance of the equipment to maintain safety standards. The Electrical Density Gauge (EDG) is an alternative in-situ test that is quicker, safer and easier to maintain since it uses electric current to measure the compaction characteristics of the soil. The objective of the study was to determine the repeatability, accuracy and applicability of the EDG on South African soils by comparing its measurements for dry density and moisture content in the laboratory and in the field to the results from the sand cone and oven method. In the laboratory, a clean sand and a clayey sand were tested at the optimum moisture content and at ± 3% of the optimum moisture content. The soils were compacted to 200 mm using the RT74 rammer and the compaction values first tested using the EDG then followed by the sand cone test at the centre of the EDG test spot. The moisture content of the excavated sample from the sand cone test was determined using the oven method. For the field tests, the compaction characteristics of a sandy gravel and three uniformly graded sands were tested in-situ using the EDG followed by the sand cone test. Overall, the EDG measurements were repeatable based on test-retest comparison of the paired measurements. EDG results for moisture content were consistent with the values obtained from the laboratory oven method especially in the uniformly graded sands. However, the density measurements differed from the results of the sand cone test, which was considered the reference test for determination of field soil density. It is recommended that the EDG calibration relationship for bulk density be revised in order to improve the accuracy of the density measurements

Physical modelling of group behaviour of stone column foundations

Abstract available: p.3