The University of Aberdeen has conducted research into ground anchorage systems since the early 1980's. During this time, the non-destructive GRANIT system (GRound ANchorage Integrity Testing) has been developed for anchorages in rock. The system is based on observing the dynamic response from anchorages to which an impulse of a known intensity has been applied. This technique has been proven to be a reliable system to assess the integrity of rock anchorages, which is then used as a base to study the integrity of soil anchorages. This research aims to implement a non-destructive testing system at small scale size and full scale stress levels by means of centrifuge modelling at the University of Dundee. Accordingly, centrifuge modelling was undertaken to monitor and assess the dynamic response of soil anchorages installed in dry sand reinforcing a retaining wall in 3x3 anchorage array sets, subject to different post tension levels within different bonding ratios and different inclinations. In order to perform non-destructive testing, an In-flight Robotic Manipulator, previously developed, was used to apply a post tension load followed by an impact load to the anchorage head to obtain the dynamic response of the system. Anchor frequency response signatures were then evaluated in order to validate the consistency of results obtained. The practical importance of this research is that non-destructive testing may be usable to assess the soil anchors integrity to define the relationship between both anchor load and geometrical characteristics with frequency response accomplished using centrifuge modelling. This research presents a further development of the physical model in which additional instrumentation is included in order to obtain load/deflection information of the anchor head, which has been proven crucial for monitoring load on rock anchorage. Additionally, load distributions along scaled model soil anchors are measured and found to reduce gradually within the fixed length, similarly as it was reported for the fixed length of rock anchorages. Furthermore, a lumped parameter model for a single soil anchorage was adapted to investigate the dynamic response under the same physical and geometrical characteristics studied during centrifuge modelling. Mode shapes helped to understand the origin of some of the frequency modes present in the frequency response of the centrifuge results. The results from the numerical and centrifuge models were compared and good agreement was observed. Soil anchorage does not show as much frequency shift as was observed for rock anchorages under different post tension load, suggesting that the bonding strength of the fixed length with the surrounding ground plays an important role on the dynamic response of the system. The accomplishment of the assessment of soil anchorage can not be exclusively judged on its ability to diagnose controlled changes under centrifuge and numerical modelling. Therefore a preliminary phase to assess a soil anchorage under field conditions was carried out deploying the GRANIT system. This research showed that the GRANIT non-destructive testing technique has potential for use in soils, but that the results are not as well defined as in rock, necessitating more careful characterization of each anchorage signature response.

No description available.

The development of a more rational design procedure to predict not only ultimate tieback capacities in cohesive soils, but associated tieback displacements as well, requires a basic understanding of short-term and long-term tieback behavior. In view of the above, a series of full-scale and model tieback tests were conducted on instrumented and non-instrumented straight-shafted, postgrouted, and single-underreamed tiebacks anchored in different cohesive soils. In addition, laboratory shear strength tests were conducted on soil-soil samples and grout-soil samples to allow a better interpretation of field and model results. A better understanding of (1) the load-transfer mechanism of each type of tieback and (2) both time-independent and time-dependent component movements has led to the development of a physical model to describe short-term and long-term tieback behavior in a cohesive soil.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 112-115). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

The thesis falls naturally into four parts. The first constitutes a world-wide survey of the methods used in practice to design prestressed, cement grouted rock anchors. The major topics of overall stability and system geometry, the rock-grout and grout-steel interfaces, and grout and tendon selection, are reviewed in turn. Comparisons between the standard methods of practice, and the findings from theoretical and field studies, reveal important areas of uncertainty and contradiction, particularly with regard to the mechanisms of load transfer from tendon to rock. Part 2 describes the author's full scale test anchor programme, conducted at Withnell, Lancashire, devised to investigate the major problems associated with load transfer which were highlighted in Part 1. Full details are provided of the site and its geology, and the methods of construction, testing, recording and analysis employed. Most emphasis placed on the results obtained from the fifty-seven anchors: these are fully discussed and wherever possible compared with data presented in the review. The third part deals with the long term performance of rock anchor systems. Analogous to Parts 1 and 2, one chapter is devoted to a review of relevant published information, whereas the other chapter details the author's case study of ten production anchors at H.M. Dockyard, Devonport. In Part 4, conclusions on the field test programmes are summarised and indications are given of topics meriting further research.

Current methods for assessing the integrity of ground anchorages during service are primarily restricted to monitoring by load cells or load lift-off testing. Both are expensive and lift-off testing is time consuming and can damage the anchorage construction below the anchor head. Hence, only typically 5-10% of anchorages are monitored in service. As a result, The Institution of Civil Engineers reported that non-destructive test methods for ground anchorages need to be developed as a high priority (ICE, 1992). The Universities o f Aberdeen and Bradford have been conducting research since 1986 to investigate the response o f rock anchorages to dynamic loading arising from blasting operations. Full scale field trials were conducted during the construction of two tunnels in North Wales. An important finding from the research revealed that certain characteristics of the dynamic response of a rock bolt resulting from blasting operations, were similar for different blast sequences. This indicates that the dynamic response o f an anchorage system is dependant on the construction of the anchorage and the characteristics of the co-vibrating rock mass. Consequently, the University of Aberdeen has developed a new non-destructive condition monitoring and integrity assessment system for ground anchorages (GRANIT ™). A range of patent applications have been successful world-wide and the system has been exclusively licensed to AMEC Civil Engineering Limited. The system operates by applying an axial tensile impact load to the free end of an intact anchorage immediately after installation. The resulting vibrational response is monitored by an accelerometer, located at the anchorage head, which produces a datum signature for that anchorage. The condition of the anchorage is then inferred by comparing subsequent response signatures with the datum. A change in the signature indicates that there may be a potential change in the integrity of the anchorage. Artificial Intelligence systems are employed to compare response signatures. As part of the research programme, the author conducted commissioning tests on small scale laboratory test rigs and was responsible for the development of a prototype non-destructive test system, which included a means of applying an impact load and recording the vibrational response. In addition, the author conducted full scale laboratory tests and field trials to investigate the effect of prestress on the dynamic response of ground anchorage systems. As a result, the prototype non-destructive test system has been employed to successfully predict the amount of load within an anchorage installation.

M.Tech. (Civil Engineering) / Recoverable anchor screws are widely used in the construction of massive concrete structures such as dams, channels, tunnels and multi-story buildings to fix temporary cantilever forms. Attempts have been made before to quantify the failure capacities of recoverable anchor screws. However, such tests were conducted and reported on more than 25 years ago and were limited to a small number of tests on concrete strengths not exceeding 20 MPa, whereas most concrete constructions now exceed such strengths. The aim of this dissertation was to review the existing theories on the use of concrete anchors in practice and to apply the appropriate theories to recoverable anchor screws. In doing so, the overall shear strength of these screws was determined by considering existing theoretical standards and norms, and by testing the tensile capacity in the laboratory. The failure behaviour of recoverable anchor screws in various concrete strengths and construction applications is reviewed and is discussed based on both theory and the laboratory results obtained. The empirical formulas derived for the practical use of recoverable anchor screws are presented in standard form. These formulas provide an easy reference for engineering professionals in practice to determine the load capacity of recoverable anchor screws in various concrete strengths and construction applications. In conclusion, the required future research on recoverable anchor screws is presented.

<p>A unified and consistent design procedure is proposed for column base anchorages loaded in shear and tension. A literature review of previous work was done to identify discrepancies. A design procedure for anchorages loaded in shear, tension and combined shear and tension was developed which attempted to coordinate c;lnd resolve the discrepancies in previous work. A design methodology utilizing shear lugs was developed. The overall design procedure is for column bases loaded in shear and tension and uses two design methods:</p> <p>Method 1: Headed anchor bolts are used to resist both shear and tension loads.</p> <p> Method 2: A shear lug welded to the bottom of the base plate resists shear loads and the headed anchor bolts resist only tension loads.</p> <p>The proposed design method differs form the design method used by Shipp and Haninger (Reference 23) as follows:</p> <p> 1. The proposed procedure incorporates both shear and tension design stress based on the ultimate strength of the anchor bolts times a reduction factor.</p> <p> 2. Separate capacity reduction factors are introduced for shear and tension.</p> <p> 3. The use of shear lugs is incorporated in the proposed design.</p> <p> 4. The incorrect use of the "shear-friction" concept is noted and not used in the design.</p> <p> 5. The safety factor for the required embedment depth is applied to the projected area of the failure cone not the embedment depth of the bolt.</p> <p> Several design examples are presented using the two methods. A computer program (using Microsoft QuickBasic 4.0) has also been developed using the proposed design procedure.</p> / Master of Engineering

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 86-88). Also available on the World Wide Web.