Helical Pile Installation Torque and Capacity Correlations

Large diameter helical piles are being utilized increasingly to support large compressive and tensile loads. Both the magnitude of the required installation torque and the pile capacity can be directly attributed to the soil shearing resistance developed over the embedded area of the pile including the shaft and helical plates. Hence, the pile capacity can be correlated to the installation torque. Such correlations are widely used in helical pile industry as a means for quality control/quality assurance. However, the reliability of capacity-torque correlations for predicting the large diameter helical piles is adversely affected by the inaccurate measurement of the installation torque employing hydraulic pressure torque indicators. In the current study, a torque pin was fabricated using strain gauges methodology to facilitate accurate measurement of installation torque. A total of 17 piles, including seven fully instrumented, were installed while monitoring the installation torque continuously with depth using the fabricated device. The results of installation torque monitoring were demonstrated to be accurate and repeatable. In addition, six compressive and four tensile axial load tests were conducted on the test piles. The load test results were analyzed to determine the interpreted ultimate capacity of the test piles. The results demonstrated that the ultimate capacity of large diameter helical piles can be determined from the pile load tests data employing the interpreted failure criteria proposed by Elkasabgy and El Naggar (2015) and Fuller & Hoy (1970).The measured installation torque and the corresponding ultimate capacity values were used to define torque-to-capacity correlation based on embedded pile area, which is suitable for large diameter piles with single and double helices. Furthermore, the results from the seven test piles that were instrumented with strain gauges provided a description of the load transfer mechanism at various levels of axial loading. It was found that significant settlement may be required to mobilize the bearing resistance provided by the lead helix for both compressive and tensile loading conditions. Finally, the rear helix provides significant capacity contribution under compression loading but little contribution under tensile loading

Effective stress analysis and set-up for shaft capacity of piles in clay

ABSTRACT A case history of repeated dynamic and static loading tests in Alberta on two pipe piles during dissipation of driving-induced pore pressures is presented together with three reanalyzed published case histories involving similar records. The four case histories demonstrate that, for each case, the same effective-stress proportionality coefficients, beta-coefficients, fit the capacities at different degrees of dissipation of excess pore pressures. For two of the test sites, the beta-coefficients back-calculated from the tests differed considerable from the values determined from the soil plasticity relation, while for two, the agreement is good. For one case, the backcalculated shaft resistance agreed well with the values of vane shear strength, while a less good agreement was found for the other tests. Neither case showed good agreement was found for methods combining undrained shear strength and effective overburden stress. Capacity calculations for two cases employing methods based on CPT soundings gave excellent agreement with one test and a poor agreement with the other. The increase of capacity due to aging after dissipation of excess pore pressures did not agree with cited recommendation for calculations of aging effect

Using shared-data localization to reduce the cost of inspector-execution in unified-parallel-C programs

Programs written in the Unified Parallel C (UPC) language can access any location of the entire local and remote address space via read/write operations. However, UPC programs that contain fine-grained shared accesses can exhibit performance degradation. One solution is to use the inspector-executor technique to coalesce fine-grained shared accesses to larger remote access operations. A straightforward implementation of the inspector executor transformation results in excessive instrumentation that hinders performance.; This paper addresses this issue and introduces various techniques that aim at reducing the generated instrumentation code: a shared-data localization transformation based on Constant-Stride Linear Memory Descriptors (CSLMADs) [S. Aarseth, Gravitational N-Body Simulations: Tools and Algorithms, Cambridge Monographs on Mathematical Physics, Cambridge University Press, 2003.], the inlining of data locality checks and the usage of an index vector to aggregate the data. Finally, the paper introduces a lightweight loop code motion transformation to privatize shared scalars that were propagated through the loop body.; A performance evaluation, using up to 2048 cores of a POWER 775, explores the impact of each optimization and characterizes the overheads of UPC programs. It also shows that the presented optimizations increase performance of UPC programs up to 1.8 x their UPC hand-optimized counterpart for applications with regular accesses and up to 6.3 x for applications with irregular accesses.Peer ReviewedPostprint (author's final draft

Volunteerism in community policing : A case study in Nonthaburi Province, Thailand

The purpose of this study is to identify the principal determinants associated with motivational factors in becoming and staying as volunteers in community policing. The research on volunteer motivations is based on the functionalist theory. An existing instrument, the Volunteer Functions Inventory (VFI), is used to measure the functions. The volunteers' opinions on community policing are also used to measure volunteering motivations consisting of policy, budget, training, tool and necessary equipment, wage and welfare, knowledge and ability of the heads of the local police organizations, and acceptance and respectability from police officers. Subsequently, the volunteers' demographic factors are analyzed with the Volunteer Functions Inventory to come up with a pattern of volunteerism in the community policing in Nonthaburi province. And lastly, the improvements and the strengths of volunteerism in community policing are presented. Volunteers in the community policing in Nonthaburi province of the Local Centre of Cooperation in the Prevention of Crimes, the Mayors, Executive Board's Chairpersons of Subdistrict Administration Organization (SAO), and heads of the local police organizations are studied. The findings from volunteers' demographic factors reveal that the volunteers are elderly, have village committee in the community, a volunteer in other agencies, have long lengths of volunteer service, and have faith in religion. Occupation, education level, income, and the location of volunteer's house do not relate to this pattern. Results indicate that the Understanding and Enhancement motives are predictive of the satisfaction to be and continue working with the Local Centre of Cooperation in the Prevention of Crimes. Community policing provides them an opportunity to seek new experiences and to learn more about various aspect of police task which is of interest to them. They are also attracted to because it gives them an opportunity to maintain or to enhance a positive mood, as well as for reasons of personal growth and to increase self esteem. The relationship between the volunteers' opinion of community policing with the volunteers' motivation reveals that policy, tool and necessary equipment, training, and knowledge and ability of the head of the local police organization are predictive of the motivations in terms of Volunteer Functions Inventory. Finally, this finding shows that wage and welfare is the most important factor for this program, followed by training, law, budget and tool and necessary equipment, insufficient volunteers and cooperation among stakeholders in The Local Centre of Cooperation in the Prevention of Crimes. The recommendation of this thesis is that the Royal Thai Police and Nonthaburi Provincial Police Division should recognize and improve every process of this program according the results of this thesi

Automatic MPI to AMPI Program Transformation Using Photran

Abstract. Adaptive MPI, or AMPI, is an implementation of the Mes-sage Passing Interface (MPI) standard. AMPI benefits MPI applications with features such as dynamic load balancing, virtualization, and check-pointing. Because AMPI uses multiple user-level threads per physical core, global variables become an obstacle. It is thus necessary to con-vert MPI programs to AMPI by eliminating global variables. Manually removing the global variables in the program is tedious and error-prone. In this paper, we present a Photran-based tool that automates this task with a source-to-source transformation that supports Fortran. We eval-uate our tool on the multi-zone NAS Benchmarks with AMPI. We also demonstrate the tool on a real-world large-scale FLASH code and present preliminary results of running FLASH on AMPI. Both results show sig-nificant performance improvement using AMPI. This demonstrates that the tool makes using AMPI easier and more productive.

Ground source heat storage and thermo-physical response of soft clay

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 137-141).Ground source heat storage can condition buildings with reduced consumption of fossil fuels, an important issue in modem building design. However, seasonal heat storage can cause soil temperature fluctuations and possibly deformation of soft clays. This thesis evaluates the thermo-mechanical response of soft clays to seasonal heat storage and associated temperature fluctuations. A literature review reveals that, in normally consolidated to lightly overconsolidated clays, increases in soil temperature can lead to significant plastic strains and a reduction in soil strength. This behavior can be modeled through constitutive formulations that include thermal strain within the elasto-plastic framework of the well-known Modified Cam-Clay Model. The current research uses the MCC Picard (1994) model to study the ground response to a buried heat exchange pipe. The spacing of the pipe was found to govern the effectiveness of ground heat storage. With only one pipe in semi-infinite soil, heat transfer to the ground dissipates quickly and thermal-mechanical interaction is negligible; however, seasonal heat storage is not possible. Closely spaced heat pipes would permit effective seasonal heat storage, but could undergo significant thermally induced consolidation deformations.by Shoshanna Dawn Saxe.S.M

Parallel Seismic Ray Tracing

Seismic ray tracing is a common method for understanding and modeling seismic wave propagation. The wavefront construction (WFC) method handles wavefronts instead of individual rays, thereby providing a mechanism to control ray density on the wavefront. In this thesis we present the design and implementation of a parallel wavefront construction algorithm (pWFC) for seismic ray tracing. The proposed parallel algo- rithm is developed using the stapl library for parallel C++ code.We present the idea of modeling ray tubes with an additional ray in the center to facilitate parallelism. The parallel wavefront construction algorithm is applied to wide range of models such as simple synthetic models that enable us to study various aspects of the method while others are intended to be representative of basic geological features such as salt domes. We also present a theoretical model to understand the performance of the pWFC algorithm. We evaluate the performance of the proposed parallel wavefront construction algorithm on an IBM Power 5 cluster. We study the effect of using different mesh types, varying the position of source and their number etc. The method is shown to provide good scalable performance for different models. Load balancing is also shown to be the major factor hindering the performance of the algorithm. We provide two load balancing algorithms to solve the load imbalance problem. These algorithms will be developed as an extension of the current work

Parallel Program Composition with Paragraphs in Stapl

Languages and tools currently available for the development of parallel applications are difficult to learn and use. The Standard Template Adaptive Parallel Library (STAPL) is being developed to make it easier for programmers to implement a parallel application. STAPL is a parallel programming library for C++ that adopts the generic programming philosophy of the C++ Standard Template Library. STAPL provides collections of parallel algorithms (pAlgorithms) and containers (pContainers) that allow a developer to write their application without reimplementing the algorithms and data structures commonly used in parallel computing. pViews in STAPL are abstract data types that provide generic data access operations independently of the type of pContainer used to store the data. Algorithms and applications have a formal, high level representation in STAPL. A computation in STAPL is represented as a parallel task graph, which we call a PARAGRAPH. A PARAGRAPH contains a representation of the algorithm's input data, the operations that are used to transform individual data elements, and the ordering between the application of operations that transform the same data element. Just as programs are the result of a composition of algorithms, STAPL programs are the result of a composition of PARAGRAPHs. This dissertation develops the PARAGRAPH program representation and its compositional methods. PARAGRAPHs improve the developer's difficult situation by simplifying what she must specify when writing a parallel algorithm. The performance of the PARAGRAPH is evaluated using parallel generic algorithms, benchmarks from the NAS suite, and a nuclear particle transport application that has been written using STAPL. Our experiments were performed on Cray XT4 and Cray XE6 massively parallel systems and an IBM Power5 cluster, and show that scalable performance beyond 16,000 processors is possible using the PARAGRAPH

Dynamic and Static Performance of Large-Capacity Helical Piles in Cohesive Soils

Large-capacity helical piles can provide immense construction and performance advantages over the conventional concrete and steel piles. Nowadays, there is significant interest in using large-capacity helical piles to support foundations that would be subjected to both dynamic and static loading. The main objectives of this thesis are to: investigate the dynamic response and impedances of large-capacity helical piles; develop an analysis methodology for their dynamic response; and investigate their static axial compression and lateral behaviour, considering installation effects on their dynamic and static performances. The thesis presents the first full-scale vertical and horizontal dynamic field testing program executed on large-capacity helical piles, which involved 190 full-scale field load tests on nine instrumented large-capacity helical piles and two driven steel piles with different geometrical configurations installed in cohesive soils. Six piles were tested two weeks after installation and four piles were tested after allowing a recovery period of nine months following installation. One hundred and seventy six field experiments were conducted to evaluate the dynamic response characteristics of single helical piles and driven piles under different levels of vertical and horizontal harmonic excitations. The effects of various parameters, namely: pile length, number of helix plates and inter-helix spacing, excitation intensity, and soil thixotropy on the dynamic response were investigated. The experimental results were compared to the theoretical predictions of the continuum theory considering linear and nonlinear approaches. Reasonable match was found between the predicted response using the nonlinear approach and the measured response for both vertical and horizontal vibrations. The results demonstrated the significant effects of pile installation on forming weak soil zone around the pile, which stiffened with time following installation. This stiffening was manifested in an average increase in pile stiffness of about 43% and in pile damping of 25 to 90% within a nine month period. In addition, the dynamic response of the helical piles was similar to that of the driven piles. The load transfer mechanism of large-capacity helical piles was found to be predominantly through the helical plates and pile toe end bearing. Based on the results of the pile load tests, it is proposed to define the ultimate load of helical piles as the load that corresponds to pile head movement equal to the pile elastic deformation plus 3.5% of helix diameter. The helical piles displayed a superior axial performance with capacities higher than driven pile by about 17 to 85% based on pile configurations. The effects of attached helices and inter-helix spacing were found to be negligible on the pile lateral capacity and performance. The lateral pile load tests were examined numerically using the p-y approach incorporated in LPILE program. The mobilized soil shear strength parameters and soil moduli of subgrade reaction were back-calculated

Parallel Seismic Ray Tracing

Seismic ray tracing is a common method for understanding and modeling seismic wave propagation. The wavefront construction (WFC) method handles wavefronts instead of individual rays, thereby providing a mechanism to control ray density on the wavefront. In this thesis we present the design and implementation of a parallel wavefront construction algorithm (pWFC) for seismic ray tracing. The proposed parallel algo- rithm is developed using the stapl library for parallel C++ code.We present the idea of modeling ray tubes with an additional ray in the center to facilitate parallelism. The parallel wavefront construction algorithm is applied to wide range of models such as simple synthetic models that enable us to study various aspects of the method while others are intended to be representative of basic geological features such as salt domes. We also present a theoretical model to understand the performance of the pWFC algorithm. We evaluate the performance of the proposed parallel wavefront construction algorithm on an IBM Power 5 cluster. We study the effect of using different mesh types, varying the position of source and their number etc. The method is shown to provide good scalable performance for different models. Load balancing is also shown to be the major factor hindering the performance of the algorithm. We provide two load balancing algorithms to solve the load imbalance problem. These algorithms will be developed as an extension of the current work