Reducing Centerline Rumble Strips Effects on Pavement Performance

Centerline rumble strips (CLRS) have proven to be a cost-effective safety measure in reducing lane departure crashes. However, there are often unintended consequences associated with the installation of CLRS, particularly in rural mountainous areas or snow zones. These consequences include the accumulation of water and ice on the roadway and the potential deterioration of the pavement longitudinal joint, both of which are safety concerns. In order to provide a safe and reliable transportation system, appropriate traffic safety features and pavements in fair or better condition are required. Despite numerous research studies inspecting the safety benefits of CLRS on pavements, there has been a limited exploration into the impact on pavement durability as a result of the installation of CLRS. Although CLRS installation could reduce pavement performance and life, many states and countries continue to actively implement CLRS on roads to improve safety. The major purpose of this study was to corroborate what specific factors are controlling the cracking failures due to the installation of CLRS and find solutions to mitigate CLRS-related failures on the roadway. In this study, a test strip was constructed at the local Knife River facility in Corvallis, Oregon where CLRS were milled into the asphalt pavement. Potential CLRS cracking performance factors examined in the laboratory testing included: CLRS type, CLRS geometry, CLRS depth, CLRS position relative to the longitudinal joint, climate, and surface treatment. Three-point flexural fatigue, Hamburg Wheel Tracking, and moisture infiltration testing methods were developed and utilized for the study. The primary findings showed that sinusoidal CLRS had optimal performance, shallower and smaller rumble strips had less structural impact, and chip seal surface treatment was an effective method to prevent moisture infiltration. The next portion of the study was X-ray Computed Tomography (CT) imaging, and its purpose was to determine the presence of microcracks in the asphalt pavement due to rumble strip milling. Cores were extracted from various locations along the rumble strips at the Knife River test section. Results demonstrated the presence of microcracks at all milled rumble strip locations. The final component of the study was Finite Element Analysis (FEA) modeling. This was conducted to simulate moving tire loads over a full-scale asphalt pavement section containing CLRS. Factors examined included speed, asphalt stiffness, CLRS type, CLRS geometry, CLRS depth, tire orientation, and rumble strip location. The optimal CLRS configuration included sinusoidal rumble strips installed adjacent to the longitudinal joint with shorter wavelength. The FEA results verified the findings of the laboratory testing while allowing for the examination of additional factors not tested in the field. Potential failure mechanisms and construction recommendations were developed based on the results of the laboratory testing, X-ray CT imaging, and FEA. Implementation of the recommended construction practices has the potential to improve the cracking performance of CLRS and extend pavement life

Evaluation of Cementitious Injection Grouts for the Stabilization of Holly Tower Support Rock, Hovenweep National Monument

This thesis addresses the testing and evaluation of the use of a cementitious injection grout for the reattachment of detached slabbing on the sandstone support rock of Holly Tower at Hovenweep National Monument. This research follows on a previous condition assessment and diagnosis of the deterioration of the sandstone support rock and the effects of consolidation on the rock as the first step in a multi-phase conservation program. The extreme instability of the slabbing on the west side of the support rock requires remedial intervention that will retain and reattach the slab to the parent rock. Injection grouting was identified as a viable option for reattachment, requiring the development of an intensive testing regimen to determine the physical and mechanical properties of a commercial cementitious grout

Development of an experiment to study the effects of transverse stress on the critical current of a niobium-tin superconducting cable

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references (leaves 197-199).Superconducting magnets will play a central role for the success of the International Thermonuclear Experimental Reactor (ITER). ITER is a current driven plasma experiment that could set a milestone towards the demonstration of fusion as a source of energy in the future. Cable-in-Conduit is the typical geometry for the conductor employed in superconducting magnets for fusion application. The cable is composed of over 800 strands. Once energized, the magnets produce an enormous electromagnetic force defined by the product of the current and the magnetic field. The strands move under the effect of this force, and the force accumulates against one side of the conduit thereby pressing transversally against the strands. The experiment proposed here has the goal of assessing the functionality of the apparatus designed to study the effect of transverse load on a cable composed of 36 superconducting strands (with a 3x3x4 pattern) by mechanically simulating the ITER Lorentz stress condition. The apparatus was assembled at MIT and preliminary tests at 77 K and room temperature were made to improve the design prior to carrying out the actual experiments. These were done at the National High Magnetic Field Laboratory (NHMFL) located in Florida. Ideally, the transverse conditions simulating the ITER conditions should be created by Lorentz forces due to current and magnetic field. Unfortunately to create such a high level of stress, currents higher than the power supply capability at NHMFL (10 kA) would be required. This is the driving reason to have an apparatus simulating the same stress condition mechanically.The first test was conducted in October 2005. It was possible to test the structure and its range of operation. Critical current measurements were made as a function of different fields. However during the first measurement, under the loading conditions, the sample was irreversibly damaged and no other measurements were possible. The successful test of the structural behavior of the apparatus motivated a second test carried out in January 2006. With the improvements made between the two experiments, it was possible to successfully measure the degradation of the cable as a function of the transverse pressure applied, measuring degradation as high as 50% with a transverse load of 100 MPa. The ultimate goal of these studies is to characterize the critical current behavior as a function of transverse load in order to predict the response of a full sized Cable-in-Conduit. The work in this thesis was used to explore a setup for measurements and measurement technique. A set of empirical equations describing the behavior of full size cables is needed and should be addressed with a new project that extends the work done so far.by Luisa Chiesa.S.M