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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Lightweight Geomaterials for Bridge Approach Utilization on Soft Ground Area) ผู้เขียน: ดร.ธวัชชัย ตันชัยสวัสดิ์, อาจารย์ ,  D.T. Bergado, Taweesak Kanjananak สื่อสิ่งพิมพ์:pdf AbstractConstruction of bridge approach highway embankment using strong but lightweight geomaterials over soft ground will alleviated problems of instability and long-term settlement. Backfills of retaining structure can also be constructed using lightweight materials resulting in lower earth pressure and improved economics. There is a variety of lightweight geomaterials available. However, large volume needed in embankment and backfill construction often places limits on the use of costlier manufactured lightweight materials. This study is aimed on used rubber tire-sand mixtures reinforced with geogrid for embankment on soft ground. The test embankment is constructed in the campus of Asian Institute of Technology (AIT). The geogrid reinforced embankment system is extensively instrumented in the subsoil and within the embankment itself in order to monitor the behavior of the wall both during construction and in the post-construction phases, and thereby to evaluate its performance. The unit weight of rubber tire sand mixture 30:70 by weight is 13.6 kN/m3 compare to conventional backfill sand of 18.0 kN/m3, it is lighter by about 75 %. The settlement magnitude of 122 mm at original ground is less when compare to conventional backfill. Differential settlements are small, so this type of lightweight material is appropriate for highway bridge approach utilization. |
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หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Enhancement of PVD Performance by Thermal and Electro-Osmotic Techniques) ผู้เขียน:ดร.ธวัชชัย ตันชัยสวัสดิ์, อาจารย์, Dennes T. Bergado, Jaturonk Saowapakpiboon สื่อสิ่งพิมพ์:pdf AbstractThis paper examines the innovative techniques for enhancing the performance of the prefabricated vertical drain (PVD) consisting of thermal and electro-osmotic consolidation techniques. The electro-osmotic consolidation of soft Bangkok clay was first studied. Laboratory testing program were done on undisturbed and reconstituted sample in large consolidometer under voltage gradient of 60 and 120 V/m with 24 hours polarity reversal. The time to achieve 90% degree of consolidation induced by electro-osmosis ranged from 1.4 to 2.1 and 2.1 to 2.2 times faster than the normal consolidation with PVD only, for undisturbed and reconstituted samples, respectively. Faster rate of consolidation and higher magnitudes of settlement were achieved at higher voltage gradient. Subsequently, the performances of thermo-PVD which involves increasing simultaneously both the vertical effective stress and the surrounding clay temperature up to 90?C were investigated using the large consolidometer. The test results demonstrated that higher consolidation rates were observed for the clay specimen at elevated temperatures for both undisturbed and reconstituted specimens. This behavior can be attributed to the increase in the clay permeability with temperature. Therefore, raising the clay temperature can enhance the performance of PVD by reducing the drainage retardation at the smear zone around the PVD. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Interaction between Geogrid and Tire Chips-Sand Mixture: Pullout Test Simulation) ผู้เขียน:ดร.ธวัชชัย ตันชัยสวัสดิ์, อาจารย์, Dennes T. Bergado สื่อสิ่งพิมพ์:pdf AbstractThe aims of the study were to measure and calculate the interaction coefficient between geogrid and sand and between geogrid and a tire chips-sand mixture using a laboratory test and numerical simulations. Numerical simulation was imperative for the sensitivity analyses of the laboratory test results to find the important parameters. Two types of material were used as backfill, namely sand and a tire chips-sand mixture. The sand and tire chips in the mixture were in the proportion by weight of 70 and 30%, respectively. Polyfelt geogrid was used as geosynthetic reinforcement with a tensile strength of 97.48 kN/m from the in-air tensile test. Pullout tests were carried out on a large-scale pullout machine. The shear strength parameters of Ayutthaya sand and the tire chips-sand mixture were a 29.8? friction angle with cohesion of 15.6 kPa for sand and a 24.4? friction angle with 14.3 kPa cohesion for the tire chips-sand mixture. The results revealed that the interaction coefficient obtained from the pullout test was 0.7 and 0.6 for the sand and tire chips-sand mix, respectively. Numerical analyses were also performed using finite element software. The results of the numerical simulation agreed reasonably with the laboratory results. Sensitivity analyses were carried out for the pullout test by varying the interaction coefficient and axial stiffness of the geogrid. These two important parameters were found to affect the efficiency of the geogrid reinforcement. |
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หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Interaction between Geogrid Reinforcement and Tire Chip-Sand Mixture) ผู้เขียน:ดร.ธวัชชัย ตันชัยสวัสดิ์, อาจารย์, D.T. Bergado, ดร.สุริยน เปรมปราโมทย์, ผู้ช่วยศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractThe interaction between reinforcing and backfill materials is a significant factor for analysis and design of reinforced earth structures. It can be simplified as pullout resistance and direct shear resistance, which depend on both reinforcing and backfill materials. This study is aimed at studying the interaction between geogrid and tire chip-sand mixture. Numerous experiments including index tests, compaction tests, pullout tests and large-scale direct shear tests were conducted to meet the mentioned objectives. Saint-Gobain and Polyfelt geogrids were selected as reinforcing materials whereas tire chipsand mixtures at the mixing ratios of 30:70, 40:60 and 50:50 % by weight were used as fill materials. The mixture at the mixing ratio of 30:70 % was found to be the most suitable fill material. The pullout resistance and the pullout interaction coefficients of Saint-Gobain geogrids were higher than those of Polyfelt geogrids. In contrast, the direct shear resistance, the direct shear interaction coefficients, and the efficiency values of Polyfelt geogrids were higher than those of Saint-Gobain geogrids. The ultimate tensile strength of Polyfelt geogrid was slightly lower than that of Saint-Gobain geogrid. Finally, Polyfelt geogrid and the tire chip-sand mixture at the mixing ratio of 30:70 % by weight were recommended as reinforcing and backfill materials for field applications. |
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