Thomas J. Weaver

Geotechnical Tests of Sands Following Bioinduced Calcite Precipitation Catalyzed by Indigenous Bacteria

Recentexperimentshaveshownthatexogenousbacteriacanbeintroducedintosoilforthepurposeofinducingcalciteprecipitation. A series of tests are documented in this paper that demonstrate that natural indigenous bacteria can also be stimulated to induce calcite precip- itation with measurable changes in geotechnical properties. Tests reported in this paper include a microcosm experiment with cone-penetration testing and cyclic triaxial shear tests. These experiments demonstrate that indigenous bacteria can induce significant quantities of calcite pre- cipitation, that calcite precipitation can result in measurable changes to geotechnical soil properties, and that the cyclic resistance ratio can be increased substantially with moderate levels of calcite precipitation. Using indigenous bacteria to modify soil properties is a significant step in making biomodification of soils economically viable. DOI: 10.1061/(ASCE)GT.1943-5606.0000781.

Liquefaction Mitigation Using Stone Columns Around Deep Foundations: Full-Scale Test Results

The results presented were developed as part of a larger project analyzing the behavior of full-scale laterally loaded piles in liquefied soil, the first full-scale testing of its kind. Presented here are the results of a series of full-scale tests performed on deep foundations in liquefiable sand, both before and after ground improvement, in which controlled blasting was used to liquefy the soil surrounding the foundations. Data were collected showing the behavior of laterally loaded piles before and after liquefaction. After the installation of stone columns, the tests were repeated. From the results of these tests, it can be concluded that the installation of stone columns can significantly increase the density of the improved ground as indicated by the cone penetration test. Furthermore, it was found that the stone column installation limited the excess pore pressure increase from the controlled blasting and substantially increased the rate of excess pore pressure dissipation. Finally, the stone columns were found to significantly increase the stiffness of the foundation system by more than 2.5 to 3.5 times that in the liquefied soil. This study provides some of the first full-scale quantitative results on the improvement of foundation performance due to stone columns in a liquefiable deposit.

Development and evaluation of hot mix asphalt stability index

This paper addresses the development and evaluation of a mix stability index referred to as the gyratory stability (GS). GS is calculated from the compaction data by summing the cumulative energies dissipated in the compaction of a gyratory sample. A wide range of commonly used mixes in the State of Idaho were selected for evaluation. Mixes were tested for dynamic modulus (E*) and flow number (F N); rutting was measured with the asphalt pavement analyser (APA). Furthermore, E* test results were used in the AASHTO Mechanistic–Empirical Pavement Design Guide (MEPDG) as level 1 inputs, to predict rutting for these mixes; GS ranked mixes similarly to the APA and F N tests and MEPDG results. Furthermore, results indicated that the GS has the potential to be used as a screening tool for asphalt mix design, especially to decide upon the acceptance of the mix aggregate structure, and as a quality control tool.

Pore Pressure Response of Liquefied Sand in Full-Scale Lateral Pile Load Tests

Several full-scale lateral pile load tests were performed at Treasure Island in the San Francisco Bay in sand liquefied by controlled blasting. Cyclic lateral loads were applied to the foundations with displacements up to 225 mm. Piezometers were installed adjacent to, and at a distance up to 4.2 m in front of, the deep foundations. Excess pore pressure ratios observed during testing are presented for the purpose of providing insight into the behavior of liquefied soil in response to laterally loaded piles. Observed excess pore pressure ratios show that soil in the loading path of the foundations experienced a phase transformation at distances as great as 4.2 m. The soil behavior in response to lateral foundation movement is presented based on interpretation of the measured excess pore pressure response.

Lateral Load Behavior of a Concrete-Filled GFRP Pipe Pile

This paper presents results of full-scale lateral load tests to failure of a concrete-filled glass-fiber reinforced polymer (GFRP) pipe pile in comparison to a typical pre-stressed concrete pile. Soil conditions at the test site consisted of fine grained, poorly graded, medium dense sand underlain by soft clay with the groundwater table near the ground surface. A diesel hammer was used to drive the piles. Both the pre-stressed concrete and concrete-filled GFRP piles displayed good drivability. The concrete-filled GFRP pile was more flexible than the standard pre- stressed concrete pile, which resulted in larger displacements at equivalent lateral loads and reduced service load capacity of the GFRP pile. The ultimate lateral load capacity of the concrete-filled GFRP pile was greater than the pre-stressed concrete pile, though the GFRP pile exhibited brittle behavior at failure. A comparison of the predicted and measured behavior shows that concrete-filled GFRP piles can be adequately modeled using traditional p-y curves and classical beam theory.