Rankine classic earth pressure solution has been expanded to predict the seismic active earth pressure behind rigid walls supporting c-φ backfill considering both wall inclination and backfill slope. The proposed formulation is based on Rankine's conjugate stress concept, without employing any additional assumptions. The developed expressions can be used for the static and pseudo-static seismic analyses of c-φ backfill. The results based on the proposed formulations are found to be identical to those computed with the Mononobe-Okabe method for cohesionless soils, provided the same wall friction angle is employed. For c-φ soils, the formulation yields comparable results to available solutions for cases where a comparison is feasible. Design charts are presented for calculating the net active horizontal thrust behind a rigid wall for a variety of horizontal pseudo-static accelerations, values of cohesion, soil internal friction angles, wall inclinations, and backfill slope combinations. The effects of the vertical pseudo-static acceleration on the active earth pressure and the depth of tension cracks have also been explored. In addition, examples are provided to illustrate the application of the proposed method.
Gravelly soil, a mixture of clay and gravel, has been widely used as a core material of high earth core rock fill dams. The triaxial consolidated drained (CD) test for gravelly soil is time-consuming, especially for larger scale test samples because of its low permeability caused by the high content of clay. This study presents a quick triaxial consolidated drained (QCD) test, which can greatly accelerate the CD test on gravelly soil. In the QCD test, the traditional cylindrical specimen was modified to a sand-core cylindrical specimen containing a hollow cylindrical specimen, and the sand column filled in the central hollow. As a result, the sand column in the center of the specimen greatly accelerates the water drainage of the specimen, and both the consolidation stage and the shear stage of the test can be finished quickly. Based on gravelly soil, the comparative tests, including CD tests and QCD tests, are performed. It is concluded that the QCD tests can be conducted more rapidly than CD tests, and the test results of QCD tests, for both stress–strain curves and the parameters of the Duncan–Chang model, are basically identical with that of the CD tests. The QCD test can greatly shorten the studying time on gravelly soil, i.e., the core material of earth core rock fill dams, thus speeding up the future design of dams.
In coastal areas, structures such as cement-soil dams are often eroded by seawater, so it is significant to study how to improve the impermeability of cement-soil. Basalt fiber with a strong tensile property, good stability and a high-performance price ratio was selected as the additive to study the influence of the basalt fiber content on the permeability of soil-cement. The permeability test and the chloride ion permeability test were used to evaluate the best mixing amount. The results of the permeability test showed that, although the permeability coefficient of soil-cement decreased with the increase in the basalt fiber content, the decreased rate of the permeability coefficient showed a slowing trend. The results of the chloride ion permeability test indicated that the chloride ion-related impermeability of soil-cement was enhanced with the increase in the basalt content, which was confirmed by the consistent findings of the contrast permeability test. The comprehensive analysis shows that the optimal content ratio of the basalt fiber was 1.5%. Furthermore, a SEM analysis established that the addition of the basalt fiber reduced the soil-cement porosity, improved the structural compactness and formed a more stable whole. This study could serve as a valuable reference for soil-cement used in projects with impermeability requirements.
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