Search

The benefits of geosynthetic-reinforced soil systems over conventional earth-retaining structures are now well established. These reinforced systems are often subjected not only to static loads, but also to seismic and/or traffic loads, in which case the effects of repeated loading on soil-geosynthetic interaction characteristics should be properly considered. This study investigates the behaviour of a geogrid typically used for soil reinforcement under cyclic pullout loading through load-controlled laboratory pullout tests. To examine the influence of cyclic loading amplitude, number of cycles and static pullout force acting on the geogrid at the onset of cyclic loading, distinct loading patterns are considered. A well-graded residual soil from granite is used as backfill material. A comparison between the cyclic and monotonic pullout response of the reinforcement is then established in order to identify any potential strength loss attributed to cyclic loading. The experimental results show that the ultimate pullout resistance of the geogrid embedded in medium dense residual soil from granite may be adversely affected by cyclic loading. The cumulative cyclic displacements of the reinforcement are more pronounced during the initial loading cycles, but tend to stabilize with the increasing number of cycles when the soil is densely compacted. In the presence of dense soil, the cyclic strains of the geogrid specimen are particularly significant at the front section and almost negligible towards the back end.

In recent years, with the rapid development of cities, the utilization rate of underground space has gradually increased, and anti‐pull piles have also been widely used in practical engineering. In this paper, the failure surface form of the anti‐pull pile was assumed, the soil parameters of each soil layer in the layered foundation and the Poisson effect generated by the anti‐pull pile under the action of the uplift force was considered, and the calculation formula for the bearing capacity of the anti‐pull long pile in the layered foundation was obtained, which was verified by on‐site test data. Finally, the parameter range of the calculation method was analyzed. The results show that when the aspect ratio of the anti‐pull pile is large, and the elastic modulus of the anti‐pull pile is small, the Poisson effect of the anti‐pull pile is obvious, and the increment of pile side friction caused by the Poisson effect is also large. When the value range of parameter N is 50 ≤ N ≤ 100, the calculation results are more reasonable. The average error of the lower limit N = 50 is 11.7%, and the average error of the upper limit N = 100 is 5.3%. [ABSTRACT FROM AUTHOR]

In traffic engineering design in saline soil environments, a salt barrier is usually installed in the embankment to prevent secondary salinization damage on the upper embankment and road surface. However, using this salt barrier method in saline soil subgrade projects in cold and arid highland areas has led to the problem of salt barrier failure, and the failure mechanism remains unclear. The study was performed in the saline soil distribution area in the Qaidam Basin on the northeastern part of the Qinghai–Tibet Plateau. We collected samples from the natural saline soil foundation and the structural layer of the subgrade soil using the method of excavating a road section that had undergone salt barrier failure. Laboratory tests and theoretical calculations were carried out on the particle gradation of the natural saline soils and the structural subgrade soil layers. In addition, their water and salt transport heights and the failure mechanism of the subgrade salt barrier were studied. The results showed that salt chemistry increases the capillary force between the soil grains in highly saline soil environments. This increases the water–salt transport of more than 850.00 mm in saline soils, which is much greater than the capillary water rise in ordinary soils (463.0–650.0 mm). When no water barrier geotextile layer is set in the subgrade structure, there is frequently a high headwater and salt transport in the soil layer of the subgrade structure for a long time. There is continuous vapor and salt transport in the large pores of the coarse‐grained salt barrier. The vibration load of the road surface causes the fine soil particles to migrate downward into the coarse‐grained salt barrier, reducing the thickness of the salt barrier. Under the combined effect of these three effects, the salt barrier of the saline soil subgrade in cold and arid areas fails to resist salt migration, and the subgrade is prone to secondary salinization. [ABSTRACT FROM AUTHOR]

Alkaline activation of fly ashes is a procedure that enables an alternative binder which has been receiving much interest by several research groups particularly on the manufacturing of mortars and concretes. The properties of the materials that are developed during the alkaline activation are influenced by the curing conditions (temperature and relative humidity). Another relevant facet related to the curing procedures is the possibility of carbonation occur, which may have an impact on the mechanical strength of the alkaline cements. In this research, several sets of curing conditions were tested to understand which one results in a higher strength and reveals carbonation. Uniaxial compressive strength tests were conducted to assess mechanical behavior. The outcome suggests that higher temperature and low relative humidity yields higher mechanical strength.

This work aims to study the influence of using construction and demolition waste in the replacement of coarse and fine aggregate to produce recycled aggregate concrete (RAC). A moderate compressive strength concrete made with usual fine and coarse aggregate was used as a benchmark material. Compressive and split tensile tests were performed using 120 cylindrical concrete specimens with 150 mm diameter and 300 mm length. Four-point flexural tests in reinforced beams made with conventional concrete and RAC were performed. The results obtained showed that the use of recycled fine aggregates, in both percentages of substitution investigated—50% and 100%—did not generate any deleterious influence on the values of compressive strength and split tensile strength of the RACs produced. Tin fact, the mechanical strengths of RACs produced with recycled fine aggregate were equal or higher than those from the reference concrete. The same behavior was not observed, however, when the recycled coarse aggregate was used. For this case, decreases in concrete mechanical strengths were observed, especially in compressive strength, with values around 35% lower when compared to the reference concrete. Tensile mechanical tests results confirmed the excellent behavior of all RACs made with replacement of usual fine aggregates by recycled. Bending tests performed in reinforced RAC beams had as objective to evaluate the deformation profile of the beams. The obtained results showed that RAC beams with full replacement of usual fine aggregate by the recycled aggregates have presented little changes in the global behavior, an aspect that encourages its use.