Biopolymers have recently been used as ecofriendly materials for soil improvement in terms of stabilization, compressibility, and engineering parameters. The objective of this study is to assess the effect of biopolymer content in sand mixtures during freeze - thaw repetitive loading cycles. The biopolymers were mixed at weight ratios of 0.0, 0.5, 1.0, 2.0, 5.0, and 10 % (BPC 0.0 - BPC 10), and the relative density and degree of saturation were fixed at 60 % and 20 %, respectively. The measurement system was located in an ice chamber for freeze - thaw, and 100 cycles of repetitive loads were applied. The test results showed that the deformation decreased from BPC 0.0, to BPC 1.0 owing to the cementation effect produced by the biopolymer chain and coating. However, the deformation increased from BPC 1.0 to BPC 5.0 because high -viscosity solutions might separate the sand particles, causing a density reduction and generating more deformation by compaction. The relative permittivity varied with respect to BPC and freeze - thaw repetitive loading stages that were affected by unfrozen water content, volume contraction, and water consumption during dehydration. The shear wave velocity gradually increased from BPC 2.0 to BPC 10 because the effect of fines in coarse - fine mixtures, rather than the cementation effect. Therefore, the module containing the sensors used in this study can be used to understand the role of biopolymers as reinforcing materials in railway subgrades.

This paper reports several plane-strain trapdoor tests conducted to investigate the effects of reinforcement on soil arching development under localized surface loading with a loading plate width three times the trapdoor width. An analogical soil composed of aluminum rods with three different diameters was used as the backfill and Kraft paper with two different stiffness values was used as the reinforcement material. Four reinforcement arrangements were investigated: (1) no reinforcement, (2) one low stiffness reinforcement R1, (3) one high stiffness reinforcement R2, and (4) two low stiffness reinforcements R1 with a backfill layer in between. The stiffness of R2 was approximately twice that of R1; therefore, two R1 had approximately the same total stiffness as one R2. Test results indicate that the use of reinforcement minimized soil arching degradation under localized surface loading. Soil arching with reinforcement degraded more at unloading stages as compared to that at loading stages. The use of stiffer reinforcement had the advantages of more effectively minimizing soil arching degradation. As compared to one high stiffness reinforcement layer, two low stiffness reinforcement layers with a backfill layer of certain thickness in between promoted soil arching under localized surface loading. Due to different states of soil arching development with and without reinforcement, an analytical multi-stage soil arching model available in the literature was selected in this study to calculate the average vertical pressures acting on the trapdoor or on the deflected reinforcement under both the backfill self-weight and localized surface loading.

Although the internal stress state of soils can be affected by repetitive loading, there are few studies evaluating the lateral stress (or K0) 0 ) of soils under repetitive loading. This study investigates the changes in K0 0 and directional shear wave velocity (Vs) s ) in samples of two granular materials with different particle shapes during repetitive loading. A modified oedometer cell equipped with bender elements and a diaphragm transducer was developed to measure the variations in the lateral stress and the shear wave velocity, under repetitive loading on the loading and unloading paths. The study produced the following results: (1) Repetitive loading on the loading path resulted in an increase in the K0 0 of test samples as a function of cyclic loading number (i), and (2) Repetitive loading on the unloading path resulted in a decrease in K0 0 according to i. The shear wave velocity ratio (i.e. Vs(HH)/Vs(VH), s (HH)/V s (VH), where the first and second letters in parentheses corresponds to the directions of wave propagation and particle motion, respectively, and V and H corresponds to the vertical and horizontal directions, respectively) according to i supports the experimental observations of this study. However, when the tested material was in lightly over-consolidated state, there was an increase in K0 0 during repetitive loading, indicating that it was the initial K0, 0 , rather than the loading path, which is responsible for the change in K0. 0 . The power model can capture the variation in the K0 0 of samples according to i. Notably, the K0 0 = 1 line acts as the boundary between the increase and decrease in K0 0 under repetitive loading. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Steelmaking slag, which is used as a construction material, can be crushed during compaction or repetitive loading in construction work. This crushing has a considerable influence on its physical and mechanical properties. Therefore, this study aims to evaluate/estimate the crushing properties and particle size distribution of steelmaking slag under various compaction loads. Accordingly, compaction tests were conducted by subjecting steelmaking slag with 10 different particle sizes to an increasing number of compaction cycles (1-15 times) to simulate repetitive compaction loading. The compaction test results were analyzed by considering the particle size distribution, particle size distribution curve, breakage factors, and fractal dimension. The results revealed that these factors could be influenced by changing the voids in steelmaking slag by altering the repetitive compaction load and particle size. An equation for predicting the particle size distribution from the compaction energy and particle size based on the sequence limit with the rational and the recurrence formulas was proposed. The proposed equation demonstrated excellent accuracy, and it can be utilized in efficiently predicting the particle size distribution curve.