Silt is widely distributed in North China Plain, especially in the Yellow River flood basin. Unfortunately, untreated silt cannot be directly used as a subgrade filler. Therefore, it is of great practical significance to explore the reinforcement of silt in the Yellow River flood basin. To solve this problem, the dynamic characteristics of silt added with different proportions of lignin were studied. The correlation among lignin content, curing time, dynamic shear modulus, and damping ratio of the improved soil was tested. The results showed that the dynamic strength and shear modulus can be effectively improved by adding lignin. The optimal lignin content for the dynamic strength and shear modulus was 5%. To understand the microscopic mechanism of lignin-treated silt, scanning electron microscopy (SEM) was performed on lignin samples. The SEM results showed that with an increase in lignin content, a certain amount of cementitious materials was formed in the soil. These cementitious materials wrap up the soil particles and connect the fine soil particles to form larger aggregates. The research results can provide a reference to further improve the physical and mechanical properties of the silt in the Yellow River flood basin, and this study is instructive.

Anti-slide piles were used in the region of the Zhenzilin landslide in Sichuan, China. The horizontal displacement of these piles exceeds specifications. Deterioration in bedrock properties may cause deformation, thereby causing landslide destabilization. An approach was developed for the analysis of anti-slide pile in two bedrocks with different strengths below the slip surface. A relationship has been established between the modulus of subgrade reaction of the first weak bedrock and reasonable embedded length for landfill slopes with strata of various strengths. Furthermore, the influence of embedding length on deformation has been studied to determine the reasonable embedded length, which helps reduce deformation and ensure landslide stability. The results reveal that (1) at a constant embedded length, horizontal displacement increases with the thickness of the first soft bedrock, meanwhile the maximum shear force remains constant, and the bending moment first increases followed by subsequent decrease; (2) with an increase in the embedded length, horizontal displacement and the maximum shear force of the pile in the embedded bedrock decrease, whereas the bending moment increases; (3) the maximum internal forces and horizontal displacement increase with a decrease in the subgrade reaction modulus of the first weak rock; and (4) the reasonable embedded length of an anti-slide pile increases with a decrease in the subgrade reaction modulus of the first weak bedrock. The proposed approach can be employed to design anti-slide piles in similar landslide regions to control pile-head deformation.

This paper investigates the response of finned piles in sand subjected to static lateral load through laboratory tests and full-scale field tests. Firstly, model tests were carried out on free headed single piles of different shaft diameters with and without fins in sand to explore the performance of the piles under lateral loading. The results obtained from monotonic loading tests on three series of piles of three different combination of fins and pile shaft diameters were presented. The effect of fins on improving the stiffness and ultimate lateral capacity of the piles was discussed. An equivalent diameter was proposed for a finned pile, which enabled the experimental results to be back calculated using an available elasto-plastic solution for laterally loaded piles in sand. Secondly, field tests were conducted on laterally loaded Starfin screw piles in loose to medium dense sand. The proposed approach was then used for the analysis of the measured response of Starfin screw piles and further validated against measured test results from fully instrumented finned piles in overconsolidated dense sand. The results show that the proposed equivalent diameter and approach for the analysis of finned piles provided the most satisfactory match to the measured data, ranging from the initial elastic state to the ultimate limit state.

With the development of infrastructure construction, an increasing number of projects are faced with the problem of hydraulic and dynamic coupling. However, traditional physical model materials mainly consider the single factor influence and lack comprehensive research on the hydraulic and dynamic parameters of similar materials. Based on the dimensionless criterion and Buckingham π theorem, the dimension and similarity relation of physical model tests of rock masses under seepage and dynamic coupling are derived. A new type of similar material considering hydraulic and dynamic properties was developed by using quartz sand, barite powder, cement, water glass, rosin, and glycerol as raw materials through a large number of orthogonal tests. Meanwhile, the sensitivity analysis of the physical and mechanical properties of similar materials was carried out and the influence of each component factor on the physical properties was revealed. A material preparation scheme was developed to meet the physical and hydraulic characteristics of different rock and soil physical models. An empirical matching formula considering each parameter is proposed. This work can provide an important reference for physical model tests of similar rock masses.