Compared with other natural fibers, coir fiber has good strength characteristics and long-term anti-biodegradation ability. At present, most studies on randomly distributed coir fiber-reinforced soil have focused on cohesionless soil or granular soil. In this paper, the influence of randomly distributed coir fiber on the deviatoric stress and shear strength index of red clay with different fiber content was assessed by a consolidated undrained (CU) triaxial compression test. Since the hyperbolic variational character of the stress–strain relation of the samples conformed to the hyperbolic hypothesis of the Duncan–Chang model of nonlinear elastic model, the Duncan–Chang model was used to fit it, and the influences of fiber content and confining pressure on the parameters of the Duncan–Chang model were studied. The fiber content was determined by testing to be 0%, 0.2%, 0.25%, 0.3%, 0.35% and 0.4% of the dry soil mass. It has been found that coir fiber distributed in a random radial manner can significantly increase the deviatoric stress of red clay, and thus can be effectively used in the case of soil and fiber mixing. The cohesion of the red clay first increases and then decreases with the increase in fiber content, with an optimum content of 0.3%. The internal friction angle changes little with increasing fiber content.

Although the current ecological engineering technology can reinforce shallow landslides, it cannot reinforce deep landslides. A new type of ecological engineering technology-living tree stump slope protection was developed, aiming at the deficiency of current ecological engineering technology. For living stumps with different tap root lengths, the mechanical properties of the living stump slope and root system were analyzed. The model was based on the finite element method, using the Mohr-Coulomb failure criterion to consider the mechanical plasticity of the soil. The three-dimensional (3D) models of living stumps with different tap root lengths were simulated by embedded beam elements. Changes in stress and strain of soil and root system were simulated. The strength reduction method was used here to calculate the safety factor of the slope. The results showed that long taproots moved the soil shear stress area to deeper soil layers, increasing the stability of the slope. The root system in the middle and lower part of the slope mainly exerted its tensile strength and played a positive role in the stability of the slope. The longer the taproots, the more stable the slope. Slope stability may be affected by root length, spatial root morphology, and the spatial layout of the root system on the slope. Planting living stumps in the middle and lower part of the slope densely was recommended in ecological engineering.

As a novel technology for slope protection, living stumps have demonstrated the ability to significantly enhance slope stability. This study aims to investigate the mechanical properties of living-stump root systems and their reinforcement mechanisms on slopes through three-dimensional modeling tests. Using ABS materials, a 3D model of a living elm stump was created via 3D printing; this was followed by slope model testing. The reinforcement mechanisms of living stumps were examined through a combination of model testing and numerical simulation. The results reveal that the presence of living stumps in the lower and middle sections of a slope causes the maximum-shear-stress zone of the soil to shift deeper. The stress distribution around the living stump is notably improved owing to the lateral root system. Living stumps positioned in the lower part of the slope intersect the potential sliding surface, gradually transferring soil shear stress to the root system through root–soil interactions. Furthermore, the tap roots and lateral roots of living stumps form a robust spatial network that can collectively withstand soil shear stress, thereby enhancing slope stability.

Live stump-supported slopes are an environmentally friendly form of support that utilizes the powerful anchoring and reinforcing effects of deep-rooted plants to enhance slope stability. In order to ensure the safety and stability of embankment slopes during their service life, it is necessary to carry out research on the dynamic characteristics and stability of live stump slopes under train vibration loading. In this study, a large-scale indoor dynamic loading model test with a geometry of 1:7 was carried out on the live stump slope of a ballasted passenger railroad track to explore the attenuation characteristics of additional dynamic stresses, the dynamic displacement response law of the slope surface and the stress response characteristics of the live stumps, and to further investigate the influence of the live stumps on the stability of the slope under the dynamic loading. The results are as follows. (i) Additional dynamic stresses decayed at the bed surface and bed floor at a greater rate than the embankment body, and were significantly affected by dynamic loading when the vertical depth was less than 0.89 m. (ii) The dynamic displacement of the foundation bed is larger than that of the embankment body. The displacement response of the slope near the top and about 1/4 of the elevation of slope is the largest. (iii) The taproot of the living poles has many reverse bending points, and the bending moment of the taproot between the lateral roots shows the law of being larger on the top and smaller on the bottom. (iv) The slope facing has an amplifying effect on the vibration load of the train, and the farther away from the track, the smaller the amplifying effect. The research results have reference significance for the theoretical research and engineering application of living poles.

As a new plant slope protection technology, living stumps can effectively improve slope stability. The current study attemptes to investigate the mechanical characteristics of the root system of living stumps and their reinforcement mechanism on slopes by carrying out a three-dimensional living stump slope modeling test. Using ABS materials, a 3D model of a living elm stump was created by 3D printing and a slope model test was carried out. The reinforcement mechanism of the living stump was studied through a combination of model testing and numerical simulation. The results indicate that, due to the presence of living stumps in the lower and middle parts of the slope, the maximum shear stress area of the soil moved to a deeper direction. The stress state of the soil around the living stump was effectively improved due to the existence of the lateral root system.Living stumps in the lower part of the slope cross the potential sliding surface and transferred the soil shear stress gradually to the root system through root-soil interaction. Moreover, the tap roots and lateral roots of living stumps form a robust spatial structure that bears the shear stress of soil together, thus increasing the stability of the slope.