Unified Failure Strength Criterion for Terrace Slope Reinforcement Materials

This paper presents a study on the failure strength criterion of terrace slope reinforcement materials, such as lean cemented sand and gravel (LCSG) material, under a triaxial stress state. Cement content and confining pressure were selected as major factors to investigate their influence on the peak stress of terrace slope reinforcement materials based on experimental results and data from the literature. The mechanical properties of the LCSG samples, with cement contents of 60, 80, and 90 kg/m3, and noncemented sand and gravel materials were tested under four confining pressure levels (namely, 300, 600, 1000, and 1500 kPa). The results show that the strength of LCSG material improves as the confining pressure increases. When the confining pressure exceeds 1200 kPa, the rate of increase of the strength for LCSG material and other cemented grained materials declines generally. The material strength displays a linear increase with the growth of the cement content. When the axial load rises up to a certain value, damage will occur at the particle cemented site near the shear plane, and the resistance stress generated by the cementation shows a trend of growth first and then attenuation, and concurrently, the friction between particles increases by degrees. Based on the identified strength characteristics of LCSG material under different cement contents and confining pressures, a new strength criterion that incorporates the frictional strengths and the cementing strengths is proposed for LCSG and other similar materials. The results of this work can provide an important theoretical basis for the stability calculation of terrace slopes and LCSG dams.

Evaluation of the Effect of Hydroseeded Vegetation for Slope Reinforcement

A landslide is a significant environmental hazard that results in an enormous loss of lives and properties. Studies have revealed that rainfall, soil characteristics, and human errors, such as deforestation, are the leading causes of landslides, reducing soil water infiltration and increasing the water runoff of a slope. This paper introduces vegetation establishment as a low-cost, practical measure for slope reinforcement through the ground cover and the root of the vegetation. This study reveals the level of complexity of the terrain with regards to the evaluation of high and low stability areas and has produced a landslide susceptibility map. For this purpose, 12 conditioning factors, namely slope, aspect, elevation, curvature, hill shade, stream power index (SPI), topographic wetness index (TWI), terrain roughness index (TRI), distances to roads, distance to lakes, distance to trees, and build-up, were used through the analytic hierarchy process (AHP) model to produce landslide susceptibility map. Receiver operating characteristics (ROC) was used for validation of the results. The area under the curve (AUC) values obtained from the ROC method for the AHP model was 0.865. Four seed samples, namely ryegrass, rye corn, signal grass, and couch, were hydroseeded to determine the vegetation root and ground cover’s effectiveness on stabilization and reinforcement on a high-risk susceptible 65° slope between August and December 2020. The observed monthly vegetation root of couch grass gave the most acceptable result. With a spreading and creeping vegetation ground cover characteristic, ryegrass showed the most acceptable monthly result for vegetation ground cover effectiveness. The findings suggest that the selection of couch species over other species is justified based on landslide control benefits.

Optimal Design and Numerical Analysis of Soil Slope Reinforcement by a New Developed Polymer Micro Anti-slide Pile

As a new material, polyurethane polymer has been widely used in engineering in recent years due to the excellent engineering mechanical properties. Based on the characteristics of this material, a multi pipe grouting micro anti-slide pile is proposed, which is formed by using polymer slurry as grouting material. Compared with traditional anti-slide pile, the polymer micro pile has the advantages of strong applicability, no water reaction, small disturbance, fast construction, economy and durability. As a flexible retaining structure, polymer micro-piles can strengthen the slope by cooperating with the forces. However, there is no report on the reinforcement of slope by polymer micro piles at present. In this paper, a three-dimensional multi row polymer micro piles model for slope reinforcement considering different embedded depth and pile location is established. Safety factor, thrust force of landslide behind pile, length of pile and mises stress are taken as four factors to evaluate reinforcement effect, the optimal reliability of polymer micro anti-slide pile for slope reinforcement is evaluated by giving different weight values to each factor through multi factor comprehensive evaluation method. The safety factor of slope (Fs), landslide thrust behind pile and mises stress of pile are analyzed under different embedded depth (le) and pile position (px). The results show that the best embedded depth is about1/8 − 1/12 of the horizontal length of the landslide behind the pile when multi row polymer micro piles are used to reinforce the slope; the optimum position of pile arrangement is 0.55–0.65 times the slope length from the top of the slope.

ANALISIS PENGARUH TEKANAN AIR PORI PADA LERENG YANG DIPERKUAT DENGAN GEOTEKSTIL

ABSTRACTInfrastructure development in Indonesia is growing rapidly. With the large number of infrastructure developments in various slope topographies, it is one of the locations that is part of this development. The slope area is prone to landslides so that strengthening is necessary. One of the reinforcement that can be done is with geotextiles. In its installation, it is necessary to calculate the correct length and strength of the geotextile for reinforcement. The tensile strength and length of the geotextile as well as the parameters of the embankment affect the safety factor of slope construction. One of the factors being considered is the pore water pressure which reduces the slope strength. So that the results of this study will show how much the influence of pore water pressure on slope reinforcement with geotextiles. After analysis, it was found that the increase of pore water pressure resulted in decreasing of slope safety factor.ABSTRAKPembangunan infarstruktur di Indonesia berkembang sangat pesat. Dengan banyaknya pembangunan imfrastruktur di berbagai topografi lereng menjadi salah satu lokasi yang menjadi bagian dalam pembangunan tersebut. Daerah lereng rawan akan terjadinya longsor sehingga perlu dilakukan perkuatan. Salah perkuatan yang dapat dilakukan adalah dengan geotekstil. Dalam pemasangannya dibutuhkan perhitungan panjang dan kuat geotekstil yang tepat untuk perkuatan. Kuat tarik dan panjang geotekstil serta parameter tanah timbunan mempengaruhi faktor keamanan konstruksi lereng. Salah satu faktor yang dipertimbangkan adalah tekanan air pori yang menjadi penurunan kekuatan lereng. Sehingga hasil studi ini akan menunjukkan seberapa besar pengaruh tekanan air pori pada perkuatan lereng dengang geotekstil. Setelah dilakukannya analisis didapatkan bahwa kenaikan tekanan air pori mengakibatkan penurunan nilai faktor keamanan lereng.