A new slip surface in noncohesive slopes

Determining the slope slip surface is difficult, prominent and uncertain. Slip-surface are utilized to estimate slope safety. This study aimed at investigating the slip surface caused by statistical loads by using experimental testing methods. The experimental method was conducted by providing a statistical load on the sand slope The load was used until the slope collapsed. Sand slopes were modeled in a glass box measuring 110 cm x 40 cm x 10 cm. The sand material used was sand that passed through sieve no.10 and was held by sieve no. 200. At a distance of 2.5 cm horizontally and at a distance of 5 cm vertically, colored marks were used to see the pattern of grain movement. Observations were conducted until the slope collapsed. The collapse pattern revealed in the experimental method is non-circular.

Application of Harmony Search Algorithm to Slope Stability Analysis

Slope stability analysis is undoubtedly one of the most complex problems in geotechnical engineering and its study plays a paramount role in mitigating the risk associated with the occurrence of a landslide. This problem is commonly tackled by using limit equilibrium methods or advanced numerical techniques to assess the slope safety factor or, sometimes, even the displacement field of the slope. In this study, as an alternative approach, an attempt to assess the stability condition of homogeneous slopes was made using a machine learning (ML) technique. Specifically, a meta-heuristic algorithm (Harmony Search (HS) algorithm) and K-means algorithm were employed to perform a clustering analysis by considering two different classes, depending on whether a slope was unstable or stable. To achieve the purpose of this study, a database made up of 19 case studies with 6 model inputs including unit weight, intercept cohesion, angle of shearing resistance, slope angle, slope height and pore pressure ratio and one output (i.e., the slope safety factor) was established. Referring to this database, 17 out of 19 slopes were categorized correctly. Moreover, the obtained results showed that, referring to the considered database, the intercept cohesion was the most significant parameter in defining the class of each slope, whereas the unit weight had the smallest influence. Finally, the obtained results showed that the Harmony Search algorithm is an efficient approach for training K-means algorithms.

Elastoplastic-damage-seepage coupling model and numerical algorithm for rock slope stability evaluation

The stability of slope under complex geological conditions is one of the essential issues in geotechnical engineering. The mechanical damage caused by external force load and the hydraulic property of rock have both significant influences on slope stability. However, the two factors and the coupling process between them are not considered in the traditional slope safety calculation method. Firstly, in this paper, an elastoplastic-damage-seepage coupling model is established based on the modified Mohr-Coulomb (M-C) criterion. This model takes into account the weakening effect of damage on the strength of rock mass. Further, according to the Biot's theory and the evolution equation of permeability coefficient, a complete hydraulic-mechanics (HM) coupling model is established. Secondly, the fully implicit backward Euler algorithm and "strict-cornered" algorithm are used to integrate the stress precisely. The complete coupling analysis of HM is implemented by the step-by-step iterative method. By combining the centrifugal loading method (CLM) with the FEM program, the factor of slope safety (FOS) under the coupling influence of damage-seepage can be solved. The calculation results showed that, compared with the traditional rounded M-C model, the results obtained by the "strict-cornered" algorithm method in this paper are closer to the theoretical solution. The solution process is robust with a global second-order convergence rate. After considering the effects of damage and seepage, the FOS is obviously reduced. Finally, the model is applied to the stability evaluation of an actual engineering. The variation rules of pore water pressure, displacement field, damage zone and FOS are calculated under different head heights. The model built in this paper considers the coupling characteristics of rock seepage-stress-damage well. The proposed numerical algorithm ensures the accuracy and rationality of the calculation results which provides a theoretical foundation for engineering application.

Limit Analysis, Numerical and Physical Modelling of Pile Stabilized Slopes

Vast researches have been performed in the field of earth slope stability analysis including limit equilibrium, strength reduction, and limit analysis methods. All the available methods present slope safety factors in a range with a bit of difference and confirm each other. Validation of analytical results performs with instrumentation in actual slopes existing in the field. Also, another approach that uses for validating results is experimental modeling. The physical modeling requires manufacturing of the intended model in the laboratory concerning the reducing effect of dimensions on the other parameters. This paper investigates slope safety factors against sliding by simulating the slopes in the laboratory and with an image processing system. The test container has dimensions of 1.5×1.5×2 m. The results have illustrated the crest displacement in reinforced slope, with increasing slope angle 13 degrees, is 30 mm in the experimental test and 13 mm in numerical modeling. In the unreinforced slopes, when the slope angle increased by 8 degrees, the experiment test failed, and the factor of safety in the numerical modeling is less than one.

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.

Unsaturated seepage and stability of double-layer slope under rainfall infiltration

Taking a homogeneous double-layer soil slope as an example, the SEEP/W module and SLOPE/W module in the finite element analysis software GeoStudio were used in this paper. Then, the changes of pore water pressure and stability under different rainfall patterns and soil parameters were studied. Finally, the variation curves of pore water pressure and slope safety factor with rainfall time were obtained. The results show that: Soil parameters a and m are directly proportional to the slope safety factor, while n is inversely proportional to the slope safety factor. Under the condition of continuous rainfall, the decreasing rate of slope safety factor is directly proportional to the rainfall intensity.Under different rainfall patterns, the continuous rainfall in the advanced and normal rainfall patterns will cause the slope stability to decline and then gradually recover, while delayed and averaged rainfall patterns rainfall will cause the slope stability to decline continuously.In addition, there is a lag period in the change of slope safety factor, and the whole lag period lasts about 6 hours. During the lag period, the pore water pressure inside the soil began to decrease, while the slope safety factor continued to decrease. The safety factor starts to recover after the lag period ends.