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A series of centrifuge model tests were conducted to investigate the contribution of root reinforcement to slope stability. A compacted sandy clay slope, inclined at 45°, was reinforced with model roots. The model roots were varied in material, architecture, and numbers. They had stiffness values corresponding to upper and lower values found for pl...
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... paper reports the results of a series of centrifuge model tests of a 45° inclined slope (e.g., Fig. 1). The slopes were reinforced with different numbers and types of model roots and brought to failure by increasing the pore-water pressure within the slope. The control of root and soil charac- teristics as well as the hydraulic conditions at failure allowed direct examination of how roots affected slope stability. Fi- nally, the ...
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... moments stop increasing for very large slope dis- placements, possibly suggesting a migrating shear plane. Figure 10 shows the distribution of the axial forces and the bending moment in the straight section of the strain-gauged roots in rows 2 and 3 at crucial times in the test. The axial load (root row 3) is evenly distributed over the whole root before displacement starts to increase significantly (Fig. 10a). ...
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... possibly suggesting a migrating shear plane. Figure 10 shows the distribution of the axial forces and the bending moment in the straight section of the strain-gauged roots in rows 2 and 3 at crucial times in the test. The axial load (root row 3) is evenly distributed over the whole root before displacement starts to increase significantly (Fig. 10a). Figure 10b shows that the maximum bending moment was measured about mid-depth along the strain-gauged root in row 3. This is consistent with the shear plane crossing the root at about this depth as shown in Fig. 8. In contrast, the strain-gauged root in row 2 experienced maximum axial load- ing (Fig. 10c) and bending (Fig. 10d) near ...
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... axial load (root row 3) is evenly distributed over the whole root before displacement starts to increase significantly (Fig. 10a). Figure 10b shows that the maximum bending moment was measured about mid-depth along the strain-gauged root in row 3. This is consistent with the shear plane crossing the root at about this depth as shown in Fig. 8. ...
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... starts to increase significantly (Fig. 10a). Figure 10b shows that the maximum bending moment was measured about mid-depth along the strain-gauged root in row 3. This is consistent with the shear plane crossing the root at about this depth as shown in Fig. 8. In contrast, the strain-gauged root in row 2 experienced maximum axial load- ing (Fig. 10c) and bending (Fig. 10d) near the soil surface, confirming that its main loading was due to a shear plane in- tersecting it near the soil surface. . Increasing slope displacement with time and pore-water pressure (wooden dichotomous root). (a) Pore-pressure variation (PPT D) and slope displacement against time (entire test); (b) slope displacement against time ...
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... vectors show the root and inclinometer displacements calculated using PIV during the early stages of failure (t = 12 570 to 13 360 s). Figure 11 shows the measured axial loads and bending moments for the middle pair of strain gauges in the root in row 3 plotted against measured pore-water pressure, with slope movements also plotted alongside to highlight stages of the test. Following initial excess pore-water pressure dissi- pation after spin-up (labelled "consolidation" in Fig. 11a), pore-water pressure increases as the water table rose are shown to increase the axial stress in the roots as expected, and these loads increased before significant soil displace- ments were observed. ...
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... s). Figure 11 shows the measured axial loads and bending moments for the middle pair of strain gauges in the root in row 3 plotted against measured pore-water pressure, with slope movements also plotted alongside to highlight stages of the test. Following initial excess pore-water pressure dissi- pation after spin-up (labelled "consolidation" in Fig. 11a), pore-water pressure increases as the water table rose are shown to increase the axial stress in the roots as expected, and these loads increased before significant soil displace- ments were observed. However, there appeared to be little contribution towards slope stability (i.e., increase in axial force) until the pore-water pressure ...
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... middle section of the slope (e.g., row 3) showed similar behaviour, but axial load was first mobilized at approximately 37 kPa (i.e., closer to failure of the slope). Figure 11b confirms that larger water pressures of 46 kPa (>28 kPa) were required for mobilization of bending moments in the roots, compared to axial forces. ...
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... the pull-out capacity of the roots was likely to be significantly smaller as was the ex- pected slope reinforcement. Figure 12 shows images captured during progression of the slope failure. First, an almost vertical tension crack developed just below the crest (Fig. 12a), which appears to be about to intercept the highest root (row 5) about two-thirds along its length. ...
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... root), the roots in wooden taproot test were un- branched (Table 1). Consequently, the pull-out capacity of the roots was likely to be significantly smaller as was the ex- pected slope reinforcement. Figure 12 shows images captured during progression of the slope failure. First, an almost vertical tension crack developed just below the crest (Fig. 12a), which appears to be about to intercept the highest root (row 5) about two-thirds along its length. At this stage there is evidence of some root bending and pull-out -translation near the root tips. The main slope failure had developed when the image was captured for Fig. 12b and the shear plane clearly crosses the highest row of roots ...
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... an almost vertical tension crack developed just below the crest (Fig. 12a), which appears to be about to intercept the highest root (row 5) about two-thirds along its length. At this stage there is evidence of some root bending and pull-out -translation near the root tips. The main slope failure had developed when the image was captured for Fig. 12b and the shear plane clearly crosses the highest row of roots breaking the top root about half way down its length. At this point, large downslope movements had occurred of approximately 28 mm (420 mm at prototype scale) at an an- gle of -55° to the horizontal (i.e., steeper than the initial slope angle) and thus the slope may be ...
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... had occurred of approximately 28 mm (420 mm at prototype scale) at an an- gle of -55° to the horizontal (i.e., steeper than the initial slope angle) and thus the slope may be considered to have reached collapse state. However, with a further increase in water pressure, deeper shear planes (with accompanying ten- sion cracks) were observed (Fig. 12c), which appear to be below the level of the roots. This suggests that the reinforc- ing effect of the roots had led to the failure mechanisms be- coming deeper and this was supported by root strains that reduced with large slope ...
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... test had the same conditions as the previous branched test (wooden dichotomous root) except that rubber was used as the root material. Figure 13 shows an image captured dur- ing slope failure. The middle height root (row 3) is subjected to the similar type of soil loading as the equivalent wooden root shown in Fig. 8. ...
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... which allows for full user control and quick cross-checks for alternative slope analysis methods and different slope conditions. More information about the program is given by Greenwood (2006). In calculations, the measured phreatic surface position when failure started was used together with the failure plane observed in the centri- fuge test (Fig. ...
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... may be replaced by s t = T o /A, where T o is the axial pull-out resistance of a root and A is the cross-sectional area of the root. 12. Images of slope failure in wooden taproot test (consolida- tion finished after 3710 s): (a) just after generation of tension crack (5310 s); (b) at onset of primary slope failure (5430 s); (c) during development of second tension crack (5600 s). ...
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... T o is the axial pull-out resistance of a root and A is the cross-sectional area of the root. 12. Images of slope failure in wooden taproot test (consolida- tion finished after 3710 s): (a) just after generation of tension crack (5310 s); (b) at onset of primary slope failure (5430 s); (c) during development of second tension crack (5600 s). Fig. 13. Image of slope failure in rubber dichotomous root test. The pull-out resistance of a root has been studied by a number of researchers (e.g., Ennos 1989Ennos , 1990Ennos , 2000Mickovski et al. 2007a). Mickovski et al. (2007b) suggested sim- ple equations for the pull-out capacity of unbranched and branched roots based on standard axial ...
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... force of approx- imately 26 N measured on the root in row 3 (Fig. 9a). The axial force taken up by the roots depends on their position within the slope and the position of the shear plane. The root in row 2 was the first in the test to experience axial loading, but a higher axial force was observed for the root in row 3 by the end of the test (Fig. ...
Citations
... Through the interaction of the root and soil, the taproot transmits the thrust of slope sliding to a deeper and more stable soil layer. Slope sliding is prevented due to the anchorage and passive resistance of the stable stratum to the vertical taproot, resulting in improved slope stability [35]. Through the excavation of the test slope, it was discovered that the soil at the position of the living stumps is compact and that the soil particles are bound more effectively by the roots. ...
... Through the interaction of the root and soil, the taproot transmits the thrust of slope sliding to a deeper and more stable soil layer. Slope sliding is prevented due to the anchorage and passive resistance of the stable stratum to the vertical taproot, resulting in improved slope stability [35]. Through the excavation of the test slope, it was discovered that the soil at the position of the living stumps is compact and that the soil ...
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.
... When a physical model test is used to study slope failure, one critical aspect is the selection of the factor inducing slope failure. By selecting a centrifugal force as the failure-inducing factor to simulate enhanced gravity, centrifuge model tests have been widely used to study the failure mechanisms of rock or soil slopes (Nova-Roessig and Sitar 2006;Pant et al. 2015;Sonnenberg et al. 2012). In contrast, base friction model tests have been adopted to study slope failure by exerting friction force, as the inducing factor, on the model slope to simulate gravity (Aydan and Kawamoto 1992;Ning et al. 2020). ...
The numerical simulation-based strength reduction method has frequently been applied to analyze slope stability, showing that slope failure characteristics caused by the decrease in slope soil strength represent potential failure characteristics. This study aimed to develop a model test method for simulating the decrease in slope soil strength and applied this method to an excavation slope. A model material, composed of a high-strength substrate and a softening solution, which showed progressively decreasing strength, was developed. Then, a model slope constructed from the substrate was immersed in the softening solution to simulate the decrease in slope strength. Finally, an excavation slope was used to test the practical applicability of the developed method. The test results of the model slope indicate that the developed method enables the observation of the complete failure process caused by the decrease in slope strength, with a circular slip surface forming at 62 min 2 s of softening time; the location of the slip surface and the critical cohesion causing the slope failure generally agree with those from three limit equilibrium methods. The model test results of the excavation slope show that slope failure initiates near the toe at 53 min 36 s of softening time, followed by a series of retrogressive sliding failures that quickly occur; the location of the slip surface and the critical cohesion generally agree with the published information of the natural excavation slope.
... In the case of slope instability, an interesting solution is the installation of wooden reinforcement structures. They can be paired with live plants to increase the stabilizing effect through the root system ( Sonnenberg et al., 2012 ). However, on steep slopes, agricultural terraces are still the optimal solutions as they include a wide range of ecosystem services ( Xiong et al., 2018 ). ...
Viticulture in Argentina is an important socioeconomic sector, reflected in a significant wine market and tourism. However, climate change and related extreme events are serious concerns. The main issues are heatwaves, hailstorms, and heavy rainfall, resulting in damage to vineyards. While climate change impacts have already been discussed for regions such as the Mediterranean, the literature lacks an up-to-date overview of Argentine viticulture and potential mitigation solutions. In a country culturally and economically connected to the world of wine, it is strategic to bridge this gap to be prepared for a climatically adverse future. This perspective paper presents an overview of Argentine viticulture and its relationship to climate change. We focus on the Mendoza region, one of the most productive areas and home to cultural landscapes where internationally recognized wines are produced. Climate change is already occurring, a fact we observed by analyzing data from the past decades. We discussed how heatwaves in the lowlands drive farmers to move to the Andes slopes looking for more favorable conditions. But new threats arise, such as extreme rainfall. Due to surface hydrological processes, they can cause land degradation and compromise vineyards. We investigate these phenomena in detail, highlighting how they represent a growing challenge that must be addressed for the sustainable development of future viticulture in the area. Therefore, we propose mitigation strategies for more resilient production, drawing inspiration from the Sustainable Development Goals and suggesting a framework that can be extended to broader contexts worldwide.
... Linear variable displacement transducers (LVDTs) (or potentiometers) and extensometers are examples of contact techniques (Wartman 1999;Khosravi et al. 2011;Sonnenberg et al. 2012;Lu et al. 2015). The principle of the contact method is to physically contact the surfaces of the landslide model to obtain data by using a single probe. ...
Physical modelling is a useful method to examine how landslides deform and fail at the laboratory scale. Reliable and accurate measurement systems are required for landslide model tests. This study comprehensively evaluates the performance of a multismartphone measurement (MSM) system for landslide model tests. Two slope models with different particle sizes were selected to assess the trueness and precision of the MSM system based on photogrammetry techniques under varied conditions, including different smartphone qualities and phone configurations. Benchmark data from a 3D laser scanner and preprinted markers were employed in the entire-point tests and marker-point tests, respectively. In addition, the MSM system’s application test for monitoring landslides is presented. The results show that the system can be applied to achieve both trueness and precision at the millimetre level and submillimetre level in the entire-point tests and marker-point tests, respectively. Best-practice settings of the MSM system based on assessment tests are suggested for landslide slope models. The deformation behaviour of the excavation-induced slope model in the application test was clearly illustrated through the marker-based MSM system.
... In the model roots, geometry is the key factor that affects slope stability. Branched roots, heart-shaped artificial roots and 3D root clusters showed better reinforcement performances in centrifuge slope models under water level changes, rainfall, and earthquakes, respectively (Sonnenberg et al., 2012;Leung et al., 2017;. The tensile forces in the interaction between roots and soils were monitored as the primary reinforcement in the mechanical response (Sonnenberg et al., 2012). ...
... Branched roots, heart-shaped artificial roots and 3D root clusters showed better reinforcement performances in centrifuge slope models under water level changes, rainfall, and earthquakes, respectively (Sonnenberg et al., 2012;Leung et al., 2017;. The tensile forces in the interaction between roots and soils were monitored as the primary reinforcement in the mechanical response (Sonnenberg et al., 2012). On the other hand, Ng et al. (2016b) focused on both the mechanical and hydrological effects of vegetation on a slope subjected to rainfall at 15g using a novel suction-controlled system, as shown in Fig. 26. ...
Landslides are serious geohazards that occur under a variety of climatic conditions and can cause many casualties and significant economic losses. Centrifuge modelling, as a representative type of physical modelling, provides a realistic simulation of the stress level in a small-scale model and has been applied over the last 50 years to develop a better understanding of landslides. With recent developments in this technology, the application of centrifuge modelling in landslide science has significantly increased. Here, we present an overview of physical models that can capture landslide processes during centrifuge modelling. This review focuses on (i) the experimental principles and considerations, (ii) landslide models subjected to various triggering factors, including centrifugal acceleration, rainfall, earthquakes, water level changes, thawing permafrost, excavation, external loading and miscellaneous conditions, and (iii) different methods for mitigating landslides modelled in centrifuge, such as the application of nails, piles, geotextiles, vegetation, etc. The behaviors of all the centrifuge models are discussed, with emphasis on the deformation and failure mechanisms and experimental techniques. Based on this review, we provide a best-practice methodology for preparing a centrifuge landslide test and propose further efforts in terms of the seven aspects of model materials, testing design and equipment, measurement methods, scaling laws, full-scale test applications, landslide early warning, and 3D modelling to better understand the complex behaviour of landslides.
... Sonnenberg et al. [175] investigated the influence of mechanical reinforcement on the slope failure mode. The technique shown in Figure 28(a) was adopted to model root effects. ...
As a result of climate change and increasing engineering activities, soil-related disasters such as slope failures and sandstorms have become more frequent worldwide. These disasters have caused not only loss of life, but also have led to serious economic losses as well as ecological and environmental damage. To sustain mankind, a new discipline, eco-geotechnics, has rapidly become established and developed in recent years. It integrates scientific knowledge from soil mechanics, rock mechanics, ecology, biology, and atmospheric science to develop cross-disciplinary theories and carry out experiments to tackle grand world challenges such as the effects of climate change. Through the development of eco-geotechnics, various eco-friendly technologies have been developed to mitigate sandstorms and to improve the performance of earthen structures such as embankments, slopes and landfill covers. This state-of-the-art review introduces and discusses the important advances in the field of eco-geotechnics, covering theoretical developments, laboratory testing, centrifuge modelling, field monitoring and engineering applications. Finally, the research gaps and future needs of eco-geotechnics are highlighted and discussed.
... However, this type of modeling was subject to drawbacks relating to the scale due to the gravitational field applied in the centrifuge and in terms of controlling the distribution of the natural roots on the slope. Due to the large number of variables that interfere in modeling slope stability with natural plants (root size, uneven plant growth along the slope, root inclination, among others), researchers such as Sonnenberg [17], Eab [18]; Liang and Knappett [19]; Liang [20]; used artificial roots to try to control these variables that occur when using natural roots. The results of the seepage and rainfall-induced slope failure models performed in a geotechnical centrifuge by Eab [18] indicate that root reinforcement improves slope stability, preventing cracks on the surface and reducing soil deformations. ...
The purpose of this study was to explore the influence of vegetation on the stability of clayey slopes. Physical models with varying layer depths reinforced with roots were performed in a geotechnical centrifuge. The soil reinforced with vegetation was simulated with a mixture of clay and fiberglass which present similar shear strength properties. Displacement vectors of the physical models are obtained using the Particle Image Velocimetry (PIV). The computed resultant displacements showed that the slip surface varied with respect the root depth. Additionally, numerical models of the tests in centrifuge were made using finite elements and Bishop's method. The results obtained also show that the deeper the roots, the deeper the sliding surface. The slip surface moves from a depth of the slope toe (slope without reinforcement) to a depth close to twice the height of the slope. Regarding the factor of safety, it varies from a value of 0.7 for slopes without vegetation to 1.19 for a root depth of three meters. Moreover, the factor of safety increases as root depth increases.
... The utilization of vegetation as a bioengineering method to enhance the stability of slopes and minimize surface erosion is well known (Cislaghi et Sonnenberg et al, 2012). While roots of herbaceous vegetation rarely cross potential shear planes, however, they increase soil cohesion in the top soil and create a surface-mat effect (Michael et al. 2020). ...
Direct shear tests conducted on soil samples reveal that soils with plant roots show an increase in cohesive factor but increase in frictional angle is insignificant. Displacement and shear strength graphs, however, indicate that soil with plant roots can withstand more shear stresses. Among the three plant species selected for the present study, Chimonobambusa sp. has the highest shear strength increment, ∆C = 5.0 KN/m ² followed by Cymbopogon sp., and Pseudosasa japonica with 4.5KN/m ² and 1.0KN/m ² shear strength increments respectively. An increase in shear strength is also observed in the reinforced soils with increase in number of roots of these plant species. Cymbopogon sp. has higher root density near the surface but decreases with increasing depth and absent at 320mm depth, Pseudosasa japonica has the lowest root density but penetrates deeper up to 530mm while Chimonobambusa sp . penetrates deepest at 700mm with lateral branches extending up to 650mm. Cymbopogon sp., and Pseudosasa japonica may be useful as a bioengineering tool to mitigate soil erosion while Chimonobambusa sp. to mitigate both erosion and shallow landslides.
... The hydraulic jack is used to application of vertical load on the center of this footing and the applied load magnitude was measured by utilizing Load cell. the LVDTS were utilized to measure settlement of the slope and the horizontal displacement [14] which their locations are showing in Figure.(1). ...
... The total suction of the meddle and bottom layers are decreased in quickly rate comparing with top layer. In this layers, the total suction decrease from (23, 21) kPa to (14,13)kPa respectively when increased vertical stress that applied on the slope crest from (0 to 306) kPa and then the suction remained constant until failure happen at vertical stress equal to (408) kPa. The soil suction varatin of these is appear in figure (5). ...
This research was conducted to detect the effect of static load, dynamic condition, and rainfall on slope stability. The studied parameters are: rainfall intensity, static load, frequency, soil suction variation, and the form of slope failure. A laboratory model was manufactured in the form of a box with dimensions of (2000 × 1000 × 1450) mm that slides on a rail installed on the ground and moved by a dynamically generated system and provided with a controlled rainfall system. To clarify the rainfall effect with dynamic conditions on the slope stability, the effect of rainfall intensities of (20, 30, and 40) mm/h were studied on a series of three model tests. Two stages of a rainfall (duration of each one = 1 h) have been applied to the soil sample. After each stage, the model was left for 24 h to allow the water infiltration process into the soil layers. Dynamic conditions were enjoined as (20) mm of one direction horizontal vibration displacement at frequencies of (0.5, 1.0, and 2.0) Hz. The time duration for each frequency value is (3) minutes. The acceleration during vibrations was measured through the test by an accelerometer that was placed on a shaking table and inside the soil. The main result shows that the rainfall and dynamic load have negatively affected the slope bearing capacity. It decreased from (408) kPa at the static test to (204, 127, and 102) kPa at the three rainfall tests, respectively. On the other hand, results also revealed that the soil suctions were decreased after the application of rainfall on the slope model.
... Often, numerical modelling of slope stability is compared with experimental results. In the case of seismic load, to establish the stability of a slope, geotechnical centrifuge can be used for rooted (Sonnenberg et al. 2010, Ng et al. 2016) and unrooted soil (Ling et al. 2009), as well as for slopes with root analogues (Sonnenberg et al. 2012, Eab et al. 2014, Liang et al. 2015. In Liang & Knappett (2017) the influence of slope height is observed for vegetated slopes with 3D root cluster analogue representing a tap-root system. ...
This PhD thesis presents an innovative experimental investigation on the mechanical response of sand to plant root growth.Root-soil interaction is investigated for two different root systems -- Maize and Chickpea -- and two different gradings of Hostun sand with two initial porosities.An original protocol is developed aiming to create samples with repetitive initial nominal properties and representative of the natural interaction.Two experimental campaigns were run on a series of samples with different sands and plants.A 4D (3D+time) analysis of the interaction is carried out by using x-ray Computed Tomography.For each sample, an average of 7 x-rays scans is performed, from the day of the seed sowing up to 7-days-old root system.An image processing technique has been developed and it is applied to the 3D images resulting from the reconstruction of the x-ray scans. Through this image processing, the root system is identified, together with the sand grains and the water present in the system. Finally, a four-phased volume representative of the soil-root system can be defined for each state of the observed samples.Besides, from the 3D greyscale images of the samples, measurements of the kinematics of the system are obtained through local and discrete approaches of image correlation.Local sand porosity and deformations resulting from the four-phased volumes and the image correlations are detailed for one sample of each root-sand configuration.Regarding the impact of the initial sand state on the root system development, the comparison of the different configurations shows, among other things, that the sand density plays a key role on the expansion of the root system, for both plant species.Concerning the sand response to the root growth, the strain tensor computed with image correlation shows that a root shears the soil while growing and the sheared zone is wider when the initial bulk density is lower.This work focuses also on the determination of the sand volumetric response to root growth in the sheared zone and its dependency on the soil density.Sand response is purely dilatant for denser initial states, while the looser sand exhibits a contractant behaviour far from the root surface. Such a response is obtained in the case of both maize and chickpea. Moreover, the contractant behaviour induced by the shearing away from the root is confirmed also for both sand granulometries in a looser state.
