scholarly journals GIS-based topographic reconstruction and geomechanical modelling of the Köfels Rock Slide

2020 ◽  
Author(s):  
Christian Zangerl ◽  
Annemarie Schneeberger ◽  
Georg Steiner ◽  
Martin Mergili
Keyword(s):  
Shear Strength ◽  
Groundwater Flow ◽  
Friction Angle ◽  
High Water ◽  
Strength Properties ◽  
Trigger Factor ◽  
Rock Slide ◽  
Low Friction ◽  
Volume Estimates ◽  
The Impact

Abstract. The Köfels Rock Slide in the Ötztal Valley (Tyrol, Austria) represents the largest known extremely rapid landslide in metamorphic rock masses in the Alps. Although many hypotheses for the trigger were discussed in the past, until now no scientifically proven trigger factor has been identified. This study provides new data about the i) pre-failure and failure topography, ii) failure volume and porosity of the sliding mass, and iii) shear strength properties of the gneissic rock mass obtained by back-calculations. Geographic information system methods were used to reconstruct the slope topographies before, during and after the event. Comparing the resulting digital terrain models leads to volume estimates of the failure and deposition masses of 3.1 km3 and 4.0 km3, respectively and a sliding mass porosity of 26 %. For the back-calculations the 2D discrete element method was applied to determine the shear strength properties of the reconstructed basal shear zone. Results indicated that under no groundwater flow conditions, a very low friction angle below 24° is required to promote failure, whilst, with groundwater flow, the critical value increase to 28°. Such a low friction angle is unexpected from a rock mechanical perspective for this strong rock and groundwater flow, even if high water pressures are assumed, may not be able to trigger this rock slide. Additional conditioning and triggering factors should be identified by further studies, for example focussing on the impact of dynamic loading.

scholarly journals Geographic-information-system-based topographic reconstruction and geomechanical modelling of the Köfels rockslide

2021 ◽  
Vol 21 (8) ◽  
pp. 2461-2483
Author(s):  
Christian Zangerl ◽  
Annemarie Schneeberger ◽  
Georg Steiner ◽  
Martin Mergili
Keyword(s):  
Information System ◽  
Shear Strength ◽  
Rock Mass ◽  
Groundwater Flow ◽  
Shear Zone ◽  
Failure Process ◽  
Friction Angle ◽  
Strength Properties ◽  
Low Friction ◽  
Basal Shear

Abstract. The Köfels rockslide in the Ötztal Valley (Tyrol, Austria) represents the largest known extremely rapid landslide in metamorphic rock masses in the Alps. Although many hypotheses for the trigger were discussed in the past, until now no scientifically proven trigger factor has been identified. This study provides new data about the (i) pre-failure and failure topography, (ii) failure volume and porosity of the sliding mass, and (iii) numerical models on initial deformation and failure mechanism, as well as shear strength properties of the basal shear zone obtained by back-calculations. Geographic information system (GIS) methods were used to reconstruct the slope topographies before, during and after the event. Comparing the resulting digital terrain models leads to volume estimates of the failure and deposition masses of 3100 and 4000 million m3, respectively, and a sliding mass porosity of 26 %. For the 2D numerical investigation the distinct element method was applied to study the geomechanical characteristics of the initial failure process (i.e. model runs without a basal shear zone) and to determine the shear strength properties of the reconstructed basal shear zone. Based on numerous model runs by varying the block and joint input parameters, the failure process of the rock slope could be plausibly reconstructed; however, the exact geometry of the rockslide, especially in view of thickness, could not be fully reproduced. Our results suggest that both failure of rock blocks and shearing along dipping joints moderately to the east were responsible for the formation or the rockslide. The progressive failure process may have taken place by fracturing and loosening of the rock mass, advancing from shallow to deep-seated zones, especially by the development of internal shear zones, as well as localized domains of increased block failure. The simulations further highlighted the importance of considering the dominant structural features of the rock mass. Considering back-calculations of the strength properties, i.e. the friction angle of the basal shear zone, the results indicated that under no groundwater flow conditions, an exceptionally low friction angle of 21 to 24∘ or below is required to promote failure, depending on how much internal shearing of the sliding mass is allowed. Model runs considering groundwater flow resulted in approximately 6∘ higher back-calculated critical friction angles ranging from 27 to 30∘. Such low friction angles of the basal failure zone are unexpected from a rock mechanical perspective for this strong rock, and groundwater flow, even if high water pressures are assumed, may not be able to trigger this rockslide. In addition, the rock mass properties needed to induce failure in the model runs if no basal shear zone was implemented are significantly lower than those which would be obtained by classical rock mechanical considerations. Additional conditioning and triggering factors such as the impact of earthquakes acting as precursors for progressive rock mass weakening may have been involved in causing this gigantic rockslide.

scholarly journals Determining the Shear Strength and Permeability of Soils for Engineering of New Paddy Field Construction in a Hilly Mountainous Region of Southwestern China

2020 ◽  
Vol 17 (5) ◽  
pp. 1555
Author(s):  
Zhen Han ◽  
Jiangwen Li ◽  
Pengfei Gao ◽  
Bangwei Huang ◽  
Jiupai Ni ◽  
...  
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Engineering Design ◽  
Soil Water ◽  
Soil Water Content ◽  
Paddy Field ◽  
Friction Angle ◽  
Strength Properties ◽  
Mountainous Region

As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. New paddy field construction can give full play to the production and ecological functions of paddy field and can adjust the development structure of the agricultural industry effectively. The soil properties of shear strength and permeability, which provide a theoretical basis for engineering design, construction, and post-operation, are important indexes in the site selection of new paddy field. The shear strength and permeability properties of soils from different land use types (vegetable field, gentle slope dryland, corn field, grapery, and abandoned dryland) for engineering new paddy field construction were investigated in this study. The results showed that the soil water content had a significant effect on the soil shear strength, internal friction angle, and cohesion. The total pressure required for soil destruction decreased with increasing water content under the same vertical pressure, resulting in easier destruction of soils. The internal friction angle decreased with increasing soil water content, and the soil cohesion first increased and then decreased with increasing soil water content. Considering that paddy fields were flooded for a long time, the soil strength properties had certain water sensitivity. Effective measures must be taken to reduce the change in soil water content, so as to ensure the stability of the embankment foundation, roadside ditch foundation, and cutting slope. In addition, the influence of changing soil water content on the strength properties of paddy soils should be fully considered in engineering design and construction, and the soil bulk density at the plough pan should reach at least 1.5 g cm−3 or more to ensure better water retention and the anti-seepage function of paddy field. The study can provide construction technology for engineering new paddy field construction in a hilly mountainous region of southwestern China.

scholarly journals Shape or friction? Which of these characteristics drives the shear strength in granular systems?

2021 ◽  
Vol 249 ◽  
pp. 06008
Author(s):  
Theechalit Binaree ◽  
Emilien Azéma ◽  
Nicolas Estrada ◽  
Mathieu Renouf ◽  
Itthichai Preechawuttipong
Keyword(s):  
Shear Strength ◽  
Sliding Friction ◽  
Strength Properties ◽  
Contact Dynamics ◽  
Granular Systems ◽  
Combined Effects ◽  
Low Friction ◽  
Systematic Analysis ◽  
Dynamics Simulations ◽  
Two Parameters

The shape of the particles and local friction, separately, are known to strongly affect the macroscopic properties of an assembly of grains. But the combined effects of these two parameters still remain poorly described. By means of extensive two dimensional contact dynamics simulations, we perform a systematic analysis of the interplay between friction and shape on strength properties of granular systems. The shape of the particles is varied from disks to triangles, while the friction is varied from 0 to 0.7. We find that the macroscopic friction first increases with angularity, but it may decline (for low friction values), saturate (for intermediates friction values), or continue to increase (for large friction values) for the most angular shapes. In other words, the effect of the particle’s angularity on the shear strength depends on the level of sliding friction. In contrast, the effect of local friction on the shear strength does not depend on the specific properties of shape. The results presented here highlight the subtle coupling existing between shape and friction effects.

scholarly journals Leaching Impact on Compressibility and Shear Strength of Undisturbed and Cement-treated Champlain Sea Clay

2021 ◽  
Author(s):  
Mohammad Afroz
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Experimental Results ◽  
Salinity Level ◽  
Compression Tests ◽  
Treated Sample ◽  
Salinity Levels ◽  
Geotechnical Tests ◽  
The Impact

This research investigated the impact of leaching on the compressibility and shear strength properties of undisturbed and cement-treated Champlain Sea clay. A total of five undisturbed clay samples were leached with distilled water in the laboratory to reduce the salinity from initial values ranging from 9.5 to 15 g/L to the salinity values of 2.75, 1.45, 1.03, 0.55, and 0.35 g/L. A series of geotechnical tests were conducted on these samples at different salinity levels, including constant rate of strain consolidation tests, consolidated isotropic undrained triaxial compression tests, and vane shear tests. The experimental results showed that leaching leads to an increase in the compressibility and a reduction in shear strength of undisturbed Champlain Sea clay. The experimental results revealed that cement, mixed at a dosage of 50 kg/m3 , can significantly decrease the compressibility and increase the shear strength of Champlain Sea clay. A leached cement-treated sample exhibits a relatively higher compressibility than that of unleached cementtreated one. An increase in compressibility was also observed as salinity declines for the cementtreated samples. Moreover, a cement-treated sample at a lower salinity level displays slightly a higher shear strength compared to that of a cement-treated sample at the original salinity level.

scholarly journals Characterization of the Undrained Shear Strength of Expansive Soils of High Water Content

2018 ◽  
Vol 206 ◽  
pp. 01002
Author(s):  
Zheng Su ◽  
Daokun Qi ◽  
Xinju Guo ◽  
Xiaojuan Xi ◽  
Liang Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Friction Angle ◽  
High Water ◽  
Ease Of Use ◽  
Triaxial Tests ◽  
High Water Content

In recent years, engineering constructions increase rapidly in western and central areas of China, where expansive soil widely distributes. Since expansive soil is sensitive to water content, the characterization of its shear strength should be carefully conducted. For simplicity and ease of use, the Mohr-Coulomb criterion is often adopted to describe the shear strength of expansive soil. In this paper, the physical meaning of the cohesion and frictional strength of expansive soil are explained, and the variations of the strength parameters with water content are investigated. By fitting to the experimental results from direct shear test and triaxial tests, the changing characteristics of cohesion and friction angle with water content are obtained.

Study on the Shear Strength Properties of the Silt in Hangzhou, China

2013 ◽  
Vol 405-408 ◽  
pp. 349-352
Author(s):  
Zhen Ying Zhang ◽  
Da Zhi Wu ◽  
Cha Wang
Keyword(s):  
Shear Strength ◽  
Soil Mechanics ◽  
Friction Angle ◽  
Strength Properties ◽  
Soil Samples ◽  
Uniformity Coefficient ◽  
Cohesion Force ◽  
Natural Density ◽  
Hardening Curve ◽  
The Relationship

To investigate the shear strength properties of the silt, three soil samples are collected from Xiasha zone, Hangzhou, Zhejiang Province, China. The geotechnical engineering parameters of the silt soil are measured in the soil mechanics laboratory. Tests results show that the uniformity coefficient of the silt is 13.6, the natural density is 1.96t/m3, the moisture content is 17.0%, the plasticity index is 9.4, the cohesion force varies from 20.8 to 28.3kPa, and the internal friction angle varies from 12.3 to 31.8degree. Finally, the properties of the shear strength are studied, and find that the relationship between the shear stress and the shear strain is conformity with the strain hardening curve, and the relationship between the shear strength and the vertical pressure applied on the soil samples is linear, and agrees with the Coulombs law.

Numerical Simulation on the Influence of the Groundwater Flow Field during Tunnelling

2012 ◽  
Vol 594-597 ◽  
pp. 1230-1233 ◽  
Author(s):  
Xiao Bing Kang ◽  
Xie Wen Hu ◽  
Huai Qian Xie
Keyword(s):  
Numerical Simulation ◽  
Groundwater Flow ◽  
Water Pressure ◽  
High Water ◽  
Tunnel Construction ◽  
Groundwater Environment ◽  
Western Development ◽  
Geological Conditions ◽  
Sphere Of Influence ◽  
The Impact

With the vigorous development of China's economic construction, especially since the western development, needs of traffic tunnel construction are increasing, a large number of tunnels will be built in the mountainous with deeply buried and high water pressure, it is an urgent problem about research on the groundwater environment and the ecological environment in the tunnel site area causes of tunnel construction. The Songpan County Mounigou tunnel located in the high altitude alpine region, regional and environmental geological conditions are complicated, the strata in the tunnel site area is aquifer, and developed faults fractures and fissures, tunnelling will lead to groundwater dewatering and cause the deterioration of the groundwater environment, Then great collapse, burst mud and water gushing will occur during the tunnel construction due to the enrichment of groundwater in tunnel site. Take a research on numerical simulation of groundwater flow in the tunnel site area, the tunnel excavation will form a larger catchment corridor, the impact is bound to the tunnel site hydrogeological conditions in the sphere of influence may appear to lower the groundwater level, seisensui drawdown or part of the dry, provide the basis for tunnel construction.

The main influencing factors of soil mechanical characteristics of the gravity erosion environment in the dry-hot valley of Jinsha river

2018 ◽  
Vol 16 (1) ◽  
pp. 796-809 ◽  
Author(s):  
Yangyi Zhao ◽  
Xu Duan ◽  
Jiaojiao Han ◽  
Kun Yang ◽  
Yang Xue
Keyword(s):  
Shear Strength ◽  
Soil Erosion ◽  
Root System ◽  
Mechanical Characteristics ◽  
Plant Root ◽  
Friction Angle ◽  
Plant Root System ◽  
The Impact ◽  
Erosion Environment ◽  
Mass Erosion

AbstractThe dry-hot valley region counts as one of the most eco-sensitive zones in China, the issue of soil erosion is critical in regional ecological environment, soil mechanical property is one of the primary factors confining the occurrence of erosion, and it is attached crucial significance to in ascertaining the characteristics and principal factors of soil mechanics, and how to prevent and control soil erosion in arid red soil area of dry-hot valley. Through monitoring field location and directly shearing, the soil mechanical characteristics and the primary influencing factors of the mass erosion environment in the basin were ascertained. As the result indicates: (1) The soil moisture content, cohesion and internal friction angle are evidently correlated with each other abiding by power function, the relationship among soil cohesion, internal friction angle and volume moisture content goes as:$$\begin{array}{} \displaystyle c=80.107e^{-5.451\frac{{\it\omega}}{1.64\,+\,{\it\omega}}},\phi=65.646{\rm e}^{-3.325\frac{\omega}{1.64\,+\,\omega}}; \end{array}$$(2) The soil being large in pore radius vary in number and distribution evidently with structure and destruction degree (P<0.05). Soil aggregation was also significantly different (P<0.05), with the increasing of structural failure rate, the shear strength of soil decreased, and the probability of damage was increased as the external load increaseing. (3) The disintegration of soil can be effectively decelerated, and anti-disintegration ability of soil can be enhanced by the root system. The impact exerted by plant root system on shear strength of soil decreased as soil got deeper, more than a certain depth can be ignored; the impact exerted by plant root system on small-scale gravitational erosion was particularly evident, whereas the impact exerted by large-scale mass erosion was comparatively small. The ability of plant roots to optimize soil resistance was primarily through the roots shorter than 2 mm, the effective fibrous roots in the soil of the Leucaena Benth and the Dodonaea angustifolia were comparatively small, and the root of the herbaceous plants was comparatively large.

scholarly journals Analisis Kestabilan Lereng Berdasarkan Kekuatan Geser Massa Batuan Terhadap Perubahan Kandungan Air Pada Tambang Batubara Di Area Blok Menyango

PROMINE ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 71-77
Author(s):  
Novandri Kusuma Wardana
Keyword(s):  
Shear Strength ◽  
Natural Condition ◽  
Shear Failure ◽  
Friction Angle ◽  
Direct Shear ◽  
Test Results ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Wet Condition ◽  
The Impact

Mining activities is commonly to work with the problem of stability of rock mass, then befordesaining mine’s slope should know rock shear strength parameters, such as cohesion (c) andinternal friction angle value ( . Beside those parameters, also needed to know the impact ofwater content to the rocks. The water content will effect rock’s shear strength, proof by the rockcondition which is ductile when it is dry and soft when it is wet. Based on test results was doneusing sandstone with laboratory scale of direct shear test were analyzed using mohr – coulomband patton criteria (1966). It is known that the cohesion (c) of sandstone decreased from 510,35kPa at natural condition down to 133,75 kPa at wet condition. The internal friction angle ( ) alsodecreased from 54,56° at natural condition down to 48,45° at wet condition. The reduction of theshear strength is caused by fragments and clay minerals characteristics which are so reactiveand very easy to absorb water so that the cohesion of the sandstone reduce the active normalstress so that working the shear stress required to cause the shear failure becomeweaker. From the results, it is also known that the shear surface roughness had a lot ofinfluence on the shear strength the normal stresses applied on the direct shear tests werevery low under 20% of UCS.

scholarly journals Reinforcing Effect of Polypropylene Waste Strips on Compacted Lateritic Soils

2020 ◽  
Vol 12 (22) ◽  
pp. 9572
Author(s):  
Régis Marçal ◽  
Paulo César Lodi ◽  
Natália de Souza Correia ◽  
Heraldo Luiz Giacheti ◽  
Roger Augusto Rodrigues ◽  
...  
Keyword(s):  
Low Cost ◽  
Friction Angle ◽  
Strength Properties ◽  
Clayey Sand ◽  
Lateritic Soils ◽  
Direct Shear Tests ◽  
Apparent Cohesion ◽  
Fiber Reinforcements ◽  
Definition Of ◽  
The Impact

This study evaluated the strength properties of compacted lateritic soils reinforced with polypropylene (PP) waste strips cut from recycled plastic packing with the goal of promoting sustainability through using local materials for engineering work and reusing waste materials as low-cost reinforcements. Waste PP strips with widths of 15 mm and different lengths were uniformly mixed with clayey sand (SC) and clay (CL) soils with the goal of using these materials as low-cost fiber reinforcements. The impact of different PP strip contents (0.25% to 2.0%) and lengths (10, 15, 20, and 30 mm) on the unconfined compressive strength (UCS) of the soils revealed an optimum combination of PP strip content and length. Statistical analysis showed that PP strip content has a greater effect than the PP strip length on the UCS for both soils. Results led to the definition of an empirical equation to estimate the UCS of strip-reinforced soils. The results from direct shear tests indicate that the SC soil showed an increase in both apparent cohesion and friction angle after reinforcement, while the CL soil only showed an increase in friction angle after reinforcement. California bearing ratio (CBR) tests indicate that the SC soil experienced a 70% increase in CBR after reinforcement, while the CBR of the CL soil was not affected by strip inclusion.

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