Factors affecting slope stability
- Strength of soil and rock.
- Type of soil and stratification.
- Discontinuities and planes of weakness.
- Groundwater table and seepage through the slope.
- External loading.
- Geometry of the slope.
What is the relationship between erosion and slope stability?
Erosion, driven by gravity, is the inevitable response to that uplift, and various types of erosion, including mass wasting, have created slopes in the uplifted regions. Slope stability is ultimately determined by two factors: the angle of the slope and the strength of the materials on it.
What is the most important factor that affects slope strength?
Apart from the type of material on a slope, the amount of water that the material contains is the most important factor controlling its strength. This is especially true for unconsolidated materials, like those shown in Figure 15.4, but it also applies to bodies of rock.
What is the relative stability of slope?
Relative stability of slopes as a function of the orientation of weaknesses (in this case bedding planes) relative to the slope orientations. Apart from the type of material on a slope, the amount of water that the material contains is the most important factor controlling its strength.
What is safety factor in slope stability analysis?
In other words, it is often known as the safety factor, Fs, the ratio of shear strength to shear stress. When the value of safety factor less than 1.0, it indicates that slope failure is expected. To perform the different method of slope stability analysis used by both programs.
What are three factors that decrease slope stability?
Weathered geology: Weak, weathered bedrock, jointed rock, or bedrock that dips parallel to the slope can decrease stability. Vegetation removal: Droughts, wildfires and humans can remove vegetation from the slope, decreasing stability. Freeze/thaw cycles: Water in rock joints or in soils can decrease slope stability.
What are the factors affecting slope?
In general terms the factors include climate, lithology, topography and vegetation. At a more site-specificlevel, rainfall fre- quency, intensity and duration, slope length and inclination, soil properties, ground cover, and soil-disturbing activities are also important.
What are the factors trigger the slope failure?
Factors that can trigger slope failure include hydrologic events (such as intense or prolonged rainfall, rapid snowmelt, progressive soil saturation, increase of water pressure within the slope), earthquakes (including aftershocks), internal erosion (piping), surface or toe erosion, artificial slope loading (for ...
How do you prevent slope instability?
To ensure slope stability in constructed soil slopes, one common method is to take soil core samples, determine the stratigraphic layout of the soils, and then cut benches into the weaker soil. Next, a more stable and uniform soil type can be placed overtop to promote slope stabilization.
What are the factors that affect soil stability?
Alternate Wetting and Drying.Factor # 1. Climate: ... Factor # 2. Organic Matter: ... Factor # 3. Adsorbed Cations: ... Factor # 4. Tillage: ... Factor # 5. Type of Vegetation: ... Factor # 6. Plant Roots: ... Factor # 8. Manurial Practices and Crop Rotation: ... Factor # 9. Alternate Wetting and Drying:
How do you determine the stability of a slope?
If the forces that resist the movement are greater than those driving the movement, the slope is considered stable. A factor of safety (FS) is calculated by dividing the resistance by the driving forces. A factor of safety greater than 1.00 suggests that the slope is stable.
What are the five 5 factors influencing slope stability?
Five factors influence slope stability of an embankment: 1) Shear strength of the soil; 2) Unit weight; 3) Embankment height; 4) Slope steepness; and 5) Pore pressure within the soil. Failure generally occurs in two ways.
What do you mean by slope stability?
Slope stability is the process of calculating and assessing how much stress a particular slope can manage before failing. Examples of common slopes include roads for commercial use, dams, excavated slopes, and soft rock trails in reservoirs, forests, and parks.
Which feature can strengthen slopes?
Plant roots add strength and cohesion to slope materials. They act like steel rebar reinforcements in concrete and increase the resistance of a slope to landsliding. Vegetation also adds weight to a slope. Water is almost always directly or indirectly involved with landslides, so its role is particularly important.
How does water affect slope stability?
The Role of Water Since water is heavier than air, this increases the weight of the soil. Weight is force, and force is stress divided by area, so the stress increases and this can lead to slope instability. Water has the ability to change the angle of repose (the slope angle which is the stable angle for the slope).
What are the three types of slope failures?
Types of slope failure in geotechnical engineeringRotational failure. When rotational failure occurs, the failed surface will begin to move outwards and downwards. ... Translational failure. ... Compound failure. ... Wedge failure.
What factors influence the development of slopes over time?
The mechanics and rates of slope movement are controlled by many factors: slope gradients, overburden depth, structural rock properties, water content and soil pore water pressure, and certain engineering properties of overburden and weathered rock, such as cohesion and coefficient of friction.
What causes different slope elements to develop?
Processes like weathering, mass wasting, erosion, and deposition play key role in fashioning a landscape. These processes consistently operate upon the surface and regularly create and modify slope forms.
What are the different types of slope failure?
Soil slope failures are generally of four types : Translational Failure. Rotational Failure....Rotational FailureFace failure or slope failure.Toe failure.Base failure.
What are the factors that affect the strength of rock explain?
Factors that influence the strength of a rock and how it will deform include temperature, confining pressure, rock type, and time. Stress is the force per unit area acting on a solid.
What is the most important factor in determining the strength of a rock?
Apart from the type of material on a slope, the amount of water that the material contains is the most important factor controlling its strength. This is especially true for unconsolidated materials, like those shown in Figure 15.4, but it also applies to bodies of rock. Granular sediments, like the sand at Point Grey, have lots of spaces between the grains. Those spaces may be completely dry (filled only with air); or moist (often meaning that some spaces are water filled, some grains have a film of water around them, and small amounts of water are present where grains are touching each other); or completely saturated (Figure 15.5). Unconsolidated sediments tend to be strongest when they are moist because the small amounts of water at the grain boundaries hold the grains together with surface tension. Dry sediments are held together only by the friction between grains, and if they are well sorted or well rounded, or both, that cohesion is weak. Saturated sediments tend to be the weakest of all because the large amount of water actually pushes the grains apart, reducing the mount friction between grains. This is especially true if the water is under pressure.
How are slopes created?
As already noted, slopes are created by uplift followed by erosion. In areas with relatively recent uplift (such as most of British Columbia and the western part of Alberta), slopes tend to be quite steep. This is especially true where glaciation has taken place because glaciers in mountainous terrain create steep-sided valleys. In areas without recent uplift (such as central Canada), slopes are less steep because hundreds of millions of years of erosion (including mass wasting) has made them that way. However, as we’ll see, some mass wasting can happen even on relatively gentle slopes.
How does metamorphic foliation affect rock strength?
Fractures, metamorphic foliation, or bedding can significantly reduce the strength of a body of rock, and in the context of mass wasting, this is most critical if the planes of weakness are parallel to the slope and least critical if they are perpendicular to the slope. This is illustrated in Figure 15.3. At locations A and B the bedding is nearly perpendicular to the slope and the situation is relatively stable. At location D the bedding is nearly parallel to the slope and the situation is quite unstable. At location C the bedding is nearly horizontal and the stability is intermediate between the other two extremes.
How does water affect rock?
Water will also reduce the strength of solid rock, especially if it has fractures, bedding planes, or clay-bearing zones. This effect is even more significant when the water is under pressure, which is why you’ll often see holes drilled into rocks on road cuts to relieve this pressure. One of the hypotheses advanced to explain the 1965 Hope Slide is that the very cold conditions that winter caused small springs in the lower part of the slope to freeze over, preventing water from flowing out. It is possible that water pressure gradually built up within the slope, weakening the rock mass to the extent that the shear strength was no longer greater than the shear force.
What caused debris flow in Riverside Drive?
Figure 15.6 The debris flow in the Riverside Drive area of North Vancouver in January, 2005 happened during a rainy period, but was likely triggered by excess runoff related to the roads at the top of this slope and by landscape features, including a pool, in the area surrounding the house visible here. [The Province, used with permission]
What is the process that weakens a rock?
One other process that can weaken a body of rock or sediment is shaking. The most obvious source of shaking is an earthquake, but shaking from highway traffic, construction, or mining will also do the job. Several deadly mass-wasting events (including snow avalanches) were trigged by the M7.8 earthquake in Nepal in April 2015.
Does water increase the shear force?
And finally, water can significantly increase the mass of the material on a slope, which increases the gravitational force pushing it down. A body of sediment that has 25% porosity and is saturated with water weighs approximately 13% more than it does when it is completely dry, so the gravitational shear force is also 13% higher. In the situation shown in Figure 15.2b, a 13% increase in the shear force could easily be enough to tip the balance between shear force and shear strength.
88 15.1 Factors That Control Slope Stability
Mass wasting happens because tectonic processes have created uplift. Erosion, driven by gravity, is the inevitable response to that uplift, and various types of erosion, including mass wasting, have created slopes in the uplifted regions.
Mass-Wasting Triggers
In the previous section, we talked about the shear force and the shear strength of materials on slopes, and about factors that can reduce the shear strength. Shear force is primarily related to slope angle, and this does not change quickly.
What factors control slope stability?
15.1 Factors That Control Slope Stability. Mass wasting happens because tectonic processes have created uplift. Erosion, driven by gravity, is the inevitable response to that uplift, and various types of erosion, including mass wasting, have created slopes in the uplifted regions. Slope stability is ultimately determined by two factors: ...
Why are slopes less steep?
In areas without recent uplift (such as central Canada), slopes are less steep because hundreds of millions of years of erosion (including mass wasting) has made them that way. However, as we’ll see, some mass wasting can happen even on relatively gentle slopes. The strength of the materials on slopes can vary widely.
How does water affect rock?
Water will also reduce the strength of solid rock, especially if it has fractures, bedding planes, or clay-bearing zones. This effect is even more significant when the water is under pressure, which is why you’ll often see holes drilled into rocks on road cuts to relieve this pressure. One of the hypotheses advanced to explain the 1965 Hope Slide is that the very cold conditions that winter caused small springs in the lower part of the slope to freeze over, preventing water from flowing out. It is possible that water pressure gradually built up within the slope, weakening the rock mass to the extent that the shear strength was no longer greater than the shear force.
What can reduce the strength of a body of rock?
Fractures, metamorphic foliation, or bedding can significantly reduce the strength of a body of rock, and in the context of mass wasting, this is most critical if the planes of weakness are parallel to the slope and least critical if they are perpendicular to the slope. This is illustrated in Figure 15.1.2.
How are slopes created?
As already noted, slopes are created by uplift followed by erosion. In areas with relatively recent uplift (such as most of British Columbia and the western part of Alberta), slopes tend to be quite steep. This is especially true where glaciation has taken place because glaciers in mountainous terrain create steep-sided valleys. In areas without recent uplift (such as central Canada), slopes are less steep because hundreds of millions of years of erosion (including mass wasting) has made them that way. However, as we’ll see, some mass wasting can happen even on relatively gentle slopes.
What is the most important factor in determining the strength of a rock?
Apart from the type of material on a slope, the amount of water that the material contains is the most important factor controlling its strength. This is especially true for unconsolidated materials, like those shown in Figure 15.1.3, but it also applies to bodies of rock. Granular sediments, like the sand at Point Grey, have lots of spaces between the grains. Those spaces may be completely dry (filled only with air); or moist (often meaning that some spaces are water filled, some grains have a film of water around them, and small amounts of water are present where grains are touching each other); or completely saturated (Figure 15.1.4). Unconsolidated sediments tend to be strongest when they are moist because the small amounts of water at the grain boundaries hold the grains together with surface tension. Dry sediments are held together only by the friction between grains, and if they are well sorted or well rounded, or both, that cohesion is weak. Saturated sediments tend to be the weakest of all because the large amount of water actually pushes the grains apart, reducing the mount friction between grains. This is especially true if the water is under pressure.
Why are dry sediments weak?
Saturated sediments tend to be the weakest of all because the large amount of water actually pushes the grains apart, reducing the mount friction between grains.
How to obtain the factor of safety equal to one for slope stability?
Firstly, change the drained friction angle (phi) but maintained the other soil parameters constant. Secondly , maintained drained friction angle and the other parameters constant but change the angle slope of the problems. Meanwhile for the undrained analysis the same analysis was carried out but in this case was to obtain the factor of safety equal to one; only the undrained shear strength was changed.
What software is used to calculate slope stability?
For this project, there were two computer softwares used for modeling the slope stability problems named Limitstate : Geo 2.0 and GeoStudio 2007. By using this new technology being developed, modelling and calculating the factor of safety and the adequacy factor of the soil have been made easier to be obtained.
What is discontinuity layout optimization?
In Limitstate:Geo 2.0, Discontinuity Layout Optimization is a solution engine to analyse the slope stability problems. This procedure was developed at University of Sheffield. Beside that this method can be used to identify critical transitional sliding block failure mechanism with no limitations.
What is the factor of safety in Geo 2.0?
For the case of changing the slope angles and the remaining material strength properties stay the same, the results was tabulated in table… .It shows that in Limitstate: Geo 2.0 the factor of safety close to one was 29.5°. Meanwhile, in Geostudio 2007 the slope angles obtained was one degree smaller than the Limitstate: Geo 2.0.
Which two scientists proposed an equation to be used to handle the interslice shear forces?
Morgenstern and Price proposed an equation to be used to handle the interslice shear forces. The equation is:
Why does a material move down a slope?
The material will move down-slope when the sheer stress is larger than the total forces holding the object on the slope. However, when the materials like soil, clay, sand, silts and etc, the shear stress will become higher than the cohesional forces which hold, the particles will flow down slope and separate.
What is a slope in physics?
1.1 Overview. A slope is a ground surface that inclines either may be natural or man-made. Each slope has its own soil characteristics and geometric features, in order to resist gravity or collapse. Soil mass will move slowly or suddenly without any signage downward and outward when slope failure occurred. Slides usually begin from hairline tension ...
