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 are the factors that affect slope stability?
Slope stability is ultimately determined by two factors: the angle of the slope and the strength of the materials on it. (1) Figure 7.1.1 Differences in the shear and normal components of the gravitational force on slopes with differing steepness.
How do you stabilize a sloped slope?
Slopes can be stabilized by adding a surface cover to the slope, excavating and changing (or regrading) the slope geometry, adding support structures to reinforce the slope or using drainage to control the groundwater in slope material. How do you increase the stability of a slope?
What are the causes of slope failure?
Although gravity acting on an over-steepened slope is the primary reason for a landslide, there are other contributing factors: erosion by rivers, glaciers, or ocean waves create oversteepened slopes. rock and soil slopes are weakened through saturation by snowmelt or heavy rains. What are the three types of slope failure?
What determines the strength of a rock on a slope?
[SE] 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 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 is the main force involved in the stability of slopes?
Slope Stability. The main force responsible for mass movement is gravity.
How can you improve the stability of slopes?
Improving stability of slopesSlope flattening reduces the weight of the mass tending to slide/collapse. ... Proving a berm beneath the toe of the slope enhances the resistance to movement. ... Drainage helps in reducing the seepage forces and thus enhances the stability of slopes.More items...•
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 two opposing forces in controlling slope stability?
Definition of Factor of Safety Slope stability is controlled by 2 main factors: the driving and the resisting forces.
What are the key factors that may trigger 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 ...
What are slope protection methods?
Slope protection approaches discussed below include erosion control blankets and turf reinforcement mats, which can also be used for ditch protection, surface roughening, slope drains, gabion structures, and cellular mats.
How can we minimize slope failures?
Below are some of the common methods used for slope failure mitigation and repair:Drainage. Contractors who know what they're doing will always draw up drainage plans to complement their slope repair plans. ... Terracing & Benching. ... Retaining Walls. ... Friction Piles. ... Sheet Piling. ... Rock Bolts. ... Shotcrete. ... Geo-grid.More items...•
How do you prevent erosion on a slope?
Techniques for steep slopes include wood retaining walls, interlocking concrete blocks, rock retaining walls, riprap (loose rock) areas, and terracing. If you choose wood, make sure the wood is treated with a wood preservative to prevent rotting.
What would help prevent the likelihood of a slope failing?
cohesion between grains may reduce the potential for slope failure. loose unconsolidated material is formed into a pile. adding weight, destroying cohesion between grains, and reducing friction.
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: ...
How is slope stability determined?
Slope stability is ultimately determined by two factors: the angle of the slope and the strength of the materials on it. In Figure 15.2 a block of rock situated on a rock slope is being pulled toward Earth’s centre (vertically down) by gravity. We can split the vertical gravitational force into two components relative to the slope: one pushing ...
Why are unconsolidated sediments stronger than dry sediments?
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.
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 15.3.
Why are sedimentary rocks weaker than sedimentary rocks?
Unconsolidated sediments are generally weaker than sedimentary rocks because they are not cemented and , in most cases, have not been significantly compressed by overlying materials.
What force pushes a block down a slope?
The shear force, which wants to push the block down the slope, has to overcome the strength of the connection between the block and the slope, which may be quite weak if the block has split away from the main body of rock, or may be very strong if the block is still a part of the rock.
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.
What is the strength of the relationship between a block and a slope called?
The strength of the relationship between the block and the slope is called the shear strength .
Why is dry sediment weak?
Saturated sediments tend to be the weakest of all because the water pushes the grains apart, decreasing friction between grains.
What are the strengths of sedimentary rocks?
Sedimentary rocks have variable strength. Dolostone and some limestone are strong, most sandstone and conglomerate are moderately strong, and some sandstone and all mudstones are quite weak. Fractures, metamorphic foliation (excluding gneissosity and banding), or bedding can significantly reduce the strength of rock.
Why are unconsolidated sediments stronger?
Unconsolidated sediments tend to be strongest when they are mois t because the small amounts of water at grain boundaries holds the grains together due to surface tension.
What causes rapid melting of snow?
Rapid melting can be caused by a dramatic increase in temperature (e.g., in spring or early summer), or by a volcanic eruption. Heavy rains are typically related to storms.
What is surface tension?
Surface tension is the tension at the surface of a fluid that allows the liquid to resist an external force. Liquids always tend to acquire the lowest surface area possible; this happens because molecules at the surface of the fluid are attracted to the molecules below the surface).
What happens if you pick up sediment with a shovel?
A cohesive sediment binds together strongly and if you picked it up with a shovel it would stick together in a lump (e.g., sand mixed with clay, clay). A sediment that is not very cohesive is weakly bound and would probably fall apart if you picked it up with a shovel (e.g., sand, silt).
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.
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.
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.
What force pushes a block down a slope?
The shear force, which wants to push the block down the slope, has to overcome the strength of the connection between the block and the slope, which may be quite weak if the block has split away from the main body of rock, or may be very strong if the block is still a part of the rock. This is the.
What causes rapid melting of snow?
Rapid melting can be caused by a dramatic increase in temperature (e.g., in spring or early summer) or by a volcanic eruption. Heavy rains are typically related to major storms.
Does shear force change quickly?
Shear force is primarily related to slope angle, and this does not change quickly. But shear strength can change quickly for a variety of reasons, and events that lead to a rapid reduction in shear strength are considered to be for mass wasting. An increase in water content is the most common mass-wasting trigger.
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 ...
Who developed the general limit equilibrium?
Formulation used in general limit equilibrium was developed by Fredlund at the University of Saskatchewan in the 1970s (Fredlund and Krahn 1977; Fredlund et al. 1981). This technique includes the key elements of all the other methods available in the slope stability analysis in Geostudio 2007.
Who introduced the first method of calculating the base normal force?
They are:-. i) Fellenius (1936) which introduced the first method. It is also known as the Ordinary or the Swedish method and used for a circular slip surface. ii) Bishop (1955) had advanced the first method by introducing a new relationship for the base normal force.
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 slope movement?
A slope movement (also referred as a landslide) can lead to severe issues including infrastructure damage or/and casualties. Slope stability depends on the capability of the soil mass to withstand its gravitational forces, the additional loads acting on the slope, as well as potential dynamic loads (such as that of an earthquake).
What are the two types of slopes?
Slopes are typically categorized in two types: natural and artificially-made slopes. Natural slopes are formed due to physical processes that include plate tectonics and weathering/erosion of rock masses that result in material deposition. Artificially-made slopes are established to facilitate infrastructure projects, ex., embankments, earth dams, road cuttings etc.
What is a fall in science?
Falls are downward movements that progress rapidly and may not be preceded by initial movements or warnings. They occur when a rocky mass is detached from a slope along a discontinuity plane that can be associated with fractures, joints or bedding ( Figure 1 ).
What are the causes of landslides?
The natural causes of landslides include: gravitational forces that tend to destabilize the ground, water saturation, erosion, dynamic loads (e.g., earthquakes), the sudden uplift of the aquifer level, volcanic eruptions and freeze-thaw weathering cycles.
