Viewed from above, it has the shape of an open fan, the apex being at the valley mouth. It commonly marks a visible change in lithology or color. A common use is to control channelized debris flow frequency and volume. Check dams are expensive to construct and are therefore usually only built where important installations, such as a camp or unique spawning area, lie downslope.
The designation captures both the type of material that failed and the type of movement that the failed material exhibited. Material types are broadly categorized as either rock or soil, or a combination of the two for complex movements.
TYPES OF LANDSLIDES The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. 5 Landslides Landslide is a general term for a wide variety of down slope movements of earth materials that result in the perceptible downward and outward movement of soil, rock, and vegetation under. Landslide is a general term for a wide variety of down slope movements of earth materials that result in the perceptible downward and outward movement of soil, rock and .
Rock refers to hard or firm bedrock that was intact and in place prior to slope movement. Soil, either residual or transported material, is used in the engineering sense to mean unconsolidated particles or poorly cemented rock or aggregates.
Soil is distinguished further on the basis of texture as debris coarse fragments or earth fine fragments. The distinction between rock and soil, and the further distinction between debris and earth is most often based on interpretation of geomorphic characteristics within landslide deposits, but can also be inferred from geologic characteristics of the parent material described on maps or observed in the field.
Landslide movements are interpreted from the geomorphic expression of the landslide deposit and source area, and are categorized as falls, topples, spreads, slides, or flows. Falls are masses of soil or rock that dislodge from steep slopes and free-fall, bounce, or roll downslope.
Topples move by the forward pivoting of a mass around an axis below the displaced mass. Lateral spreads, commonly induced by liquefaction of material in an earthquake, move by horizontal extension and shear or tensile fractures.
Slides displace masses of material along one or more discrete planes. In rotational sliding the slide plane is curved and the mass rotates backwards around an axis parallel to the slope; in translational sliding the failure surface is more or less planar and the mass moves parallel to the ground surface.
Flows mobilize as a deforming, viscous mass without a discrete failure plane. More than one form of movement may occur during a failure, in which case the movement is classified as complexif movements occur sequentially and composite if they do not. A landslide involving bedrock in which the rock that moves remains largely intact for at least a portion of the movement.
Rock slides can range in size from small and thin to very large and thick, and are subject to a wide range of triggering mechanisms. Rock slides commonly occur on relatively steep slopes in competent rocks.
Movement of an intact rock mass along a curved slide plane leads to a steep, arcuate headscarp at the upper boundary of the slide. Immediately below the headscarp is a block that is commonly rotated so that it is less steep than the surrounding hill slopes.
Below the bench, the slide mass may be intact with a similar gradient to the surrounding slopes or may have additional scarps and benches.
The lower parts of the slopes may bulge outward and be steeper that the surrounding slopes. A specific type of Soil Flow landslide where the majority of the soil materials are fine-grained silt and clay and cohesive. The material strength is low through much of the slide mass, and movement occurs on many discontinuous shear surfaces throughout the landslide mass.
The lower parts of an earth flow usually bulge outward and are steeper than adjacent slopes.
Earth flows commonly occur on moderately steep slopes. They are characteristically slow moving, in the millimeters or centimeters per day range, and may continue to move for a period of days to weeks after initiating.
A slide of coarse-grained soil, most common in unconsolidated sandy or gravelly units, but also are common in residual soils that form from in-place weathering of relatively hard rock.
Owing to the granular constituents, overall strength of the debris slide mass generally is higher than that of earth flows, but there may be a very low strength zone at the base of the soil or within weathered bedrock.
Debris slides typically move initially as shallow intact slabs of soil and vegetation, but break up after a short distance into falls and flows. Movement of the slide mass as a shallow slab leads to a smooth, steep, commonly curved scar.
The debris is deposited at the base as a loose hummocky mass, although the deposit may be rapidly removed by erosion. Debris slides form steep, un-vegetated scars which are likely to remain un-vegetated for years.
Re-vegetated scars can be recognized by their steep slopes, and a shallow amphitheater morphology.
A single heavy rainstorm or series of storms may deliver enough rain to trigger debris slides. Individual debris slides may move at rates ranging from meters per day to meters per minute.
Debris slide scars are extremely steep and therefore are very sensitive to renewed disturbance.Landslides Glossary. types of soil that shrink or swell as the moisture content decreases or increases. Structures built on these soils may experience shifting, cracking, and breaking damage as soils shrink and subside or expand.
a general term for a mass-movement landform and process characterized by a flowing mass of fine-grained. Soil and General Term Landslides Words | 5 Pages. LANDSLIDES Introduction The term ‘landslide’ includes all varieties of mass movements of hill slopes and can be defined as the downward and outward movement of slope forming materials composed of rocks, soils, artificial fills or combination of all these materials along surfaces of separation by falling, sliding and flowing, either.
The term landslide or, less frequently, landslip, Say there is a slope with silt and sand as its top soil and bedrock as its bottom soil. During an intense rainstorm, the bedrock will keep the rain trapped in the top soils of silt and sand.
In general, to predict landslides, one must assume that their occurrence is determined by certain. Landslide is a general term for a wide variety of down slope movements of earth materials that result in the perceptible downward and outward movement of soil, .
Landslide is a general term used to describe a variety of geologic processes involving the movement of fine-grained earth, coarse-grained debris, or rock down a slope under the influence of gravity.
This broad definition of downslope movements includes falling, toppling, sliding, spreading, and flowing. Landslide is a general term for a wide variety of down slope movements of earth materials that result in the perceptible downward and outward movement of soil, rock and vegetation under the influence if gravity.
The materials may move by falling, toppling, sliding, spreading, or flowing.