In between November 2013 to 2017, more than 200 sinkholes were formed in the Armala area of Pokhara. The sinkholes were formed mostly in the paddy fields in the alluvial fan deposit. The sinkholes terrorised and displaced hundreds of local residents. [1] [2]
In 2013, about 30 sink holes were formed in both sides of Duhuni Khola. The holes had a diameter of about 10m and depth of about 7m. Locals reported flow of muddy silty water outlet at the Kali Khola about one week before the first sinkhole appeared in November 2013. The sinkholes were completely filled up later.
More than 150 sinkholes appeared between 2013 and 2014 in the same area. This time the sinkholes affected the agricultural farmland, collapse of cowsheds in a house of a local resident. The hole near the house was filled up by the owner.
Most of the sink holes were located on the western side of river. Some of the new sinkholes were the old sinkholes. A series of progressive sinkholes along a straight line were also identified. [3]
The sinkhole is composed of silty clay, sand, and gravel. The area has a layer of thick white silt in depth of 4 m to 20 m. A hidden cavity of 2.5 m wide was found at a depth of 7.5 m to 10 m. [4]
The scrap from nearby Kali Khola identified 0.05 m thick sand seam layer between the silty clay layers at a depth of 9 m from the ground surface, which was similar to the level of sinkhole cavity. At the outcrop of Kali khola, groundwater flowing out from the interface of sand and silty clay layers were observed. An internal erosion was found at both the side of a sand layer. The internal erosion was not taking place at that location if there was only the presence of silty clay in the subsurface of Armala. The seepage groundwater from the hillside to the mainstream was the main source of erosion.
The groundwater flow is believed to trigger the formation of sinkholes. The Armala area is speculated to be actively eroding since hundreds of years which has caused gradual dissolving of small parts of soluble soil. This created caverns. [5]
The geo-physical survey found that excessive use of natural resources and encroachment of water resources as the major cause of the caving. [1]
The area used to be an agriculture land for most part of its history. Recently, there was an abrupt development of infrastructures. Due the sink holes, approximately 70 households has high risk. [6]
A high potential of catastrophe is predicted in case of seismic event in the area. [3]
The earthquake of 2015, some muddy water was observed at the outlet of the Kali River indicating alteration of subsoil conditions in some ways. However, no new sinkholes were formed and the size of existing sinkholes did not change. [7]
The Disaster Prevention Department has prohibited paddy plantation in the area for five years to reduce water seepage. However, locals were allowed to cultivate vegetables which require less amount of water. It has been learnt that a study around five decades ago had also recommended not to establish any human settlement in the area. [1]
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging, but many soils need artificial drainage to improve production or to manage water supplies.
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials. Groundwater from aquifers can be extracted using a water well. Water from aquifers can be sustainably harvested through the use of qanats. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as vrtače and shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet. A cenote is a type of sinkhole that exposes groundwater underneath. Sink and stream sink are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock.
Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid. In soil mechanics, the term "liquefied" was first used by Allen Hazen in reference to the 1918 failure of the Calaveras Dam in California. He described the mechanism of flow liquefaction of the embankment dam as:
If the pressure of the water in the pores is great enough to carry all the load, it will have the effect of holding the particles apart and of producing a condition that is practically equivalent to that of quicksand... the initial movement of some part of the material might result in accumulating pressure, first on one point, and then on another, successively, as the early points of concentration were liquefied.
Pokhara is a metropolitan city in central Nepal, which serves as the capital of Gandaki Province. It is the second most populous city of Nepal after Kathmandu, with 599,504 inhabitants living in 120,594 households in 2021. It is the country's largest metropolitan city in terms of area. The city also serves as the headquarters of Kaski District. Pokhara is located 200 kilometres west of the capital, Kathmandu. The city is on the shore of Phewa Lake, and sits at an elevation of approximately 822m. The Annapurna Range, with three out of the ten highest peaks in the world—Dhaulagiri, Annapurna I and Manaslu—is within 15–35 mi (24–56 km) of the valley. The current mayor of Pokhara is Dhana Raj Acharya from CPN.
Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids and particles but soil may also contain organic solids and other matter. Along with rock mechanics, soil mechanics provides the theoretical basis for analysis in geotechnical engineering, a subdiscipline of civil engineering, and engineering geology, a subdiscipline of geology. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that are buried in soils. Example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems. Principles of soil mechanics are also used in related disciplines such as geophysical engineering, coastal engineering, agricultural engineering, hydrology and soil physics.
The Kali Gandaki Gorge or Andha Galchi is the gorge of the Kali Gandaki in the Himalayas in Nepal. By some sources, it may be one of the deepest gorges in the world.
Devil's Millhopper Geological State Park is a Florida state park located in the north-westernmost part of Gainesville, Florida, off County Road 232, also known as NW 53rd Avenue and Millhopper Road, northwest of the University of Florida.
Palpa District (Nepali: पाल्पा जिल्ला, a part of Lumbini Province, is one of the seventy-seven districts of Nepal, a landlocked country of South Asia. The district, with Tansen as its headquarters, covers an area of 1,373 km2 and has a population of 261,180.
A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock. Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples are the Dragon Hole and, in the Caribbean, the Great Blue Hole and Dean's Blue Hole.
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Internal erosion is the formation of voids within a soil caused by the removal of material by seepage. It is the second most common cause of failure in levees and one of the leading causes of failures in earth dams, responsible for about half of embankment dam failures.
A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site.
Soil nailing is a remedial construction measure to treat unstable natural soil slopes or unstable man-made (fill) slopes as a construction technique that allows the safe over-steepening of new or existing soil slopes. The technique involves the insertion of relatively slender reinforcing elements into the slope – often general purpose reinforcing bars (rebar) although proprietary solid or hollow-system bars are also available. Solid bars are usually installed into pre-drilled holes and then grouted into place using a separate grout line, whereas hollow bars may be drilled and grouted simultaneously by the use of a sacrificial drill bit and by pumping grout down the hollow bar as drilling progresses. Kinetic methods of firing relatively short bars into soil slopes have also been developed.
The Cheltenham Badlands are in Caledon, Ontario, on the southeast side of Olde Base Line Road, between Creditview and Chinguacousy Roads. The site occupies an area of approximately 0.4 square kilometers and features exposed and highly eroded Queenston shale. The Cheltenham Badlands are a significant educational site due to the readily visible geologic processes and the red colour and the unique topography of the exposed shale make this a popular tourist site. The site is a Provincial Earth Sciences Area of Natural and Scientific Interest (ANSI) since it is considered one of the best examples of "badlands topography" in Ontario.
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