Seifert conjecture: Difference between revisions
en>ZéroBot m r2.7.1) (Robot: Adding fr:Conjecture de Seifert |
No edit summary |
||
Line 1: | Line 1: | ||
[[Image:Slopslump2.jpg|thumb|250px|Figure 1: Simple slope slip section]] | |||
The field of '''slope stability''' encompasses the analysis of static and dynamic stability of slopes of earth and rock-fill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock.<ref>[http://web.archive.org/web/20080528085404/http://www.usace.army.mil/publications/eng-manuals/em1110-2-1902/entire.pdf US Army Corps of Engineers Manual on Slope Stability]</ref> Slope stability investigation, analysis (including modeling), and design mitigation is typically completed by [[geologists]], [[engineering geologists]], or [[geotechnical engineer]]s. [[Geologists]] and [[engineering geologists]] can also use their knowledge of earth process and their ability to interpret surface [[geomorphology]] to determine relative slope stability based simply on site observations. | |||
As seen in Figure 1, earthen slopes can develop a cut-spherical weakness area. The probability of this happening can be calculated in advance using a simple 2-D circular analysis package.<ref>{{cite web |url=http://www.wise-uranium.org/cssth.html |title=Slope Stability Calculator |accessdate=2006-12-14 |work= }}</ref> A primary difficulty with analysis is locating the most-probable slip plane for any given situation.<ref>{{Citation|surname=Chugh|given=Ashok|author-link=|year=2002|title=A method for locating critical slip surfaces in slope stability analysis|journal=NRC Research Press|volume=|issue=|pages=|url=http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleInitialGet&journal=cgj&volume=39&calyLang=eng&articleFile=t02-042.pdf}}</ref> Many landslides have only been analyzed after the fact. More recently [[slope stability radar]] technology has been employed, particularly in the mining industry, to gather real time data and assist in pro-actively determining the likelihood of slope failure. | |||
== Real life failures == | |||
[[Image:Landslide Böschungsrutschung.jpg|thumb|250px|Figure 2: Real life landslide on a slope]] | |||
Real life failures in naturally deposited mixed soils are not necessarily circular, but prior to computers, it was far easier to analyse such a simplified geometry. Nevertheless, failures in 'pure' clay can be quite close to circular. Such slips often occur after a period of heavy rain, when the pore water pressure at the slip surface increases, reducing the effective [[normal stress]] and thus diminishing the restraining [[friction]] along the slip line. This is combined with increased soil weight due to the added groundwater. A 'shrinkage' crack (formed during prior dry weather) at the top of the slip may also fill with rain water, pushing the slip forward. At the other extreme, slab-shaped slips on hillsides can remove a layer of soil from the top of the underlying bedrock. Again, this is usually initiated by heavy rain, sometimes combined with increased loading from new buildings or removal of support at the toe (resulting from road widening or other construction work). Stability can thus be significantly improved by installing drainage paths to reduce the destabilising forces. Once the slip has occurred, however, a weakness along the slip circle remains, which may then recur at the next monsoon. | |||
Slope stability issues can be seen with almost any walk down a [[ravine]] in an urban setting. An example is shown in Figure 3, where a river is eroding the toe of a slope, and there is a swimming pool near the top of the slope. If the toe is eroded too far, or the swimming pool begins to leak, the forces driving a slope failure will exceed those resisting failure, and a [[landslide]] will develop, possibly quite suddenly. | |||
== Analysis methods == | |||
{{Main|Slope stability analysis}} | |||
[[Image:Riverslope.jpg|thumb|250px|Figure 3: Slope with eroding river and swimming pool]] | |||
[[File:Pett bish.gif|thumb|250px|Figure 4: Method of slices]] | |||
If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable. A [[factor of safety]] is calculated by dividing the forces resisting movement by the forces driving movement. In earthquake-prone areas, the analysis is typically run for static conditions and pseudo-static conditions, where the seismic forces from an earthquake are assumed to add static loads to the analysis. | |||
===Method of slices=== | |||
The '''method of slices''' is a method for analyzing the stability of a slope in two dimensions. The sliding mass above the failure surface is divided into a number of slices. The forces acting on each slice are obtained by considering the mechanical equilibrium for the slices. | |||
=== Bishop's method === | |||
The Modified (or Simplified) Bishop's Method <ref>{{cite doi|10.1680/geot.1955.5.1.7}}</ref> proposed by [[Alan W. Bishop]] of [[Imperial College Civil & Environmental Engineering|Imperial College]] is a method for calculating the stability of slopes. It is an extension of the Method of Slices. By making some simplifying assumptions, the problem becomes statically determinate and suitable for hand calculations: | |||
* forces on the sides of each slice are horizontal | |||
The method has been shown to produce factor of safety values within a few percent of the "correct" values. | |||
:<math>F=\frac{\sum [\frac{c'+((W/b)-u)\tan\phi'}{\psi}]}{\sum[(W/b)\sin\alpha]}</math> | |||
where | |||
:<math>\psi=\cos\alpha+\frac{\sin\alpha \tan\phi}{F}</math> | |||
:c' is the effective cohesion | |||
:<math>\phi'</math> is the effective internal [[angle of internal friction]] | |||
:b is the width of each slice, assuming that all slices have the same width | |||
:W is the weight of each slice | |||
:u is the water pressure at the base of each slice | |||
=== Sarma method === | |||
{{Main|Sarma method}} | |||
The '''[[Sarma method]]''',<ref>{{cite doi|10.1680/geot.1975.25.4.743}}</ref> proposed by [[Sarada K. Sarma]] of [[Imperial College Civil & Environmental Engineering|Imperial College]] is a [[Slope stability analysis#Limit equilibrium analysis|Limit equilibrium]] technique used to assess the stability of slopes under seismic conditions. It may also be used for static conditions if the value of the horizontal load is taken as zero. The method can analyse a wide range of slope failures as it may accommodate a multi-wedge failure mechanism and therefore it is not restricted to planar or circular failure surfaces. It may provide information about the factor of safety or about the critical acceleration required to cause collapse. | |||
=== Lorimer's method === | |||
'''Lorimer's Method''' is a technique for evaluating slope stability in cohesive soils. It differs from Bishop's Method in that it uses a [[clothoid]] slip surface in place of a circle. This mode of failure was determined experimentally to account for effects of particle cementation. | |||
The method was developed in the 1930s by [[Gerhardt Lorimer]] (Dec 20, 1894-Oct 19, 1961), a student of geotechnical pioneer [[Karl von Terzaghi]]. | |||
== See also == | |||
* [[Discontinuity layout optimization]] | |||
* [[Mass wasting]] | |||
* [[Mohr-Coulomb theory]] | |||
* [[Slope stability analysis]] | |||
* [[Slope stability radar]] | |||
== Notes == | |||
<references/> | |||
== References == | |||
* Coduto, Donald P. (1998). ''Geotechnical Engineering: Principles and Practices.'' Prentice-Hall. ISBN 0-13-576380-0 | |||
==External links== | |||
* {{Dmoz|Science/Technology/Civil_Engineering/Geotechnical/Software|Geotechnical Software}} | |||
{{Geotechnical engineering}} | |||
[[Category:Soil mechanics]] | |||
[[Category:Geology]] |
Revision as of 00:23, 9 August 2013
The field of slope stability encompasses the analysis of static and dynamic stability of slopes of earth and rock-fill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock.[1] Slope stability investigation, analysis (including modeling), and design mitigation is typically completed by geologists, engineering geologists, or geotechnical engineers. Geologists and engineering geologists can also use their knowledge of earth process and their ability to interpret surface geomorphology to determine relative slope stability based simply on site observations.
As seen in Figure 1, earthen slopes can develop a cut-spherical weakness area. The probability of this happening can be calculated in advance using a simple 2-D circular analysis package.[2] A primary difficulty with analysis is locating the most-probable slip plane for any given situation.[3] Many landslides have only been analyzed after the fact. More recently slope stability radar technology has been employed, particularly in the mining industry, to gather real time data and assist in pro-actively determining the likelihood of slope failure.
Real life failures
Real life failures in naturally deposited mixed soils are not necessarily circular, but prior to computers, it was far easier to analyse such a simplified geometry. Nevertheless, failures in 'pure' clay can be quite close to circular. Such slips often occur after a period of heavy rain, when the pore water pressure at the slip surface increases, reducing the effective normal stress and thus diminishing the restraining friction along the slip line. This is combined with increased soil weight due to the added groundwater. A 'shrinkage' crack (formed during prior dry weather) at the top of the slip may also fill with rain water, pushing the slip forward. At the other extreme, slab-shaped slips on hillsides can remove a layer of soil from the top of the underlying bedrock. Again, this is usually initiated by heavy rain, sometimes combined with increased loading from new buildings or removal of support at the toe (resulting from road widening or other construction work). Stability can thus be significantly improved by installing drainage paths to reduce the destabilising forces. Once the slip has occurred, however, a weakness along the slip circle remains, which may then recur at the next monsoon.
Slope stability issues can be seen with almost any walk down a ravine in an urban setting. An example is shown in Figure 3, where a river is eroding the toe of a slope, and there is a swimming pool near the top of the slope. If the toe is eroded too far, or the swimming pool begins to leak, the forces driving a slope failure will exceed those resisting failure, and a landslide will develop, possibly quite suddenly.
Analysis methods
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.
If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable. A factor of safety is calculated by dividing the forces resisting movement by the forces driving movement. In earthquake-prone areas, the analysis is typically run for static conditions and pseudo-static conditions, where the seismic forces from an earthquake are assumed to add static loads to the analysis.
Method of slices
The method of slices is a method for analyzing the stability of a slope in two dimensions. The sliding mass above the failure surface is divided into a number of slices. The forces acting on each slice are obtained by considering the mechanical equilibrium for the slices.
Bishop's method
The Modified (or Simplified) Bishop's Method [4] proposed by Alan W. Bishop of Imperial College is a method for calculating the stability of slopes. It is an extension of the Method of Slices. By making some simplifying assumptions, the problem becomes statically determinate and suitable for hand calculations:
- forces on the sides of each slice are horizontal
The method has been shown to produce factor of safety values within a few percent of the "correct" values.
where
- c' is the effective cohesion
- is the effective internal angle of internal friction
- b is the width of each slice, assuming that all slices have the same width
- W is the weight of each slice
- u is the water pressure at the base of each slice
Sarma method
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. The Sarma method,[5] proposed by Sarada K. Sarma of Imperial College is a Limit equilibrium technique used to assess the stability of slopes under seismic conditions. It may also be used for static conditions if the value of the horizontal load is taken as zero. The method can analyse a wide range of slope failures as it may accommodate a multi-wedge failure mechanism and therefore it is not restricted to planar or circular failure surfaces. It may provide information about the factor of safety or about the critical acceleration required to cause collapse.
Lorimer's method
Lorimer's Method is a technique for evaluating slope stability in cohesive soils. It differs from Bishop's Method in that it uses a clothoid slip surface in place of a circle. This mode of failure was determined experimentally to account for effects of particle cementation.
The method was developed in the 1930s by Gerhardt Lorimer (Dec 20, 1894-Oct 19, 1961), a student of geotechnical pioneer Karl von Terzaghi.
See also
- Discontinuity layout optimization
- Mass wasting
- Mohr-Coulomb theory
- Slope stability analysis
- Slope stability radar
Notes
- ↑ US Army Corps of Engineers Manual on Slope Stability
- ↑ Template:Cite web
- ↑ Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010 - ↑ Template:Cite doi
- ↑ Template:Cite doi
References
- Coduto, Donald P. (1998). Geotechnical Engineering: Principles and Practices. Prentice-Hall. ISBN 0-13-576380-0
External links
- 43 yr old Analyst Programmer Courtney from Strathroy, enjoys football, new launching property developers in singapore and compose music. that covered visiting Urnes Stave Church.