SLOPE STABILITY

           Key words  slope stability , causes, shearing strength

Introduction

Land  slides are the downward and outward  movements of  materials on the slope. The reason for this is the lack of required shear strength. The slope materials may be composed of natural rock and soil, artificial fills. Slides can occur in natural slopes as well as man- made structures and embankments.

Great care should be taken in the selection of good construction material and also suitable construction methods to avoid sliding of slopes.

Causes of slope failures

The causes of slope failures may be external or internal.

External: Steepening of the slopes, depositing of material along the edge of the slopes and earthquakes.

Internal: Decrease in shearing resistance due to excess pore water pressure, leaching of salts, softening and breakage of cementation bonds.

The other activities which may provoke land slides are: Rapid draw down, seepage of water, erosion, heavy rainfall, excavation at the toe of the slope, excavation at the head of the slope, blocking of the drainage.

Basic concepts of stability analysis

All sloping surfaces are subjected to shearing stresses .The shear available  should overcome the developed stresses. If the shearing stresses are more, then a surface of rupture will be formed at the verge of failure.

1. Finding the most severely stressed internal surface and the connected shearing stress along the surface   Finding the shearing strength along the surface

Instead of resorting to rigorous mathematical analysis, a reasonable shape of failure is assumed and then the stability of the soil above the assumed surface is analysed.

Rate of land movement

The movements associated with land slides can be grouped under four heads.

-  Creep, pre-failure movements, movements during slides, post failure movements.

Creep may range from 1 to  few millimeters per year. Heavily over consolidated clays experience post failure movements, the speed of movements ranging from 0 to 6 m per year.

Importance of the Factor of Safety on slope stability analysis.

It is a measure of limiting the stress or strain so as to ensure the safety of the structure. As such, the working stress in any earth structure is much less than the shear strength of the soil.

The Factor of Safety may be defined as the ratio of shearing resistance available (τf ) along a slip surface to the total mobilized or developed shearing stress.( τ ).

F= τf / τ

Both cohesion and friction contribute to the shearing strength

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Kuttan Nair forgot his keys ( a micro storey)

 

       Kuttan Nair 

                

Kuttan Nair was returning from his daughter’s house. The village road was almost empty.  The sun was  approaching the western horizon. A group of cranes flew  over the green fields. In the nearby play ground children were playing football.  Suddenly he remembered that he had forgotten  to take his house keys. When he came yesterday to his   daughter’s house, he had kept it over the table in the sitting room. He turned back and started walking towards his daughter’s house.

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Kuttan (Ku) Nair was  staying in a remote village in Kerala. The house  was constructed by his ancestors   years back.  It   was  made out of mud.   Even in summer, the inside of the house was quite cool   His  wife Sulochana (Su)  and daughter Parvati  (Pa) were with him.  There were a large number of coconut, arecanut, jack fruit, teakwood trees in the house  compound.  Also he  was nurturing a quite big  vegetable garden. The surplus vegetables were  sold in the nearby market. In his house compound there was a small  pond. Water was drawn from the pond. In front of the house there was a small stream. Beyond the stream was paddy fields.  Altogether it gave  really a panoramic view.

Ku’ spent most of his time in the field and garden.  He was able to raise sufficient money from the sale of the agricultural products. There was a Krishna temple near  his house. Pa’ and Su’ used to go to the temple regularly in the evening. Once in a year in the month of October there used to be a  pooram  festival in the temple. The celebration  lasted for three days.  Various cultural programs like Ottan thullal , Dance, Chakyar kooth   etc  were being enacted during this period.

Su’  spent her spare time in reading books. There was a small library  near to her house. She used to get books from  there. She  was interested in painting also. She taught  few student painting.

Pa’ was studying in a nearby college. She took part in various cultural activities and won many  prizes. She also acted  as the Editor of the college magazine.

After graduation, she joined as a teacher in the nearby school. At the same time she continued with  her  cultural activities.   By the time her parents started searching a suitable boy for her marriage. They gave advertisement in a local news paper. Pa’  told her parents that she was not interested in marrying a boy working in  the  middle  east. She wanted the boy to be near to her place. After lot of searches, they could identify a boy from the neighboring town. He was working in the state government revenue department.

The marriage was solemnized in the traditional style. Only close relatives were invited for the marriage  After marriage,  Pa’ shifted to her husband’s house. She was happy with her in laws. Father- in- law was a retired government servant. The school was very near to her house. She could come to the house for lunch also.

It was a Sunday evening. Pa’ was seeing a cinema in the TV. Mother in law  was  in  the kitchen preparing evening tea.  At that time she got a whatsup message. After reading the message, she started crying  loudly. Mother in law came running from the kitchen enquiring about the reason of the cry. Pa’ was not in a state to talk. Mother- in- law  sprinkle some water on her face. Then she murmered that her mother was no more.

Pa’ along with her husband immediately rushed   to her house. Almost all the neighbors were there. Her immediate neighbor  started consoling her. She paid respect to her departed mother and sat near the dead body. She could not imagine that her mother would meet such an untimely death. She was told that mother was watering the kitchen garden. Suddenly she felt some uneasiness and  fell down.  She was immediately taken to the near by hospital  but was  declared as brought dead. After the death - ceremonies  she returned to her husband’s  house. She requested her father to come and stay with her. But he did not agree. He told hat he has to look after his paddy fields and vegetable garden. But  he agreed to come to her house in the week end.

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Ku'  walked a bit fast. It was getting dark. Children in the nearby houses started chanting  prayers slightly in a louder voice. He opened the gate of her daughter’s house. Walked towards  the portico of the house. He was about to knock on the door. At that time, he heard a conversation   in a very  low tone between Pa’ and her husband.

“I don’t think the old man will die in the near future.”

“He  is  keeping good health now also.”

‘When he dies, I  want   to sell  the property and purchase

a new flat in the town.”

“That will be nice. I am completely fed up with this  village  life.”

Ku’   could  not  believe his  ears. He was till now thinking that his daughter was  not so greedy and   was loving her father very much.

Ku’   collected   the  keys. He could not tell  any  thing  to Pa’. He came out of the house and started walking  to his  house. Old memories cropped up in his mind. He could not control his sorrow. Tears rolled down from his eyes. 

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Erosion control using Geo Synthetics

 Erosion Control using Geo synthetics

Erosion of soil takes place due to the action of flowing water, rain water or wind. The soil particles then get displaced which in turn creates various   engineering and environmental problems. It is therefore very essential to prevent soil erosion. There are different methods to arrest the erosion. One of the effective and economical methods is the use of geosynthetic mats for erosion control.

Introduction

Soil erosion takes place when the shear force generated due to the external agencies such as wind and flowing water exceeds the shearing resistance of the soil particles. To control soil erosion, the shear resistance has to be increased.

Due to erosion, the banks of rivers may cut into the natural ground, road/ railway embankments may collapse leading to serious catastrophes. In case of agricultural soils, the top layer of soil may get depleted and may lead to the loss of fertile soil. It is reported that the soil is swept and washed faster than natural replenishment to the tune of 10 times in USA and 30 to 40 times faster in China and India.

Erosion can be controlled by different methods as natural vegetation, turfing, rip-rap, stone pitching, mats and gabions. But for the last fifty years, geo synthetic materials are being used in large quantities.

Characteristics of Soil Erosion

The main factors affecting erosion are intensity of rain, quantity of rain, duration, slope of the ground and soil permeability.

The types of erosion are - splash, sheet, shore line and rill & gully.

The processes involved in erosion are - detachment, transportation and deposition.

Geo synthetics

Geo means earth or soil and synthetics means man-made. Geo synthetics are made from petrochemical based polymers (plastics) which are biologically inert and will not decompose from bacterial or fungi actions. These are porous fibers manufactured from synthetic materials such as polypropylene, polyester, polyethylene, nylon, polyvinyl chloride and different mixes of these items. They are available in different thicknesses and widths in rolls of various lengths. These fabrics are durable and strong and can with stand hostile soil environment.

These geo synthetic mats are placed on or in the soil to improve slope stability of embankments, hill sides, and river / stream banks. Different geo synthetic materials are geo- textiles, geo- grids, geo- cells, geo- membranes and erosion control materials.

Method of Installation

-         Level and compact the area after removing vegetation, debris, stones and              other discarded materials.

-         Lay the mat and anchor it at the toe of slope properly.

-         Construct gabions at the slope benches

Advantages of Geosynthetic Mats

The main advantages of geo synthetic mats are:

 Easy and quick installation, economical, environmental friendly, maximum root anchorage, helps in the growth of vegetation and reduces water and wind velocities.

Conclusions

Erosion is a natural phenomenon and can’t be avoided altogether. But its effects can be reduced by taking suitable methods. One such effective and economical method is the use of geo synthetics for the control of erosion.

Image courtesy: http://www.flickr.com/photos/drainage-erosion-virginia/4293695138/

References:

1. Principles of Soil Mechanics and Foundation Engineering, V N S Murthy,UBS Publishers and Distributors, New Delhi,1992

2. Construction Engineering and Management, S Seetharaman, Umesh Publications, Delhi, 2003

3.Construction and Foundation Engineering, J Jha, S K Sinha, Khanna Publishers,Delhi,1977

Links:

http://www.brighthub.com/environment/science-environmental/articles/94028.aspx

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Happy and Joyful Life

Happy And Joyful life

Tags:  Joyful life , happiness, food, shelter , clothing

Everybody in this world  want  to lead a healthy and happy life.  But is it possible?  It is difficult to quantify the degree of happiness. Happiness  is a state of mind and depends on the attitude of the person concerned.

The basic requirements of a human being are food, shelter and clothing. One can have a meal of a small quantity of cereal while another can have a five star meal; one can have a  small one room hut  for self and family while another may have a multi storey house in a  large estate; while one can have a single piece cheap dress while anther can have a gold laced costly three piece suit. In addition to the basic amenities, one should have good physical and mental health . Then only one should be able to enjoy life to its full extent.

But what is the  state of most of the people of this present day world. From a small baby to a  grownup youth to a senior citizen, almost all are under some sort of pressure due to the mental agony ,worry and tension. It can be on the personal account, official account or on social account.

Is there a remedy for all these problems? Yes, it is there; but one has to find the solutions himself and practice accordingly. If one can control his emotions, his anger, resentment and greediness and then have a positive outlook towards life, one will be able to lead  a happy and joyful life.

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Natural Resources - Forests

 Natural Resources – Forests

                                 Natural Resources - Forests

Tags: forests, deforestation, afforestation, soil erosion, global warming

Nature has provided us many natural resources such as forest, land, water, energy, mineral etc. A resource is a source of supply held in reserve. Among them forest is one of the important resource. In the early periods,  man cut trees for getting timber for constructing his house, for obtaining fire wood and also for clearing forest for agriculture. But in course of time as population increased, his needs also increased and he started inflicting too much pain on the forest by clearing the forest area for constructing dams, industries, agriculture, air ports, high ways – like that for many infrastructure works. Trees improve our aesthetic environment ,absorb noise and create calm and peaceful atmosphere.

Forest can be defined as a community composed of trees, plants, shrubs etc serving as an abode for animals and birds. Approximately one third of the earth’s land area is covered by forests. The services rendered by forests can be grouped under three categories – productive, protective and regulative. People collect from forests fruits ,roots, herbs, fire wood , fodder for animals and timber for house construction. The main protective functions of forests are conservation of soil and water. The regulative functions are absorption, storage and release of gases like carbon dioxide and oxygen. Forests help in regulating atmospheric temperature.

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It has been reported that during king Ashoka’s rule emphasis was given to tree planting and its upkeep. Also in several parts of kerala people used to worship trees and did ‘ poojas’ in what is called as snake gardens. The per capita forest area available in India is only 0.06 hectares as against 0 .64 hectares of world average. Destruction of forests is going on at an alarming rate – approximately 10 million hectares per year.

The main causes of deforestation as mentioned earlier are clearing the areas for construction of dams, air ports, industries, high ways, agriculture and mining. Extreme weather conditions, over grazing by cattle and forest fires also contribute for deforestation. The deforestation causes many hardships such as reduced rain fall, increased soil erosion, decreased soil fertility, climate change and frequent floods. Deforestation causes loss of biodiversity, leading to disturbances in ecological balance.

As such, it is very essential for forest conservation as well as proper management of the resources. Tree felling should be matched by an equal number of trees planting.  Afforestation should be done in areas not fit for agriculture. In building construction, alternate materials should be used in place of timber as far as possible. Previously for railway sleepers, teak wood was used. But now it has been dispensed with and pre cast concrete sleepers are being used.                                       

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Mix veg Iddli

                                            Mix  Veg Iddli

  

                              key words: iddli, vegetable, rice

Ingredients

Rice & dal batter

Carrot                  2

Potato                  3

Salt

Turmeric powder

Preparation

Wash the potato and carrot

Cut them into small pieces

Add a bit salt and turmeric powder and cook

Keep the iddli - plate on a level  top

Fill  half the dip with the rice batter  

Take a portion of the veg. mix and spread over the batter

Again top them with rice batter

Steam the  iddlis  for about 8 to 10 minutes

Take out the cooked iddlis from the plate

Have  it with coconut / pudina chutney and sambar

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Problems of old age

Problems of old age

                 Tags: ageing, life style, diseases, free radicals, antioxidants

        Each and everybody in this world have to pass through different stages in their life time. The different stages are  - childhood , adolescence , adulthood and old age  In the old age , problems are manifold . They can be grouped as follows -  Physical ,Psychological . Financial , Family related. In the advanced age the old are more prone to face various      accidents. Their eye sight may get impaired, may be difficulty in hearing. various life style diseases like diabetes, blood pressure, cholesterol , memory loss (dimentia) etc . Elderly population in India is 138 million  in 20121. 

          As discussed, old age is an inevitable stage  in everybody's life. But the irony is that all  want to remain, youthful always. As days pass, one gets older and changes take place both physically and mentally. Ageing is a natural process which affects the whole body. Since it is a natural process, it can’t be stopped altogether but can only  be slowed down to a certain extent. The rate of ageing will speed up on account of lack of exercise, improper food, lack of sleep and mental worry. By correcting the lifestyle, the rate of ageing can be slowed down considerably.

        In old age skin loses its elasticity, eye sight gets impaired, muscles weaken, black hair turns to white, teeth get decayed and various other diseases increase. Heredity plays a very important role in ageing. Highly corrosive oxidising elements called free radicals attack our body. The main causes of free radicals are air pollution, strong sun light, cigarette smoking and absence of nutritious food. As  a remedial step, antioxidants should be taken which break down the free radicals. The main anti oxidants are vitamins - A, C and E and the mineral selenium.

 Summarising, the main effects of ageing are:

Increased chances for heart attack, arthritis , cancer

Impaired hearing, loss of teeth, cataract etc

Black hair turning white

Poor sleep, irritability

Bones turn more brittle due to loss of calcium

As mentioned earlier, ageing is a natural  process 

which can’t be stopped but can be only slowed down

to a certain extent  by changing the life style.

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