# Soil mechanics and foundations bc punmia pdf

Posted on Thursday, June 3, 2021 9:11:50 AM Posted by Audrey S. - 03.06.2021

File Name: soil mechanics and foundations bc punmia .zip

Size: 1509Kb

Published: 03.06.2021

## Soil Mechanics and Foundations by Dr. B.C. Punmia- Ashok Kumar Jain- B.C. Punmia- Arun Kr. Jain

Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Punmia- Ashok Kumar Jain- B. Punmia- Arun Kr. Uploaded by PawanKumar. Document Information click to expand document information Description: soil mechanics for engineers. Date uploaded Feb 11, Did you find this document useful? Is this content inappropriate? Report this Document.

Description: soil mechanics for engineers. Flag for inappropriate content. Download now. For Later. Soil Mechanics and Foundations by Dr. Related titles. Carousel Previous Carousel Next. Reinforced Concrete Structures- Volume 2 by Dr.

Punmia- Ashok Kumar Jain- b. Punmia- Ashok Kr. Jain- Arun Kr. Design of Steel Structures B. Irrigation and Water Power Engineering by Dr.

Punmia- Dr. Design of Reinforced Concrete Structures m. Jump to Page. Search inside document. It is further recommended. The well is acted upon by an uni- directional horizontal force P in a direction across the pier.

The well is founded in sandy stratum. The ratio between contact pressure and corresponding displacement is independent of the pressure. The co-efficient of vertical subgrade reaction has the same value for every point of surface acted upon by contact pressure.

The analysis that follows is that suggested by Banerjee and Gangopadhyay When a rigid well, embedded in sand, starts moving parallel FIG. Let p be the load per unit arca of vertical surface of sand and p be the corresponding displacement. Assum- jing that p, is the displacement required to increase the value of resultant unit pressure form zero to p,, we have.

Let p be the deflection at a distance x from the centre O of the base. The load coming on the cutting edge is uncertain as a considerable part of it is borne by skin friction.

Another factor of uncertainty is in regard to the effective depth of the well curb, since the entire well acts as a deep girder to resist torsion and bending. The well curb has also to withstand stress due to sand blows, as well as due to light blasting required when boulder obstructs the sinking of the well Cutting edge. The cutting edge should have as sharp an angle as practicable for knifing into the soil without making it too weak to resist the various stresses induced by boulders, blows, blasting, etc.

In concrete caissons, the lower portion of the cutting edge is wrapped with 12 mm steel plates which are anchored to the concrete by means of steel straps. A sharp vertical edge is generally provided along the outside face of the caisson. Such an edge facilitates the rate of sinking and prevents air leakage in the case of pneumatic casissons. Steining thickness. This is, however, contrary to the usual practice of providing greater thickness of steining with increasing diameter of the well as given in the following table : From which D outside diameter of well t steining thickness 3m 0.

Moreover, for deeper wells, water is invariably met with and the effective self-weight is reduced by buoyancy in the portion of the well below water level, and hence larger steining thickness is required.

To overcome the inreased skin friction and the loss in weight of the well due to buoyancy, additional loading known as kensledge is applied on the well. Pumping out the water from inside the well is effective in sinking of well under certain conditions. Pumping should be discouraged in the initial stage. Unless the well has gone deep enough or has passed through a ring of clayey strata so that chances of tilts and shifts are minimised during this process. Complete dewatering should not be allowed when the well has been sunk to about 10 m depth.

Sinking thereafter should be done by grabbing, chiselling, applying Kentledge and using gefignite charges. Only when these methods have failed, dewatering may be allowed upto depressed water level of 5 m and not more. On certain occasions a well is struck up and normal method of keniledge and dredging fail co sink it further. In such a case frictional resistance developed on its outer periphery is reduced considerably by forcing jet of water on the outer face of the well around.

This method is effective in case the well is being sunk in sand strata. Tilts and Shifts. The primary aim in well sinking is to sink them straight and at the correct position, Suitable precautions should be taken to avoid tilts and shifts, Also proper records of tilts and shifis should be maintained and measure should be taken to Counter-act tills and shifts. The precasutions to avoid tilts and shifts are as follows: 1.

The outer surface of the well curb and steining should be as regular and smooth as. The radius of curb should be kept 2 to 4 cm larger than the outside radius of well steining. The cutting edge of the curb should be of unifrom thickness and sharpness since the sharper edge has a grater tendency of sinking than a blunt edge.

The dredging should be done uniformly on all sides in a circular well and in both pockets of a twin well. The tilts and shifts of well, if any, must be carefully checked and recorded.

The correct measurement of the tilts at any stage is pethaps one of the most important field observations required during well sinking. Unequal dredging causes tilts and hence if higher side is grabbed more by regulating the dredging, the tilt can be rectified Fig. This method is not very effective when the well has been sunk to a great depth.

In that case, a hole in the steining of the well is made on the higher side, and by hooks, the rope of the grab is pulled towards higher side to the maximum possible extent Fig. The hole is made near the ground level. The well may be dewatered if possible and open excavation on the higher side is carried out.

In such a case a welded frame bracket is used as shown in Fig. In this method, water jet is forced on the outer faces of the well, towards the higher side so that skin friction is reduced towards the higher side, The method if used alone is not very effective but provides a contributory effect if used with other methods. A filled well generally. In such a case, the well is dewatered, if possible and safe, an open excavation is done below the cutting edge of the higher side. In some cases wooden.

Hooking the cutting edge on the lower side of the well with the help of the steel wire rope, pulled, and kept strained by steam which also has a similar effect Fig, Pulling the well. This method is effective only in early stages of sinking, The well is pulled towards the higher side by placing one or more steel ropes round the well with vertical sleepers packed in between to distribute the pressure over larger areas of well steining.

The pulling of ropes may be carried out by winches [Fig. This method is used to avoid any further increase in the tilt of the well rather than reetifying it. The well is strutted on its tilted side with suitable logs of wood. The well steining is given covering plate to distribute pressure.

The other ends of the logs rest against firm and non-yielding base by driving piles ete. Wood pieces are kept ready to be inserted and fixed in the gaps caused by the tilts of the well being rectified viii Pushing by jacks. The well may be pushed by force applied by hydraulie or mechanical jack on the tilled side of the wells. In order that sub-soit water may not enter the working chamber, the pressure of air in the shaft is kept just higher than that of the water at that depth, However, the maximum pressure is limited from the considerations of health of persons who work inside the chamber.

Normally, the tolerable air pressure under which a man can work is limited to 3. The air lock may rest on rubber seals just above the cutting edge. The number of air locks may vary from one to three. Generally, two ait locks are used — one for sending men inside and the other for moving the excavated material with the help of a much bucket and hoisting rope. Afier properly placing the air lock in position, so that direct air entry is scaled, water is pumped out from the bottom and air pressure is gradually increased so that fresh water docs not enter the working chamber.

Labourers are then sent down to the working chamber, through the appropriate air lock. In order to prevent leakage of air, arrangement of double gates is provided.

## Soil Mechanics and Foundations by Dr. B.C. Punmia- Ashok Kumar Jain- B.C. Punmia- Arun Kr. Jain

Save extra with 2 Offers. This book is intended to present currently accepted theories, design principles and practices of soil mechanics and foundation engineering. The book provides sufficient material ranging from simple to very complex for undergraduate and postgraduate courses. At the end of each chapter, latest problems from various central competitive examinations has been solved to enable the student to test his reading at different stages of his studies. Punmia : He is an eminent author of 18 books, most of which are followed as textbooks. Having started his career as Assistant Professor in , he was elevated to the posts of Reader in and Professor in