Bridge Manual 1998-86-108 PDF

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CONSTRUCTION OF FOUNDATIONS FOR BRIDGES CHAPTER - IV CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 401. 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Pipe and box Culverts with open foundation 3LSHDQGER[FXOYHUWVFDQEHFRQVWUXFWHGDIWHUUHPRYLQJWKHWRS VRLOLQEHGWRWKHUHTXLUHGGHSWKDQGUHSODFLQJLWZLWKDOD\HURIOHDQ FRQFUHWHDIWHUWKHEHGLVOHYHOOHGDQGZHOOFRQVROLGDWHGE\UDPPLQJRU UROOLQJ 5HIHUHQFH PD\ EH PDGH WR $QQH[XUH  IRU D  W\SLFDO DUUDQJHPHQW3LSHDQGER[FXOYHUWVVKRXOGQRWQRUPDOO\EHSURYLGHG ZKHUHWKHEHGLVOLNHO\WREHVFRXUHG 403. Other Bridges with open foundation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xcavation using coffer dam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hoice of pile materials 5&&SLOHVERWKGULYHQDQGERUHGPD\EHXVHG'ULYHQSLOHVPD\ EHHLWKHUSUHFDVWRUFDVWLQVLWX7LPEHUSLOHVPD\KRZHYHUEHXVHGIRU WHPSRUDU\UHVWRUDWLRQRIWUDIILF7KH\VKRXOGEHUHSODFHGZLWKSHUPDQHQW VWUXFWXUHV$W\SLFDODUUDQJHPHQWRIDWHPSRUDU\ZRRGHQSLOHEULGJHLV VKRZQLQ$QQH[XUH INDIAN RAILWAYS BRIDGE MANUAL  CHAPTER -  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 406. Soil Exploration for design and construction of piles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04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 6. Well cap : The bottom of the well cap shall, as far as possible, be located 300 mm above low water level. All the longitudinal bars from the well steining shall be anchored into the well cap. The well cap shall be designed as a slab resting on the well steining. 419. Pitching of the cutting edge and well curb The curb should be generally pitched at about 15 cm to 30 cm above the low water level. The pitching level may be kept higher if the water level in the river is subjected to greater fluctuations like in tidal areas. In case the site is dry, excavation should be carried out upto the level at which the well curb is proposed to be pitched and the centre of the well curb carefully marked. The well curb should then be assembled on wooden blocks or sand bags placed at intervals of about 1.5 metre. In case the well has to be sunk in water, an island is formed, and the top of the island is levelled and compacted lightly and marking for setting the cutting edge is done on the level surface. The concrete should be of mix not leaner than M-20 grade. After concreting the well curb the outer shuttering may be taken off after 24 to 48 hours depending on the temperature. The inside conical shuttering can be taken off after 72 hours. The wooden block supports can be taken out alternatively one by one, supporting the well curb on sand bags using a jack, for the purpose. Vertical gauges on four sides of the well from the centre of the cutting edge should be provided to monitor the verticality of the well during sinking. RCC well curb should be allowed to set for at least one week before sinking is started. A well is most unstable in the beginning when it has no grip in the sand or when the grip is very small. The chances of tilting increases considerably if the well is made top heavy by raising the masonry of the steining too high in the first instance. The best course is to sink the well curb alone after allowing it setting time without raising the steining above it. 420. Concreting of steining The well steining should be built up in stages initially 1.20 to 1.50 metres at a time, as it is gradually sunk through the soil, keeping sufficient free board above the water level. Once well has acquired INDIAN RAILWAYS BRIDGE MANUAL 81 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES a grip of about 6 metres, the steining can be raised 3 metres at a time to obtain a better rate of progress. Inner shuttering and bracing should not be removed within 24 hours of casting. 421. Sinking of wells in water 1. The sinking of well is done by removing the soil with grabs or chiselling and drawing out the soil. Sinking of steining should not be done within 48 hours of casting. 2. In stagnant water and in water with velocity upto about 2.0 m/s and of depth upto about 5 metres, construction of island may be resorted to. In greater depths, the use of steel caissons would become unavoidable. 3. Construction of island : a) The island should provide sufficient working space of about 2 to 3 metres all round the well. A minimum free board of 0.6 metre should always be provided. b) For depths of water upto 1 metre, an island may be constructed by laying a few rings of sand bags enclosing the area of the island and filling with sand. Boulders should not be used in the construction of island as they may find a way inside the island and obstruct the sinking of the well. For greater depths, two rows of piles 1.5 metre apart at a spacing of 1 metre enclosing the area of the island may be provided. Upto 1.5 metre depth, bamboo piles may be used and timber ballies may be used upto 3 metre depth. The piles are lashed together with strap, wire ropes or coir ropes. Bamboo matting is then fixed along the inside faces of the piles and the space between the mattings is filled with puddle or sand bags. Beyond 13 metre depth, steel sheet piles should be used. The piles should have a grip of at least 3 metres. Sand bags should be dumped outside the island as a protection against scour. In cases, where velocity is high, wire netting (crates) filled with boulders may be used. (Refer Annexure 4/13). 422. Sinking of wells using caissons 1. In deeper channels and swift rivers, caissons built of steel plates suitably strengthened by angle iron stiffeners and further strutted and tied together by MS angles may be used. Caissons are lowered through water and pitched in position before commencing the sinking. INDIAN RAILWAYS BRIDGE MANUAL 82 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 2. Assembling and launching of caissons : Caissons can be assembled at site itself and launched straight away using barges or can be assembled when the river bed is dry and launched when water level in the river rises. In the first method, a temporary platform is constructed over two barges suitably anchored and a gantry is erected over the platform. The caisson is assembled on the temporary platform. After testing for leakages, the caisson is lifted from the platform and lowered in position after removing the temporary platform (Annexure 4/14) In the second method, the caissons are assembled, tested and kept ready duly filled with water on the river bed when it is dry. When the water level rises, the water in the caisson is pumped out and they are toed into position. The draught can be reduced by covering the dredge holes with steel plates and pumping compressed air into them. As an alternative method, caissons can be assembled on the river bank and brought into the water using the slip ways after which they can be toed into position for launching and grounding. This method of assembling the caissons in dry docks and launching them is very expensive and resorted to only under special circumstances. 3. Grounding of caissons: While lowering, the caisson should be held firmly in position between the barges with greased wooden packings as shown in Annexure 4/15. The barges should themselves be firmly anchored to the river bed. The caisson should be lowered slightly at first by pumping in water or releasing the compressed air from the dredge holes. Later the rate of lowering can be increased by adding weight either by concrete or water. It should be ensured that a minimum free board of 0.6 metre is maintained throughout the grounding operations. Once the caisson has touched the bed, sand bags should be deposited alround to contain the scour. The caisson is then set in its correct position. Further weight is added by pouring concrete in the caisson and dredging operations are commenced. INDIAN RAILWAYS BRIDGE MANUAL 83 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 423. Process of open sinking of wells 1. Sinking of smaller wells may be done with the help of timber shear leg, derrick or timber scotch. For shallow depths, grabbing and removal of the earth can be done manually. For greater depths and where the sub soil water level is high, suitable dredger may be used. The grab can not be operated in the blind area below the curb. Hence, these are suitable for the wells with thinner steining. Steam or diesel winches of suitable capacity can be used for operating the grabs or dredgers. For faster sinking of wells of 6 metre dia and above, suitable cranes may be used. 2. Well Sinking through clay and hard strata : a) In stiff clay strata or in strata with compact sand, shingle and boulders, the use of rail chisel may be required. Use of chisels can be avoided if hammer grabs are used. A sketch of rail chisel commonly in use on Indian Railways is shown in Annexure 4/16. b) For sinking through stiff clay and other hard strata buoyancy effect of the soil may be reduced by dewatering the well to increase its effective weight. c) If due to heavy skin friction, the well is held in a floating condition, air or water jets may be used on the outer periphery of the well for reducing the friction. For this purpose pipes of 4 to 5 cm. dia. fitted with nozzles can be incorporated in the well close to the outside periphery, particularly in the curb portion and also for some height of the steining above. d) When any of the above methods is not effective, a few sticks of gelignite can be detonated under the water below the cutting edge. This results in shaking of the well and reducing the skin friction, which helps in its further sinking. Charging should be started with small quantities in each dredge hole at a time and gradually increased. When there is more than one dredge hole, such charging and detonation should be done in all the holes simultaneously. INDIAN RAILWAYS BRIDGE MANUAL 84 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES 3. Precautions to be taken during well sinking: a) Blowing of Sand: Great caution is necessary when dewatering of well is done at shallow depths or when the well has not gone into the soil by at least 1 metre. The difference in the hydraulic pressure inside and outside the well may create a passage for rush of sand from outside the well resulting In “blowing of the sand”. Sand blowing can endanger the safety of men working inside the well and can also cause sudden tilting of the well. Seepage of water should be carefully watched during sinking and should be checked by putting sand bags over the area where such seepage is noticed. In severe cases of sand blowing, large quantity of the sand is sucked into the well and a funnel shaped depression is formed outside the well as shown in Annexure 4/17. Empty gunny bags and branches of the tree with green leaves may be thrown into the funnel and dredging continued till the sand blow gets arrested. The well can then be dewatered completely and excavation continued. b) Quick sand condition:- Quick sand conditions may occur when fine sand or silt underlie an impervious layer of clay with a considerable hydraulic pressure below the clay layer. As soon as the layer of clay is pierced through, a steep hydraulic gradient is established across a fine sand or silt under the clay and it either starts rushing upwards or is in a state of incipient motion. It has no shear strength in this state and allows the well to sink into it without offering any resistance. In most cases, the sand rises to a considerable height above the cutting edge and remains there inspite of continuous dredging. The problem can be faced to a certain extent if the steining of the well is raised to a considerable height when the cutting edge is well within the clay layer. The level of water inside the well should also be raised by pumping in water. Dewatering should not be tried under any circumstance and no one should be allowed inside the well when quick sand condition develops. By keeping the water level inside the well higher, a hydraulic gradient is established in the reverse direction and the quick sand condition is not allowed to develop. INDIAN RAILWAYS BRIDGE MANUAL 85 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES Even if it does develop, there is considerable margin of safety and the well does not sink below the bed level. c) While sinking wells in deep water, divers with their equipment should be present for emergencies. 424. Tilt and shift of the well 1. Limits of tilt and shift : a) As far as possible wells shall be sunk without any tilt and shift. A tilt of upto 1 in 100 (1%) and a shift of D/40 subject to a maximum of 150 mm can be permitted. b) Excessive tilt and shift, which cannot be corrected, should be taken into account for rechecking the design of the well and the resulting foundation pressure. c) The gauges marked at quarter points on the outer periphery of the steining starting from the bottom of the cutting edge mentioned earlier are used for checking the tilts. Water level readings on all the four gauges are observed frequently to get an idea of the direction and extent of tilt. Where the well is not sunk through water, plumb bobs are used on all four sides to judge the verticality of the well. It should be noted that plumb bobs are used only for checking for tilt during sinking and should never be used while building up the steining. 2. Tilt correction : Depending on the site conditions, any one of the following methods may be adopted either separately or in combination with others for the rectification of tilt which may occur due to the well encountering very soft material on one side and hard material on the other side or when there is a log of wood or a big boulder under the cutting edge on one side of the well. a) Eccentric dredging : The dredging is confined to the higher side and is done very close to the inside face of the steining and even a little under the steining. b) Eccentric loading : The side which is higher is loaded either by placing kentledges on the steining or by placing the load on a cantilevered platform (Annexure 4/18). Eccentric dredging should also be carried out to aid the tilt correction. INDIAN RAILWAYS BRIDGE MANUAL 86 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES c) Applying pull to the well : Light pull can be applied to a well by taking a wire rope round the well and anchoring the tackle to a dead man anchorage or a large tree if available in the vicinity. The tackle is worked by a winch and tension is maintained as sinking progresses (Annexure 4/18). For applying heavy pull, wire ropes are taken round and fixed to a large dead man anchorage. Rails or other kentledges are then placed on the wire ropes to develop high tension and the tilt gets rectified as the well sinks (Annexure 4/18) d) Applying push to the well : Light push can be applied by driving a strut between the well and the bank. The strut is made tight by driving wedges. For applying heavy push, two timbers or struts of steel of suitable section are tied together in the shape of a nut cracker with the handles spread apart and the load is placed at the hinge. Care should be taken to see that the push is not excessive. e) Packing the low side of the well with sand bags under the splayed portion. This can be adopted only when sinking is done under dewatered conditions either by pumping or using compressed air. The side which is lower is packed with sand bags and excavation is carried out only on the high side. This method should be used cautiously if the depth of the well is shallow and when the well is resting on a sloping rock surface. 425. Use of divers for sinking When dewatering is not possible and the use of pneumatic equipment for sinking is uneconomical, divers can be deployed for the removal of obstruction or clearing the strata. No man suffering from any chronic disease, alcoholic excess, ear or heart troubles or having a sluggish blood circulation or who has excess of fat should be employed as a diver. Theoretically a diver can work upto a maximum depth of water of 75 metres. But in practice it may be limited to about 35 metres. Any diver who will be employed in depths beyond 10 metres should be medically certified. The descending and ascending should be done slowly so that the diver can adjust himself to the pressures at various INDIAN RAILWAYS BRIDGE MANUAL 87 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES depths. Durations of ascends and stoppages at various depths and stay under water at various pressures as laid down in the relevant British standard Specifications should be strictly adhered to. 426. Pneumatic sinking of well 1. Pneumatic sinking is used when other methods are not found feasible, particularly when the wells have to pass through considerable depths of intervening layers of rock or when the bed is full of large boulders or interlocked small boulders. This method may be employed for depths varying from 12 metres to 33 metres. 2. The inside of the well is made into a closed air tight box chamber and all water from this chamber is expelled out by letting in compressed air. The pressure of air inside the chamber should be maintained at approximately 0.12 kg/cm2 above atmospheric pressure per metre depth below water level. The dredging operation may be carried out inside the chamber in near dry condition. The compressed air arrangements are then removed and sand filling etc. of the well are completed as for the open dredging. The working chamber must be practically air and water tight and yet there must be an opening for men to enter and leave the chamber, as well as an inlet and outlet for materials. These opening are provided with vertical shafts and air locks. A typical arrangement showing the chamber with the vertical shaft and air lock is at Annexure 4/19. 3. Precautions while working in air lock chamber : a) The lock usually becomes warm and water is required to be sprayed on its outside to keep the temperature down. b) Workmen should be medically examined before they are selected. c) Working time, rest intervals and time and rate of decompression must be carefully regulated when the pressure exceeds 0.7 kg/cm2 above atmospheric pressure. d) Medical arrangements under a medical officer specially trained in caisson disease must be ensured when the working pressure is more than 1.75 kg/cm2 above atmosphere and there must be a medical lock. INDIAN RAILWAYS BRIDGE MANUAL 88 CHAPTER - 04  CONSTRUCTION OF FOUNDATIONS FOR BRIDGES e) The rate of decompression specified should be followed. Working above a pressure of 3.5 kg/cm2 above atmospheric pressure is not allowed except in emergency. f) The steining concrete for wells to be sunk using pneumatic caissons should be as dense as possible to reduce the pore pressure caused by air under pressure trying to escape through fine pores in concrete. g) The joints should be made as air tight as possible to prevent escape of air. Water proof cement plastering can be resorted to on the inside face of steining. 427. Founding the well 1. Settling the well by blasting : After loading the well as specified a small charge of one or two gelignite sticks of 50 gm each is exploded at the centre of the well at the level of straight portion of cutting edge. The well should not go down by more than 25mm. If it goes down, the necessity of further sinking should be examined. 2. Dressing the bottom of the well : a) As far as possible, the well shall be evenly seated on sound rock devoid of fissures, cavities, etc. b) One or more cylindrical holes may be made in the base to give good anchorage to the well. (Annexure 4/20 a). Alternatively anchorage can be provided by the rock itself which is allowed to remain projecting at the centre. (Annexure 4/20 b). c) In shallow wells and wells resting on rock a few holes may be drilled and MS dowels fixed in them for providing a good bond between the base rock and the bottom plug. d) In case of sand overlaying steeply sloping rocky base below, it is preferable to bench the rock and take the well down to have a proper base. Where this is not feasible, a number of small wells or piles are sunk or driven through the sand till they penetrate into the base rock (Annexure 4/20 c & d) INDIAN RAILWAYS BRIDGE MANUAL 89 CHAPTER - 04 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