The Jet hose in combination with a high pressure high volume pump and a reactionless nozzle will allow a diver to trench or level a tremendous volume of material in a short period of time. The hose most commonly used in the Philadelphia area is a 2 1/2” fire hose coupled to a navy reaction-less nozzle. The navy nozzle has one main jet pointing in a forward direction and four smaller jets pointing back along the hose. It can be placed unrestrained on the bottom and with the balanced force coming from the apposing jets it will not move. Considering the weightlessness of the diver this is a great advantage. A conventional fire nozzle would force the diver backwards with a force equal to that exiting the forward jet. The reactionless nozzle allows the diver to utilize hundreds of pounds of force and water volume to move material. The jet hose works best in softer material, rip rap, branches, and large pieces of trash will not of course blow away. It is also limited when digging deeper excavations as the material tends to fall back into the hole.
Jet Hose:
Commander Ellsberg of the USN tells about discovering the advantages of the reaction-less nozzle in his book about the salvage of the USN Sub 151 entitled “On The Bottom”.
Many divers still prefer making a “T” nozzle out of plumbing fittings. Although a bit bulkier they work at least as well as the Navy Nozzle in most applications and have some advantages in others.
The air lift requires a compressor, an air hose and a long tube. When used for hand excavation the air lift tube is from 8” to 12” in diameter and 6’ to 10’ long. The air hose is used to introduce air into the water column inside the tube. This reduces the hydrostatic head inside the tube relative to the hydrostatic head outside the tube. The water rushes into the bottom of the tube and out the top picking up any sand, mud or small stones near the mouth of the tube as it goes. The more diffuse the water bubbles in the tube are the greater the differential of hydrostatic head. An air lift can be made on the job site by wiring a cp hose into the mouth of any pipe light enough for the diver to manage and it will work. An annular collar formed around the air lift tube with small holes drilled through the tube under the collar will give the greatest efficiency. In any case the air should be introduced within a foot or 18” of the bottom.
If the air lift should seal off the bottom opening such as when it sucks up a piece of wood or rock to big to pass up the tube it will become positively buoyant very quickly and head towards the surface. Great care should be taken by the diver to ascertain his umbilical is never in a position to be fouled should the air lift decide to take an unscheduled trip to the surface. Should the diver be pulled to rapidly to the surface he could experience a pulmonary embolism, sinus squeeze or ruptured ear drums. It is our practice to install a ¾ ball valve on the exterior of the lift as well as one at the surface next to the dive station. This allows the diver or the tender to cut off the air very quickly.
If the diver finds that some of the heavier material is falling back into the excavation he can tie the top of the air lift down so that it leaves the excavation at enough angle to insure the material will fall outside of the hole. Alternatively a 45 degree angle and short section of pipe can be added to the top of the air lift tube. The material leaving the air lift will now shoot up and away from the air lift and in most instances will not fall back into the excavation.
Air lifts will lift materials well above the water surface. In some instances they are used to deposit material directly into a barge. The rule of thumb for figuring the height that an air lift will lift material above the surface of the water is two thirds of its’ length submerged, one third of its’ length above the surface.
Air lifts are simple reliable excavation tools. They cannot be used in very shallow water. They do not transport material well in a horizontal direction.
The water dredge requires several lengths of rigid 4” or 6 “ suction line, a jet hose pump, and a water dredge. The water dredge is most often formed from a metal tube with a fitting for a 2 ½” fire hose to enter the side of the tube in such a manner as to force the jet of water up the pipe. The dredge can be placed at the end of the suction hoses or if the diver finds it more easy to maneuver the hose it can be placed in the middle of the hose sections. While not as powerful as the air lift and not able to break up and push material like the jet hose it has the advantage of being able to move material horizontally under water. This is often an advantage when digging deeper excavations or when not suspending material in the water column is advantageous. Water dredges are often used in combination with jet hoses. The diver jets the material to the water dredge suction and the water dredge carries it some distance out of the excavation. The water dredge will suck up a divers hand or foot as well as his umbilical . This is generally not a serious matter due to the relatively mild suction formed at the mouth of the water dredge. Still the diver should pay close attention to the relative position of the water dredge his body and his umbilical.
Our modular float system is made up of 22” square plastic Jet Floats. They are stored on their own trailer ready to go to work. Two men can unload them and put them together in less then 90 minutes. They can be assembled into a barge with a moon pool, a “T” head dock, a “U” to make any boat a powered barge, a sidewalk to get your work area or any configuration you may need. They are strong enough to drive a truck over and light enough to be moved and assembled by hand. Unlike conventional floats and barges each 22” modular cube is entirely isolated from the other cubes so if an accident punctures a few cubes the remainder retain their buoyancy.
Abutment – A structure supporting the shore end of a bridge or pier.
Batter Pile – A pile intentionally driven out of plumb to resist lateral movement. Less commonly known as a brace pile
Beam – Any structural member carrying weight from one support to another.
Bearing Pile – Plumb piles bearing the weight of a structure.
Bent – A row of piles fastened together.
Bollard – A mooring device.
Bracing – Horizontal or inclined structural members connecting piles in a bent used to increase lateral stability. Inclined members often form an “X” and are called X braces. Horizontal braces are commonly referred to as clamps as they are often paired one on each side of the pile bent thereby “clamping” the piles between them.
Bulkhead – A retaining wall or barrier.
Buttress – A brace on a retaining wall.
Caisson – Any large diameter shaft excavated inside of a protective casing to bearing strata.
Camel – A floating log timber in front of a dock to keep ships away from the dock.
Cantilever – A projecting portion of a structure supported at one end only.
Capstan – Rotating spool used to pull heavy lines.
Cat Walk – Walkway beneath a dock.
Cell – A round cofferdam constructed of sheet piles.
Chock – A piece of timber used as a separator between piles or timbers. Fender systems on piers were constructed of vertical members called fenders separated by horizontal chocks.
Cleat Mooring device – Line is placed in a figure eight around the horns to fasten lines from vessels.
Cluster – A group of closely driven piles often used as a fender, mooring point or breasting surface.
Cofferdam – Any dam used to exclude water from a construction site. Most commonly constructed of steel sheets today.
Column – A structural member carrying its load vertically.
Creosote – Coal tar, heated and forced into timbers under pressure to act as a preservative.
Crib – A heavy timber box often filled with stones, sand or mud.
Cross Bracing – Inclined structural members connecting piles in a bent used to increase lateral stability. Also known as “X” bracing.
Cutoff Wall – Interlocked sheet pile wall designed to prevent the loss of fill at the interior side of a relieving platform.
Deadman – Any buried member serving as an anchor for the structure it is attached to.
Dead Load – The weight of the structure itself.
Deck – Structural member in a horizontal plane serving as a surface or floor of a pier, dock or wharf.
Diaphragm – A stiffening member between the flanges of a beam or girder also a connecting sheet pile wall between adjacent sheet pile cells.
Dolphin – A structurally independent section of a pier designed for mooring and or breasting of vessels. Similar in function to a cluster but structurally more complex.
Drift Pin – A metal rod driven into a tightly fitting hole bored through two pieces of timber.
Eccentric loading – Condition arising from piles driven out of plumb.
Embedment – Length of piling driven into the earth. Many older piers have slips dredged deeper to accommodate ships with a deeper draft than those they were designed to accommodate. The dredged slip may approach the embedded depth of the piles adversely affecting the stability of the pier.
Encasement – Any structure surrounding a section of piling intended to protect or repair that piling
End bearing pile – A pile transmitting its load axially to a firm bearing surface.
False work – Temporary piles and or structure designed to aid in the construction of a structure.
Fairlead – Device mounted on the side of a vessel meant to guide a line, prevent it from moving laterally and allow it to lead over the edge of the vessel without chaffing.
Fender Pile – Any non bearing pile driven to act as protection for a marine structure.
Footing – A structural member designed to distribute the load to the bearing materials or bearing piles.
Friction pile – A pile depending upon friction between its surface and the surrounding material it is embedded in to support its load.
H-pile – Structural steel member with an H shaped section used as a pile.
King Pile – The center pile in a dolphin or cluster used to place mooring lines around.
Knee Brace – A short diagonal brace.
Lagging – Timbers placed between plumb piles to retain earth or fill.
Live Load – The moving or non permanent load a structure is designed to support in addition to the dead load.
Mooring Piles – Piles specifically installed to provide mooring for a vessel.
Mudsill – A timber structure placed in the mud as a support.
Pier – An intermediate structural support between the abutments of a bridge. A Marine structure protruding out into the water in such a manner as to provide docking facilities perpendicular to the shore line.
Pile – A structural member placed in the ground to transmit a load to a firm bearing surface.
Pile Bent – Two or more piles driven in a row transverse to the long dimension of a structure and fastened together by means of bracing and capping.
Pile Cap – A structural member placed on the top of a line of piles to distribute the load of the structure above to the head of the piling.
Pile clamps – Horizontal braces installed so as to clamp the piling between them. They are often installed at the head and low water mark of piles on high deck piers.
Pipe pile – Pipe used as a pile.
Plumb Pile – Pile installed as close to vertically as possible.
Prestressed Pile – Pile constructed of concrete and steel reinforcement installed under tension.
Retaining Wall – A wall designed to hold back earth or fill.
Sheet Pile – Piles, often with a lock connecting them, driven next to each other to retain earth, fill or water.
Shim – Any small piece of wood or metal designed to fill a gap between structural members.
Shoring – Temporary braces.
Soldier Pile – One of a line of piling driven so as to allow the placement of lagging between them, often used to secure the banks of an excavation.
Spall – An irregular dish shaped depression left when a small area of concrete is broken off due to mechanical damage or rusting and expansion of the reinforcement rods.
Spliced Pile – Two or more pile sections joined to make one pile.
Stringer – Structural members connecting pile caps.
Tremie – A method of installing concrete under water, also the finished product.
Wakefield Piles – A sheet pile constructed of three planks so as to leave a groove on one side and a protrusion on the other. Often used to construct cut off walls.
Waler – A horizontal structural member designed to hold the heads of sheet piles in line and often connected to a dead man.
It is sometimes necessary to estimate distance such as across a river. The following method was taught to me by John Malatich, a hard hat diver I tended when I was breaking into the business.
1. Pick out a fixed object on the bank on the other shore. A tree works well. (A)
2. Walk up river and pick out another tree on the bank on your side of the river. (B)
3. Keeping the two trees lined up go away from the river for about the distance you guess the river might be wide. This distance is not critical so don’t worry if you have a hard time judging distance.
4. Now make a pile of rocks. (C)
You should now have three points forming a diagonal line across the channel.
5. On your side of the river measure the down river distance between tree two (B) and tree one (A) to make point (D).
6. Starting back at tree two (B) walk up river that same distance.
7. After reaching this point if you measure away from the river to where a line
perpendicular to the river would intersect the line you created with the two trees and the rock pile you will have the distance across the river.
If your curious as to why this works – get your seventh grade geometry book out, like I did, and find out the minimum information you need to describe a right triangle. Obviously, if you know the lengths of all three sides you know what triangle you have. If you don’t have the length of all the legs, like in our case, you can also use the length of one leg and the angle two of the legs make when they intersect. Once you have a duplicate of the triangle on the river bank you just measure the distance across the river.