or if not, a hatchway can be cleared through the various floor systems of sufficient size to pass the loads required. The acetylene torch will be found invaluable for dismembering the steel frame, cutting down pipe lines, reinforcing rods, or any other metal obstructions which may be met with. For heavy brick walls and reinforced concrete structures, the skull-cracker, or heavy cast-iron ball, suspended over the part to be shattered by a derrick boom and released for a free fall by means of a trigger attachment or magnet has proven of good economy. A 2-ton weight and a drop of 10 or 12 ft. will break down all but the most obstinate resistance with a few blows.

Wrecking operations are quite generally handled by specialists in that line, as they are the better equipped for disposing of the old materials than would be the ordinary builder. When sublet, it is customary to require the wrecker to remove exterior walls to grade lines and interior walls and footings to basement floor line.

PILE DRIVING

BY NATHAN C. JOHNSON

8. Hand Driving.-The driving of piling by hand is practicable only for very small round piles or sheet piling, and in soft materials, such as wet sand or mud. Where a trip hammer is available, this may in emergency be operated by splaying out the hammer line so that a large number of men can pull on it, hoist the hammer and drop it, but the method is uneconomical.

9. Horse Driving.—The use of a horse or a team to pull up the hammer by means of manila rope falls, or a horse-power drum is the simplest effective power for pile driving. The hammer must be arranged to trip and fall when it reaches a certain height or else have a trip line to drop it. The "horsepower" must also have a ratchet so that the line can be quickly overhauled for each drop of the hammer. This method will prove, however, to be very slow and expensive, as seldom more than 10 or 15 piles can be driven per day even where the penetration is small, and an engine should be obtained if possible.

10. Pile-driving Engines.—The pile-driving engine is a hoist engine with two drums, one of which operates the "hammer line," and the other one the "pile line" for hoisting piles into the leads. These lines should both be of 34-in. or at most -in. plough steel wire rope. The hammer line should have a piece of manila line about 6 to 8 ft. long connecting the wire rope and the hammer in order to give some spring for quick handling of the hammer. The pile line should have about the same length of chain with a hook on the end of it to pass around the pile for hoisting. When the driving requires the use of jets, then a third shaft must be provided on the engine to carry two small drums, or two large niggerheads, to carry the lines for raising and lowering the jet pipes.

The size of a double cylinder engine for a drop hammer of 1600 lb. or less may be a 61⁄4 × 9; for a 3000-lb. hammer or less, a 71⁄2 X 10 engine; and for a 4500-lb. hammer or less, an 81⁄2 X 10 engine. Where a steam pile hammer is to be used, a separate 81⁄2 X 10 hoist should be used, and a locomotive type of boiler of about 40 horsepower provided, which will also be large enough to supply steam for a 71⁄2 × 431⁄2 X 10 steam jetting pump.

11. Driver Leads or Gins.—The leads or gins for a driver should be from 7 to 10 ft. higher than the length of the piles to be driven; and for building foundations should have a very short base, with rollers for moving the rig about. These are standard in all locations, and if more details are required, a treatise on pile driving may be consulted.

The gins of a water-driver are mounted on a scow which is usually about 18 to 20 ft. by 60 ft., by 4 ft. deep. This scow is square at the end carrying the gins, and has a rake at the other end. The gins on a water-driver may be tipped forward for driving brace piles with a small batter, or have a set of false leads extended in front for piles having a large batter or the leads may be tipped. The driving of batter or brace piles with a land rig, is best accomplished with a pendulum driver in which the leads are pivoted and can be swung sidewise at the bottom to give the required batter.

12. Pile Hammers.-Drop hammers for steam drivers are from 2500 to 4500 lb. in weight, usually about 3000 lb. They should have 231⁄2 × 61⁄2 guides, to run in width of 24 in. and upon 6-in. leads. They should not be too long, and should have the weight largely concentrated at

the lower end. For horse driving they must have tripping tongs for releasing the hammer automatically when it reaches the top of the leads.

The steam pile hammer is made in several types of which the pile Warrington-Nasmyth single acting and the Arnott double acting, are among the best, the smaller sizes being used for sheet piles and the larger sizes for large round wood or concrete piles. The striking rams of the three sizes of the Warrington hammer, weighs respectively 550, 3000, and 4800 lb.; the latter hammer weighing complete 5 tons. The No. 3 Arnott hammer, suitable for large sheet pile work, has a total weight of 4500 lb. and a ram of 663 lb. The next to largest size, weighs 12,000 lb.; and has a 1548-lb. ram.

A steam hammer will strike from 60 to 70 blows per minute according to size and type, and will keep a pile moving more nearly continuously than will a plain drop hammer. The best results are obtained in the use of steam hammers in ordinary sand, gravel, or soft clay.

13. Jetting. The use of jets is advantageous when a drop hammer is being used to drive piles in packed sand or very sandy gravel, or in soft firm clay. The functions of the jet pipes are to both lubricate the surface of the pile and to loosen the materials in the path of the pile with water delivered at a pressure of from 100 to 250 lb. per sq. in.

Two jets should be used if they can be arranged. When a single jet pipe is employed, it should be used first on one side of the pile and then on the other to keep the pile going straight. The jet pipes should not be fastened to the pile, but kept moving up and down the pile to extend the lubricated areas from below the point up to the surface of the ground and to keep inflowing soil clear of the sides of the pile.

The jet pipes should be 21⁄2 to 3 in. double-strength pipe, with a %-in. or 1-in. nozzle. All bends should be of long sweep in order to diminish pipe friction losses of pressure. The jet hose should be for 250-lb. pressure, and be clamped on to long nipples with 3 clamps on either side of the joint. The form of nozzle is of importance and should be adapted to the materials to be penetrated.

The pump and boiler capacity must be large enough to deliver the water at 175-lb. pressure for ordinary materials, and at about 250-lb. pressure for hard packed material. A vertical pressure balancing tank between pump and jet pipe is of material assistance in heavy jetting.

The use of a single jet is often effective in sand or fine gravel, if it is first run down full depth where the pile is to be driven; and upon pulling out the jet, if then placed immediately the pile can often be driven full depth without further jetting. Care should be taken in placing jetted piles not to overjet the hole, so that sufficient resistance is encountered by the pile to develop its full bearing power.

14. Pile Points. When piles are of good hard timber, and are axed to a square point, they will drive in all but the hardest material or boulders, without metal points. But in very hard clay and coarse gravel with boulders, steel or cast-iron points are necessary to prevent brooming and to cut the way for the pile. The usual type of strap point is of very little use, as the pile will spread out around it in driving and often broom worse than when unprotected. The best form of point is a recessed circular cast-iron cone, with a rod cast in it to be driven into a slightly smaller hole cored into the tip end of the pile. This cast point, if made in the shape of a triangular pyramid, will cut its ways into much harder materials than will the conical or any other form of point.

15. Detail Equipment. Wooden piles may be kept from brooming at the top during driving by a bonnet casting or else be ringed with iron rings of about % X 22-in. size. Steam hammers may have a recessed base to go over the top of the pile but for drop hammer a similar bonnet of cast steel to run in the leads can be provided.

When piles have to be driven below water or at least below the leads, a follower must be employed. This follower can be made from a first-class piece of pile, which will often last better than one of hard wood. The follower must either be ringed or else have a bonnet casting fitting over the top, and must have a cast-steel base with a bonnet recess for fitting over the top of the pile.

Other equipment such as sledges, bars, dollies, ring pullers, and the like, are usually supplied with a driver. 16. Driving Concrete Piles.-Concrete piles, after curing for not less than three weeks of mild or warm weather, should stand more punishment in driving than wooden piles, but the top of the pile must be protected against shattering by a special cushion cap. This cap may consist of a steel casting having a top recess to receive an oak or hardwood follower block; and a bottom recess to be packed with old hose and rope and lastly with oak blocks to come in contact with the concrete. When the rope or blocks become burned through heat of driving or crushed solid, they must be renewed.

A hole through the center of a concrete pile as provision for jetting, is not so effective as jets used outside of the pile. Where the material into which the piles are being driven is very firm or packed, jets should be used and as much shock on the pile saved as is possible.

17. Cutting Off Piles. When wooden piles have been driven with a follower cap, they are seldom broomed up, and therefore do not require cutting off to give a solid bearing on their tops. But when broomed up from ordinary driving they must be cut off square to solid timber, or if they are not driven down to proper level they must be cut off to proper height. This can be done in the dry by ordinary two-man cross cut saws, but when the cut-off is under water, they must be cut off by a diver or else by a circular saw working on a vertical shaft in the pile driver leads.

There are frequently cases where old piles require removal by cutting them off, and this can be done by a diver, or else by placing three sticks of dynamite around them and firing it by a battery.

18. Pulling Piles.-Steel sheet piles can easily be pulled with special pulling nippers into which the pile line is hooked, or else the hook of a wire rope set of falls. Holes may also be bored through the web of the piles at the top and a shackle bolted on. Reversing a doubleacting steam hammer to strike upward, supporting the whole from a derrick, is also used successfully.

Wooden sheet piles or round piles are pulled by taking several turns around the top of a pile with a heavy chain, or with a wire rope sling, and hooking a set of double or triple wire rope blocks into it. It may be necessary to keep hold of a pile for some time to overcome suction before it starts, but if it does not start readily, a blow or two from the pile hammer may loosen it. Jetting around piles is also of assistance in loosening them as they are being pulled upon.

The use of levers and jacks for pulling piles in soft material is often effective, but for any large number some power rig should be used.

EXCAVATING

BY A. G. MOULTON

Gen

Excavating, with the attendant grading, is necessary in every building enterprise. erally being the first branch of the work undertaken, it is often unconsciously called upon to bear many of the organization expenses that might be more correctly prorated against the succeeding trades. For that reason, a carefully studied program should be mapped out before starting work to be sure that proper methods are chosen and all economies observed.

19. Equipment for Excavating.-Local conditions vary so with each building operation that anything more than a brief description or reference to the proven methods and various types of equipment for excavating purposes would be useless in an article of this kind.

In the case of excavation for solid foundation walls and piers, where the work would be mainly pick and shovel, and the excavated material disposed of by wasting on the banks, or transferred by wheel barrows in the immediate vicinity; or in the case of basement excavation where the ground may be broken up by a plow and removed beyond the building lines by two horse scrapers or slips, or directly loaded into wagons or trucks which have been driven into the excavated area; or even in the case of the larger excavations where the steam shovel becomes a possibility, there is not much danger of a mistake in choice as to method. It is in the deep basement work through varying conditions of soil that the opportunity for careful study of plant layout is encountered.

20. Steam Shovel Excavating.-Where 1500 yd. or more are involved, and where the width of the lot will permit a full swing, it is generally conceded that, except in rock work, the small revolving steam shovel running on tractor equipment provides the most economical tool. On the first cut through, the wagons or trucks are loaded while standing on the grade. When the depth of the cut exceeds the limit of the shovel, it becomes necessary to introduce the bridge or inclined driveway to bring the trucks down to the floor of the cut. A booster engine set on the grade level to pull or ease the loads out, will permit of a sharper incline.

When the depth of cut reaches a point that will prohibit the further use of an incline, other features will have been introduced in the way of holding or shoring of banks with consequent restriction on working area as to render unprofitable the further use of the shovel. If the basement is to go to still further depth, then hand work will be resorted to and the excavated materials carried to above street level and deposited in chutes or hoppers for easy transfer to trucks at that point. The elevation may be obtained either through small cars and barrows on platform hoists or in buckets operated by boom derricks. On such work, the use of the clam-shell will not be practical, as the cross lot bracing for supporting street banks would cause too much interference.

21. Shoring, Sheeting, and Underpinning.-The holding or shoring of street banks and underpinning of adjoining structures, often presents quite serious complications especially if the excavation is to be carried to some depth through treacherous soil. In such instances, the expedient is sometimes adopted of sinking a trench full depth, on the line or curb wall, in advance of the general excavation. This trench may be opened in sections if the entire frontage involved would be too great to handle safely in one operation. The trench will be sheeted tight or not, depending upon the character of the soil, and cross braced with struts and wedges. On heavy work, screws are introduced to make up for ground movement and settlement. Up to 15 ft. in depth, the material from such a trench may be benched out by hand. Beyond that depth, the excavated material should be passed up by mechanical means, such as buckets operated by hand winches or boom derricks. The trench having been completed, the wall is next constructed and upon acquiring normal strength the general excavation of the basement proceeds. Temporary supports to help resist the earth pressure must be given the wall from the inside as the ground is removed. This is generally obtained through batter braces, which are left in place until the building columns and permanent framing have been installed.

21a. Sheet Piling and Shifting Soils.-Where ground conditions are good, such as in clay, or compact sand and gravel, the above method with its great amount of hand work would be too expensive. In such cases, the general excavation would be carried down the full area of the lot and the banks left at sufficient slope to stand alone, or skeleton braced from the inside. In dry sand and running soil, a tight sheet piling will be required. This may be composed of vertical planks, square-edged or matched as the case may require, and driven through by hand or by small sheet hammers operating on steam or compressed air. When water is to be encountered, a system of steel interlocking sheet piling will possibly be chosen.

Any type of sheet piling will require bracing to hold it in position, and the proper erection of this bracing, so as to permit the later carrying up of permanent walls, should receive due consideration. Instead of building them in, leaving a hole to be plugged later, it is generally preferable to strike the braces as the work goes up, replacing same on the inside of the wall.

216. Protection of Adjacent Structures.-The holding and shoring of adjoining buildings generally presents so many elements of risk, that, unless it is a relatively simple operation, this branch of the work had better be entrusted to specialists in that line.

Underpinning where the soil is unyielding can be carried out successfully and without great danger if due precaution is given to the number and length of the different sections which are to be worked on simultaneously. These should not be too close together and generally not in lengths over 6 or 8 ft., and the load of the structure should be brought to bear on the new work before opening up an adjoining section. This is accomplished by means of slim metal wedges inserted between specially prepared stone wedging blocks built into the underpinning and driven home after the masonry has taken a set. If the soil is particularly unyielding, the same results can be obtained by a wedge course of brick inserted by the mason as he tops off the underpinning work. When using the sectional method, little or no timbering will be required beyond an occasional spur brace to overcome tendency of the old wall to slip. If the old wall is in poor condition, or the soil under it inclined to be treacherous, needling of the wall had better be resorted to and the aid of a specialist secured.

22. Rock Excavation.-Rock excavation is carried on by the aid of explosives and in most communities not only is a licensed powder man required to do the shooting, but regulations are also provided covering the manner in which the dynamite may be handled and stored. On small work, hand drills are successfully used, but where the yardage to be removed is great, steam or air drills should be provided. The use of the explosive is to lift the rock slightly and break it up into sizes convenient for disposal. The number and size of the respective charges is dependent upon the surrounding conditions, and the supervision of this class of work should be entrusted only to those who are thoroughly familiar with its possibilities. After being

shattered, the rock is loaded in skips or buckets and removed from the basement by a boom derrick or picked up by a steam shovel and deposited into trucks or cars.

23. Open Caissons.-Caisson excavation may be carried on in the open or by means of locks and compressed air, the latter expedient being adopted only when excessive water conditions preclude the open method.

For building footings, caissons are generally designed circular in form, varying from 4 to 10 ft. in diameter and carried down either to bed rock, or stopped off and belled out on some convenient strata of hardpan. Under the former condition, depths of 100 ft. and upward are sometimes encountered. Excavation is done by hand, the excavated material being lifted to the surface by buckets suspended over the mouth of the well and raised and lowered through the agency of a niggerhead, the mechanism receiving its power through a traction cable lead from a conveniently placed hoisting engine. Ten to fourteen wells comprise a set up and are commonly run from one engine. This provides a constant speed for all the niggerheads, and the individual operator at the head of each well on signal from below raises the filled bucket by taking 2 or 3 wraps of the hoisting line over the niggerhead. The excavation is carried down to a depth of 5 ft. 4 in. and then lagged with 2- or 3-in. matched lumber, the lagging being held in place by metal rings inserted two to each length of lagging. The rings are rolled out of flat bars and made up in two sections to the ring. After being brought to position, the two halves are bolted together at the ends and wedged tightly against the lagging. The excavation then proceeds for another stretch and repeats until the bottom has been reached.

When working through wet ground, bailing may not be sufficient and pumps may be required. For this purpose, steam syphons or pulsometer pumps will be found most convenient. Sections of steel lagging may be required if the ground is very soft, but its use is not always attended with satisfaction. Continued pumping of a well with little or no headway shown is bad practice, and will lead to sure trouble on adjacent wells. When such conditions arise, pumping should be discontinued and every effort first exhausted to stop the inflow of water and sand by tightening up the lagging. An inner set of sufficient length driven ahead of the excavation may make it possible to pass the soft spot. This procedure, however, is at the expense of a reduced area on the caisson, and for that reason may not be permissible. The use of hay or straw for packing back of the wooden lagging will often overcome water difficulties which otherwise seem insurmountable.

wells.

Electric lights and, in some cases, forced ventilation will be required for the workmen at the bottom of the

When wells are belled out, it is not customary to lag the last section but to immediately fill it with concrete as soon as it has been shaped up and cleaned out.

The rings may be salvaged as the concreting is brought up, but the lagging is left in place.

24. Compressed Air Caissons.-In ground conditions where water or quicksand would make open work impractical, compressed air is resorted to. In this work caissons are carried down in the open as far as possible and then an air-lock is installed at the head of the well. Through this vestibule, which by the manipulation of valves is alternately under normal and then at an increased air pressure which varies with the requirements, all workmen and excavated material must pass. The air pressure in the working chamber is kept at a point just sufficient to exclude the incoming water and, to a workman accustomed to it, little or no inconvenience will result.

Experienced men only should be used on this class of work, and every precaution should be taken to see that the compressor plant and all other apparatus is in first-class working order. The use of naked lights should be prohibited, as combustion will be found much more rapid than when exposed under normal pressure.

In the majority of cases, it will be found desirable to start caisson work from the normal ground level rather than to await the completion of basement excavation. The additional expense of hand over steam shovel labor for the yardage included in the caisson tops, will be more than compensated for by the saving in time to the building schedule and also the greater convenience in removing the caisson dirt from the premises.