I. G. Basov, B. L. Stepanov

EXCAVATION OF FROZEN SOIL WITH WEDGE HAMMERS AND IMPACT FROST RIPPERS

(Presented by the Department of Mining Machines and Mine Transport)

Loosening frozen soil with the aid of wedge hammers and ball hammers is one of the simplest and most widely used methods. In this case, the bucket is removed from an excavator equipped with a dragline boom, and an impact working member in the form of a wedge hammer or ball hammer is suspended from the hoisting cable. During operation, the excavator operator raises the hammer to a specified height and then, by allowing it to fall freely, fractures the frozen soil. After the soil has been destroyed across the full width from one excavator position, the excavator moves forward by 0.5–1.5 m, and the cycle is repeated (Fig. 1).

Fig. 1.

Construction organizations in the country use a wide variety of wedge-hammer and ball-hammer designs (Table 1), as well as methods of excavating soil with their aid.

Existing wedge hammers are distinguished as follows:

1. By the shape of the body of the projectile:

a) pyramidal (3, 8, 10, 13, 14, 16, Table 1);

b) in the form of a rectangular parallelepiped (2, 5, 7, 15, Table 1);

c) in the form of a truncated cone (6, Table 1);

d) cylindrical (4, Table 1);

e) cylindrical-conical (17, 18, Table 1)

e) prismatic (9, Table 1).

1. With the teeth of the projectile in the form of:

a) a wedge (2, 3, 7, 8, 10, Table 1);

b) a cone (4, 12, 17, 18, Table 1) or a truncated cone (9).

1. By number of teeth:

a) single-tooth or single-wedge;

b) two-tooth (13, 14, Table 1);

c) single-tooth double-wedge (with a cross-shaped wedge 16, Table 1).

1. By manufacturing technology:

a) cast,

b) welded, filled with cast iron or concrete.

In most wedge hammers the body and working tooth form a single whole, but some are made with an inserted tooth (12, Table 1). The sharpening angle of the working teeth in wedge hammers is 20–65°.

The designs of wedge hammers are, as a rule, the product of the initiative of machine operators in construction organizations, who intuitively select the weight and geometric parameters of the projectiles and make them from available material.

When the depth of soil freezing is small (0.25–0.35 m), wedge hammers weighing 0.4 t (1, Table 1) are used [16] for loosening it; it is indicated that 2–3 blows are required to excavate 1 m². As the freezing depth increases, the weight of the wedge hammers and the required number of blows increase. To loosen 1 m² of soil frozen to 35–45 cm with a wedge hammer weighing 0.9 t, made from a steel billet of square section and a No. 30 channel enclosing it on two sides (2, Table 1), 4–5 blows are required; and with freezing to 45–70 cm, 8–10 blows are required [16].

As practice has shown [7], the use of cast pear-shaped projectiles (6, Table 1) is less expedient than welded ones filled with concrete and having projecting ribs (7, Table 1).

For excavating soil frozen to a depth of 0.5–0.7 m, the Soyuzekskavatsiya trust also used a welded-design wedge hammer (8, Table 1) [20]. Such wedge hammers are usually welded from steel sheet 15 mm thick, coated inside with refractory clay, and filled with cast iron in small portions. In the same trust, wedge hammers of octagonal shape weighing 2 t (9, Table 1) were effectively used [4].

The obelisk-shaped wedge hammer weighing 2.6 t (10, Table 1), used in the Glavvladivostokstroy trust of Dalstroymekhanizatsiya, ensured low productivity, especially on clay soils (20 m³ of loosened category IV soil per shift). In this connection, three new types of wedge hammer were developed there: a triangular one with cut-off ribs and without a core, weighing 2.8 t (11, Table 1); a triangular one with two conical transitions and a core, weighing 3.2 t (12, Table 1); and a round one with two conical transitions and a core, weighing 2.8 t. The highest productivity (88 m³ of loosened category IV soil per shift) was achieved when working with a triangular wedge hammer with a round core, onto which additional ribs of sheet steel up to 30 mm thick were welded [22].

One of the shortcomings of wedge hammers is their overturning when striking the ground. To avoid this, teeth are welded to the edge of the wedge, the working surfaces of which are faced with hard alloy (13, 14, Table 1).

In the Mosenergostroymekhanizatsiya Administration, frozen-soil loosening was carried out with wedge hammers weighing 3 and 4 t with two teeth (14,

Table No. 1

Table 1). When the ground was frozen to less than 1.5 m, three-ton wedge hammers were used. With three blows at the same spot by a wedge hammer falling from a height of 10 m, frozen clayey soil was broken up over the surface within a radius of 0.8–1.0 m and to a depth of 0.6–0.8 m. When freezing extended to a greater depth, four-ton wedge hammers were used; when dropped from a height of 10.8–12.8 m and with the same number of blows, they broke up the soil to a depth of 1.4 m and over the surface within a radius of 1.2–1.4 m [18, 27].

In the construction organizations of Tomsk, loosening of frozen soil was successfully carried out with wedge hammers whose working tooth has an elongated cruciform shape (16, Table 1).

At the Transvodstroy trust [8], cylindrical wedge hammers were used for excavating frozen soil (17, Table 1). The body was made of sheet steel not less than 5 mm thick, and in the middle part from a steel pipe 600 mm in diameter. It was then filled with scrap metal and poured with cast iron or, in extreme cases, with cement mortar.

Table 1 presents the design of another cylindrical wedge hammer [14, 15]. It is made from a section of pipe 500 mm in diameter. Along the axis of the pipe passes a steel rod 100 mm in diameter, the lower end of which is sharpened, while to the upper end, projecting above the body of the wedge hammer, its eye is welded. The wedge hammer is filled with cast iron. When used on an OM-202 excavator, such a wedge hammer weighing 1.7 t gave an average productivity of 100–120 m³/shift, which is almost twice as much as with a three-ton wedge hammer with two teeth [14]. It has been established that the greatest efficiency is achieved when working with a wedge hammer of this design weighing 2.4 t [15]. A drawback of wedge hammers of this type, however, as the author [15] points out, is that they become stuck in the upper layer of thawed soil.

The destruction of frozen soil by wedge hammers is accompanied by considerable losses of impact energy to elastic deformations. Therefore, for effective excavation of frozen soil by this method, it is necessary to increase the energy of a single blow by increasing the weight of the tool and the height from which it is dropped, selecting the parameters so that losses to elastic deformations are minimal.

As the authors [1, 7] indicate, the weight of wedge hammers should not be less than 3.0 t, and the drop height should be 5–6 m.

The ratio between the length of a wedge hammer and its cross section has a significant influence on its operation. The literature [5] mentions that the Leningrad trust Soyuzekskavatsiya carried out studies to determine the optimal ratios between the cross section and length of a wedge hammer, but the results of this work are not known.

Loosening and excavation of soil may be carried out by one excavator or by different excavators. As practice has shown, when the freezing depth is up to 0.8 m, it is expedient to carry out soil loosening and excavation with a single excavator. To ensure two-shift operation of an excavator with a bucket capacity of 0.5 m³, 2.5–3 hours are sufficient for loosening the frozen soil. When the soil is frozen to 1.5 m, it is recommended [18] that the work be carried out by three excavators at once: one is used for breaking up the frozen soil, and two for excavation.

Excavation of soil with wedge hammers is carried out in several ways.

The simplest method is the vertical dropping of the wedge hammer (Fig. 2a). It is accessible to excavator operators of any qualification, but in this case the loosening depth does not exceed 0.6–0.8 m, and productivity is 50–70 m³/shift. In the second method, the wedge hammer is dropped obliquely (Fig. 2, b); in this case it not only breaks off

soil, but also loosens it. Productivity increases to as much as 110 m³/shift. Such work can be performed only by highly qualified excavator operators, since it is difficult to drop the wedge hammer obliquely while controlling only one, and in some cases two, cables [15]. A disadvantage of this method is that, in this case, pieces of frozen soil fly off in different directions. To avoid accidents, a protective screen is placed in front of the excavator windshield, and people are not allowed near the face within a radius of 25–30 m.

When two cables (hoisting and pulling) are used, the wedge hammer is operated in the following sequence. First, a free blow is delivered to the soil (Fig. 2, c), and then, by tightening the pulling cable, the wedge hammer is overturned and soil is broken off (Fig. 2, d). The loosening depth is 1–1.8 m, depending on the spacing of the blows. The method is simple and accessible to excavator operators of average qualification [15]. The use of the pulling cable makes it possible to break frozen soil along the line of the face, to carry out excavation in layers (up to 0.8 m thick), and sharply to reduce cable wear. With this method, clods of earth do not fly off in different directions [8].

Fig. 2.

A major disadvantage of wedge hammers is their tendency to overturn and fall at various angles, which causes a sharp increase in the energy intensity of excavation. One way of eliminating this disadvantage is to use ball hammers. Owing to their spherical form, changes in the position of the tool during falling do not affect the efficiency of the blow. But the impact effect of a ball hammer is considerably less than that of a wedge hammer of the same weight falling from the same height, because of the much larger area of contact with the soil.

Ball hammers are made as steel or cast-iron castings and have a spherical or pear-shaped form (19, 20, Table 1). According to a number of authors [4, 19, 26], a ball hammer should be used in excavating sandy loams and sandy soils, while a wedge hammer should be used in excavating clayey and loamy soils. V. N. Sizov [24] indicates that it is advisable to use a ball hammer when the depth of freezing is up to 0.5 m, while S. F. Gusakov and A. S. Vaigant [8] recommend it even when the depth of freezing is up to 0.9 m. According to S. S. Chelnokov [28], when the soil is not frozen very deeply, its fragmentation by means of a ball hammer during pit excavation makes it possible for even two excavators to work simultaneously.

The main disadvantages of the method of excavating frozen soil with wedge and ball hammers are as follows.

Because of the large dynamic loads, excavators undergo increased wear. The bearing of the verti-

Table No. 2

the walking shaft of the travel mechanism; gear transmissions fail prematurely, cracks form in the excavator undercarriage frame, the gears and the friction mechanism of the traction winches wear out, etc.

During the free fall of the wedge hammer, the hoisting rope twists, and during lifting it untwists. The rope is severely deformed, the regularity of the lay is disturbed, and it quickly fails. Its consumption increases fivefold in comparison with summer excavator operations and reaches 60 kg for every 1000 m³ of excavated frozen soil [4, 6].

As measures undertaken to reduce rope consumption, it is recommended: a) to connect wedge hammers to the rope by means of a ball-and-swivel device [24]; b) to restrain the impact tool from rotating by means of the excavator’s traction rope [18]; c) to use ropes of special lay [13, 16]. In American practice, in order to reduce rope wear and lower the dynamic loads on the boom and other excavator assemblies, shock absorbers in the form of used automobile tires are built in along the length of the rope holding the impact tool; reeving of the rope is also used to prevent it from untwisting [13].

Among the disadvantages of breaking frozen soil with wedge hammers one may also include the large amount of metal required to manufacture the impact tools and the considerable shaking of the ground, which has a harmful effect on nearby structures.

But the principal drawback of using wedge and ball hammers for loosening frozen soil is the low productivity and high energy intensity of the work, since, in order to achieve the required effect, many “superfluous” blows are made and the soil is always broken over an area larger than necessary because the motion of the impact tool is not guided as it falls.

In recent years, impact frost rippers built on tractor bases have begun to become widespread. Such frost rippers are more advanced machines in comparison with wedge hammers on excavators, since their impact tool has guided motion during free fall.

Impact frost rippers are in most cases made by the construction organizations themselves and are distinguished as follows:

1. By the arrangement of the impact equipment:
   a) directly on a tractor-bulldozer;
   b) on a trailer dolly.

2. By the form of the impact member:
   a) with a single-wedge tool (2, 3, Table 2),
   b) with a comb-type working member (1, 4, 5—10, Table 2).

3. By the operating principle of the impact equipment, when:
   a) the wedge-shaped working member is dropped from the required height with simultaneous unwinding of the winch rope,
   b) the wedge-shaped working member is dropped from a specified height with release of the hoisting rope,
   c) blows of a falling weight are delivered to the wedge-shaped working member with the machine stationary or moving continuously.

Among the earliest designs of impact frost rippers is the pile driver of the Lenélektrosetstroy Trust (Fig. 3), whose working member was a toothed ripper (1, Table 2) weighing about 2.0 t, fastened with bolts to the impact hammer of the pile driver. After 3–4 blows of the working member at one place, the soil broke off to a depth of

0.5 m, and the excavator moved on by 20–40 cm. Excavation was carried out in layers. Before loosening the lower layer, the upper one was removed. Productivity was 10–13 m³ of frozen soil in 7 hours of operation [25].

One of the simplest installations, but with higher output, is the installation first manufactured in 1953 according to the design of I. K. Stadnik by the Ukrstroimekhanizatsiya trust [12], which consists of mounted equipment installed on an S-80 tractor.

The mounted equipment consists of a steel wedge weighing about 1.0 t (2, Table 2), runners, and a guide frame made of channel sections 4.2 m long. The guide frame is attached to the housing of the tractor’s rear axle. The runner with the wedge is raised by the cable of the bulldozer winch. The wedge is freely suspended on a pin rigidly connected to the runners. In the lower part of the wedge, lugs are provided for guiding it and eliminating swinging during lifting and lowering. The length of the runner is 1.6 m. This makes it possible to carry out work in trenches and foundation pits to a depth of up to 1.5 m below the bottom of the tractor track, without losing the direction of fall, since the runner does not leave the guides.

Fig. 3.

According to I. L. Kulin [12], when the soil is frozen to 1.0 m, the installation’s productivity over a seven-hour shift was 130–200 m³ of loosened soil; according to L. V. Rogovskii et al. [23], it was only 50 m³/shift.

At the Dubrovskaya Hydroelectric Power Station, K. Gaido, I. Shokotko, and V. Artamonov developed and built a frost-ripping installation similar to the one discussed above [10, 17]. The mounted attachment is installed on a D-147 bulldozer and consists of a frame made of two No. 10 channel sections with their flanges facing each other, and a wedge weighing 1.2 t, which moves by means of a mechanical winch along the frame guides on runners (3, Table 2).

The productivity of the installation in loosening Category IV frozen soil at a freezing depth of 0.5 m is 90–100 m³ per shift.

The main shortcomings of these installations, in the opinion of a number of authors [1, 21, 29], are that they have a low wedge weight (1.0–1.2 t) and a lifting height of up to 4 m, and, as a result, an insignificant energy of a single blow. This makes it possible to break up sandy soils frozen to a depth of up to 0.8 m, and clayey soils only to 0.6 m. The number of lifts per minute with the aid of the winch can be no more than ten. The cable often fails because of its rapid unwinding, and the tractor winches quickly go out of service. The guide frame on the installations is often damaged.

The Laboratory of Earthworks of the Research Institute for Organization, Mechanization, and Technical Assistance of the Academy of Construction and Architecture of the USSR (NIIOMTP), on the basis of a proposal by Candidate of Technical Sciences V. A. Cherkashin, developed mounted equipment for the S-80 tractor. The layout of the installation is presented in Fig. 4 [29, 30].

The mounted equipment consists of a guide frame, hinged to a bracket, with the working member moving along it.

The frame is made in the form of two five-meter uprights of No. 30 channels, connected to one another by three welded pieces of No. 10 angle steel. For greater rigidity, the lower half of each upright has a box section.

The bracket is mounted on the rear part of the tractor. It consists of two vertical uprights (of No. 15 angle steel), two horizontal cross-members of No. 30 channel, two tie rods, and a transverse brace of No. 9 angle steel.

The working member of the installation (4, Table 2) consists of three wedges shaped like triangular pyramids with sharp tips; wedge anvils; a freely falling weight in the form of separate steel or cast-iron plates tightened with a shackle. The shackle, passing through a hole drilled in the plates, also serves for gripping the weight by an automatic lock and lifting it.

The lock acts as a spring latch and has a tailpiece for releasing the weight. When the weight is lifted to the required height, the lock tailpiece catches on the lifting limiter and drops the weight onto the wedge anvil.

Fig. 4.

The weight of the load can vary within the range from 0.5 to 3.0 t, depending on the number of impact plates. By changing the weight of the load and the height to which it is lifted, it is possible to select the optimum amount of work for breaking off a block of frozen soil with one blow under the given conditions.

In the transport position, the working member is raised and secured on the frame by means of two support rods, while the frame itself is secured in the vertical position also by a rod. Before starting operation, the installation’s winch slightly raises the impact working member, the support rods are removed, the wedges are lowered onto the ground surface, and the guide frame is released from the stop. After this, by successively lifting and dropping the load, the wedges are driven into the ground. The breaking away of the split-off block of frozen soil from the mass and its dumping into the excavated space occur owing to the hinged suspension of the guide frame and because the wedges are single-beveled; when driven in, together with the frame they deflect forward toward the splitting plane. The simultaneous driving of three wedges into the ground forms a crack in the soil that passes through all three wedges. The width of the block being broken off is about 1.6 m. Owing to the triangular shape of the wedges’ cross section, the block breaks up into separate pieces during splitting.

The installation is serviced by two people.

The experimental model of the installation provided an output of 100 m³ per shift, with a cost of loosening 1 m³ of frozen soil of 19 kopecks.

Subsequently, the design of the ripper was substantially modified. In the mounted equipment the impact weight was eliminated. The destruction of frozen soil is carried out by a three-wedge impact comb.

(5, Table 2), weighing 3.6 tons, falling along guides from a height of 2.8 m [24]. The teeth of the comb have the shape of four-sided pyramids 1.15–1.3 m long (the middle tooth is longer), with sharp tips. The productivity of the ripper was 200–220 m³/shift, with the cost of ripping 1 m³ of frozen soil being 9.2–10 kopecks [31].

At the Mechanization Administration for Construction and Installation Work of the Tomsk Sovnarkhoz, similar three-wedge frost rippers were created for ripping frozen soil in clay quarries and when digging foundation pits. The mounted equipment, consisting of a vertical guide frame along which the impact working member moves (6, Table 2), is rigidly mounted on the body of the bulldozer’s rear axle.

At the Kuibyshevgidrostroi organization, two designs of frost ripper were developed: one on an S-80 tractor of the T-2750 type, and a towed ripper.

In the T-2750 frost ripper [2, 11], the guide frame, made of channel sections, is mounted on a hinged axle between two brackets that are fastened to the body of the tractor’s rear axle. In the upper part, the frame is attached by two rigid stays to a U-shaped post located at the front of the tractor. The impact comb consists of five steel bars arranged in a row and connected to one another (7, Table 2). Two bars are 1200–1300 mm long, and three are 2000 mm long. The latter are sharpened on two sides. The weight of the comb is 2.7–3.0 tons, and the drop height is 2.5–3 m. The comb is raised by means of the tractor winch through a fourfold tackle.

The device for engaging and releasing the impact comb consists of a roller fixed in the lower part of the block crosshead and a hook hinged in the upper part of the impact comb. When the block crosshead is lowered under the action of its own weight (170 kg), the roller presses back the hook and enters the engaged position, connecting the impact comb with the crosshead. When the upper extreme position is reached, the comb hook is automatically removed from the roller of the block crosshead by means of a lever system. Owing to this, the impact working member falls freely without unwinding the winch cable, as a result of which the impact energy is increased.

The impact comb, owing to the coulisse mechanism, always assumes a vertical position during operation, which makes it possible to excavate soil at any inclination of the tractor.

To preserve the longitudinal stability of the tractor, a counterweight (in the form of a box with ballast) weighing 1.2 tons is installed in its front part. In order to reduce the load on the body of the rear axle during transport, short metal skids are placed under the impact comb.

During operation, the ripper cuts parallel furrows 0.5 m long. Productivity at a freezing depth of 0.7 m was 175–193 m³/shift. The installation is operated by one tractor driver.

In the towed version [2, 24], the frost ripper is mounted on runners and is hitched to the rear of the tractor. The ripper consists of an impact comb weighing 2.75–3.0 tons, an automatic device for engaging it, a guide frame, and a counterweight weighing 1.2 tons. The frame, 5 m high and 1.33 m wide, is made of two No. 30 channel sections. The free drop height of the comb is 2.5–3 m. Five to ten drops are made per minute.

When moving over long distances, the guide frame is brought into an inclined position in order to reduce the height of the machine. The machine is operated by one tractor driver. The shift productivity of ripping is 175–220 m³ of frozen soil; the cost of ripping 1 m³ is 9–11 kopecks, and the labor input is 0.004–0.005 man-days/m³ [24].

At the Construction Administration of the Dubrovka Hydroelectric Power Station, I. I. Shokotko and V. N. Kharkov developed and built a tractor-towed ripper, somewhat different from the ripper of Kuibyshevgidrostroi [9]. It consists of a dragline bucket mounted on skids, which are moved by bulldozers with the blade removed. During operation the bulldozer moves in reverse. The skids are made of I-beams. The guides of the dragline bucket, 6 m long, have the shape of the letter “P” and are made of No. 30 channels. Angles are welded to the guides; these enter corresponding recesses (slots) on the side faces of the rake. The lower part of the dragline-bucket frame is fastened movably to the skids. This makes it possible, during transport, to place it in a horizontal position by means of the bulldozer winch. In this position the upper part of the guides rests on a supporting post made on the middle runners of the skids.

The impact rake is made from old wagon axles; the rake teeth are sharpened. The working teeth of the rake are 70 cm longer than the inserts and are spaced from one another at a distance equal to one or two axle diameters. The weight of the rake is 2.5 t (8, Table 2).

To grip the impact rake during lifting and to uncouple it during release, there is a coupling device controlled from the tractor operator’s cab. Freed from the rope, the rake falls downward and loosens the frozen soil. Following the rake, owing to the reverse motion of the winch, the hook descends under its own weight and, upon reaching the rake shaft, engages with it.

In the installation the design of the bulldozer winch has not been altered, which makes it possible to use it both for its direct purpose and for loosening soil. Connecting the ripper to the bulldozer takes 15–20 min. The ripper can operate with the guides inclined up to 30°. The vertical position of the guides is fixed by a special device.

The output of the ripper is 220–260 m³ of frozen soil per shift at a frost depth of 0.7 m. The cost of loosening 1 m³ of frozen soil is 7 kopecks.

In 1959, at the Mechanization Administration of the former Ulyanovsk Council of National Economy, a three-wedge frost ripper of the NIIOMTP design was manufactured. But when this installation was operating, during the fall of the ripper load, the entire machine was subjected to strong shaking, which quickly put individual tractor assemblies out of order and made normal work by the tractor operator impossible. In connection with this, the Administration developed the design of a ripper mounted on towed metal skids [21].

The guide uprights consist of two halves and fold on hinges, which reduces the height of the ripper in the transport position to 3 m. Raising and lowering the upper half of the uprights is performed by the tractor operator using the second drum of the scraper winch.

To fix the rake in the raised position and release it, the installation has an automatic double-sided catch of the lever-spring type with a floating hook-lock.

The output of the towed ripper, taking into account all auxiliary operations under housing-construction conditions, averaged 40 m³ per shift of frozen soil of different categories at a frost depth of up to 0.8–1.0 m. The installation is operated by one tractor operator.

In the winter season of 1960–1961, 5 such installations operated on the construction sites of the Sovnarkhoz, and in 1961–1962, 9. With each installation there worked one excavator with a bucket capacity of 0.25–0.35 m³, equipped with a backhoe.

VNIIStroydormash has developed a machine for continuous breaking of frozen soil [3].

The mounted equipment is installed on an S-100 tractor. The working member consists of four single-bevel wedges rigidly connected with guide rods, which are joined in pairs (10, Table 2). The wedges are driven into the soil by two loads moving along the guides, 2.0 tons each. The lifting height of the load is 2.0–3.1 m. The guides are four telescopic rods, hinged to the tractor. The impact parts of the installation are lifted by a two-drum winch with multiple-disk friction clutches. For coupling the load with the working member and raising it to the upper position, there is a special gripping mechanism.

Before work begins, the working members are set on the surface of the frozen soil. The load is then dropped onto them successively (14–17 blows/min). Penetration of the wedges and destruction of the soil to a depth of up to 1.3 m in one pass, with a width of the destroyed strip of 1.5–3 m, take place while the tractor moves continuously at a speed of 30 m/h. To reduce the speed of travel during operation, a speed reducer is installed on the tractor.

When the loads fall and are lifted, limit switches mounted on the working members and the rear suspension of the guides are closed; these respectively engage or disengage the disks of the normally closed friction clutches with electrohydraulic control.

After the soil has been destroyed, the working members are coupled to the loads by special gripping devices, lifted (independently of one another), and set in another position. The installation is operated by one person from the tractor cab or from a remote control panel. The output of the installation is 280–350 m³/shift.

As practice has shown, excavation of frozen soil by the method of large-block breaking with wedge-type frost rippers is one of the progressive, high-productivity methods. However, the designs of existing machines are still very imperfect; in most cases they are made by handicraft methods. Because of the frequent lifting of the load, the tractor winches quickly fail, gears and friction transmissions wear out, etc. [1].

On the basis of a review of works dealing with the designs of wedge-hammer impact frost rippers based on tractors, as well as the results of their operation, the following conclusions may be drawn.

1. The use of wedge-hammers on excavators as impact machines for destroying frozen soil is low-productivity and should be limited, in view of the rapid disabling of excavators.

2. Impact frost rippers based on tractors should find wider application. But in order to develop recommendations for selecting an expedient design of such a machine, studies must be carried out on:

a) a method for the most complete use of the kinetic energy of the falling load for destroying frozen soil;

b) the optimal parameters of the impact equipment (weight, geometric shape and dimensions, drop height, etc.);

c) a method of isolating the harmful influence of the dynamic forces from the falling load on the structure of the mounted equipment and the tractor;

d) a method for carrying out the operations of lifting the impact load.

References

1. V. D. Abezgauz, M. I. Galperin. Excavation of frozen soils in mechanical trench digging. Gostoptekhizdat, Moscow, 1962.

2. I. D. Aleshin. Mechanical ripper T-2750 for loosening frozen soil. Installation and Specialized Works in Construction, No. 5, 1960.

3. V. P. Balandin. A new machine for excavating frozen soils by splitting. Construction and Road-Building Machines, No. 12, 1963.

4. G. V. Verdnikov. Basic requirements imposed on the excavation of frozen soils. Excavation of Frozen Soils by Cutting and Impact (conference proceedings), Moscow, 1955.

5. M. I. Galperin. Analysis of existing mechanisms for excavating frozen soils by cutting and impact. Excavation of Frozen Soils by Cutting and Impact (conference proceedings), Moscow, 1955.

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8. S. F. Gusakov, A. S. Vaiogant. Earthwork production in winter. Construction Industry, No. 9, 1956.

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10. A wedge for loosening frozen soil. Stroitel’, No. 2, 1957.

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13. V. N. Lofitskii. Winter earthworks in hydroelectric-power construction. Moscow–Leningrad, Gosenergoizdat, 1961.

14. V. K. Lyakhov. From experience in excavating frozen soil with a wedge-drop hammer. Mechanization of Construction, No. 2, 1955.

15. V. K. Lyakhov. Excavation of frozen soil with wedge-drop hammers. Mechanization of Construction, No. 10, 1955.

16. F. N. Malina. Experience in excavating frozen soils with small-bucket excavators. Mechanization of Construction, No. 3, 1952.

17. T. V. Miklashevskaya. Principal trends in the technology of frozen-soil excavation. Academy of Sciences of the USSR, VNIITI, Moscow, 1960.

18. A. I. Miloslavskii, M. M. Trakhtenberg. From experience in winter soil excavation. Mechanization of Construction, No. 11, 1955.

19. B. A. Nikolaev, M. I. Galperin. Mechanization of frozen-soil excavation. Construction of Oil-Industry Enterprises, No. 11, 1957.

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