RU2344228C2 - Method and device of dynamic ground compaction - Google Patents

Abstract

FIELD: construction, road construction.

SUBSTANCE: at least, one rope (3) is fastened to fright (4) being on the ground, through the releasable connection (7). Pulling effort is applied to the rope to lift fright to the given height. The pulling effort is terminated or minimised to start moving the fright downwards, which is followed by the rope. The connection is released during fright moving downwards.

EFFECT: effective compaction of ground.

9 cl, 5 dwg

Description

The present invention relates to technologies for dynamic soil compaction. These technologies are used to improve the structural characteristics of the soil, in particular, before construction work.

Dynamic compaction treatment increases the density of the soil to a great depth by means of very high energy waves. It includes the use of large loads, usually from 10 to 100 tons, falling from a height of mainly 10-40 meters. The location of impact points on the ground and other processing parameters (energy, phase, periods of no exposure) depends on the characteristics of the soil being cultivated and, possibly, on the measurement results obtained in the test area. These parameters are determined in advance based on the required soil characteristics.

Such soil treatment is usually used for building foundations or for obtaining large, stabilized areas in embankments or loosened soil.

The following two general types of dynamic soil compaction methods can be distinguished:

1) A method with pulling cables.

Rope bucket excavators used for excavation are often equipped with winches that have a gripper that provides the so-called “free fall” function. Such a device can be used for dynamic soil compaction by attaching a sealing weight to one or more winch cables. After turning on the winch and lifting the load to the required height, the grip is opened and the load falls so that it pulls the cable from the winch drum along with it. After the impact, the winches are braked to stop their rotation, the cables rewind again and resume a new cycle.

The disadvantage of the above method is that when using devices available on the market for civil engineering, it is observed that the energy transmitted to the ground upon impact is only 50-60% of the potential energy accumulated when lifting a load. Such low efficiency results from friction losses and inertia of cables and winches. This method can only be applied by using one cable per winch (without increasing the winch effort) and one layer of cable on the winch drum. In practice, this limits the fall height to approximately 25 m and the weight of the sealing load to approximately 25 tons. In accordance with this, the energy of one impact is mostly 60% × 25000 × 9.81 × 25≈3700 kJ.

2) Free fall method

To eliminate poor performance in the fall of the above method, it is possible to use a lifting device equipped with a connecting device that can be disconnected under load and which is located between the sealing weight and the cables. Such a connecting device may be of the type of hook, such as used for towing. It can also be a specially designed hydraulic clamp. The sealing load is lifted to the required height where the winches are stopped, and then the hook or clamp releases the load, which really falls freely.

The main advantage of this method is its high efficiency, since the impact energy is equal to the potential energy received as a result of the lift. In addition, it is possible to use block systems to multiply the pulling force exerted by the winches. You can also use more than one layer of cable on the winch drum. Impact energy is in principle limited by the stability of the lifting device under load.

However, this method also has several disadvantages. When the connecting means is disconnected, the elastic strain energy accumulated in the device and in the cables when lifting the load is suddenly transferred to the connecting device mainly under the influence of the cable reactions. The moving parts making up the connecting device and possibly the block systems experience a push up with substantial energy. They may also experience a side impact due to the asymmetry of the system. Such a reaction can cause various problems, such as the descent of cables from guides, impacts on the crane structure, etc. This phenomenon must be compensated either by increasing the weight of the moving parts to approximately 20% of the weight of the freed load, which impairs the overall efficiency, or using an external strapping to limit the movement of the connecting device.

In addition, lowering the connecting device for reconnecting with the load on the ground takes considerable time, because it depends on the speed capabilities of unloaded winches, which are usually low. In the best case, it can be expected that the lowering time is in the same order as the lifting time. Therefore, the implementation of this second method takes a relatively long time.

An object of the present invention is to remedy the drawbacks of the prior art described above.

Thus, in the invention, the problem is solved by a method of compaction of the soil, in which:

- connect at least one cable with a load lying on the ground, using a detachable means of connection;

- apply traction to the cable to lift the load to the desired height;

- reduce the indicated pulling force to start moving down the load, followed by a cable;

- disconnect the connection means when the load moves down.

Lifting is carried out by means of one or several winches of the type of the system with a "free fall" (as in the methods of the prior art, by pulling the cables), possibly using blocks to multiply the winch effort. The sealing load is suspended on the lower unit or directly on the winch cable through a releasable connection means, for example, a hook or a clamp. The connection means is opened after a certain downward speed has been reached, as a result of which the connecting part, which remains fixed on the cable, does not experience a jerk up. This prevents structural damage and does not require the use of external strapping systems. In addition, the speed when moving down the means of connection and the cable during the release of the load reduces the time required to transfer the means of connection back to the position of the cargo after it falls to the ground.

The present invention also relates to a soil compaction apparatus comprising a crane arm, winch means, at least one cable extended from the winch means around a deflection pulley mounted on top of a crane arm, a detachable coupling means for connecting the cable to the load and control means to turn on the winch means to lift the load from the ground to the required height, reduce the traction force applied by the winch means to initiate the downward movement of the load, followed by the cable, and release dstva connection while cargo traffic down.

The present invention is illustrated by drawings, on which:

figure 1-4 are side views of a device for dynamic soil compaction at different stages of the implementation of the method in accordance with the invention;

5 is an example of a detachable connection means used in such a device.

The soil compaction apparatus shown in FIGS. 1-4 has a vehicle structure 1 on which a crane arm 2 is mounted. One or more cables 3 are used to lift a heavy load 4 (> 10 tons) from the ground level to a predetermined discharge level Н0 (> 10 m). Each hoisting cable 3 is wound on a winch drum 5 mounted on the structure 1 and rejected by a pulley 6 mounted on the top of the crane boom 2.

A detachable connecting device 7, schematically shown in FIGS. 1-4, is located between the lifting cable (s) 3 and the sealing weight 4.

In the embodiment shown in figures 1-4, the device further comprises a system of 8 blocks, through which the lifting cable 3 is pulled between the deflection pulley 6 and the detachable connection device 7. Such a system 8 may include an upper pulley block 9 mounted next to the top of the crane jib 2 and a lower pulley block 10, the frame of which is connected to the connection device 7. The cable 3 is installed on the pulleys of blocks 9, 10 to multiply the lifting force exerted by the winch 5.

In other preferred embodiments of the invention, the hoisting cable 3 can be directly attached to the releasable coupling device 7.

An example embodiment of a detachable connection device is shown in Fig.5. In this embodiment, a socket 12 is provided on the upper surface of the sealing cargo for mounting a hydraulic clamp 13. The socket 12 has a wide central hole with an upper conical section that extends outward towards the upper surface to center the clamp 13 when lowering it, for properly install it inside the slot. In the lower part of the socket 12, its central hole expands, forming a recess 14, in which the clip 13 can be installed.

The clamp 13 is equipped with a bracket 15, designed to connect with the block 10 of the lower pulley of the system 8 blocks (or directly with the cable 3). A plurality of cam elements 16 are articulated on the bottom of the bracket 15. These cam elements 16 are mounted symmetrically about a vertical axis. In their lower part, they have a conical external shape, which corresponds to a recess 14 made in the socket 12. Each pair of opposing cam elements 16 is driven by a hydraulic jack 17 through a lever mechanism. This mechanism contains a pair of rods 18, each of which is articulated at its outer end with one of the cam elements 16 around a horizontal axis. Two rods 18 are also articulated together around a horizontal axis that intersects the vertical axis of symmetry of device 7. The jack 17 is located vertically. When it is extended, the articulation point between the two rods 18 is lowered, as a result of which the cam elements 16 are moved apart from each other to the clamping position in which they are pressed against the socket 12 inside the recess 14. When the jack 17 is pulled in, the articulation point between the two rods 18 rises, bringing the cam elements 16 are closer to each other to disconnect the connection, as a result of which the clamp 13 and the socket 12 are disconnected from each other.

The jack 17 of the detachable clamp 13 is driven by a control unit (not shown) to obtain the operating sequence described below, together with the winch 5.

After determining the structure of impacts on the ground and the sequence of impacts, the device and the load 4 are installed in the first position. The clamp 13 is lowered and controlled in such a way as to hook the load 4 laid on the ground, as shown in figure 1. The winch 5 is then turned on to lift the load 4 to a predetermined height H0, as shown in FIG.

At this point, significant potential energy is accumulated, M × g × H0, where M represents the weight of the load 4. Ideally, 100% of the potential energy would be transferred to the ground when the load fell. In addition, in the position shown in figure 2, in the lifting cable 3 and in the design of the device accumulates significant energy of elastic deformation, in particular, in the boom 2 of the crane.

The downward movement of the load from the position shown in figure 2, is performed using two phases.

During the first phase, the winch 5 is controlled in such a way that it allows the drum to unwind, while the clamp 13 is not yet open. This eliminates or significantly reduces the traction exerted by the winch 5. The first phase is performed until the load 4 reaches a certain speed v when moving down, as shown in FIG. 3. At this moment, the second phase begins by disconnecting the clamp 13, which allows the load 4 to freely fall to the ground.

Since the load 4 and the clamp 13 already has a certain speed v when the clamp is opened, the clamp 13 and the lower part 10 of the block system 8 do not experience a push upward as a result of the sudden release of the elastic strain energy accumulated in the cable 3 and in the crane arm 2. This eliminates the disadvantages of the known free fall methods of the prior art.

In the second phase, the rotation of the winch drum 5 is inhibited by means of an appropriate coupling means (not shown) for controlling the downward speed v 'of the connecting device 7 while lowering it to the load 4. This makes it possible to adjust the time required to reconnect the clip 13 to the load 4, and thus optimize the cycle time.

After reconnecting the clamp 13, the next cycle can be performed in the same position on the ground or after moving the device and load in the lateral direction.

There are various ways for the control unit to determine the moment at which the clamp 13 must be opened after the start of the movement of the load down.

In a simple embodiment, the connection device 7 is opened (for example, by retracting the hydraulic device 17 shown in FIG. 5) at a predetermined point in time t, after the winch drum 5 begins to unwind.

Alternatively, a position sensor may be installed on the connection device. The connection device 7 is then opened after it moves down a certain distance h (or, equivalently, when it reaches a height H0-h).

In another embodiment, a speed sensor is installed on the connection device 7, which monitors the rate of fall of the load in the first phase. In this case, the release condition occurs when the measured fall rate reaches a predetermined threshold value v, while the jack 17 is retracted in accordance with the detection of this condition by the control unit.

Typical values of the above threshold values are t≈0.5 s, h≈1 m, v≈4 m / s. Since the lifting height H0 is usually more than 10 meters (for example, H0 = 25 m), it can be seen that the sealing load 4 will lose no more than a few percent of its potential energy in the first phase of the cycle, which also receives a certain downward speed v. Therefore, the total energy transferred to the ground during the impact will be very close to the original potential energy. This means that the efficiency of the method is very high, the inertia of the winch and the structure will appear only in the short first phase.

Such high efficiency is achieved without the risk of damage to the structure as a result of a jerk up of the clamp 13, the cable and the pulley block 10 when dumping the load 4, with a relatively short cycle time.

Claims (9)

1. A method of compaction of the soil, in which at least one cable is attached to a load lying on the ground through a detachable connection means, a pulling force is applied to the cable to lift the load to a predetermined height, the indicated lifting force is reduced to start the load moving downward, followed by a cable, and release the connection means in response to the detection of a condition that the speed of falling of the load reaches a predetermined threshold value when the load moves down. 2. The method according to claim 1, in which the cable is stretched around the deflection pulley on top of the crane jib between the detachable connection means and the winch used to apply traction. 3. The method according to claim 2, in which the cable is braked on the winch after disconnecting the connection means for controlling the downward movement of the part of the connection means that remains connected to the cable. 4. The method according to claim 2, in which the cable is additionally passed through a block system between the deflection pulley and detachable connection means. 5. The method according to claim 1, in which the load has a weight of at least 10 tons, and the predetermined height is at least 10 m 6. A device for compaction of the soil, comprising a boom of a crane, a winch, at least one cable stretched from a winch around a deflection pulley on top of a crane boom, a detachable connection means for connecting the cable to the load, and also control means for switching on winches for lifting loads from the ground to a predetermined height, reducing the pulling force applied by the winch to start moving down the load, followed by a cable, and a control unit for controlling the disconnection of the connection means, in t to detect that the rate of fall of the load reaches a predetermined threshold value when the load moves down. 7. The device according to claim 6, containing braking means that interacts with the winch means, which is included by the control means for braking the cable, after disconnecting the connecting means, for controlling the downward movement of the part of the connecting means that remains connected to the cable. 8. The device according to claim 6, containing a system of blocks into which the cable is laid between the deflection pulley and detachable connection means. 9. The device according to claim 6, containing a load weighing at least 10 tons, and the top of the crane boom is located at a height of at least 10 m above the ground.

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