JPS6149018A - Construction of sand pile by casing shorten than improved length - Google Patents

Abstract

PURPOSE:To cut down the cost of construction by a method in which a casing shorter than the length of ground to be improved is penetrated into soft ground, water and sand are supplied into the casing, and the casing is pulled up while regulating the pressure of air in the casing. CONSTITUTION:A casing 1, whose upper end is closed and the axial length is made shorter than the length of ground to be improved, is penetrated to a given depth into soft ground by a penetrator 3 through a power transmitter lever 2. Sand with water is supplied through a supply pipe 6 into the casing 1, and while controlling a pressure regulating valve inserted into a discharge pipe 7, the casing 1 is pulled up to form a given diameter sand pile. Used compressed air is recovered through the discharge pipe 7.

Description

DETAILED DESCRIPTION OF THE INVENTION ■Objective of the invention Industrial field of application The method of the present invention relates to a construction method for creating a large number of sand piles etc. in the ground used in soft ground improvement work.

Conventional technology When performing ground improvement by applying a large number of sand piles at depth B to soft ground at the bottom of water depth A, conventional construction methods:
With the casing driven to the depth of the pile bottom in the underwater ground,
the length such that the top of the casing is above the water surface, i.e.
Since a casing with a length of at least A x B was used, (a) a large buoyant force was applied to the casing, and it was necessary to make the penetrating machine heavier to cancel out the buoyant force, and the penetrating machine as a whole ((long and Since it is heavy, a vibrator or impact machine with a large capacity is required. ((b) The guide leader of the penetration device must also be strong and large. (...) Penetration The capacity of the winch to suspend and lift the equipment needs to be large enough to accommodate this. (d) As a result, problems arise with the stability of the construction machine, so a large machine should be introduced as much as possible. Inefficient and uneconomical construction was required.

In addition, when performing soft ground improvement work using sand piles on land, conventionally, the length of the casing is at least longer than the pile bottom depth B, so the mass is large and the above-mentioned disadvantages can be avoided. (e) An operating pile that discharges the sand, etc. supplied into the casing into the void created by pulling out the casing for an appropriate length, and then re-penetrates the casing and bulges the discharged sand, etc. into the compacted ground; This is a construction method in which the so-called Composer method is repeated upward in sequence, and sand, etc., is forcibly discharged and pushed out from the bottom of the casing into the soft ground using a vibrating body installed in the casing, a screw, a vertically operating extrusion mechanism, etc., and then compacted. In the process of repeated operation cycles, a large amount of driving energy is required to create sand piles, especially to create piles with enlarged diameter.

Furthermore, the sand, etc. for building the pile mentioned above is once transported up to the hopper at the top of the casing and refilled inside the casing, so (f) when the length of the casing is long, it is necessary to lift it to a high place. Therefore, whether it is a "batch type" using elevating packets or a "real time type" using a pressure pipe, a considerable amount of power is required.

Recently, as a countermeasure for this, an underwater soil improvement method has been developed in which the length of the casing is made slightly longer than the soil improvement depth B, and the length of the water depth A is covered by the length of an impact transmission rod equipped with a vibrohammer. For example, the hopper for replenishing sand etc. into the casing can be mounted as low as possible to reduce the mass of the penetrating device and its driving energy. Driving underwater drain piles by matching the weight and changing the mutual fixing position of the impact transmission rod and casing to shorten the length and height of the leader and reduce weight. A method (see Japanese Patent Publication No. 49-1084) has been proposed.

In addition, as a method of creating large-diameter piles by bulging sand discharged from the casing into soft ground, sand, etc. is mixed with transportation fluid, and the sand, etc. is separated as it flows through the casing. By this, the casing is replenished with sand, etc., and by controlling the pressure of the fluid, pressure is applied to the sand, etc. discharged from the lower end of the casing into the ground, and forced IC extrusion and compaction are performed against the earth pressure. A sand pile construction method (JP-A-53-125309 or JP-A-53-145311) aims to save driving energy of the casing and obtain economic effects by controlling the pile diameter. (see official bulletin) are also published.

However, in any case, in the conventional method, the length of the casing in the penetration device is actually somewhat longer than the ground improvement depth B, and therefore the difference in degree is Even if there were, we could not solve the problems listed in items (a) to (f) above, and as a solution, we propose the technical idea of using a casing with a length shorter than the length of B above. There was nothing.

Problem 1 to be Solved by the Invention Therefore, the method of the present invention attempts to provide a new construction method that can eliminate and improve the above-mentioned disadvantages of the conventional sand pile construction method.

(B) Means for Solving the Constituent Problems of the Invention The method of the present invention is as follows: (1) In a method of driving a sandpile at a predetermined depth in soft ground, the casing for ground penetration is of a closed type at the upper end. The axial length is made shorter than the length corresponding to the soil improvement depth, and the penetration means provided at the upper position is connected by a power transmission rod, and inside the casing,
A pipe for replenishing sand, etc. mixed with the transportation fluid, and a pipe for discharging the fluid from which sand, etc. has been separated in the same casing, or a fluid supply pipe for adjusting the internal pressure of the casing, are connected to each other, This is an improved casing that is shorter than the improved length, characterized by draining and filling the void created in the ground below by pulling out the casing that has penetrated to a predetermined depth. How to construct.

(2) The length of the power transmission rod is at least longer than the soil improvement depth or the soil improvement depth plus the water depth minus the axial length of the casing. 1) Method of sand pie/l'll'ii work with a casing shorter than the improved length.

(3) Sand, etc. refers to sand-like granular materials such as sand, gravel, crushed stone, slag, lime, cement, etc., or a mixture thereof;
The transport fluid for this consists of using compressed air.'' - A method of constructing sand piles, etc. with a casing shorter than the improved length, as described in sections (1) and (2).

(4) The sand, etc. is one of sand-like granular materials such as sand, gravel, crushed stone, ore slag, or a mixture thereof, and the transport fluid is a small amount of water. A method of constructing sand piles, etc. using a casing shorter than the improved length described in Section 1.

(5) A pressure regulating means is inserted in the middle of the transportation fluid discharge pipe or fluid supply pipe, and the internal pressure of the casing is adjusted by controlling the means, and the pile is formed by sand etc. discharged into the ground soil. A method of constructing piles or the like with a casing shorter than the improved length, as described in items (]) to (4) above, which comprises controlling the diameter or density of the casing.

bitter.

In other words, the function of the casing in conventional construction methods is focused on making a hole in soft ground and protecting the sand, etc. stored inside the hole from the ground soil, so the length of the casing is longer than the improved construction length B. It is understood that a long one was also used.

When construction is carried out over water, the length corresponding to the water depth A is added to the length, so the length becomes even larger, and the above-mentioned problems become more noticeable. Therefore, the basic technical idea of the method of the present invention is that rather than requiring the casing to function as a protection pipe for sand, etc., it emphasizes its function as a discharge pipe for sand, etc. It is required to ensure sufficient space and axial length to separate the sand, etc. to be replenished, and to provide a diameter necessary to create a sandpile of the required diameter.

In the method of the present invention, it is sufficient to create a sand pile if sand or the like is replenished by some means through the casing trench serving as a discharge pipe.

Operation (a) Dry construction method After penetrating the casing into the ground to a predetermined depth while detecting the depth of the lower end of the casing using a depth gauge, sand, etc. is placed on compressed air and transported to the upper part of the casing through a supply pipe, where it is Separate from air. Separated sand, etc. is stored and replenished in the lower part of the casing, and compressed air is discharged or recovered from the recovery pipe.

In this way, by gradually pulling out the casing while maintaining the inside of the casing in a pressurized state, the sand, etc. stored in the lower end of the casing is discharged into the ground, while the sand, etc. is subsequently replenished into the casing. However, a sandpile is formed at the site where the lower end of the casing has been pulled out. At this time, the amount of sand discharged into the ground from the lower end opening of the casing can be detected using a sand level meter. By performing the above operations in a trench near the ground surface, a sandpile of a predetermined depth is created. In addition, there is the so-called composite method, in which the casing is pulled out for a certain length, then re-penetrated to an appropriate depth, and these operations are repeated. There is also a method of creating a sand pile by moving the sand discharge/compaction member downward.

In these construction methods, sand, etc. is fed into the casing through a supply pipe, and compressed air is exhausted through an exhaust pipe. At this time, by controlling the recovery air pressure of the exhaust pipe, the air pressure at the lower end of the pressurized casing By making it correspond to the earth pressure at the depth of the lower end of the pipe (in the case of improving the water bottom ground surface, the pressure that is the sum of the water pressure for the water depth and the earth pressure up to the depth of the lower end of the pipe below the water bottom ground surface), the diameter of the constructed pile can be adjusted. Take control. In other words, by suppressing the air pressure at the bottom end of the pipe to exceed the active earth pressure at the depth of the bottom end of the pipe and below the passive earth pressure,
By creating a sandpile equal to the diameter of the pipe and adjusting the air pressure at the bottom end of the pipe to be greater than the active earth pressure at the depth at the bottom end of the pipe, it is possible to create a sandpile with a diameter larger than the diameter of the pipe. can.

(b) Wet construction method The amount of water added is sent to the casing-F section in a fluid state using a replenishment pipe. On the other hand, compressed air may be supplied from a fluid supply pipe. In this way, by filling the casing with water and then gradually pulling out the casing, the filled water is discharged from the lower end, forming a sandpile in the ground due to the amount of water added. do.

In particular, when the amount of water added is such that the water content ratio is near saturation, a vibrator (or impact machine) is used to maintain the fluid state by applying an external force such as vibration. When activated, the amount of water added can be handled as a fluid, allowing smooth discharge from the lower end of the casing and making it easier to adjust the amount of water discharged. There is no fear that the diameter of the sand pile created by adding water in this amount will become narrower later.

In the above case, a kind of on-off valve is provided at the lower end of the casing,
It is also possible to control the discharge flow rate by adjusting the opening degree, and by using such an on-off valve, once the valve is closed, compressed air from the fluid supply pipe is added to the amount of water filled into the casing. The air pressure can also be used to assist in controlling the discharge flow rate of the amount of water added by applying the adjustment pressure and opening the on-off valve.

In addition, the total pressure of the pressure on the lower end surface of the pipe due to water sand inside the casing and the compressed air pressure from the fluid supply pipe is made to correspond to the earth pressure at the depth of the lower end of the pipe, and the total pressure exceeds the active earth pressure at the depth of the lower end of the pipe and is By controlling the pressure to less than the passive earth pressure, it is possible to create a sandpile equal to the diameter of the pipe, and by controlling it to a level greater than or equal to the passive earth pressure at the depth of the lower end of the pipe, it is possible to create a sandpile larger than the diameter of the pipe.

In addition, in the case of wet construction, there is no need for forced sand discharge and compaction means as in the dry construction described above, and the casing is generally not re-penetrated.

Example 1 Figure 1(a) shows a construction machine (
This is a schematic side view of a marine construction vessel (in this example, a marine construction vessel). In the figure, 1 indicates a casing made of a cylindrical steel pipe with a closed top end, and the inner space is large enough to separate sand, etc. to be pneumatically blown from the air flow. The length is almost independent of the soft ground improvement depth. Moreover, it is preferable that the inner diameter is larger than a fraction of the maximum diameter of the constructed pile.

The lower end opening may be provided with an opening/closing lid to prevent ground soil from entering during the casing penetration operation.

Reference numeral 2 denotes a power transmission rod that connects the penetrating machine 3 and the casing 1, and transmits the vibrations of the penetrating machine 3 to the casing 1 to pawn the pipe into soft ground to a predetermined depth. At this time, the length of the transmission rod 2 is determined to such an extent that the penetrating device 3 can be positioned above the ground or water surface with a sufficient margin. The same rod is ■
Shaped steel 1, such as shaped steel or H-shaped steel, may be a steel pipe, and its length is the maximum pond improvement depth minus the length of the casing, or in the case of construction over water, the length plus the water depth. Generally, it is slightly longer than that.

If the penetration machine is designed to be usable underwater, there is no need to add a depth section. The cross-sectional area of the transmission rod 2 depends on the required strength, but it is preferable that it is not too large.If a steel pipe is used, the upper and lower ends should be open. It is desirable that penetration of the transmission rod 2 into the ground does not create unnecessary holes in the ground and push the soil there to the side. [Refer to section 2 (b) Dotted line display] .

Reference numeral 3 denotes a penetrating machine, which is normally fixed to the upper end of the power transmission rod 2, but as shown in Fig. 11b), the relative fixing position between it and the transmission rod 2 can be changed, and the length of the leader described later can be changed. There are also ways to shorten the length. Generally, a vibrator or an impact machine is used as the penetrating machine 3.

4 is a leader that guides and supports the transmission rod 2 and the cable ring 1 connected to this in the upward and downward directions; it is made of wood, and is installed on one side of the work boat in the +4 example. Of course, when working on land, the length of the leader 4 provided on the tall roller clay 7, at least the length of the case/
The length of the ring 1 in the ・h11 direction must be longer than the length of the power transmission rod 2, the penetrator 3, and the shock absorber 5 connected in series, and a pulley is pivotally supported at the top of the rod and attached to the shock absorber 5. A wire rope connected to the penetrating device consisting of the members 1 to 3 and 5 is looped through the U-shaped pulley, and the other end is tied to a separately installed winch drum, so that the penetrating device is connected to the leader 4Krr3. hi, lift it downwards so that it can be hung. Therefore, guide leader 4
This makes it possible to make the leader lighter as it does not need to support the weight of a casing of at least the same length as the soil improvement depth, allowing for a correspondingly lower level of structure and strength. This is especially effective when performing construction on water, since it is not necessary to additionally support the weight of the water-based casing. Furthermore, as shown in FIG. 1(b), if the fixed position between the penetrator 3 and the transmission rod 2 can be changed, the length of the leader 4 can be transmitted to the axial length of the casing 1. Since it is possible to make it shorter than the length of the rod 2 etc., it can be further downsized, which not only improves the stability and maneuverability of the construction machine, but also reduces the size of the construction machine as a whole. It will also be possible to do so. If a submersible penetrator is used, the leader will extend into the water, providing even greater stability.

As explained above, since the weight of the entire penetrating device can be reduced, the capacity of the penetrating device 3 and the power of the winch for driving the device can be reduced accordingly, and the driving force can be reduced accordingly. Energy can be saved.

In addition, in the case of construction on water, the casing is shorter than the construction improvement length, and the magnitude of the buoyancy generated from it can be saved, so it is possible to reduce the driving force by that amount.

Reference numeral 5 denotes a shock absorber, which constitutes a vibration damping mechanism by combining coil springs, rubber, etc., and prevents vibrations and shocks from the penetrator 3 from being transmitted to the leader 4 via the wire rope. It has the function of blocking.

6 is a supply pipe for sand, etc. that communicates with the inside of the upper end of the casing l, and is used to supply sand, gravel, crushed stone, etc. on a separately provided air supply means.
One or a mixture of sand-like granular materials such as slag, lime or cement is fed into the casing l, air particles are separated in that space, and sand, etc. is deposited and replenished near the lower end opening of the casing l. Therefore, by making the open end of the replenishment vibro deeply penetrate into the casing 1, by making it flow into the pipe in a spiral shape, by providing a filter, etc., it is possible to promote the air particle separation effect and to ensure its effect. I take it as a thing. On the other hand, the compressed air from which sand and the like have been separated is recovered outside the pipe through a discharge (recovery) pipe 7 that also communicates with the upper end of the casing l. A pressure regulating valve is inserted in the middle of the exhaust pipe 7 so that the exhaust pressure can be controlled.

Maintenance of these vibros 7 can be facilitated by placing them along the power transmission rod 2 up to the upper end of the casing l or installing them inside the vibro, and by using steel pipes. From then on, the supply route uses combustible pipes.

8 indicates a work boat, 9 indicates the water bottom ground surface, and W and L indicate the water surface.

FIG. 2 shows the steps of the method of the present invention, its fa)
(b) shows the state at the completion of the sandpile creation process, when the penetration device was penetrated to a predetermined depth into the soft ground at the bottom of the water. In Fig. 2(a), when a steel pipe is used for the power transmission rod 2, the lower end is opened to prevent buoyancy, or air is actively introduced during extraction to prevent penetration. It is also possible to return the soil to the eroded original ground. In addition, in the figure, two casings are symmetrically connected to the transmission rod 2, but the number of casings 1 may be one,
It cannot be taken as a number. However, it goes without saying that the supporting position of the casing must be balanced with respect to the penetrating machine 3 when viewed from above.

Figure 2(b) shows that by adjusting the pressure regulating valve inserted in the discharge pipe, the air pressure at the lower end opening of the casing 1 is gradually controlled to exceed the active earth pressure at the depth of the lower end of the pipe and to be less than the passive earth pressure. This figure shows the construction of a sandpile for the hollow tube diameter needle by pulling up the casing.Of course, during this operation, it is necessary to keep pneumatically feeding and replenishing the casing with sand, etc. At that time, by controlling the air pressure to a level greater than the passive earth pressure, it is possible to create a sandpile with a diameter larger than the pipe diameter, so it is possible to make the diameter of the casing 1 relatively thin. In other words, the mass of the casing can be made smaller. Therefore, using a casing with a specific diameter, it is possible to create sandpiles each having a plurality of diameters.

Furthermore, since the created sand pile is made of dry sand, it has an excellent initial water absorption capacity, and the pore ratio of the sand can be reduced through compaction during construction, creating a compacted sand pile. be able to. During the above-mentioned construction, the used compressed air is collected by the discharge pipe 7, so there is no risk of polluting the water area.

Example 2 In FIG. 1(a), water is supplied into the casing 1 in a fluid state using a replenishing vibro such as sand.

In this way, the casing is filled with water, and by gradually pulling out the casing, the filled water is discharged from the casing 1, forming a sandpile in the ground. On the other hand, compressed air is supplied into the casing 1 from the fluid discharge pipe 7, and the pressure is applied to the amount of added water that is filled, and the amount of added water that is discharged into the ground when the casing 1 is pulled out. Furthermore, since the compressed air only acts on the upper surface of the hydrated sand in the casing and does not leak to the outside, there is no risk of polluting the water area.

In particular, when the amount of water added is such that the water content ratio is near saturation, the fluid state can be maintained by applying an external force such as vibration, so a vibrator is activated in addition to the casing lifting operation. By doing so, the amount of added water can be discharged into the ground as a fluid, and by controlling the pressure of the compressed air mentioned above, it is possible to create a sandpile having a diameter larger than the pipe diameter.

(C) Effects of the Invention As described above, according to the method of the present invention, the axial length and diameter of the casing are smaller than the length and diameter of the created sandpile, so the weight of the penetration device that is a component of the casing is smaller. (1) The power of the penetrating machine that drives the penetrating device can be small.

(2) The power of the winch for lifting and hanging the penetration device can be saved.

(3) The structure of the leader that lifts and guides the penetration device can be weakened and lightened.

(4) Therefore, the stability of the construction machine is improved and it is possible to downsize the construction machine.

Since the casing is used as a sand discharge pipe and its axial length is shorter than the construction improvement length, all or most of the sand, etc., is transported and supplied to the lower position. This is advantageous in reducing the power required to transport sand, etc.

Furthermore, if the method of the present invention is used to make the penetrating machine underwater, or if the penetrating machine is detachable from the side of the power transmission rod instead of the top end, the upper part of the leader becomes unnecessary, which contributes to the stability of the construction machine. .

[Brief explanation of drawings]

Figure 1(a) (ri) is a schematic side view of a construction machine that carries out the method of the present invention, Figure 1+bj is a front view of a penetration device of another type of construction machine, and Figure 2 shows the steps of the method of the present invention. It shows
The (ai figure) is a partially cutaway front view of the penetrating device when the casing penetration is completed, and the fb1 figure is a partially cutaway front view including the penetrating device after sandpile creation is completed.1. Casing, 2... Power transmission rod, 3... Penetrator, 4... Guide leader, 5... Buffer, 6...
・Supply pipe, 7... Discharge pipe, 8... Work boat,
WXL...Water surface.

Claims (5)

[Claims] (1) In a method of driving sand piles at a predetermined depth in soft ground, the ground penetration casing has a closed top end and an axial length shorter than the length corresponding to the soil improvement depth. At the same time, a power transmission rod connects the penetrating means provided at the upper part of the casing with a pipe for replenishing the transport fluid and sand mixed in the casing, and separating the sand, etc. within the casing. A pipe for discharging the fluid or a fluid supply pipe for adjusting the internal pressure of the casing is connected, and when the casing that has penetrated to a predetermined depth is pulled out, a void created in the ground below is filled with the inside of the casing. A method of constructing sand piles, etc. with a casing shorter than the improved length, characterized by discharging and filling the supplied sand, etc. (2) The length of the power transmission rod is at least longer than the soil improvement depth or the soil improvement depth plus water depth minus the axial length of the casing. A method of constructing sand piles, etc. using a casing shorter than the improved length as described in Scope (1). (3) Sand, etc. is one of sand-like granular materials such as sand, gravel, crushed stone, slag, lime, cement, etc., or a mixture thereof;
A method for constructing sand piles or the like with a casing shorter than the improved length, as set forth in claims (1) and (2), which comprises using compressed air as the transport fluid. (4) The sand, etc. is one of sand-like granular materials such as sand, gravel, crushed stone, ore slag, or a mixture thereof, and the transport fluid is a small amount of water. (2
) method of constructing sand piles, etc. using a casing shorter than the improved length. (5) A pressure regulating means is inserted in the middle of the transportation fluid discharge pipe or the fluid supply pipe, and the pressure inside the casing is adjusted by controlling the means, and the casing is formed by sand etc. discharged into the ground soil. Claims (1) to (4) consist of controlling the diameter or density of the pile.
A method of constructing sand piles, etc. using a casing shorter than the improved length described in Section 1.