JPH0317963B2 - - Google Patents

Description

[Detailed description of the invention]

This invention uses a water-absorbing swelling material such as quicklime,
This relates to a construction method for improving soft ground by placing permeable materials such as sand and crushed stone into the soft ground in the form of piles. Conventionally, water-absorbing and expanding materials such as quicklime, sand,
A method of ground improvement is carried out by placing permeable materials such as crushed stone in the form of piles in soft ground, and a vibrating drive device is used to create piles with a larger diameter than the outer pipe. The compaction method has been adopted, but it generates vibration and noise, causing pollution problems, and the scope of application of this method is limited. In most cases, when the soil quality of the target ground is not uniform, a method is used to deal with the problem by changing the improvement material depending on the soil quality. This significantly reduces construction efficiency, so soil quality is often concentrated at one point and only one type of improvement material is applied.
Furthermore, in most cases in conventional construction methods, compressed air is used as a material discharge means, which causes the compressed air to blow out onto the ground and increase lateral displacement of the ground. Therefore, in order to eliminate the drawbacks of conventional construction methods, the present invention aims to provide a construction method for improving soft ground that enables efficient and pollution-free construction. As a means of discharging the material, a material feed device is attached to the tip of the inner tube, and the outer tube is used as a guide pipe to create a double-pipe casting device.The inner and outer tubes are each driven to rotate, and the material is forcibly fed by the feed device. The material is discharged without using any compressed air for discharging the material, and multiple hoppers are provided to store and feed the material into the casing, and different types of materials are charged into each hopper. By detecting changes in soil quality and their depth from self-recorded records of the pouring depth at the time of casing penetration and the current of the drive motor, determining the type and amount of material to be introduced, and depositing the pile, the soil quality can be determined. This method is characterized by creating piles that can respond to changes in conditions. Other objects, features, and advantages of the present invention will become apparent from the following detailed description of one embodiment of the soft ground improvement method of the present invention, taken in conjunction with the accompanying drawings. FIG. 1 shows an embodiment of a pouring device for carrying out the method of improving soft ground according to the present invention. The pouring device 1 includes an inner pipe 2 having a feed device 3 for ground improvement material at its tip, an outer pipe 4 serving as a guide pipe for discharging the material, and a plurality of hoppers for storing different types of materials. 5, 6, and a drive device 7 consisting of drive motors 8, 9 for rotationally driving the inner tube 2 and outer tube 4, respectively. 2 consisting of such an inner tube 2 and an outer tube 4
The heavy pipe type driving device 1 is attached to a leader (not shown) of a general-purpose pile driver so that it can be raised and lowered, and is raised and lowered by winding and feeding out a wire 10 from a winch. At the upper end of the outer tube 4, a drive device 7 consisting of suitable drive motors 8, 9, such as electric or pneumatic type, is provided, and drives the inner tube 2 and the outer tube 4, respectively, through two types of output shafts for the inner and outer tubes. It is ready to drive. Further, a rotary hopper 11 is provided below the drive device 7 at the upper end of the outer tube 4, and a plurality of hoppers 5 and 6 for storing different types of materials are connected to the rotary hopper 11 through feeders 12, respectively. . Further, an on-off valve 14 is provided at the lower end of the outer tube 4, and a spiral 1
5 is installed. The upper end of the inner tube 2 is connected to one drive motor 8 of the drive device 7, and the lower end of the inner tube 2 is appropriately provided with a feed device 3. In addition, a depth detector 17 having a wire 18 and a pulley 19 to detect the pouring depth and changes in soil quality in the target ground, and a current converter 21 to detect changes in current in the drive device 2 are combined with a self-recording recorder 22. used. When implementing the soft ground improvement method of the present invention using the driving device configured as described above, first, to perform normal pile driving, the driving device 2 is started in normal rotation and the driving device 2 is started in normal rotation to penetrate to a predetermined depth. . The penetration depth at this time is detected by the depth detector 17 via the wire 18. Next, the required materials for ground improvement are put into each hopper 5, 6, and the feeder 12 is operated to put a predetermined amount of material into the outer tube 4. When the introduction of the improved material is completed, the drive device 2 is started in reverse, and the material is discharged into the soil by the feed device 3, while the pouring device 1 is pulled up to complete the pouring. Next, when driving a pile with a diameter larger than the outer diameter of the outer pipe 4, the driving procedure is the same as the normal pile driving described above, but the pulling speed is lower than that for normal pile driving. Just do it. Now, the required pulling speed for normal pile driving is calculated.
V ₀ m/min, the pile diameter is d ^m , the pulling speed when the diameter is larger than the outer diameter of the outer tube is V ₁ m/min, and the pile diameter is D ^m , then V ₀ , V ₁ , d, The relationship between D is shown in the table below, and the pile diameter D can be arbitrarily determined by selecting _V1 .

[Table] To give an actual example, the outer diameter of the outer pipe is 0.4 m, and the pulling speed is 1/2 of the normal pile driving speed, resulting in a pile with a diameter of 0.55 to 0.6 m. I was able to do that. In addition, when piles are placed so that the strength of the piles is uniform by changing the improving material in response to changes in soil quality, the following procedure is used. For example, in the case of the target ground as shown in Figure 3, cement-based ground improvement materials are generally used for sandy ground, quicklime-based ground improvement materials are used for silty ground, and especially for sandy ground. Adding quicklime-based improvers has almost no effect. In addition, in the case of a peat layer, it is necessary to add a large amount of improving material compared to the soil quality. From the above, in the case of actual improvement of soft ground,
For example, a cement-based material is put into the hopper 5 of the pouring device 1, a quicklime-based material is put into another hopper 6, and
Improve the soil using seed improvement materials. The pouring procedure is the same as the normal pile pouring described above, but when penetrating the casing, the pouring depth and drive motor current changes are recorded, and embankment 2 is placed according to the results.
5. The thickness of the peat layer 26, sand layer 27, and silt layer 28 is detected for each layer, and the type and amount of improvement material to be introduced is determined. An example of this self-recorded record is shown in FIG. Normally, the penetration resistance of the casing into sand layers, relatively hard clay layers, etc. is large, and therefore the second
In the figure, it can be determined that there is a layer that is difficult to penetrate between point b and point c. Now, when comparing the diagram in Figure 2 with the example of the target ground in Figure 3, the peat layer 26 (including the embankment 25) is 4 m (point a to point b),
It can be seen that the sand layer 27 is 2 m (points b to c), and the remaining 4 m is a silt layer 28 (points c to d). Therefore, first, for the silt layer, apply quicklime-based improvement material in an amount equivalent to 4 m from one hopper of the casting device.
If an amount of cement-based improvement material equivalent to 2 m is applied to the sand layer, and a large amount of improvement material is added to the peat layer according to the procedure for placing expanded diameter piles as described above, It becomes possible to create piles 30 that correspond to changes in soil quality. As described above, according to the improved construction method for soft ground of the present invention, a plurality of concrete can be placed by a pouring device equipped with a casing having a double pipe structure consisting of an inner pipe having a feed device and an outer pipe having a spiral. A different type of material is placed in the hopper in advance, and changes in the current of the drive motor for driving the casing are detected and detected with respect to the depth of pouring when the casing is penetrated, and changes in soil quality are determined. By controlling this according to the soil quality, it is possible to create piles of different diameters and improve the ground. In addition, in the soft ground improvement method of the present invention, materials such as quicklime, sand, and crushed stone are forcibly discharged by a feed device at the tip of the inner pipe without using compressed air. As a result, the shape of the pile is good, the tip of the pile and the top of the pile can be created with high precision, the continuity of the pile is good, the diameter is larger than the outside diameter of the casing, and the pile is compatible with changes in soil quality. This allows for effects such as reducing lateral displacement of the ground due to compressed air during pouring.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view showing the pouring device used to implement the improved method for soft ground according to the present invention, and Figure 2 is a self-recorded record of the pouring depth and drive motor current changes in the pouring device shown in Figure 1. The recorded diagram, Figure 3, is a schematic diagram showing the ground to be improved and the piles that have been placed. In the figure, 1... pouring device, 2... inner pipe, 4...
Outer tube, 5, 6...Hopper, 7...Drive device, 8,
9... Drive motor, 11... Rotating hopper, 17...
...Depth detector, 21...Current converter, 22...Self-recorder.

Claims (1)

[Claims] 1 In a construction method that improves soft ground by placing a water-absorbing and expanding material such as quicklime and a water-permeable material such as sand or crushed stone in piles in soft ground, a material feed device is installed at the tip. Different types of materials are placed in advance into multiple hoppers using a double-pipe casting device equipped with an inner pipe that serves as a guide pipe for discharging materials, and an outer pipe that serves as a guide pipe for material discharge. A soft ground characterized in that changes and their depths can be detected by self-recording of the driving motor current and the driving depth at the time of casing penetration, thereby making it possible to create piles of different diameters in response to changes in soil quality. improved construction method.