JPS59173414A - Improvement work of soft ground - Google Patents

Abstract

PURPOSE:To sufficiently make use of the performance of an improving agent by allowing the increase of contact area with soil by a method in which a water absorptive expandible material, e.g., quick lime, etc., is driven into the ground in a cylindrical form. CONSTITUTION:An inner driving tube 5 is provided to an outer driving tube 8, and the inner and outer driving tubes 5 and 8 are penetrated into soft ground to a given depth. While supplying a water absorptive expandible material into the ground through the space between the outer and inner driving tubes 8 and 5, the driving tubes 5 and 8 are pulled up to form a pile of a doughnut-shaped cross section. The results of a driving test in which the test was made in a clayey silt-based soft ground and the quality of the soil one month after the driving was measured showed that the average strength of the intermediate ground was higher in this method than in the conventional panel work for the same 10% areal ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for improving soft ground by supplying a water-absorbing and swelling material such as quicklime into the ground.

BACKGROUND ART Conventionally, a pile construction method has been used to improve the ground by placing a water-swelling improving material such as quicklime in the form of a pile in soft ground. The main characteristics of this improvement material are a hardening reaction that occurs when it comes into contact with the soil, and a dehydration reaction that absorbs moisture from the soil. For example, increasing the surface area per pile means increasing the pile diameter, and the soil The distance from the contact surface to the center of the pile becomes longer, the reaction time becomes longer, the performance of the improved material deteriorates further, and there is a big economic disadvantage, and the hardening reaction and dehydration reaction progress to the center of the pile. It takes a long time to do this, and the rapid reactivity properties of these improved materials cannot be fully utilized.

The present invention aims to solve the problems of conventional pile construction methods in which the properties of these improved materials are not fully utilized.

The present invention makes it possible to increase the contact area with the soil by casting a water-absorbing and swelling material such as quicklime in a cylindrical shape, and furthermore, it is possible to reduce the distance between the contact surface of the soil and the core of the soil. Therefore, the chemical and physical reactions are allowed to proceed at a faster rate), and the properties of the improved material (Ml) are fully utilized. Compared to cylindrical piles, the number of piles can be reduced, making it possible to increase economical effects.

The present invention will be explained below with reference to embodiments shown in the accompanying drawings.

, 74 shows a front view of an apparatus implementing the invention.

This device is attached to a general-purpose pile driver (none of which is shown), which is a base machine, so that it can be raised and lowered. The device is raised and lowered by winding and pulling out 10 wires using a winch (not shown) of the base machine.

2 is axis 11? i: A drive device that rotationally drives the inner casting pipe 5 through the drive pipe 5; 3 is a drive device that drives the outer casting V pipe 8 via the drive pipe 12 to which the hopper 4 is attached; The rotational speed of each can be adjusted separately, and the difference in the rotational speed between the outer casting pipe 8 and the inner casting pipe 5 can be adjusted as desired.

The outer casting pipe 8 and the inner casting pipe 5 are arranged concentrically, and a spiral 7 is attached to the outer periphery of the inner casting pipe 5 to transport the improved material downward.

A sword vine 7 is provided at the lower end of the inner casting pipe 5, and a sword vine 7 is provided at the upper end for discharging earth and sand filled in the middle gate side casting pipe 5, and for removing the negative impact generated inside the inner casting pipe 5 when pulled out. Exhaust and air inlet pipes IO are provided to avoid pressure. The air introduction pipe 10 is fixed to the outer casting pipe 8 and is rotatably held relative to the inner casting pipe 5.

An opening/closing hole 99 is provided at the lower end of the outer casting pipe 8. The opening/closing box 9 is closed by earth pressure resistance during penetration, and can be automatically opened by the supply pressure of the improving material supplied from between the outer casting pipe 8 and the inner casting pipe 5.

The construction method using the equipment shown in Figure 1 will be explained.

Start the drive device N2.3 at the same time. While rotating in the same direction and at the same rotation speed, wire 1 is fed out and penetration begins. When the predetermined depth is reached, the drive device N2.3 is stopped and the quicklime is removed. Improved materials such as the above are introduced between the outer casting pipe 8 and the inner casting pipe 5 via the U-turn hopper 4. After the injection is completed, start the drive device 2 and reverse the rotation), and the improved material is placed inside and outside the cast pipe 5.8.
Do not pull up until you are sure that the tip has been reached. This confirmation is determined based on the required time calculated from the discharge capacity of the spiral 6 attached to the inner casting pipe 5 and the sudden increase in the driving torque (ampere) of the inner casting pipe 5. After confirmation, the drive device 3 is started (reversely) and the device is pulled up by winding the wire 1, completing the casting. The pulling speed is determined by the required amount of improving material and the discharge capacity of the spiral 6.

In this way, a pile with a doughnut-shaped cross section is created in the soft ground.

Figure 2 shows an example of another uninvented device, which uses a single drive unit and discharges the improvement material into the soil using pressurized air, and is a simpler device than the one shown in Figure 1. It can be done.

In Figure 2, 13 is an inner casting pipe, 14 is an outer casting pipe, and the upper and lower parts of the inner casting pipe 13 and the outer scooping pipe 14 are integrally connected by support lips 15 and 16. , 7 is connected to a supply pipe 18 at a flange 17, the supply tube 18 is connected, and the supply tube 18 is connected to a drive device 19. The supply pipe 18 is provided with a hopper for receiving improved material, and an opening/closing damper 4 is provided in the supply pipe 18 below the hopper.

Reference numeral 22 denotes a pressurized air device, which pressure-feeds the improved material in the pronation of the receiving hopper between the inner pouring pipe 13 and the outer pouring pipe σ14, and presses the improved material into the soft ground from the opening/closing box at its lower end. The air forced into the ground passes through the inner pouring pipe 13 as appropriate to the pipe 2.
4.2FJ) can be discharged.

In addition, the station in the figure is the cutter installed at the lower end of the inner casting pipe 13, 2
Reference numeral 7 denotes an improved material passage hole provided in the 7 flange 17.

Next, in order to compare the improvement effects of the above-mentioned method of the present invention and the conventional pile method on soft ground, a pouring test was conducted in clayey silty soft ground, and soil properties were measured after a month of pouring. did.

The driving specifications are as shown in Figure 4 and Figure 5. In the method of the present invention shown in Figure 4, the outer diameter is 100-1, and the inner diameter is 800m.
Pile ′f of length 101: 60 pieces, force) The spacing t between the piles
Fig. 75 shows an example in which piles of 400 m in outer diameter and 10 m in length were cast in the order of 1680 mm or 2000 mm, and the distance t between them was 1120 mm. As shown in the table below, the average strength of the intermediate ground is higher with the construction method A40000 of the present invention than with the conventional pile construction method at the same 10% area ratio. Even with an area ratio of 7.1%, it showed almost the same strength, and it was confirmed that a more economical design was possible compared to the conventional 7-piles.

The ground improvement material used in the present invention can be the same as that used in conventional pile construction methods, with the main material being one or two layers of calcined lime dolomite, and optionally secondary materials such as blast furnace slag, converter sash, and plywood. ash, gypsum, cement,
It is made of one layer of clay or a mixture of two or more materials.

As explained above, in the ground improvement method in which the dehydration-swellability improving material is cast in the form of piles, the contact area between the improving material and the soft material is reduced by casting Pi A/ in a cylindrical shape. By making full use of the performance of the improvement material to increase the size, the improvement @ area will increase and the soft ground can be improved in a shorter period of time.

Furthermore, since the improved area is increased, the number of piles to be placed can be greatly reduced compared to conventional pile construction methods, resulting in a large economic effect.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a device for carrying out misfire #l. Figure 1 and Figure 2 are cross-sectional views of other devices carrying out the present invention.
2.3.19... Drive device 5.13-・Inner pouring pipe 8.14・-・Foreign pouring pipe 4.20j−・Hopper agent Masu Saito', Yugai 2 persons Figure 4 Exit 5

Claims (1)

[Claims] An inner pouring pipe is provided within the outer pouring pipe, and the inner and outer pouring g is penetrated into the soft ground, and after penetrating to a predetermined depth, an improved material with water absorption and expansion property is passed between the outer pouring pipe and the inner pouring pipe. A construction method for improving soft ground that is characterized by raising the excavated and cast pipe above the ground while supplying it into the ground.