JPH01154912A - Method and apparatus for improving peaty ground - Google Patents

Abstract

PURPOSE:To raise the strength of improved ground by lengthening nozzle and also by increasing the amount of grout to be jetted by a method in which a grout or hardener flow path is slantly provided in a rod crown having a sidewardly directed nozzle. CONSTITUTION:An excavating blade 5 and a rod crown 7 having a side jet nozzle 6 are attached to the tip of an injection tube 1 supported by a rotary vertically movable mechanism. The upper part of the crown 7 has a flow path joint 71 to be screwed with the tube 1 and also has a slant flow path directed downwards from the joint 71. The lower end 73 of the flow path 72 is set back toward the direction of jetting, where the center axis 14 is set backwards from the center axis 75 of the crown 7 to secure the nozzle space 76 by as much long as the setting. The nozzle diameter can thus be increased, the side nozzle can also be shaped into a tapered structure, and the amount of jetting can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a ground improvement method and device for peat ground such as the Hokkaido Pea I layer, which has a water content of 300% to 10009A. be.

(b) Conventional technology Conventionally, to improve peat ground with extremely high moisture content, powder such as cement or lime is directly poured into the ground and mechanically stirred with the mud using a stirring blade, causing it to react and harden. In addition to this method, a method of injecting a hardening material through an injection tube has been used.

(c) Problems to be Solved by the Invention The method of stirring by adding powder as described above requires a very large machine and requires extensive installation and operation.

In addition, unlike slurry injection using an injection pipe, there is a limit to the depth of improvement, and the improvement is limited to shallow areas compared to injection pipe improvement, leaving fundamental problems unavoidable.

On the other hand, attempts have been made to improve the process by inserting an injection tube, but since there is no powerful stirring means, the conventional method of jet agitation has to be used. Since this is a prerequisite, there is a limit to the diameter of the injection pipe, and this also places restrictions on the diameter and length of the injection nozzle that must be installed there. Therefore, there are limits to the injection pressure of the hardening material that is injected into the ground and the amount that can be injected at one time. For this reason, it was not possible to increase the amount of hardening material injected per cubic meter of ground, and the strength of the improved ground had to be extremely low.

(d) Means for Solving the Problems In order to solve the above-mentioned problems, the present invention aims to make the flow path inherited from the injection pipe flow path to the rod crown flow diagonally downward to form the inflow section of the side injection nozzle. By setting back the rod, it was possible to take up a longer nozzle space than the normal wall thickness of the rod.

Additionally, the longer nozzle space allows the nozzle diameter to be increased, making it possible to form the side nozzles into a tapered structure.

Furthermore, the tapered structure of the side nozzle prevents a drop in the injection pressure of the hardening material jet, and also increases the amount of hardening material injected per cubic meter of ground, making it possible to increase the strength of the improved soil.

(e) Implementation example Hereinafter, the present invention will be described in detail with reference to the drawings.

Reference numeral 1 is an injection pipe that is supported by a rotating vertical movement mechanism 2, and the upper part is connected to a supply hose 4 that communicates with a hardening material supply section via a swivel 3, and a cutting blade 5 is provided at the tip, and a side injection nozzle is provided on the side wall. A rod crown 7 having a diameter of 6 is attached. The upper part of the rod crown 7 is a flow path joint part 7 into which the injection pipe 1 is screwed.
A diagonal descending flow path 72 is provided that flows diagonally downward from there, and its lower end 73 is set back with respect to the injection direction so that its central axis 74 is rearward of the central axis 75 of the rod crown. , and the nozzle space 76 is secured accordingly. Reference numeral 8 denotes a nozzle tip, and the rear part of the flange 81 is a base 82 that is screwed into the threaded part 77, and the entire nozzle outer cylinder 84 has a retaining part 83 that engages with a box tool when screwed into the threaded part 77 as the base. A fitting hole 85 into which the nozzle liner 9 is fitted is bored.

The nozzle liner 9 has a flange 91 at its rear end, has a tapered nozzle hole 92 with a diameter smaller at the outlet than at the nozzle inlet, and is made of a hard wear-resistant material such as ceramic. The side nozzle 6 is configured by fitting such a nozzle liner 9 into the fitting hole 85 of the nozzle chip 8 and screwing it into the threaded part 77 provided at the lower end of the inclined downward flow path 72. This is much larger than the nozzle diameter of 1.8 to 2.5 mm provided in this type of injection pipe, and it is possible and appropriate to provide the diameter of the narrowed injection outlet to about 3.2 mm.

FIG. 6 shows the configuration of the side nozzle 6 according to another embodiment, in which the tapered nozzle is set not in the horizontal direction but at an angle downward from the lower end 7°3 of the diagonal descending channel. By doing so, the nozzle space can be secured even longer.

First, the injection pipe configured as described above is rotated and lowered to the target ground A.

The peat ground itself is extremely soft with a water content of 300% to 1000%, but there are many delicate substances such as tree roots, and it is difficult to insert it as is. Lower the injection tube while cutting the fibrous material. Of course, in such a place where there is no fibrous material, it may be inserted as it is without rotating it and using its own weight.

When a predetermined depth has been reached, the ground hardening material is fed under high pressure into the injection pipe 1 through the hardening material supply port 4, and the injection pipe is rotated upward while being injected at high pressure from the side nozzle 6, so that the hardening material jet forms peat soil. The hardening material is stirred and mixed to create a cylindrical hardened layer B, but the injection tubes developed so far can only be configured as straight nozzles with a nozzle diameter of 1.8 to 2.5 mm. According to this, since the amount of hardening material ejected was about 30 liters per minute, the hardening material flowed into the moist soil before hardening, making it impossible to maintain the hardening density.

As a result of experiments, the method according to the present invention has obtained the following results.

Nozzle diameter of side nozzle 6: 3.2 mm, injection pressure: 200
kgf/cJ, injection tube rotation speed 20 times per minute, rising speed 3 meters per minute, rising pitch 2.5 cm, rising 1
The number of rotations of the injection tube per step was set at 1.5 times, and Nippon Steel Earth-Tato 201 (trade name) was used as the hardening material.
Addition amount 300kg/W/C1,,0) 400kg
The slurry was prepared using a ratio of 600 kg of water to 600 kg of water. The temperature was 19°C1 and the weather was cloudy.

As a result, the diameter of the cylindrical hardened layer created was 800 mm, and the unconfined compressive strength of the hardened layer was 4.5 mm. The improvement effect was sufficient at kg/cf.

Naturally, the construction conditions will vary depending on the water content ratio of the target ground, etc., but the nozzle diameter of the side injection nozzle is 2.
5 to 3.5 mm Hardening material discharge amount is 60 to 90 p/
min, injection pressure 100-300 kg/cM, hardening agent addition amount 200-500 kg/rr? It was confirmed through both field and laboratory experiments that the level was appropriate.

(f) Functions and Effects of the Invention Since the present invention is configured as described above, the hole diameter of the side injection nozzle can be configured to be large, and in combination with the adoption of the tapered nozzle, stirring and hardening of the hardening material jet can be achieved. This dramatically increases the amount of material discharged.

As a result, we have succeeded in full-scale application of high-pressure injection injection to peat ground, which previously could only be used supplementally due to the low strength of the hardened layer.

Note that the present invention is fully applicable to general ground depending on the conditions.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is an overall explanatory diagram showing the construction situation, Fig. 2 is a side view of the rod crown, Fig. 3 is a front view thereof, and Fig. 4 is a side view of the nozzle tip. 5th between cross sections
The figure is a front view of the same, and FIG. 6 is a side view of a rod crown according to another embodiment. 1 - Injection pipe 2 - Rotating vertical movement mechanism 3 - Swivel 4 - Supply hose 5 - Cutting blade 6 - Side injection nozzle 7 - Rod crown 71 - Channel succession part 72
- Diagonal descending channel 73 - Lower end of the diagonal descending channel 74 - Diagonal descending channel central axis 75 - Crown rod central axis 76 - Nozzle space 77 - Threaded portion 8 - Nozzle tip 81 - Flange 82 - Base 83 - Connection Base part 84 ~ liner fitting hole 9 ~
Nozzle liner 91 ~ liner flange 92 ~ nozzle hole A ~ target ground B ~ cylindrical hardened layer

Claims (3)

[Claims] (1) A tapered nozzle whose tip part is closed and the flow path is set back from the lower end of the flow path that flows diagonally downward from the flow path joint part of the injection tube at the rear end and is laterally longer than the rod radius as a whole is provided. An injection pipe with a rod crown attached to the tip is lowered into the target ground and inserted to a predetermined depth, and the soil hardening material is pumped into the injection pipe at high pressure and injected as a high-pressure jet from the tapered nozzle. A method for improving peat ground characterized by creating a cylindrical hardened layer in the ground by rotating and lifting a pipe. (2) A rod crown with a cutting blade at the tip and a tapered nozzle that is longer than the rod radius in the horizontal direction from the lower end of the flow path that flows diagonally downward from the flow path joint of the injection tube and is set back. A peat ground improvement device characterized in that an injection pipe attached to the tip is supported by a rotating vertical movement mechanism, and the upper end of the injection pipe is connected to a hardening material supply section via a swivel. (3) Peat ground improvement device according to claim (2), wherein the taper nozzle is provided laterally from the lower end of the flow path of the rod crown and is set at an angle diagonally downward or upward.