JPS6050927B2 - Ground injection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chemical injection method carried out for the purpose of ground improvement, and particularly to an injection method using a combination of instant setting grout and slow setting grout.

In recent years, the chemical injection method has been used in various types of construction work for the purpose of strengthening soft ground and stopping water.

However, grouts with a gel time of just a few minutes, which have been commonly used in the past, tend to overflow onto the ground or run out from slack in the ground on complex multi-layered ground or ground with abundant water, resulting in insufficient continuous solidification for the important target ground. It has become clear that it does not form a body and is difficult to achieve its intended purpose. To deal with this phenomenon,
A method was considered in which a sufficient amount of sleeve grout was applied around the injection pipe in advance, and then grout with a long gel time was used to penetrate into the fine gaps. However, with this method, in order to fill sleeve grout, it is necessary to excavate the ground with a large-diameter casing beforehand, and also to fill slack parts in the ground or layer boundaries with cement milk or LW grout. There is a problem that pretreatment to enhance the injection effect is time-consuming and uneconomical, such as the need to homogenize the ground by injecting high-strength grout. In addition, it requires considerable skill and technique to homogenize the ground with advance grouting, but this is one of the reasons why the effectiveness is not certain in the complex and diverse actual site. . Therefore, by using instant-setting grout, first of all, it is the simplest and most effective method to prevent grout from overflowing around the injection pipe or from flowing underground, which enables reliable injection into the specified area. It is.

This method uses instant setting grout with a gel time of several seconds, but if it can be fed into the ground reliably and continuously, there is little room for human factors such as advanced knowledge and judgment regarding the ground conditions to enter. Therefore, it is considered that there is very little variation in the injection effect in the actual field. However, the penetration mode of the injection method using instant setting grout is based on five types: slight penetration, consolidation, and vein-like penetration, so increasing the injection rate per unit time increases the resistance of the ground. There are problems in that the injection pressure tends to be high and that the skeletal structure of the soil is more likely to be destroyed microscopically than in methods using slow-setting grout. Strict construction management is required to minimize ground deformation.

Therefore, by combining slow-setting grout and fast-setting grout, composite injection that takes advantage of the advantages of each was considered, and a method was proposed in which these two types of grout were alternately injected using a double pipe. .

However, with this method, there is a possibility that the grout packer formed by the instant-setting grout may be pierced by the subsequently injected slow-setting grout, or the packer effect around the injection pipe may become insufficient as the grout is poured. There is a concern that the advantages of composite injection may not be fully utilized. Furthermore, one of the most important factors for effective ground improvement through injection is to reduce the injection rate per unit time.

This is considered an essential condition in order to form a homogeneous solid body without causing shear failure in the ground and without changing the structure of the ground as much as possible. However, regardless of whether it is a single pipe or a double pipe, the grout discharge port is usually considered to be one, so there is a contradiction that increasing the injection speed to improve economic efficiency reduces the injection effect. , came as a major issue. However, although some models have been equipped with strainer-style discharge ports, changes in the ground properties associated with injection create a difference in the resistance pressure of the surrounding ground before the injection has even begun, resulting in an increase in resistance. Earth! The strainer-type injection method has been considered not to be as effective as theoretically because the strainer holes near the mountain become clogged one by one, and eventually only one port will be able to discharge.

As a result of careful consideration of the above-mentioned problems, we have found that the most effective way to solve the above-mentioned problems all at once is to simultaneously inject instant-setting grout and slow-setting grout using a three-way pipe. We focused on this fact and came up with this construction method.

By the way, the injection device for carrying out the construction method of this invention has the following functions.

In other words, the three channels are completely independent all the way to the discharge port, the drilling water is discharged from the tip when drilling, and the switch to grout injection can be easily and reliably made after reaching the deepest point, and the main ingredient of instant setting grout is A. liquid and its curing agent liquid. ．． Make sure that the B liquid is thoroughly mixed and that the A. ．． It is required that the slime does not flow backward from the outlet for liquid B and the outlet for liquid C+D, which becomes a slow-setting grout liquid, that the rod can be easily attached and detached, and that all three channels can withstand high pipe internal pressure. Conventionally, there is a concentric triple tube for discharging chemical liquid, water, and air, but this type of tube with a diameter of ψ40 to 5-5, which is used for normal chemical injection, is important in terms of the thickness and strength of the tube. It is difficult to implement and has little practicality. Therefore, the injection device used in this construction method has A. Insert two parallel tubes for liquid B, the outer tube and A, . The interval between the tubes for liquid B was used as the flow path for liquids C+D. The present invention will be explained below with reference to Examples. FIG. 1 shows the construction state of this invention and the equipment used therein.

Then, insert the injection pipe 1 into the ground, and while pulling it up, pour loosely setting grout C+D from the discharge port 2 at its tip.
Discharge and inject the liquid into the ground. 0.3TrL from the tip.
A. of instant setting grout at a distance of ~2 m. ．． B liquid discharge port 3
Instantly setting grout is discharged and injected from the discharge port 3 at the same time as slow setting grout is injected. Injection tube 1 is shown in Figures 2 and 3.
As shown in the figure, two tubes, a tube 5 for liquid A and a tube 6 for liquid B, are placed inside the outer tube 4.
A parallel tube is inserted, and the gap 7 between the outer tube 4 and the tubes 5 and 6 becomes a flow path for the C+D liquid, through which each grout liquid is fed.

Note that the type of liquid that passes through the three channels thus formed is not limited to this embodiment, and can be changed as appropriate. The injection pipe 1 is then connected by a joint structure using a joint 8 shown in FIGS. 4 to 9. A spline key 9 is formed at the fitting portion of each tube to transmit rotational torque, and a pin 11 is inserted into a pin hole 10 to connect the tubes. The main body of the joint 8 is provided with two channels 7'' for the C+D liquid.The discharge port 2 is provided with a ball valve 12 as shown in FIGS. 10 to 12.

As shown in FIGS. 13 to 15, the discharge port 3 has valves 13 and 14 operated by hydraulic pressure, and liquids A and B are mixed at the discharge port 3. Note that the flow path of the C+D liquid in the nozzle part constituting the discharge port 3 is indicated by the reference numeral 7''.By the way, if the distance between the discharge ports 2 and 3 is too close, the pore water pressure around the pourer tends to increase, leading to ground upheaval. In addition, if the distance is too far, it is difficult to detect changes in the soil layer in detail, so it is appropriate to position the discharge ports 2 and 3 preferably at a distance of about 0.5 to 1.07 nm. Pump A of the injection machine is a device that can convert the discharge amount for liquid B and liquid C+D, and the injection speed is controlled separately.
The ratio of the injection amount of seed grout can be freely changed and adjusted while injection is continued.

By this, for example, in the case of uniform sandy ground where the soil layer is relatively permeable, a small amount of instant setting grout can be injected from the upper discharge port 3, and then the slow setting grout can be simultaneously applied to both discharge ports 2 and 3. The injection speed can be approximately twice that of injection from the saw discharge port. By the way, the following materials are used for the base liquid A, its curing agent B, and the slow-setting grout C+D liquid, which are blended to provide the above-mentioned instant setting properties.

For instant setting grout, water glass is used as the A component, and alkali salts such as sodium aluminate and bicarbonate are used as the B component hardening agent.
Inorganic acids such as phosphoric acid and carbonic acid and their salts, as well as swindle acids, tartaric acid, etc., as well as organic acids and their esters and polyhydric alcohol partial esters, as well as the above-mentioned inorganic acids and their salts. A suitable combination of the following ingredients is used so that the gel time is several seconds or less.

As a slow-setting grout, the above-mentioned organic acid esters and polyhydric alcohol partial esters may be used alone or in combination of two or more, or in addition to these, an inorganic curing agent may be appropriately added as a gel time adjusting agent depending on the purpose. The gel time is from several minutes to several tens of minutes.

Further, the standard formulation of 100e in one specific example is as follows.

(1) Instant setting grout Gel time (15 parts C), 3 seconds A liquid...Water glass 50k9, water 50kg B liquid...
...Potassium bicarbonate 15 kg, remaining water (Ii), slow-setting grout, gel time (15 remaining C), 1 part C solution...
...Water glass 60k9, water 40k9D liquid...
・6 kg of ethylene carbonate, remaining water This invention has the above-mentioned configuration, and the main liquid of instant setting grout, its hardening agent liquid, and slow setting grout liquid are passed through three different flow paths, and are separated by a predetermined interval above and below. Since the grout is injected simultaneously from a single injection pipe with a slanted discharge port, and the instant-setting grout is constantly discharged from the top, a grout packer is reliably formed until the end.

Therefore, highly reliable limited area injection is possible. In addition, the instant-setting grout that was injected in advance roughly fills loose parts and large gaps, and the loose-setting grout with good permeability is injected through the injection space created by pulling up the injection pipe. As a result, the injection can be carried out without strain, and homogeneous ground improvement can be expected. Furthermore, since the instant-setting grout and the slow-setting grout, which use one injection pipe, are separately delivered through three flow paths and discharged, the injection speed and amount of both grouts are adjusted according to the soil quality. Adjustment and combinations are possible.

In other words, in this invention, two types of grout can be sent to separate pumps, and therefore, regardless of changes in ground resistance, the grout can be discharged from separate ports to the end, so it can be used as a strainer type grout. There is no need to worry about clogging of the discharge port due to injection.

Further, the two discharge ports are arranged at a predetermined interval above and below, that is, from 0.5 to
Since the distance is maintained at a distance of about 1.0 TL, the influence on the surrounding ground regarding pore water pressure etc. is significantly smaller than when the two types of grout are injected from a single outlet. Therefore, in this invention, it is possible to increase the total discharge speed while decreasing the discharge speed per unit time of grout from one discharge port, which allows careful injection and is economical. Excellent.

In other words, it is calculated that one hole can be drilled at the same injection speed as two holes. Note: As in the illustrated device, one injection tube has two parallel tubes inserted into the outer tube.
If three channels are formed by the main parallel tube and the gap between the outer tube and the parallel tube, an injection tube with the same diameter as a normal injection tube can be obtained. Therefore, the advantages of the construction method using instant setting grout and the construction method using slow setting grout can be effectively and economically utilized.

[Brief explanation of drawings]

Figure 1 is a sectional view of the construction state, Figures 2 and 3 are a cross-sectional view and a partial longitudinal sectional view of the inlet pipe (note), Figure 4 is an exploded perspective view of the joint, and Figure 5 is the injection pipe joint. 6 is a sectional view along I-1, FIG. 7 is a side view of the joint, FIG. 8 is a cross-sectional view thereof, FIG. 9 is a cross-sectional view of the connected state, and FIGS. 10 and 11. , 1st
Figure 2 is a plan view and longitudinal sectional view of the distal end outlet portion, Figure 13,
FIGS. 14 and 15 are a sectional view and a vertical sectional view taken along the line 1--2 of the upper discharge port portion. 1...Injection pipe, 2...Discharge port, 3...
...Discharge port, 4...Outer tube, 5,6...
・Pipe, 7...Gap, 7'', r...Flow path,
8...Joint, 9...Spline key 1
0...Pin hole, 11...Pin, 12.
...Ball valve, 13,14...Valve.

Claims (1)

[Claims] 1. Insert an injection pipe into the ground that has three channels in one pipe and discharge ports with the required vertical spacing, and then, while pulling up the injection pipe, insert two of the three channels in the injection pipe. A main agent liquid and a curing agent liquid are fed through a flow path to provide instant setting properties, and these two liquids are merged near the above-mentioned discharge port to discharge and inject instant setting grout. A ground injection method characterized in that slow-setting grout is fed simultaneously with the instant-setting grout using one channel, and is discharged and injected from a lower discharge port.