JPH0516495B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a chemical liquid injection method, and more particularly, to a chemical liquid injection method in which an instant-setting chemical liquid is injected using a double pipe rod. BACKGROUND ART Conventionally, as a chemical injection method, a so-called double-pipe rod instant-setting injection method has been proposed and implemented, in which, for example, a double-pipe rod is used to inject an instant-setting chemical. The principle of the double pipe rod instant connection injection method is as follows. That is, when an instant-setting chemical solution with an extremely short gel time is injected into the ground, it initially penetrates radially from the tip of the double-tube rod, forms a sphere, and begins to gel. However, since the injection continues and the chemical liquid is discharged one after another, the inside of the initially formed gel sphere is destroyed before it gains sufficient strength, creating several channels. The chemical solution that emerges from the uninjected part of the ground through this channel penetrates radially from here, solidifies into a hemispherical shape, and solidified matter grows around the initially formed sphere. I'll go. A spherical solid body is obtained by repeating all the above steps. The penetration state of such an instant-setting chemical solution is schematically shown in FIG. 1. Problems to be Solved by the Invention However, in actual construction sites, most of the ground is complex and multi-layered, and the instant-setting chemical solution injected from the tip of the double-pipe rod can damage the voids and layers around the rod. The penetration state was extremely non-uniform, with the material escaping the boundaries and other weak spots and solidifying outside the planned injection area, away from the rod, while leaving unconsolidated areas within the planned injection area. It is extremely difficult to form a solid as shown in the figure. Further, escaping outside the planned injection range not only causes injection loss of the chemical solution but also causes ground upheaval, which is undesirable. The present invention has been made with the aim of eliminating such conventional problems. Means for Solving the Problems As a result of extensive research to eliminate the above-mentioned conventional problems, the present inventors have intermittently injected an instant-setting drug solution, and in the middle of the injection, there are cases where the previous injection occurs. When establishing an infusion stop period necessary for gelation of the drug solution,
It was discovered that the permeation state of instant-setting chemical liquids was significantly improved, and this led to the completion of the present invention. That is, the present invention uses a double pipe rod to inject an instant-setting chemical into the ground, and the chemical is continuously injected at each stage with a discharge rate of 10 to 20/min and a discharge time of 1 to 5 minutes. The present invention relates to a chemical liquid injection method that is carried out repeatedly and is characterized in that after each continuous injection, an injection stop period necessary for gelation of the chemical liquid is provided. The instant-setting chemical liquid used in the construction method of the present invention consists of liquids A and B as usual, and is injected into the target ground while being mixed at the tip of the double pipe rod. The gelation time and discharge rate of the instant-setting chemical solution are as per conventional methods, for example, the gelation time is about 0 to 15 seconds, and the discharge rate is 10 to 20 minutes. The instant-setting chemical solution is injected into the ground in multiple stages from the deep layer upwards as usual, and the injection time at each stage depends on the discharge amount, soil condition, improvement scale, etc. However, it usually takes about 3 to 15 minutes. The present invention is characterized in that the drug solution injection process is performed intermittently at each of these stages, and that an injection stop period necessary for at least one gelation of the drug solution is provided in the middle of the injection process. The injection stop time period only needs to be long enough to allow the previously injected drug solution to gel sufficiently, and it is sufficient if it is approximately equal to the gelation time of the normal drug solution, or slightly longer than this, Stopping the injection for a long time that far exceeds the gelation time is undesirable because it causes a delay in the work. If the continuous injection time of the drug solution is too long,
As with the conventional method, there is a risk of the chemical solution escaping outside the planned injection area, so it should be kept within a range that does not cause such escaping. Therefore, make an appropriate selection. In the present invention, following such continuous injection, the previous injection stop period is taken, continuous injection is performed again, and this is repeated as necessary. By repeating such continuous injection and stopping the injection,
In addition to improving infiltration conditions, it can prevent ground uplift and chemical loss. The reason for this effect is not clear, but by stopping the injection, the drug solution injected earlier becomes a gel during this period and becomes strong enough to function as a packer. The tendency of the injected chemical solution to escape after restarting is thought to be due to reasons such as being suppressed by this Packer effect and guiding the penetration of the chemical solution toward the unconsolidated area within the planned injection area. . In addition to the double pipe rod instant setting injection method, the method of the present invention is the first stage of the double pipe rod composite injection method, which combines the primary injection of an instant setting chemical solution and the secondary injection of a slow setting chemical solution. It can also be applied to injections. Examples Examples of the present invention will be given below to further clarify the characteristics of the present invention. Example 1 1) Chemical solution used Solution type water glass type (instant setting type) Gelation time 10see 2) Injection work conditions

[Table] 3) Soil Conditions The ground to be constructed is mainly composed of very soft sandy silt, and has a high water content.It is predicted that the natural water content ratio has already exceeded the liquid limit, and it is expected that the ground will be constructed under a slight external pressure. It was thought that it could be easily fluidized by change. Also, φ1800mm in contact with the upper part of the ground to be constructed.
Three buried pipes crossed diagonally, and the surrounding area was filled with backfilling soil (backfilling with generated soil: fine sand). 4) Construction status: Conventional method Because the sand layer is soft and fine, no change in pressure was observed during construction using only instant setting. (The injection rate is
The pressure was constant at 18/min, and there was no increase in pressure. ) This indicates a tendency for the injected material to escape outside the injection range, and the consolidated soil lacks continuity, causing sediment flow due to spring water from the discontinuous area, and the consolidated area Although it appears to be in a compressed state, the infiltration was not uniform and unimproved areas remained, which caused the collapse. Furthermore, as the injection material escapes, it may cause ground upheaval, raising the possibility of secondary failures. During interval construction When pouring, the pressure tends to rise little by little at each interval, indicating that the injection material spreads uniformly within the improved area and permeates, and compacted soil is consolidated as one piece without any discontinuities. There was no evidence of ground upheaval. In addition, the compacted soil had such high strength that it could be excavated with a pick, and its water-blocking properties were also very good. 5) Visual observation results of conventional construction face The condition of the face shows that compacts with high strength can be seen in some parts, but unimproved areas remained between the compacts. The unimproved part is
The infiltration of groundwater caused the sand to flow out and cause the face to collapse. In addition, the injection material was concentrated at the layer boundaries, and there were places above and below where no injection material was seen at all. During interval construction, the face was uniformly improved as a whole, there were almost no springs, and the degree of consolidation was extremely strong. The grout veins ran finely in all directions, and the presence of the injection agent was especially visible above and below the layer boundaries, and the consolidated gel made the improved soil extremely hard and allowed for smooth propulsion work. Example 2 1) Chemical solution used Solution type water glass type (instant setting type)
Gelation time 10sec Semi-suspension type water glass type (instant setting type)
Gelation time 10sec 2) Injection working conditions

[Table] 3) Soil conditions The ground targeted for injection consists of very soft clay soil (N = 0 to 1) and sandy soil from the top.
There are places where the clayey soil is intercalated with a slag layer, and the area is generally backfilled soil (polder land). The clay soil was mainly composed of soft silt, with alternating layers locally mixed with a large amount of sand. 4) Construction status Conventional method Since the soil is very loose and cohesive, there is a tendency for the injection material to run away and lift the road (asphalt pavement) mentioned above.
Because the injection material overflowed along the sheet pile, the injection speed was reduced from 20/min to 16/min (semi-suspension type and solution type). During interval construction, the patch car effect around the road became larger, no overflow was observed, and road upheavals were reduced. The clay soil was locally consolidated, the adhesive force in the injection area increased, the propulsion face was stabilized, and there were no problems caused by spring water. The homogel strength of semi-suspension type injection material is 0.8~
It is 1.0Kgf/cm ² , which is much higher than that of the solution type. The viscosity is approximately 4.5 cps/20℃, which is 3 to 4 times that of the solution type (approximately 1.2cps/20℃), so the distance traveled is less than that of the solution type, but the gel strength is greater, so it is difficult to maintain the ground. This is likely to cause upheaval, but because of the interval implementation, almost no ground upheaval was observed. 5) Visual observation results of conventional construction method The injection material can be seen in thick veins in the clayey soil, but the soil has not been consolidated and the degree of improvement is poor. There was an outflow of water, making it difficult to proceed. During interval construction, the condition of the face was such that thin grout veins ran in all directions, and a uniform improvement effect was observed. In particular, there was no runoff of earth and sand caused by spring water, and it was possible to control the ground upheaval seen with conventional construction methods. Example 3 1) Chemical solution used Solution type water glass type (instant setting type)
Gelation time 10sec 2) Injection working conditions

[Table] 3) Soil conditions It is a boundary between a diluvial layer and an alluvial layer, and exhibits a variety of alternating layers.The soil layer sandwiching clayey soil has a low N value, and the soil is a multilayered ground with a high moisture content overall. be. 4 Construction status Conventional method Construction was carried out using the double pipe rod type instant injection method, but the ground was so heavily raised that it was almost impossible to accept the injection material. Therefore, when the pipe is propelled, collapse of the face and spring water are serious,
This became an obstacle to the promotion work. During interval construction As a result of interval construction, it was confirmed that there was almost no ground upheaval and the injection pressure increased with each interval. Even under the conditions of propulsion, it was possible to proceed smoothly with almost no problems. 5) Visual observation results of conventional construction method The ground targeted for this construction had very complex alternating layers, and the injection material escaped along the periphery of the injection hole, and almost no injection material could be seen within the improved area. Therefore, during pipe propulsion, spring water and the face collapsed repeatedly, making the propulsion work extremely difficult. During interval construction, the condition of the face is that the injection material runs in veins at the boundaries of each layer.
Consolidated clay soil and dewatered sandy soil were observed. In particular, the clay soil has thin grout veins running through it, and it is thought that the injection material running along the layer boundaries was controlled by the interval and then ran to other soft areas. Example 4 1) Chemical solution used Solution type water glass type (instant setting type)
Gelation time 15sec 2) Injection working conditions

[Table] 3) Soil condition No. 1 The improvement range is silt-mixed medium sand to coarse sand from the upper part,
It consists of sand and silt layers mixed with floating stones, and is an alternating layer with a low N value. No. 2 The improvement range is from the top: coarse sand, silty fine sand,
It consists of alternating layers of clay and fine sand, and the N value also varies. The ground to be constructed is medium to loose sandy soil and soft clay soil, the groundwater level is relatively high, and there are concerns about soil runoff due to spring water.
In addition, sandy soil contains a large amount of fine particles, making it difficult to improve the ground. 4) Construction status Conventional construction method The design was based on the double pipe rod type instant injection method, and as a result of construction, the road ground was raised and the flow rate was reduced from 18/min to 12/min. Only about 1/2 of the planned amount could be injected. (Due to significant ground upheaval, construction work was suspended.) Many of the areas to be improved were unimproved, and mirror cutting of the starting area was also possible. During interval construction, there was almost no ground upheaval, and the improved soil was in a continuous state, so picks were used to promote the work. 5) Visual observation results of conventional construction method: The injection material was concentrated at the layer boundaries, and uniform improvement was not possible. In particular, the injection material traveled around the rod and deviated to the boundary of the upper layer, causing ground upheaval. During interval construction, the grouting material formed fine grout veins not only at the layer boundaries but also throughout the area, and uniform ground improvement was achieved. In addition, the strength developed to the extent that a pick was used during excavation. Example 5 1) Chemical solution used Solution type water glass type (instant setting type)
Gel time 10sec〃 (slow setting type)
Gelation time 3-10min 2) Injection work conditions

[Table] 3) Soil conditions The ground for this construction work will be filled with backfill soil from the top.
Silty sand, medium-fine sand, coarse sand (including gravel layer)
In particular, there were many buried pipes installed in the backfill soil at the top, and there were concerns about their impact during propulsion. In addition, the reaching part is in contact with a river,
It was predicted that the high groundwater level and the inflow of groundwater from the lower layer would become obstacles to the promotion work. 4) Construction status Conventional construction method As a result of construction using the double pipe rod type composite injection method, the backfill soil rose abnormally and there was a risk of damaging the existing buried pipes (φ400mm water supply, φ800mm public water, electrical pipes, etc.) Due to this occurrence, injection was temporarily suspended.
A combination of intervals was used. During interval construction As a result of using interval construction, ground upheaval subsided and the injection conditions were good. In particular, the interval when switching from instant setting to slow setting is considered to be very effective, contributing to controlling the overflowing of the injection material around the rod, and suppressing ground upheaval. 5) Visual observation results of conventional construction method The upper part of the face was in good condition and was strong enough to use an air pick. However, the amount of spring water at the lower part of the face was large, causing fine sand particles to flow out and becoming an obstacle during box propulsion. (It is judged that this will not be a problem in the case of circular propulsion such as Huyum pipes.) In addition, the injection material was concentrated around the buried pipes and at the layer boundaries. During interval construction, the face condition has been uniformly improved, and grout veins are not so visible.
The solids had continuity and exhibited extremely high strength. In addition, a water stop layer has been formed at the bottom of the face, and the water is not as good as spring water.
There was only a small amount of water coming in from behind the box. Effects As described above, the construction method of the present invention has the characteristics of improving the penetration state of the chemical solution and preventing its escape, improving the reliability of ground improvement, and reducing the loss of the chemical solution.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the double pipe rod instant connection injection method.

Claims (1)

[Claims] 1 When injecting instant-setting chemical liquid into the ground using a double pipe rod, the chemical liquid injection at each stage is controlled by the discharge amount.
A chemical liquid injection method, which is carried out by repeating continuous injection at 10 to 20/min and a discharge time of 1 to 5 minutes, and after each continuous injection, an injection stop period necessary for gelation of the chemical liquid is provided.