JPS5810529B2 - How to strengthen weathered rock - Google Patents

Description

[Detailed Description of the Invention] The present invention improves weathered rock that has a low moisture content, is not filled with water, is heterogeneous in strength, brittle, and easily deformed, and has a high overall strength and is difficult to deform. It concerns a method to make the properties of each part homogeneous.

Weathered rock has a complex soil composition, uneven strength, and is brittle.

Therefore, when attempting to construct a structure such as a tunnel on weathered rock that is fragile, has a low water content, and is not filled with water, excavating the rock without taking any protective measures may cause deformation of the rock. It is also extremely dangerous as it can grow large enough to affect surrounding structures, and in extreme cases may even collapse.

The inventor of the present invention has developed weathered rock that has a low water content ratio, is not filled with water, is heterogeneous in strength, and is brittle and easily deformed.
As a result of intensive research aimed at developing a construction method that has high overall strength and is resistant to deformation, while also making these properties uniform in each part, it was found that the above-mentioned rock is unique because it contains a small amount of water. With a simple freezing method, the ice layer that binds the bedrock and soil particles is not sufficiently formed, so it cannot be strengthened. If cracks in the rock are filled with water and then frozen, the water will freeze and act as an adhesive in areas with uneven strength, resulting in the entire area to be frozen. The present invention was achieved based on the knowledge that frozen rock has high strength and is difficult to deform, and that these properties can be formed into a frozen rock that is homogeneous in various parts.

That is, the present invention supplies moisture to weathered rock that has a low moisture content and is not filled with water, causes the rock to absorb water, and freezes the rock while filling its cracks with water, thereby completely damaging the rock. Its main characteristics are that it has high strength and is difficult to deform, and these properties form a homogeneous frozen product in each part.More specifically, it has a low moisture content and is not filled with water. An appropriate number of frozen pipes are buried in the area of the weathered rock that is to be strengthened, and an appropriate number of water injection pipes are buried at an appropriate distance from the frozen pipes, and an appropriate amount of water is injected and dispersed from the water injection pipes into the area. After sufficiently supplying moisture to the area, a suitable amount of water is further supplied and a refrigerant is passed through the freezing pipe to freeze the ground and water in the area together, thereby freezing the area as a whole. It is characterized by high strength and resistance to deformation, and these properties allow it to be formed into a frozen product that is homogeneous in all parts.

Next, embodiments of the present invention will be described with reference to the drawings.

G is a weathered rock mass with a low water content that should be strengthened to excavate a tunnel, etc., and 1 is placed on the construction surface of the rock mass G on which work to strengthen the weathered rock mass G is to be carried out, and on the excavation surface in the vicinity thereof. 2 is a large number of freezing pipes buried horizontally from the water stopping wall 1 to the region A of the rock wall G to be strengthened; 3 is a freezing pipe buried above the freezing pipe 2 in the same way as limb pipes. With the water injection pipe,
Both the freezing pipe 2 and the water injection pipe 3 are treated with caulk C to stop water between their mouths and the water stop wall 1.

H is the area of weathered bedrock G to be excavated. Therefore, in order to strengthen the weathered bedrock G, first, water is sprayed sufficiently from the water injection pipe 3 onto the area A to be strengthened to provide sufficient moisture to the area A and also to strengthen the small areas of the bedrock in the area A. Make sure the rack is filled with water.

Next, the refrigerant is passed through the freezing pipe 2 to start freezing, and the amount of water sprayed from the water injection pipe 3 is reduced, and the work is continued in the cleaning area A while controlling the amount to a level that does not interfere with freezing. The bedrock begins to freeze from the small cracks around the freezing pipe 2 and gradually closes the cracks, and the passage through which the injected water flows gradually gets pinched, and eventually this narrowed waterway also freezes and becomes blocked. The rock in Area A has high overall strength and is resistant to deformation because frozen water acts as an adhesive in parts of the rock where the strength is uneven, but these properties are homogeneous in each part. It is formed by Freezer F.

In addition, in the above, after the start of freezing, reduce the amount of water injection,
In the end, if the amount of water sprayed is not reduced, it is necessary to control the water so that there is no problem with freezing.After freezing starts, if freezing begins to occur from the small rack around the freezing tube 2, the path of the injected water gradually closes. Water is stored in the bedrock of area A, and as the amount of stored water increases, the water pressure increases and is narrowed into several channels, causing the flow speed in those areas to increase. This is because the amount of heat brought in by the injected water makes it difficult for the area to freeze and blockage, and the amount of water sprayed is ultimately determined by the amount of heat removed by the freezing tube 2 than the amount of heat brought in by the water. The actual amount differs depending on the type and quality of the rock, but for example, in the case of weathered granite, the freezing pipe 2
It is desirable that the movement of nearby water be 200cc/min/m2 or less.

In addition, instead of simply using fresh water for water spraying, CM
By using water mixed with a thickener such as CO, the water retention capacity of the rock can be increased and the flow rate can be easily adjusted.

A useful water spraying method when carrying out the method of the present invention is to connect the water injection pipe 3 to the inner pipe 31. It is a double tube consisting of an outer tube 32, and a large number of slit-shaped water holes 33 are provided in the outer tube 32, so that water supplied to the inner tube 31 flows between the inner tube 31 and the outer tube 32, and the water fill holes 33 are provided in the outer tube 32. 33 into the area A, and water pressurized using a water head difference or a pump, or water mixed with a thickener, is added to the inner pipe 31 to prevent the progress of freezing. This is a method of supplying while adjusting and controlling the amount so that it does not overflow, and when using the difference in water head,
A tank T is arranged so that the water head difference is at least 1.5 m, and contains fresh water or water adjusted to a predetermined viscosity by mixing a thickener therein, and the tank T and the water injection pipe 3 are A dispensing header 4 is disposed between them, and a large number of water pipes S provided in the header 4 are individually connected to the inner pipe 31 of the water injection pipe 3, and water from the tank T is supplied to the inner pipe 31. Water is supplied through the water pipes S and sprayed in the area A from the water injection hole 33 of the outer pipe 32, and each water pipe S is provided with a flow meter 5 and a valve 6, and
A pressure gauge 7 is provided on the outer pipe 32 of the water injection pipe 3, and the flow rate and pressure are appropriately adjusted by the valve 6. On the other hand, when a pump is used, water from the water source is appropriately stored in the tank T1, The water is sent from the tank T1 to the tank T2 by a pump 8, and a header 4 for dispensing is provided between the tank T2 and the water injection pipe 3, and a pump 9 and a relief valve R are provided between the tank T2 and the header 4. Then, the water in the tank T2 is sent to the header 4 by the pump 9, and fresh water is supplied from the header 4 to the inner pipe 31 of the water injection pipe 3 in the same way as in the previous case, or the water from the tank T2 is provided separately. Tank T
3 with a pump 8, water mixed with a relatively large amount of CMC is made in the mixer M, and is sent into a tank T8 with a pump 10, and CMC mixed water with a predetermined concentration is made in the tank T8, and this is poured into the tank T2. After feeding, connect the water injection pipe 3 from the header 4 in the same way as above.
The water is supplied to the inner pipe 31 of the header 4, but in order to prevent the pressure of water from the pump 9 from exceeding a predetermined pressure on the header 4, it is adjusted by the relief valve R, and the flow rate from the header 4 and the pressure inside the outer part 2 are adjusted by the valve 6. Please adjust accordingly.

As described above, water is supplied to the water injection pipe 3, and the weathered rock G
By doing so, water can be supplied to the area A extremely smoothly.

The present invention is as described above, by supplying moisture to weathered rock that has a low moisture content and is not filled with water, causing the rock to absorb water, and freezing the cracks etc. filled with water. The overall strength of the rock is high and it is difficult to deform.
However, since these properties are a method of strengthening weathered rock that has a low moisture content and is not filled with water by forming a homogeneous frozen rock in each part, it is relatively easy to strengthen weathered rock that has a low moisture content and is not filled with water. Weathered bedrock can be strengthened, and therefore, when building structures such as tunnels on the rock, if the method of the present invention is adopted to strengthen the rock, the impact on surrounding structures can be reduced and the construction can be carried out safely. can be done.

In fact, the method of the present invention was applied to strengthen weathered granite rock in Nunobiki, Kobe City, Hyogo Prefecture, which is located above the groundwater level, using a mixture of 0.1% CMC in water. ), a pit 2 m high, 3 m wide, and 12 m deep was excavated and the results were investigated, and it was found that the reinforcement was extremely effective as shown below.

1) Elastic modulus investigation test The elastic modulus at a point approximately 4 m from the mine entrance before freezing was 9.
12X103 (Kt/cm2), but after freezing it was 2.46X104 (Kf/cm2), and the elastic modulus at the time of freezing was approximately three times that before freezing, and freezing increased the rigidity of the ground. In other words, it was found that the resistance to deformation was increased.

2) P-wave investigation As a result of the P-wave investigation on the upper part of the pile, the P-wave velocity increased approximately 2.25 times after freezing compared to before freezing, and furthermore, before freezing, the P-wave velocity increased to around 9 m from the mine entrance. Although changes were seen,
After freezing, the value was uniform up to around 12m from the mine entrance.

This shows that the ground has become uniform after freezing.

3) Unconfined compression test As the temperature of frozen soil decreases, the unconfined compressive strength (qu) increases, and the strength (qu) at -10°C is approximately 200 Kf/cm2.
So, compared to about 60 to 7/cm2 at room temperature (15℃), 3
It was found that the number has more than doubled.

4) Others No displacement due to freezing was observed.

[Brief explanation of the drawing]

Figure 1 is a front view of the state in which a water stop wall has been installed on the weathered rock that needs to be strengthened, and the freezing pipe and water injection pipe have been buried. The figure is a sectional view of the water injection pipe, FIG. 4 is a schematic diagram of an example in which water is supplied to the water injection pipe by a water head difference, and FIG. 5 is a schematic diagram of an example in which water is supplied by a pump. G... Weathered bedrock, A... Region of weathered bedrock to be strengthened, F
... Frozen rock, 1 ... Water stop wall, 2 ... Frozen pipe, 3 ... Water injection pipe, 31 ... Inner pipe, 32 ... Water injection hole, 4 ... Hesogu,
S... Water pipe, 5... Flow meter, 6... Valve, 7... Pressure gauge, 8, 9, 10... Pump, T, Ti9T2? T8...
Tank, M...Mixer.

Claims (1)

[Scope of Claims] 1. Water is supplied to weathered rock that has a low moisture content and is not filled with water, and the rock is made to absorb water, and the cracks, etc., are filled with water and then frozen, thereby turning the rock into a whole. A method for strengthening weathered rock, which is characterized by forming frozen rock that has high mechanical strength and is difficult to deform, and has these properties uniformly in each part. 2. Bury an appropriate number of frozen pipes in areas to be strengthened of weathered rock that has a low moisture content and is not filled with water, and bury an appropriate number of water injection pipes at an appropriate distance from the frozen pipes, and from the water injection pipes. After injecting and dispersing an appropriate amount of water into the area to sufficiently supply moisture to the area, while supplying an appropriate amount of water, a refrigerant is passed through the freezing pipe to integrate the rock and water in the area. A method for strengthening weathered rock, characterized in that by freezing, the region is formed into a frozen rock that has high overall strength, is difficult to deform, and has homogeneous properties in each part. 3. The method for strengthening weathered rock according to claim 1 or 2, in which water mixed with a thickener is used as water to be supplied to weathered rock that has a low moisture content and is not filled with water.