JPH0252069B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for constructing shotcrete on spring or wet surfaces such as tunnels and underground structures. BACKGROUND ART Conventionally, methods of using shotcrete as shoring for tunnels and underground structures have been known. This construction method uses compressed air to forcefully feed unhardened concrete through a pipe or hose, and discharges it from a nozzle at the tip onto the spraying surface. No formwork is required, and relatively uniform construction is possible even on uneven surfaces. Addition of an accelerating agent has the advantage that solidification can be achieved relatively easily in a short period of time.
Construction methods are broadly divided into wet and dry methods; in the former, pre-kneaded concrete material is pumped and sprayed as is, while in the latter, cement and aggregate are mixed in the air (dry mix) and then pumped, and water is added at the nozzle. The spraying process is carried out using the following methods. However, this shotcrete construction method, whether wet or dry, is difficult to apply on spring surfaces or wet surfaces (infiltrated surfaces).
The basic problem is that the adhesive strength is not sufficient and peeling and collapse occur, making it difficult to carry out the required construction. Conventionally, measures have been taken to deal with this, such as increasing the rate of addition of quick-setting agents, or, in the case of dry systems, adjusting the amount of water supplied at the nozzle according to the amount of spring water, but appropriate measures have been taken. It was difficult to say that it was a cure, and the construction was extremely difficult, as it required the installation of drainage pipes and waterproof sheets. The present invention was made with the aim of solving this problem, and provides a method that allows shotcrete construction to be performed directly on spring water surfaces or wet surfaces such as tunnels, underground structures, etc. That is, the present invention provides a method for spraying unhardened concrete onto a spring surface or a wet surface using a spray nozzle, by blending an adhesive into the unhardened concrete so that it satisfies predetermined conditions. It is something that makes it sticky, more specifically,
400 c.c. of cement paste with a water-cement ratio of 60% is placed in a cylindrical container with a diameter of 5 cm and a height of 40 cm filled with 400 c.c. of water.
According to the test method, the cement is allowed to flow down from above the water surface, left to harden, and samples are taken from the top 5 cm and the bottom 5 cm of the hardened cement and the specific gravity of both is measured. The method is characterized in that a thickening agent that makes the difference in specific gravity between the two samples 0.1 or less when mixed is mixed in a weight ratio of 0.1 to 4.0% with cement in the route from the spraying machine to the spraying nozzle. Thickening agents used in the present invention include polyvinyl alcohol, polyacrylamide, polyethylene oxide, sodium polyacrylate, carboxymethyl cellulose, methyl cellulose, cellulose ethers represented by these, sodium alginate, guar gum, Korean silver, etc. Grass or similar thickeners may be used, and these may be added singly or in combination so as to satisfy the above conditions. Incidentally, as the cement used, conventionally known common cements can be used, but it may be advantageous to use early-strengthening cement. Moreover, a part of it can be replaced with fly ash, granulated slag powder, siliceous mixture, etc., and the object of the present invention may be advantageously achieved by this replacement. In producing the concrete of the present invention, there are no restrictions on the type of aggregate, including fine aggregate and coarse aggregate, and any type of aggregate can be used. The present invention is also useful in cases such as cement mortar that does not use coarse aggregate. According to the tests conducted by the present inventors, when the adhesive was mixed so that the difference in specific gravity of the samples collected by the above test method was 0.1 or less, the sprayed surface It was confirmed that even if there was spring water, the shotcrete would not be washed away by the spring water and sag, and a strong concrete layer would be formed over the entire surface of the sprayed surface. If this specific gravity difference exceeds 0.1, the cement will be washed away into the spring water during construction, making it impossible to form a highly reliable shotcrete layer. This specific gravity difference
The amount of thickening agent added to achieve a value of 0.1 or less varies depending on the cement adhesion effect of the thickening agent.
If the weight ratio to cement is less than 0.1%, such an effect cannot be achieved, and if the amount is more than 4.0%, the curing reaction of cement may be delayed, which is not practical. However, this addition amount is based on the assumption that the thickening agent has been sufficiently mixed with the cement, and if the mixing is insufficient or the type of thickening agent that does not mix uniformly with the cement fine particles even if thoroughly mixed, In the case of a thickening agent, it is necessary to add it without being particular about this range of addition amount. However, the conditions must be met so that the difference in specific gravity is 0.1 or less when the above test method is followed.
In other words, it is essential to satisfy the condition that the specific gravity difference is 0.1 or less in this test method, and as long as this requirement is met, it is preferable for actual operation to use a viscosity of 0.1 to 4.0% by weight relative to cement. A thickening agent may be added, and the amount can be adjusted to an appropriate amount within this addition range depending on the amount of spring water on the surface to be sprayed and the degree of wetness. By adding a thickening agent in the above range according to these conditions, concrete with adhesion and hardening properties similar to ordinary shotcrete without spring water or moisture can be formed in spring water or wet areas, and can be rapidly When a binder is used in combination, it does not adversely affect the performance of this quick-setting agent or the physical properties of concrete after hardening. In addition to the above-mentioned resistance to spring water, the combination of this thickening agent has the effect of suppressing the generation of dust and the effect of suppressing splashing during spraying work, improving the working environment. You can also contribute. When carrying out the method of the present invention, viscous concentrate is added and blended in the route from the spray machine to the spray nozzle (including the spray machine). To explain in detail according to the drawings, Fig. 1 shows examples of wet spraying, and Figs. 2 to 4 show examples of dry spraying. In the figures, 1 is a mixer, 2 is a spraying machine, and 3 is a spraying A spray nozzle is shown, and the spray machine 2 discharges the spray material using compressed air. In the wet spraying shown in Fig. 1, in the mixer 1, cement C,
Fine aggregate S, coarse aggregate G, and water W are kneaded and sent to a spray machine 2, where a thickening agent 5 is applied at a position near the nozzle of a pipe 4 leading from the spray machine 2 to a spray nozzle 3. It is added and blended. In addition, this thickening agent 5
Together with or separately, an accelerating agent 6 is added. In the dry spraying shown in Figs. 2 to 4, cement C, fine aggregate S, and coarse aggregate G are mixed in a mixer 1 and sent to a spraying machine 2.
Water W is added to the pipe 4 at a position near the nozzle 3 through which this dry mix is conveyed toward the spray nozzle 3, and as a result, water-containing kneaded concrete is sprayed from the nozzle 3.
In the case of Fig. 2, the thickening agent 5 is added after this water W is added and before the nozzle 3, and in the case of Fig. 3, the thickening agent 5 is added to the added water W to make it viscous. It is added to dry mixes as a solution in which Agent 5 is dissolved or suspended. Figure 4 shows an example in which the thickening agent 5 is added to the dry mix before adding water W in the pipe line 4 leading from the spray machine 2 to the nozzle 3, and Figures 5 and 6 show the case of the spray machine. 2 shows an example in which a thickening agent is added. In addition, in FIGS. 2 to 6, 6 represents an quick setting agent. There are other combinations of adding positions for the thickening agent and/or quick-setting agent other than those shown in the figure, but basically the thickening agent is added to the path from the spraying machine 2 to the spraying nozzle 3 (including the spraying machine). ) is convenient for actual operation, and whether to add it in powder form or liquid form may be determined as appropriate depending on the addition position. In either case, it is necessary that the thickening agent is well dispersed in the unhardened concrete discharged from the spray nozzle 3, so that spring or running water on the spray surface will not form. However, shotcrete can be formed that is no different from that of a normal shotcrete surface where these do not exist. As described above, according to the method of the present invention, shotcrete can be easily and reliably applied to surfaces with spring water or wet surfaces (infiltrated surfaces), which have conventionally been difficult to perform, while suppressing the generation of dust. In addition, it exhibits an excellent effect that conventional methods do not have, such as reducing splashback, and it is possible to produce shotcrete with good workability and good adhesion and setting hardening properties using conventional equipment without the need for additional special equipment. Obtainable. Example 1 Water was placed in a cylindrical polyethylene bag with a diameter of approximately 50 mm.
Pour 400 c.c. of cement paste into it from above the water surface, leave it to harden, and divide the cured product (cylindrical shape with a height of about 200 mm) into 4 equal parts. and measure their unit volume weight. The height of one section to be divided is approximately 50 mm. In this test, hydroxyethylcellulose was used as a thickening agent, and the water-cement ratio was 100%, 60%,
The thickening agent was changed to three levels of 40%, and the thickening agent was added using the dry mix method (adding it in powder form and kneading it), the dissolution method (adding it dissolved in water and kneading it), and the post-addition method. Three methods (method of adding after mixing) were carried out when the amount of thickener added (ratio to water) was 0.5% and 1.0%. The unit volume weight (Kg/m ³ ) of each section divided into four sections is shown in Figure 7 (added amount of thickening agent is 0.5%) and Figure 8 (the same
1.0%). These results show that when the water-cement ratio is 60% or less, when 1.0% of this thickening agent is added, the difference in specific gravity between the top section and the bottom section becomes 0.1 or less. In this case, regardless of the method of adding the thickening agent, the difference in specific gravity will be
It will be 0.1 or less. Figures 9 and 10 show the compressive strength of specimens produced in air and in water at 28 days of age when hydroxyethylcellulose was added as a thickening agent in different amounts (ratio to water). This is what is shown. The in-air fabrication specimen was 5cmφ×10 in accordance with JIS A1132 “How to make specimens for concrete strength testing”.
The specimen had dimensions of cm. The underwater fabricated specimen is at the depth of the water.
A cylindrical formwork with an internal volume of 5cmφ x 10cm is placed at the bottom of a 60cm water tank, and cement paste is passed through the water toward the formwork from above the water surface, continuously adding 10 to 20% more than the capacity of the formwork. After 1 to 2 hours of pouring into the formwork, the water in the water tank was drained, the formwork and excess cement paste were removed, and the cement paste was allowed to harden.
The aerial fall distance above the water surface is 15 cm. At first glance, FIGS. 9 and 10 appear to show different compressive strength behavior. However, as shown in Figure 11, when plotting the ratio of the compressive strengths in Figures 9 and 10, the amount of thickener added is 1.0.
In all of the water cements mentioned above, the ratio is concentrated within the range of 0.7 to 1.0, and the variation in strength is extremely small. When the amount of thickener added is 1.0 or more, the difference in specific gravity between the uppermost section and the lowermost section is 0.1 or less, as shown in FIG. 8. The results shown in FIG. 11 have an important meaning in the spraying construction of spring water surfaces that harden in a mixed phase state of air and water. In other words, the thickening agent-containing concrete defined by the present invention forms a good hardened surface with consistent quality even on slopes where spring water exists. Example 2 A spring surface with a spring water flow rate of 17/min/m (meaning the spring water flow rate per 1 m width per minute is 17) was artificially created and the spraying construction of the present invention was carried out. The mix of concrete and the amount of thickening agent added were varied as shown in Table 1. The adhesion status of the obtained concrete is also listed in Table 1. The thickening agent used was hydroxyethylcellulose, and the construction method was
I followed the method shown in the figure. From the results in Table 1, it can be seen that according to the method of the present invention, a concrete sprayed surface with sufficient strength could be formed with good workability.

[Table] Example 3 Tables 2 to 4 show examples of actual implementation of the method of the present invention. Table-2 is power plant construction, Table-2
3 is an example of construction on an expressway, and Table 3 is an example of construction on a spring surface in an underground power plant, and good results were obtained in both cases.

【table】

【table】

【table】 [Brief explanation of drawings]

Figures 1 to 6 are process diagrams of a shotcrete construction method showing an example of the method of the present invention, and Figures 7 and 8 show a hardened body containing a thickening agent prepared according to the present invention. A diagram showing the unit volume weight (Kg/m ³ ) of each section divided into four sections, and Figures 9 and 10 show the material age of the in-air fabrication specimen containing a thickening agent and the underwater fabrication specimen.
FIG. 11 is a diagram showing the compressive strength on the 28th day, and is a diagram plotting the ratio of the compressive strengths in FIGS. 9 and 10. 1... Mixer, 2... Spraying machine, 3... Spraying nozzle, 4... Route from the spraying machine to the spraying nozzle, 5... Thickening agent, 6... Rapid setting agent, C... Cement, S...fine aggregate, G...coarse aggregate, W...
water.

Claims (1)

[Claims] 1. A cylindrical container with a diameter of 5 cm and a height of 40 cm containing 400 c.c. of water when spraying unhardened concrete onto a spring surface or a wet surface using a spray nozzle. Cement paste with water-cement ratio of 60% in 400
A test method was followed in which cc was allowed to flow down from above the water surface, allowed to stand and harden, and samples were taken from the top 5 cm and bottom 5 cm of the hardened cement and their specific gravity was measured. Sometimes, a thickening agent that sticks between cement particles and makes the difference in specific gravity of both samples 0.1 or less is added at a weight ratio of 0.1 to 0.1 to the cement in the route from the spray machine to the above-mentioned spray nozzle.
A shotcrete construction method for spring or wet surfaces characterized by a 4.0% mix.