JPS621078B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a means for efficiently performing backfilling along the outer periphery of a lining tube formed by segments in a shield construction method in response to the diversity of the excavated ground, and at the same time obtaining excellent strength. It is something. The shield construction method, which is widely used when constructing various tunnels and culverts, has become stable after much research and experience, but the backfill method determines the success or failure of the shield construction method. Regarding filling, there are many conditions and factors that need to be resolved in order to immediately respond to the geology of the region including the construction site and the conditions of the construction site, and to bring benefits during construction and ensure strength preservation after construction. It was. Needless to say, in the shield construction method, a tunnel-like plain excavation is excavated along the outer shell of the shield excavator, but a lining segment tube (a cylindrical structure made by combining gutter-like segments) is then excavated. Since the pipe (hereinafter referred to as segment) is assembled at the tail part of the shield excavator, a tail void will inevitably occur between the excavated stratum and the outer surface of the segment. Immediately fills the tail voids that occur immediately after excavation by the shield excavator, develops enough strength to counteract the extrusion pressure of the ground in a short period of time, prevents the loosening of the ground that is about to occur, and subsides the ground. In addition to preventing the impact on existing structures, it also achieves water stoppage in the working tunnel and equalization of earth pressure applied to the segments. Various proposals have been made. In other words, the filling materials include aggregate-based materials such as pea gravel concrete or sand mortar, clay-based materials such as clay sand air mortar, and non-aggregate materials such as chemical injection. Many attempt to resolve the relationship between injection into the tail void and rapid consolidation at the filling point. However, according to these above measures,
Problems in transporting materials include the difficulty of transporting them using pressure pipes, poor workability, and injecting cannot reach the entire length of the segment, and problems with the kneading properties of the filler, which tend to cause material separation and water outflow. If the soil is easily damaged or the tail packing part escapes, normal injection may be lost, leading to ground subsidence. It was extremely difficult to set up proper injection and filling as there was a lot of excessive penetration into the ridges. The inventors of the present invention have previously developed a method that solves the problems of backfilling as described above and does not require high construction costs like chemical injection (Japanese Patent Application Laid-open No. 147627/1983 and
39564), the filling material and coagulant are sent separately and mixed at the filling point, which enables long-distance pressure feeding, improves fluidity, improves the filling rate, and speeds up the rise of the setting time. We have proposed a method that develops early strength, has a good water-stopping effect, and has a sufficient backfilling function.However, in these methods, the amount of cement in the filling material is kept constant, and the amount of coagulant added changes the gel time of the injection filling material. However, it is difficult to centrally control the correlation between gel time and developed strength or the working environment temperature and gel time, and when air mortar is used as a filling material, the volume increases due to the contraction of air bubbles due to pressure feeding. There was a concern that the temperature inside the mine would rise due to the exhaust heat from the working machines, and that the filling material would harden without the addition of coagulant and clog the pumping pipe. The present invention was created in consideration of the current situation,
By making the backfilling material have unique properties, it maintains a sufficient pot life and prevents the moisture contained in it from escaping from various parts including the tail packing and from excessively penetrating into the ground. The purpose of this paper is to propose a method for effective backfilling of tail voids by eliminating digging and effectively reaching the filling local area.To this end, the mode of the backfilling material when injected into tail voids is as follows: By combining the backfilling material with a specific composition with a coagulant instead of forming it into a solution (liquid) or slurry as seen in conventional methods, the backfilling material becomes transformable during injection. A backfilling material with a rich viscous bond (jelly-like) is injected in synchronization with the generation and expansion of tail voids caused by the advancement of the shield excavator in the shield jack. It shows a mechanism that allows filling that follows the shape of the tail void to avoid succumbing to earth pressure and has a pot life that allows solidification through rapid solidification, and satisfies many of the conditions required for backfilling. The purpose is to provide a backfilling method that can fully satisfy the requirements. Furthermore, even when shield excavation is applied to a long tunnel, it is possible to prepare the backfilling material for injection outside the mine and extend it over a considerable distance without interfering with underground operations and where there is less risk of temperature rise. Even if the pumping time is extended by adding additives that can maintain fluidity, it is still possible to instantly create a viscous bonded plastic body that is highly deformable by mixing and bonding with a coagulant as described above. We also use a backfilling method that satisfies the various conditions required for backfilling, as well as the backfilling materials and coagulants used in both methods, as well as the changes brought about by mixing and combining them. The ultimate objective is to provide a backfilling material that is a viscous bonded plastic body with rich properties. Next, to specifically explain an example of the implementation of the present invention, the backfilling material is kneaded into a cellular mortar containing an extremely large amount of closed cells by selecting and combining appropriate composition materials, and The backfilling material with such properties is transported from the outside of the mine or other kneading locations to the shield tail via a conduit using a grout pump, etc. lead Then, it is fed into a mixer installed close to the injection port of the lining segment that follows the shield excavator, where it is mixed with and combined with the coagulant sent separately through a pipe, and the coagulation effect is achieved. The backfilling material has a sufficient pot life when it is kneaded into a plastic material that can be expressed and injected from the injection port provided in the lining segment in synchronization with the generation and expansion of tail voids due to the advance of the shield excavator. The rising state of condensation is reached through
After that, it solidifies rapidly. When the backfilling material used in the method of the present invention or the backfilling material obtained by mixing a coagulant with the backfilling material obtained with such properties is in a state within the pot life immediately after injection, the pipe The tendency for weight loss resulting from the compression of the bubbles due to the added pressure for in-line pumping is compensated for by the swelling of the bentonite-like qualities contained in the clay-mineral body material in the composition, keeping the volume relatively constant; It retains its greatest feature, deformability, and exhibits mobility and workability, and because of this characteristic, it can seep into various escape-inducing areas such as joints, gaps in the ground surface, or pores. It exhibits water-stopping properties and volume stability with an occluded contact mode. Unlike the solution or slurry used in conventional methods, the backfilling material used in the present invention is in a highly deformable and viscous bonded state, and in this state, it is injected from the segment injection port and is densely distributed in the dorsal portion of the segment. During filling, it exhibits a sufficient pot life and exhibits excellent properties as a filler. A backfilling material is made by blending a substance that has an interfacial action and can stably sustain foaming as closed cells, and a plasticity enhancer that acts on the coagulant to form an instant bond when it meets the coagulant. None, this backfilling material is mixed with a sodium silicate (water vitreous) medium as the coagulant to obtain a backfilling material that is a viscous bonded plastic body with extremely high deformability, and has this property. (a) So-called gel time exhibits instantaneous plasticization almost regardless of the working atmosphere temperature, and is a highly deformable jelly-like material that can be effectively distributed and filled into the tail void. (b) Since there is no leakage from the tail packing, each part can be filled uniformly and reliably. (c) It has a great water-stopping effect. (d) This backfilling method is simple as a construction method, so
It does not compete with or interfere with shield excavation work, (e) It can be applied to any soil type or situation, and is especially effective in ground with a lot of spring water, (f) It can backfill the composition of a permanent structure. By using the filling material, it is ideal for filling tail voids. , injection filling for each follow-up extension of the segment or simultaneous injection can be easily performed. In addition to the above-mentioned compositional components, the backfilling material of the present invention can be pumped over long distances through pipes by adding an appropriate amount of hydroxycarboxylic acid or hydroxycarboxylate as a setting retarder for hydraulic cement. It does not lose its fluidity even over long periods of time, and furthermore, it promotes gelation when mixed with a coagulant, and can be pumped through pipes without causing coagulation or loss of consolidation strength of the backing filler. The extremely easy extension distance has been greatly increased, making it possible to accommodate the extension of the construction work without moving forward the kneaded part of the backfilling material, and furthermore, by using the backfilling material with such characteristics. It is not necessary to mix the backfilling material in each period of pressure-feeding and filling, and it is possible to stock a certain amount, reducing the number of man-hours of filling work, and furthermore, it is possible to use the mixed filling material every other time. It is an advantage of the present invention that this can be achieved. The backfilling material included in the present invention is a highly deformable viscous bonded plastic body, which will be made clear by the following description. In other words, the backfilling material has properties that provide fluidity, workability, water-stopping properties, and volumetric stability that can withstand long-distance transportation, and by mixing it with a coagulant, rapid bonding and pot life can be achieved. This is the backfilling material shown. Therefore, in the present invention, a small amount of a substance is added as a component of the cellular mortar system to create an instantaneous bonding state between the coagulant and the coagulant, thereby promoting the action of forming a plastic body with high deformability. It contains chloride and calcium compounds that are effective in
As an example, a case where calcium chloride is added will be explained. Calcium chloride is an inexpensive water-soluble calcium, and various types of hydrated calcium silicate produced by the reaction of calcium chloride with sodium silicate are insoluble in water and contribute to reducing gel time. Specifically, 240 kg of Portland cement was used as the hydraulic cement that is the basic composition, and clay sand from Okayama Prefecture (loam consisting of quartz, silkworm, montmorillonite, etc.) was used as the clay mineral constitutional material; composition [wt%] SiO ₂ 73.85, Al. ₂ O ₃ 18.23, Fe ₂ O ₃ 0.98,
CaO0.38, K ₂ O2.50, Na ₂ O0.21, others 0.79,
Igloss3.01; Sieving test [Residual rate weight %]
55 to 0.088mm, 48 to 0.15mm, 30 to 0.30mm,
8 up to 0.60mm, 0 up to 1.20mm) 240Kg, foaming sustaining agent (including polyoxyethylene alkyl ether, sodium lignin sulfonate, sodium resinate, etc.) 2.0Kg, water 326 mixed (volume approx. 1m) ³ ), various calcium compounds and others are added to it, and a backfilling material made by adding and mixing 100% of a sodium silicate-based aqueous solution (specific gravity 1.39, so-called water glass) to a bubble mortar in which air is mixed. Table 1 shows the results of examining the gel time and strength of this product at 15°C. 1st
As is clear from the experimental results shown in the table, the gel time becomes zero by adding calcium chloride, but the strength of the filler does not decrease. In addition, hydroxycarboxylic acids represented by citric acid are used as hardening retardants in cellular mortar as is well known, but when they come into contact with aqueous sodium silicate solutions, they have been observed to also act as gelation accelerators. Ru. Next, Table 2 shows an example of the results of examining the gel time at various temperatures mainly with calcium chloride added as a plasticity enhancer. From this experiment shown in Table 2, it is clear that increasing the amount of calcium chloride added reduces the gel time, and it can be seen that by adding about 3 kg, the gel time can be reduced to zero even in an atmosphere of 1°C. In addition, to demonstrate the curing retarding effect of citric acid,
Flow value at 25°C of cellular mortar with the above basic composition (a metal cylinder with a height of 8 cm and an inner diameter of 8 cm was placed in the center of a 30 cm square plastic plate and filled with a sample,
Table 3 shows an example of the results of measuring the average value [cm] of vertical and horizontal spread one minute and three minutes after being gently lifted up. From the results of this experiment shown in Table 3, it can be seen that by adding 0.3 kg of citric acid, the curing of the foamed mortar itself started after approximately 2 hours of stretching. Furthermore, the addition of condensed phosphates (eg sodium triphosphate) to the cellular mortar increases the setting retardation effect and reduces corrosivity. In the present invention, clay sand is a mixture of clay and sand (clay content: 20 to 80% by weight, sand content: 80 to 20% by weight), and includes silt, loam, and sandy loam, and is a bentonite-based mixture. is preferable because it easily swells with water, but it is not limited to this. Furthermore, hydroxycarboxylic acids include hardening retardants having hydroxyl groups and carboxyl groups, such as citric acid, tartaric acid, and lactic acid. The blowing agent referred to here refers to the so-called AE agent (Air entraining reagent), which includes sodium lignin sulfonate, sodium resinate, alkylaryl sulfonate amine salt, polyoxyethylene alkyl ether, etc. refers to a substance that has the property of forming small air bubbles to increase fluidity and workability. Moreover, Portland cement and the like are suitable as the cement used in the present invention. The typical composition of the backfilling material of the present invention is as follows: 240 kg of Portland cement, 240 kg of clay sand produced in Okayama Prefecture used in the above experiment, 2.4 kg of blowing agent,
The main ingredient is a foam mortar made with 3 kg of calcium chloride and 326 kg of water, and mixed with 100 kg of a sodium silicate aqueous solution with a specific gravity of approximately 1.39. Small amounts of substances can be added, such as condensed phosphoric acid. The foam mortar and the sodium silicate-based aqueous solution are usually prepared separately outside the tunnel, pumped separately to the point of use via a pipe, and mixed immediately before injection. As mentioned above, the backfilling material of the present invention is a highly deformable plastic material obtained by a hybrid combination of the filling material and the coagulant, so it has a sufficient pot life and solidifies, and after the completion of solidification, It develops sufficient strength, and until this point it has good workability, water-stopping properties, and volumetric stability, and it is possible to work with tail voids kept to a minimum, thereby reliably preventing problems such as ground subsidence. Additionally, it has excellent effects such as reducing the need for clogging of the pressure-feeding conduit and cleaning the conduit when work is stopped.

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[Table] Considered to be the limit of use.

Claims (1)

[Scope of Claims] 1. When filling the tail void that occurs at the rear of a shield excavator during shield construction, hydraulic cement, a clay mineral body material, and a foaming sustaining agent are mixed with water and a foaming gas is incorporated therein. A cellular mortar is prepared, and a backfilling material is prepared by containing a plasticity enhancer that causes rapid bonding when combined with a sodium silicate-based coagulant, and this backfilling material and the above coagulant are combined. and are respectively transported to the tail void site via pipes, and just before injection into the tail void, the backfilling material and coagulant are mixed to bond the two, forming a highly deformable viscous bonded plastic body and injecting it. A backfilling method for lining segments in the shield construction method, characterized in that the filler follows the shape of the tail void and rapidly solidifies to develop high support pressure and consolidation strength. 2. When filling the tail void that occurs at the rear of the shield excavator during shield construction, hydraulic cement, clay mineral body material, foaming sustaining agent, and setting retarder for hydraulic cement are mixed with water and a foaming gas is added. This is combined to form a bubble mortar,
A back-filling material is prepared by containing a plasticity enhancer that causes rapid bonding when combined with a sodium silicate-based coagulant. Immediately before injection into the tail void, the backfilling material and coagulant are mixed to bond the two, and the material is injected as a highly deformable viscous bonded plastic material. A backfilling method for lining segments in the shield construction method, characterized in that the material is filled following the shape of the tail void and rapidly solidified to develop high shoring pressure and consolidation strength. 3 Used to fill the tail void that occurs at the rear of the shield excavator during shield construction, (a)
clay sand, cement, foaming sustaining agent, chloride,
A foam mortar containing a calcium compound, water, and a foaming gas, and containing or not containing condensed phosphoric acid, hydroxycarboxylic acid, or a salt thereof, and (b) a sodium silicate-based aqueous solution are mixed immediately before filling. Back filling material in shield construction method.