JP2914608B2 - Shield method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an improvement in a shield construction method which ensures the viscosity of a muddy material fed into a shield machine at the time of excavation in a shield construction and at the same time makes it easy to solidify wastewater after excavation. About.

[0002]

2. Description of the Related Art For example, a muddy material (also called mud) which is injected into a face (specifically, a space between a cutter head and a partition wall) at the time of excavation in a mud pressure shield method, is referred to as a mud material in this specification. In this method, specific gravity, concentration, viscosity, etc. are adjusted by appropriately mixing water and a modifier with powdered clay or bentonite.

[0003] Various types of adjusting agents are known, and an appropriate one is selected according to the excavated ground and the clay mineral to be used. However, when necessary, a suitable viscosity is imparted without impairing the fluidity of the material. What can be used is used. A typical example is carboxymethylcellulose (CMC).

On the other hand, excavated soil (water and spring water) generated by the excavation is stirred and mixed with the mud material by a cutter of a shield machine or an agitator for earth removal in the space in the above-mentioned partition wall, so that the excavated soil becomes fluid. It is transported as raised sludge outside the mine. In the large-diameter shield method, it is normal to carry the sludge on a slip-cart, and then to carry it out, but a method of feeding it with a hydraulically driven piston pump is also adopted. In the small- and medium-diameter shield construction method, a small hydraulic piston pump or bakyum pump is used to carry out.

[0005] In order to dispose of this sludge in a state in which it can be transported and to dispose of it in landfills or the like, a solidification treatment for concentrating the mud is required. In this solidification treatment, a cement-based or lime-based solidifying agent is used. A method of single or compound blending, a method of adding a flocculant to perform solid-liquid separation, a method of using a flocculant and a solidifying agent in combination, and the like have been performed.

[0006]

The properties that must be provided by a mud material may not be desirable for mud drainage. For example, if viscosity is given to the muddy material so as not to cause material separation even at high specific gravity and to maintain appropriate fluidity,
When the sludge is to be separated into solid and liquid, it does not act in a preferable direction. Conventional mud conditioning agents are based on the principle of imparting advantageous properties to the mud material injected into the face, and those that can impart advantageous properties to the sludge treatment such as solid-liquid separation. Was not. On the one hand, a regulator which does not cause solid-liquid separation and on the other hand makes it easy to cause solid-liquid separation was considered to be essentially non-existent due to its reaction.

For this reason, when solidifying sludge, a cement-type or lime-type solidifying agent or a coagulant is separately used. However, when a cement-type or lime-type solidifying agent is used, the solidified earth mass is Since it exhibits alkalinity, leachate becomes alkaline when landfilled, and there is a problem that it greatly affects the surrounding environment such as groundwater.

[0008] Even when an alkaline soil block is neutralized with an acidic substance, it is difficult to control the amount of the acidic substance to be added.

Even in the method of promoting coagulation using a coagulant, the conventional coagulant has a small coagulation effect and cannot be coagulated economically and advantageously. It was difficult to solidify efficiently.

[0010] The present invention aims to solve the problem of such a shield method.

[0011]

SUMMARY OF THE INVENTION According to the present invention, sodium alginate and a reaction retarder are blended into a mud material fed into a shield machine at the time of excavation, and the alginate contained in the material is added to the sludge mixed with the mud material and excavated soil. It is characterized in that a sufficient amount of a polyvalent metal salt is added so that sodium can be crosslinked and gelled.

[0012]

When sodium alginate is dissolved in a clay material mixed with powdered clay or bentonite, it has an effect of imparting an appropriate viscosity and suspending and dispersing fine mud.
For this reason, the fluidity of the mud material is also improved.

Therefore, it can be advantageously used as a mud material for the shield method. In this case, the effect of sodium alginate itself does not change so much even when used in combination with other conventional modifiers.

When sodium alginate is added to a mud material, if metal ions are present in the mud material, sodium alginate causes a crosslinking reaction via the metal ions to promote gelation. To suppress this reaction,
In the present invention, the reaction retardant is preliminarily mixed with sodium alginate and then added to the pulverized material.

At this time, if the reaction retardant is previously mixed with sodium alginate, it has the effect of preventing the sodium alginate from hardening into mamaco,
The dispersibility of sodium alginate in turbid water can be improved.

Examples of the reaction retardant that can be used include various phosphates such as sodium tripolyphosphate, sodium dibasic phosphate, sodium tertiary phosphate, sodium pyrophosphate, sodium hexametaphosphate and the like, or various carbonates such as sodium carbonate , Sodium bicarbonate, potassium bicarbonate and the like, or various citrates such as sodium citrate, sodium hydrogen citrate, potassium citrate and ammonium citrate. These may be used alone or in combination.

When the sodium alginate and the reaction retarder are previously mixed and dissolved in a small amount of water to form a liquid mixture, the surroundings of the sodium alginate are protected by the reaction retarder when added to the muddy material. Crosslinking of sodium alginate by ions in water is effectively prevented, and dispersibility of sodium alginate in water is improved as described above.

On the other hand, when a shield construction is performed using a mud material containing this sodium alginate, sodium alginate remains in the sludge, but this sludge is sent to a pit or ground surface in the rear. When mud is added and polyvalent metal salt is added to the sludge in the sludge treatment zone, sodium alginate crosslinks (fiber) gels and takes in suspended particles in the sludge, rapidly granulating and flocculating. be able to.

The polyvalent metal salt is dissolved in water,
Any material capable of supplying a metal ion having a valence of two or more which participates in the crosslinking reaction of sodium alginate may be used, but calcium chloride is preferred because it is inexpensive and harmless. At that time, if the calcium chloride aqueous solution is added to the wastewater, the reaction proceeds more efficiently. An appropriate concentration of the aqueous calcium chloride solution is about 5 to 20%.

As described above, the addition of the metal salt rapidly granulates and flocs the sludge in the sludge. When the sludge is sent to a screen-type separator using a coarse filter, the sludge is separated from the solids. It can be easily filtered off into water. The separated solids have been removed from water to such an extent that they can be transported by dumping, and can be directly used for landfill.

In addition, sodium alginate is harmless to living organisms as used as a food additive or as an emulsifier for medicines. Therefore, even if sodium alginate remains in the solid content, it does not affect the biological environment.

[0022]

[Formulation A]

Heavy clay: 400 kg The mixture: 45 kg Water: 864 kg The specific gravity, flow value and viscosity of the obtained mud material (mud) were measured. The results are shown in Table 1.

For comparison, the specific gravities, flow values and viscosities of conventionally used slurries of the following formulations B and C are also shown in Table 1. [Formulation B] Clay: 400 kg Bentonite: 80 kg Water: 820 kg [Formulation C] Clay: 470 kg CMC: 6.3 kg Water: 830 kg

[0024]

From Table 1, it can be seen that the muddy material of Formulation A according to the present invention is not inferior to the slurry of the conventional Formulations B and C, and has a better flow rate than the conventional product despite its high viscosity and specific gravity. It can be seen that it has the property.

The excavated soil of the gravel layer is mixed with the muddy material of the composition A according to the present invention at a mixing ratio of 1:10 by volume ratio.
4% by volume of a 40% aqueous solution of calcium chloride was added and mixed.

As a result, gelation occurred and mud flocked. When 50 kg of this was collected and supplied to a vibrating screen type separator, a mixed mud having a water content of 98% was separated into a solid content having a water content of 65% and 16.4 liters of surface separation water.

[0028]

As described above, according to the present invention,
In the shield method using a mud material, viscosity and fluidity can be provided so that sedimentation does not occur even with a mud material using a relatively high specific gravity clay. As it became easy to separate. For this reason, the shield work can be stably performed and the sludge treatment can be simplified.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C09K 103: 00 (72) Inventor Yasuhiro Yukawa 3-4-1 Kawaramachi, Chuo-ku, Osaka-shi, Osaka Yamahiro Corporation (56) References JP-A-5-339564 (JP, A) JP-A-3-269087 (JP, A) JP-A-5-98249 (JP, A) JP-A-3-232600 (JP, A) Kaihei 7-82559 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E21D 9/06 301 C09K 17/06 C09K 17/42 C09K 17/50 E21D 9/12

Claims (4)

(57) [Claims] In the shield method, sodium alginate and a reaction retarder are mixed with a mud material fed into a shield machine at the time of excavation, and sodium alginate in the material is added to a mud mixed with the mud material and excavated soil. A shielding method characterized by adding a polyvalent metal salt sufficient to form a crosslinked gel. 2. The shield method according to claim 1, wherein the reaction retardant is phosphate, carbonate or citrate. 3. The shielding method according to claim 1, wherein the polyvalent metal salt is calcium chloride. 4. The shielding method according to claim 1, wherein the mixture of sodium alginate and the reaction retarder is a liquid mixture which is previously mixed and dissolved with water.