JPH0432172B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an underground continuous structure made of precast concrete that is used as an underground wall of a permanent structure, for example, when constructing a permanent structure that continues underground. The present invention relates to a wall construction method and a continuous wall unit element.

[Conventional technology] In the conventional method of constructing an underground continuous wall made of precast concrete, the ground corresponding to the underground continuous wall to be constructed is excavated by an excavator to a predetermined width and width while maintaining the stability of the excavated trench wall with a muddy water stabilizer. A common method is to form a deep groove with an extension and length, and then sequentially insert concrete panels into the deep groove to construct a continuous wall.

[Problem that the invention seeks to solve]

The biggest feature of the conventional underground continuous wall construction method is the use of muddy water (bentonite) stabilizing liquid (muddy water method). It requires measures to prevent water pollution and disposal as industrial waste, which drives up construction costs. In addition, continuous walls made of concrete panels are constructed by constructing each wall element by element, making it impossible to connect horizontal reinforcing bars. Various joint methods have been attempted, but continuous monolithic structures are not possible. We have not yet come up with a fundamental solution for establishing it as a physical object. Furthermore, since the cross section of the concrete panel has a structurally small section modulus, it is unsuitable for a deep underground continuous wall.

As a method to solve these problems, a method of constructing an underground continuous wall using box-shaped elements made of precast concrete has been developed, instead of using the muddy water construction method. The structure of the unit element is to form a continuous box shape with an open top and bottom, and to have a through hole for connecting the unit elements with each other using prestressing steel, etc., and the ground corresponds to the position where the unit element is sunk. After substituting the ground with easy-to-sink soil such as loose sand, the unit elements are successively deposited using prestressed steel materials, etc. to construct the specified element, and the internal space of the element is used as a work space. The desired precast continuous wall is constructed by horizontally tightening these together using prestressed steel or the like.

However, when constructing a deep underground continuous wall, the replacement method, which does not involve muddy water construction, does not cause problems such as water pollution, but because the replacement work is large-scale, it does not necessarily result in a significant reduction in construction costs compared to the muddy water construction method. Must not be. In addition, when horizontally tightening an element, it is necessary to keep the inside of the element dry, but in ground where the groundwater level is high, it is difficult to stop the water because it is replaced with sand. In addition, since the horizontal connections between the elements are made of horizontal reinforcement using prestressed steel, etc., construction accuracy is extremely difficult.

As mentioned above, the conventional construction methods described above are not necessarily satisfactory in the sense of reducing construction costs and increasing construction efficiency by using precast concrete walls instead of using the muddy water method for constructing deep underground continuous walls. Not yet.

[Means for solving problems]

In the present invention, in a method of constructing a target underground continuous wall underground by sequentially sinking and joining unit elements made of precast concrete, a continuous vertical pipe for draining mud is provided at a symmetrical position of the unit elements, The ground on which the unit element is to be deposited is changed into fluidized mud in advance. Furthermore, in order to reduce construction costs, the scale of modification is to create a wall-shaped fluidized mud with a width commensurate with the thickness of the wall member of the unit element and up to a predetermined depth. The work of sinking the unit element involves draining the fluidized mud from underground, which is pushed away by the wall members, through the vertical pipe and discharging it to the ground using the suction pump. The verticality of the unit element is maintained by adjusting the amount of silted soil discharged, and the unit element is sunk to a predetermined depth.

The method for modifying the ground in which the unit element is to be sunk is to first loosen the soil to a predetermined width and depth using an earth auger, etc., and discharge some of the earth and sand to the surface, and add an appropriate amount of admixtures (foaming agents, foaming agents, etc.).
By pumping air and cement slurry or lime slurry added to (retardant, etc.) and forcibly mixing this with underground earth and sand, a highly fluid cement system containing countless small independent air bubbles is created. Or use lime-based mixed mud. In this case, the degree of fluidity of the mixed mud is preferably such that the unit element is sunk at a rate that allows the fluidized mud in the ground that is pushed away by the wall member of the unit element to be discharged to the ground.

In the unit element used in the present invention, it is preferable that a removable covering sheet is attached to the wall surface of the permanent structure on the side to be used as the underground surface to prevent the adhesion of mud.

The structure of the unit element for large depths according to the present invention is that its upper and lower surfaces are open, and its front and rear walls are extended to form an irregular box shape, and the side surfaces of the extended front and rear walls are shaped like vertically inserted joints. and fixed fixing plates for horizontal bonding to these inner surfaces,
Furthermore, it is desirable to have a structure in which vertical pipes for removing mud are buried at the intersections of the front and rear walls, side walls, and partition walls. Here, it is preferable that the small compartment formed surrounded by the front and rear walls and side walls of the two large-depth unit elements be dimensioned so that it can be used as a welding work space.

The method of integrating the structure of the unit element for large depths underground according to the present invention is the interior of a shaft space of a small compartment surrounded by the overhanging front and rear walls and side walls of two adjacent unit elements. The work space is secured by discharging the earth and sand, and the mutual misalignment of the fixing plates is measured in advance, and holes for bolts in the splicing plate are drilled accordingly, and bolts are joined horizontally using these holes. Furthermore, if necessary, using a dowel attachment plate or a bolt that also serves as a dowel, a reinforcing bar cage is inserted into the shaft space of the small compartment, and concrete is poured to form a pillar in the wall.

[Effect]

The auxiliary construction method for sinking unit elements in the present invention is a fluidized mud construction method in which the ground for sinking is changed in advance into fluidized mud in which the unit elements can be easily deposited. This is a cement slurry or lime slurry that is made by discharging some of the earth and sand from the ground while loosening it with an earth auger, and adding an appropriate amount of admixtures (foaming agents, retarders, etc.). Air is forced into the system and mixed with the earth and sand underground. In other words, the in-situ ground soil is fluidized mud, and unlike conventional construction methods, it does not discharge all the earth and sand from the deep trench while protecting the excavated trench walls. Therefore, the construction method is extremely simple. In addition, fluidized mud is a highly fluid cement-based or lime-based mixed soil that contains countless small independent air bubbles, so it has high fluidity even in gravel ground due to the bearing effect of the air bubbles. Water-stopping properties are also improved. Therefore, the applicable ground ranges from sand and gravel to clayey soil.
In addition, the ground strength develops over time, and its magnitude can be set freely. Moreover, the scale of conversion to fluidized mud is sufficient to create a wall with a width commensurate with the thickness of the wall member of the unit element and up to a predetermined depth, which requires significantly less construction work than the conventional mud method or replacement method. Costs can be reduced.

In addition, the work of sinking the unit element involves discharging the fluidized mud from underground, which is displaced by the wall members, to the ground through the vertical slurry pipe and using the suction pump. This is a system construction method that can reliably control the construction, such as adjusting the sedimentation speed and verticality, by adjusting the amount of mud discharged.

In addition, in order to improve the integrity of continuous walls at great depths, which is a particular problem in structures, we installed splicing plates with dowels for horizontally connecting unit elements, and inserted reinforcing bar cages in the middle of the shafts of small compartments. Concrete was poured to form pillars (vertical beams) in the wall. That is, the joints of the unit elements are reinforced in a composite manner and also by utilizing the internal space of the continuous wall. The structural analysis of the joints is clear and the construction is reliable, making it highly reliable and making it easy to design continuous walls as an integral structure.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Figures 1 and 2 show units made of precast concrete that are suitably used as the basic unit structure constituting the elements used in the continuous wall at great depths when constructing the continuous wall at great depth according to the present invention. This shows the structure of the element.

In these figures, the symbol A is a unit element. This unit element A is composed of a front wall 1a, an overhanging front wall 1b, a rear wall 2a, an overhanging rear wall 2b, a side wall 3, and a partition wall 4. It has two large compartments C in the shape of a double irregular box with its upper and lower surfaces open and its front wall 1a and rear wall 2a extended. The side surfaces of the front overhanging wall 1b and the rear overhanging wall 2b are shaped as joints to form a male joint 5a and a female joint 5b, respectively, and a fixing plate 6 for horizontal joining is fixed to the inner surfaces of these joints. There is. Further, a vertical pipe 7 for draining mud is buried at the intersection of the front wall 1a, the rear wall 2a, the side wall 3, and the partition wall 4. As shown in FIG. 2, a small compartment D is formed by two adjacent unit elements A. Here, the small compartment D is set to a size that can be used as a work space in which at least an operator can enter and perform the work described below. In the figure, reference numeral 8 indicates a splicing plate for horizontally joining the unit elements A to each other.

FIG. 3 shows a front view of the vertical bolt joint when the unit element A is submerged. This is buried at an appropriate position inside the upper and lower surfaces of each wall of the unit element A. In the figure, 9a is a vertical joint box;
9b indicates a joint bolt.

Next, an example of actually constructing an underground continuous wall using the above unit element A is shown in Figure 4 a.
This will be explained sequentially with reference to b, c, d, etc.

First, the submerged ground at the continuous wall construction location is loosened to a width commensurate with the thickness of the wall member of the unit element, using an earth auger, etc., to loosen some of the earth and sand, and at the same time, some of the earth and sand are discharged to the ground. Cement slurry or lime slurry with an appropriate amount of admixture added, such as an admixture, and air are pumped, and this is forcibly mixed with underground earth and sand to form a predetermined wall-shaped fluidized muddy ground as shown in Figure 4a. Create E. What is important here is to set the degree of fluidity of the fluid mud at a rate at which the underground mud that is pushed away by the wall members of the unit elements is discharged to the ground, and by setting the degree of fluidity to such a level that the unit elements are submerged. The purpose of this project is to determine the slurry composition and pumping amount of slurry and air based on the depth of burial, etc., and to manage construction work. The fluidized muddy ground E in the figure indicates a portion corresponding to the front wall 1a and rear wall 2a of the unit element A, or the overhanging front wall 1b and overhanging rear wall 2b. Further, in the figure, the reference numeral F indicates the conventional ground, and the reference numeral 11 indicates the concrete foundation of a mobile bridge-type crane for work, for example.

After creating the fluidized muddy ground E in this way, place the cutting edge element B at the beginning, stack several unit elements A on top of it, and bolt the vertical joint shown in the third section to form the unit. Form K. Next, as shown in FIG. 2B, this is suspended and fixed using, for example, a mobile bridge type crane 10 and installed at a predetermined position. Next, the hose of the suction pump 12 is connected to the vertical pipe 7 of Unit K, the suspension fixation of the bridge type crane 10 of Unit K is released, and the sinking is started by its own weight, and the ground that is pushed away by the wall members of Unit K is removed. The fluidized mud inside is discharged to the ground by a suction pump 12 through a vertical pipe 7, and is then deposited. Figure 4c shows the state of submersion of unit K. What is important here is that the amount of fluidized mud discharged through each vertical pipe 7 is adjusted by the suction pump 12,
The aim is to maintain the verticality of unit K while sinking it.

After placing unit K as shown in Figure 4c,
The unit element A is stacked on top of the unit element A in succession, and the above-described sinking method is repeated until the unit element A is sunk to a predetermined depth as shown in FIG.

After completing the submersion work for the first vertical row in this manner, the submergence work for the second and subsequent vertical rows to be successively connected in the horizontal direction is carried out using the same method. At this time, as shown in FIG. 2, the vertical insertion joint of the unit element A and the male joint 5b are engaged to interconnect them in the lateral direction. After completing the installation of the unit elements A in the number corresponding to the underground continuous wall of the desired depth and length as described above, the earth and sand in the shaft space of the small compartment D at the connection part of each element is discharged. , secure the work space and install the fixing plate 6 in advance.
Measure the mutual misalignment between the
Drill holes for the bolts and use them to make horizontal bolt connections. Furthermore, if necessary, use the attachment plate 13 with a dowel to attach the reinforcing bar cage 1 to the shaft space of the small compartment D.
4 is inserted, and filling concrete 15 is poured to form a vertical center column. Figure 5 shows a horizontal sectional view of a cast-in-place reinforced concrete wall column. Also, vertical connections are made using vertical pipe 7.
A steel material 16 is inserted inside, the element body is vertically tightened, and the filling concrete 15 is filled.

The underground continuous wall constructed as described above has each unit element A that is a unit structure composing it.
It has an integrated structure in which the horizontal direction is bolted to the splicing plate, and the vertical direction is tightened using prestressed steel. Furthermore, if necessary, it is also possible to easily strengthen the integrity of horizontal joints, which tend to be weak points in precast continuous walls, by using cast-in-place reinforced concrete at the joints and using them as pillars in the wall.

Note that the present invention is not limited to the above embodiments. For example, in the embodiment, six examples are shown of only the vertical connection of the unit elements A on land, but the present invention is not limited to this. You may also use This is because the dimensions of unit element A are limited due to transportation issues, and in submersion work, the size of unit K can be determined based on the capacity of the working machine such as the mobile bridge crane 10. . Alternatively, the wall surface of the unit element A may be curved to form a unit structure of a circular cell structure, and the continuous walls may be closed in a circle. In addition, covering sheets to prevent mud from adhering to the walls of unit elements may be pasted.

〔Effect of the invention〕

As described in detail above, according to the present invention, the unit elements according to the present invention are constructed by constructing a target underground continuous wall by sequentially sinking unit elements made of precast concrete into the ground and joining them to each other. The submergence submergence method uses fluidized mud as the in-situ ground soil. Therefore, unlike conventional methods, this method does not discharge all the earth and sand from deep trenches while protecting the excavated structure. For this reason, the construction method is extremely simple and construction costs are low. Further, the fluidized mud of the present invention is a cement-based or lime-based mixed soil containing numerous independent microscopic air bubbles. Therefore, even in sandy and gravelly ground, the fluidity is very high due to the bearing effect of air bubbles, so it can be applied to a wide range of ground, from sandy and gravelly to cohesive soil. The water-stopping properties are high, and the effective time and strength of the mixed ground can be freely set. Moreover, since the scale of conversion to fluidized mud is sufficient to correspond to the thickness of the wall member of the unit element, the construction cost can be reduced significantly compared to the conventional mud construction method and replacement construction method.

In addition, the unit element sinking work of the present invention is a system that can reliably control construction, such as adjusting the sinking speed and verticality, by adjusting the amount of fluidized mud underground discharged from each earth removal pipe. Since it has become a construction method, its construction accuracy has improved dramatically.

Regarding the integrity of the continuous wall according to the present invention,
For horizontal joints, which tend to be weak points in precast continuous walls, we have made it easy to strengthen the joint joints in a complex manner by using bolts of splicing plates and cast-in-place reinforced concrete as pillars (or longitudinal beams) in the wall. . In conjunction with the submerged system construction method, various connections of underground continuous walls, such as even angles, T
The reliability is high because the connections to ensure structural integrity, such as cross-shaped and cross connections, are reliable, and the highly effective use of underground space is dramatically increased, producing excellent effects that have never existed before.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is a perspective view of a unit element, Fig. 2 is a plan view showing how the elements are connected to each other, Fig. 3 is a front view of a vertical bolt joint, and Fig. 4 is a front view of a vertical bolt joint. Figures a, b, c, and d are side sectional views showing the element sinking process, respectively, and Figure 5 is a horizontal sectional view of a column in a cast-in-place reinforced concrete wall. A...Unit element, B...Blade edge element, D...Small compartment, E...Fluidized muddy ground, 1a
...Front wall of unit element, 1b... Same overhang front wall, 2a... Same rear wall, 2b... Same overhang rear wall, 3
... Same side wall, 7 ... Vertical pipe, 8 ... Connection plate.

Claims (1)

[Claims] 1. In a method for constructing an intended underground continuous wall underground by sequentially depositing and joining unit elements made of precast concrete, a continuous sludge drainage wall is installed at a symmetrical position of the unit elements. A vertical pipe is installed, and then the ground in which the unit element is to be sunk is changed into fluidized mud to a predetermined depth with a width commensurate with the wall member thickness, and this is achieved through the work of sinking the unit element. The fluidized mud in the ground that is pushed away by the wall members is discharged to the ground through the vertical pipes by a suction pump, and at this time, the amount of fluidized mud discharged from each vertical pipe for suction is adjusted. 1. A method for constructing a precast underground continuous wall, comprising the step of sinking the unit element to a predetermined depth while maintaining the verticality of the unit element. 2 Cement slurry or lime slurry, which is made by loosening the ground in which the unit element is to be sunk to a predetermined width and depth using an earth auger, etc., and discharging some of the earth and sand to the ground, and adding an appropriate amount of admixture. A patent claim characterized in that by pumping air and forcibly mixing it with earth and sand underground, a highly fluid cement-based or lime-based mixed mud containing numerous independent microscopic air bubbles is created. A method for constructing a precast continuous wall according to item 1. 3. The precast according to claim 1, characterized in that a removable covering sheet is pasted on the wall surface of the unit element on the side used as the underground surface of the permanent structure to prevent the adhesion of mud. How to construct underground continuous walls. 4. The method for constructing a precast underground continuous wall according to claim 1, characterized in that the wall surface of the unit element is curved to form a unit structure of a circular cell structure, and the continuous wall is closed in a circle. 5 In a unit element for constructing a precast underground continuous wall by joining the upper and lower sides and the left and right sides, the upper and lower surfaces thereof are opened, and the front and rear walls are extended to form an irregular box shape, and the front and rear walls of the overhang are The sides are shaped like vertically inserted joints, fixing plates for horizontal connection are fixed to the inner surfaces of these, and vertical pipes for mud removal are buried at the intersections of the front and rear walls, side walls, and partition walls. Furthermore, the dimensions of the small compartment formed by being surrounded by the rear wall and side wall of the two adjacent unit elements are set such that it can be used as a work space for joining these unit elements. A unit element for precast underground continuous walls featuring: