JPH1161862A - Method of excavating pump-up vertical shaft in cut-off wall of underground tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excavate a pump-up vertical shaft continuous to a continuous underground wall without using an additional excavating device. SOLUTION: An excavating machine 10 for forming a continuous underground wall serving as the cut-off wall of an underground tank, is attached with a predetermined excavating guide 20, and is then positioned by means of a guide frame so as to be projected from the outer wall surface of a groove 3 in the underground wall. A pump-up vertical shaft 4 having a rectangular cross-sectional shape is formed, being projected from the outer walk surface of the groove 3 in the wall by the excavating machine which is guided by the excavating guide 20 along the wall surface of the groove previously formed in the continuous underground wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for digging a pumping shaft of an underground tank water stop wall, and more particularly to a method of digging a pumping shaft installed protruding from a continuous underground wall serving as an underground tank water stop wall.

[0002]

2. Description of the Related Art When constructing a large liquefied natural gas (LNG) underground tank or the like, a continuous deep underground wall is constructed around the main body as a retaining wall, and ground excavation is carried out along the inner periphery thereof. The construction method of constructing the skeleton concrete so that it is integrated with the continuous underground wall has been adopted. In addition, the continuous underground wall often functions as a water stop wall at the time of main construction. In this case, a pumping shaft is provided outside the continuous underground wall to reduce the water pressure acting on the wall, and a vertical shaft is provided. A pumping facility of a predetermined capacity is arranged inside.

FIG. 5 shows a water stop wall 51 formed of a continuous underground wall provided in an underground tank 50 of this type, and a plurality of pumping shafts (pump pits) 5 attached to the water stop wall 51.
FIG. 2 is a schematic plan view showing a second example. As shown in the figure, in this example, four pumping shafts 52 are provided along the outer peripheral surface of a polygonal water blocking wall 51 to which a plurality of elements 51a are connected. These pumping shafts 52 are often excavated using a reverse circulation drill (hereinafter referred to as RCD) in parallel with the excavation of the continuous underground wall (water stop wall 51).

[0004]

However, when the pumping shaft 52 is excavated by the RCD along the continuous underground wall, the continuous underground wall must be removed in order to prevent the working range of both operations from being complicated. The excavator for construction must be stopped. In addition, an RCD must be deployed and excavated only to excavate the pumping shafts 52 at a plurality of locations around the water stop wall 51, and the cost increases in terms of temporary facilities. Further, a ground improvement body may be installed in advance in order to prevent collapse of the element groove wall. In such a state, a part of the solidified ground improvement body must be excavated by RCD. The solidified ground improvement body cannot be drilled sufficiently with an RCD drill bit, resulting in reduced work efficiency and excavation accuracy. In addition, in the case of the RCD, since the rotary excavation is performed by the cylindrical keriba, the excavation cross section is circular. When this circular pumping shaft 52 is excavated so as to circumscribe the groove wall of the element 51a, an undigged portion 53 occurs between the circular shaft portion 52 and the groove wall of the element 51a as shown in FIG. . Therefore, it is necessary to further excavate the unexcavated portion 53 while the groove wall is expected to collapse, which is problematic in terms of process and safety.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional technology,
An object of the present invention is to provide a method for excavating a pumping shaft of an underground tank cutoff wall, which does not require additional equipment and excavates a pumping shaft.

[0006]

In order to achieve the above-mentioned object, the present invention attaches a predetermined excavation guide to an excavator for excavating a continuous underground wall serving as an underground tank water blocking wall, and attaches the excavator to the excavator. Pumping of a rectangular excavated cross section projected from the trench outer wall surface of the continuous underground wall by the excavator while being positioned so as to protrude from the trench outer wall surface of the continuous underground wall, and guiding the excavated trench wall surface by the excavation guide The shaft is excavated.

At this time, the positioning of the excavator is preferably performed along a guide frame provided on a guide wall of the continuous underground wall.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for digging a pumping shaft for an underground tank water stop wall according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an excavator 10 (a schematic shape is shown by a virtual line) used in the excavation method of a pumping shaft according to the present invention, and an excavation guide 20 (20A, 20B: hereinafter, both of which are attached around the excavator 10). In the case where the description is made without distinction, reference numeral 20 is attached.) As shown in FIGS. 1 and 2, in the present embodiment, a known horizontal biaxial reverse circulation drill type excavator 10 such as an electromill is used. At the lower end of the frame 11 of the excavator 10 suspended from the suspension device 1 (see FIG. 2A), two drum cutters 1 supported by two parallel horizontal rotating shafts are provided.
2, 12 are attached. The horizontal two-axis drum cutter 12 and a vertical axis auxiliary bit (not shown) are driven to rotate by a submersible motor, so that a predetermined rectangular excavation cross section is obtained. This rectangular excavation part 2
One element of the continuous underground wall is completed by excavating a plurality of guts as guts (units of excavation). Excavated earth and sand is efficiently discharged to the ground by reverse circulation. In the present embodiment, a crawler crane shown in FIG. 2 is employed as the suspension device 1 for the excavator 10.

The excavation guide 2 shown in FIGS. 1 and 2
As long as the excavator to which 0 can be attached is used, a known excavator for a continuous underground wall, such as a BW, a keriba system, and a bucket system, can be used without being limited to the specification such as the electromill.

FIGS. 1 and 2 show the structure of the excavation guide 20.
This will be described with reference to FIG. The excavator 10 used in the present embodiment is configured to be suspended in the groove 3 by the suspension equipment 1. For this reason, if there is an already excavated space around the gut to be excavated, the excavator may escape to the already excavated space side. Drilling guides are used to prevent this. Excavation guides 20 shown in FIGS. 1 and 2 are provided on the side surfaces of the lower end 11 a and the upper end 11 b of the excavator frame 11.
A and 20B are respectively fixed. Each of the excavation guides 20 includes a contact plate 21 that is substantially equal to the vertical and horizontal widths of the excavator frame 11, and a supporting steel material 22 that supports the contact plate 21 on the excavator body frame 11. The upper and lower ends of the contact plate 21 are bent in a sled shape so that the excavator frame 11 can smoothly contact the groove wall surface when the excavator 10 moves up and down. In this embodiment, the supporting steel member 22 includes a stiffening member such as a channel steel for stiffening the contact plate 21 from the back side, and the excavator frame 1.
1 and a supporting member that supports the contact plate 21. As shown in FIG. 3, if the excavation guide 20 is formed in a box shape, it can be a mounting member having high rigidity and relatively easy to mount.

A procedure for excavating the pumping shaft 4 so as to circumscribe the continuous underground wall using the excavator 10 to which the excavation guide 20 is attached will be described with reference to FIGS.
FIG. 4A shows a pumping shaft 4 having a substantially T shape in plan view.
The planned excavation position of (width B0 x depth D0) and this pumping shaft 4
2 shows a trailing element 5 connected to the continuous underground wall and a preceding element 6 installed on both sides thereof. In addition,
Each figure in Fig. 4 shows one excavation unit (gut: B
× D), a code G indicating the order of excavation of the gut, and a suffix numeral.

First, as shown in FIG. 4A, excavation of a gut (G1) substantially at the center of an approximately T-shaped excavation area sandwiched between preceding elements 6A and 6B is performed. In the present embodiment, as shown in the figure, the excavator 10 has a gut excavation width B equal to the thickness of the continuous underground wall, and excavates 3 gut in the longitudinal direction to complete excavation of one element. I do. Subsequently, the second gut (G2) is excavated so as to remove the ground portion 7 remaining between the first gut (G1) and the joint space portion of the preceding element 6A. Subsequently, excavation of the ground portion 7 between G2 and the joint space portion with the preceding element 6B on the opposite side is performed (G3). Thus, excavation of the following element 5 is completed.

At this stage, the direction of the suspended excavator 10 is changed by 90 °. Next, as shown in FIG. 4D, the lower end of the excavator 10 is set on a guide frame 25 serving as a cut-off guide previously mounted on a guide wall (not shown). This guide frame 25 has a large H
This is a temporary material in which the section steels are stacked in a cross-girder shape with a predetermined clearance with respect to the outer dimensions (B × D) of the excavator 10. The lower end of the excavator 10 is inserted so as to be hung in a substantially square-shaped portion of the guide frame 25, and is used as a guide for starting excavation, and excavation of gut (G4) is performed. Since the width B of the excavator is smaller than the width B0 of the pumping shaft 4, it is necessary to widen the gut (G4) to the width B0 of the pumping shaft 4. Therefore, FIG.
As shown in (e), in the shape shown in FIG.
(= B0−B) excavation guide 20A and thickness Δ2 (= B + D)
0-D) with the excavator frame 11
Wide excavation. Excavation guide 2 shows that the excavator inclines to the gut (G4) and the continuous underground wall side
Since 0 is blocked, the groove wall side of the gut (G5) is reliably excavated. Thereby, the pumping shaft 4 having a rectangular cross section of the width B0 and the depth D0 shown in FIG.

In the above description, an example was shown in which the trailing element 5 and the pumping shaft 4 were excavated while being divided into 5 guts. However, the wall thickness of the continuous underground wall (B) and the width of the pumping shaft 4 (B0) Depending on the size of the excavation guide or the like, a plurality of excavation guides having different thicknesses may be appropriately changed to correspond to a predetermined excavation cross section.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view schematically showing an embodiment of an excavation guide used in an excavation method of a pumping shaft of an underground tank water stop wall according to the present invention.

FIG. 2 is a front view and a partial side view showing an embodiment of a configuration of an excavator to which an excavation guide is attached.

FIG. 3 is a partial perspective view showing a modification of the excavation guide shown in FIG.

FIG. 4 is a construction sequence diagram schematically showing a procedure for excavating a pumping shaft using an excavation guide.

FIG. 5 is a schematic plan view showing an example of arrangement of a pumping shaft provided on a water stop wall of an underground tank using a conventional continuous underground wall.

FIG. 6 is a partially enlarged plan view showing details of a pumping shaft shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suspension device 4 Pumping shaft 5 Trailing element 6 Leading element 10 Excavator 11 Excavator frame 20 (20A, 20B) Excavation guide 25 Guide frame Gi i-th gut (drilling unit)

Claims (2)

[Claims] 1. A predetermined excavation guide is attached to an excavator for excavating a continuous underground wall serving as an underground tank water stopping wall, and the excavator is positioned so as to protrude from a groove outer wall surface of the continuous underground wall. An underground tank stopping water, wherein the excavator excavates a pumping shaft having a rectangular excavation cross section protruding from the outer wall surface of the continuous underground wall while guiding the excavation wall surface by the excavation guide. How to excavate the pumping shaft on the wall. 2. The underground tank water stop wall according to claim 1, wherein the positioning of the excavator is performed along a guide frame provided on a guide wall of the continuous underground wall. Excavation method of pumping shaft.