JPH10102506A - Sliding resistance increasing method for caisson - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding resistance increasing method at the time of caisson installation capable of increasing the sliding resistance on a caisson installation plane at the time of an earthquake and preventing the slide of a caisson due to the earthquake. SOLUTION: When a riprap foundation 2 is installed, multiple key blocks 4 each having a lug-like stopper 3 at the front end section are adjacently installed so that their top ends serve as the installation plane of a caisson 1 to be installed along the longitudinal direction of the caisson 1 and a gap is formed between the front heel side of the caisson 1 and the stopper 3. Ripraps 6 are crammed between the key blocks 4, the caisson 1 is installed on them, then underwater concrete 5 is placed in the gap between the front heel side of the caisson 1 and the stopper 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for increasing the sliding resistance of a caisson to prevent the installed caisson from sliding on a rubble of an installation surface due to an earthquake or the like and to be displaced.

[0002]

2. Description of the Related Art In recent years, in a large-scale earthquake that occurred in Japan, a caisson, an underwater structure, slides on the abandoned stone surface of its installation surface, and not only shifts its position, but also collapses, causing it to recover. A great deal of time and money is required. As a cause of such sliding on the installation surface of the caisson, a gravity type structure such as a caisson resists the sliding by its own weight, but the upper limit is a value obtained by multiplying the bottom weight by the friction coefficient, The upper limit is the straight sliding of the rubble mound or the shear resistance value of the soil on the lower surface of the rubble mound. Generally, the sliding on the upper surface of the rubble mound is often an element that determines the shape of the gravity embankment.

[0003]

SUMMARY OF THE INVENTION According to the present invention, when a caisson is installed, a key block is interposed between the caisson and the rubble mound, so that the sliding resistance on the caisson installation surface during an earthquake can be increased. A method for increasing caisson sliding resistance.

[0004]

According to the present invention, there is provided a method for increasing sliding resistance when a caisson is installed. A key block having a T-shaped planar shape and a protruding stopper at a front end portion when a rubble foundation is laid. After installing a plurality of adjacent caisson so that the top end of the caisson is the installation surface of the caisson along the longitudinal direction of the caisson, and there is a gap between the fore toe side of the caisson and the stopper After installing the caisson on the leveled top of the key block with the rubble squeezed to the same level as the top end of the key block, install underwater concrete in the gap between the front toe side of the caisson and the key block stopper. Consists of

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a caisson according to an embodiment of the present invention, in which a caisson is installed by adopting the method of increasing sliding resistance according to the present invention. FIG. 2 is a plan view of a main part of the caisson shown in FIG. 1 indicated by broken lines.

First, as shown in FIG. 1, when the caisson 1 is laid on the rubble foundation 2 before installation, the caisson 1 has a T-shaped plane shape as shown in FIG. 2 and a projection at the front end portion as shown in FIG. The key block 4 having the stopper 3 is provided with a gap D between the front toe side of the caisson 1 and the stopper 3 so that the top end thereof is the mounting surface of the caisson 1 along the longitudinal direction of the caisson 1 to be installed. As shown in FIG. 2, a plurality of caisson 1 are installed adjacent to each other.

Next, as shown in FIG. 1, the caisson 1 is installed on the upper surface of each of the key blocks 4 on which the rubble 6 is packed to the same level as the top end of the key blocks 4 and is evenly leveled. After the caisson 1 is installed, the underwater concrete 5 is poured into the gap D between the front toe side of the caisson 1 and the stopper 3 of the key block 4.

As described above, according to the method of the present invention, when the caisson 1 is installed, the key block 4 is installed so that the top end thereof is the installation surface of the caisson 1, and the rubble 6 is packed between the key blocks 4. Since the caisson 1 is installed on the upper surface, the installation of the caisson 1 is facilitated, and the accuracy of the installation can be increased. Also, a gap D between the front toe side of the caisson 1 and the stopper 3 of the key block 4
The underwater concrete 5 is cast in the caisson 1
Sliding between the rubble foundation 2 and the rubble foundation 2 can be easily prevented by the key block 4 and its stopper 3.

In this case, the sliding resistance of the key block 4 depends on the received earth pressure on the front surface of the key block 4, and this received earth pressure is equal to the height H of the projecting stopper 3 at the front end of the key block 4. It will be determined by the front wall. Here, earth pressure intensity p = K _p γH and pressure (passive resistance) P = pH ²
/ 2, the internal friction angle of the abandoned stone was 40 degrees, the seismic intensity Kh = 0.2, and the height H of the front wall of the stopper was H =
Assuming _{1.5m, K p = 7.41 p =} 7.41 × 1.0 × 1.5 = 11.12tf / m 2 P = 11.12 × 1.5 × 1.5 / 2 = 12 .51tf
/ M and the sliding resistance due to the passive earth pressure on the front surface of the key block 4 is arguably greater than the sliding resistance due to only the bottom friction of the caisson 1.

[0010]

If the caisson is installed by the above-described sliding resistance increasing method of the present invention, a relatively simple operation procedure of interposing a key block between the caisson and the rubble mound at the time of caisson installation is added, The caisson's sliding resistance can be easily increased.

Since the sliding resistance of the caisson can be increased as described above, the sliding resistance due to the earthquake is increased as compared with the caisson installed by the conventional method, and the sliding of the caisson due to the earthquake can be prevented.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a main part of an embodiment in which a caisson is installed by adopting the sliding resistance increasing method of the present invention.

FIG. 2 is a plan view of a principal part of the caisson shown in FIG.

[Explanation of symbols]

 1 caisson 2 rubble foundation 3 stopper 4 key block 5 underwater concrete 6 rubble D gap

Claims (1)

[Claims] At the time of laying a rubble foundation, a key block having a T-shaped planar shape and having a protruding stopper at the front end is installed along the longitudinal direction of a caisson to be installed. After installing two or more adjacent so that there is a gap between the fore toe side of the caisson and the above stopper so that it becomes a mounting surface, rubble between each key block to the same level as the top end of the key block A method of increasing the sliding resistance of a caisson in which a caisson is installed on the stuffed level surface and then underwater concrete is poured into the gap between the caisson's fore toe and the key block stopper.