JPH06240696A - Cement back-filler for retaining wall - Google Patents

Abstract

PURPOSE:To prevent a retaining wall from damage by providing the retaining wall for preventing the collapse of a filling slope, etc., and using low-heat cement and super-low-heat cement as back-filler. CONSTITUTION:A retaining wall 2 is approached to a filling or a cut slope 1 and is buried and fixed, and cement back-filler 3 is filled between the slope 1 and retaining wall 2. After that, at that time, low-heat cement and/or super- low-heat cement is used as the back-filler 3. According to the constitution, expansion pressure against the retaining wall can be reduced because of small heat generation rate in the case of hydration and, at the same time, cracks or damage of the retaining wall can be surely prevented, and durability can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement-based backfill material for a retaining wall, and particularly when applied as a backfill material for a retaining wall, the expansion pressure applied to the retaining wall due to heat of hydration is small and the retaining wall is small. The present invention relates to a cement-based backfill material for a retaining wall that does not cause cracking or damage to the wall.

[0002]

2. Description of the Related Art A retaining wall is constructed to prevent landslide of an embankment or a cut slope and maintain structural stability, and a cement system of mortar or concrete is provided between the retaining wall and the embankment or cut slope. The method of filling the backfill material has already been put to practical use.

Specifically, as shown in FIGS. 1 (a) to 1 (d), the retaining wall 2 (2a, 2) is provided close to the embankment or cut slope 1.
b, 2c, 2d) are embedded and fixed, and the cement-based backfilling material 3 is filled between the retaining wall 2 and the slope 1. In this retaining wall 2,
As illustrated, there are sheet pile type retaining wall 2a, L-shaped retaining wall 2b, inverted T type retaining wall 2c, inverted L type retaining wall 2d and the like.

Conventionally, as cement for cement-based backfill material, Portland cement (JIS R 5210)
Or mixed cement (JIS R 5211, 5212,
5213) and the like are used.

In some cases, a backfill material made of air mortar is used as the cement-based backfill material.
In this case, since the filling weight of the backfill material becomes light, there is an advantage that the lateral pressure received by the retaining wall at the time of placing the backfill material becomes small.

[0006] Usually, in such a construction method, the structural strength design of the retaining wall is performed mainly by the lateral pressure when the retaining wall is filled with the backfill material, the expansion pressure due to the hydration heat of the cement of the cement-based backfill material, and the like. It is decided to ensure safety that can sufficiently withstand these pressures or loads in consideration of loads due to subsequent traffic, slope reaction forces, and external forces due to disasters such as earthquakes.

[0007]

By the way, since the retaining wall described in the text has a relatively thin wall that is directly subjected to pressure, the pressure and load applied to this retaining wall can be applied. It is preferable to make it as small as possible.

On the other hand, the expansion pressure due to the heat of hydration during hardening after the cement-based backfilling material is placed is a value that cannot be ignored,
The displacement due to the expansion pressure is large, and the retaining wall may be cracked or, in a remarkable case, the retaining wall may be damaged.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a cement-based backfilling material which has a small expansion pressure due to heat of hydration of cement and does not give a large displacement to the retaining wall.

[0010]

The cement-based backfill material for a retaining wall of the present invention is characterized by using low heat cement and / or ultra low heat cement as cement.

The present invention will be described in detail below.

The cement-based backfill material of the present invention uses one or both of low heat cement and ultra low heat cement as cement.

Here, the low heat cement is a Portland cement which has been chemically changed so that the heat of hydration in the initial stage of hardening is 25 to 30% smaller than that of a normal one. Japanese heat is 40 ~
It is designed to be 45% smaller.

Specifically, as the low heat cement and the super low heat cement, the following can be used.

An increase in the amount of C ₂ S (2CaO · SiO ₂ ) which has a relatively low heat of hydration in the cement mineral composition. For example, the following composition. _{C 3 S (3CaO · SiO 2} ): 22 _{wt% C 2 S (2CaO · SiO} 2): 57 _{wt% C 3 A (3CaO · Al} 2 O 3): 4 _{wt% C 4 AF (4CaO · Al} 2 O ₃・ Fe ₂ O ₃ ): 11
Weight% Others that meet ASTM type IV standards.

A mixture of Portland cement specified in JIS R 5210 and slag and fly ash. For example, a mixture of Portland cement with slag and fly ash in the following formulation. Slag: 40 to 60% by weight based on the total of Portland cement, slag and fly ash Fly ash: 10 to 30% by weight based on the total of Portland cement, slag and fly ash The above low heat cement instead of the above Portland cement Or, using ultra low heat cement.

In the present invention, the fineness of the low-heat cement or the ultra-low-heat cement used is not particularly limited, but in general, it is preferable that the Blaine value is 3000 to 6000 cm ² / g.

The cement-based backfill material of the present invention using such low heat cement or ultra low heat cement can have the following compounding composition, for example.

Concrete backfill material Low heat cement and / or ultra low heat cement: 100 parts by weight Fine aggregate: 250 to 300 parts by weight Coarse aggregate: 350 to 400 parts by weight Mortar type backfill material Low heat cement and / or ultra low heat Cement: 100 parts by weight Fine aggregate: 250 to 350 parts by weight Air mortar type backfilling material Low heat cement and / or ultra low heat cement: 100 parts by weight Fine aggregate: 150 to 250 parts by weight Foaming agent: Bubble volume for mortar is 40 ~ 60
% Amount of AE agent, A
E A water reducing agent may be added.

When such a cement-based backfill material is used, a water / cement ratio of 0.4 to 0.4 is used in accordance with a conventional method.
It may be kneaded at about 0.75 and placed.

[0021]

Since the cement-based backfill material of the present invention uses low-heat cement or ultra-low-heat cement as the cement, it can suppress the amount of heat generated by hydration of the cement when it is filled as the backfill material for the retaining wall. it can. Therefore, the temperature rise of the backfill material is suppressed, and the expansion amount of the backfill material is significantly reduced. Therefore, the expansion pressure of the backfill material applied to the retaining wall is also extremely small, the amount of displacement of the retaining wall due to this expansion pressure is reduced, and cracking and damage of the retaining wall are prevented.

[0022]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Examples 1 and 2, Comparative Example 1 A precast cement-based sheet pile was used to produce a frame 4 shown in FIG. Blast furnace cement type B, ultra low heat cement (Portland cement: 20% by weight, slag 60% by weight,
20% by weight of fly ash and low heat cement (Portland cement: 40% by weight, slag: 40% by weight,
Fly ash: 20% by weight) was used to prepare an air mortar having the following composition, and it was placed in the frame 4 in FIG.

Cement containing air mortar backfill material : 100 parts by weight Fine aggregate: 200 parts by weight Water: 70 parts by weight Foaming agent: Amount of air bubble volume to 50% relative to mortar Increase temperature of air mortar by hydration of cement CC
The measurement was performed with a thermocouple, and the expansion pressure (including pressure measurement) generated at this time was examined with a wire strain gauge. The results are shown in Table 1.

The temperature was measured at one point in the center of the filled air mortar, and the expansion pressure was measured at two points A, B and C facing each other in FIG. .

[0026]

[Table 1]

As is clear from Table 1, the cement-based backfill material for retaining walls of the present invention has a small amount of heat generated during hydration and can significantly reduce the expansion pressure.

[0028]

As described in detail above, the cement-based backfill material for retaining wall of the present invention has a small amount of heat generation during hydration, and therefore,
Since the expansion pressure applied to the retaining wall is small, the displacement of the retaining wall after filling the backfill material can be suppressed as much as possible, and the retaining wall can be reliably prevented from cracking and damage, and the retaining wall construction with excellent durability can be performed. Is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a retaining wall construction method.

FIG. 2 is a perspective view of a frame used in Examples and Comparative Examples.

[Explanation of symbols]

 1 Embankment or cut slope 2 (2a, 2b, 2c, 2d) Retaining wall 3 Cement-based backfilling material 4 Frame

Claims (1)

[Claims] 1. A cement-based backfill material for a retaining wall, wherein low-heat cement and / or ultra-low-heat cement is used as the cement.