JP2643721B2 - Early Quality Judgment Method of Soil Mortar for Column Type Underground Wall Construction Method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an early method for determining the quality of soil mortar in a column-type underground continuous wall method (hereinafter referred to as SMW method).

[0002]

2. Description of the Related Art In a SMW method, a soil mortar is formed by injecting and stirring a cement suspension while drilling a ground with a multiaxial auger. This is a method of inserting a core material (stress-bearing material) made of H-section steel or the like, and the end of each element is wrapped to improve the water stoppage.

[0003] The construction equipment of the SMW construction method is almost the same as the conventional single-axis column-type continuous underground continuous construction method, is simpler than the wall-type underground continuous wall construction method, the construction cycle is simple and short, and industrial waste is discharged. Therefore, the construction cost is smaller than that of the above-mentioned wall-type underground continuous wall, so that it is suitable for a mid-depth retaining wall. As shown in FIG. 1, the quality control of the SMW method is roughly classified into strength, water stoppage, construction accuracy, and workability. As is clear from the figure, quality control of the soil mortar is an important factor in the quality control of the SMW method.

At present, the quality of soil mortar is generally represented by strength, and the quality of the quality is determined by a uniaxial compression test of a test sample taken on site.

[0005]

However, in the above-mentioned conventional method, it takes one to four weeks after the preparation of the soil mortar until the quality of the soil mortar is determined. It will be difficult. The quality control of soil mortar on site: (a) Soil mortar has fluidity, uniformity and pore wall stability suitable for building a core material. (B) Having the above performance and having a predetermined strength after curing.

There are the above two items, and it is necessary to judge the quality before the core material is built. The present invention has been proposed in order to satisfy the above items, and the purpose thereof is to determine the quality of soil mortar in a short time until the core material is built into the soil mortar, which is highly applicable in the field. An object of the present invention is to provide an early method for determining the quality of soil mortar.

[0007]

In order to achieve the above-mentioned object, according to the early method for determining the quality of soil mortar in the SMW method according to the present invention, a sample is taken from a soil mortar created on a construction site, and Using the sample, the specific gravity of the soil mortar and the measurement of the exothermic temperature difference were measured by the hydrochloric acid heat of dissolution method, and the strength of the soil mortar on the 7th day was calculated from the specific gravity and the exothermic temperature difference of the soil mortar. A control range diagram consisting of the strength of 7 days of the material age, the specific gravity in the soil mortar, and the difference in heat generation temperature, and performing quality control of the soil mortar in real time based on the control range diagram. is there.

[0008]

According to the present invention, when the quality of soil mortar is determined at an early stage, the quality of the soil mortar is represented by the difference in heat generation temperature of the soil mortar and the specific gravity of the soil mortar as shown in the following equation (2). In what
The quality control items are strength, uniformity, fluidity, pore wall stabilizing function, etc. as shown in FIG. 1 above. However, in practice, if the cement amount of soil mortar and the specific gravity of the soil mortar are predetermined values, This is because it was determined that the required strength was exhibited, the construction status was good, and the quality such as uniformity and fluidity was also satisfied.

The present invention has been proposed based on such a viewpoint, and a control range diagram is prepared by measuring a heat generation temperature difference of a soil mortar and a specific gravity having a large correlation with a water content of the soil mortar. Based on this figure, the uniaxial compressive strength of the soil mortar can be estimated in a short time until the core material is installed on the soil mortar wall, easily, and in real time on site, enabling early quality judgment of the soil mortar. It's a trivial thing.

[0010]

The present invention will be described below with reference to examples. When applying SMW method according to the present invention in YamaTome Engineering, Mountain distillate calculated in the design strength of the soil mortar, safety factor F _S = 2
Σ ₂₈ = 6.0 kgf / cm ² in uniaxial compressive strength.

[0011] In the quality control of the day-to-day, early in the σ ₇ ≒ σ _28/2 from past experience in order to determine the results have been obtained, and therefore 7 days strength σ ₇ ≧ 3.0kgf /
We decided to perform quality control in cm ² . The standard examples of the basic composition of the soil mortar were determined as shown in Table 1 below as a result of test kneading.

[0012]

[Table 1]

The determination of the early method of determining the quality of soil mortar is based on the condition that the estimation of the uniaxial compressive strength can be carried out easily and in a short time until the core material of the ridge is built on the wall of the soil mortar. . The method of measuring soil mortar is to measure the amount of cement, (a) the heat of dissolution of hydrochloric acid, (b) the reverse titration method, (c) the method using a colorimeter, and (d) the measurement of the amount of cement. And (e) a method using a vibro checker for the purpose of measuring the water-cement ratio (W / C).

The colorimeter (c) measures the color of the soil mortar and attempts to estimate the amount of cement in the soil mortar according to the degree of the color difference. It was found to be unrelated to quantity. According to the early method for determining the quality of concrete by a vibro checker (e) specified by the Japan Society of Civil Engineers, the water / cement ratio W / C of concrete is directly measured. It is too large to measure.

The back titration method (b) by the Japan Concrete Institute is a method of dissolving cement in soil mortar with hydrochloric acid and back titrating with phenolphthalein as a reagent to estimate the amount of cement. There is a drawback that requires skill. The simple back titration method (d) is intended only for quantitative measurement of the amount of cement to determine whether or not an arbitrary standard is satisfied.

Further, the method of heat dissolution of hydrochloric acid of (a) by the Japan Concrete Institute is one of the early methods for judging the quality of concrete by the Japan Concrete Institute. The hydrochloric acid is added to a diluted sample of soil mortar, and the reaction with cement is performed. It measures heat as a temperature difference and estimates the amount of cement. There is no individual difference in the measured values, the reliability is high, and the test is easy.

As a result of conducting a laboratory test prior to the SMW method, it was confirmed that the difference between the exothermic temperature ΔT and the cement milk injection rate, ie, the exothermic temperature difference ΔT, and the unit cement amount C were proportional to each other. Was done. This result and the unit cement content C during the test kneading synthesize the relationship between the uniaxial compression strength sigma _7, Figure 2 shows the graph of the obtained relation between the heating temperature difference ΔT between the uniaxial compression strength sigma _7.

From the above graph, the reference strength σ of the uniaxial compressive strength
_When a heat generation temperature difference ΔT that satisfies ₇ = 3 kgf / cm ² is obtained, ΔT = 16 ° C., and the management reference value of the expected heat generation temperature difference is ΔT _a ≧ 16 ° C. Next, the implementation and review of early quality judgment of soil mortar will be described. For the early quality judgment of the soil mortar, a test was conducted by taking a sample at the current position with a sampler after the completion of kneading and before the core material was built. Samples were initially GL-5m, -10m, -15m
Although the sample was collected at each depth, no significant difference was observed in the difference between the exothermic temperature difference ΔT and the intensity σ ₇ depending on the sample collection depth. Therefore, only a sample of GL-15m was sampled and a required test was performed.

[0019] In the present inventors have study performed this time by the both the management reference value [Delta] T _a and the target uniaxial compressive strength of the heating temperature difference are clear enough, there was no problem about the quality of soil mortar. However, regression analysis of the test results during the construction revealed that the correlation between the exothermic temperature difference ΔT and the uniaxial compressive strength σ ₇ was smaller than originally thought, and it was difficult to manage only by the exothermic temperature difference by the hydrochloric acid heat-of-dissolution method.

FIG. 3 shows the relationship between the water content ω of the soil mortar and the uniaxial compressive strength of the mortar, and shows that the strength of the soil mortar tends to decrease as the water content ω increases. As a result, the determination method was reviewed so that not only the above-mentioned heat generation temperature difference ΔT but also the water content ω of the soil mortar was measured by a heating method or the like. Next, the result of the early quality judgment of the soil mortar will be described.

The results of single regression analysis performed to determine the correlation between the uniaxial compressive strength σ ₇ of soil mortar and various measured values (parameters) to determine the correlation coefficient are shown in Table 2 below.

[0022]

[Table 2]

Among the four measured values listed in Table 2, it was found that the one having the largest correlation coefficient was the water content ω of the soil mortar. Note that the heat generation temperature difference ΔT, that is, the correlation coefficient of the unit cement amount C was a numerical value smaller than originally thought. However, the strength cannot be developed unless a certain amount or more of cement is contained, and it is irrational to control the quality (strength) only by the water content.

Then, multiple regression analysis was performed between the water content ω of the soil mortar, the difference in heat generation temperature ΔT, and the uniaxial compressive strength σ ₇ to obtain the following equation. σ ₇ = 0.194ΔT−0.053ω + 3.658 (1) When quality control of soil mortar is performed on site, it is desirable to use a simpler test method, and therefore, the correlation with the water content ratio ω is large. When the multiple regression analysis is performed using the specific gravity ρ, the following equation is obtained.

Σ ₇ = 0.044ΔT + 15.948ρ-21.989 (2) As can be seen from the above equation, the uniaxial compressive strength σ ₇ of the soil mortar in the uniform sand layer is determined by the difference between the heat generation temperature ΔT and the soil mortar. It is proportional to both the specific gravity ρ. Next, the review of management standards will be described. FIG. 4 is a control range diagram showing the results of the multiple regression analysis obtained in the preceding section. In FIG. 4, the control range is set under the following conditions so that the uniaxial compression strength σ ₇ exceeds the target strength.

(1) The uniaxial compressive strength of the soil mortar on the 7th grade exceeds the target strength. That is, σ ₇ ≧
3.0 kgf / cm ² (2) The unit cement amount is higher than the standard. That is, ΔT
≧ 16.0 ° C (3) The building resistance of the core material of the retaining wall shall be small. That is, ρ ≦
1.70 (values from actual construction results) The control range diagram shown in FIG. 4 is used for the purpose of performing the above-described quality control, and the horizontal axis represents the specific gravity of a sample (soil mortar) collected by a sampler. The vertical axis represents the difference between the exothermic temperature of the sample (soil mortar) collected by the sampler. In the example, the relationship between the uniaxial compressive strength, the difference between the exothermic temperature and the specific gravity on the 7th day as shown in the above formula (2) The relationship was obtained. FIG. 4 is a control range diagram for measuring the exothermic temperature and specific gravity of the soil mortar and estimating the uniaxial compressive strength of the soil mortar on the age of 7 days. This is the region of the uniaxial compressive strength of the soil mortar on the age of 7 estimated from the above equation when the specific gravity is 1.7 or less. For example, the specific gravity is 1.
6. Uniaxial compressive strength of soil mortar of 7 days old when heat generation temperature difference is 20 ° C. is 4.4 kgf / cm ² . Figure ● mark estimated uniaxial compressive strength of wood age 7 days when the heat temperature difference of 20 ° C. is 4.4kgf / cm ^2. The symbol “△” indicates the result of the uniaxial compressive strength test of the sample collected on site. The length of the arrow connecting both △ and ● indicates the difference between the two. When quality control of soil mortar is performed on site using the control range diagram of FIG. 4, a cement-based suspension is injected and stirred while drilling the ground with an auger, and a columnar soil mortar is introduced into the ground. Immediately after forming the soil mortar, the soil mortar is sampled from a predetermined position in the formed soil mortar, and the specific gravity measurement and the heat generation temperature difference of the sample are measured by a hydrochloric acid dissolution method. If the measured value is within the oblique line in the control range diagram of FIG. 4, it can be confirmed that the target strength is 3 kgf / cm ² or more. If the result of the determination satisfies the reference value, the core material of the retaining wall such as an H-beam is immediately installed in the formed columnar soil mortar. If the judgment result is out of the shaded portion of the control range diagram, cement milk is again injected into the formed columnar soil mortar,
Stir. Among the shield works, it is located on the dip plateau, has a ground height of about TP20m, has a uniform sand layer mainly composed of a uniform Narita sand layer, has a viscous soil layer near the ground surface, and has a groundwater level of GL- It is around 3m and the excavation depth is 2
The test results of the 4 m starting shaft substantially satisfied the control range of FIG. 4, and the control range is considered to be appropriate.

As described above, according to the present invention, when the starting shaft is constructed by the SMW method, the unit cement amount in the soil mortar is measured by the hydrochloric acid dissolving heat method, and the water content of the soil mortar is measured during the construction. Added.
As for the control standard, the data was fed back during the construction and the reference value was modified and managed. However, the target strength, which is the final criterion for the quality judgment, was completed without any problem.

Although the management of the intermediate shaft constructed following the above-mentioned starting shaft was continued by the above-mentioned method, good results were obtained because the ground was similar to the starting shaft.

According to the present invention, as described above, in the SMW method, a sample is taken from the soil mortar created on the construction site, and the specific gravity of the soil mortar is measured by the heat dissolution method using hydrochloric acid using the same sample. Measure the difference,
Along with calculating the seven-day strength of soil mortar from the specific gravity and the difference in heat generation temperature in the same soil mortar, a control range diagram comprising the seven-day strength of the soil mortar and the specific gravity of the heat generation temperature difference, soil mortar is provided, By measuring the quality of the soil mortar based on the same figure, the measurement time is performed in a short time of 30 minutes or less required for the core material to be built into the soil mortar in erection work,
The accuracy of the measured values such as the unit cement amount is good, the test is easy, and the quality of the soil mortar can be measured in real time on site.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a quality control table of the SMW method.

FIG. 2 is an explanatory diagram showing a relationship between a heat generation temperature difference (ΔT) of a soil mortar and a uniaxial compressive strength (σ ₇ ).

FIG. 3 is an explanatory diagram showing a relationship between a water content (ω) of a soil mortar and a uniaxial compressive strength (σ ₇ ).

FIG. 4 is a management range diagram showing a relationship between an estimated uniaxial compressive strength of a soil mortar and a result of a uniaxial compressive strength test.

[Explanation of symbols]

ΔT Exothermic temperature difference C Unit cement amount of soil mortar σ ₇ Uniaxial compressive strength of soil mortar ω Water content ρ Specific gravity ΔT _a Control standard value of exothermic temperature difference

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeki Ihara 4-6-115 Sendagaya, Shibuya-ku, Tokyo Inside Fujita Co., Ltd. (72) Koichi Kishi Inventor 4-6-115 Sendagaya, Shibuya-ku, Tokyo Fujitanai (72) Inventor Seikage Pyeongchang 4-6-1 Sendagaya, Shibuya-ku, Tokyo Fujitanai Co., Ltd. 56) References JP-A-63-21466 (JP, A) JP-A-2-276965 (JP, A) JP-A-2-275355 (JP, A) JP-A-58-43696 (JP, B2) JP-A 60-41923 (JP, B2)

Claims (1)

(57) [Claims] 1. A sample is taken from a soil mortar created on a construction site, and a specific gravity measurement of the soil mortar and a difference in heat generation temperature are measured by a hydrochloric acid dissolution method using the sample.
A seven-day strength of the soil mortar is calculated from the specific gravity and the heat generation temperature difference in the same soil mortar, and a management range diagram including the seven-day strength of the soil mortar, the specific gravity and the heat generation temperature difference in the soil mortar. An early method for determining the quality of soil mortar in a column-type underground continuous wall construction method, in which the quality of soil mortar is controlled in real time based on the control range diagram.