JPH0361845A - Measuring method for water content of soil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIG. 3 is a schematic diagram showing a moisture content measuring device, in which four sensors 10 are fixed to a plate 12 with nuts 13, and a level 19 is installed in the center of the mounting plate 12. A shaft rod 18 is provided to protrude upward.

On the other hand, the lead wire 5 from the sensor 10 is connected to the calculation/judgment section 14 . The calculation determination unit 14 is connected to the select switch 1
6, a determination LED display section 17 and a display section 20 are provided.

FIG. 4 is a schematic diagram of a guide jig used in the present invention, and its shape is roughly the same as that of a sensor for a water content meter, but the mounting is done using a simple metal pin 1 that protrudes below the plate 12.
1, and is made slightly thinner than the sensor 10.

FIG. 5 is a block diagram showing the arithmetic operation and determination mechanism of the arithmetic machine by the computer in the arithmetic and determination section.

FIG. 6 is a diagram of a sensor cooling container, in which a plastic container 15 is filled with a coolant 22 containing water and has a lid 21 with holes 23 formed therein.

Next, an example of implementing the present invention will be shown.

Here, we will show an example in which improved soil is used as the burying material and the determination value of the moisture content required to achieve a predetermined degree of compaction after backfilling is standardized. First, the improved soil passed through a sieve of 4.751 mm was backfilled in two layers into a mold with a diameter of 15 cm and a height of 12 (!
After compacting the entire surface by hitting it 10 times from a height of , insert the guide jig shown in Figure 4 perpendicularly to the compacted surface.
The measurement position of the sensor was determined. Next, the guide jig was removed, and the sensor of the moisture content meter shown in FIG. 3 was carefully inserted into the previously drilled hole. At this time, the hole drilled by the guide jig was one size narrower than the sensor, and the sensor could be installed more easily and in good contact with the soil than if it were inserted by itself. Figures 7 and 8 are calibration curves for improved soil and sea sand, and Figure 7 shows the difference in sensor output vs. moisture content curves depending on whether or not a guide jig is used. From the figure,
Although measurements were performed three times at each measurement point, it is clear that using the guide jig results in smaller variations and a more stable calibration curve. Also, JI
According to SA1210, the relationship between soil dry density and moisture content (
Test method: Sea sand 2.5-b) Compacted improved soil 1.6-
Figures 9 and 10 show the characteristics of b.

From Figure 9, when the improved soil is compacted as specified, the degree of compaction is 90% or more when the moisture content is 8 to 20%, and 95% when the moisture content is in the range of 9.3 to 17.3%. It can be seen that the degree of compaction is higher than that. If this is replaced with the moisture content measuring device of the present invention, as shown in Table 1, the degree of compaction of 90% or more is in the range of 0.79 to 1°20V, and the degree of compaction of 95% or more is 0. It becomes .86-1.14V.

(Left below) Upper table moisture content (%) A: Compaction degree of 95% or more B: Compaction degree of 90 to 95% C: Compaction degree of 90% or less Using this as the judgment standard, a computer (CPU) Judgment section 1 inside
First, a cubic equation obtained from the calibration curve shown in FIG. 7 was memorized in the calculation section 1. As a result, when the select switch 16 on the main body is set to the improved soil, the calculation section 1 inside the CPU
The input/output port constituted by the determination unit 1 and the determination unit 1 receives sensor input signals. After the measurement is completed, the input signal of the sensor is calculated into a gravimetric moisture content by the calculation unit 1, and the moisture content display unit 20
Then, the process moves to the determination section 1. After a numerical comparison is made to determine which of the three categories shown in Table 1 the value of the weight water content inputted to the judgment section 1 falls into, the judgment LED display section 17 (A, B, C) is turned on. For example, when the input signal of the sensor is 1.1 V, the moisture content is displayed as 10%, and the determination LED display section 17A lights up.

The measurement principle of the sensor is a well-known method of determining the moisture content by emitting a certain amount of heat from inside the sensor and measuring the amount of heat that escapes. It takes time and continuous measurement is not possible. This is a phenomenon that occurs due to heat being trapped inside the sensor, and in order to improve this, sea sand (water content 10% ) is shown in FIG. 11. From the diagram,
If a cooling container is used after the measurement indicated by ○,
The base temperature returns to the original temperature in about 2 minutes, showing stable reproducibility, whereas when left to cool in the air without using the cooling container marked with Mu, the base temperature returns to the initial level in 2 minutes. This results in a measurement error of about 2 to 3%.

Furthermore, the waiting time until the next measurement takes approximately 10 minutes when the cooling container is not used, but when the cooling container is used, the measurement can be performed in approximately 2 minutes.

〔Effect of the invention〕 According to the method of the present invention, the following effects can be obtained.

1. By using the measurement formula creation guide jig, it can be easily installed even in compacted soil and in good contact with the object to be measured, improving measurement accuracy.

2. It is possible to determine the optimum moisture content of backfilling soil before backfilling the soil, and it can also be confirmed after backfilling.

3. By using a senna cooling container, the following measurements can be carried out in about 2 minutes.

[Brief explanation of drawings]

Figure 1 is a sectional view of the sensor, Figure 2 is a sectional view of another sensor, Figure 3 is a schematic diagram of the moisture content measuring device, Figure 4 is a schematic diagram of the guide jig, and Figure 5 is a diagram of the computer. Block diagram, Figure 6 is a plan and side view of the sensor cooler, Figure 7 is a calibration curve of voltage and moisture content of improved soil, Figure 8 is a calibration curve of voltage and moisture content of sea sand, Figure 9 and FIG. 10 is a graph showing the relationship between moisture content and dry density of improved soil, and FIG. 11 is a graph showing the relationship between time and temperature showing the results of repeated tests on sea sand. 1... Heater 2... Temperature sensor 5... Lead wire 7... Temperature loss body 10... Senna 11... Pin 14... Calculation determination section 15... Plastic container 21... ··lid

Claims (3)

[Claims] (1) Using a moisture content measuring device with multiple sensors,
In the method of measuring the moisture in soil by inserting the sensor into the soil, a guide jig is used which is equipped with a metal pin that is slightly thinner but approximately the same shape as the sensor of the measuring device, and is drilled into the soil in advance. A method for measuring soil moisture content, comprising: inserting the sensor into the soil after opening the container. (2) Remove the sensor of the measuring device that has finished measuring soil moisture content.
The soil moisture content measuring method according to claim (1), characterized in that the sensor is inserted into a cooling container into which a moisture-retaining substance containing sufficient water has been absorbed, and after cooling the sensor in a short time, the sensor is subjected to moisture measurement again. Measuring method. (3) The sensor is electrically connected to a computer that determines whether or not the moisture content of the backfilled soil is appropriate for reaching a predetermined degree of compaction after backfilling. The method for measuring soil moisture content according to claim (1).