Suction accurately controlled pressure plate instrument capable of directly saturating soil sample

Abstract

The invention discloses a suction accurately controlled pressure plate instrument capable of directly saturating a soil sample. The instrument mainly comprises a pressure chamber system, a suction control system, a soil sample air exhaust saturation system, a scouring system, a water quality measuring system, an automatic data acquisition system and the like, and is characterized in that a sample preparation device is tightly contacted with a clay plate through threads, so that the sealing performance of the sample preparation device and the clay plate is ensured; the changes of suction and the water content of the soil sample are monitored and controlled in real time by combining a high-accuracy electronic pressure gauge with an electronic balance; a water storage outer chamber with an upper opening is formed, and a temperature control heating rod ensures that the temperature of an inner chamber is basically constant; water is stored in the inner chamber, and filter paper is soaked in the water, so that the air humidity of the inner chamber is basically saturated; and the inner chamber is improved and matched with a vacuum pump and a water storage tank, so that a new function of performing air exhaust saturation on the soil sample is realized. A measuring result of a soil-water characteristic curve is accurate, particularly test accuracy under the condition of low suction is improved, and a measuring method is convenient.

Description

Technical field [0001] The invention relates to a device for measuring the soil-water characteristic curve of a soil sample, in particular to a suction precision control pressure plate instrument that can directly saturate the soil sample. Background technique [0002] The soil-water characteristic curve refers to the relationship curve between soil suction and soil water content, saturation or volumetric water content. The soil-water characteristic curve is an important part of the constitutive model of unsaturated soil. It can be used to estimate the strength and permeability coefficient of unsaturated soil. Therefore, it is a key parameter and basic test content in unsaturated soil mechanics. At present, the soil-water characteristic curve of soil at home and abroad is generally measured by pressure plate instrument or permeation consolidation type pressure plate instrument, etc. These pressure plate instruments have the following problems in the use process: [0003] (1) The i...

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Problems solved by technology

[0003] (1) The initial saturation condition of the soil sample is not easy to realize

Due to the gap between the sample preparation device and the clay plate of the traditional pressure plate instrument, the water in the saturated soil sample will flow out before the test starts, resulting in that after the test, the measured data cannot be used to accurately calculate the pressure under low suction conditions. Moisture content of soil sample

[0004] (2) Low suction conditions are not easy to control

The traditional control of soil suction is only divided into high and low levels. Due to the large range of the low pressure section, it is limited by the accuracy of the pressure gauge and it is difficult to accurately reflect the actual suction value. The measurement of the soil water characteristic curve in the low suction range It has a great impact, especially for the soil-water characteristic curve of cracked soil, which is difficult to accurately measure

[0005] (3) Lack of automation of data collection

The test data needs to be read regularly by the test personnel, which is easy to cause human error, affects the accuracy of the data, and cannot monitor the test process in real time

[0006] (4) The suction balance condition is not easy to determine

Because the low suction condition is not easy to control, and lack of real-time monitoring of soil moisture and suction changes during the test, the soil sample is affected by the unstable suction control during the test, making it difficult to judge the suction balance condition

[0007] (5) The temperature control effect of the pressure vessel is not good

The temperature of the pressure vessel is easy to change with the environment, causing water vapor to condense on the inner wall of the pressure vessel, which makes the determination of the water content of the soil sample have certain errors

[0008] (6) The air saturation in the pressure vessel is not easy to control

The unsaturated air around the soil sample will gradually evaporate the water in the soil sample, which affects the test results

[0009] (7) The error of water evaporation is easy to be ignored

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