CN-121994676-A - System and method for measuring infiltration rate of variable-angle type soil moisture with controllable flow

CN121994676ACN 121994676 ACN121994676 ACN 121994676ACN-121994676-A

Abstract

The invention relates to the technical field of soil physical property measurement, and provides a system and a method for measuring the infiltration rate of variable-angle soil moisture with controllable flow, wherein the system comprises an angle-variable support component (200) for controlling a rotary positioning angle test column (300), the test column (300) is a uniformly distributed split column, and a closed joint of the split column is used for sealing the filled test soil through a gasket (303); the flexible water supply assembly (400) is connected to test post (300) top, still includes visual compactor (100) of double control, compactor (100) are used for being right test soil in test post (300) presses real-time, carries out synchronous control to soil volume and soil body stress. The invention eliminates the marginal effect, is convenient for undisturbed sampling, is applicable to various angles, can accurately control the flow, realizes visual constant volume filling by utilizing mechanical stress feedback, and corrects the soil hydraulic characteristic of the Philip infiltration model based on compaction stress parameters to carry out high-precision measurement.

Inventors

MA ZIJIE
LI HANG
KONG WEIJIN
LIU XINMIN
TIAN RUI
TANG YING
LI RUI
LI BINXU

Assignees

西南大学

Dates

Publication Date: 20260508
Application Date: 20260312

Claims (9)

1. The variable-angle type soil moisture infiltration rate measuring system with the controllable flow is characterized by comprising an angle-variable supporting component (200) and a rotary positioning angle measuring column (300), wherein the measuring column (300) is a split type column body which is evenly distributed, the closed joint of the split type column body is used for sealing test soil filled in through a gasket (303), the top end of the measuring column (300) is connected with a flexible water supply component (400), the variable-angle type soil moisture infiltration rate measuring system further comprises a double-control visual compactor (100), and the compactor (100) is used for synchronously controlling the volume and the stress of soil when the test soil in the measuring column (300) is pressed.
2. The variable-angle soil moisture infiltration rate measuring system with controllable flow rate according to claim 1, wherein the compactor (100) comprises an external cylindrical handle sleeve (101), a central pressing rod (102) is arranged in the sleeve in a sliding mode, the bottom end of the central pressing rod (102) extends out of the handle sleeve (101), the tail end of the central pressing rod is connected with a compaction bottom plate, three-color indication areas are arranged on the central pressing rod (102) in the handle sleeve (101) and correspond to under-pressure, compliance and overpressure states respectively, a check spring (103) is arranged between the inner wall of the top end of the handle sleeve (101) and the top end of the central pressing rod (102), the check spring (103) has a calibrated stiffness coefficient k, a limiting stop ring (104) with an adjustable position is sleeved on the lower portion of the central pressing rod (102) and is located outside the handle sleeve (101) and fixed through a locking screw, and a transparent observation window is arranged on the side wall of the handle sleeve (101) corresponding to the three-color indication areas.
3. The system for measuring the infiltration rate of the soil moisture with the variable angle and controllable flow rate according to claim 2, wherein the variable angle supporting component (200) comprises a base (201) and a stand column (202) arranged on the base, an angle dial (203) with the angle of 0-180 degrees is fixedly connected in the stand column (202), a transparent rotatable shaft lever (205) fixed through a locking wheel (207) is arranged in front of the angle dial (203), an angle indication arrow is marked on the rotatable shaft lever (205), and hoop clamps (206) are arranged at two ends of the rotatable shaft lever (205) and used for clamping the test column (300).
4. The system for measuring the infiltration rate of soil moisture by changing an angle with controllable flow according to claim 3, wherein the two sides of the bottom end of the angle dial (203) are provided with telescopic spring positioning pins (204) for positioning the rotatable shaft lever (205).
5. The system for measuring the infiltration rate of soil moisture by varying an angle with a controllable flow according to claim 4, wherein the test column (300) has at least two flaps.
6. The system for measuring the infiltration rate of soil moisture by varying an angle with a controllable flow according to claim 5, wherein the gasket (303) is a silica gel sealing pad with a Shore hardness of 40-60.
7. The system for measuring the infiltration rate of the soil moisture with the variable angle of the controllable flow according to claim 5, wherein when the test column (300) is two-piece, the first half pipe (301) is made of transparent polymethyl methacrylate (PMMA) material, the outer wall is provided with length scale marks, the inner wall is coated with a microporous polyurethane coating (304) of a water sensitive tracer material, the second half pipe is internally provided with a rough layer, and the rough layer is formed by coating epoxy resin glue on the inner wall of the second half pipe (302) and uniformly bonding standard PMMA particles with the particle size of 0.5-1.0 mm.
8. The system for measuring the infiltration rate of the soil moisture with the variable angle of the controllable flow according to claim 7, wherein the flexible water supply assembly (400) is connected with a constant water head water supply bottle (401), an upstream liquid guide tube (402), a micro flow regulator (403), a downstream liquid guide tube (402) and an infiltration dripper (404) from top to bottom, the micro flow regulator (403) is of a needle valve type structure, a valve core adopts a conical needle valve with a high length-diameter ratio, the upper part of the valve rod is connected with a micrometer differential regulating hand wheel, and the axial displacement of the valve needle is controlled to be at least 0.01 mm.
9. A method for determining the rate of infiltration of soil moisture by a controlled flow rate variable angle soil moisture determination system according to claim 8, comprising the steps of: S1, assembling the split type test column (300) and adopting the gasket (303) to separate and seal; S2, filling a test soil sample, which specifically comprises the following steps: s2.1, calculating the required soil weight of the air-dried and sieved soil sample to be detected according to the preset soil volume weight; S2.2, filling soil into the test column (300) in a layered manner, setting a single-layer compaction height and a target volume weight for preventing obvious interface blocking water flow between soil layers, adjusting the limit stop ring (104) of the compactor (100), filling quantitative soil samples for compaction until the limit stop ring (104) contacts the top end of the test column (300), simultaneously observing a color band area in an observation window, recording the current spring compression amount reading x i as a structural stress index of the soil of the layer if the color band is displayed in a compliance area, and then calculating the average compaction stress index of the whole column The following formula: (1) Wherein, the The device is characterized in that the device is a full column average pressure index with the unit of kPa, k is the stiffness coefficient of a check spring in the compaction device (100) with the unit of N/mm, x i is the compression reading of the check spring (103) with the unit of mm when the i-th layer of soil is compacted to reach a constant volume state, N is the total number of layers of soil column layered filling, D is the inner diameter of a test column (300) with the unit of cm; S2.3, installing a water inlet end cover at the top of the test column (300); s3, performing an infiltration rate measurement experiment, specifically comprising the following steps: S3.1, fixing a filled test column (300) on a hoop-type clamp (206), rotating an arrow on a rotatable shaft lever (205) until the arrow points to a 90-degree position of an angle dial (203) if the test column (300) is in a vertical state, screwing a locking wheel (207), unscrewing the locking wheel (207) if the test column is used for horizontal infiltration experiments, slowly rotating the rotatable shaft lever (205) by 90 degrees, wherein the arrow on the rotatable shaft lever (205) points to a 180-degree position of the angle dial (203) and is fixed through a telescopic spring-type positioning pin (204), screwing the locking wheel (207) to lock, and locking the test column (300) until the test column (300) is in a stable horizontal state; s3.2, regulating the micro-flow regulator (403) to a fully-opened state, pre-calculating required water supply flux according to the estimated saturated water conductivity of the soil, finely regulating a knob of the micro-flow regulator (403), observing and controlling the dropping rate to enable the dropping rate to be stable at a preset flux, wherein the soil surface is free of accumulated water at the moment, and the water flow infiltrates in a non-saturated state; S3.3, after the experiment begins to be instantaneously timed, recording the scale position of the downward advancing of the wetting front along with time by naked eyes or using a time-delay photographic device through a first half pipe (301), simultaneously recording the water level change of a constant water head water supply bottle (401), and calculating the accumulated infiltration amount; s3.4 because the compaction resistance required for each layer of soil when the same volume is reached may vary due to small differences in aggregate hardness or grain size, the use of Introducing correction factors The traditional Philip infiltration model is modified for the infiltration rate S: (2) In the formula, S 0 is the standard permeability, beta is the soil particle compression sensitivity coefficient, and the unit is kpa -1 ; data fitting was then performed using a correction model, as follows: (3) In the above formula, S 0 is the standard permeability, beta is the soil particle compression sensitivity coefficient, the unit is kpa -1 , t is the infiltration time, and the unit is min; Carrying out nonlinear regression by utilizing the measured Z-t data, and inverting to obtain a standard permeability S 0 and a steady permeability A after structural stress correction; S4, nondestructive sampling of an experiment, after the experiment is finished, disconnecting the flexible water supply assembly (400), taking down the test column (300), separating the split of the test column (300) to obtain a complete cylindrical soil column, using a circular stainless steel slice to transversely slice the soil column according to a preset interval, putting the cut soil sample into a container, and measuring the volume moisture content and suction distribution of each section by adopting a drying method, thereby drawing an accurate soil moisture characteristic curve or verifying infiltration model parameters.

Description

System and method for measuring infiltration rate of variable-angle type soil moisture with controllable flow Technical Field The invention relates to the technical field of soil physical property measurement, in particular to a system and a method for measuring the infiltration rate of variable-angle soil moisture with controllable flow. Background Soil moisture infiltration characteristics are important parameters for researching soil erosion, making farmland irrigation system and evaluating water and soil resources. In soil physics research, the mode of moisture infiltration is generally divided into vertical infiltration by the combined action of gravity and matrix potential and horizontal infiltration by the suction force of matrix potential, with gravity being perpendicular to the flow direction. The accurate measurement of the vertical and horizontal water conductivity of soil and the establishment of the accurate functional relation between the migration distance (Z) of a wetting front and the time (t) are basic requirements of soil physics. The existing measurement method mainly has the following 5 problems: 1. filling the "density-structure" binary paradox is that the traditional earth column experiment only controls the dry sample density (ρd=m/V), but ignores the damage of the soil structure in the process of reaching the density. The same density can be either perfect aggregate accumulation (low stress) or crushed powder compaction (high stress), and different soils can ensure consistency of the densities, and the natural distribution structure of soil particles can be greatly influenced by using artificial pressure compaction, so that the actual measured Philip model parameters (such as the permeability S) can be greatly fluctuated in repeated experiments, and the physical consistency is lacking; 2. The function is single, the existing experimental device can only measure the infiltration in one direction. For example, a double-ring infiltration instrument or a traditional vertical earth column is adopted for vertical infiltration, and a special horizontal soil box is required for horizontal infiltration, so that two sets of different equipment are required to be prepared when scientific researchers perform anisotropic research, and the experimental cost and the operation complexity are increased; 3. In the indoor soil column experiment, when filling the soil column, the soil particles and the smooth wall tend to have larger porosity, so that water flows quickly pass along the wall to generate preferential flow, the measured infiltration rate is larger than the actual matrix infiltration rate of the soil, and the accuracy of data is seriously affected; 4. The observation and sampling are difficult, and most of the traditional soil columns are opaque metal or PVC pipes, so that the advancing process of the wetting front cannot be observed in real time. Although some devices use transparent organic glass, accurate infiltration peak positions are difficult to determine only by naked eye reading; 5. The upper soil structure is easy to be damaged, the existing earth column infiltration device mostly adopts a fixed water head method for forming a fixed water head on the earth column surface, and the method has obvious defects. Firstly, unsaturated infiltration cannot be simulated, surface soil is forced to be saturated rapidly, the non-ponding infiltration process cannot be simulated, and great difference exists between the non-ponding infiltration process and the actual infiltration condition. Secondly, the surface soil structure can be damaged, long-term ponding soaking can lead to rapid disintegration of surface soil aggregates, so that the soil rapidly reaches a moisture saturation condition, the original pore structure of the soil is changed, and the measured infiltration rate gradually deviates from a true value. Further, it is extremely difficult to take out an undisturbed soil sample from a slender pipe after the experiment is finished and to measure the layering moisture content, and the soil structure is often destroyed when the soil column is pushed out. Therefore, there is a need for an assay system that can be modified from the loading mechanism, the observation means, and the algorithm in three dimensions simultaneously. Disclosure of Invention The invention aims to provide a system and a method for measuring the infiltration rate of the water in the angle-type soil with controllable flow. The invention provides the following technical scheme: The variable-angle type soil moisture infiltration rate measurement system with the controllable flow comprises a variable-angle supporting component (200) and is used for controlling a rotary positioning angle test column (300), wherein the test column (300) is a split type column body which is evenly distributed, the closed joint of the split type column body is used for sealing test soil filled in through a gasket (303), the top end of the tes