Portable earthen ruins in-situ permeameter

Abstract

The invention discloses a portable earthen ruin in-situ permeameter which is structurally composed of a water storage barrel, a pressure regulating bin, a funnel, a permeable stone, a pressure regulating pipe, a gas conveying pipe, two valves, a valve with a barometer, a water level sensor and a notebook computer, the bottom of the water storage barrel is open, the permeable stone is placed at the opening, the number of the valves is two, and the pressure regulating pipe is arranged in the water storage barrel. Comprising a first valve and a second valve, the two valves and a funnel are all arranged on the upper portion of a water storage cylinder, the first valve is located at the joint of the funnel and the water storage cylinder, a water level sensor is arranged in the water storage cylinder, a notebook computer is connected outside the water storage cylinder, the periphery of a pressure regulating bin is sealed, and the upper portion of the pressure regulating bin is connected with a pressure regulating pipe and a valve with a barometer. The side edge of the water storage cylinder is connected with a second valve. The pressure adjusting bin is communicated with the water storage cylinder through an air conveying pipe. The portable earthen ruin in-situ permeameter provided by the invention is high in measurement precision and low in cost, the portability is improved, and the automation of reading is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geotechnical engineering, and particularly relates to a portable in-situ permeameter for earthen sites. BACKGROUND

[0002] Earthen sites are immovable cultural heritage with important social, cultural, historical, artistic and scientific values, which are mainly made of soil. Earthen sites are usually directly exposed to the natural environment, and are affected by sunlight, wind erosion, rainfall erosion, freeze-thaw degradation and salinization, gradually developing various diseases. Evaluating the basic properties of site soil is of great significance to understanding the disease development process and preservation status of earthen sites. Permeability reflects the hydrodynamic characteristics of soil and embodies the water-carrying capacity of the pores of site soil. High permeability usually reflects large porosity and pore connectivity. In summer, high permeability of earthen sites may lead to more serious erosion. In winter, temperature fluctuations after snowfall cause repeated freeze-thaw in the snow-covered parts of earthen sites, and high permeability potentially increases the infiltration amount of snowmelt, aggravating the damage of the freeze-thaw process to earthen sites. Considering the complexity of field test conditions, the accuracy and representativeness of test results, the simplicity and portability of test equipment, and the destructiveness of the test process to the test object, current field test equipment is designed for natural soil. In order to obtain representative indicators, the infiltration area is large, so the infiltration surface needs to be processed to ensure flatness before testing. These characteristics limit the promotion of the equipment in the field of cultural relic protection. There is currently no instrument suitable for testing the in-situ permeability of earthen sites. Therefore, it is of great practical value to develop a simple in-situ permeameter for earthen sites, which is portable, low in cost, easy to operate and meets the requirements of on-site testing of earthen sites. SUMMARY

[0003] The application aims to solve the above problems and provide a portable in-situ permeameter for earthen sites, which is high in measurement accuracy, low in cost, improves portability and realizes automation of reading.

[0004] It is the following structure: composed of a water storage cylinder, a pressure regulating bin, a funnel, a water permeable stone, a pressure regulating pipe, a gas pipe, a valve, a valve with a gas pressure gauge, a water level sensor and a notebook computer, the bottom of the water storage cylinder is open, a water permeable stone is placed at the opening, the number of valves is two, including a first valve and a second valve, the two valves and the funnel are arranged on the upper part of the water storage cylinder, and the first valve is located at the connection between the funnel and the water storage cylinder, the water storage cylinder is provided with a water level sensor, and the notebook computer is connected outside, the pressure regulating bin is sealed around, the upper part is connected with the pressure regulating pipe and the valve with the gas pressure gauge, the side of the water storage cylinder is connected with the second valve, and the pressure regulating bin is communicated with the water storage cylinder through the gas pipe.

[0005] The water level sensor is a resistive water level sensor. The funnel facilitates adding water to the storage tank before the test. The valve is used to control the start and end of the test. The laptop is used to monitor the water level changes during the technical seepage test in real time.

[0006] The surface of the water tank has mechanical graduations for water level calibration.

[0007] The system consists mainly of a water storage tank and a pressure regulating chamber. The bottom of the water storage tank is open, and a permeable stone is placed at the opening to ensure uniform seepage. The upper part of the water storage tank has two valves and a funnel, one of which is located at the connection between the funnel and the water storage tank. The funnel facilitates adding water to the water storage tank before testing, while the valves control the start and end of the test. The water storage tank contains a resistive water level sensor, externally connected to a portable laptop computer for real-time monitoring of water level changes during the seepage test. Additionally, the surface of the water storage tank has mechanical graduations for water level calibration.

[0008] The constant pressure chamber is sealed on all sides, with a pressure regulating pipe and a valve equipped with a pressure gauge at the top. The constant pressure valve is tightly connected to the water storage tank, which is connected via a water supply pipe. During testing, water is first added to the funnel until the water storage tank is full. The water in the storage tank flows into the constant pressure chamber through the water supply pipe. When the water in the constant pressure chamber exceeds the bottom of the pressure regulating pipe, the constant pressure chamber begins to apply a constant pressure to the water storage tank, thus ensuring a constant head pressure at the permeable stone during the seepage process.

[0009] At the beginning of the infiltration test, due to the very low natural moisture content of the site soil, the initial infiltration process can be simplified to unidirectional infiltration:

[0010]

[0011] Where I1 is the one-dimensional cumulative infiltration amount, cm; t is time, s; and S is the soil moisture absorption rate, cm. 2 / s; K is the hydraulic conductivity in cm / s;

[0012] As the infiltration process continues, the moistening front diffuses, and the infiltration process becomes three-way infiltration:

[0013]

[0014] Where I3 is the infiltration amount of the three-dimensional infiltration process, in cm; r is the radius of the infiltration surface, in cm; θ0 and θ are the initial soil moisture content and the final soil moisture content after testing, respectively, in cm. 3 / cm 3 ;

[0015] By combining the two equations, we can obtain:

[0016]

[0017] in, C1 = S

[0018] There is the following relationship between C1 and C2:

[0019]

[0020] And:

[0021] Therefore, taking ΔI / Δt 0.5 as the y - coordinate and t 0.5 as the x - coordinate, after linear fitting, the intercept is equal to C1 and the slope is equal to 2C2, and the stable infiltration conductivity of the three - dimensional infiltration state is obtained; if the measured data is not a straight line, the steady - state method is used to solve. When the rammed earth can be approximately considered uniform within the test range, when the radius of the ponded water on the soil surface is r and the soil water potential is Ψ, the stable infiltration flux is I:

[0022] I = πr 2 (k - k0)+4rΨ

[0023] where I is the stable infiltration flux, cm 3 / s; r is the radius of the ponded water on the soil surface, cm; k0 is the conductivity at the water head h0, cm / s; k is the unsaturated conductivity at the water head h, cm / s; Ψ is the matrix potential flux, cm 2 / s; the matrix potential flux is equal to:

[0024]

[0025] The relationship between the matrix potential flux and the soil moisture absorption rate is:

[0026]

[0027] where b is the shape factor, generally taken as 0.55; θ0 and θ are the initial soil moisture content and the final moisture content after testing respectively, cm 3 / cm 3 ;

[0028] Since the moisture content of the soil at the site is very low in the natural state, so k0 << k, then:

[0029]

[0030] Then, the unsaturated conductivity is:

[0031]

[0032] where q s is the stable infiltration rate, cm / s; S in the above formula is equal to the slope of the initial stage of the curve with I as the y - axis and t 0.5 as the x - axis;

[0033] The unsaturated hydraulic conductivity of the archaeological site soil can be obtained by reading the air pressure value from the barometer and the data from the portable laptop, and by measuring the soil moisture content before and after the experiment.

[0034] The existing technology for in-situ testing of soil permeability is the double-ring infiltrator, primarily used to determine the infiltration rate. It is the most widely used and classic method for measuring soil infiltration rate. Current double-ring infiltrators mainly consist of three parts: an inner ring, an outer ring, and a Marshall bottle. The inner ring typically has a diameter of 35.5 cm, the outer ring a diameter of 50.5 cm, and a ring height of 25 cm. The Marshall bottle provides a constant water head source. In actual testing, due to the large contact area between the double rings and the ground surface, the surface must first be leveled to ensure uniform infiltration. Then, the double rings are driven into the soil to a depth of 12.5 cm, maintaining concentricity. Water is then supplied to both the inner and outer rings using the Marshall bottle. When the water head in the rings reaches 3 cm, the water level on the Marshall bottle is read. To ensure the accuracy of the test results, three completely repeated tests are required within a 3-meter range.

[0035] The existing technology has four drawbacks:

[0036] 1. The dual-ring infiltration apparatus consists of two concentric rings, inner and outer. If the two rings are not concentric during installation, it will severely affect the validity of the test process and cause serious interference. Due to the large size of the two rings, this problem is often encountered in actual testing. In addition, during the installation of the two rings, the tapping process may cause the concentric rings to deviate. If forced correction is made manually, it will disturb the contact between the two rings and the test surface, resulting in additional infiltration, which significantly affects the accuracy of the test.

[0037] 2. The double-ring test has stringent requirements for the flatness of the test site. The surface needs to be cleaned during installation. For areas with steep slopes, this equipment cannot be used for permeability testing. This limitation of the double-ring permeameter directly restricts its application in permeability testing of earthen sites.

[0038] 3. The double-ring test uses a Marshall bottle to provide a constant head of water. In order to obtain the change in water volume, it is usually necessary to take readings at regular intervals. The human readings cause human degree error and time accumulation error in the test results.

[0039] 4. The double-ring permeameter is large and inconvenient to carry, and the double-ring permeameter test takes a long time, usually several hours.

[0040] The technical problem to be solved by this invention:

[0041] 1. While ensuring testing accuracy, reduce the size of the equipment infiltration surface and the testing time, allowing for multiple tests within a small area to obtain more representative results.

[0042] 2. Reduce interference with the surface of the test object during testing, and reduce the requirements for the flatness of the infiltration surface during testing, so that it can be used for permeability testing of the top and facade of earthen ruins.

[0043] 3. Reduce the impact of human reading on test results and automate the reading process.

[0044] 4. Reduce the cost of the testing equipment and improve its portability so that it can meet the needs of on-site testing.

[0045] The portability of the test device of the present invention meets the minimally invasive requirements of field testing of earthen sites, and the versatility and simplicity of the test device eliminate the need for manual reading.

[0046] Beneficial effects:

[0047] 1. The device has a low manufacturing cost, with the entire set costing less than 500 yuan.

[0048] 2. This device can meet the requirements of non-destructive or minimally destructive testing of earthen sites, with a small testing impact range. Multiple sets of tests can be conducted simultaneously in a small area to obtain representative results.

[0049] 3. The device takes into account the needs of field testing. The materials used are lightweight, and the total weight is less than 2kg, which can be carried to the test site by a single person.

[0050] 4. This device eliminates the need for manual readings, minimizing the impact of human intervention on the results. Real-time computer data recording facilitates organized result processing. Attached Figure Description

[0051] Fig. 1 Overall schematic diagram of the invention;

[0052] Fig. 2 Front view of the present invention. Detailed Implementation

[0053] The following will refer to the appendices in the embodiments of the present invention. Figs. 1-2 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] Its structure is as follows: it consists of a water storage tank 1, a pressure regulating chamber 2, a funnel 3, a permeable stone 4, a pressure regulating pipe 5, an air supply pipe 6, a valve 7, a valve 8 with a pressure gauge, a water level sensor 9, and a laptop computer 10. The bottom of the water storage tank 1 is open, and a permeable stone 4 is placed at the opening. There are two valves 7, including a first valve 70 and a second valve 71. Both valves 7 and the funnel 3 are located on the upper part of the water storage tank 1. The first valve 70 is located at the connection between the funnel 3 and the water storage tank 1. There is a water level sensor 9 in the water storage tank 1, and the laptop computer 10 is connected to the outside. The pressure regulating chamber 2 is sealed on all sides, and the pressure regulating pipe 5 and the valve 8 with a pressure gauge are connected to the upper part. The second valve 71 is connected to the side of the water storage tank 3. The pressure regulating chamber 2 is connected to the water storage tank 1 through the air supply pipe 6.

[0055] The water level sensor 9 is a resistive water level sensor, the funnel 3 facilitates adding water to the water storage tank 1 before the test, the valve is used to control the start and end of the test, and the laptop 10 is used to monitor the water level changes during the technical seepage test in real time.

[0056] The surface of the water storage cylinder 1 has mechanical graduations for water level calibration.

[0057] It consists of a water storage tank, a pressure regulating chamber, a funnel, a permeable stone, a pressure regulating pipe, a gas supply pipe, two valves, a valve with a pressure gauge, a water level sensor, and a laptop computer. The water storage tank and pressure regulating chamber are the main components. The bottom of the water storage tank is open, and a permeable stone is placed at the opening to ensure uniform seepage. The upper part of the water storage tank has two valves and a funnel, one of which is located at the connection between the funnel and the water storage tank. The funnel facilitates adding water to the water storage tank before testing, and the valve controls the start and end of the test. The water storage tank contains a resistive water level sensor, which is externally connected to a portable laptop computer for real-time monitoring of water level changes during the seepage test. Additionally, the surface of the water storage tank has mechanical graduations for water level calibration.

[0058] The constant pressure chamber is sealed on all sides, with a pressure regulating pipe and a valve with a pressure gauge at the top. The constant pressure valve is tightly connected to the water storage tank, which is connected to the water storage tank through a water supply pipe. During the test, water is first added to the funnel until the water storage tank is full. The water in the water storage tank flows into the constant pressure chamber through the water supply pipe 6. When the water in the constant pressure chamber exceeds the bottom of the pressure regulating pipe 5, the constant pressure chamber begins to apply a constant pressure to the water storage tank 1, thereby keeping the water head pressure at the permeable stone 4 constant during the seepage process.

[0059] At the beginning of the infiltration test, due to the very low natural moisture content of the site soil, the initial infiltration process can be simplified to unidirectional infiltration:

[0060]

[0061] Where I1 is the one-dimensional cumulative infiltration amount, cm; t is time, s; and S is the soil moisture absorption rate, cm.2 / s; K is the hydraulic conductivity in cm / s;

[0062] As the infiltration process continues, the moistening front diffuses, and the infiltration process becomes three-way infiltration:

[0063]

[0064] Where I3 is the infiltration amount of the three-dimensional infiltration process, in cm; r is the radius of the infiltration surface, in cm; θ0 and θ are the initial soil moisture content and the final soil moisture content after testing, respectively, in cm. 3 / cm 3 ;

[0065] By combining the two equations, we can obtain:

[0066]

[0067] in, C1 = S

[0068] C1 and C2 have the following relationship:

[0069]

[0070] and:

[0071] Therefore, with ΔI / Δt 0.5 Let y be the coordinate, and t be the coordinate. 0.5 Using the x-coordinate as the x-coordinate, after linear fitting, the intercept equals C1, and the slope equals 2C2, yielding the steady-state infiltration conductivity in the triaxial infiltration state. If the measured data is not linear, a steady-state method is used to solve the problem. The rammed soil within the test area can be approximated as uniform. Therefore, when the radius of water accumulation on the soil surface is r and the soil water potential is Ψ, the steady-state infiltration flux is I:

[0072] I = πr 2 (k-k0)+4rΨ

[0073] Where I is the steady infiltration flux, cm 3 / s; r is the radius of water accumulation on the soil surface, cm; k0 is the hydraulic conductivity at a water head of h0, cm / s; k is the unsaturated hydraulic conductivity at a water head of h, cm / s; Ψ is the matrix potential flux, cm 2 / s; matrix potential flux equals:

[0074]

[0075] The relationship between matrix potential flux and soil moisture absorption rate is as follows:

[0076]

[0077] Among them, b is the shape factor, generally taken as 0.55; θ0 and θ are the initial water content of the soil and the final water content after testing, respectively, in cm 3 / cm 3 ;

[0078] Since the water content of the site soil is very low in its natural state, k0 << k, then:

[0079]

[0080] Then, the unsaturated hydraulic conductivity is:

[0081]

[0082] Among them, q s is the stable infiltration rate, in cm / s; S in the above formula is equal to the slope of the initial stage of the curve with I as the y-axis and t 0.5 as the x-axis;

[0083] By reading the air pressure value at the barometer 8 and the data at the portable laptop 10, and measuring the water content of the soil before and after the test, the unsaturated hydraulic conductivity of the site soil can be obtained.

[0084] During the test, first add water to the funnel to make the water storage cylinder full of water. The water in the water storage cylinder flows into the constant pressure chamber through the water delivery pipe 6. When the water in the constant pressure chamber submerges the lowest end of the pressure regulating pipe 5, the constant pressure chamber starts to apply a constant pressure to the water storage cylinder 1, so as to make the head pressure at the permeable stone 4 constant during the seepage process.

[0085] The cost of manufacturing this device is relatively low. Excluding the portable computer, the cost of the whole set of devices is within 500 yuan. Considering the requirements of on-site tests, the overall use is made of lightweight acrylic materials, with a total weight of less than 2 kg, and it can be carried to the test site by a single person. It takes less time for field tests, and the infiltration surface of the instrument is small, and multiple tests can be repeated within a small range to determine the hydraulic conductivity of the earth site.

[0086] Example 1

[0087] The following is the specific working process of the device: Before the test, a circular infiltration surface with a diameter of 5cm and a depth of 1cm is first excavated at the test site, and the surface soil moisture content θ0 is measured using an aluminum box. Then, the infiltration device is placed on the infiltration surface, and all valves except valve 7 are closed. Distilled water is then slowly poured into funnel 3 until it reaches outlet 7. At this time, water from the storage tank flows along the water delivery pipe into the constant pressure chamber until it reaches the bottom of the pressure regulating pipe, and then valve 7 is closed. At this time, the value displayed on the pressure gauge 8 is the product of the water's density and the water head height in the storage tank. Then, air is injected into the pressure regulating pipe to make the pressure gauge reading reach the target value. Then, the computer is turned on to start recording the water level and calibrating it. Then, valve 7 is opened to officially begin the infiltration test. During the experiment, the water level in the storage tank must not be lower than the top of the water delivery pipe 6. In addition, if the value in the pressure gauge 8 decreases during the test, it indicates that there is an air leak in the device, and the entire device needs to be checked for air tightness. After the test is completed, the device is removed, a small amount of soil sample is taken from the infiltration surface to test the water content θ, and then the relevant results of the infiltration test are calculated according to the method in 2.2.

[0088] Finally, it should be noted that the above description is only a preferred embodiment selected based on the principles and implementation methods of the present invention. The specific implementation methods described are not intended to limit the scope of protection of the present invention. Those skilled in the art can make various modifications and improvements to the technical solutions of the present invention. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A portable in-situ permeameter for earthen archaeological sites, characterized in that, The structure is as follows: It consists of a water storage cylinder (1), a pressure regulating chamber (2), a funnel (3), a permeable stone (4), a pressure regulating pipe (5), a gas transmission pipe (6), valves (7), a valve with a pressure gauge (8), a water level sensor (9) and a laptop computer (10). The bottom of the water storage cylinder (1) is open, and a permeable stone (4) is placed at the opening. The number of the valves (7) is two, including a first valve (70) and a second valve (71). The two valves (7) and the funnel (3) are both arranged at the upper part of the water storage cylinder (1). Among them, the first valve (70) is located at the connection between the funnel (3) and the water storage cylinder (1). There is a water level sensor (9) in the water storage cylinder (1), and it is externally connected to a laptop computer (10). The pressure regulating chamber (2) is sealed on all sides, and a pressure regulating pipe (5) and a valve with a pressure gauge (8) are connected to the upper part. The second valve (71) is connected to the side of the water storage cylinder (3). The pressure regulating chamber (2) is communicated with the water storage cylinder (1) through a gas transmission pipe (6).

2. The portable in-situ permeameter for earthen archaeological sites as described in claim 1, characterized in that, The water level sensor (9) is a resistive water level sensor. The funnel (3) is convenient for adding water into the water storage cylinder (1) before the test. The valves are used to control the start and end of the test. The laptop computer (10) is used to record the water level change during the seepage test in real time.

3. The portable in-situ permeameter for earthen sites as described in claim 1, characterized in that, The surface of the water storage cylinder (1) has mechanical scales for calibrating the water level.

4. A portable in-situ permeameter for earthen sites as described in claim 1, characterized in that, At the beginning of the infiltration test, due to the very low natural moisture content of the site soil, the initial infiltration process can be simplified as one-way infiltration: Where I1 is the one-dimensional cumulative infiltration amount, cm; t is time, s; and S is the soil moisture absorption rate, cm. 2 / s; K is the hydraulic conductivity in cm / s; As the infiltration process continues, the wetting front keeps spreading, and the infiltration process becomes three-way infiltration: Where I3 is the infiltration amount of the three-dimensional infiltration process, in cm; r is the radius of the infiltration surface, in cm; θ0 and θ are the initial soil moisture content and the final soil moisture content after testing, respectively, in cm. 3 / cm 3 ; Combining the two equations, we can get: in, There is the following relationship between C1 and C2: and: Therefore, with ΔI / Δt 0.5 Let y be the coordinate, and t be the coordinate. 0.5 Using the x-coordinate as the x-coordinate, after linear fitting, the intercept equals C1, and the slope equals 2C2, yielding the steady-state infiltration conductivity in the triaxial infiltration state. If the measured data is not linear, a steady-state method is used to solve the problem. The rammed soil within the test area can be approximated as uniform. Therefore, when the radius of water accumulation on the soil surface is r and the soil water potential is Ψ, the steady-state infiltration flux is I: I=πr 2 (k-k0)+4rΨ Where I is the steady infiltration flux, cm 3 / s; r is the radius of water accumulation on the soil surface, cm; k0 is the hydraulic conductivity at a water head of h0, cm / s; k is the unsaturated hydraulic conductivity at a water head of h, cm / s; Ψ is the matrix potential flux, cm 2 / s; matrix potential flux equals: The relationship between the matrix potential flux and the soil moisture absorption rate is: Where b is the shape factor, typically taken as 0.55; θ0 and θ are the initial soil moisture content and the final soil moisture content after testing, respectively, in cm. 3 / cm 3 ; Since the moisture content of the site soil is very low in the natural state, so k0 << k, then: Then, the unsaturated hydraulic conductivity is: Where, q s To stabilize the infiltration rate, cm / s; in the above formula, S is equal to t with I as the y-axis. 0.5 The slope of the curve in the initial stage is the x-axis. By reading the air pressure value at the pressure gauge (8) and the data at the portable laptop computer (10), and measuring the soil moisture content before and after the test, the unsaturated hydraulic conductivity of the site soil can be obtained.

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