Device and method for testing frost heaving force of frozen soil under high load

Abstract

The invention discloses a test device and a test method for frost heaving force of frozen soil under high load. The test device comprises a temperature control chamber arranged in a refrigeration device, a loading device arranged in the temperature control chamber, a frost heaving amount monitoring device and a temperature monitoring control device, a loess sample is placed on the loading device, the loading device is connected with the transmission stand column and the loading plates through the loading head of the upper loading fixing device, and the acting force of the transmission stand column is applied to the loess sample between the loading plates; a lever loading system connected to the transmission column is arranged below the loading device, and the test precision of the frost heaving force of the frozen soil under different loads is adjusted through different gravities applied to the loading arm, so that the frost heaving capacity of the loess sample under different dry densities and water contents is obtained. According to the invention, a non-contact combined temperature measurement mode and a lever ratio continuously adjustable loading device are adopted, so that high-stress working conditions in projects such as building foundations and heavy roadbeds can be simulated, and reliable data are provided for research on frost heaving characteristics of frozen soil under complex load conditions such as subway tunnels and bridge foundations.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of soil testing and experiment, in particular to a test device and test method for frozen soil frost heaving force under high load. BACKGROUND

[0002] China has a vast seasonal frozen soil area, accounting for 53.5% of the country's land area. Frozen soil is a special soil, different from conventional soil. Frozen soil is affected by environmental temperature, and the ice and liquid water in the frozen soil transform into each other, causing the temperature sensitivity of the frozen soil. When water freezes into ice, the volume increases by about 9%, so the expansion of ice crystals in the soil causes the frozen soil to produce frost heaving deformation. Because of the low compressibility of ice, when the frost heaving deformation of frozen soil is inhibited, the frozen soil will generate a large normal frost heaving force. The Loess Plateau is a seasonal frozen soil area. In foundation, roadbed, tunnel, culvert, and frozen wall engineering, the frost heaving of loess can cause different degrees of deformation and cracking of the structure, and even cause structural damage. Therefore, the study of frost heaving force is of great significance to engineering construction in cold regions. Currently, most indoor test methods for testing frost heaving force are based on the overall vertical displacement of the soil sample to measure the frost heaving force, but this method can only measure the overall frost heaving force at the top of the soil sample, and cannot obtain the frost heaving characteristics of frozen soil under different upper loads. Therefore, it is necessary to conduct frost heaving characteristic test research on different water content and density test soil samples under different loads.

[0003] Chinese patent CN 117740867 A discloses a frozen soil frost heaving force and displacement test device, which is composed of a fixing system, a soil sample tank, a sensor system, and a temperature control system. By installing pressure sensors at different heights, the device can measure the frost heaving force at different positions and heights in the soil. In the closed circuit, a resistor is connected, and when the sensor moves due to the frost heaving of the soil, the resistance value connected changes, causing the current value to change, and thus the real-time vertical displacement of each sensor can be obtained. Although the device can measure the frost heaving force at different positions in the soil, it uses a fixed loading method, with a load range of only 0-500 kPa, and cannot achieve precise load adjustment, making it difficult to simulate the high load (such as ≥1000 kPa) conditions commonly found in actual engineering.

[0004] Therefore, it is necessary to provide a test device for frozen soil frost heaving force under high load to obtain the frost heaving characteristics of frozen soil under different upper high loads, which has become a technical problem that needs to be solved at present. SUMMARY

[0005] To solve the problem that the existing technology cannot obtain the frost heaving characteristics of frozen soil under different upper loads, the purpose of the present application is to provide a test device and test method for frozen soil frost heaving force under high load. By using the method of lever amplification loading + multi-variable collaborative monitoring, the load range is expanded to 4400 kPa, and synchronous high-precision acquisition and precise adjustment of load-frost heaving amount-temperature are achieved, solving the testing blank of existing devices in high load scenarios.

[0006] The present application is realized by the following technical solutions.

[0007] In one aspect of the present application, a high-load frozen soil frost heaving force testing device is provided, comprising a refrigeration device, a temperature control chamber arranged in the refrigeration device, a loading device, a frost heaving amount monitoring device and a temperature monitoring control device arranged in the temperature control chamber.

[0008] The loess sample is placed on the loading device, and the loading device is connected to the transmission column and the loading plate through the loading head of the upper loading fixing device, so that the force of the transmission column is applied to the loess sample between the loading plate.

[0009] A lever loading system connected to the transmission column is arranged below the loading device, the test precision of the frozen soil frost heaving force under different loads is adjusted by applying different gravity to the load arm, and the frost heaving amount of the loess sample under different dry densities and water contents is obtained.

[0010] Preferably, the loading device comprises an upper loading fixing mechanism, the loading fixing mechanism comprises a loading head, a transmission column, a loading plate and a base; the loading plate is placed on the base, the loess sample is placed between the loading plates, and the transmission column is connected to the loading plate below the loading head.

[0011] Preferably, the loading device further comprises a lower lever loading system, the lever loading system comprises a load arm, a counterweight and a weight set; the load arm is horizontally arranged below the base and is sleeved through the extension arm of the transmission column, one end of the load arm is provided with the counterweight, and the other end is hingedly connected to a vertically connected weight set.

[0012] Preferably, a frame for mounting the frost heaving amount monitoring device is arranged above the base, the upper part of the frost heaving amount monitoring device is connected to the frame, and the bottom part is in seamless contact with the loading plate; the frost heaving amount monitoring device adopts a telescopic displacement sensor.

[0013] Preferably, the loess sample is arranged in a cutting ring arranged by upper and lower water permeable stones and left and right sides, the diameter of the upper water permeable stone is the diameter of the loess sample, and the diameter of the lower water permeable stone is the outer diameter of the cutting ring.

[0014] Preferably, the temperature monitoring control device comprises a temperature sensor, a temperature controller, a digital display screen and a warning device.

[0015] Preferably, the temperature control chamber is completely closed, heat preservation materials are arranged on the inner wall of the temperature control chamber, and the temperature control chamber is connected to the refrigeration device through an air pipe; an elastic rubber plug is arranged at the connection between the air pipe and the top of the temperature control chamber, a linear cut is arranged on the elastic rubber plug, and the air pipe penetrates through the linear cut and extends into the temperature control chamber.

[0016] In another aspect of the present application, a test method of the high-load frozen soil frost heaving force testing device is provided, comprising:

[0017] Start the refrigeration device, connect the cold source into the temperature control room, and control the required temperature of the experiment through the temperature monitoring control device;

[0018] The loess sample is placed on the loading device, the loading head is connected to the loading plate through the loading fixing mechanism, different loads are applied to the weight group through the lever loading system, and the force is applied to the loess sample below the loading plate through the transmission column.

[0019] The frost heaving deformation of the loess sample under load is obtained through the frost heaving monitoring device, and when the frost heaving increment of two consecutive hours is less than 0.5% of the measured frost heaving, the load is stopped, the frost heaving deformation is stable, and the frost heaving of the loess sample under different dry densities and water contents is calculated.

[0020] As preferred, the temperature control room is maintained at a constant temperature of-3 DEG C ± 0.2 DEG C.

[0021] The lever loading system applies equal loads of 100kPa, 200kPa, 300kPa and 400kPa.

[0022] The present application has the following beneficial effects due to the above technical solutions:

[0023] 1. Precise temperature control: Compared with the traditional infrared temperature measurement technology, the environmental factors have a significant impact on the temperature measurement accuracy. In a low-temperature environment, the material, color, shape and environmental conditions of the object will reduce the temperature measurement accuracy. In a high-pressure environment and a blocked area, infrared temperature measurement is difficult to implement. Some systems using infrared temperature measurement, even with the assistance of infrared temperature measurement glass, will still affect the measurement accuracy after a long period of use. The present application uses a non-contact temperature measurement method, and the temperature control room is completely sealed and the inner wall is provided with thermal insulation materials, which can effectively maintain the internal constant temperature. Combined with the temperature monitoring control device, the environmental negative temperature can be accurately controlled within the range of set temperature ± 0.2 DEG C, which ensures the stability of the experimental conditions, reduces the interference of temperature fluctuation on the frost heaving experiment results of frozen soil, and makes the experimental data more reliable.

[0024] 2. High loading accuracy: The loading device realizes a loading accuracy of 12.5kPa through the combination of the continuous adjustable lever ratio (1:1~4:1) and the weight mass gradient group (5~50kg), and the maximum load can reach 4400kPa. It can simulate the high stress working conditions in building foundations, heavy roadbeds and other engineering projects, and provide reliable data for the study of the frost heaving characteristics of frozen soil under complex load conditions such as subway tunnels and bridge foundations.

[0025] 3. Monitoring the amount of frost heaving is sensitive: The frost heaving amount monitoring device uses a telescopic displacement sensor, the upper part is connected with the loading head, the bottom part is in seamless contact with the loading plate and is zeroed. This direct and close connection can more sensitively and accurately capture the subtle deformation of the loess sample during the frost heaving process. Compared with some existing devices that are rough and have poor sensitivity, it can record more accurate frost heaving amount change information, which is beneficial to in-depth analysis of the frost heaving law.

[0026] 4. Good sealing: The air pipe and the temperature control chamber are in close and seamless contact through the elastic rubber plug and special cut design, and the temperature control chamber itself is also completely closed. Good sealing prevents cold gas leakage and external environmental interference, ensures stable experimental environment, and is better than some existing equipment with insufficient sealing, which makes the experimental conditions such as temperature and humidity easily affected, ensuring the purity of experimental results.

[0027] 5. Multifunctional data acquisition: The device can be used to test the loess frost heaving characteristics under different vertical loads, and comprehensive frost heaving amount data of loess samples with different water contents and dry densities under various loads can be obtained. A set of devices can realize multidimensional variable research, while some existing devices have single function and can only conduct experiments for specific working conditions or a few variables. This device can provide more comprehensive and rich data support for loess frost heaving characteristic research and help more in-depth and extensive scientific analysis. BRIEF DESCRIPTION OF DRAWINGS

[0028] The drawings described herein are used to provide further understanding of the present application, constitute a part of this application, and do not constitute an improper limitation on the present application. In the drawings:

[0029] Figure 1 is a structural schematic view of a high-load frost heaving force test device;

[0030] Figure 2 is a structural schematic view of a loading device and a frost heaving amount measuring device;

[0031] Figure 3 is a structural schematic view of a temperature monitoring and control device;

[0032] Figure 4 is a structural schematic view of a temperature control chamber sealing structure.

[0033] In the drawings, 1 is a refrigeration device; 2 is a loading device; 201 is a loading head; 202 is a transmission column; 203 is a loading plate; 204 is a base; 205 is a load arm; 206 is a counterweight; 207 is a weight set; 3 is a frost heaving amount measuring device; 301 is a displacement sensor; 4 is a temperature monitoring and control device; 401 is a digital display screen; 402 is a warning device; 403 is a valve; 5 is an air pipe; 501 is an elastic rubber plug; 502 is a linear cut; 6 is a temperature control chamber; 601 is a heat preservation material; 7 is a water permeable stone; 8 is a cutting ring; 9 is a loess sample. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0035] like Figure 1 As shown, this embodiment of the invention provides a test device for the frost heave force of frozen soil under high load, including a refrigeration device 1, a control chamber 6 located inside the refrigeration device 1, a loading device 2, a frost heave monitoring device 3 and a temperature monitoring and control device 4 arranged inside the control chamber 6, and an air pipe 5 extending into the chamber of the control chamber 6 from the top of the control chamber 6.

[0036] The temperature control chamber 6 is completely enclosed to ensure its airtightness. Insulation material 601 is installed on the inner wall of the chamber 6 to ensure a constant temperature during the experiment. The gas pipe 5 includes a cold air inlet pipe and a cold air outlet pipe, both equipped with one-way valves 403. The temperature control chamber 6 is connected to a refrigeration unit via the gas pipe 5, and the temperature of the chamber 6 is controlled by valves 403. When the temperature inside the temperature control chamber reaches the predetermined value, the cold air valve is closed to maintain the temperature.

[0037] The loading device 2 is located in the upper part of the controlled temperature room 6. The frost heave monitoring device 3 is connected to the loading device 2, and the loess sample 9 is placed at the bottom of the loading device 2.

[0038] The loess sample 9 is placed in a ring cutter 8 arranged with upper and lower permeable stones 7 and left and right sides. The diameter of the upper permeable stone 7 is the diameter of the loess sample 9, and the diameter of the lower permeable stone 7 is the outer diameter of the ring cutter 8.

[0039] like Figure 2 As shown, the loading device 2 includes an upper loading and fixing mechanism and a bottom lever loading system. The loading and fixing mechanism includes a loading head 201, a transmission column 202, a loading plate 203, and a base 204; the lever loading system includes a load arm 205, a counterweight 206, and a weight set 207.

[0040] The loading head 201 is connected to the loading plate 203 through the transmission column 202, and applies force to the loading plate 203. The loading plate 203 includes upper and lower permeable stones 7. The loading plate 203 is located above the upper permeable stone 7. The loading head applies force to the permeable stone 7 above the loess sample 9, and then applies force to the test soil sample 9. The loess sample 9 is placed on the base 204.

[0041] A frame is connected to the base 204, and the frost heave monitoring device 3 is connected to the frame. The lever loading system includes a horizontally arranged load arm 205 provided at the bottom of the base 204, the middle of the load arm 205 is connected to the force transmission column 202, one end of the load arm 205 is provided with a counterweight 206, and the other end is hingedly connected to a vertically connected weight set 207.

[0042] The load arm 205 at the bottom of the base 204 serves as a lever fulcrum, one end of the load arm 205 is connected to the counterweight 206 for initial balance calibration, and the other end applies a load by suspending the weight set 207. When the weight set 207 exerts a gravitational force on the load arm, the load is transmitted to the force transmission column 202 and the loading plate 203 through the principle of lever amplification (the lever ratio can be adjusted by the fulcrum position, and the maximum amplification factor is 4 times), and finally acts on the permeable stone 7 above the loess sample 9.

[0043] In one embodiment, when the weight of the weight set is 10 kg and the lever ratio is 4:1, a load of 400 kPa can be applied to the sample. This design realizes flexible application and precise control of high load (maximum 4400 kPa) by adjusting the lever ratio combined with the weight set. When the lever ratio is 3:1 and the total weight of the weight set is 30 kg, a load of 900 kPa can be applied to the sample, with an error of ≤1.5%. This design breaks through the limitation of the load range of traditional devices (usually ≤2000 kPa).

[0044] The loading device 2 uses the load arm as a lever to amplify the weight of the weight set, and adjusts the lever ratio and the weight of the weight set to improve the loading accuracy and experimental accuracy, ensuring that the obtained test data is more true and reliable.

[0045] As shown in Figure 2 , the frost heave monitoring device 3 uses a telescopic displacement sensor 301, the upper part of which is connected to the frame on the base 204, and the bottom part is in seamless contact with the loading plate 203 and is zeroed.

[0046] As shown in Figure 2 , Figure 3 , the temperature monitoring and control device 4 is arranged on the loading plate 203, and the device includes a temperature sensor, a temperature controller, a digital display screen 401, and a warning device 402. The temperature controller sets the test temperature obtained by the temperature sensor to the required temperature, and needs to adjust the control cooling device 1 and the valves 403 on the cold air inlet pipe and the cold air outlet pipe to ensure that the temperature is constant during the test.

[0047] As shown in Figure 4 , an elastic rubber plug 501 is arranged at the connection between the bottom of the air pipe 5 and the top of the temperature control room 6, and a linear cut 502 is arranged in the center of the elastic rubber plug 501. The bottom end of the air pipe 5 penetrates through the linear cut 502 into the temperature control room, so as to ensure the tight and seamless contact between the air pipe 5 and the temperature control room 6.

[0048] The method steps of the high-load frozen soil frost heaving force test device are as follows:

[0049] Step 1, first start the refrigeration device 1, connect the air pipe 5 of the cold air source to the top of the temperature control room 6 to introduce the cold air source into the temperature control room 6, and during the operation, the environment temperature in the temperature control room 6 continuously decreases, and after about 2 hours, the environment temperature decreases to the required freezing negative temperature, that is, -3 DEG C.

[0050] Step 2, control the start and stop of the refrigeration device 1 through the temperature monitoring and control device 4, so that the environment temperature is kept in the range of -3 DEG C ± 0.2 DEG C; if it exceeds or is lower than the set temperature range, the warning device 402 warns.

[0051] Step 3, place the loess sample 9 on the loading device 2, and apply an upper load of 0-4400 kPa (such as 100 kPa, 200 kPa, 300 kPa, 400 kPa and the like) through the lever loading system, the loading head 201 applies force to the loading plate 203 through the transmission column 202, and then to the loess sample 9 below the water-permeable stone 7.

[0052] In the high-load test, the problems of insufficient loading precision and limited load range of the traditional device need to be overcome, and the present application solves the problems through the following scheme:

[0053] The lever amplification technology is adopted, the load arm with adjustable lever ratio (maximum amplification ratio 4 times) is combined with different quality weights (single weight 5-50 kg) to realize the accurate application of high load in stages.

[0054] The loading device base 204 is made of high-strength steel, the transmission column 202 and the loading plate 203 are coaxial through precise machining to ensure the stability of the structure and avoid the influence of eccentric load on the test precision.

[0055] At the same time of applying load, the temperature control room 6 maintains a constant temperature environment of -3 DEG C ± 0.2 DEG C, and the frost heaving amount monitoring device 3 (expansion displacement sensor precision 0.01 mm) is used to record the frost heaving deformation at the same time, which solves the technical problem that the existing device cannot couple high load and frost heaving property test, and realizes multi-variable collaborative control.

[0056] The loading device 2 uses the principle of lever, which not only amplifies the weight of the weight to apply load, but also flexibly adjusts the lever ratio and the weight quality, which improves the loading precision, provides more accurate loading conditions for high-load experiments, and better simulates the high-load scene in complex engineering practice compared with some existing devices with single loading mode and limited precision, so as to obtain accurate frozen soil mechanical response data and improve the loading precision.

[0057] Step 4: Observe the frost heave of the loess sample under a specific upper load using the frost heave monitoring device 3. Under negative temperature conditions, the soil sample freezes over a period of time, and the frost heave gradually increases over time. However, after a certain period, the increase gradually decreases until the frost heave stabilizes, at which point the load is stopped. The stabilization standard is set at 0.5% of the measured frost heave for two consecutive hours.

[0058] Calculate the frost heave of loess soil samples at different dry densities and moisture contents:

[0059] η=(ae -x +b)×100%

[0060] In the formula, η is the frost heave of the loess sample; x is the load on the upper part of the loess sample; a and b are the values ​​of the moisture content w and dry density ρ of the loess sample, respectively. d The coefficient, where a = mρ d +n / (wl), b=rρ d s w t In the formula, m is the dry density ρ d The influence coefficient of coefficient a; n and l are the influence coefficients of moisture content w on coefficient a; r is the correction coefficient of coefficient b; s is the dry density ρ. d The influence coefficient of coefficient b; t is the influence coefficient of moisture content w on coefficient b. Specifically, in one embodiment, m = 2.1325, n = 0.0026, l = 0.1973; r = 0.0035, s = 4.8516, t = -3.0354.

[0061] The apparatus of this invention can be used to conduct experimental studies on the frost heave characteristics of loess under different vertical loads, obtaining frost heave data for loess samples with different moisture contents and dry densities under different vertical loads. This provides reliable data support for the study of the frost heave characteristics of loess.

[0062] This invention overcomes the technical bottlenecks of existing frozen soil frost heave test devices in terms of load range, control accuracy, and multivariate coupling through high-load simulation, precise temperature control, real-time monitoring of multiple parameters, and structural optimization. It is suitable for studying the frost heave characteristics of foundations, roadbeds, and other engineering projects in seasonally frozen soil areas (such as the Loess Plateau) and has advantages such as accurate measurement, convenient operation, and strong environmental adaptability.

[0063] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A test device for high load under frozen soil frost heaving force, characterized by, The application relates to a temperature control device for loess, which comprises a refrigeration device (1), a temperature control room (6) arranged in the refrigeration device (1), a loading device (2), a frost heave monitoring device (3) and a temperature monitoring control device (4) arranged in the temperature control room (6). The loess sample (9) is arranged on the loading device (2), the loading head (201) of the upper loading fixing mechanism is connected with the transmission column (202) and the loading plate (203), and the force of the transmission column (202) is transmitted to the loess sample (9) between the loading plates (203). The lever loading system connected with the transmission column (202) is arranged below the loading device (2), different gravity is applied to the load arm (205), the test precision of the frost heave force of the frozen soil under different loads is adjusted, and the frost heave amount of the loess sample under different dry densities and water contents is obtained.

2. The test apparatus for frozen soil frost heave force under high load according to claim 1, characterized by, The loading device (2) comprises an upper loading fixing mechanism, the loading fixing mechanism comprises a loading head (201), a transmission column (202), a loading plate (203) and a base (204), the loading plate (203) is arranged on the base (204), the loess sample (9) is arranged between the loading plates (203), and the transmission column (202) is connected to the loading plates (203) below the loading head (201).

3. The test apparatus for frozen soil frost heave force under high load according to claim 2, characterized by, The lever loading system connected with the transmission column (202) is arranged below the loading device (2), different gravity is applied to the load arm (205), the test precision of the frost heave force of the frozen soil under different loads is adjusted, and the frost heave amount of the loess sample under different dry densities and water contents is obtained.

4. The test apparatus for frozen soil frost heave force under high load according to claim 2, characterized by, The base (204) is provided with a frame for mounting the frost heave monitoring device (3), the upper frame of the frost heave monitoring device (3) is connected, and the bottom is in seamless contact with the loading plate (203); the frost heave monitoring device (3) adopts a telescopic displacement sensor (301).

5. The test apparatus for frozen soil frost heave force under high load according to claim 1, characterized by, The loess sample (9) is arranged in the ring knife (8) arranged on the upper and lower water permeable stones (7) and the left and right sides, the diameter of the upper water permeable stone (7) is equal to that of the loess sample (9), and the diameter of the lower water permeable stone (7) is equal to the outer diameter of the ring knife (8).

6. The test apparatus for frozen soil frost heave force under high load according to claim 1, characterized by, The temperature monitoring control device (4) comprises a temperature sensor, a temperature controller, a digital display screen (401) and a warning device (402).

7. The test apparatus for frozen soil frost heave force under high load according to claim 1, characterized by, The temperature control room (6) is completely closed, heat preservation materials (601) are arranged on the inner wall of the temperature control room (6), and the temperature control room (6) is connected with the refrigeration device through the air pipe (5); the elastic rubber plug (501) is arranged on the top connection position of the air pipe (5) and the temperature control room (6), the linear cutout (502) is arranged on the elastic rubber plug (501), and the air pipe (5) penetrates through the linear cutout (502) and extends into the temperature control room (6).

8. A test method of the test apparatus for frost heaving force of frozen soil under high load according to any one of claims 1 to 7, characterized by, The application further relates to a temperature control method for loess, which comprises the following steps: The refrigeration device (1) is started, the cold air source is connected and introduced into the temperature control room (6), and the temperature required by the experiment is controlled through the temperature monitoring control device (4). The loess sample (9) is arranged on the loading device (2), the transmission column (202) is connected to the loading plate (203) through the loading fixing mechanism loading head (201), different loads are applied to the weight group (207) through the lever loading system, and the force is applied to the loess sample (9) below the loading plate (203) through the transmission column (202); The frost heaving deformation of the loess sample (9) under the action of the load is obtained through the frost heaving amount monitoring device (3), when the frost heaving increment of two consecutive hours is less than 0.5% of the measured frost heaving amount, the load is stopped, the frost heaving deformation is stable, and the frost heaving amount of the loess sample under different dry densities and water contents is calculated.

9. The test method for frozen soil frost heave forces under high loads according to claim 8, characterized in that, The temperature control room (6) is maintained at a constant temperature of-3℃±0.2℃; Equal loads of 100kPa, 200kPa, 300kPa and 400kPa are applied through the lever loading system.

10. The method of claim 8, wherein the method is characterized by, The frost heaving amount of the loess sample under different dry densities and water contents is calculated as follows: η = (ae -x + b) x 100% In the formula, η is the frost heaving amount of the loess sample; x is the upper load of the loess sample; a and b are respectively the coefficients of the water content w and the dry density ρ of the loess sample; wherein a=mρ d +n / (w-l), b=rρ d +n / (w-l), b=rρ d s w t ; in the formula, m is the influence coefficient of the dry density ρ d on the coefficient a; n and l are the influence coefficients of the water content w on the coefficient a; r is the correction coefficient of the coefficient b; s is the influence coefficient of the dry density ρ d on the coefficient b; t is the influence coefficient of the water content w on the coefficient b.

Images