A method for determining tillage depth based on penetration resistance

Abstract

The present invention relates to a method for distinguishing tillage depth based on penetration resistance. The method comprises: constructing a mathematical model of soil firmness and penetration depth, simulating the process of a probe penetrating the soil using simulation software EDEM and analyzing the simulation results, analyzing the disturbance effect of the probe on the soil based on the simulation results, and obtaining significant parameters and influence rates affecting soil firmness, and proposing an influence depth method and a stratification line method for distinguishing tillage depth. The method has the advantages of accurate measurement, stable and reliable results, and high work efficiency.

Description

Technical Field

[0001] The present invention relates to the field of soil mechanics applications, and in particular to a method for determining tillage depth based on penetration resistance. Background Art

[0002] In agricultural production, plowing is the most important and fundamental process, breaking up the soil, improving soil permeability, and evenly blending soil and fertilizer. Tillage depth, a key indicator of tillage quality, has a direct impact on soil physical properties, fertility, and crop growth.

[0003] The traditional method of measuring tillage depth is to randomly select several points in the field, manually clean the ditch bottom, measure with a steel ruler or tillage depth gauge, and then compare it with the actual set tillage depth to obtain the machine operation quality. This method has low work efficiency, high intensity, and is greatly affected by human factors, resulting in poor measurement accuracy.

[0004] Some scholars have proposed adding sensors to tillage equipment to measure tillage depth, such as posture sensors, ultrasonic and infrared sensors, optical sensors, and resistance sensors. These are new mechanical measurement methods that improve work efficiency compared to manual measurement, but are greatly affected by impurities in the field. If there are clods of soil, crop residues, weeds on the ground, or the ground is not flat enough, etc., the measurement accuracy of the sensor will be affected, and the measurement results may be inaccurate. Summary of the Invention

[0005] In response to the defects of the existing technology, the purpose of the present invention is to provide a method for determining the tillage depth based on penetration resistance, construct a mathematical model of penetration resistance, and combine field experiments to measure and determine the tillage depth. It is not easily affected by external factors such as human factors and soil impurities, can improve work efficiency and have a high accuracy of measurement results.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for determining tillage depth based on penetration resistance includes the following steps:

[0008] (1) Using the spherical pore expansion theory, a spherical pore expansion model of unsaturated soil is established to obtain the pore expansion pressure;

[0009] (2) Conduct indoor soil trench tests to determine the relationship between hole expansion pressure and penetration resistance, and obtain a mathematical model of the penetration resistance of the tillage layer;

[0010] (3) Conduct probe penetration simulation tests using EDEM simulation software, and analyze the disturbance effect of the probe on the soil, as well as the significant influencing factors and influencing rates of penetration resistance based on the simulation test results;

[0011] (4) Based on the analysis results of step (3), define the influence depth method or the layered line method to determine the tillage depth.

[0012] In step (1), the stress field, strain field and displacement field in the elastic-plastic zone are derived and analyzed according to the spherical hole expansion theory to obtain the probe expansion pressure, that is, the soil is expanded from radius a0 to a u The pressure required:

[0013]

[0014] in:

[0015]

[0016]

[0017]

[0018] σ v0 =gγh

[0019] Where p a is the hole expansion pressure; c is the soil cohesion; is the internal friction angle of soil; b is a parameter characterizing the effect of intermediate principal stress, with a value range of 0 to 1; m is the intermediate principal stress parameter, m≤1 under plane strain conditions, and m→1 when the soil enters the plastic state; K0 is the soil lateral pressure coefficient; σ v0 is the vertical stress of soil; g is the acceleration of gravity; γ is the bulk density of soil; h is the penetration depth; G is the shear modulus of soil.

[0020] Step (2) specifically includes: (2.1) conducting an indoor soil trough test, wherein the test equipment includes a probe, a universal testing machine, and a bucket, wherein the bucket contains the test soil;

[0021] The indoor test described in (2.2) set the soil moisture content range to 10% to 20%, divided into three levels: 10%, 15%, and 20%, and the soil density range was set to 1.1×10 3 kg / m 3 ~1.3×10 3 kg / m 3 , also divided into three levels: 1.1×10 3 kg / m 3 , 1.2×10 3 kg / m 3 , 1.3×10 3 kg / m 3 , do orthogonal test;

[0022] (2.3) Soil parameters at water contents of 10%, 15%, and 20% were measured by direct shear tests and soil sample crushing tests. The results were substituted into the calculation formula (1) for hole expansion pressure. Analysis revealed that, at different water contents and densities, the hole expansion pressure and penetration resistance have the following relationship, i.e., the mathematical model of penetration resistance is:

[0023]

[0024] Where q c is the penetration resistance; p a is the expansion pressure; r is the cone head radius; μ is the soil Poisson's ratio.

[0025] Step (3) is specifically as follows: using the Plackett-Burman test to screen the parameters of the plow layer and the plow bottom layer that have a significant impact on the penetration resistance value, and using the EDEM simulation software to perform a probe penetration simulation test, and using the Design Expert software to perform a variance analysis on the Plackett-Burman test. It is concluded that the only factors that have a significant impact on the penetration resistance of the dividing point between the plow layer and the plow bottom layer are the plow layer shear modulus and the plow bottom layer shear modulus, and the influence ratio of the two is 3:17.

[0026] The simulation test of step (3) shows that the change of probe resistance is related to the change of soil disturbance area and the shear modulus of the tillage layer. The specific steps of the influence depth method to determine the tillage depth are as follows:

[0027] (5.1) △h1 represents the distance between the probe and the plow layer, i.e., the depth of influence. The shear modulus G1 of the plow layer is set in the range of 1 MPa-50 MPa, divided into four levels for single factor analysis. EDEM software is used for simulation. Based on the simulation data, the shear modulus value of the plow layer is fitted with the depth of influence. The relationship between the distance △h1 between the probe and the plow layer and the shear modulus of the plow layer is obtained as follows:

[0028]

[0029] Where, △h1 is the impact depth; G1 is the shear modulus of the plow layer;

[0030] (5.2) Conduct a field test to measure soil parameters and probe penetration resistance and penetration depth. On the one hand, substitute the measured tillage layer soil parameters into the penetration resistance mathematical model obtained in step (2), draw the penetration resistance model curve based on the calculation results, and calculate the influence depth according to the above formula (3); on the other hand, draw the penetration resistance measured in the field test into a field test curve, and compare the two curves together. Before the penetration resistance of the field test curve begins to increase significantly, the displacement corresponding to the minimum difference in resistance between the two is the depth of the probe when the soil influence area approaches the plow bottom layer. Sum this depth with △h1, and the result is the tillage layer depth measured by the influence depth method.

[0031] The specific steps of the layering line method for determining tillage depth are as follows: (6.1) Define the layering line, which represents the resistance value at the interface affected by the shear modulus of the tillage layer and the plow bottom layer at different tillage depths. The model used for the layering line is consistent with the mathematical model of the penetration resistance of the tillage layer. The ratio of the shear modulus influence rate of the tillage layer and the plow bottom layer is 3:17, and the individual influence rates of the two are 15% and 85%, respectively. Set the shear modulus of the layering line to G λ , is determined simultaneously by the shear modulus of the plow layer and the plow bottom layer: G λ =15%G1+85%G2 (4)

[0032] Where G1 is the shear modulus of the plow layer; G2 is the shear modulus of the plow bottom layer.

[0033] (6-2) Conduct field tests to measure probe penetration depth, penetration resistance, plow layer shear modulus, plow bottom layer shear model and plow layer soil parameters. λ , and the soil parameter values ​​of the tillage layer are substituted into the penetration resistance mathematical model of formula (2). The stratification line is drawn according to the calculation results, and the field test curve is drawn with the penetration depth and penetration resistance of the field test. The intersection of the stratification line and the field test curve is the measured tillage depth of the stratification line method.

[0034] Beneficial effects: Based on theoretical analysis, the present invention constructs a mathematical model of penetration resistance, and combines the influencing factors of penetration resistance to propose a tillage depth discrimination method based on the influencing depth method and the layered method. Compared with the existing tillage depth detection method, its significant advantages are: ground weeds, ground flatness, soil clods and crops have little effect on the discrimination accuracy of the present invention, which can effectively reduce the discrimination error rate and effectively improve the tillage depth discrimination accuracy and work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Spherical hole expansion model

[0036] Figure 2 Probe penetration test

[0037] Figure 3 This is a graph showing the probe disturbance depth and the resistance inflection point.

[0038] Figure 4 is the influence depth of different shear moduli.

[0039] Figure 5 A comparison chart of the layered line method for different shear moduli.

[0040] Figure 6 Field trial map.

[0041] Figure 7 Comparison chart of test results. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The method for determining tillage depth based on penetration resistance provided by the present invention generally includes the following steps:

[0044] (1) Using the spherical pore expansion theory, a spherical pore expansion model of unsaturated soil is established to obtain the pore expansion pressure;

[0045] (2) Conducting indoor soil trench tests to determine the relationship between hole expansion pressure and penetration resistance, and obtaining a mathematical model of penetration resistance;

[0046] (3) The probe penetration simulation test was carried out using EDEM simulation software. The disturbance effect of the probe on the soil was analyzed based on the simulation results, and the significant factors and influence rates were obtained.

[0047] (4) Based on the analysis results of the simulation test, define the influence depth method to determine the tillage depth, or define the layered line method to determine the tillage depth

[0048] Furthermore, step (1) specifically includes:

[0049] (1.1) For unsaturated soil, the spherical cavity expansion model is as follows: Figure 1 As shown. The initial radius of the hole is a0, and the hole begins to expand due to the continuous internal pressure, and the final expansion radius is a u , the corresponding internal pressure is p u , at this time the radius of the plastic zone changes from r p0 Expand to r p , the displacement is u rp , the plastic zone range is a u ≤ r≤r p , the elastic range is r≥r p The initial effective stress of the hole is p0, the radial effective stress and the tangential effective stress are σ r and σ θ .

[0050] (1.2) For the topsoil layer, the unsaturated soil is assumed to be homogeneous and isotropic elastoplastic, and the magnitude of the initial radial stress is related to the soil depth. During the hole expansion process, the soil is assumed to obey Hooke's law for small strains in the elastic region and the uniform strength criterion for large strains in the plastic region.

[0051] Define the horizontal initial stress: σ r0 =σ θ0 =K0σ v0 =K0gγh

[0052] in:

[0053] σ r0 , σ θ0 ——horizontal initial radial stress and horizontal initial tangential stress, unit: Pa;

[0054] σ v0 ——vertical stress, unit: Pa;

[0055] K0——soil lateral pressure coefficient;

[0056] g——acceleration due to gravity, taken as 9.8N / kg;

[0057] γ——soil density, kg / m 3

[0058] h——penetration depth, in m;

[0059] (1.3) According to the spherical hole expansion theory, the stress field, strain field and displacement field in the elastic-plastic zone are derived and analyzed to obtain the probe expansion pressure, which is to expand the soil from radius a0 to a u The required pressure is as follows:

[0060]

[0061] According to the unified strength criterion

[0062]

[0063]

[0064]

[0065] σ v0 =gγh

[0066] Where p a is the expansion pressure, unit is Pa; c is the soil cohesion; is the internal friction angle of the soil; b is a parameter that characterizes the effect of the intermediate principal stress, usually ranging from 0 to 1; m is the intermediate principal stress parameter, under plane strain conditions, m≤1, and when the soil enters the plastic state, m→1; K0 is the soil lateral pressure coefficient; σ v0 is the vertical stress of soil, unit is Pa; g is the acceleration of gravity, m / s 2 ; γ is the soil bulk density, kg / m 3 ; h is the penetration depth, unit is m; G is the soil shear modulus, unit is Pa.

[0067] Furthermore, step (2) specifically includes:

[0068] (2.1) An indoor soil trough test was conducted. The soil in Lingou Village, Mengjin, Henan Province was used as the test object. The soil texture was silt clay loam.

[0069] The equipment used in the indoor test described in (2.2) includes a probe (material: 65Mn steel, length: 530mm, tip diameter: 14mm), a universal testing machine (DNS02-1KW), and a bucket (inner diameter: 124mm, height: 400mm). The soil is placed at a height of 300mm. The probe penetrates the soil at a speed of 8mm / s to a depth of 200mm. Figure 2 shown.

[0070] The indoor test described in (2.3) set the soil moisture content range to 10% to 20%, divided into three levels (10%, 15%, and 20%), and the soil density range to 1.1×10 3 kg / m 3 ~1.3×10 3 kg / m 3 , also divided into three levels (1.1×10 3 kg / m 3 , 1.2×10 3 kg / m 3 , 1.3×10 3 kg / m 3 ) to conduct orthogonal experiments.

[0071] (2-4) Soil parameter values ​​at water contents of 10%, 15%, and 20% were measured by direct shear tests and soil sample crushing tests. The results were substituted into the formula (1) for hole expansion pressure. For the convenience of calculation, the intermediate principal stress parameters b and m were both taken as 0.5. Through analysis, it was found that at different water contents and densities, the hole expansion pressure and penetration resistance have the following relationship

[0072]

[0073] Where q c is the penetration resistance, unit is N; p ais the expansion pressure, unit is Pa; r is the cone head radius, unit is cm; μ is the soil Poisson's ratio.

[0074] This mathematical model can replace indoor soil trench tests for penetration resistance analysis. Compared with laboratory penetration resistance, field soil has a solid plow layer below the tillage layer, and the penetration resistance will increase significantly when the probe approaches the plow layer. However, the soil trench test corresponding to the penetration resistance mathematical model is for a single layer of soil (tillage layer) and cannot be directly used in field tests.

[0075] In order to apply the penetration resistance mathematical model to the analysis of tillage depth in the field, step (3) specifically includes:

[0076] (3.1) The Plackett-Burman test was used to screen the factors that significantly affect the resistance value among the 20 parameters of the tillage layer and the plow bottom layer, and the probe penetration simulation test was carried out using EDEM simulation software. The simulation model described is the Hertz-Mindlin with JKR bonding model. The soil particle radius is set between 0.5 mm and 1.5 mm, the tillage layer is 50 mm high, the plow bottom layer is 80 mm high, and the number of particles is 3×10 4 and 5×10 4 The probe penetration speed is 8 mm / s and the penetration depth is 50 mm. In order to shorten the simulation time, preliminary experiments show that the barrel diameter can be reduced to 80 mm and the particles will not be affected by the barrel wall.

[0077] Table 1 Simulation parameter value range

[0078]

[0079] (3.2) Using Design Expert software, the variance analysis of the Plackett-Burman test was performed, and it was found that the only factors that significantly affect the resistance at the boundary between the plow layer and the plow bottom layer are the shear modulus of the plow layer and the shear modulus of the plow bottom layer, with the influence ratio of the two being approximately 3:17.

[0080] Table 2 Significance analysis of Plackett-Burman test parameters

[0081]

[0082]

[0083] Note: P < 0.01 (extremely significant, **); P < 0.05 (significant, *)

[0084] (3.3) During the test, it was discovered that the probe's penetration disturbed the soil, causing it to move at a certain speed. The soil particles were considered disturbed by the probe if their speed was greater than or equal to 2 mm / s. When the disturbed area approached the plow bottom layer, the penetration resistance began to increase significantly.

[0085] like Figure 3 As shown, the tillage layer depth is 50 mm; Figure 3 The shear modulus of the tillage layer shown in (a) is 1 MPa. Figure 3 The shear modulus of the plow layer shown in (b) is 10 MPa. △h1 represents the distance between the probe and the plow bottom layer, and also represents the depth of soil disturbance below the probe tip. △h2 represents the distance between the probe and the plow bottom layer when the penetration resistance begins to rise due to the influence of the plow bottom layer. The experiment found that △h1 is approximately equal to △h2, indicating that the change in probe resistance is related to the change in the soil disturbance area and the shear modulus of the plow layer.

[0086] Furthermore, the influence depth method for determining tillage depth specifically includes the following steps:

[0087] (5.1) The shear modulus of the tillage layer is set to 1MPa-50MPa and divided into four levels for single factor analysis of △h1. The simulation is performed using EDEM software. The soil particle radius is between 0.5mm and 1.5mm, the barrel diameter is still 80mm, and the number of particles is 8x10 4 The probe penetration speed is 8mm / s. Only the shear modulus of the tillage layer is changed, and other factors are fixed. The total simulation time is 4S. The influence area at the 4th second is taken, and the simulation results are as follows: Figure 4 .

[0088] Table 3 Simulation parameter values

[0089]

[0090] (5.2) Fitting the shear modulus value with the impact depth value, the relationship between △h1 and the shear modulus of the plow layer is as follows:

[0091]

[0092] Where △h1 is the impact depth, unit is mm; G1 is the shear modulus of the plow layer, unit is Pa.

[0093] (5.3) Conduct field tests, measure the soil parameters of the tillage layer, and then insert them into the mathematical model formula (2) of the penetration resistance. According to the calculation results, the obtained penetration resistance is used as the vertical coordinate, and the displacement (i.e., penetration depth) is used as the horizontal coordinate. A resistance model curve of penetration resistance-penetration depth is drawn and compared with the penetration resistance-penetration depth curve results measured in the field test. Before the penetration resistance of the field test begins to increase significantly, the depth corresponding to the minimum difference in resistance between the two is the depth of the probe when the affected area approaches the plow bottom layer. This depth is summed with △h1, and the result obtained is the tillage layer depth obtained by the influence depth method.

[0094] The specific steps of further layered line method to determine tillage depth include:

[0095] (6.1) The ratio of the shear modulus influence of the tillage layer and the plow layer is 3:17. The individual influence rates of the two are 15% and 85%, respectively. A stratification line is defined to represent the resistance value at the interface affected by the shear modulus of the tillage layer and the plow layer at different tillage depths. The penetration resistance mathematical model used for this stratification line is consistent with the penetration resistance mathematical model of the plow layer. The shear modulus of the stratification line is set to G λ , replace the soil shear modulus G in formula (2) to calculate the penetration resistance, G λ It is determined simultaneously by the shear modulus of the plow layer and the plow bottom layer.

[0096] G λ =15%G1+85%G2 (4)

[0097] Where G1 is the shear modulus of the plow layer, in Pa; G2 is the shear modulus of the plow bottom layer, in Pa.

[0098] (6.2) Conduct field tests to measure probe penetration depth, penetration resistance, plow layer shear modulus, plow bottom layer shear model and plow layer soil parameters. λ The soil parameter values ​​of the plough layer are substituted into the penetration resistance mathematical model of formula (2). The stratification line is drawn according to the calculation results. At the same time, the penetration depth and penetration resistance of the field test are used to draw the field test curve. The intersection of the stratification line and the field test curve is the measured tillage depth of the stratification line method.

[0099] Because of G λ Instead of the shear modulus G of the tillage layer, the shear modulus becomes larger, and the resistance values ​​at different depths calculated also become larger. The obtained curve will intersect with the curve of the field test, such as Figure 5 As shown: Figure 5 The shear modulus of the plow layer in (a) is the same. The shear modulus of the plow layer in test 1 is 1 MPa, corresponding to delamination line 1, and the shear modulus of the plow layer in test 2 is 5 MPa, corresponding to delamination line 2; Figure 5(b) is the resistance curve from the displacement of 60mm to the plow bottom layer. The shear modulus of the plow bottom layer is the same. The shear modulus of the plow bottom layer in test 1 is 50MPa, and the shear modulus of the plow bottom layer in test 2 is 100MPa, corresponding to delamination lines 1 and 2 respectively. Figure 5 It can be seen that no matter the shear modulus of the plow layer or the plow bottom layer changes, the delamination line will change with the change of the shear modulus and the intersection point with the actual test.

[0100] The present invention uses the soil of Lingou Village in Mengjin, Henan Province as the test object, conducts field tests, and uses the above-mentioned influence depth method and layering line method to measure the tillage depth.

[0101] The soil texture is silt clay loam as measured by a hydrometer method.

[0102] Figure 6 The figure shows the plowing depth detection vehicle used in the test. The six probes on the vehicle can measure the penetration resistance of a soil section at a time. The five-point method is used to detect the plowing depth of the soil after plowing, and the soil parameters of the plow layer and the plow bottom layer are measured. The parameters at one of the sections are taken as an example for explanation.

[0103] Table 4 Field soil parameters

[0104]

[0105] The penetration resistance and penetration depth data of one of the probes in the section are exported.

[0106] Substituting the shear modulus of the plow layer and the plow bottom layer into formula (4) yields the G used in the layered line method. λ , and the penetration depth and G λ , and the soil parameter values ​​of the tillage layer are substituted into the penetration resistance mathematical model formula (2) to obtain the stratification line (i.e., the resistance-displacement curve obtained by the stratification line method). At the same time, the penetration resistance-penetration depth measured in the field test is plotted as the field test curve. The intersection of the stratification line and the field test is the measured tillage depth of the stratification line method, which is 121.40 mm.

[0107] At the same time, according to the value of the shear modulus of the tillage layer, the influence depth △h1 is obtained from formula (3) to be 24.04mm. The tillage layer soil parameters measured in the field test are substituted into formula (2) to calculate the penetration resistance. The depth corresponding to the intersection of the resistance model (i.e., the calculated penetration resistance-penetration depth curve) and the field test is added to the influence depth △h1, which is the measured tillage depth of 129.14mm using the influence depth method. Figure 7 shown.

[0108] During the field experiment, the tillage depth measured by the tillage depth measuring ruler was Figure 7The actual tillage depth in the experiment is 132 mm, which shows that the tillage depth discrimination method based on the resistance model proposed in the present invention has high accuracy and reliable measurement results.

[0109] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for determining tillage depth based on penetration resistance, characterized in that: The following steps are involved: (1) Using the spherical pore expansion theory, a spherical pore expansion model of unsaturated soil is established to obtain the pore expansion pressure; (2) Conduct indoor soil trench tests to solve the relationship between hole expansion pressure and penetration resistance, and obtain a mathematical model of the penetration resistance of the plow layer, including: (2.1) Conduct an indoor soil trough test using a probe, a universal testing machine, and a bucket containing the test soil. The indoor test described in (2.2) set the soil moisture content range to 10% to 20%, divided into three levels: 10%, 15%, and 20%, and the soil density range was set to 1.1×10 3 kg / m 3 ~1.3×10 3 kg / m 3 , also divided into three levels: 1.1×10 3 kg / m 3 , 1.2×10 3 kg / m 3 , 1.3×10 3 kg / m 3 , do orthogonal test; (2.3) Soil parameters at moisture contents of 10%, 15%, and 20% were measured using direct shear tests and soil sample crush tests. The results were substituted into the calculation formula for hole expansion pressure. Analysis revealed that, at different moisture contents and densities, the following relationship exists between hole expansion pressure and penetration resistance. The mathematical model for penetration resistance is: Where q c is the penetration resistance; p a is the expansion pressure; r is the cone head radius; h is the penetration depth, γ is the soil bulk density, and μ is the soil Poisson's ratio; (3) Conduct probe penetration simulation tests using EDEM simulation software, and analyze the disturbance effect of the probe on the soil, as well as the significant influencing factors and influencing rates of penetration resistance based on the simulation test results; (4) Based on the analysis results of step (3), define the influence depth method or the layered line method to determine the tillage depth; The simulation test of step (3) shows that the change of probe resistance is related to the change of soil disturbance area and the shear modulus of the tillage layer. The specific steps of the influence depth method to determine the tillage depth are as follows: △h1 represents the distance between the probe and the plow bottom layer, i.e., the influence depth. The shear modulus G1 of the plow layer is set in the range of 1MPa-50MPa and divided into four levels for single factor analysis. EDEM software is used for simulation. Based on the simulation data, the shear modulus value of the plow layer is fitted with the influence depth value. The relationship between the distance △h1 between the probe and the plow bottom layer and the shear modulus of the plow layer is obtained as follows: Where, △h1 is the impact depth; G1 is the shear modulus of the plow layer; A field test was conducted to measure soil parameters and the probe penetration resistance and penetration depth. On the one hand, the measured tillage layer soil parameters were substituted into the penetration resistance mathematical model obtained in step (2), and the penetration resistance model curve was drawn according to the calculation results. The influence depth was calculated according to the relationship between △h1 and the shear modulus of the tillage layer. On the other hand, the penetration resistance measured in the field test was drawn into a field test curve, and the two curves were compared together. Before the penetration resistance of the field test curve began to increase significantly, the displacement corresponding to the minimum difference in resistance between the two was the depth of the probe when the soil influence area approached the plow bottom layer. This depth was summed with △h1, and the result obtained was the tillage layer depth measured by the influence depth method.

2. The method for determining tillage depth based on penetration resistance according to claim 1, wherein: In step (1), the stress field, strain field and displacement field in the elastic-plastic zone are derived and analyzed according to the spherical hole expansion theory to obtain the probe expansion pressure, that is, the soil is expanded from radius a0 to a u The pressure required: in: s v0 =gγh Where p a is the hole expansion pressure; c is the soil cohesion; is the internal friction angle of soil; b is a parameter characterizing the effect of intermediate principal stress, with a value range of 0 to 1; m is the intermediate principal stress parameter, m≤1 under plane strain conditions, and m→1 when the soil enters the plastic state; K0 is the soil lateral pressure coefficient; σ v0 is the vertical stress of soil; g is the acceleration of gravity; γ is the bulk density of soil; h is the penetration depth; G is the shear modulus of soil.

3. The method for determining tillage depth based on penetration resistance according to claim 1, wherein: Step (3) is specifically as follows: using the Plackett-Burman test to screen the parameters of the plow layer and the plow bottom layer that have a significant impact on the penetration resistance value, and using the EDEM simulation software to perform a probe penetration simulation test, and using the Design Expert software to perform a variance analysis on the Plackett-Burman test. It is concluded that the only factors that have a significant impact on the penetration resistance at the dividing point between the plow layer and the plow bottom layer are the plow layer shear modulus and the plow bottom layer shear modulus, and the influence ratio of the two is 3:

17.

4. The method for determining tillage depth based on penetration resistance according to claim 2, wherein: The specific steps of the layering line method for determining tillage depth are as follows: define a layering line, which represents the resistance value at the interface affected by the shear modulus of the tillage layer and the plow bottom layer at different tillage depths. The model used for the layering line is consistent with the mathematical model of the penetration resistance of the tillage layer. The ratio of the shear modulus influence rate of the tillage layer and the plow bottom layer is 3:17, and the individual influence rates of the two are 15% and 85%, respectively. Set the shear modulus of the layering line to G λ , determined simultaneously by the shear modulus of the plow layer and the plow bottom layer: G λ =15%G1+85%G2, where G1 is the shear modulus of the plow layer; G2 is the shear modulus of the plow bottom layer; Field tests were conducted to measure the probe penetration depth, penetration resistance, plow layer shear modulus, plow bottom layer shear model and plow layer soil parameters. The layered linear shear modulus G was used. λ Instead of soil shear modulus G, penetration resistance is calculated. According to the relationship between hole expansion pressure and penetration resistance, penetration depth, G λ The soil parameter values ​​of the tillage layer are substituted into the penetration resistance mathematical model in step (2). The stratification line is drawn according to the calculation results. At the same time, the penetration depth and penetration resistance of the field test are plotted into a field test curve. The intersection of the stratification line and the field test curve is the measured tillage depth of the stratification line method.

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