CN116359277A - Method for in-situ monitoring of volume weight of non-rigid soil - Google Patents

Abstract

The invention relates to a method for in-situ monitoring of the volume weight of non-rigid soil, which aims at the problems of increased contact thermal resistance, field temperature drift and the like generated in the expansion and contraction process of the non-rigid soil, adopts brand new design, and on the principle of a thermal pulse-time domain reflection technology, utilizes a soil thermal pulse probe and a soil moisture probe to fill up the technical blank of long-term in-situ monitoring of the volume weight dynamics of the soil by a plurality of probes, determines the volume weight value of the non-rigid soil according to a design model based on the acquisition of the soil thermal conductivity value and the soil volume moisture content value, and adopts high-thermal conductivity silicone grease to improve the thermal contact between the soil thermal pulse probe and the soil aiming at the soil thermal pulse probe, thereby overcoming the defect of increased volume weight prediction error caused by the cracking of the non-rigid soil in the traditional method; the volume weight prediction deviation under different weather conditions caused by ambient temperature drift during field monitoring is corrected by a linear extrapolation method; the method is improved and optimized, is easy to operate and implement under field conditions, improves the accuracy of in-situ monitoring of the volume weight of the non-rigid soil, and has popularization significance.

Description

A method for in-situ monitoring of non-rigid soil bulk density

technical field

The invention relates to a method for in-situ monitoring of non-rigid soil bulk density, and belongs to the technical field of soil physical property measurement.

Background technique

Soil bulk density is one of the most commonly used indicators to characterize soil structure, and plays an important role in regulating soil moisture transport and crop growth. At present, the dynamic change of soil bulk density is mainly obtained through the method of sampling at intervals in the field, which is time-consuming and laborious, and the continuous dynamic process of soil structure cannot be obtained.

Thermal pulse-time domain reflectometry (Thermo-TDR) can use the synchronously acquired soil thermal characteristics and water content to reverse the soil bulk density and realize continuous monitoring of soil bulk density. However, at present, the thermal pulse-time domain reflectometry technology has not yet been applied commercially, and the manufacturing process of self-made probes is complex, and there are some uncertainties between the probes, which limit the wide application of this technology. Studies have combined commercial soil moisture and heat pulse probes to achieve accurate bulk density measurements in different rigid soil types, further improving the application prospects of this technology.

However, for the non-rigid soil rich in expansive clay minerals, the severe contraction of the soil not only caused the obvious deformation of the probe itself, but also the gradual development of soil cracks during the dehydration process. The air gap formed between the probe and the soil significantly increases the contact thermal resistance of the soil, which leads to a large error in the prediction of the bulk density. In the process of field monitoring, the prediction of bulk density has more uncertainties. For example, in addition to the pulse heating process, the determination of soil thermal properties in the field is more susceptible to the influence of solar radiation and ambient temperature drift, resulting in bulk density between day and night or under different weather conditions. large deviation from the forecast. Therefore, it is urgent to develop an accurate, convenient and easy-to-promote non-rigid soil bulk density in-situ monitoring method to fill the technical gap in monitoring soil bulk density dynamics with multiple probes.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for in-situ monitoring of non-rigid soil bulk density. Aiming at problems such as increased contact thermal resistance and field temperature drift caused by non-rigid soil expansion and contraction, a new design can be used to efficiently and accurately measure Dynamic changes in bulk density of non-rigid soils.

In order to solve the above technical problems, the present invention adopts the following technical solutions: the present invention designs a method for in-situ monitoring of non-rigid soil bulk density, based on the measurement of the thermal conductivity and volume content of the target non-rigid soil by the soil heat pulse probe and the soil moisture probe. For the simultaneous detection of the amount of water, the following steps A to C are performed to realize the detection of the soil bulk density value ρ _b of the target non-rigid soil;

Step A. Based on the probe sensitivity S of the soil heat pulse probe, the length L of the heating wire in the soil heat pulse probe, the resistance R of the heating wire in the soil heat pulse probe, and the voltage U _heater at both ends of the heating wire in the soil heat pulse probe , and the probe output voltage U ₀ and U ₁ before and after heating corresponding to the preset probe heating time of the soil heat pulse probe to obtain the soil thermal conductivity value λ of the target non-rigid soil, and then enter step B;

Step B. According to the soil dielectric constant Eb of the target non-rigid soil obtained by the soil moisture probe, the soil volumetric water content value θ _v of the target non-rigid soil is obtained, and then enter step C;

Step C. According to the soil thermal conductivity value λ and soil volumetric water content value θ _v of the target non-rigid soil, aim at the following model:

Iterative calculation to obtain the total soil porosity φ of the target non-rigid soil and the soil bulk density value ρ _b of the target non-rigid soil, where α=0.67f _clay +0.24, β=1.97f _sand +1.87ρ _b -1.36f _sand ρ _b -0.95, f _sand and f _clay represent the sand and clay content of the target non-rigid soil, respectively, and λ _dry represents the thermal conductivity of dry soil.

As a preferred technical solution of the present invention: in the step A, based on the probe sensitivity S of the soil heat pulse probe, the heating wire length L in the soil heat pulse probe, the heating wire resistance R in the soil heat pulse probe, The voltage U _heater at both ends of the heating wire in the soil heat pulse probe, and the output voltages U ₀ and U ₁ of the probe before and after heating corresponding to the preset probe heating time of the soil heat pulse probe are as follows:

Obtain the soil thermal conductivity value λ of the target non-rigid soil, where S represents the probe sensitivity of the soil thermal pulse probe, Q represents the electric power of the heating wire per meter in the soil thermal pulse probe, and ΔU represents the difference between U ₁ and U ₀ The difference between, and then go to step B.

As a preferred technical solution of the present invention: in the step B, according to the soil dielectric constant Eb of the target non-rigid soil obtained by the soil moisture probe, according to the following formula:

θ _v =4.3×10 ^-6 ×Eb ³ -5.5×10 ^-4 ×Eb ² +2.92×10 ^-2 ×Eb-5.3×10 ^-2

Obtain the soil volume moisture content value θ _v of the target non-rigid soil, and then enter step C.

As a preferred technical solution of the present invention: In the step A, regarding the detection of the target non-rigid soil by the soil heat pulse probe, the detection data of the preset daytime time period is eliminated, and then according to the detection data of the preset nighttime time period, Execute the step A to obtain the soil thermal conductivity value λ of the target non-rigid soil.

As a preferred technical solution of the present invention: in the step A, regarding the detection of the target non-rigid soil by the soil heat pulse probe, for the preset night time period detection data, according to the following linear extrapolation formula:

U ₀ (t)=at+b

Fitting to obtain the trend equation U ₀ (t) of the output voltage of the soil heat pulse probe corresponding to the change of the probe output voltage with time (t) before heating, that is, to correct the influence of the ambient background temperature on the detection data during the monitoring process of the preset night time period, and then According to where at, update U ₁ with the result of U ₁ -at, update and obtain the corrected probe output voltage U ₁ after the heating time of the soil heat pulse probe corresponding to the preset probe heating time, where a and b represent the equation fitting parameters .

As a preferred technical solution of the present invention: before the soil moisture probe detects the target non-rigid soil, the measured value of the soil ring knife sample is obtained by applying the soil moisture probe and the drying method respectively, and the difference between the two is obtained. The linear relationship is used to subsequently correct the error of the soil moisture probe for the detection of the target non-rigid soil.

As a preferred technical solution of the present invention: in the step A, based on the acquisition of the soil thermal conductivity value λ of the target non-rigid soil, further according to K=K _reference ×T _reference /T, the soil of the target non-rigid soil is obtained The thermal diffusivity K, and then according to C=λ/K, the soil volumetric heat capacity C of the target non-rigid soil is obtained; where, K _reference represents the thermal diffusivity of the standard reference agar gel at 20°C, and T _reference represents the condition at 20°C The time required for the output voltage to drop to 37% of ΔU after heating the standard reference agar gel, ΔU represents the difference between U ₁ and U ₀ , T represents the heating time of the soil heat pulse probe corresponding to the preset probe After heating, the response time for the probe output voltage to decrease to 37% of ΔU.

As a preferred technical solution of the present invention: before using the soil heat pulse probe to detect the target non-rigid soil, use high thermal conductivity silicone grease to smear the surface of the soil heat pulse probe foil, and because the heat pulse probe can accurately measure the soil heat Due to the influence of the spatial range of the characteristics (radius 4mm), the thickness of the high thermal conductivity silicone grease should not exceed 1mm.

A method for in-situ monitoring of non-rigid soil bulk density described in the present invention, compared with the prior art by adopting the above technical scheme, has the following technical effects:

(1) The present invention designs a method for in-situ monitoring of non-rigid soil bulk density. Aiming at problems such as increased contact thermal resistance and field temperature drift caused by non-rigid soil expansion and contraction, a new design is adopted. In the thermal pulse-time domain In principle, the reflection technology uses soil heat pulse probes and soil moisture probes to fill in the technical gaps in the long-term in-situ monitoring of soil bulk density dynamics with multiple probes. The model determines the soil bulk density value of non-rigid soil, and for the soil thermal pulse probe, uses high thermal conductivity silicone grease to improve the thermal contact between the soil thermal pulse probe and the soil, which overcomes the bulk density prediction error caused by the cracking of non-rigid soil in the original method The shortcomings of the increase; and the linear extrapolation method in the design corrected the deviation of the bulk density prediction under different weather conditions caused by the ambient temperature drift during field monitoring; the entire design method can realize the accuracy of the non-rigid soil bulk density under indoor and field conditions predict.

Description of drawings

Figures 1a, 1b, and 1c are schematic diagrams of the structure of TP01 thermal pulse probe and 5TE moisture probe connected to CR3000 data collector;

Figure 2 is the relationship between the θ _v value measured by the 5TE soil moisture probe and the drying θ _v ;

Figure 3 is the relationship between daytime and nighttime monitoring data and ambient temperature before and after correction;

Figure 4 is the relationship between the predicted value of bulk density and the measured value.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The present invention designs a method for in-situ monitoring of non-rigid soil bulk density. In practical applications, firstly, before the soil moisture probe detects the target non-rigid soil, the soil moisture probe and the drying method are used to obtain the soil ring knife sample respectively. Measure the value and obtain the linear relationship between the two, which is used to correct the error of the soil moisture probe for the target non-rigid soil detection. Specifically, the soil moisture probe is inserted into the PVC ring knife using a series of bulk density gradients and water content gradients The measurement is carried out in the sample. The size of the ring knife sample is required to be larger than the spatial measurement range of the moisture probe, and the material of the ring knife should not affect the measurement of the soil dielectric constant. After the measurement is completed, the PVC sample is dried at 105°C to constant weight. The linear relationship between the measured values is corrected for the error of the moisture probe, as shown in Figure 2.

And before using the soil heat pulse probe to detect the target non-rigid soil, use high thermal conductivity silicone grease to smear the surface of the soil heat pulse probe foil, and in the specific implementation, because the heat pulse probe accurately measures the spatial range of the soil thermal characteristics (radius 4mm), the thickness of the high thermal conductivity silicone grease should not exceed 1mm; because the high thermal conductivity silicone grease is selected with a thermal conductivity of 14.8WmK ^-1 , a thermal resistance <0.0028°CW ^-1 , a density greater than 2.6gcm ^-3 , and a viscosity greater than 2500poise insulating silicone grease, evenly and thinly applied to the surface of the soil heat pulse probe foil, can reduce the contact thermal resistance between the soil and the probe after the non-rigid soil loses water and cracks.

Probe installation is performed as follows.

(1) For the indoor soil column experiment, first fill the soil column to half the height, place the TP01 probe foil on the soil surface and ensure good contact, and then fill the other half of the soil column to the target height. During the filling process, the soil column is pressed layer by layer to ensure that the probe foil is in good contact with the upper and lower soil layers.

(2) For in-situ monitoring of different soil layers in the field, use a blade to draw a gap in the soil layer before installation, carefully insert the probe foil coated with high thermal conductivity silicone grease, and use wet soil to seal the probe base Fix it well to prevent it from falling off when filling the soil. After the landfill is installed, pour water on the surface 1-2 times to make the soil layer solid, so as to achieve the purpose of full contact between the soil and the probe.

Then, based on the simultaneous detection of the thermal conductivity and volumetric water content of the target non-rigid soil by the soil heat pulse probe and the soil moisture probe, the following steps A to C are performed to realize the detection of the soil bulk density value ρ _b of the target non-rigid soil .

Step A. Based on the probe sensitivity S of the soil heat pulse probe, the length L of the heating wire in the soil heat pulse probe, the resistance R of the heating wire in the soil heat pulse probe, and the voltage U _heater at both ends of the heating wire in the soil heat pulse probe , and the probe output voltage U ₀ and U ₁ of the soil heat pulse probe corresponding to the preset probe heating time before and after heating, according to the following formula:

Obtain the soil thermal conductivity value λ of the target non-rigid soil, where S represents the probe sensitivity of the soil thermal pulse probe, Q represents the electric power of the heating wire per meter in the soil thermal pulse probe, and ΔU represents the difference between U ₁ and U ₀ The difference between, and then go to step B.

In practical applications, in step A, regarding the detection process of the target non-rigid soil by the soil heat pulse probe, the further design first eliminates the detection data of the preset daytime time period, and then for the detection data of the preset nighttime time period, according to the following linear formula Inference formula:

U ₀ (t)=at+b

Fitting to obtain the trend equation U ₀ (t) of the output voltage of the soil heat pulse probe corresponding to the change of the probe output voltage with time (t) before heating, that is, to correct the influence of the ambient background temperature on the detection data during the monitoring process of the preset night time period, such as As shown in Fig. 3, U 1 is updated according to the result of at, U ₁ -at, and the output voltage _{U 1 of} the corrected probe after heating is obtained by updating the soil heat pulse probe corresponding to the preset probe heating time, and finally executes the Step A, obtaining the soil thermal conductivity value λ of the target non-rigid soil, where a and b represent equation fitting parameters.

The above-mentioned detection and verification of the target non-rigid soil by the soil heat pulse probe is specifically based on the trend equation of the change of the soil background temperature (T ₀ ) with time (t) before heating:

T ₀ =at+b

Subtracting the change of soil background temperature from the temperature of the thermal pulse induction needle (T _v ) during the heating process, the temperature change of the induction needle under the single action of pulse heating (T _c ) is obtained, and then the thermal characteristics of the soil are obtained by fitting:

T _c =T _v -at

Since the TP01 heat pulse probe in this patent converts the soil temperature change (ΔT) into a small voltage output value (ΔU), the change trend equation of T _v (t) is transformed into:

U ₀ (t)=at+b

Transform the T _c (t) equation into the U ₁₈₀ (t) equation:

U ₁ (t) = U ₁ -at

In the actual application implementation, based on the acquisition of the soil thermal conductivity value λ of the target non-rigid soil, the further design is based on K=K _reference ×T _reference /T to obtain the soil thermal diffusivity K of the target non-rigid soil, and then according to C= λ/K, to obtain the soil volumetric heat capacity C of the target non-rigid soil; where, K _reference represents the thermal diffusivity of the standard reference agar gel at 20°C, usually 0.14×10 ^-6 m ² s ^-1 , T _reference Indicates the time required for the output voltage to drop to 37% of ΔU after the standard reference agar gel is heated at 20°C, usually 19s, ΔU represents the difference between U ₁ and U ₀ , T represents the soil heat pulse probe Aiming at the preset heating time of the probe, it is the response time when the output voltage of the probe drops to 37% of ΔU after heating.

Step B. According to the soil dielectric constant Eb of the target non-rigid soil obtained by the soil moisture probe, according to the following formula:

θ _v =4.3×10 ^-6 ×Eb ³ -5.5×10 ^-4 ×Eb ² +2.92×10 ^-2 ×Eb-5.3×10 ^-2

Obtain the soil volume moisture content value θ _v of the target non-rigid soil, and then enter step C.

In practical applications, the linear relationship between the initial soil moisture probe and the measured values of the soil ring knife sample obtained by the drying method is used here to correct the error of the soil moisture probe in the detection of the target non-rigid soil.

Step C. According to the soil thermal conductivity value λ and soil volumetric water content value θ _v of the target non-rigid soil, aim at the following model:

Iterative calculation to obtain the total soil porosity φ of the target non-rigid soil and the soil bulk density value ρ _b of the target non-rigid soil, where α=0.67f _clay +0.24, β=1.97f _sand +1.87ρ _b -1.36f _sand ρ _b -0.95, f _sand and f _clay represent the sand and clay content of the target non-rigid soil, respectively, and λ _dry represents the thermal conductivity of dry soil.

Applying the above design to practice, the soil thermal pulse probe adopts the TP01 thermal pulse probe of Hukseflux Company, as shown in Fig. 1a, which is used for long-term monitoring of soil thermal characteristic values. 60mm, thickness 0.15mm). The heating wire is located on the central axis of the foil, and there is a thermopile probe at 4 mm on both sides, and the two thermopile probes are connected in series.

The soil moisture probe is used to measure the volumetric water content of the soil. Commonly used moisture probes such as TDR100, 5TE, EC-5, 315H, etc. can be used. Specifically, the 5TE soil moisture probe of METER company is used, as shown in Figure 1b. The probe Using frequency domain reflectometry (FDR), the apparent dielectric constant of the soil was measured according to the propagation frequency of electromagnetic waves in the soil, and then the volumetric water content of the soil (θ _v , cm ³ cm ^-3 ) was obtained.

In actual application, in the implementation of the above steps A to C, the data collector is used to connect with the soil heat pulse probe and the soil moisture probe respectively to obtain the soil thermal characteristics and soil water content values synchronously. In specific applications, use Campbell company CR series data collector, when the data collector is used indoors, the data collector is powered by a 12v voltage regulator; when it is used in the field, install a 12v battery and solar panel, the design here specifically uses the Campbell company CR3000 data collector , as shown in Figure 1c. The data collector is respectively connected with the TP01 soil thermal pulse probe and the 5TE moisture probe for synchronous acquisition of soil thermal characteristics and soil moisture content.

Further use LoggerNet software to write a control program, which is used to control the simultaneous calculation and output of the heating time, measurement interval, soil thermal characteristic value and soil volumetric water content value of the thermal pulse probe.

In practical applications, the positive pole of the TP01 probe heating wire power line is connected in series with the 150Ω resistor and then connected to the switch excitation channel (SW12V), and the negative pole is grounded; the positive and negative poles of the thermopile signal line are connected to a pair of differential ports; the positive pole of the heater voltage output line is connected to The differential ports are connected, the negative pole is grounded; the ground wire is grounded. Each TP01 probe occupies 1.5 pairs of differential channels; the positive and negative poles of the 5TE soil moisture probe power line are connected to the switch excitation channel; the data signal line is connected to the single end. Since the connector of the moisture probe is a 3.5mm cylindrical earphone interface, in order not to damage the structure of the probe itself, a corresponding size connector is added to connect the data collector, as shown in Figure 1c.

In actual operation, regarding the above-mentioned design steps A to C, the set time interval starts the program every 3 hours. When the program starts, heat the heating wire for 180s to generate a stable radial temperature difference around it, and then perform the following steps A to C based on the simultaneous detection of the target non-rigid soil by the soil heat pulse probe and the soil moisture probe, The relationship between the predicted value of bulk density and the measured value is shown in Figure 4.

The method of in-situ monitoring of non-rigid soil bulk density designed by the above technical scheme adopts a new design for the problems of increased contact thermal resistance and field temperature drift caused by the expansion and contraction of non-rigid soil. Based on the principle of thermal pulse-time domain reflection technology , use the soil heat pulse probe and soil moisture probe to fill the technical gap of long-term in-situ monitoring of soil bulk density dynamics with multiple probes, based on the acquisition of soil thermal conductivity and soil volumetric water content, the non-rigid The soil bulk density value of the soil, and for the soil thermal pulse probe, high thermal conductivity silicone grease is used to improve the thermal contact between the soil thermal pulse probe and the soil, which overcomes the shortcomings of the original method of increasing the bulk density prediction error due to non-rigid soil cracking ; and the linear extrapolation method in the design corrected the bulk density prediction deviation under different weather conditions caused by ambient temperature drift during field monitoring; the entire design method can realize accurate prediction of non-rigid soil bulk density under indoor and field conditions.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and can also be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. Variations.

Claims (8)

1. A method for in-situ monitoring of the volume weight of non-rigid soil, which is characterized in that: based on the simultaneous detection of the thermal conductivity and the volumetric water content of the target non-rigid soil by the soil heat pulse probe and the soil moisture probe, the following steps A to C are executed to realize the soil volume weight value rho of the target non-rigid soil _b Is detected;

step A. Based on the probe sensitivity S of the soil heat pulse probe, the length L of the heating wire in the soil heat pulse probe, the resistance R of the heating wire in the soil heat pulse probe, and the voltage U at two ends of the heating wire in the soil heat pulse probe _heater The output voltage U of the probe before and after the heating of the soil heat pulse probe corresponding to the preset heating time of the probe ₀ And U ₁ Obtaining a soil heat conductivity value lambda of target non-rigid soil, and then entering a step B;

step B, obtaining the soil volume moisture value theta of the target non-rigid soil according to the soil dielectric constant Eb of the target non-rigid soil obtained by the soil moisture probe _v ThenEntering a step C;

step C, according to the soil thermal conductivity value lambda and soil volume moisture content value theta of the target non-rigid soil _v For the following model:

iterative calculation to obtain soil total porosity phi of target non-rigid soil and soil volume weight value rho of target non-rigid soil _b Wherein α=0.67 f _clay +0.24，β＝1.97f _sand +1.87ρ _b -1.36f _sand ρ _b -0.95，f _sand And f _clay Respectively representing sand grain and clay grain content, lambda of target non-rigid soil _dary Indicating the dry soil thermal conductivity.

2. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: in the step A, the probe sensitivity S based on the soil heat pulse probe, the length L of the heating wire in the soil heat pulse probe, the resistance R of the heating wire in the soil heat pulse probe and the voltage U at two ends of the heating wire in the soil heat pulse probe are adopted _heater The output voltage U of the probe before and after the heating of the soil heat pulse probe corresponding to the preset heating time of the probe ₀ And U ₁ The following formula is adopted:

obtaining a soil thermal conductivity value lambda of the target non-rigid soil, wherein S represents the probe sensitivity of the soil heat pulse probe, Q represents the electric power of each meter of heating wire in the soil heat pulse probe, and DeltaU represents U ₁ And U ₀ The difference between them, and then step B is entered.

3. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: in the step B, according to the soil dielectric constant Eb of the target non-rigid soil obtained by the soil moisture probe, the following formula is adopted:

θ _v ＝4.3×10 ^-6 ×Eb ³ -5.5×10 ^-4 ×Eb ² +2.92×10 ^-2 ×Eb-5.3×10 ^-2

obtaining the soil volume moisture value theta of the target non-rigid soil _v Then step C is entered.

4. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: and (C) detecting the target non-rigid soil by the soil heat pulse probe in the step A, removing detection data of a preset daytime period, and executing the step A according to the detection data of the preset nighttime period to obtain a soil heat conductivity value lambda of the target non-rigid soil.

5. The method for in situ monitoring of the volume weight of non-rigid soil of claim 4, wherein: in the step A, with respect to the detection of the target non-rigid soil by the soil heat pulse probe, for detection data of a preset night time period, the following linear extrapolation formula is adopted:

U ₀ (t)＝at+b

fitting to obtain a trend equation U of the output voltage of the soil heat pulse probe corresponding to the probe before heating along with the change of time (t) ₀ (t) correcting the influence of the ambient background temperature on the detection data in the monitoring process of the preset night time period, and applying U according to at ₁ Result update U of-at ₁ Updating and obtaining the output voltage U of the correction probe after the soil heat pulse probe is heated corresponding to the preset probe heating time length ₁ Wherein a, b represent equation fitting parameters.

6. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: before the soil moisture probe detects the target non-rigid soil, the soil moisture probe and the drying method are respectively applied to obtain the measured value of the soil cutting ring sample, and the linear relation between the measured value and the soil cutting ring sample is obtained for subsequently correcting the error of the soil moisture probe on the target non-rigid soil detection.

7. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: in the step a, based on the obtaining of the soil thermal conductivity value λ of the target non-rigid soil, the method further comprises the following steps of k=k _reference ×T _reference Obtaining the soil thermal diffusivity K of the target non-rigid soil, and further obtaining the soil volumetric heat capacity C of the target non-rigid soil according to C=lambda/K; wherein K is _reference Shows the thermal diffusivity of the standard reference agar gel at 20 ℃, T _reference Represents the time period required for the output voltage to drop to 37% of DeltaU after heating of a standard reference agar gel at 20 ℃, deltaU representing U ₁ And U ₀ And the difference value T represents the response time length of the probe output voltage reduced to 37% of DeltaU after the soil heat pulse probe is heated corresponding to the preset probe heating time length.

8. A method of in situ monitoring of non-rigid soil bulk density as claimed in claim 1 wherein: before the soil heat pulse probe is used for detecting the target non-rigid soil, the high-heat-conductivity silicone grease is smeared on the surface of the soil heat pulse probe foil, and the smearing thickness of the high-heat-conductivity silicone grease is not more than 1mm.

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