CN107966471B - In-situ testing device and testing method for soil thermal conductivity and geothermal gradient - Google Patents

Abstract

The application belongs to the field of geotechnical engineering, and relates to an in-situ testing device and a testing method for soil body thermal conductivity and geothermal gradient, which comprises a probe rod, a telescopic thermal probe rod and a probe head which are sequentially connected from top to bottom, wherein the telescopic thermal probe rod comprises a telescopic sleeve rod, an annular heat sensor, a heat wire source and a micro motor, the end of the telescopic sleeve rod is connected with the probe head, the other end of the telescopic sleeve rod is connected with the probe rod, the micro motor is provided with two or more than two micro motors, the two or more than two micro motors are uniformly arranged on the telescopic sleeve rod at intervals, the telescopic sleeve rod can be stretched under the power action of the micro motors, the annular heat sensor is provided with two or more than two annular heat sensors, the annular heat sensor is correspondingly arranged on the micro motors, and the heat wire source is arranged in the telescopic sleeve rod and combines geothermal gradient with thermal conductivity testing, so that surveying engineering is convenient, rapid, accurate and economical, and.

Description

In-situ testing device and testing method for soil thermal conductivity and geothermal gradient

technical field

The invention belongs to the field of geotechnical engineering, an in-situ test element and device capable of effectively and accurately obtaining basic engineering properties and thermodynamic properties of soil, and relates to a method for testing thermal conductivity and thermal gradient of soil by using a transient line heat source method. The invention relates to a segmented penetration in-situ testing device, in particular to an in-situ testing device and a testing method for soil thermal conductivity and geothermal gradient.

Background technique

The transient line heat source method is a transient temperature response based on the infinite medium pulse heating linear body to form a line heat source. By recording and fitting the relationship between the temperature rise and the response time of the probe, the thermal conductivity of the material is calculated by the formula. The experimental method can be used to solve the analysis of the thermodynamic properties of materials in thermal engineering. This method is developed from the hot wire method and the tropical method, and combines the advantages of the hot wire method and the tropical method, and gradually becomes a popular test method in thermodynamic performance testing.

Thermal conductivity is a very important parameter in geotechnical engineering, and it is the basis for determining the thermodynamic properties of shallow rock and soil. The thermal conductivity of the surface rock and soil not only determines the distribution form of the shallow ground temperature field, but also determines the core of the heat pump calculation power, which is a key factor affecting the investment and energy consumption of ground source heat pump projects. At present, the method used in the laboratory to test the thermodynamic properties of soil samples is mainly the transient line heat source method, which has a fast response speed and a relatively accurate test.

Geothermal gradient is also one of the very important parameters in geotechnical engineering, which determines the efficiency of shallow geothermal heat exchange and the penetration depth of geothermal wells. It is one of the key factors affecting the investment and energy consumption of geothermal pump projects. The current testing instruments are relatively cumbersome, with low testing efficiency and high economic cost.

SUMMARY OF THE INVENTION

Based on the method of measuring the thermal conductivity coefficient of soil by the transient line heat source method, the invention proposes a telescopic segmented thermal probe testing instrument, which combines the geothermal gradient and thermal conductivity testing, making the survey project convenient, fast, and reliable. Accurate and economical, it can provide fast, effective and low-cost test parameters for geothermal energy research and energy installation engineering design.

In order to achieve the above technical purpose, the present invention adopts a specific technical scheme as follows: an in-situ testing device for soil thermal conductivity and geothermal gradient, including a probe rod, a telescopic thermal probe rod and a probe connected in sequence from top to bottom; The thermal probe rod includes a telescopic sleeve rod, an annular heat sensor, a hot wire source and a micro motor; one end of the telescopic sleeve rod is connected to the probe, and the other end is connected to the probe rod; there are two or more micro motors, and two or more micro motors are spaced apart Evenly installed on the telescopic sleeve rod, the telescopic sleeve rod can expand and contract under the power of the micro motor; there are two or more annular thermal sensors, and the annular thermal sensor is correspondingly installed on the micro motor, and can be extended with the expansion and contraction of the telescopic sleeve rod Displacement occurs; the hot wire source is arranged in the telescopic sleeve rod, and one end of the hot wire source is connected to the probe, and the other end extends into the probe rod.

As an improved technical solution of the present invention, a data receiving module is also included, and the data receiving module is arranged at the tail end of the probe rod and is used for receiving the data detected by the annular thermal sensor.

As an improved technical solution of the present invention, the telescopic sleeve rod is made of titanium alloy stainless steel.

As an improved technical solution of the present invention, the probe rod is made of alloy steel.

As an improved technical solution of the present invention, the probe is made of alloy steel.

As an improved technical solution of the present invention, the probe has a conical structure, and the tip of the conical structure is arranged on the side away from the telescopic thermal probe.

As an improved technical solution of the present invention, the length variation range of the telescopic thermal probe rod is 1 m.

Another object of the present invention is to provide a test method for an in-situ testing device for soil thermal conductivity and geothermal gradient, comprising the following steps:

Step 1. Adjust the thermal expansion probe to make it at the shortest length; insert the probe into the soil at a constant speed;

Step 2. When the probe reaches the test depth, the micromotor controls the extension of the telescopic sleeve rod. For each extension of 20cm, a micromotor in the relatively uppermost position drives the annular thermal sensor corresponding to the micromotor to move with the telescopic sleeve rod until all the When all the annular thermal sensors are released, stop penetration;

Step 3: Keep still until the ground temperature of the probe and the soil is consistent, and the data receiving module receives the test data of the annular thermal sensor at this time;

Step 4: Start the hot wire source to heat the soil, set the heating time, and the annular thermal sensor detects the ground temperature of the heated soil; the data receiving module receives the temperature detected by the annular thermal sensor at this time;

Step 5: The external external data processing system processes the data received by the data receiving module in step 3 and the data received by the data receiving module in step 4, and obtains the thermal conductivity of soil bodies at different depths.

beneficial effect

The device of the present application is simple in structure, convenient in operation and high in test accuracy; by setting a telescopic thermal probe between the probe and the probe, the soil temperature and thermal conductivity of different depths can be measured in situ. Those skilled in the art cannot easily think of it; in addition, the present application adopts the cooperation of a micro motor, a ring thermal sensor and a data receiving module to achieve real-time and accurate measurement of soil temperature, and at the same time, it can also perform data collection, processing, and storage work by itself, so that each time The experimental test data is of reference value.

To sum up, the device of the present application effectively solves the lack of existing domestic in-situ testing instruments for soil thermodynamic properties, as well as the problems that the existing instruments are cumbersome, time-consuming, difficult to operate, and high cost.

Description of drawings

Fig. 1 is the structural representation of the device of the present application;

2 is a schematic diagram of the use process of the device of the present application;

Figure 3 is a cross-sectional view of a telescopic thermal probe;

Figure 4 is a schematic cross-sectional view of a telescopic thermal probe;

In the figure, 1, probe rod; 2, telescopic thermal probe rod; 3, probe; 4, annular thermal sensor; 5, hot wire source; 6, micro motor; 7, data receiving module; 8, micro motor force transmission device; 9. Telescopic sleeve.

Detailed ways

In the embodiment, the probe rod 1 , the telescopic thermal probe rod 2 , the probe 3 , the annular thermal sensor 4 , the hot wire source 5 , the micromotor 6 , the data receiving module 7 , the micromotor force transmission device 8 , and the telescopic sleeve rod 9 .

The present application is a segmented penetration in-situ test device for testing soil thermal conductivity and geothermal gradient using the transient line heat source method, specifically the in-situ soil thermal conductivity and geothermal gradient as shown in Figures 1-2. Bit test device,

It includes a probe rod, a telescopic thermal probe rod and a probe connected in sequence from top to bottom; the telescopic thermal probe rod includes a telescopic sleeve rod, an annular thermal sensor, a hot wire source and a micro motor; one end of the telescopic sleeve rod is connected to the probe, and the other end is connected to the Probe rod; there are two or more micro-motors, and the two or more micro-motors are installed on the telescopic sleeve rod evenly spaced, and the telescopic sleeve rod can expand and contract under the power of the micro-motor; there are two or more annular thermal sensors , the annular heat sensor is correspondingly installed on the micro motor, and can be displaced with the expansion and contraction of the telescopic sleeve; the heat source is set in the telescopic sleeve, and one end of the heat source is connected to the probe, and the other end extends into the probe.

Specifically, as shown in Figures 3-4, the telescopic thermal probe includes a telescopic sleeve, an annular thermal sensor, a hot wire source and a micromotor; one end of the telescopic sleeve is connected to the probe, and the other end is connected to the probe; the annular thermal sensor has two There are two or more (preferably five annular thermal sensors in this embodiment), and the annular thermal sensors are installed on the telescopic sleeve rod at even intervals; there are two or more micromotors (preferably five micromotors in this embodiment), The micro-motors are installed on the telescopic sleeve rod at even intervals, and the micro-motors are installed corresponding to the annular thermal sensor (the annular thermal sensor is installed on the micro-motor). It is connected to the telescopic sleeve rod; when the telescopic sleeve rod needs to be stretched, the micro motor acts on the telescopic sleeve rod to make the telescopic sleeve rod expand and contract, and the annular thermal sensor on the corresponding micro motor also moves; the heat source is located in the telescopic sleeve rod. In the sleeve rod, one end of the hot wire source is connected to the probe, and the other end extends into the probe rod. When the hot wire source heats the soil, the annular thermal sensors located at different positions of the telescopic sleeve rod can detect the temperature of the surrounding soil. , so that the telescopic thermal probe part can quickly and effectively test the thermal conductivity and geothermal gradient of the soil, providing a convenient and accurate test method for the indoor test of the thermodynamic properties of the soil, for the study of shallow heat flow, thermal energy The implementation of pile engineering is of great significance.

In order to obtain data quickly and in time, a data receiving module is also included. The data receiving module is arranged at the end of the probe rod for receiving the data detected by the annular thermal sensor.

In order to ensure the accuracy of the test and the service life of the device, the telescopic sleeve rod is made of titanium alloy stainless steel.

In order to ensure the accuracy of the test and the service life of the device, the probe rod is made of alloy steel; the probe is made of alloy steel.

For the convenience of use, the probe has a conical structure, and the tip of the conical structure is arranged on the side away from the telescopic thermal probe.

In this embodiment, the length variation range of the telescopic thermal probe rod is 1 m, that is, the telescopic sleeve rod can be extended by about 1 m along with the penetration process.

Another object of the present invention is to provide a test method for an in-situ testing device for soil thermal conductivity and geothermal gradient, comprising the following steps:

Step 1. Adjust the thermal expansion probe to make it at the shortest length; insert the probe into the soil at a constant speed;

Step 2. When the probe reaches the test depth, the micromotor controls the extension of the telescopic sleeve rod (specifically, the telescopic sleeve rod is stretched under the action of the micromotor, and the micromotor is fixed on the telescopic sleeve rod and is fixedly connected with the annular thermal sensor at the same time. When telescoping is required, the micromotor acts on the telescopic sleeve to make it extend to the specified depth. After reaching the designated position, the first telescopic sleeve reaches the longest length, and the micromotor brakes to ensure that the ring sensor remains stationary at the designated position. , the micro motor stops and releases the brake on the telescopic sleeve rod, so as to release the ring sensor), every 20cm of extension, the micro motor at the top drives and releases the ring thermal sensor corresponding to the micro motor until all the After all the annular thermal sensors are released, stop penetrating; that is, after the device reaches the specified depth, every 20cm of penetration, the telescopic sleeve is extended by 20cm, and a ring-shaped thermal sensor is placed at this position;

Step 3: Keep one end stationary for a period of time to ensure that the ground temperature of the probe and the soil is consistent, and the data receiving module receives the test data of the annular thermal sensor at this time;

Step 4: Start the hot wire source to heat the soil, set the heating time, and the annular thermal sensor detects the ground temperature of the heated soil (that is, the thermal response data of the soil at different depths); the data receiving module receives the data detected by the annular thermal sensor at this time. temperature;

Step 5: The external external data processing system processes the data received by the data receiving module in step 3 and the data received by the data receiving module in step 4, and obtains the thermal conductivity of soil bodies at different depths.

Its calculation formula is as follows:

λ=(Q/4πΔT)ln(t ₂ /t ₁ )

In the formula, λ is the thermal conductivity, Q is the heat source energy, ΔT is the temperature change value, t ₂ and t ₁ are the heating time, where t ₁ is the heating time of the previous period, and t ₂ is the heating time of the latter period. The interval between the two should be greater than 100s.

The device combines the measurement of thermal conductivity coefficient and geothermal gradient, and solves the lack of existing domestic in-situ testing instruments for soil thermodynamic properties, as well as the problems that existing instruments are cumbersome, time-consuming, difficult to operate, and high cost. The in-situ dynamic testing device for basic thermodynamic properties of soil penetrates into the in-situ testing device, and can collect, process and store data by itself. It can provide fast, effective and low-cost test parameters for geothermal energy research and energy installation engineering design.

Claims (7)

1. an in-situ testing device of soil thermal conductivity and geothermal gradient, is characterized in that, comprises probe rod, telescopic thermal probe rod and probe connected successively from top to bottom; telescopic thermal probe rod comprises telescopic sleeve rod, annular Thermal sensor, hot wire source and micro motor; one end of the telescopic sleeve rod is connected to the probe, and the other end is connected to the probe rod; The telescopic sleeve rod can be extended and retracted under the power of the micro motor, and can be displaced with the expansion and contraction of the telescopic sleeve rod; there are two or more annular thermal sensors, and the annular thermal sensors are correspondingly installed on the micro motor; the heat source is located on the telescopic sleeve. In the rod, one end of the hot wire source is connected to the probe, and the other end extends into the probe rod; it also includes a data receiving module, which is arranged at the end of the probe rod and used to receive the data detected by the annular thermal sensor. 2 . The in-situ testing device for soil thermal conductivity and geothermal gradient according to claim 1 , wherein the telescopic sleeve rod is made of titanium alloy stainless steel. 3 . 3 . The in-situ testing device for soil thermal conductivity and geothermal gradient according to claim 1 , wherein the probe rod is made of alloy steel. 4 . 4 . The in-situ testing device for soil thermal conductivity and geothermal gradient according to claim 1 , wherein the probe is made of alloy steel. 5 . 5. The in-situ testing device for soil thermal conductivity and geothermal gradient according to claim 1, wherein the probe is a conical structure, and the tip of the conical structure is located at a distance away from the telescopic thermal probe. side. 6 . The in-situ testing device for soil thermal conductivity and geothermal gradient according to claim 1 , wherein the length variation range of the telescopic thermal probe rod is 1 m. 7 . 7. The test method of the in-situ testing device of soil thermal conductivity and geothermal gradient according to any one of claims 1-6, characterized in that, comprising the steps of: Step 1. Adjust the thermal expansion probe to make it at the shortest length; insert the probe into the soil at a constant speed; Step 2. When the probe reaches the test depth, the micromotor controls the extension of the telescopic sleeve rod. For each extension of 20cm, a micromotor in the relatively uppermost position drives the annular thermal sensor corresponding to the micromotor to move with the telescopic sleeve rod until all the When all the annular thermal sensors are released, stop penetration; Step 3: Keep still until the ground temperature of the probe and the soil is consistent, and the data receiving module receives the test data of the annular thermal sensor at this time; Step 4: Start the hot wire source to heat the soil, set the heating time, and the annular thermal sensor detects the ground temperature of the heated soil; the data receiving module receives the temperature detected by the annular thermal sensor at this time; Step 5: The external external data processing system processes the data received by the data receiving module in step 3 and the data received by the data receiving module in step 4, and obtains the thermal conductivity of soil bodies at different depths.

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