A method for confining pressure stress aging strengthening based on ice-soil mixture simulating lunar soil

Abstract

The present invention provides a confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil, belonging to the fields of lunar in-situ resource utilization and space exploration. It solves the problem of needing to design a simulated lunar soil confining pressure stress aging strengthening method with ultra-low temperature, stress aging, and temperature stress monitoring to meet various special working conditions, and proposes a confining pressure stress aging strengthening method that can be maintained at about -180°C and statically compacted, which can strictly control the temperature and pressure of the ice-soil and the effectiveness of stress aging. For the confining pressure stress aging strengthening method of ice-soil mixed simulated lunar soil proposed by the present invention, the mass of water required is calculated according to the water content required for the test. The water is placed in a container, gradually evacuated, and given a low-temperature environment of -80°C for freezing to make ice. After the ice-making is completed, the ice cubes are placed in a ice crusher until they are uniformly crushed into small particles for standby. The particle size of the particles prepared by this method can be better mixed with the simulated lunar soil particles to achieve homogeneity.

Description

Technical Field

[0001] The present invention belongs to the fields of in-situ lunar resource utilization and space exploration, and particularly relates to a confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil. Background Art

[0002] At present, the research and drilling of real lunar soil are becoming increasingly urgent for understanding its main components and mechanical properties. So far, the ground-simulated lunar soil layers mainly include water-mixed soil, ice-mixed soil, and vapor-condensed ice simulated lunar soil. Regarding the confining pressure stress aging strengthening, it is mainly carried out for water-mixed soil, and there is no corresponding specific implementation or good progress for the other two. Moreover, the preparation technology of vapor-condensed ice is not mature, so there are certain limitations. Therefore, there is a need for a confining pressure stress aging strengthening method for ice-mixed soil simulated lunar soil to meet the requirements of corresponding working conditions or extreme working conditions.

[0003] For the current stress aging strengthening method of water-containing simulated lunar soil - water-mixed soil simulated lunar soil, the simulated lunar soil after being dried in an oven is used, and then ultrapure water is added for water mixing to prepare the simulated lunar soil with the corresponding moisture content. After standing and homogenizing, it is put into a lunar soil bucket. The hydraulic press is used to statically press and compact the water-containing simulated lunar soil in the lunar soil bucket, and then it is put into a low-temperature refrigerator for gradient refrigeration, and finally the purpose of confining pressure stress aging strengthening is achieved. However, this method has certain water loss, resulting in inaccurate moisture content.

[0004] Therefore, there is an urgent need to design a simulated lunar soil confining pressure stress aging strengthening method with little interference from water loss, a high-precision moisture content in a constant ultra-low temperature environment, and good uniformity to meet the requirements of corresponding working conditions and extreme working conditions. Summary of the Invention

[0005] In view of this, in order to solve the problem of designing a simulated lunar soil confining pressure stress aging strengthening method with ultra-low temperature, stress aging, and temperature stress monitoring to meet various special working conditions, the present invention proposes a confining pressure stress aging strengthening method that can be maintained at about -180°C and statically compacted, which can strictly control the temperature and pressure of the ice-soil and the effectiveness of stress aging.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil, specifically including the following steps:

[0007] Step S1: Select anorthosite and basalt as the raw materials for preparing the simulated lunar soil according to the mineral components of polar region lunar soil;

[0008] Step S2: Mix 10 kg of raw materials, and use a stirrer to stir evenly at a speed of 50 r / min for 1 min at room temperature, and then stir evenly at a speed of 180 r / min for 5 minutes;

[0009] Step S3: weigh the mass of the sample before drying and adjust the temperature of the dryer to 105° C. for more than 6 hours until the sample is dried to a constant weight;

[0010] Step S4: Before mixing the ice soil, use liquid nitrogen to pre-cool the ice soil mixing equipment and related equipment and simulated lunar soil particles to -180°C;

[0011] Step S5: weigh the mass of the dried sample and calculate the initial moisture content using a formula;

[0012] Step S6: Calculate the required water mass according to the required water content of the test, put the water in a container, gradually evacuate the container and freeze it at a low temperature of -80°C to make ice. After the ice making is completed, put the ice cubes in an ice crusher until they are evenly crushed into small particles for standby use;

[0013] Step S7: pour the ice particles and simulated lunar soil particles into a pre-cooled stirring device, and continuously stir the samples at a low temperature of -180°C to achieve uniform mixing of the samples;

[0014] Step S8: Before the dense container is loaded, the ultra-low temperature strain gauge is first attached to its side wall, and the ultra-low temperature strain gauge is calibrated at room temperature;

[0015] Step S9: The low-temperature shaping process adopts a static compaction method at a low temperature of -180°C. To ensure the uniformity of the density of the sample along the depth direction, the compaction process needs to be added layer by layer and compacted layer by layer;

[0016] Step S10: Use a plastic wrap or a transparent sealing bag to seal the upper surface of the cross-section sample that is in contact with the air, then use a hand drill to drill a hole at the preset sensing location, insert the temperature sensor through the hollow bolt into the sensor hole, wrap the raw tape around it, and tighten the bolt; arrange two temperature sensors at a certain distance in the depth direction of the sample, connect the installed temperature sensors to the temperature converter, connect the power supply, and continuously record the temperature change;

[0017] Step S11: After low-temperature shaping, continue to maintain the low-temperature environment, use the stress aging application device to apply confining pressure to the sample, and use the monitoring device to monitor the temperature and pressure in real time; then, perform gradient cooling on it, put it into a low-temperature refrigerator, and according to the collection and monitoring of the temperature and pressure sensors, keep it at 0℃~-30℃, and the cooling time is about 12h. Then, put it into an ultra-low temperature refrigerator, and finally put it into a pre-cooled liquid nitrogen barrel for three-stage cooling. When the liquid nitrogen evaporates, the simulated lunar soil will gradually heat up, and let it stand for 30~60min, and continuously record the temperature change and pressure change;

[0018] Step S12: The simulated lunar soil that has been gradient cooled is transferred while maintaining a low temperature of -180°C and kept aside for testing.

[0019] Further, in step S2, two types of soils with particle sizes less than 1 mm are selected for mixing.

[0020] Further, in step S2: 10 kg of raw materials are mixed with anorthosite and basalt in a ratio of 7:3.

[0021] Further, in step S5, the maximum allowable error should be ±0.5%. If the moisture content is within the allowable error range, the ice and soil mixing continues; otherwise, it needs to be dried again until the moisture content is within the error range.

[0022] Further, in step S7, first stir slowly at 50 r / min for 20 min, and then adjust to fast stirring for 10 min to achieve uniform mixing of the samples.

[0023] Further, in step S9, a fixed mass of simulated lunar soil is weighed each time and poured into the lunar soil bucket. A pre-cooled mass block is pressed above the sample, and the press head is controlled to feed at a constant speed. The maximum pressure does not exceed 100 kN. The compaction height is determined according to the scale marked on the compaction block. After compaction to the specified height, keep the pressure for 30 s and then release the pressure; after each layer is pressed, the upper surface needs to be scraped to prevent the sample from being segmented.

[0024] Further, in step S10, one temperature sensor is inserted 50 mm into the sample, and the other temperature sensor is inserted 40 mm into the sample. The two temperature sensors are symmetrically distributed.

[0025] Further, in step S11, a confining pressure is applied to the sample using a stress aging application device. The maximum applied pressure is 8 kN, and the confining pressure holding time is 12 h.

[0026] Further, in step S11, it is placed in an ultra-low temperature refrigerator. According to the acquisition and monitoring of the temperature and pressure sensors, it is maintained at -30°C to -80°C, and the refrigeration time is about 24 h.

[0027] Further, in step S11, the three-stage refrigeration is based on the acquisition and monitoring of the temperature and pressure sensors, and it is maintained at -80°C to -180°C, and the refrigeration duration is 3 - 4 h.

[0028] Compared with the prior art, the beneficial effects of the method for confining pressure stress aging strengthening of simulated lunar soil based on ice and soil mixing according to the present invention are:

[0029] (1) The method for strengthening the confining pressure stress aging of ice-soil mixed simulated lunar soil proposed by the present invention calculates the mass of water required according to the water content required for the test, places the water in a container, gradually evacuates it, and gives it a low-temperature environment of -80°C for freezing to make ice. After the ice-making is completed, the ice cubes are placed in a ice crusher until they are uniformly crushed into small particles for standby. The particle size prepared by this method can better mix with the simulated lunar soil particles to achieve homogeneity.

[0030] (2) For the method for strengthening the confining pressure stress aging of ice-soil mixed simulated lunar soil proposed by the present invention, before the dense container is loaded, the side wall of the container should be attached with a 3×3 array of ultra-low temperature strain gauges, and the ultra-low temperature strain gauges should be calibrated at room temperature, so that the pressure change can be recorded when applying the low-temperature stress confining pressure.

[0031] (3) After the stress aging treatment, the intermolecular force between the lunar soil particles and the ice particles increases compared with that before application, so that the two interfaces are fused, resulting in an increase in the cementation strength between the particles and an improvement in the mechanical properties. Description of the Drawings

[0032] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 is a flow chart of the method for strengthening the confining pressure stress aging of ice-soil mixed simulated lunar soil according to the present invention. Detailed Embodiments

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention may be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0035] I. Detailed Embodiment 1, see Figure 1 This embodiment is described. A method for strengthening the confining pressure stress aging of ice-soil mixed simulated lunar soil includes 12 steps of basic raw material preparation and selection, raw material mixing, drying, pre-cooling, water content detection, ice particle preparation, ice-soil mixing, stress sensing presetting, low-temperature shaping, low-temperature sensing presetting, low-temperature stress aging, and sample transfer. The specific steps are as follows:

[0036] Step S1: According to the mineral composition of the polar lunar soil, anorthosite and basalt are selected as the raw materials for preparing the simulated lunar soil. The particle size of the polar lunar soil is mainly less than 1 mm, so the simulated lunar soil with a particle size of 0-1 mm is selected to be made into angular and sub-angular shapes.

[0037] Step S2: Mix 10 kg of raw materials by blending anorthosite and basalt at a ratio of 7:3. After stirring evenly at a speed of 50 r / min for 1 min with a stirrer at room temperature, then stir evenly at 180 r / min for 5 minutes.

[0038] Step S3: Weigh the mass of the specimen before drying and set the temperature of the dryer to 105 °C. The drying time is more than 6 hours until the specimen is dried to a constant weight.

[0039] Step S4: Before the ice and regolith mixing, pre-cool the ice and regolith mixing equipment, related equipment, and simulated regolith particles to -180 °C with liquid nitrogen.

[0040] Step S5: Weigh the mass of the dried specimen and calculate the initial moisture content through a formula. The maximum allowable error should be ±0.5%. If the moisture content is within the error range, continue with the ice and regolith mixing; otherwise, re-dry until the moisture content is within the error range.

[0041] Step S6: Calculate the mass of water required according to the moisture content required for the experiment. Place the water in a container, gradually evacuate it to a vacuum, and subject it to a low-temperature environment of -80 °C for freezing to make ice. After the ice-making is completed, place the ice cubes in a crusher until they are evenly crushed into small particles for standby.

[0042] Step S7: Pour the ice particles and simulated regolith particles into the pre-cooled stirring equipment. Under the condition of a low temperature of -180 °C, continuously stir the sample. First, stir slowly at 50 r / min for 20 min, and then adjust to fast stirring for 10 min to achieve uniform mixing of the sample.

[0043] Step S8: Before the dense container is filled, first attach a 3×3 array of cryogenic strain gauges to its side wall, and perform calibration of the cryogenic strain gauges at room temperature.

[0044] Step S9: The cryogenic shaping process adopts the method of static compaction in a low-temperature environment of -180 °C. To ensure the uniformity of the density of the sample in the longitudinal direction, the compaction process needs to be added layer by layer and compacted layer by layer. Weigh a fixed mass of simulated regolith each time, pour it into the regolith bucket, press the pre-cooled mass block above the sample, control the constant-speed feeding of the pressure head of the press, and the maximum pressure does not exceed 100 kN. Determine the compaction height according to the scale marked on the compaction block. After compaction to the specified height, keep the pressure for 30 s and then release the pressure. After each layer is compacted, the upper surface needs to be scraped to prevent the sample from being segmented.

[0045] Step S10: Seal the part of the upper surface of the cross-section sample that is in contact with air with plastic wrap or a transparent seal bag. Then, first drill a hole at the preset sensing location with a hand drill. Insert the Pt100 temperature sensor through the hollow bolt into the sensor hole, wrap the thread seal tape, and tighten the bolt. Arrange two sensors at a certain distance in the depth direction of the sample. One sensor is inserted 50 mm into the sample, and the other sensor is inserted 40 mm into the sample. The two sensors are symmetrically distributed. Connect the installed sensors to the temperature transducer, connect the power supply and turn it on, and continuously record the temperature change.

[0046] Step S11: After low-temperature shaping, continue to maintain the low-temperature environment. Use the stress aging application device to apply confining pressure to the sample. The maximum applied pressure is 8 kN, and the confining pressure holding time is 12 h. Use the monitoring device to monitor the temperature and pressure in real time. Then, perform gradient refrigeration on it. Put it into a low-temperature refrigerator. According to the acquisition and monitoring of the temperature and pressure sensors, make its temperature range from 0 °C to -30 °C, and the refrigeration time is about 12 h. Then, put it into an ultra-low temperature refrigerator. According to the acquisition and monitoring of the temperature and pressure sensors, make its temperature range from -30 °C to -80 °C, and the refrigeration time is about 24 h. Finally, put it into a pre-cooled liquid nitrogen tank for three-stage refrigeration. According to the acquisition and monitoring of the temperature and pressure sensors, make its temperature range from -80 °C to -180 °C, and the refrigeration duration is 3 - 4 h. Then, wait until the liquid nitrogen has evaporated (about 20 - 30 min). The simulated lunar soil will gradually warm up. Let it stand for 30 - 60 min, and continuously record the temperature change and pressure change.

[0047] Step S12: Transfer the simulated lunar soil after gradient refrigeration while ensuring a low temperature of -180 °C for standby experiments.

[0048] The working principle of the strengthening method of the present invention is that in the first preparation of ice-mixed soil, i.e., the simulated lunar soil particles and ice particles are uniformly mixed. The lunar soil particles and ice particles form stress extrusion through the force given by the stirrer, so that the molecular spacing is shortened and the lunar soil particles and ice particles achieve stress bonding. The water molecules in the ice bond with the simulated lunar soil particles to form an ice film that wraps the lunar soil particles.

[0049] After applying confining pressure to the ice-mixed soil, the stress extrusion between the lunar soil particles and ice particles is enhanced, so that the two interfaces fuse, and the molecular force is increased compared with that before application, and the bonding effect is enhanced.

[0050] Since this method uses stress extrusion to enhance the molecular force between the simulated lunar soil particles and ice particles, the performance of the ice-soil mixture is enhanced, and the strengthening effect is increased.

[0051] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. According to the content of this specification, many modifications and variations can be made. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. A method for confining pressure stress aging strengthening based on ice-soil mixture simulating lunar soil, characterized in that: The specific steps include: Step S1: selecting plagioclase and basalt as raw materials for preparing simulated lunar soil according to the mineral composition of polar lunar soil; Step S2: 10 kg of raw materials were mixed and stirred at 50 r / min for 1 min at room temperature, and then stirred at 180 r / min for 5 min to mix evenly; Step S3: weigh the mass of the sample before drying and adjust the temperature of the dryer to 105° C. for more than 6 hours until the sample is dried to a constant weight; Step S4: Before mixing the ice soil, use liquid nitrogen to pre-cool the ice soil mixing equipment and related equipment and simulated lunar soil particles to -180°C; Step S5: weigh the mass of the dried sample and calculate the initial moisture content using a formula; Step S6: Calculate the required water mass according to the required water content of the test, put the water in a container, gradually evacuate the container and freeze it at a low temperature of -80°C to make ice. After the ice making is completed, put the ice cubes in an ice crusher until they are evenly crushed into small particles for standby use; Step S7: pour the ice particles and simulated lunar soil particles into a pre-cooled stirring device, and continuously stir the samples at a low temperature of -180°C to achieve uniform mixing of the samples; Step S8: Before the dense container is loaded, the ultra-low temperature strain gauge is first attached to its side wall, and the ultra-low temperature strain gauge is calibrated at room temperature; Step S9: The low-temperature shaping process adopts a static compaction method at a low temperature of -180°C. To ensure the uniformity of the density of the sample along the depth direction, the compaction process needs to be added layer by layer and compacted layer by layer; Step S10: Use a plastic wrap or a transparent sealing bag to seal the upper surface of the cross-section sample that is in contact with the air, then use a hand drill to drill a hole at the preset sensing location, insert the temperature sensor through the hollow bolt into the sensor hole, wrap the raw tape around it, and tighten the bolt; arrange two temperature sensors at a certain distance in the depth direction of the sample, connect the installed temperature sensors to the temperature converter, connect the power supply, and continuously record the temperature change; Step S11: After the low-temperature shaping, the low-temperature environment is continued to be maintained, a stress aging applying device is used to apply confining pressure to the sample, and a monitoring device is used to monitor the temperature and pressure in real time; Afterwards, it is subjected to gradient cooling and placed in a low-temperature refrigerator. According to the collection and monitoring of temperature and pressure sensors, it is kept at 0℃~-30℃ for 10-14h. Then, it is placed in an ultra-low temperature refrigerator, and finally placed in a pre-cooled liquid nitrogen barrel for three-stage cooling. When the liquid nitrogen evaporates, the simulated lunar soil will gradually heat up and be allowed to stand for 30~60min, and the temperature and pressure changes are continuously recorded. Step S12: The simulated lunar soil that has been gradient cooled is transferred while maintaining a low temperature of -180°C and kept aside for testing.

2. The confining pressure stress aging strengthening method based on ice-soil mixture simulating lunar soil according to claim 1, wherein: In step S2, two types of soil with a particle size less than 1 mm are selected for mixing.

3. The confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil according to claim 2, characterized in that: Step S2: 10 kg of raw materials are mixed with anorthite and basalt in a ratio of 7:

3.

4. The confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil according to claim 1, characterized in that: In step S5, the maximum allowable error should be ±0.5%. If the moisture content is within the allowable error range, ice-soil mixing is continued; otherwise, drying is required again until the moisture content is within the error range.

5. The confining pressure stress aging strengthening method based on ice-soil mixture simulating lunar soil according to claim 1, characterized in that: In step S7, first stir slowly at 50 r / min for 20 min, and then adjust to fast stirring for 10 min to achieve uniform mixing of the sample.

6. The confining pressure stress aging strengthening method based on ice-soil mixture simulating lunar soil according to claim 1, wherein: In step S9, each time a fixed mass of simulated lunar soil is weighed and poured into the lunar soil bucket. A pre-cooled mass block is pressed above the sample, and the press head is controlled to feed at a constant speed with the maximum pressure not exceeding 100 kN. The compaction height is determined according to the scale marked on the compaction block. After compaction to the specified height, keep the pressure for 30 s and then release the pressure; after each layer is compacted, the upper surface needs to be roughened to prevent the sample from being segmented.

7. The confining pressure stress aging strengthening method based on ice-soil mixture simulating lunar soil according to claim 1, characterized in that: In step S10, one temperature sensor is inserted 50 mm into the sample, and the other temperature sensor is inserted 40 mm into the sample. The two temperature sensors are symmetrically distributed.

8. The confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil according to claim 1, characterized in that: In step S11, a confining pressure is applied to the sample using a stress aging application device, with the maximum applied pressure being 8 kN and the confining pressure holding time being 12 h.

9. The confining pressure stress aging strengthening method based on ice-soil mixture simulating lunar soil according to claim 1, wherein: In step S11, it is placed in an ultra-low temperature refrigerator. According to the acquisition and monitoring of the temperature and pressure sensors, the temperature is maintained at -30°C to -80°C for 24 h.

10. The confining pressure stress aging strengthening method based on ice-soil mixed simulated lunar soil according to claim 1, characterized in that: In step S11, the three-stage refrigeration is based on the acquisition and monitoring of the temperature and pressure sensors, with the temperature maintained at -80°C to -180°C for 3 to 4 h.

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