Cement mixing pile single-pile composite foundation static load test device and method

Abstract

The invention discloses a cement mixing pile single-pile composite foundation static load test device and method, and relates to the technical field of foundation load test devices.The cement mixing pile single-pile composite foundation static load test device comprises a rack with a power loading head, and the rack is provided with a bearing plate, a first loading plate and a second loading plate; a layered displacement monitoring mechanism and a data analysis mechanism are arranged on the rack; and the layered displacement monitoring mechanism is used for detecting the displacement of the second loading plate. By arranging the data analysis mechanism, two kinds of thrust are formed to jointly act on the sliding piston in the thaw collapse displacement average hydraulic cavity, the displacement of the sliding piston is detected by the first displacement sensor to obtain thaw collapse displacement, and the bearing displacement is calculated by combining the total displacement obtained by the layered displacement monitoring mechanism; the mechanism realizes accurate separation of frozen soil thaw collapse displacement and bearing displacement through a mechanical structure, solves the problem of test result deviation caused by incapability of distinguishing two types of deformation, and enables test data to truly reflect the bearing capacity characteristic of a single-pile composite foundation.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation load testing devices, and in particular to a static load testing device and method for a cement mixing pile single pile composite foundation. Background Art

[0002] In the field of engineering construction in plateau permafrost areas, the bearing capacity assessment of cement-mixed single-pile composite foundations relies on static load tests, but the special permafrost environment in this area poses a significant challenge to the accuracy of the test. The average annual temperature in plateau permafrost areas is low, and it is in a negative temperature state for a long time from winter to spring. Permafrost has significant thawing and settling characteristics, and a slight change in temperature may cause permafrost structural damage and volume shrinkage. According to relevant specifications, static load tests need to be carried out in a graded manner as required, and each grade of load needs to be maintained for a long time to ensure data stability; however, the existing static load test equipment for single-pile composite foundations in plateau permafrost areas still has the following defects during use.

[0003] Existing static load tests on composite foundations only focus on collecting the total displacement of the pile top. However, due to the different strengths of the single pile and the foundation around it, relative displacement is inevitable when loading pressure is applied, causing contact friction heat, which in turn has a thermal impact on the frozen soil around the pile. As a result, the thaw settlement displacement of the frozen soil cannot be effectively identified during the static load test of the composite foundation. As a result, the test results may still be biased due to misjudgment of thaw settlement deformation, affecting the reliability of the test data and making it difficult to meet the actual engineering needs of accurately evaluating the bearing capacity of single-pile composite foundations in plateau permafrost areas. Summary of the Invention

[0004] The purpose of this application is to provide a static load test device and method for a cement mixing pile single composite foundation, which can effectively solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: a static load test device for a single cement mixing pile composite foundation, comprising a frame with a power loading head, the frame being provided with a pressure plate, a first loading plate and a second loading plate; a connecting mechanism being provided between the pressure plate and the second loading plate; the bottom end of the first loading plate being in contact with the top of the pile, and the bottom end of the second loading plate being in contact with the foundation around the pile; the pressure applied by the power loading head to the pressure plate is transmitted to the first loading plate and the second loading plate through the connecting mechanism, so as to apply the same pressure to the first loading plate and the second loading plate; a heat insulation temperature control mechanism being provided on the second loading plate, and being used to control the temperature between the second loading plate and the foundation around the pile; a layered displacement monitoring mechanism and a data analysis mechanism being provided on the frame; the layered displacement monitoring mechanism being used to detect the second The displacement of the loading plate; the data analysis mechanism includes: a temperature conversion mechanism, a displacement hydraulic transmission mechanism and a thawing displacement averaging hydraulic chamber; wherein, the temperature conversion mechanism is arranged on the frame, and is used to convert the temperature rise of the foundation around the pile into air pressure thrust; the displacement hydraulic transmission mechanism is arranged on the frame, and is used to convert the displacement between the second loading plate and the stable frozen soil layer at the bottom of the foundation around the pile into hydraulic thrust; the thawing displacement averaging hydraulic chamber is arranged on the frame, and a sliding piston sliding along its axial direction is arranged in the thawing displacement averaging hydraulic chamber, and the sliding piston divides the interior of the thawing displacement averaging hydraulic chamber into two chambers, one of which is connected to the temperature conversion mechanism, and the other is connected to the displacement hydraulic transmission mechanism; a first displacement sensor is arranged in the thawing displacement averaging hydraulic chamber, and is used to detect the displacement of the sliding piston.

[0006] Preferably: the connecting mechanism includes a telescopic shaft and a plurality of guide shafts; the plurality of guide shafts are connected to the frame along their axial sliding connection, and the ends of the plurality of guide shafts are connected to the second loading plate; the pressure plate slides axially along the guide shaft, and the telescopic shaft is arranged between the pressure plate and the first loading plate; springs are both provided on the guide shaft and the telescopic shaft; when the power loading head applies pressure to the pressure plate, the pressure of the power loading head is transmitted to the first loading plate and the second loading plate through the spring.

[0007] Preferably: the heat-insulating temperature control mechanism includes a plurality of temperature sensors; the plurality of temperature sensors are arranged at the bottom of the second loading plate, and the plurality of temperature sensors are arranged at different depths of the foundation around the pile; a medium circulation cavity is opened in the second loading plate, the medium circulation cavity is in the shape of a spiral groove, and the medium circulation cavity is filled with a cooling medium; by driving the cooling medium to flow in the spiral groove, the heat generated when the second loading plate is loaded is offset.

[0008] Preferably, a plurality of heat-conducting sleeves are provided at the bottom of the second loading plate, and the temperature sensor is provided in the heat-conducting sleeves; the heat-conducting sleeves are used to isolate the temperature sensor from the foundation around the pile.

[0009] Preferably: the layered displacement monitoring mechanism includes multiple second displacement sensors, reflective targets and third displacement sensors; multiple second displacement sensors are arranged on the top of the frame, multiple reflective targets are arranged on the first loading plate, and the reflective targets and the second displacement sensors are arranged in upper and lower alignment; multiple third displacement sensors are arranged at the bottom of the second loading plate, and multiple third displacement sensors are arranged at different depths of the foundation around the pile, one end of the third displacement sensor is connected to the second loading plate, and the other end of the third displacement sensor is connected to the stable frozen soil layer at the bottom of the foundation around the pile.

[0010] Preferably: the layered displacement monitoring mechanism also includes a carbon fiber connecting rod and an anchor rod; the movable end of the third displacement sensor is connected to the second loading plate through the carbon fiber connecting rod, and the fixed end of the third displacement sensor is fixed to the stable frozen soil layer at the bottom of the foundation around the pile through the anchor rod.

[0011] Preferably: the temperature conversion mechanism includes an airbag, a piston rod and a plurality of clamps; the airbag is fixed to the frame by a plurality of clamps, and the airbag is coaxially arranged with the melting displacement average hydraulic chamber; the airbag is filled with dry nitrogen, and the initial pressure in the airbag is balanced with the ambient air pressure; the interior of the airbag is connected to the interior of the heat-conducting sleeve through a conduit; the clamps are arranged at equal intervals along the axial direction of the airbag to prevent the airbag from undergoing radial deformation; the piston rod is coaxially slidably connected to the airbag through a piston head connected to one end thereof, and the other end of the piston rod extends to the interior of the melting displacement average hydraulic chamber and is coaxially connected to the sliding piston; The catheter is a flexible heat-insulating pipeline structure, and the flexible heat-insulating pipeline is used to transfer the temperature inside the heat-conducting sleeve to the airbag and allow relative displacement between the heat-conducting sleeve and the airbag.

[0012] Preferably: the displacement hydraulic transmission mechanism includes a cylinder body and a hydraulic push rod; the cylinder body is fixed to the second loading plate, the hydraulic push rod is coaxially slidably connected to the cylinder body through its end piston head, and the other end of the hydraulic push rod is coaxially connected to the carbon fiber connecting rod; the interior of the cylinder body and the space between the piston head of the hydraulic push rod are filled with oil, and the oil in the cylinder body is connected to one of the chambers in the melting displacement averaging hydraulic chamber through a high-pressure hose.

[0013] Preferably, an exhaust valve is provided at the top of the melt-sink displacement average hydraulic chamber near the displacement hydraulic transmission mechanism, and is used to exhaust the air existing at the top of the oil in the melt-sink displacement average hydraulic chamber.

[0014] A method for static load testing of a cement mixing pile single pile composite foundation, using the above-mentioned static load testing device for a cement mixing pile single pile composite foundation, specifically comprising the following steps: Step 1: Temperature control: The friction heat of the second loading plate is removed by the heat insulation temperature control mechanism to reduce the temperature increase of the frozen soil around the pile. At the same time, the temperature change of the frozen soil is monitored in real time to provide a temperature basis for the calculation of thaw settlement deformation; Step 2: Displacement monitoring: Simultaneously collect the displacement of the pile top and the displacement of the frozen soil stratification around the pile, and obtain the original data of the two deformations to provide the displacement basis for subsequent separation calculation; Step 3: Conversion analysis: The temperature of the frozen soil around the pile is converted into air pressure thrust through the temperature conversion mechanism, providing thrust on one side for the sliding piston. The displacement between the stable frozen soil layer at the bottom of the foundation around the pile is converted into hydraulic thrust through the displacement hydraulic transmission mechanism, providing thrust on the other side for the sliding piston. At the same time, the displacement of the sliding piston is detected by the first displacement sensor and determined to be thaw-settlement displacement. The displacement detected by the layered displacement monitoring mechanism is marked as the total displacement. The difference between the total displacement and the thaw-settlement displacement is calculated and marked as the bearing displacement, thereby realizing the static load test of the single pile composite foundation.

[0015] In summary, the technical effects and advantages of the present invention are as follows: 1. The present invention provides a data analysis mechanism. Its temperature conversion mechanism converts changes in the foundation temperature around the pile into pneumatic thrust, and its displacement hydraulic transmission mechanism converts the thaw displacement around the pile into hydraulic thrust. These two thrusts act together on a sliding piston in a thaw displacement averaging hydraulic chamber. The sliding piston displacement is detected by a first displacement sensor to obtain the thaw displacement, which is then combined with the total displacement obtained by the layered displacement monitoring mechanism to calculate the bearing displacement. This mechanism achieves precise separation of frozen soil thaw displacement and bearing displacement through a mechanical structure, solving the problem of test result deviation caused by the inability to distinguish between the two deformations, and ensuring that the test data can truly reflect the bearing capacity characteristics of a single pile composite foundation.

[0016] 2. The present invention provides a heat-insulating temperature-control mechanism, allowing the cooling medium to continuously flow in the medium circulation cavity within the second loading plate, absorbing the frictional heat generated during the loading process. Simultaneously, multiple temperature sensors are distributed at different depths in the foundation around the pile to monitor temperature changes in real time and adjust the cooling medium flow rate accordingly. This allows the temperature rise of the frozen soil around the pile to be controlled, minimizing freeze-thaw settlement caused by factors not necessary for the test, providing a stable temperature environment for displacement separation analysis, and significantly improving the reliability of the test data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1This is a schematic diagram of the three-dimensional structure of the present invention in use; Figure 2 It is a partially cutaway three-dimensional structural schematic diagram of the present invention; Figure 3 This is a partially cutaway, three-dimensional, enlarged structural diagram of the second loading plate of the present invention; Figure 4 It is a schematic diagram of the overall three-dimensional structure of the present invention; Figure 5 For the present invention Figure 4 Schematic diagram of the enlarged structure of area A in the middle; Figure 6 It is a schematic diagram of a three-dimensional magnified structure of the data analysis mechanism of the present invention; Figure 7 It is a schematic diagram of the three-dimensional enlarged structure of the temperature conversion mechanism and the displacement hydraulic transmission mechanism of the present invention; Figure 8 It is a partially cutaway, three-dimensional, and enlarged structural diagram of the temperature conversion mechanism of the present invention; Figure 9 It is a partially cutaway, three-dimensional, and enlarged structural diagram of the displacement hydraulic transmission mechanism of the present invention; Figure 10 Flow chart of the method of the present invention.

[0019] In the figure: 1. Frame; 2. Pressure plate; 3. First loading plate; 4. Second loading plate; 5. Connecting mechanism; 51. Guide shaft; 52. Telescopic shaft; 53. Spring; 6. Thermal insulation and temperature control mechanism; 61. Medium circulation chamber; 62. Temperature sensor; 63. Thermal sleeve; 7. Layered displacement monitoring mechanism; 71. Second displacement sensor; 72. Reflection target; 73. Third displacement sensor; 74. Carbon fiber connecting rod; 75. Anchor rod; 8. Data analysis mechanism; 81. Temperature conversion mechanism; 811. Airbag; 812. Clamp; 813. Conduit; 814. Piston rod; 82. Displacement hydraulic transmission mechanism; 821. Cylinder; 822. Hydraulic push rod; 823. High-pressure hose; 83. Melting displacement averaging hydraulic chamber; 84. Sliding piston; 85. Exhaust valve. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Example 1: Please refer to Figure 1-Figure 2The static load test device for a single cement mixing pile composite foundation shown in the figure comprises a frame 1 with a power loading head; it is understandable that the power loading head is a prior art, which is not shown in the figure and will not be described in detail; a pressure plate 2, a first loading plate 3 and a second loading plate 4 are provided on the frame 1; a connecting mechanism 5 is provided between the pressure plate 2 and the second loading plate 4; the bottom end of the first loading plate 3 contacts the top of the pile, and the bottom end of the second loading plate 4 contacts the foundation around the pile; the pressure applied by the power loading head to the pressure plate 2 is transmitted to the first loading plate 3 and the second loading plate 4 through the connecting mechanism 5 to apply the same pressure to the first loading plate 3 and the second loading plate 4; a heat insulation temperature control mechanism 6 is provided on the second loading plate 4, and is used to control the temperature between the second loading plate 4 and the foundation around the pile; a layered displacement monitoring mechanism 7 and a data analysis mechanism 8 are provided on the frame 1; the layered displacement monitoring mechanism 7 is used to detect the displacement of the second loading plate 4; the data analysis mechanism 8 It includes: a temperature conversion mechanism 81, a displacement hydraulic transmission mechanism 82 and a thawing displacement averaging hydraulic chamber 83; wherein, the temperature conversion mechanism 81 is arranged on the frame 1, and is used to convert the temperature increase of the foundation around the pile into air pressure thrust; the displacement hydraulic transmission mechanism 82 is arranged on the frame 1, and is used to convert the displacement between the second loading plate 4 and the stable frozen soil layer at the bottom of the foundation around the pile into hydraulic thrust; the thawing displacement averaging hydraulic chamber 83 is arranged on the frame 1, and a sliding piston 84 sliding along its axial direction is arranged in the thawing displacement averaging hydraulic chamber 83, and the sliding piston 84 divides the interior of the thawing displacement averaging hydraulic chamber 83 into two chambers, one of which is connected to the temperature conversion mechanism 81, and the other is connected to the displacement hydraulic transmission mechanism 82; a first displacement sensor is arranged in the thawing displacement averaging hydraulic chamber 83, and is used to detect the displacement of the sliding piston 84; it can be understood that the first displacement sensor is a prior art, which is not drawn in the figure and will not be described in detail.

[0022] It should be noted that when the power loading head on the frame 1 is started, the power loading head applies pressure to the pressure plate 2, and the pressure is transmitted to the first loading plate 3 and the second loading plate 4 through the connecting mechanism 5 between the pressure plate 2 and the second loading plate 4, so that the first loading plate 3 contacts the top of the cement mixing pile and the second loading plate 4 contacts the foundation around the pile and jointly bears the load. During the loading process, the heat insulation and temperature control mechanism 6 on the second loading plate 4 continues to work to control the temperature between the second loading plate 4 and the foundation around the pile, so as to avoid the contact friction heat generated by the first loading plate 3 and the second loading plate 4 with the pile top and the foundation around the pile during loading, causing significant thermal impact on the frozen soil around the pile. At the same time, the layered displacement monitoring mechanism 7 on the frame 1 detects the displacement of the second loading plate 4 in real time, and obtains the total displacement data including the bearing deformation and the melting deformation. The data analysis mechanism 8 operates synchronously, the temperature conversion mechanism 81 converts the temperature rise of the foundation around the pile into an air pressure thrust, and the displacement hydraulic transmission mechanism 82 converts the displacement between the second loading plate 4 and the stable frozen soil layer at the bottom of the foundation around the pile into a hydraulic thrust. The two thrusts act on both sides of the sliding piston 84 in the thawing displacement average hydraulic chamber 83, respectively, pushing the sliding piston 84 to slide axially along the thawing displacement average hydraulic chamber 83. The first displacement sensor provided in the thawing displacement average hydraulic chamber 83 detects the displacement of the sliding piston 84, which is the thawing displacement of the frozen soil around the pile. Finally, by calculating the difference between the total displacement detected by the layered displacement monitoring mechanism 7 and the thawing displacement, the bearing displacement caused only by insufficient bearing capacity of the foundation is obtained, and the static load test of the cement mixing pile single pile composite foundation is completed; The connecting mechanism 5 ensures stable transmission of pressure from the dynamic loading head to the first and second loading plates 3 and 4, ensuring that the top of the cement-mixed pile and the surrounding ground are always in a coordinated state of stress during the test, consistent with the actual stress characteristics of a single-pile composite foundation. The thermal insulation and temperature control mechanism 6 effectively controls temperature fluctuations in the ground surrounding the pile, minimizing freeze-thaw and thaw settlement unnecessary for the test and providing a stable environment for subsequent displacement separation.

[0023] The collaboration between the layered displacement monitoring mechanism 7 and the data analysis mechanism 8 enables precise separation of total displacement and thaw-settlement displacement. This solves the existing problem of test result deviations caused by the inability to identify thaw-settlement displacement of frozen soil. This ensures that the reliability of the test data remains high, meeting the practical engineering needs of accurately assessing the bearing capacity of single-pile composite foundations in plateau permafrost regions. Furthermore, the data analysis mechanism 8 uses a mechanical structure to achieve coupled calculations of temperature and displacement, preventing performance degradation of electronic components in the low-temperature environment of the plateau and improving the device's adaptability and stability in extreme environments.

[0024] See also Figure 1-Figure 2The connecting mechanism 5 includes a telescopic shaft 52 and multiple guide shafts 51; the multiple guide shafts 51 are connected to the frame 1 along their axial sliding connection, and the ends of the multiple guide shafts 51 are connected to the second loading plate 4; the pressure plate 2 slides axially along the guide shaft 51, and the telescopic shaft 52 is arranged between the pressure plate 2 and the first loading plate 3; springs 53 are both provided on the guide shaft 51 and the telescopic shaft 52; when the power loading head applies pressure to the pressure plate 2, the pressure of the power loading head is transmitted to the first loading plate 3 and the second loading plate 4 through the spring 53.

[0025] It should be noted that when the power loading head applies pressure to the pressure plate 2, the pressure plate 2 slides downward along the guide shaft 51, first compressing the spring 53 on the guide shaft 51. The elastic force of this spring 53 is transmitted to the second loading plate 4, pushing the second loading plate 4 into contact with the foundation around the pile and applying pressure. At the same time, the pressure of the pressure plate 2 is transmitted to the spring 53 outside it through the telescopic shaft 52. The elastic force of this spring 53 pushes the first loading plate 3 into contact with the top of the cement mixing pile and applies pressure. As the pressure of the power loading head gradually increases, the compression of the two springs 53 increases synchronously, causing the pressure applied by the first loading plate 3 and the second loading plate 4 to increase evenly, achieving synchronous loading of the pile top and the foundation around the pile.

[0026] See also Figure 1-Figure 3 and Figure 8 The heat-insulating temperature-control mechanism 6 includes a plurality of temperature sensors 62. It is understandable that the temperature sensor 62 is a prior art and will not be described in detail. The plurality of temperature sensors 62 are arranged at the bottom of the second loading plate 4, and the plurality of temperature sensors 62 are arranged at different depths of the foundation around the pile. A medium circulation cavity 61 is provided in the second loading plate 4. The medium circulation cavity 61 is in the shape of a spiral groove and is filled with a cooling medium. The cooling medium is driven to flow in the spiral groove to offset the heat generated when the second loading plate 4 is loaded.

[0027] It should be noted that the multiple temperature sensors 62 of the heat-insulating temperature-control mechanism 6 are arranged at the bottom of the second loading plate 4 and distributed at different depths of the foundation around the pile, enabling real-time monitoring of temperature changes in the frozen soil around the pile at different depths. A spirally grooved medium circulation chamber 61 is provided within the second loading plate 4, which is filled with a cooling medium. When the power loading head applies pressure to the first loading plate 3 and the second loading plate 4 through the connecting mechanism 5, contact friction heat is generated between the first loading plate 3 and the pile top, and between the second loading plate 4 and the foundation around the pile. This heat is transferred to the body of the second loading plate 4. At this time, an external drive device drives the cooling medium to flow continuously within the spiral groove of the medium circulation chamber 61. During the flow process, the cooling medium absorbs heat from the second loading plate 4, then flows out of the medium circulation chamber 61 carrying the heat and re-enters after cooling, forming a cycle. At the same time, the temperature sensors 62 collect temperature data of the frozen soil around the pile at different depths in real time. Based on this data, the flow rate of the cooling medium can be adjusted to ensure that the temperature increase of the frozen soil around the pile is always kept within the minimum range.

[0028] See also Figure 4-Figure 5 and Figure 8 A plurality of heat-conducting sleeves 63 are provided at the bottom of the second loading plate 4 , and the temperature sensor 62 is provided in the heat-conducting sleeve 63 ; the heat-conducting sleeve 63 is used to isolate the temperature sensor 62 from the foundation around the pile.

[0029] It should be noted that the material of the thermal sleeve 63 has good thermal conductivity, such as copper. When the second loading plate 4 contacts the foundation around the pile and applies pressure, the temperature of the foundation around the pile is transmitted to the internal temperature sensor 62 through the tube wall of the thermal sleeve 63. The temperature sensor 62 collects the temperature data in real time and is used to adjust the flow rate of the cooling medium in the medium circulation cavity 61. At the same time, the thermal sleeve 63 directly isolates the temperature sensor 62 from the foundation around the pile, preventing soil particles, moisture and other substances in the foundation around the pile from directly contacting the temperature sensor 62, preventing the temperature sensor 62 from being worn or corroded, and reducing the mechanical impact on the temperature sensor 62 during the frost heave and thaw settlement of the foundation around the pile.

[0030] See also Figure 1-Figure 2 and Figure 4The layered displacement monitoring mechanism 7 includes a plurality of second displacement sensors 71, a reflective target 72 and a third displacement sensor 73; it can be understood that the second displacement sensor 71 and the third displacement sensor 73 are both existing technologies and will not be described in detail; a plurality of second displacement sensors 71 are arranged on the top of the frame 1, and a plurality of reflective targets 72 are arranged on the first loading plate 3, and the reflective targets 72 and the second displacement sensors 71 are arranged in an upper and lower alignment; a plurality of third displacement sensors 73 are arranged at the bottom of the second loading plate 4, and a plurality of third displacement sensors 73 are arranged at different depths of the foundation around the pile, one end of the third displacement sensor 73 is connected to the second loading plate 4, and the other end of the third displacement sensor 73 is connected to the stable frozen soil layer at the bottom of the foundation around the pile.

[0031] It should be noted that when the first loading plate 3 displaces with the pile top, the reflective target 72 displaces synchronously with it. The second displacement sensor 71 monitors the change in distance between it and the reflective target 72 to acquire displacement data of the first loading plate 3, which represents the displacement data of the pile top. When the ground around the pile thaws, the second loading plate 4 displaces with it, while the other end of the third displacement sensor 73 remains stationary due to its fixed position in the stable permafrost layer. The third displacement sensor 73 monitors its own length change to acquire thaw displacement data at different depths of the ground around the pile. This data corroborates the thaw displacement detected by the data analysis unit 8, ensuring the reliability of the thaw displacement data.

[0032] See also Figure 1-Figure 5 The layered displacement monitoring mechanism 7 also includes a carbon fiber connecting rod 74 and an anchor rod 75; the movable end of the third displacement sensor 73 is connected to the second loading plate 4 through the carbon fiber connecting rod 74, and the fixed end of the third displacement sensor 73 is fixed to the stable frozen soil layer at the bottom of the foundation around the pile through the anchor rod 75.

[0033] It should be noted that the carbon fiber connecting rod 74 has good rigidity and an extremely low thermal expansion coefficient; in the low temperature environment of the plateau permafrost area, the thermal expansion coefficient of the carbon fiber connecting rod 74 is extremely low, and there will be no significant length changes due to temperature changes, thereby avoiding interference with the monitoring data of the third displacement sensor 73. When the second loading plate 4 is displaced along with the foundation around the pile, the second loading plate 4 drives the carbon fiber connecting rod 74 to displace synchronously, and the carbon fiber connecting rod 74 pushes the movable end of the third displacement sensor 73 to move, so that the third displacement sensor 73 can accurately monitor the displacement changes. The end of the anchor rod 75 is provided with a barb structure, which can tightly engage with the stable permafrost layer, ensuring that the fixed end of the third displacement sensor 73 always remains stationary and is not affected by the thawing or frost heave of the frozen soil around the pile.

[0034] See also Figure 1-Figure 2 and pictures- Figure 8The temperature conversion mechanism 81 includes an airbag 811, a piston rod 814 and a plurality of clamps 812; the airbag 811 is fixed to the frame 1 by a plurality of clamps 812, and the airbag 811 is coaxially arranged with the melting displacement average hydraulic chamber 83; the airbag 811 is filled with dry nitrogen, and the initial pressure in the airbag 811 is balanced with the ambient air pressure; the interior of the airbag 811 is connected to the interior of the heat-conducting sleeve 63 through a conduit 813; the clamps 812 are arranged at equal intervals along the axial direction of the airbag 811 to prevent the airbag 811 from undergoing radial deformation; the piston rod 814 is coaxially slidably connected to the airbag 811 through the piston head connected to one end thereof, and the other end of the piston rod 814 extends to the interior of the melting displacement average hydraulic chamber 83 and is coaxially connected to the sliding piston 84; the conduit 813 is a flexible insulation pipeline structure, which is used to transfer the temperature inside the heat-conducting sleeve 63 to the airbag 811 and allow relative displacement between the heat-conducting sleeve 63 and the airbag 811.

[0035] It should be noted that when the temperature of the foundation around the pile rises, heat is transferred to the dry nitrogen in the airbag 811 through the heat-conducting sleeve 63 and the conduit 813. The nitrogen expands due to the heat, increasing the pressure inside the airbag 811 and pushing the piston rod 814 to move axially. The other end of the piston rod 814 extends into the melting displacement averaging hydraulic chamber 83 and is coaxially connected to the sliding piston 84. The movement of the piston rod 814 drives the sliding piston 84 to slide within the melting displacement averaging hydraulic chamber 83, converting the temperature change of the foundation around the pile into the displacement of the sliding piston 84, providing a basis for calculating the melting displacement. The provision of clamp 812 ensures that airbag 811 deforms only axially, avoiding pressure loss caused by radial deformation. This allows the air pressure thrust generated by the expansion of nitrogen in airbag 811 to be efficiently transmitted to piston rod 814, improving the efficiency and accuracy of temperature-to-displacement conversion. Furthermore, airbag 811 is an elastic structure, and when a very small temperature change occurs, airbag 811 can deform to offset environmental influences. Furthermore, the provision of airbag 811 allows piston rod 814 to be driven to move within a relatively small temperature change range, such as a temperature change within a range of 0.3°C, ensuring temperature sensitivity and improving test accuracy. The flexible insulated pipe structure, conduit 813, can effectively transmit temperature while adapting to the relative displacement between thermal sleeve 63 and airbag 811, preventing damage to the pipe due to displacement and pulling. It also reduces temperature loss during the transmission process, ensuring that airbag 811 can accurately sense temperature changes in the foundation surrounding the pile. The use of dry nitrogen prevents the impact of gas condensation in low-temperature environments on the performance of airbag 811, ensuring that temperature conversion mechanism 81 maintains stable operation in the low-temperature environment of the plateau. Combined with other components of data analysis mechanism 8, this enables precise coupling of temperature and displacement, providing a reliable basis for calculating thaw-settlement displacement. This further improves the accuracy of separating thaw-settlement displacement from bearing displacement, ensuring that the test results truly reflect the bearing capacity of single-pile composite foundations and meet the needs of engineering construction in permafrost areas of the plateau.

[0036] See also Figure 1-Figure 2 and Figure 9 The displacement hydraulic transmission mechanism 82 includes a cylinder body 821 and a hydraulic push rod 822; the cylinder body 821 is fixed to the second loading plate 4, and the hydraulic push rod 822 is coaxially slidably connected to the cylinder body 821 through its end piston head, and the other end of the hydraulic push rod 822 is coaxially connected to the carbon fiber connecting rod 74; the interior of the cylinder body 821 and the piston head of the hydraulic push rod 822 are filled with oil, and the oil in the cylinder body 821 is connected to one of the chambers in the melting displacement averaging hydraulic chamber 83 through a high-pressure hose 823.

[0037] It should be noted that when the foundation around the pile undergoes melting settlement, the second loading plate 4 moves downward along with the foundation around the pile, driving the carbon fiber connecting rod 74 to move downward synchronously. The carbon fiber connecting rod 74 pushes the piston head of the hydraulic push rod 822 to slide in the cylinder 821, compressing the oil in the cylinder 821. The compressed oil flows into the corresponding chamber in the melting settlement displacement average hydraulic chamber 83 through the high-pressure hose 823, exerting a hydraulic thrust on the sliding piston 84, pushing the sliding piston 84 to slide axially along the melting settlement displacement average hydraulic chamber 83. This hydraulic thrust and the air pressure thrust applied by the temperature conversion mechanism 81 through the piston rod 814 act together on the sliding piston 84, so that the displacement of the sliding piston 84 can comprehensively reflect the temperature change of the foundation around the pile and the actual melting settlement displacement, ensuring the comprehensiveness and accuracy of the melting settlement displacement monitoring; The cooperation between the cylinder 821 and the hydraulic push rod 822 can accurately convert the displacement transmitted by the carbon fiber connecting rod 74 into hydraulic thrust. The incompressibility of the oil ensures that there is no energy loss in the process of converting displacement into thrust, thereby improving the efficiency and accuracy of displacement transmission. Combined with the temperature conversion mechanism 81 to convert the temperature, the displacement of the sliding piston 84 can comprehensively reflect the temperature changes and actual thawing and settlement conditions of the foundation around the pile, ensuring that the calculation of the thawing and settlement displacement is more comprehensive and accurate. In addition, the hydraulic transmission has good buffering characteristics, which can reduce the instantaneous impact force during the displacement transmission process, protect the thawing and settlement displacement averaging hydraulic chamber 83, sliding piston 84 and other components, extend the service life of the device, and further improve the reliability and stability of the device in field tests in plateau permafrost areas.

[0038] See also Figures 1-4An exhaust valve 85 is located at the top of the melt-sink displacement averaging hydraulic chamber 83, near the displacement hydraulic transmission mechanism 82. This valve is used to expel air from the top of the oil in the melt-sink displacement averaging hydraulic chamber 83. It should be noted that before using the device, the exhaust valve 85 is opened and the hydraulic push rod 822 of the displacement hydraulic transmission mechanism 82 is activated, allowing the oil in the cylinder 821 to flow through the high-pressure hose 823 into the corresponding chamber within the melt-sink displacement averaging hydraulic chamber 83. This inflow of oil pushes the air from the top of the oil in the melt-sink displacement averaging hydraulic chamber 83 toward the exhaust valve 85, through which the air is expelled from the melt-sink displacement averaging hydraulic chamber 83. When oil is observed flowing out of the exhaust valve 85, it indicates that the air in the melt-sink displacement averaging hydraulic chamber 83 has been completely expelled. At this point, the exhaust valve 85 is closed. During the test, no air is present in the melt-sink displacement averaging hydraulic chamber 83, and the oil pressure is stably transmitted to the sliding piston 84, ensuring that the displacement of the sliding piston 84 accurately reflects the changes in hydraulic thrust, thereby ensuring the accuracy of the melt-sink displacement monitoring.

[0039] Example 2: This example differs from Example 1 in that: Figures 1-10 A method for static load testing of a cement mixing pile single pile composite foundation, using the above-mentioned static load testing device for a cement mixing pile single pile composite foundation, specifically comprising the following steps: Step 1: Temperature control: The heat insulation and temperature control mechanism 6 removes the friction heat of the second loading plate 4, thereby reducing the temperature increase of the frozen soil around the pile. At the same time, the temperature change of the frozen soil is monitored in real time to provide a temperature basis for the calculation of thaw settlement deformation. Step 2: Displacement monitoring: Simultaneously collect the displacement of the pile top and the displacement of the frozen soil stratification around the pile, and obtain the original data of the two deformations to provide the displacement basis for subsequent separation calculation; Step 3: Conversion analysis: The temperature of the frozen soil around the pile is converted into air pressure thrust through the temperature conversion mechanism 81, providing thrust on one side for the sliding piston 84; the displacement between the stable frozen soil layer at the bottom of the foundation around the pile is converted into hydraulic thrust through the displacement hydraulic transmission mechanism 82, providing thrust on the other side for the sliding piston 84; at the same time, the displacement of the sliding piston 84 is detected by the first displacement sensor, and the displacement is determined to be thaw-settlement displacement. The displacement detected by the layered displacement monitoring mechanism 7 is marked as the total displacement, and the difference between the total displacement and the thaw-settlement displacement is calculated and marked as the bearing displacement, thereby realizing the static load test of the single pile composite foundation.

[0040] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A static load test device for a cement mixing pile single composite foundation, comprising a frame (1) with a power loading head, characterized in that: The frame (1) is provided with a pressure plate (2), a first loading plate (3) and a second loading plate (4); a connecting mechanism (5) is provided between the pressure plate (2) and the second loading plate (4); the pressure applied by the power loading head to the pressure plate (2) is transmitted to the first loading plate (3) and the second loading plate (4) through the connecting mechanism (5); the second loading plate (4) is provided with a heat insulation temperature control mechanism (6) for controlling the temperature between the second loading plate (4) and the foundation around the pile; the frame (1) is provided with a layered displacement monitoring mechanism (7) and a data analysis mechanism (8); The layered displacement monitoring mechanism (7) is used to detect the displacement of the second loading plate (4); the data analysis mechanism (8) includes: A temperature conversion mechanism (81), the temperature conversion mechanism (81) being arranged on the frame (1) and used for converting the temperature increase of the foundation around the pile into air pressure thrust; a displacement hydraulic transmission mechanism (82), the displacement hydraulic transmission mechanism (82) being arranged on the frame (1) and being used to convert the displacement between the second loading plate (4) and the stable frozen soil layer at the bottom of the foundation around the pile into a hydraulic thrust; and a melting and sinking displacement averaging hydraulic chamber (83), wherein the melting and sinking displacement averaging hydraulic chamber (83) is arranged on the frame (1), and a sliding piston (84) sliding along its axial direction is arranged in the melting and sinking displacement averaging hydraulic chamber (83), and the sliding piston (84) divides the interior of the melting and sinking displacement averaging hydraulic chamber (83) into two chambers, wherein one chamber is connected to the temperature conversion mechanism (81), and the other chamber is connected to the displacement hydraulic transmission mechanism (82); a first displacement sensor is arranged in the melting and sinking displacement averaging hydraulic chamber (83), and is used to detect the displacement of the sliding piston (84).

2. The static load test device for a cement mixing pile single composite foundation according to claim 1, characterized in that: The connecting mechanism (5) includes a telescopic shaft (52) and a plurality of guide shafts (51); the plurality of guide shafts (51) are connected to the frame (1) by sliding along their axial direction, and the ends of the plurality of guide shafts (51) are connected to the second loading plate (4); the pressure plate (2) slides axially along the guide shaft (51), and the telescopic shaft (52) is arranged between the pressure plate (2) and the first loading plate (3); springs (53) are sleeved on the guide shaft (51) and the telescopic shaft (52); when the power loading head applies pressure to the pressure plate (2), the pressure of the power loading head is transmitted to the first loading plate (3) and the second loading plate (4) through the spring (53).

3. The static load test device for a cement mixing pile single composite foundation according to claim 1, characterized in that: The heat-insulating temperature-control mechanism (6) includes a plurality of temperature sensors (62); the plurality of temperature sensors (62) are arranged at the bottom of the second loading plate (4), and the plurality of temperature sensors (62) are arranged at different depths of the foundation around the pile; a medium circulation cavity (61) is provided in the second loading plate (4), the medium circulation cavity (61) is in the shape of a spiral groove, and the medium circulation cavity (61) is filled with a cooling medium; by driving the cooling medium to flow in the spiral groove, the heat generated when the second loading plate (4) is loaded is offset.

4. The static load test device for a cement mixing pile single composite foundation according to claim 3, characterized in that: A plurality of heat-conducting sleeves (63) are provided at the bottom of the second loading plate (4), and the temperature sensor (62) is provided in the heat-conducting sleeve (63); the heat-conducting sleeve (63) is used to isolate the temperature sensor (62) from the foundation around the pile.

5. The static load test device for a cement mixing pile single composite foundation according to claim 1, characterized in that: The layered displacement monitoring mechanism (7) comprises a plurality of second displacement sensors (71), a reflective target (72) and a third displacement sensor (73); the plurality of second displacement sensors (71) are arranged on the top of the frame (1), the plurality of reflective targets (72) are arranged on the first loading plate (3), and the reflective targets (72) and the second displacement sensors (71) are arranged in an upper and lower aligned manner; the plurality of third displacement sensors (73) are arranged on the bottom of the second loading plate (4), and the plurality of third displacement sensors (73) are arranged at different depths of the foundation around the pile, one end of the third displacement sensor (73) is connected to the second loading plate (4), and the other end of the third displacement sensor (73) is connected to the stable frozen soil layer at the bottom of the foundation around the pile.

6. The static load test device for a cement mixing pile single composite foundation according to claim 5, characterized in that: The layered displacement monitoring mechanism (7) further comprises a carbon fiber connecting rod (74) and an anchor rod (75); the movable end of the third displacement sensor (73) is connected to the second loading plate (4) via the carbon fiber connecting rod (74), and the fixed end of the third displacement sensor (73) is fixed to the stable frozen soil layer at the bottom of the foundation around the pile via the anchor rod (75).

7. The static load test device for a cement mixing pile single composite foundation according to claim 4, characterized in that: The temperature conversion mechanism (81) includes an airbag (811), a piston rod (814) and a plurality of clamps (812); the airbag (811) is fixed to the frame (1) through the plurality of clamps (812), and the airbag (811) is coaxially arranged with the melting displacement average hydraulic chamber (83); the airbag (811) is filled with dry nitrogen, and the initial pressure in the airbag (811) is balanced with the ambient air pressure; the interior of the airbag (811) is connected to the interior of the heat-conducting sleeve (63) through the conduit (813); the clamps (812) are arranged at equal intervals along the axial direction of the airbag (811) to prevent the airbag (811) from undergoing radial deformation; the piston rod (814) is coaxially slidably connected to the airbag (811) through the piston head connected to one end thereof, and the other end of the piston rod (814) extends to the interior of the melting displacement average hydraulic chamber (83) and is coaxially connected to the sliding piston (84); The conduit (813) is a flexible heat-insulating pipeline structure, and the flexible heat-insulating pipeline is used to transfer the temperature inside the heat-conducting sleeve (63) to the airbag (811), and allows relative displacement between the heat-conducting sleeve (63) and the airbag (811).

8. The static load test device for a cement mixing pile single composite foundation according to claim 6, characterized in that: The displacement hydraulic transmission mechanism (82) includes a cylinder body (821) and a hydraulic push rod (822); the cylinder body (821) is fixed to the second loading plate (4), the hydraulic push rod (822) is coaxially slidably connected to the cylinder body (821) through its end piston head, and the other end of the hydraulic push rod (822) is coaxially connected to the carbon fiber connecting rod (74); the interior of the cylinder body (821) and the space between the piston head of the hydraulic push rod (822) are filled with oil, and the oil in the cylinder body (821) is connected to one of the chambers in the melting displacement averaging hydraulic chamber (83) through a high-pressure hose (823).

9. The static load test device for a cement mixing pile single composite foundation according to claim 8, characterized in that: An exhaust valve (85) is provided at the top of the melt-sink displacement averaging hydraulic chamber (83) near the displacement hydraulic transmission mechanism and is used to exhaust air existing at the top of the oil in the melt-sink displacement averaging hydraulic chamber (83).

10. A static load test method for a single cement mixing pile composite foundation, characterized by: The static load test device for a cement mixing pile single pile composite foundation according to any one of claims 1 to 9 is used; specifically comprising the following steps: Step 1, temperature control: take away the friction heat of the second loading plate (4) through the heat insulation temperature control mechanism (6), reduce the temperature increase of the frozen soil around the pile, and monitor the temperature change of the frozen soil in real time to provide a temperature basis for the calculation of thaw deformation; Step 2: Displacement monitoring: Simultaneously collect the displacement of the pile top and the displacement of the frozen soil stratification around the pile, and obtain the original data of the two deformations to provide the displacement basis for subsequent separation calculation; Step 3, conversion analysis: The temperature of the frozen soil around the pile is converted into a gas pressure thrust through the temperature conversion mechanism (81), providing a thrust on one side for the sliding piston (84); the displacement between the stable frozen soil layer at the bottom of the foundation around the pile is converted into a hydraulic thrust through the displacement hydraulic transmission mechanism (82), providing a thrust on the other side for the sliding piston (84); at the same time, the displacement of the sliding piston (84) is detected by the first displacement sensor, and the displacement is determined to be a thaw displacement. The displacement detected by the layered displacement monitoring mechanism (7) is marked as a total displacement, and the difference between the total displacement and the thaw displacement is calculated and marked as a bearing displacement, thereby realizing a static load test of a single pile composite foundation.

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