A low stress shear instrument for pipe-soil interface considering the coupling effect of temperature and strain rate

Abstract

The invention provides a low stress shear instrument for pipe-soil interface considering the coupling effect of temperature and strain rate, comprising a shear instrument body, a lateral pressure control module, a temperature control module and a shear control module; the normal boundary condition of the shear instrument body is mainly controlled by a pressure water bag arranged along the wall of the shear instrument body, the pressure water bag is communicated with the low stress lateral pressure control module, and the normal boundary control is realized by feedback of displacement and force signals, so that the low stress lateral force can be accurately applied; the torsion shear barrel controls the shear rate, shear cycle and shear amplitude through a servo motor, so that large deformation shearing effect of the interface can be realized under different strain rates, so as to realize soil strain rate-shear test and soil cyclic shear test; there is a cavity in the torsion shear barrel connected to the external temperature control module, and the interface temperature is controlled by water bath heating, so as to realize the soil temperature-shear test.

Description

Technical Field

[0001] The invention relates to a pipe-soil interface low stress shearing instrument taking into account the temperature strain rate coupling effect. Background Art

[0002] With the improvement of human industrial level, the global oil and gas exploration area has been expanding, and a trend of development towards the deep sea has been formed. In recent years, nearly half of the world's major oil and gas discoveries have been in the deep sea. my country has discovered a large amount of oil and gas reserves in the Bohai Sea, the East China Sea, and the South China Sea. Among them, the South China Sea is one of the world's four major oil and gas gathering places.

[0003] Submarine pipelines are an important part of the deep-sea oil and gas production system and play an important role in transporting oil and gas. They have the characteristics of high construction investment, long laying distance, deep working water depth, harsh service environment, and difficult monitoring and maintenance. Considering that various underwater production equipment are connected to them, if the submarine pipelines suffer serious instability during service, it may lead to a series of thorny problems such as oil field shutdown, complex and expensive underwater maintenance, etc. If they occur frequently, it will lead to the deterioration of the marine ecology and have a negative social impact.

[0004] Shallow soils in coastal areas of my country are mostly soft clays. Changes in the engineering properties of soft clays will affect the pipe-soil interaction force, and thus affect the overall buckling mode, critical buckling temperature, buckling amplitude and buckling length of the pipeline. The pipeline is in a dynamic process during instability, so it is necessary to consider the effect of strain rate on the pipe-soil interaction force. In addition, oil and gas in pipelines are transported at high temperature and high pressure, and heat will be dissipated into the surrounding soil during transportation, thereby changing the temperature field of the surrounding soil, thereby changing the engineering properties of the soil and affecting the pipe-soil interaction force.

[0005] At present, the temperature and strain rate effects of soft clay have received attention and importance from scholars and engineering circles at home and abroad, but there is a lack of mature calculation theories and design criteria in the design of submarine pipelines. Therefore, it is urgent to study the physical mechanism of pipe-soil interaction considering the temperature and strain rate coupling effects of soft clay, so as to provide the necessary scientific basis for the design and safe operation of submarine pipelines in my country.

[0006] Based on the above background, in order to better study the influence of strain rate-shear and temperature-shear on interface shear behavior under ground stress, the present invention proposes a pipe-soil interface low stress shear instrument considering the temperature-strain rate coupling effect. Summary of the invention

[0007] The object of the present invention is to provide a pipe-soil interface low stress shear instrument taking into account the temperature strain rate coupling effect in view of the deficiencies in the prior art.

[0008] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A pipe-soil interface low stress shearing instrument considering the temperature-strain-rate coupling effect, comprising a shearing instrument body, characterized in that: the pipe-soil interface low stress shearing instrument considering the temperature-strain-rate coupling effect also comprises a temperature control module, a shearing control module, and a low stress lateral force control module;

[0010] The shearing instrument body comprises a torsion shear barrel, a torsion shear barrel partition, a model barrel cover, a model barrel bottom plate, a model barrel, a water bag pressure plate, a pressure water bag, and a water bag water inlet;

[0011] The torsion shear barrel runs through the entire model barrel from top to bottom; a torsion shear barrel partition is arranged in the torsion shear barrel, and the torsion shear barrel partition separates the inner cavity of the torsion shear barrel to form a water inlet cavity and a water outlet cavity, the lower ends of the water inlet cavity and the water outlet cavity are connected, and the upper ends of the water inlet cavity and the water outlet cavity are respectively connected to the water inlet pipe and the water outlet pipe of the water tank; the other ends of the water inlet pipe and the water outlet pipe of the water tank are respectively connected to the temperature control module; a plurality of temperature sensors and at least one pore pressure sensor are arranged on the outer surface of the torsion shear barrel; the temperature sensor is an interface temperature sensor, which is symmetrically arranged on the outer surface of the torsion shear barrel to verify the uniformity of the temperature at the steel-clay interface in the model barrel, and the temperature control range is 5-80°C; the pore pressure sensor is used to determine the development law of the pore pressure at the interface during the test, and the pore pressure accuracy is 0.5 kPa;

[0012] The top of the model barrel is provided with a model barrel cover, and a pressure water bag is arranged in the model barrel, and the pressure water bag surrounds the torsion shear barrel to form lateral pressure on the torsion shear barrel, and the water bag water inlet of the pressure water bag is connected with the low stress lateral force control module, and the low stress lateral force control module is used to control the increase of pressure in the pressure water bag or the release of pressure; the model barrel cover is provided with a plurality of drainage ports;

[0013] The lower end of the torsion shear barrel passes through the bottom plate of the model barrel and is connected to a shear control module, and the shear control module is used to control the torsion of the torsion shear barrel in the clay.

[0014] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0015] As a preferred technical solution of the present invention: the low stress lateral force control module includes a lateral pressure servo motor, a lateral pressure bracket, a ball screw, a transmission plate, a piston push rod, a water pressure chamber, a piston cylinder, a piston plate, a guide column, and a water inlet pipeline;

[0016] One end of the ball screw is connected to the side pressure servo motor, and the other end of the ball screw passes through the transmission plate. A plurality of guide columns are arranged in the side pressure bracket, and the guide columns pass through the transmission plate and form a movement track of the transmission plate. The transmission plate is provided with a piston push rod on the side opposite to the side pressure servo motor.

[0017] The piston push rod is inserted into the piston cylinder, and the piston cylinder has a piston plate and a water pressure chamber for the compression space or release space required by the piston plate, and the other end of the piston push rod is fixed to the piston plate; the water pressure chamber is filled with water, and the water pressure chamber is connected to the water inlet pipe, and the other end of the water inlet pipe is connected to the pressure water bag.

[0018] As a preferred technical solution of the present invention: the lateral pressure range of the low-stress lateral force control module applied to the soil in the model bucket is 0~50 kPa.

[0019] As a preferred technical solution of the present invention: a linear bearing is provided between the guide column and the transmission plate.

[0020] As a preferred technical solution of the present invention: a screw nut is provided at the connection between the transmission plate and the ball screw, and the screw nut matches the external thread of the roller screw.

[0021] As a preferred technical solution of the present invention: the temperature control module includes a temperature controller and a water tank.

[0022] The temperature controller is used to control the temperature of circulating water in the water tank, and the water tank is respectively connected to a water tank water inlet pipe and a water tank water outlet pipe.

[0023] As a preferred technical solution of the present invention: the shear control module includes a torque sensor, a reducer fixing plate, a servo reducer and a shear servo motor;

[0024] One end of the reducer fixing plate is connected to the servo reducer, and the other end is used to fix the lower end of the torsion shear barrel;

[0025] The other end of the servo reducer is connected to the shearing servo motor.

[0026] As a preferred technical solution of the present invention: the shear torque provided by the shear control module is 0-50 kN·m.

[0027] As a preferred technical solution of the present invention: the temperature control module, the shear control module, and the low-stress lateral force control module are all connected to a computer and controlled by the computer.

[0028] As a preferred technical solution of the present invention: the diameter of the model barrel is 40 cm, the height is 10 cm, and the diameter of the torsion shear barrel is 10 cm.

[0029] As a preferred technical solution of the present invention: there are two drain outlets, which are used to discharge water seeping out during the test. The two drain outlets are symmetrically arranged, and both of the drain outlets are embedded with small-aperture permeable stones and geotextiles to avoid the loss of clay particles.

[0030] As a preferred technical solution of the present invention: a water stop strip is provided at the contact point between the model barrel cover and the torsion shear barrel to prevent muddy water from seeping out.

[0031] The invention provides a pipe-soil interface low stress shear instrument considering the temperature-strain rate coupling effect, comprising a shear instrument body, a lateral pressure control module, a temperature control module and a shear control module; the shear instrument body can realize the interface shear test under the normal boundary of constant stress by utilizing two sets of servo systems, namely annular and radial systems; the normal boundary condition of the shear instrument body is mainly controlled by a pressure water bag arranged along the wall of the shear instrument body, the pressure water bag is communicated with the low stress lateral pressure control module, and the normal boundary control is realized by feedback of displacement and force signals, so that the low stress lateral force can be accurately applied; the torsion shear barrel controls the shear rate, shear cycle and shear amplitude through a servo motor, so that the large deformation shear effect of the interface under different strain rates can be realized, and the soil strain rate-shear test and soil cyclic shear test can be realized; there is a cavity in the torsion shear barrel connected to the external temperature control module, and the interface temperature is controlled by water bath heating, so as to realize the soil temperature-shear test; the shear instrument provided by the invention can not only realize the normal boundary of constant stress under low stress, but also consider the temperature-shear effect, the strain rate-shear effect, the large deformation-shear effect and the cyclic shear effect. It can be used to study and reveal the influence mechanism of seabed soil temperature and rate effect on the "axial soil resistance-axial displacement" of deep-sea pipelines under low stress levels, and to interpret the axial action mechanism of the pipe-soil unit throughout the service process of deep-sea pipelines.

[0032] The low stress shear instrument for pipe-soil interface considering the temperature-strain rate coupling provided by the present invention explores the influence of temperature and strain rate on interface strength under low stress, can simulate the large axial displacement shear and cyclic shear of pipe-soil during the service of deep-sea pipelines, and can simulate the influence mechanism of the shear strength of the pipe-soil axial interface under the temperature-strain rate coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is an overall diagram of the pipe-soil interface low stress shear instrument provided by the present invention taking into account the temperature strain rate coupling effect;

[0034] Figure 2 is an internal cross-sectional view of a low stress lateral force control module;

[0035] Figure 3 It is a diagram of a torsion shear barrel;

[0036] Figure 4 is a diagram of a shear control module;

[0037] Figure 5 is a diagram of the temperature control module;

[0038] Figure 6Graphical representation of each module integration;

[0039] In the figure: 1-torsion shear barrel; 2-torsion shear barrel partition; 3-drain outlet; 4-water bag pressure plate; 5-water bag; 6-model barrel; 7-model barrel bottom plate; 8-speed reducer fixing plate; 9-servo speed reducer; 10-bracket; 11-shear servo motor; 12-temperature controller; 13-water bag water inlet; 14-water tank water inlet pipe; 15-water tank water outlet pipe; 16-side pressure servo motor; 17-side pressure bracket; 18-ball screw; 19-screw nut ; 20-transmission plate; 21-piston push rod; 22-water pressure chamber; 23-model barrel cover; 24-piston cylinder; 25-piston plate; 26-guide column; 27-linear bearing; 28-temperature sensor; 29-pore pressure sensor; 30-water tank; 31-shear instrument body; 32-temperature control module; 33-shear control module; 34-low stress lateral force control module; 35-computer; 36-water inlet pipeline; 37-torque sensor. DETAILED DESCRIPTION

[0040] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] A low stress shear instrument for pipe-soil interface considering the temperature strain rate coupling effect, comprising a shear instrument body 31, a temperature control module 32, a shear control module 33, and a low stress lateral force control module 34;

[0042] The bracket 10 is used to support the shearing instrument body 31 upwards;

[0043] like Figure 1 As shown, the shearing instrument body 31 includes a torsion shear barrel 1, a torsion shear barrel partition 2, a model barrel cover 23, a model barrel bottom plate 7, a model barrel 6, a water bag pressure plate 4, a pressure water bag 5, and a water bag water inlet 13.

[0044] Two drain ports 3 are symmetrically arranged on the model barrel cover 23, and the drain ports 3 are 10 cm away from the side wall of the model barrel cover 6. The diameter of the model barrel is 40 cm, and the diameter of the torsion shear barrel is 10 cm. The position of the drain hole is 5 cm away from the torsion shear barrel. When the soil in the container is filled, whether it is a sand test or a clay test, the pressure water bag will not squeeze to this position, preventing the drain port 3 from being blocked due to the expansion of the pressure water bag 5 during the process of increasing the lateral pressure. Since the soil types targeted by the test device include fine-grained soils such as clay, in order to prevent the loss of soil particles during the test, the drain ports 3 are embedded with small-diameter permeable stones and geotextiles. A water stop is arranged at the contact point between the model barrel cover and the torsion shear barrel 1 in the center to prevent mud and water from seeping out.

[0045] The torsion shear barrel 1 is provided with a torsion shear barrel partition 2, and the cavities on both sides of the torsion shear barrel partition 2 are respectively connected to the water tank water inlet pipe 14 and the water tank water outlet pipe 15. The torsion shear barrel 1 is connected to the shear control module 33 below, and the shear control module 33 controls the torsion shear barrel 6 to twist at different rates, different directions and different shear amplitudes in the model barrel 6 through the shear servo motor 11 to achieve different experimental requirements. The water tank water inlet pipe 14 and the water tank water outlet pipe 15 are connected to the temperature control module 32, and the temperature control module 32 injects water of different temperatures into the torsion shear barrel 1 through the water tank water inlet pipe 14, so as to achieve the temperature control of the interface of the torsion shear barrel 1 through the water bath. Four temperature sensors 28 and a pore pressure sensor 29 are symmetrically arranged on the outer surface of the torsion shear barrel 1. The temperature sensor 28 can be used to measure the temperature at the interface to verify the uniformity of the temperature at the interface during the test, and its accuracy is 1°C; the pore pressure sensor 29 is used to measure the pore pressure development at the interface during the test, and its accuracy is 0.5 kPa. A water bag pressure plate 4 is placed on the pressure water bag 5 and is arranged circumferentially along the side wall of the model barrel 6. The water bag pressure plate 4 is an annular cover plate with the same width as the side wall of the model barrel 6. It is arranged between the model barrel cover 23 and the side wall of the model barrel 6 and is used to fix the pressure water bag 5. The pressure water bag 5 is connected to the low stress lateral force control module 34 through the water bag water inlet 13. The low stress lateral force control module 34 receives the signal input by the computer 35, injects water into the pressure water bag 5 and can control the water pressure in the pressure water bag 5.

[0046] The low stress lateral force control module 34 includes a lateral pressure servo motor 16, a lateral pressure bracket 17, a ball screw 18, a screw nut 19, a transmission plate 20, a piston push rod 21, a water pressure chamber 22, a piston cylinder 24, a piston plate 25, a guide column 26, a linear bearing 27, and a water inlet pipeline 36. The lateral pressure servo motor 16 is connected to the ball screw 18. The ball screw 18 is connected to the transmission plate 20 through the screw nut 19. The guide column 26 is located inside the lateral pressure bracket 17 and is interlocked with the transmission plate 20, and the transmission plate 20 can move vertically along the guide column 26. The lower side of the transmission plate 20 is connected to the piston push rod 21. The piston push rod 21 is connected to the piston plate 25. The piston plate 25 can move vertically in the piston cylinder 24. There is a water pressure chamber 22 in the piston cylinder 24. The water pressure chamber 22 is filled with clean water, and the lower part is connected with the water inlet pipeline 36. The water inlet pipe 36 is connected to the pressure water bag 5 in the shearing instrument body. The hydraulic servo motor 16 can control the transmission plate 20 on the ball screw 18 to move up and down along the guide column 26. When the transmission plate 20 moves downward, the water in the water pressure chamber 22 is pressed into the pressure water bag 5, so that the water pressure in the pressure water bag 5 increases, that is, the lateral pressure increases; when the transmission plate 20 moves upward, the water in the pressure water bag 5 flows back to the water pressure chamber 22, and the water pressure in the pressure water bag 5 decreases, that is, the lateral pressure decreases. The water pressure control range of the low stress lateral force control module 34 is 0-50kPa.

[0047] The temperature control module 32 includes a temperature controller 12 and a water tank 30; the temperature controller 12 is used to control the temperature of the circulating water in the water tank 30;

[0048] The shear control module 33 includes a torque sensor 37, a reducer fixing plate 8, a servo reducer 9, and a shear servo motor 11. The shear servo motor 11 outputs the torsional displacement to the servo reducer 9, and the servo reducer 9 further adjusts the torsional displacement input by the shear servo motor 11 and outputs it, driving the model barrel 6 to rotate at a set rate. The reducer fixing plate 8 is used to fix the servo reducer.

[0049] The shear control module 33, the low stress lateral force control module 34, and the temperature control module 32 are integrated in a computer 35 for control;

[0050] When conducting the soil temperature-shear test, pour the pre-prepared mud into the model barrel 6 and cover the model barrel cover 23. Connect the water inlet 13 of the pressure water bag to the water inlet pipeline 36, inject water into the water pressure chamber 22 to ensure that there is sufficient water in the water pressure chamber 22, turn on the lateral pressure servo motor 16 of the low stress lateral force control module 34, input the required lateral pressure value through the computer 35, and the range of the lateral pressure value is 0-50 kPa. The lateral pressure servo motor 16 drives the transmission plate 20 to move downward along the guide column 26, and presses water from the water pressure chamber 22 into the pressure water bag 5, so that the water pressure in the pressure water bag 5 increases. After the lateral pressure reaches the requirement, connect the water tank water inlet pipe 14 and the water tank water outlet pipe 15 to the temperature control module 32, turn on the temperature control module 32, input the required temperature through the computer 35, and the temperature range is 5-80°C. The temperature control module 32 injects water at the required temperature into the torsion shear barrel 1, and controls the temperature at the interface through a water bath. By turning on the shear servo motor 11 of the shear control module 33 to perform interface shearing, the shear behavior of the interface between soil and structure under constant temperature can be investigated, and the change of the shear behavior of the interface between soil and structure after temperature cycling can be investigated.

[0051] When conducting soil strain rate-shear tests, in addition to the above steps, the required shear rate is input through the computer, and the servo motor is controlled to control the torsion shear barrel to twist at the required speed in the clay. The interface shear behavior of soil and structure under different shear rates can be explored.

[0052] When conducting a soil cyclic shear test, in addition to the above steps, the required shear cycle, shear direction, and shear amplitude are input through the computer to control the servo motor to control the torsion shear barrel to twist in the clay in the required cyclic shear. Cyclic shear can be controlled by force or by displacement. The shear behavior of the interface between soil and structure under force or displacement cyclic shear can be explored.

[0053] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A low stress shear instrument for pipe-soil interface considering the coupling effect of temperature strain rate, comprising a shear instrument body, characterized in that: The pipe-soil interface low stress shear instrument considering the temperature strain rate coupling effect also includes a temperature control module, a shear control module, and a low stress lateral force control module; The shearing instrument body comprises a torsion shear barrel, a torsion shear barrel partition, a model barrel cover, a model barrel bottom plate, a model barrel, a water bag pressure plate, a pressure water bag, and a water bag water inlet; The torsion shear barrel runs through the entire model barrel from top to bottom; a torsion shear barrel partition is arranged inside the torsion shear barrel, and the torsion shear barrel partition separates the inner cavity of the torsion shear barrel to form a water inlet cavity and a water outlet cavity, the lower ends of the water inlet cavity and the water outlet cavity are connected, and the upper ends of the water inlet cavity and the water outlet cavity are respectively connected to the water inlet pipe and the water outlet pipe of the water tank; the other ends of the water inlet pipe and the water outlet pipe of the water tank are respectively connected to the temperature control module; a plurality of temperature sensors and at least one pore pressure sensor are arranged on the outer surface of the torsion shear barrel; The top of the model barrel is provided with a model barrel cover, and a pressure water bag is arranged in the model barrel, and the pressure water bag surrounds the torsion shear barrel to form lateral pressure on the torsion shear barrel, and the water bag water inlet of the pressure water bag is connected with the low stress lateral force control module, and the low stress lateral force control module is used to control the increase of pressure in the pressure water bag or the release of pressure; the model barrel cover is provided with a plurality of drainage ports; The lower end of the torsion shear barrel passes through the bottom plate of the model barrel and is connected to a shear control module, and the shear control module is used to control the torsion of the torsion shear barrel in the clay; The low stress lateral force control module includes a lateral pressure servo motor, a lateral pressure bracket, a ball screw, a transmission plate, a piston push rod, a water pressure chamber, a piston cylinder, a piston plate, a guide column, and a water inlet pipeline; One end of the ball screw is connected to the side pressure servo motor, and the other end of the ball screw passes through the transmission plate. A plurality of guide columns are arranged in the side pressure bracket, and the guide columns pass through the transmission plate and form a movement track of the transmission plate. The transmission plate is provided with a piston push rod on the side opposite to the side pressure servo motor. The piston push rod is inserted into the piston cylinder, and the piston cylinder has a piston plate and a water pressure chamber for compressing or releasing the space required by the piston plate, and the other end of the piston push rod is fixed to the piston plate; the water pressure chamber is filled with water, and the water pressure chamber is connected to the water inlet pipeline, and the other end of the water inlet pipeline is connected to the pressure water bag; The shear control module includes a torque sensor, a reducer fixing plate, a servo reducer and a shear servo motor; One end of the reducer fixing plate is connected to the servo reducer, and the other end is used to fix the lower end of the torsion shear barrel; The other end of the servo reducer is connected to the shearing servo motor.

2. The pipe-soil interface low stress shearing instrument considering the temperature strain rate coupling effect according to claim 1, characterized in that: A linear bearing is arranged between the guide column and the transmission plate.

3. The pipe-soil interface low stress shear instrument considering the temperature strain rate coupling effect according to claim 1, characterized in that: A screw nut is provided at the connection between the transmission plate and the ball screw, and the screw nut matches the external thread of the roller screw.

4. The pipe-soil interface low stress shear instrument considering the temperature strain rate coupling effect according to claim 1, characterized in that: The temperature control module includes a temperature controller and a water tank. The temperature controller is used to control the temperature of circulating water in the water tank, and the water tank is respectively connected to a water tank water inlet pipe and a water tank water outlet pipe.

5. The pipe-soil interface low stress shear instrument considering the temperature strain rate coupling effect according to claim 1, characterized in that: The temperature control module, the shear control module, and the low-stress lateral force control module are all connected to a computer and controlled by the computer.

6. The pipe-soil interface low stress shear instrument considering the temperature strain rate coupling effect according to claim 1, characterized in that: There are two drainage outlets, which are arranged symmetrically, and each of the drainage outlets is embedded with small-aperture permeable stones and geotextiles.

7. The pipe-soil interface low stress shearing instrument considering the temperature-strain rate coupling effect according to claim 1, characterized in that: A water stop strip is arranged at the contact point between the model barrel cover and the torsion shear barrel.

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