Shield main driving structure and sealing regulation and control method

Abstract

The application provides a shield main driving structure and a sealing regulation and control method, and the shield main driving structure comprises a sealing runway, a wear-resistant steel belt, a steel belt sealing ring and a pressure boosting device, the wear-resistant steel belt is installed at the outer periphery of the sealing runway, the sealing runway is provided with a steel belt sealing groove, the steel belt sealing ring is arranged in the steel belt sealing groove, and the steel belt sealing ring is located between the sealing runway and the wear-resistant steel belt; a pressure boosting groove is arranged on the side of the steel belt sealing ring away from the wear-resistant steel belt, the pressure boosting device is in communication with the pressure boosting groove and is used for conveying pressure medium to the pressure boosting groove, and the problems that the assembly precision of the sealing runway and the wear-resistant steel belt of the shield main driving structure is poor and leakage is prone to occur due to insufficient compression amount in the running process are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of a shield machine, in particular to a shield main drive structure and a sealing regulation method. BACKGROUND

[0002] In order to improve the wear resistance of the main drive sealing runway of the shield machine, a wear-resistant steel belt needs to be installed on the end face, and an O-ring needs to be used to seal the gear oil of the drive box between the runway and the wear-resistant belt. At present, there are mainly the following three problems: (1) the wear-resistant steel belt and the sealing runway are both large in diameter, and the compression amount of the O-ring used in this structure is usually about 1mm. If there is a problem of poor assembly size precision during the installation process, the gear oil of the drive box may leak from the gap between the wear-resistant steel belt and the runway during use; (2) the operating environment temperature of the shield machine is generally about 40 degrees, and the heat generated by the friction between the lip seal and the wear-resistant steel belt may be more. The thermal expansion coefficient of the wear-resistant steel belt is generally 1.39x10-5, which causes the wear-resistant steel belt to expand due to heat, the inner diameter size expands outward, and the compression amount of the O-ring and the wear-resistant steel belt decreases, which may cause the gear oil of the drive box to leak; (3) if the compression amount of the O-ring is increased, the rubber will be permanently deformed due to the large compression, which is not conducive to long-term use.

[0003] In order to compensate for the sealing compression amount, some use a locking mechanism to solve the compression amount compensation, some use the thermal expansion of metal materials to compensate for the compression amount, and some use the supporting action of metal materials to ensure that the compression amount does not change greatly. For example, the utility model patent 201721862492.0 discloses a fixed ball valve and a sealing compensation structure thereof, which uses a metal retainer ring to compensate for the compression amount, but cannot avoid the plastic deformation of the metal, and cannot achieve accurate compensation for long-term use. These sealing compression amount compensation schemes can achieve good results for small sealing structures. However, for large-diameter sealing structures, the results are not good, especially for the structure of the main drive of the shield machine, it is difficult to effectively compensate for the sealing compression amount, and the space and conditions for improving the structure of the main drive of the shield machine are very limited, and it is difficult to add a compensation structure. SUMMARY

[0004] The purpose of the present application is to provide a shield main drive structure and a sealing regulation method to solve the problem of poor assembly precision between the sealing runway and the wear-resistant steel belt of the shield main drive structure, and the problem of leakage due to insufficient compression amount during operation.

[0005] The above-mentioned purpose of the present application can be realized by using the following technical scheme:

[0006] The application provides a shield main driving structure, which comprises a sealing track, a wear-resistant steel belt, a steel belt sealing ring and a pressurizing device, the wear-resistant steel belt is installed on the outer periphery of the sealing track, the sealing track is provided with a steel belt sealing groove, the steel belt sealing ring is arranged in the steel belt sealing groove, and the steel belt sealing ring is located between the sealing track and the wear-resistant steel belt.

[0007] The side of the steel belt sealing ring away from the wear-resistant steel belt is provided with a pressurizing groove, the pressurizing device is in communication with the pressurizing groove, and the pressurizing device is used for conveying pressure medium to the pressurizing groove.

[0008] In a preferred embodiment, the steel belt sealing groove has a groove bottom surface, the sealing track is provided with a conveying hole in communication with the pressurizing device, the conveying hole extends to the groove bottom surface, the steel belt sealing ring comprises a first protruding part and a second protruding part, the pressurizing groove is formed between the first protruding part and the second protruding part, and the first protruding part and the second protruding part both extend to the groove bottom surface.

[0009] In a preferred embodiment, the side wall of the steel belt sealing groove is inclined to the inside of the groove in a radially outward direction.

[0010] In a preferred embodiment, the inclination angle of the side wall of the steel belt sealing groove ranges from 8° to 20°.

[0011] In a preferred embodiment, a spring is arranged in the pressurizing groove, and the spring can exert a radially outward spring force on the steel belt sealing ring.

[0012] In a preferred embodiment, the pressurizing device comprises a conveying pipeline and a flow adjusting mechanism arranged on the conveying pipeline.

[0013] In a preferred embodiment, the conveying pipeline is provided with a pressure sensor, the sealing track is provided with a temperature sensor, and the shield main driving structure comprises an adjusting controller, and the temperature sensor and the flow adjusting mechanism are both electrically connected with the adjusting controller.

[0014] The application provides a sealing regulation method, which is applied to the shield main driving structure, and the sealing regulation method comprises the following steps: when the wear-resistant steel belt is heated and expanded, the pressurizing device conveys pressure medium to the pressurizing groove.

[0015] In a preferred embodiment, the following steps are further included: establishing a model between the temperature, the pressure of the pressure medium conveyed by the pressurizing device and the supporting reaction force of the steel belt sealing ring, and controlling the pressure of the pressure medium conveyed by the pressurizing device according to the model.

[0016] In the preferred embodiment, the difference between the support reaction force in the normal state and the support reaction force after the pressure medium is applied is ≤10% of the support reaction force in the normal state, and the support reaction force in the normal state > the support reaction force after the pressure medium is applied.

[0017] The features and advantages of the present application are:

[0018] When the wear-resistant steel belt is heated and expanded, the pressure boosting device delivers the pressure medium to the pressure boosting groove, the pressure medium is filled in the pressure boosting groove, and the steel belt sealing ring compensates the gap between the wear-resistant steel belt and the sealing track in the radial direction under the pressure, so as to compensate the insufficient sealing compression amount, ensure the sealing between the wear-resistant steel belt and the sealing track, and solve the problems of poor assembly precision between the sealing track of the main driving structure of the shield and the wear-resistant steel belt and easy leakage due to insufficient compression amount in the running process. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A schematic diagram of the sealing track of the main driving structure of the shield is provided.

[0021] Figure 2 A schematic diagram of an embodiment of the sealing structure in the main driving structure of the shield is provided.

[0022] Figure 3 A schematic diagram of another embodiment of the sealing structure in the main driving structure of the shield is provided.

[0023] Figure 4 A schematic diagram of the steel belt sealing ring in the main driving structure of the shield is provided.

[0024] Figure 5 A schematic diagram of the pressure boosting device in the main driving structure of the shield is provided.

[0025] Explanation of reference numerals:

[0026] 1, wear-resistant steel belt; 10, sealing track; 11, first pressure ring; 12, lip seal; 13, first spacer ring; 14, second spacer ring; 15, third spacer ring; 16, second pressure ring;

[0027] 2, steel belt sealing ring; 21, pressure boosting groove; 221, first protruding part; 222, second protruding part;

[0028] 3. Pressure sensor; 4. Flow regulation mechanism; 5. Temperature sensor; 8. Host computer;

[0029] 9. Supply system; 91. Delivery pipeline;

[0030] 6. Conveying port;

[0031] 7. Steel strip sealing groove;

[0032] 711. The bottom surface of the groove; 712. The side wall of the steel strip sealing groove.

[0033] 72. Spring. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Option 1

[0036] This invention provides a shield tunneling main drive structure, such as Figures 1-3 As shown, the main drive structure of the tunnel boring machine includes: a sealed runway 10, a wear-resistant steel belt 1, a steel belt sealing ring 2, and a pressurizing device. The wear-resistant steel belt 1 is installed on the outer periphery of the sealed runway 10. The sealed runway 10 is provided with a steel belt sealing groove 7. The steel belt sealing ring 2 is disposed in the steel belt sealing groove 7 and is located between the sealed runway 10 and the wear-resistant steel belt 1. A pressurizing groove 21 is provided on the side of the steel belt sealing ring 2 away from the wear-resistant steel belt 1. The pressurizing device is connected to the pressurizing groove 21 and is used to deliver pressure medium to the pressurizing groove 21. When the wear-resistant steel belt 1 expands due to heat, the pressurizing device delivers a pressure medium to the pressurizing groove 21. The pressure medium fills the pressurizing groove 21, and under the action of pressure, the steel belt sealing ring 2 compensates for the gap between the wear-resistant steel belt 1 and the sealing runway 10 in the radial direction to make up for the insufficient sealing compression, thus ensuring the seal between the wear-resistant steel belt 1 and the sealing runway 10. This solves the problem of poor assembly accuracy between the sealing runway and the wear-resistant steel belt in the shield tunnel main drive structure, which easily leads to insufficient compression and leakage during operation.

[0037] Figure 1The local structure of the sealing track 10, the wear-resistant steel belt 1 and the steel belt sealing ring 2 is shown, the sealing track 10 and the wear-resistant steel belt 1 are both in the shape of a cylinder as a whole, the steel belt sealing ring 2 is in the shape of a ring as a whole, and the center lines of the sealing track 10, the wear-resistant steel belt 1 and the steel belt sealing ring 2 substantially coincide. In order to better improve the sealing effect, the inventor has made further improvements: the steel belt sealing groove 7 has a groove bottom surface 711, the sealing track 10 is provided with a conveying hole 6 in communication with the supercharging device, the conveying hole 6 extends to the groove bottom surface 711; the steel belt sealing ring 2 comprises a first protruding portion 221 and a second protruding portion 222, a supercharged groove 21 is formed between the first protruding portion 221 and the second protruding portion 222, the first protruding portion 221 and the second protruding portion 222 both extend to the groove bottom surface 711, and the opening of the supercharged groove 21 is radially inward. The first protruding portion 221 and the second protruding portion 222 are respectively matched with the groove bottom surface 711 and the side wall 712 of the steel belt sealing groove, and under the action of the pressure medium filled in the supercharged groove 21, the sealing reliability is improved. Specifically, the conveying hole 6 extends from the inner wall of the sealing track 10 to the groove bottom surface 711 of the steel belt sealing groove 7.

[0038] Further, the side wall 712 of the steel belt sealing groove is inclined inwardly in the radial direction, the steel belt sealing ring 2 is deformed and displaced under the action of the pressure medium, and can better seal with the side wall 712 of the steel belt sealing groove. The steel belt sealing groove 7 adopts a narrow mouth design and is in the shape of a trapezoid, the steel belt sealing ring 2 is deformed after being subjected to internal pressure, so that the two sides of the steel belt sealing ring 2 tightly adhere to the wall surface of the steel belt sealing groove 7, thereby blocking fluid leakage. The steel belt sealing ring 2 contacts the wall surface of the trapezoidal steel belt sealing groove 7, thereby realizing internal sealing; the top of the steel belt sealing ring 2 contacts the wear-resistant steel belt 1, thereby realizing sealing of the gear oil in the drive box, i.e. external sealing.

[0039] As Figure 4As shown, the first protruding part 221 and the second protruding part 222 are inclined outwardly in a radially inward direction, the steel belt sealing ring 2 as a whole is arched, the conveying hole 6 is located between the first protruding part 221 and the second protruding part 222, the opening of the pressurized groove 21 is radially inward, under the action of the pressure medium filled in the pressurized groove 21, the first protruding part 221 and the second protruding part 222 can be separated from the groove bottom surface 711, the first protruding part 221 and the second protruding part 222 are in sealing cooperation with the side wall 712 of the steel belt sealing groove, and the sealing effect is ensured. The first protruding part 221 and the second protruding part 222 are annular, the steel belt sealing ring 2 cooperates with the annular steel belt sealing groove 7, after assembly, the sealing of the outside and the sealing of the pressure medium from the conveying hole 6 to the bottom end of the steel belt sealing groove 7 can be realized. Specifically, the top of the arched steel belt sealing ring 2 contacts the wear-resistant steel belt 1, and the sealing of the top region, i.e. the sealing of the outside and the gear oil side, is realized; the bottom and the side of the arched steel belt sealing ring 2 contact the bottom and the wall of the steel belt sealing groove 7 respectively, and the sealing of the outside and the internal pressure channel and the sealing of the gear oil side and the internal pressure channel are realized.

[0040] Further, the inclination angle of the side wall 712 of the steel belt sealing groove ranges from 8° to 20°, on the one hand, the gap between the sealing side of the steel belt sealing ring 2 and the wall of the steel belt sealing groove 7 is small, the sealing reliability is high, and the back-and-forth movement of the steel belt sealing ring 2 in the steel belt sealing groove 7 under alternating pressure is avoided; on the other hand, the inclination angle is small, the processing difficulty is reduced, and the installation is more convenient. Preferably, the inclination angle is equal to 10°.

[0041] In an embodiment, the designed compression amount of the steel belt sealing ring 2 ranges from 0.8 mm to 1.2 mm, i.e. as shown, Figure 2 the radius of the top of the steel belt sealing groove 7 is smaller than the radius of the top of the sealing ring, and the difference ranges from 0.8 mm to 1.2 mm, that is, when the wear-resistant steel belt 1 is tightly attached to the top of the steel belt sealing groove 7, the steel belt sealing ring 2 is completely pressed into the steel belt sealing groove 7, and the compression amount of the steel belt sealing ring 2 in this state ranges from 0.8 mm to 1.2 mm; preferably, the designed compression amount of the steel belt sealing ring 2 is 1 mm.

[0042] In an embodiment, the maximum allowed extrusion gap of the steel belt sealing ring 2 is 0.1 mm, i.e. the diameter difference between the sealing runway 10 and the wear-resistant steel belt 1 is less than 0.2 mm. In an embodiment, the gap between the first protruding part 221 and the side wall 712 of the steel belt sealing groove is less than 0.05 mm.

[0043] In an embodiment, as shown, Figure 2As shown, the outer contour of the first protruding part 221 and the outer contour of the second protruding part 222 are respectively arc-shaped, preferably, the outer contour of the first protruding part 221 and the second protruding part 222 are symmetrical, and the top is transitioned by a round corner, the inventor considers that: if the top round corner is increased, the mises stress inside the sealing contact position is reduced, the contact width is increased, but the contact pressure will be reduced, which is not conducive to sealing; if the sealing top round corner is reduced, the mises stress inside the sealing contact position is increased, the contact width is reduced, but the contact pressure will be increased, and the sealing performance is excessive. Therefore, the inventor makes improvement: the sealing top round corner is set to 0.5mm, which is beneficial to maintain the basis of sealing performance, appropriately reduce the mises stress inside the sealing contact position, and improve the service life of the sealing ring.

[0044] In an embodiment, a spring 72 is arranged in the pressure boosting groove 21, which can exert a radial outward elastic force on the steel strip sealing ring 2, and the spring 72 provides support to avoid local collapse of the steel strip sealing ring 2 during installation and use due to sudden pressure increase, and can be applied to higher pressure working conditions, such as Figure 3 As shown, the spring 72 can be well fitted with the inside of the pressure boosting groove 21 to provide support and avoid the situation that the steel strip sealing ring 2 is not firmly bonded with the spring 72. During installation, the spring 72 can be sleeved into the pressure boosting groove 21, and then the steel strip sealing ring 2 is installed. The spring 72 can be annular, which is sleeved in the steel strip sealing groove 7, and the circumference of the spring 72 is stretched when subjected to external force, and the spring 72 is located in the pressure boosting groove 21 and is wrapped by the steel strip sealing ring 2.

[0045] As shown in Figure 5 The pressure boosting device includes a conveying pipeline 91 and a flow regulating mechanism 4 arranged in the conveying pipeline 91. The flow regulating mechanism 4 can adopt a pneumatic ball valve. The supply system 9 supplies pressure medium to the conveying hole 6 through the conveying pipeline 91, and the supply system 9 can share the oil circuit on the gear oil side, and uses oil as the medium for compensating pressure, which can reduce the workload of pipeline modification, and even if oil leakage occurs due to excessive compensating pressure, circulation can be formed, and the oil will not be contaminated.

[0046] Further, the conveying pipeline is provided with a pressure sensor; the sealing track 10 is provided with a temperature sensor, and the shield main driving structure comprises an adjusting controller, and the temperature sensor 5 and the flow adjusting mechanism 4 are electrically connected with the adjusting controller. The pressure sensor monitors the pressure data in the conveying pipeline 91 in real time, and the pneumatic ball valve receives the signal from the supply system 9 and controls the opening and closing of the conveying pipeline 91. When the inner diameter size of the wear-resistant steel belt 1 expands outward, and the temperature sensor monitors that the temperature rises, the supply system 9 starts to work, the pressure medium enters the inside of the pressure boosting groove 21 through the conveying pipeline, and the steel belt sealing ring 2 compensates the gap between the wear-resistant steel belt 1 and the sealing track 10 in the radial direction under the action of the pressure. In the normal working state, the inner diameter size of the wear-resistant steel belt 1 does not expand outward, and the supply system 9 does not work. The conveying pipeline 91 is connected with the supply system, and the pressure compensation at different temperatures can be carried out through the conveying pipeline 91, so as to compensate the insufficient sealing compression amount, realize the automatic compensation of the compression amount, guarantee the sealing between the wear-resistant steel belt 1 and the sealing track 10, and ensure that the gear oil in the driving box does not leak from the gap between the wear-resistant steel belt 1 and the sealing track 10. When the temperature sensor 5 monitors that the temperature rises, the temperature information can be displayed on the upper computer 8.

[0047] As shown in Figure 1 The shield main driving structure further comprises a first compression ring 11, a lip seal 12, a first spacer ring 13, a second spacer ring 14, a third spacer ring 15 and a second compression ring 16.

[0048] Scheme two

[0049] The application provides a sealing regulation method applied to the shield main driving structure, which comprises the following steps: when the wear-resistant steel belt 1 is heated and expanded, the pressure boosting device delivers pressure medium to the pressure boosting groove 21. The pressure medium is filled in the pressure boosting groove 21, and the steel belt sealing ring 2 compensates the gap between the wear-resistant steel belt 1 and the sealing track 10 in the radial direction under the action of the pressure, so as to compensate the insufficient sealing compression amount, guarantee the sealing between the wear-resistant steel belt 1 and the sealing track 10, and solve the problems that the assembly precision between the sealing track and the wear-resistant steel belt of the shield main driving structure is poor, and the compression amount is insufficient and leakage occurs in the running process.

[0050] Further, the sealing control method comprises: establishing a model between the temperature and the reaction force of the steel belt sealing ring 2 of the pressure medium delivered by the pressure boosting device, and controlling the pressure of the pressure medium delivered by the pressure boosting device according to the model. The reaction force is generated when the wear-resistant steel belt 1 contacts the steel belt sealing ring 2, and the reaction force is different under different compression amounts. The wear-resistant steel belt 1 expands in size under heat, and the compression amount changes, so that the fluid pressure is applied to the inner side of the steel belt sealing ring 2, and the steel belt sealing ring 2 is tightly attached to the wear-resistant steel belt 1, so that the reaction force of the wear-resistant steel belt 1 is close to the reaction force under the normal state. Specifically, the implementation steps comprise: (1) determining the inner diameter, thickness and other sizes of the wear-resistant steel belt 1, and the temperature range under the working condition; (2) calculating the expansion size of the wear-resistant steel belt 1 under different temperatures through simulation; (3) creating a simulation model of the assembly of the steel belt sealing ring 2, and calculating the reaction force of the steel belt sealing ring 2 under different compression amounts; (4) applying the fluid pressure of the pressure medium to the inner side of the pressure boosting groove 21, and respectively obtaining the reaction force after the fluid pressure is applied under different compression amounts, so as to meet the reaction force requirement; and (5) extracting the temperature and the applied fluid pressure value to draw a curve, fitting a formula to determine the relationship, so as to obtain the compensation pressure under different temperatures.

[0051] Further, the reaction force requirement comprises: the difference between the reaction force under the normal state and the reaction force after the pressure medium is applied is ≤10% of the reaction force under the normal state, and the reaction force under the normal state > the reaction force after the pressure medium is applied.

[0052] In an embodiment of the present application, according to whether the spring 72 is supported or not, the requirement of the pressure bearing capacity of the steel belt sealing ring 2 is adjusted, so as to avoid that the steel belt sealing ring 2 generates large movement inside the steel belt sealing groove 7 under high pressure on one side. (1) The pressure boosting groove 21 is not supported by the spring 72, and is designed to bear the gear oil side pressure of 1 bar and the maximum of 1.5 bar on the outside; the design basis is that, through calculation, the sealing side surface and the wall surface gap are <0.05 mm under the single-side pressure bearing of 1 bar; the sealing side surface and the wall surface gap are 0.16 mm under the single-side pressure bearing of 3 bar; the larger the gap is, the more unfavorable to the sealing is. (2) The pressure boosting groove 21 is supported by the spring 72, and is designed to bear the gear oil side pressure of 3 bar and the maximum of 3.5 bar on the outside; the design basis is that, through calculation, the sealing side surface and the wall surface gap are <0.05 mm under the single-side pressure bearing of 3 bar; the sealing side surface and the wall surface gap are >0.05 mm under the single-side pressure bearing of 3.5 bar.

[0053] The above only describes several embodiments of the present application, and those skilled in the art can make various modifications or changes to the embodiments of the present application according to the disclosed content of the application document without departing from the spirit and scope of the present application.

Claims

1. A sealing control method applied to the main drive structure of a tunnel boring machine, characterized in that, The shield tunneling main drive structure includes: a sealed runway, a wear-resistant steel belt, a steel belt sealing ring, and a pressurization device. The wear-resistant steel belt is installed on the outer periphery of the sealed runway. The sealed runway is provided with a steel belt sealing groove. The steel belt sealing ring is disposed in the steel belt sealing groove. Furthermore, the steel belt sealing ring is located between the sealed runway and the wear-resistant steel belt. A pressure-boosting groove is provided on the side of the steel strip sealing ring away from the wear-resistant steel strip, and the pressure boosting device is connected to the pressure-boosting groove for supplying pressure medium to the pressure-boosting groove; The sealing control method includes: when the wear-resistant steel belt expands due to heat, the pressurizing device delivers a pressure medium to the pressurizing groove.

2. The sealing control method according to claim 1, characterized in that, The steel strip sealing groove has a bottom surface, and the sealing track is provided with a conveying hole that communicates with the pressurizing device, the conveying hole extending to the bottom surface of the groove; The steel strip sealing ring includes a first protrusion and a second protrusion, and the pressure-increasing groove is formed between the first protrusion and the second protrusion. Both the first protrusion and the second protrusion extend towards the bottom surface of the groove.

3. The sealing control method according to claim 1, characterized in that, The sidewall of the steel strip sealing groove is inclined inward in a radially outward direction.

4. The sealing control method according to claim 3, characterized in that, The inclination angle of the sidewall of the steel strip sealing groove ranges from 8° to 20°.

5. The sealing control method according to claim 1, characterized in that, A spring is provided in the pressure-increasing groove, and the spring can apply a radially outward elastic force to the steel strip sealing ring.

6. The sealing control method according to claim 1, characterized in that, The pressurization device includes a delivery pipeline and a flow regulating mechanism disposed on the delivery pipeline.

7. The sealing control method according to claim 6, characterized in that, The conveying pipeline is equipped with a pressure sensor; the sealed runway is equipped with a temperature sensor; the main drive structure of the tunnel boring machine includes a regulating controller; the temperature sensor and the flow regulating mechanism are both electrically connected to the regulating controller.

8. The sealing control method according to any one of claims 1-7, characterized in that, include: A model is established relating temperature, pressure of the pressure medium delivered by the booster device, and the reaction force of the steel belt seal ring. The pressure of the pressure medium delivered by the booster device is controlled based on the model.

9. The sealing control method according to any one of claims 1-7, characterized in that, The difference between the support reaction force under normal conditions and the support reaction force after the application of pressure medium is ≤ 10% of the support reaction force under normal conditions, and the support reaction force under normal conditions is > the support reaction force after the application of pressure medium.

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