An experimental device for accurately measuring buoyancy in soil layers by eliminating friction and negative pore pressure

Abstract

The present invention discloses an experimental device for accurately measuring buoyancy in soil layers, eliminating friction and negative pore pressure. The device comprises a truncated cone body, a base plate, a ventilation pipe, and a water-adding baffle. The truncated cone body is an inverted cone with a hollow interior and an open top. Its lower end has a base plate. The base plate has several through-holes, and a polyvinylidene fluoride film is affixed to its lower surface. The water-adding baffle is fixed within the truncated cone body. The lower end of the ventilation pipe interfaces with the central through-hole of the water-adding baffle. During the experiment, the outer wall of the truncated cone body is coated with lubricating silicone grease, and an earth pressure cell and a pore-water pressure gauge are installed at the center of the lower surface of the polyvinylidene fluoride film. The truncated cone body is then placed into the soil, with the base plate positioned above the soil layer to be measured. Water is then added to the cavity above the water-adding baffle. The water in the truncated cone body is then gradually drained. When the readings of the earth pressure cell and the pore-water pressure gauge are equal, drainage is stopped, and the residual water weight is calculated. The sum of the residual water weight and the weight of the experimental device is the buoyancy of the soil layer.

Description

Technical Field

[0001] The invention relates to an experimental device for accurately measuring buoyancy in a soil layer and eliminating friction and negative pore pressure. Background Art

[0002] Traditional calculations of buoyancy are based on the Archimedean principle, which states that buoyancy is related to the volume of groundwater displaced by the underground structure. In reality, soil is a three-phase medium, and air in the pores significantly influences seepage. Based on the effective stress principle, buoyancy is determined as the product of pore water pressure and foundation area. Experimentally measured buoyancy is often smaller than Archimedean calculations, particularly for foundations in clay soils.

[0003] In this situation, it is crucial to design a reasonable buoyancy model. However, existing buoyancy models cannot effectively solve the friction and negative pore pressure problems experienced by the model in the soil layer, which leads to large errors in the accurate measurement of buoyancy. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental device for accurately measuring buoyancy in soil layers, which eliminates friction and negative pore pressure, so as to solve the problems existing in the prior art.

[0005] The technical solution adopted to achieve the purpose of the present invention is as follows: an experimental device for accurately measuring buoyancy in soil layers to eliminate friction and negative pore pressure, including a frustum body, a bottom plate, a breathable pipe and a water-adding partition.

[0006] The frustum body is an inverted frustum structure with a hollow interior and an open upper end, and a bottom plate is provided at the lower end of the frustum body.

[0007] The bottom plate is provided with a plurality of through holes, and a polyvinylidene fluoride film is pasted on the lower surface of the bottom plate.

[0008] The water adding baffle is located in the truncated cone main body and is fixed on the inner wall of the truncated cone main body.

[0009] There is a gap between the water adding partition and the bottom plate. The water adding partition has a central through hole. The lower end of the air permeable pipe is connected to the central through hole of the water adding partition.

[0010] During the experiment, first, the outer wall of the frustum body is evenly coated with lubricating silicone grease, and a soil pressure box and a pore water pressure gauge are installed at the center of the lower surface of the polyvinylidene fluoride film; then, the frustum body is placed in the soil, with the bottom plate located on the soil layer to be tested, and the pore water pressure gauge and the soil pressure box are respectively arranged in the soil layer to be tested; a set amount of water is added to the cavity of the frustum body located above the water adding partition, and then the water in the frustum body is gradually drained; when the readings of the soil pressure box and the pore water pressure gauge are equal, the drainage is stopped, the water level in the frustum body is determined, and the residual water gravity is calculated. The sum of the residual water gravity and the gravity of the test device is the buoyancy of the soil layer.

[0011] Furthermore, the frustum body, bottom plate and water adding baffle are all made of aluminum plates, and the bottom plate and water adding baffle are both circular.

[0012] Furthermore, the inclination angle of the frustum body is 45°.

[0013] The technical effect of the present invention is unquestionable. The present invention designs a buoyancy precision measurement device that can eliminate the side wall friction and the negative pore pressure of the base and can accurately judge the moment when the inner box floats. The soil pressure box and the pore water pressure gauge are buried at the bottom of the model at the same time. By adding or subtracting the amount of water in the water tank, the measurement value of the soil pressure box is equal to the pore water pressure gauge, and the box body just floats. At this time, the sum of the gravity of the box body and the water in the box is the buoyancy of the soil layer in contact with the bottom of the box body. The present invention can eliminate friction and negative pore pressure to the greatest extent. Friction is eliminated by making the box body into an inverted frustum and applying lubricating silicone grease on the outside; negative pore pressure is eliminated by designing an air-permeable and water-tight barrier at the bottom of the box body and communicating with the external atmospheric pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A three-dimensional diagram of the device of the present invention;

[0015] Figure 2 is a cross-sectional view of the device of the present invention;

[0016] Figure 3 It is a front view of the device of the present invention.

[0017] In the figure: a frustum body 1, a bottom plate 2, a ventilation pipe 3 and a water adding partition 4. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the following examples, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above technical ideas of the present invention, various substitutions and modifications can be made according to common technical knowledge and customary means in the art, and all should be included in the scope of protection of the present invention.

[0019] Example 1:

[0020] This embodiment discloses an experimental device for accurately measuring buoyancy in soil layers by eliminating friction and negative pore pressure, comprising a frustum body 1, a bottom plate 2, an air permeable pipe 3 and a water adding partition 4.

[0021] See also Figure 1 The truncated cone body 1 is an inverted truncated cone structure with a hollow interior and an open upper end, and the lower end of the truncated cone body 1 has a bottom plate 2.

[0022] See also Figure 2 The bottom plate 2 is provided with a plurality of through holes, and a polyvinylidene fluoride film is attached to the lower surface of the bottom plate 2.

[0023] The water adding partition 4 is located in the truncated cone body 1 and fixed on the inner wall of the truncated cone body 1 .

[0024] See also Figure 3 A gap exists between the water-addition baffle 4 and the bottom plate 2. The water-addition baffle 4 has a central through-hole, and the lower end of the air duct 3 is connected to the central through-hole of the water-addition baffle 4. The connection between the air duct 3 and the water-addition baffle 4 is waterproofed, allowing water to be stored in the cavity above the water-addition baffle 4. The polyvinylidene fluoride film is breathable but not water-permeable. The air duct 3 connects to atmospheric pressure, eliminating the negative pore pressure generated when the bottom plate 2 contacts the soil.

[0025] The truncated cone body 1 is made of a lightweight aluminum plate with a thickness of 1 mm, and the inclination angle of the truncated cone body 1 is 45°. The bottom plate 2 is a circular aluminum plate with a thickness of 3 mm. The water adding partition 4 is a circular aluminum plate with a thickness of 1 mm.

[0026] During the experiment, first, the outer wall of the truncated cone body 1 is evenly coated with lubricating silicone grease, and the soil pressure box and pore water pressure gauge are installed at the center of the lower surface of the polyvinylidene fluoride film. Then the truncated cone body 1 is placed in the soil, the bottom plate 2 is located on the soil layer to be tested, and the pore water pressure gauge and soil pressure box are separately arranged in the soil layer to be tested. Add a set amount of water to the cavity of the truncated cone body 1 above the water adding partition 4. Then gradually drain the water in the truncated cone body 1. When the readings of the soil pressure box and the pore water pressure gauge are equal, stop draining, determine the water level in the truncated cone body 1, and calculate the residual water gravity. The sum of the residual water gravity and the gravity of the test device is the buoyancy of the soil layer.

[0027] It is worth noting that the structure described in this embodiment is characterized by its ability to minimize friction and negative pore pressure. Friction is eliminated by shaping the box into an inverted frustum and applying silicone grease to the outside. Negative pore pressure is eliminated by designing an air-permeable, water-tight barrier at the bottom of the box, which is vented to the outside atmospheric pressure, allowing for precise measurement of soil buoyancy.

[0028] Example 2:

[0029] This embodiment discloses an experimental device for accurately measuring buoyancy in soil layers by eliminating friction and negative pore pressure, comprising a frustum body 1, a bottom plate 2, an air permeable pipe 3 and a water adding partition 4.

[0030] See also Figure 1 The truncated cone body 1 is an inverted truncated cone structure with a hollow interior and an open upper end, and the lower end of the truncated cone body 1 has a bottom plate 2.

[0031] See also Figure 2 The bottom plate 2 is provided with a plurality of through holes, and a polyvinylidene fluoride film is attached to the lower surface of the bottom plate 2.

[0032] The water adding partition 4 is located in the truncated cone body 1 and fixed on the inner wall of the truncated cone body 1 .

[0033] See also Figure 3 There is a gap between the water adding partition 4 and the bottom plate 2 , the water adding partition 4 has a central through hole, and the lower end of the air permeable pipe 3 is connected to the central through hole of the water adding partition 4 .

[0034] During the experiment, first, the outer wall of the frustum body 1 is evenly coated with lubricating silicone grease, and a soil pressure box and a pore water pressure gauge are installed at the center of the lower surface of the polyvinylidene fluoride film; then the frustum body 1 is placed in the soil, the bottom plate 2 is located on the soil layer to be tested, and the pore water pressure gauge and the soil pressure box are respectively arranged in the soil layer to be tested; a set amount of water is added to the cavity of the frustum body 1 located above the water adding partition 4, and then the water in the frustum body 1 is gradually discharged; when the readings of the soil pressure box and the pore water pressure gauge are equal, the drainage is stopped, the water level in the frustum body 1 is determined, and the residual water gravity is calculated. The sum of the residual water gravity and the gravity of the test device is the buoyancy of the soil layer.

[0035] Example 3:

[0036] The main structure of this embodiment is the same as that of embodiment 2. Furthermore, the frustum body 1, the bottom plate 2 and the water adding baffle 4 are all made of aluminum plates, and the bottom plate 2 and the water adding baffle 4 are both circular.

[0037] Example 4:

[0038] The main structure of this embodiment is the same as that of embodiment 2. Furthermore, the inclination angle of the frustum body 1 is 45°.

Claims

1. An experimental method for accurately measuring buoyancy in soil layers while eliminating friction and negative pore pressure, characterized by: The method adopts the following experimental device, which includes a frustum body (1), a bottom plate (2), a ventilation pipe (3) and a water adding partition (4); The truncated cone body (1) is an inverted truncated cone structure with a hollow interior and an open upper end, and the lower end of the truncated cone body (1) has a bottom plate (2); The bottom plate (2) is provided with a plurality of through holes, and a polyvinylidene fluoride film is attached to the lower surface of the bottom plate (2); the polyvinylidene fluoride film has the characteristics of being air-permeable and water-impermeable; The water adding partition (4) is located inside the truncated cone body (1) and is fixed on the inner wall of the truncated cone body (1); There is a gap between the water adding partition (4) and the bottom plate (2), the water adding partition (4) has a central through hole, and the lower end of the air vent (3) is connected to the central through hole of the water adding partition (4); During the experiment, first, the outer wall of the truncated cone body (1) is evenly coated with lubricating silicone grease, and a soil pressure box and a pore water pressure gauge are installed at the center of the lower surface of the polyvinylidene fluoride film; then, the truncated cone body (1) is placed in the soil, the bottom plate (2) is located on the soil layer to be tested, and the pore water pressure gauge and the soil pressure box are respectively arranged in the soil layer to be tested; a set amount of water is added to the cavity of the truncated cone body (1) located above the water adding partition (4), and then the water in the truncated cone body (1) is gradually discharged; when the readings of the soil pressure box and the pore water pressure gauge are equal, the drainage is stopped, the water level in the truncated cone body (1) is determined, and the residual water gravity is calculated. The sum of the residual water gravity and the gravity of the test device is the buoyancy of the soil layer.

2. The experimental method for accurately measuring buoyancy in soil layers by eliminating friction and negative pore pressure according to claim 1, characterized in that: The truncated cone body (1), the bottom plate (2) and the water adding baffle (4) are all made of aluminum plates, and the bottom plate (2) and the water adding baffle (4) are both circular.

3. The experimental method for accurately measuring buoyancy in soil layers by eliminating friction and negative pore pressure according to claim 1, characterized in that: The inclination angle of the frustum body (1) is 45°.

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