WO2019232983A1 - 一种桩土接触面剪切力学特性试验装置 - Google Patents

一种桩土接触面剪切力学特性试验装置 Download PDF

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Publication number
WO2019232983A1
WO2019232983A1 PCT/CN2018/107136 CN2018107136W WO2019232983A1 WO 2019232983 A1 WO2019232983 A1 WO 2019232983A1 CN 2018107136 W CN2018107136 W CN 2018107136W WO 2019232983 A1 WO2019232983 A1 WO 2019232983A1
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WIPO (PCT)
Prior art keywords
thrust
pile
plate
soil
contact surface
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PCT/CN2018/107136
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English (en)
French (fr)
Inventor
檀俊坤
乔世范
郭佳奇
刘红中
李东瑞
阳军生
刘日彤
俱鹏柯
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中南大学
河南理工大学
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Application filed by 中南大学, 河南理工大学 filed Critical 中南大学
Priority to US16/533,831 priority Critical patent/US10907320B2/en
Publication of WO2019232983A1 publication Critical patent/WO2019232983A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0025—Shearing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/0042—Pneumatic or hydraulic means
    • G01N2203/0048—Hydraulic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0284—Bulk material, e.g. powders

Definitions

  • the invention relates to the technical field of civil engineering, in particular to a device for testing shear mechanical characteristics of a pile-soil contact surface.
  • Pile foundations are widely used in foundation engineering as a major foundation form.
  • pile foundation engineering As a major foundation form.
  • new pile foundations have appeared on the basis of bored piles and prefabricated piles, such as squeezed branch-and-disc cast-in-situ piles, spiral piles, bamboo piles and bored piles
  • the long piles of super high-rise building pile foundations in deep soft soil areas are generally friction piles or end bearing piles, and the bearing capacity of the pile foundation is mainly provided by the frictional resistance on the side of the pile.
  • the indoor test mainly uses the direct shear test and the ring shear test.
  • the indoor shear test can accurately measure the relative displacement of the pile and soil. The normal displacement of the contact surface was measured, but the contact surfaces of the direct shear test and the ring shear test with the pile specimens were all flat, which is different from the actual soil contact surface of the pile (round pile).
  • the boundary conditions in actual pile load transfer are also different.
  • the horizontal ground pressure of the pile-soil contact surface in actual engineering will increase with the increase of the pile depth, and the increase relationship is linear. For details, see Guo Jiaqi et al.
  • Chinese patent application CN106769478A discloses a pile-soil contact surface test device, which includes a circular model box, a loading plate, a reaction force beam, and a servo-loading motor.
  • the device improves the traditional shear test device, and the column pile is placed in the soil. In the body, the lower and peripheral sides of the soil are closed, and the upper part of the soil is pressed, and the soil applies pressure on the side of the pile.
  • test device does not consider that the horizontal ground pressure of the pile-soil contact surface will follow the depth of the pile Increasing and increasing this factor, and the changes in horizontal ground pressure will affect the test results, so the friction characteristics of the pile-soil contact surface simulated by the above test device are different from the actual pile-soil contact surface friction characteristics.
  • the invention aims at overcoming the shortcomings of the prior art, and provides a device for testing the shear mechanics characteristics of the pile-soil contact surface.
  • the device has a simple operation method and can simulate the actual force situation of the pile-soil more realistically without the need for excessive induction equipment. To reduce complicated theoretical derivation.
  • the present invention provides a test device for shearing mechanical characteristics of a pile-soil contact surface, including a support device, a pressure device, a membrane box, and a thrust device;
  • the support device includes a bottom plate, a top plate, and a support beam, and a bottom plate and a top plate
  • the support beams are connected above the top plate by a plurality of support columns;
  • the pressure device is provided on the support beams to apply vertical pressure to the pile sample;
  • the membrane tube of the membrane box is vertically disposed
  • the bottom plate is sleeved on the radially outer side of the pile sample, and an accommodating cavity is provided between the membrane tube and the pile sample;
  • the thrust device is sleeved on the membrane tube, and is used to face the
  • the membrane tube applies multiple horizontal thrusts to squeeze the soil sample in the membrane tube in a direction perpendicular to the axial direction of the pile sample, and the multiple horizontal thrusts increase linearly from top to bottom.
  • the thrust device includes a thrust cylinder group, a plurality of thrust components evenly distributed along a center circumferential direction of the thrust cylinder group, and a protective cylinder sleeved on an outer peripheral wall of the thrust cylinder group;
  • the thrust cylinder group includes a plurality of thrust cylinders that can be contracted radially, and the plurality of thrust cylinders are superposed on the bottom plate along its axial direction, and two adjacent thrust cylinders are not fixedly connected;
  • Each of the thrust components includes a vertically arranged thrust plate, a plurality of thrust rods arranged horizontally and retractably, and a plurality of thrust springs.
  • the plurality of thrust rods are arranged in the same vertical plane in the up-down direction, and a plurality of thrust rods are arranged.
  • the outer ends of the thrust rods are connected to the thrust plate, the inner ends of the multiple thrust rods are respectively connected to the thrust cylinders and the thrust rods and the thrust cylinders are arranged one-to-one correspondingly; each thrust rod is provided with a thrust spring;
  • the side wall of the protective cylinder is provided with a plurality of side holes for the thrust rod and the thrust spring to pass through; the thrust spring is in contact with the corresponding arc-shaped steel plate.
  • the thrust cylinder has a double-layer cylinder structure, and the inner cylinder and the outer cylinder are coaxially sleeved, and the inner cylinder is surrounded by a plurality of arc-shaped steel plates arranged at even intervals along the circumferential direction of the cylinder.
  • the outer cylinder is surrounded by a plurality of arc-shaped steel plates arranged at even intervals along its circumferential direction, and the gaps between two adjacent arc-shaped steel plates and the gaps between two adjacent arc-shaped steel plates are staggered inside and outside, and each An arc-shaped steel plate can be horizontally slidably fitted with two arc-shaped steel plates on the inner side of the thrust cylinder; the inner ends of the plurality of thrust rods are respectively connected with the arc-shaped steel plate, and the thrust rod and the arc-shaped steel plate A corresponding setting;
  • the thrust rods of the same layer connected to the same thrust barrel are located in the same horizontal plane, and the inner ends of the thrust rods of the same layer all point to the central axis of the thrust barrel.
  • the thrust rod includes a solid rod and a hollow rod, an inner end of the solid rod is connected to an outer side wall of the arc-shaped steel plate, and an outer end of the solid rod is slidably inserted into the hollow rod.
  • the free lengths of the thrust springs sleeved on the thrust rods of the same layer are equal, and the elastic coefficient of the thrust springs of the thrust rods of each layer from the top to the bottom increases linearly.
  • the position of the thrust plate inwardly the center of the circular bottom plate
  • the length of the thrust rod is shortened.
  • all thrust springs mounted on the thrust rod are compressed by the same amount of compression. Due to the thrust of each layer from top to bottom
  • the elastic coefficient of the thrust spring on the rod increases linearly, so the thrust device generates a plurality of horizontal thrusts that linearly increase from top to bottom.
  • each thrust cylinder corresponds to a layer of thrust rods
  • the specimen is extruded, which is consistent with the fact that the horizontal pressure of the pile and soil in actual engineering increases with depth.
  • the hollow rod is provided with a nut, the thrust spring is disposed between the nut and the arc-shaped steel plate, and the free lengths and elastic coefficients of all the thrust springs are equal. Consistent with the above structural principle, the thrust of the thrust device on a plurality of thrust cylinders from top to bottom also linearly increases from top to bottom, which can effectively simulate the horizontal ground pressure on piles and soils in actual engineering.
  • the bottom plate and the top plate are both circular plates, and the bottom plate and the top plate are each provided with a plurality of positioning devices evenly distributed along a central circumferential direction thereof, and each of the positioning devices includes a positioning along a radial direction of the bottom plate.
  • the upper and lower sides of the push plate are provided with a stop block for limiting the upper and lower positions of the push plate, which can effectively prevent the push plate from being moved up and down during the adjustment process; the latch and the post The fit is used to position the push plate inside and outside the support device.
  • the bottom plate and the top plate are respectively provided with a through hole A and a through hole B for inserting the pile sample, the through hole A and the through hole B are arranged coaxially; a plurality of the supports The pillars are arranged up and down through the bottom plate and the top plate; the support beam is connected to a plurality of the support pillars, and the support beam is provided with a through hole C;
  • the pressure device includes a vertical loading device, a force transmission rod, a pressure sensor, and a displacement sensor; the vertical loading device is detachably disposed on the support beam; the power transmission rod is disposed through the through hole C, and One end is connected to the vertical loading device, and the other end is used to contact the top of the pile sample; the pressure sensor and the displacement sensor are sandwiched between the force transmission rod and the pile sample ;
  • the film box includes a film tube, a water permeable plate, and a cover; the film tube is made of a flexible material; the water permeable plate is disposed in the film tube and blocks the lower port of the film tube, and the cover is provided On the top of the membrane tube and the upper port of the membrane tube is sealed; through holes D and through holes E are respectively provided on the water-permeable plate and the cover, and the upper and lower ends of the pile sample penetrate the respectively The through hole E and the through hole D are provided.
  • the permeable plate includes a permeable plate body and a flexible film provided on the periphery of the permeable plate body, and the through hole D is provided on the permeable plate body;
  • the film box further includes pressing the cover and the film tube tightly. At least three pressing rods;
  • the top plate is provided with a plurality of through holes F adapted to the number of the pressing rods, and each of the through holes F passes through one of the pressing rods, and the pressing The lower end of the rod is used to press on the cover.
  • the upper port of the membrane tube is covered with a cap; the compression rod passes through the through hole F from top to bottom, and the lower end of the compression rod It is pressed on the cover, and the pressing rod is fixedly connected with the top plate.
  • the supporting device includes 3 supporting columns, the bottom end of the supporting column is 50-200cm lower than the bottom plate, and the top of the supporting column is 30-200cm higher than the top plate; the supporting beam is a trifurcation A beam, each beam fork is fixedly connected to one of the support columns; a through hole C is provided at the center of the tri-fork beam.
  • the present invention has the following beneficial effects:
  • the device for testing the shear mechanical characteristics of the pile-soil contact surface of the present invention includes a support device, a pressure device, a membrane box, and a thrust device;
  • the support device includes a bottom plate, a top plate, a support beam, and a plurality of support columns;
  • the support beam is used to apply vertical pressure to the pile sample;
  • the membrane box includes a membrane tube, a permeable plate and a cover, and the membrane tube is made of a flexible plastic film;
  • a thrust device is sleeved on the membrane tube and is used to apply pressure to the membrane tube. Multiple horizontal thrusts of various sizes are applied to squeeze the soil sample in the membrane tube in a direction perpendicular to the axial direction of the pile sample.
  • the test device of the invention has a simple structure and simple operation, and can accurately simulate the mechanical characteristics of piles and soils of different types of pile foundations in actual engineering, and provides a theoretical basis for the design of actual engineering pile foundations.
  • the film box of the present invention includes a circular film tube, a water permeable plate, and a cover.
  • the water permeable plate includes a water permeable plate body and a first flexible film;
  • the film tube is made of a flexible plastic film, and is applied to the film tube from the side.
  • Horizontal thrust which realizes the effect of horizontal stress transmission on piles and soils, realistically simulates the pile-soil stress state in actual engineering, and improves the accuracy of the simulation; at the same time, the solid cylindrical concrete pile samples of larger samples can be placed in the membrane box of the present invention
  • hollow cylinders and other pile materials, and the existing geotechnical instruments were used to study the mechanical characteristics of pile-soil contact surface under static load.
  • the thrust device of the present invention includes a thrust cylinder group, a plurality of thrust components, and a protection cylinder;
  • the thrust cylinder group includes a plurality of radially retractable thrust cylinders, and the plurality of thrust cylinders are superposed on the bottom plate along its axial direction, And the two adjacent thrust cylinders are not firmly connected;
  • the thrust cylinder includes an inner cylinder and an outer cylinder which are coaxially set, and the inner cylinder is surrounded by a plurality of arc-shaped steel plates arranged at even intervals along its circumferential direction.
  • the outer cylinder is surrounded by a plurality of arc-shaped steel plates evenly spaced along its circumference; by adjusting the length of the thrust rod, the thrust spring sleeved on it exerts different horizontal thrust on the pile and soil from the outer periphery of the membrane box It can adapt to the simulation of different horizontal ground pressures on piles and soils under different conditions, and can adapt to the real simulation of different conditions of horizontal ground pressure on any overlay and any pile-soil location, with a wide range of applications.
  • the free lengths of the thrust springs sleeved on the thrust rods of the same layer are equal, and the elastic coefficient of the thrust springs of the thrust rods of each layer from the top to the bottom increases linearly.
  • the thrust spring gives the horizontal thrust of the pile-soil contact surface to increase linearly from top to bottom. It is consistent with the situation that the horizontal ground pressure of piles and soils increases with depth in actual engineering; it can realistically simulate the distribution of horizontal ground pressures of piles and soils, and is especially suitable for long piles.
  • the thrust rod includes a solid rod and a hollow rod, the inner end of the solid rod is connected to the outer wall of the arc-shaped steel plate, and the outer end is inserted in the hollow rod; a nut is provided on the hollow rod; a thrust spring is provided on the nut And curved steel plates, and all thrust springs have the same length and the same elastic coefficient. Expand the application range of the pile-earth pressure given by the thrust spring, without adjusting the pile-soil contact, and adjust the compression amount of the thrust spring on the thrust spring to change the rate of pressure increase from the top-to-bottom thrust spring compression to the pile-soil contact surface, which is suitable for actual engineering. Shear tests on contact surfaces between piles and soil of different lengths.
  • FIG. 1 is a schematic diagram of a three-dimensional structure of a device for testing shear mechanical characteristics of a pile-soil contact surface according to the present invention
  • FIG. 2 is a schematic cross-sectional structure diagram of a device for testing shear mechanical characteristics of a pile-soil contact surface in FIG. 1;
  • FIG. 3 is a schematic structural diagram of a supporting device in the present invention.
  • FIG. 4 is a schematic cross-sectional structure diagram of a membrane box in the present invention.
  • FIG. 5 is a schematic structural diagram of a thrust device in the invention.
  • FIG. 6 is a schematic structural diagram of a thrust cylinder in FIG. 5;
  • FIG. 7 is a schematic structural diagram of cooperation between a thrust rod and a nut in the present invention.
  • FIG. 8 is a schematic structural diagram of a protective cylinder in FIG. 5;
  • support device 1.1, bottom plate, 1.2, top plate, 1.3, support beam, 1.4, support column, 1a, long slot, 1b, card column, 1c, latch, 2, pressure device, 2.1, vertical loading Device, 2.1a, force transmission rod, 2.2, displacement sensor, 2.3, pressure sensor, 3, membrane box, 3.1, membrane tube, 3.2, permeable plate, 3.3, cover, 3.4, compression rod, 4, thrust device, 4.1 Thrust cylinder, 4.1a, curved steel sheet, 4.1b, curved steel plate, 4.2, thrust plate, 4.3, thrust rod, 4.3a, solid rod, 4.3b, hollow rod, 4.3c, nut, 4.4, thrust Spring, 4.5, protection cylinder, 4.5a, side hole, 5, pile sample, 6, soil sample.
  • a device for testing shear mechanical properties of a pile-soil contact surface includes a support device 1, a pressure device 2, a membrane box 3, and a thrust device 4.
  • the specific structure is as follows:
  • the supporting device includes a bottom plate 1.1, a top plate 1.2, a supporting beam 1.3, and a plurality of supporting columns 1.4; the bottom plate and the top plate are both circular steel plates, and the center portion of the bottom plate is provided with a through hole A for inserting the pile sample 5
  • the central part of the top plate is provided with a through-hole B for inserting the pile sample 5, and the through-hole A and the through-hole B are coaxially arranged up and down and have the same aperture size.
  • the bottom plate and the top plate are provided with a plurality of positioning devices evenly distributed along the center circumferential direction.
  • Each positioning device includes a long slot hole 1a arranged along the radial direction of the bottom plate (top plate), and cards provided on both sides of the long slot hole length direction.
  • the post 1b and the latch 1c for positioning the inner and outer positions of the push plate on the support device.
  • the number of support pillars is preferably three, and the three support pillars are all arranged through the bottom plate and the top plate.
  • the bottom end of the support pillar is 60 cm lower than the bottom plate and the top of the support pillar is 50 cm higher than the top plate. It is convenient to test the pile sample.
  • a support beam is located above the top plate.
  • the support beam is a trifurcated beam.
  • Each beam fork is provided with a connection hole, and the beam fork is fixedly connected to the support column through the connection hole.
  • the through hole C is provided on the center portion of the support beam.
  • the pressure device includes a vertical loading device 2.1, a force transmission rod 2.2, a pressure sensor 2.3, and a displacement sensor 2.4;
  • the vertical loading device is a servo hydraulic machine provided on a support beam;
  • the top of the force rod is connected to the vertical loading device.
  • the bottom end of the force transmission rod is used to contact the top of the pile sample.
  • the displacement sensor is set on the end surface of the force transmission rod for contact with the pile sample.
  • the pressure sensor is connected to the displacement.
  • the sensors are connected and sandwiched between the displacement sensor and the pile sample.
  • the vertical loading device applies vertical pressure to the pile sample through a force transmission rod; a displacement sensor is used to detect the displacement of the pile sample, and a pressure sensor is used to sense the pressure exerted by the servo hydraulic machine on the pile sample.
  • the membrane box is vertically arranged on the bottom plate, and includes a circular membrane tube 3.1, a water permeable plate 3.2, and a cover 3.3; the membrane box further includes 3 compression rods for compressing the cover and the membrane tube.
  • the top plate is provided with three through holes F, and a pressing rod is inserted through each through hole F.
  • the permeable plate is set at the bottom of the membrane tube and blocks the lower port of the membrane tube.
  • the cover is used to seal the upper port of the membrane tube; the membrane tube is used to be sleeved on the radial outer side of the pile sample, and when the pile sample is inserted When set in the membrane box, there is an accommodating cavity for accommodating the soil sample between the membrane tube and the pile sample.
  • the water-permeable board and the cover are respectively provided with a through-hole D and a through-hole E; during the test, the upper and lower ends of the pile sample are respectively set through the through-hole E and the through-hole D.
  • the membrane tube is made of a rubber membrane; in order to prevent the dehydration plate from adversely affecting the horizontal force applied by the thrust device, the water permeable plate is composed of a circular water permeable plate body provided at the center thereof and the flexibility provided on the outer peripheral side of the water permeable plate body.
  • the through hole D is disposed at the center of the pervious plate body; the flexible film is sealedly connected to the membrane tube and the pervious plate respectively; preferably, the flexible film is also a rubber film.
  • the cover is a steel plate that is movable on the upper end of the film tube, and the cover is pressed against the film tube (the soil sample is contained in the film tube) by a pressing rod to prevent the soil sample in the film box from protruding upward during the test. As a result, the pressure fails.
  • This structure setting is convenient for filling the soil sample into the membrane tube, and does not adversely affect the shrinkage diameter of the membrane tube when the membrane tube is radially compressed, thereby avoiding affecting the simulation effect.
  • the thrust device is sleeved on the membrane tube and is used to apply multiple horizontal thrusts to the membrane tube to squeeze the soil sample in the membrane tube in a direction perpendicular to the axial direction of the pile sample.
  • Horizontal thrust increases linearly from top to bottom.
  • the thrust device includes a thrust barrel group, a plurality of thrust components evenly distributed in the circumferential direction of the center of the thrust barrel group, and a protective barrel 4.5 sleeved on the outer peripheral wall of the thrust barrel group; it needs special explanation in order to facilitate the clearer display of the thrust device
  • the outer end of the thrust rod is fixedly connected to the thrust plate, and the inner end of the thrust rod penetrates the side hole of the protective cylinder and is connected to the thrust cylinder.
  • the arc-shaped steel plate is fixedly connected; a thrust spring sleeved on the thrust rod also penetrates the side hole, and at least contacts the arc-shaped steel plate and generates a horizontal thrust force when the thrust is applied.
  • the thrust cylinder group includes a plurality of thrust cylinders 4.1 that can be contracted radially, and the plurality of thrust cylinders are equal in size and are arranged on the bottom plate along the axial direction.
  • Fixed connection between the two adjacent thrust cylinders 4.1, between the topmost thrust cylinder and the cover 3.3, and between the bottommost thrust cylinder and the bottom plate 1.1, lubrication is performed.
  • each thrust cylinder shrinks radially according to the level of horizontal pressure it receives, which in turn exerts different pressures on the soil sample and pile sample in the membrane box.
  • the thrust cylinder has a double-layered cylinder structure, and the inner cylinder and the outer cylinder are coaxially sleeved.
  • the inner cylinder is surrounded by a plurality of arc-shaped steel plates 4.1a arranged at even intervals along its circumference.
  • the layer cylinder is surrounded by a plurality of arc-shaped steel plates 4.1b arranged at even intervals along its circumferential direction.
  • the gap between two adjacent arc-shaped steel plates and the gap between two adjacent arc-shaped steel plates are staggered inside and outside, and each arc
  • the shaped steel plates can be horizontally slidably fitted with two arc-shaped steel plates located on the inner side of the shaped steel plates in the circumferential direction of the thrust cylinder.
  • Each thrust component includes a vertically arranged thrust plate 4.2, horizontally arranged and retractable multiple thrust rods 4.3 and multiple thrust springs 4.4.
  • the multiple thrust rods 4.3 are arranged in the same vertical plane in the vertical direction.
  • the outer ends of the plurality of thrust rods are connected to the thrust plate, the inner ends of the plurality of thrust rods are respectively connected to the curved steel plates and the thrust rods and the curved steel plates are arranged one-to-one correspondingly; each thrust rod is provided with a thrust spring.
  • the arc-shaped steel plates of multiple thrust cylinders superimposed up and down are also correspondingly arranged up and down.
  • the same row of arc-shaped steel plates is called a group; the number of thrust rods included in each thrust component and the arc-shaped steel plate in a group of arc-shaped steel plates.
  • the number is equal, and the number of thrust components is equal to the number of curved steel plates.
  • the upper and lower ends of the push plate are arranged through long slot holes that penetrate the top plate and the bottom plate, respectively, and move along the length direction of the holes in the long slot holes.
  • a plurality of side holes 4.5a are provided on the side wall of the protective cylinder for the thrust rod and thrust spring to pass through; the protective cylinder can effectively prevent the soil sample in the membrane cylinder from generating outward tension. Damage to the membrane cartridge.
  • the thrust rods are arranged one-to-one corresponding to the arc-shaped steel plates; the thrust rods of the same layer connected to the same thrust cylinder are located in the same horizontal plane, and the inner ends of the thrust rods of the same layer all point to the central axis of the thrust cylinder.
  • the thrust rod includes a solid rod 4.3a and a hollow rod 4.3b. The inner end of the solid rod is connected to the outer wall of the arc-shaped steel plate, and the outer end of the solid rod is inserted in the hollow rod.
  • the latch is placed outside the push plate and inserted between two adjacent card posts to position the push plate.
  • the thrust spring is compressed and applies lateral horizontal pressure to the thrust cylinder.
  • the length is determined by the push plate and the thrust spring together.
  • the horizontal pressure received by the thrust cylinder can be calculated and obtained according to the elastic coefficient of the thrust spring and the compression amount of the thrust spring.
  • the superposed height of a plurality of thrust cylinders is equal to the height of the membrane cylinder, and the thrust cylinder is covered on the outer peripheral wall of the membrane cylinder; it is convenient for the thrust device to apply horizontal thrust to the pile sample and soil sample in the membrane box.
  • the device for testing the shearing mechanical characteristics of the pile-soil contact surface is tested by using the device for testing the shear-mechanical characteristics of the pile-soil contact surface.
  • the thrust device applies a horizontal pressure to the thrust cylinder to make it shrink radially, and then the soil sample in the membrane box is tested.
  • the application of horizontal thrusts with different sizes up and down can effectively simulate the horizontal ground pressure of piles and soils in actual engineering, which is beneficial to the study of piles and soils.
  • the specific test method includes the following steps:
  • the vertical loading device 2.1 can be detachably installed on the supporting beam, the top of the pile sample is connected to the vertical loading device through the force transmission rod 2.2, and the pile sample and the force transmission rod are sandwiched between There are pressure sensor 2.3 and displacement sensor 2.4; the vertical loading device is preferably a servo hydraulic machine.
  • Multi-layer horizontal thrust is applied to the axial direction of the outer periphery of the membrane tube to squeeze the soil sample in the membrane tube in a direction perpendicular to the axial direction of the pile sample.
  • Pressure the horizontal thrust of multiple layers increases linearly from top to bottom; maintain the levels of each layer when the pressure generated by the top thrust and bottom thrust on the soil sample is equal to the pressure at the upper and lower sections of the pile segment to be measured in actual engineering The thrust is unchanged.
  • "Pile section” refers to the selection of a part of the pile or the whole pile according to the needs of the project.
  • step (4) can implement horizontal thrust on the pile soil by the following two methods, specifically:
  • the first method The free lengths of the thrust springs sleeved on the thrust rods of the same layer are equal, and the elastic coefficient of the thrust springs of the thrust rods of each layer from the top to the bottom increases linearly.
  • the thrust plate is adjusted inward (in the direction of the axis of the membrane tube).
  • the length of the thrust rod is shortened, and the thrust spring fitted on the thrust rod is compressed.
  • the thrust spring gives the pile and soil.
  • the horizontal pressure of the contact surface increases linearly from top to bottom, which is consistent with the fact that the horizontal pressure of the pile and soil in the actual project increases with depth; it can realistically simulate the distribution of pile-soil pressure and is especially applicable Yu Changzhu.
  • the second method the hollow rod is provided with a nut (the hollow rod is provided with a thread), the thrust spring is disposed between the nut and the arc-shaped steel plate, and the length and elastic coefficient of all the thrust springs are equal.
  • This structure can also expand the applicable range of the pile-earth pressure given by the thrust spring, without adjusting the pile-soil contact, and by adjusting the compression amount of the nut to the thrust spring, the rate of pressure increase from the top-to-bottom thrust spring to the pile-soil contact surface can be adjusted. It is suitable for the shear test of the contact surface between piles and soil of different lengths in actual engineering.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)

Abstract

一种桩土接触面剪切力学特性试验装置，包括支撑装置（1）、压力装置（2）、膜箱（3）和推力装置（4）；支撑装置（1）包括底板（1.1）、顶板（1.2）、支撑梁（1.3）和多根支撑柱（1.4），底板（1.1）和顶板（1.2）上均设有用于桩试样（5）插入的通孔；压力装置（2）包括竖向加载装置（2.1）和传力杆（2.1a），竖向加载装置（2.1）通过传力杆（2.1a）将竖向压力施加在桩试样（5）上；膜箱（3）包括膜筒（3.1）、透水板（3.2）和封盖（3.3），膜筒（3.1）套设在桩试样（5）的径向外侧，膜筒（3.1）与桩试样（5）之间具有容置土试样（6）的容置腔；推力装置（4）套设在膜筒（3.1）上，并提供沿垂直于桩试样（5）轴向的方向的推力对膜箱（3）内的土试样（6）进行挤压。该桩土接触面剪切力学特性试验装置构造简单、操作简便，能准确模拟不同类型桩基础的桩土在实际工程中的力学特性，有利于桩土试验的研究。

Description

一种桩土接触面剪切力学特性试验装置 技术领域
本发明涉及土木工程技术领域，特别地，涉及一种桩土接触面剪切力学特性试验装置。
背景技术
随着我国城市建设的快速发展，当前出现了很多高层和超高层建筑，这些高层和超高层建筑对地基承载力要求较高，桩基础作为一种主要的基础形式被广泛应用于基础工程中。随着桩基础工程实际经验的累积和理论研究的深入，在钻孔桩和预制桩的基础上出现了许多新型桩基础，如挤扩支盘灌注桩、螺旋桩、竹节桩和钻孔桩等；而在深厚软土地区的超高层建筑桩基础的长桩一般为摩擦桩或端承桩，桩基础的承载力主要由桩侧摩擦阻力提供。现有建筑桩基技术规范中给出的桩侧摩阻力计算值偏差较大，因而需要结合模型试验对不同类型桩基础的桩土摩擦性能进行研究，为实际工程桩基设计提供理论依据。
目前对桩土接触面剪切力学特性的研究主要基于现场试验和室内试验两种方式，室内试验主要采用直剪试验和环剪试验，室内剪切试验可以准确测得桩土相对位移，同时能够测得接触面法向位移，然而直剪试验和环剪试验与桩试样的接触面均为平面，这与实际桩(圆形桩)土接触面不同，且剪切试验中的边界条件与实际桩荷载传递过程中的边界条件也不同。实际工程中桩土接触面的水平地压会随着桩的深度增加而增大，增大关系呈线性关系，具体见郭佳奇等人2010年在北京交通大学学报上发表的《高应力下干砂与饱和砂单剪特性比较》。中国专利申请CN106769478A公开了一种桩土接触面试验装置，包括圆形模型箱、加载板、反力梁和伺服加载电机，该装置通过对传统剪切试验装置进行改进，柱形桩置于土体中，并对土体下部和周侧封闭，对土体上部施压，进而土体对桩侧施加压力，然而该试验装置并未考虑桩土接触面的水平地压会随着桩的深度增加而增大这一因素，而水平地压的变化会对试验结果产生的影响，因此采用上述试验装置模拟所得桩土接触面摩擦性与实际桩土接触面摩擦特性有所不同。
因此，本领域的技术人员需要研发一种新的桩土接触面剪切力学特性试验装置，以解决上述问题。
发明内容
本发明旨在克服现有技术的不足，提供一种桩土接触面剪切力学特性试验装置，该装置操作方法简单，无需借助过多感应设备，就能较为真实的模拟桩土实际受力情况，减少繁杂的理论推导。
为实现上述目的，本发明提供了一种桩土接触面剪切力学特性试验装置，包括支撑装置、压力装置、膜箱和推力装置；所述支撑装置包括底板、顶板和支撑梁，底板和顶板通过多根支撑柱相连，所述支撑梁设置在顶板的上方；所述压力装置设置在所述支撑梁上，用于向桩试样施加竖向压力；所述膜箱的膜筒竖向设置在所述底板上且套设在桩试样的径向外侧，所述膜筒与桩试样之间具有容置腔；所述推力装置套设在所述膜筒上，用于向所述膜筒施加多个水平推力以对所述膜筒内的土试样沿垂直于桩试样轴向的方向进行挤压，多个水平推力从上到下线性递增。
进一步的，所述推力装置包括推力筒组、沿所述推力筒组中心周向均布的多个推力组件以及套设在所述推力筒组外周壁上的防护筒；
所述推力筒组包括可径向收缩的多个推力筒，多个所述推力筒沿其轴向叠加设置在所述底板上，且相邻两所述推力筒之间不固连；
每个所述推力组件均包括一竖向布置的推板、水平状布置且可伸缩的多根推力杆和多个推力弹簧，多根推力杆在同一竖直面内沿上下方向布置，多根推力杆的外端均与推板相连，多根推力杆的内端与推力筒分别相连且推力杆和推力筒一一对应设置；每根推力杆上套设有一所述推力弹簧；
所述防护筒的侧壁上开设有多个侧孔，用于所述推力杆及所述推力弹簧穿设；推力弹簧与与其对应的弧形钢板相接触。
进一步的，所述推力筒为双层筒体结构，内层筒体与外层筒体同轴套装，所述内层筒体由沿其周向均匀间隔设置的多片弧形钢片围成，所述外层筒体由沿其周向均匀间隔设置的多块弧形钢板围成，两相邻弧形钢板的间隔缝与两相邻弧形钢片的间隔缝内外错开设置，且每一块弧形钢板均与位于其内侧的两片弧形钢片能在所述推力筒的周向上水平滑动配合；多根推力杆的内端与弧形钢板分别相连且推力杆和弧形钢板一一对应设置；
与同一所述推力筒相连的同一层推力杆位于同一水平面内，且同一层推力杆的内端均指向所述推力筒的中轴线。
进一步的，所述推力杆包括实心杆和空心杆，所述实心杆的内端与所述弧形钢板的外侧壁相连，所述实心杆的外端滑动插设在所述空心杆内。
进一步的，套设在同一层推力杆上的推力弹簧的自由长度相等，且从上至下每层推力杆上的推力弹簧的弹性系数线性递增。通过向内(圆形底板的中心部)调整推板的位置使得推力杆的长度缩短，同时套设在该推力杆上的所有推力弹簧被压缩相同的压缩量，由于从上至下每层推力杆上的推力弹簧的弹性系数线性递增，因而该推力装置产生从上至下线性增大的多个水平推力通过相应的推力筒(每个推力筒对应一层推力杆)对膜筒内的土试样进行挤压，这与桩土在实际工程中所受水平地压随深度的增加而不断增加的情况一致。
进一步的，所述空心杆上设置有螺母，所述推力弹簧设置在所述螺母与所述弧形钢板之间，且所有推力弹簧的自由长度和弹性系数均相等。与上述结构原理一致，该推力装置对从上至下多个推力筒的推力也从上至下线性递增，可有效模拟桩土在实际工程中所受的水平地压。
进一步的，所述底板和顶板均为圆形板，所述底板和顶板上均设有沿其中心周向均布的多个定位装置，每个所述定位装置均包括沿所述底板径向方向设置的长槽孔、设置在所述长槽孔长度方向两侧的多个卡柱和用于定位所述推板在所述支撑装置上的内外位置的插销。本领域的技术人员可以理解的，推板的上端和下端的两侧各设有一个用于限定推板上下位置的限位块，可有效防止调整过程中推板上下走位；插销与卡柱配合用于定位推板在支撑装置的内外位置。
进一步的，所述底板和所述顶板上分别设有用于所述桩试样插入的通孔A和通孔B，所述通孔A与所述通孔B同轴设置；多根所述支撑柱均上下贯穿所述底板和所述顶板设置；所述支撑梁与多根所述支撑柱连接，所述支撑梁上设有通孔C；
所述压力装置包括竖向加载装置、传力杆、压力传感器和位移传感器；所述竖向加载装置可拆卸设置在所述支撑梁上；所述传力杆贯穿所述通孔C设置，其一端与所述竖向加载装置相连、另一端用于与所述桩试样的顶端相接触；所述压力传感器和所述位移传感器夹设在所述传力杆与所述桩试样之间；
所述膜箱包括膜筒、透水板和封盖；所述膜筒由柔性材料制成；所述透水板设置在所述膜筒内并将膜筒的下端口堵住，所述封盖设置在所述膜筒的顶部并将膜筒的上端口密封； 所述透水板和封盖上分别设有通孔D和通孔E，所述桩试样的上、下两端分别贯穿所述通孔E和通孔D设置。
进一步的，所述透水板包括透水板本体和设置在透水板本体周边的柔性膜，所述通孔D设置在透水板本体上；所述膜箱还包括将封盖与所述膜筒压紧的至少三根压紧杆；所述顶板上设有数量与压紧杆的数量相适配多个通孔F，每个所述通孔F内穿设一所述压紧杆，所述压紧杆的下端用于压在所述封盖上。本领域的技术人员可以理解的，当膜筒内的土试样被压实后，用封盖盖住膜筒的上端口；压紧杆从上至下贯穿通孔F，压紧杆的下端压在封盖上，压紧杆与顶板固定连接。
进一步的，所述支撑装置包括3根支撑柱，所述支撑柱的底端比所述底板低50～200cm，所述支撑柱的顶端比所述顶板高30～200cm；所述支撑梁为三叉型梁，每个梁叉与一根所述支撑柱固定连接；通孔C设置在三叉型梁的中心部位。
相比于现有技术，本发明具有以下有益效果：
(1)、本发明的桩土接触面剪切力学特性试验装置，包括支撑装置、压力装置、膜箱和推力装置；支撑装置包括底板、顶板、支撑梁和多根支撑柱；压力装置设置在支撑梁上，用于向桩试样施加竖向压力；膜箱包括膜筒、透水板和封盖，膜筒由柔性塑料膜制成；推力装置套设在膜筒上，用于向膜筒施加多个大小不等的水平推力以对膜筒内的土试样沿垂直于桩试样轴向的方向进行挤压。本发明的试验装置构造简单、操作简便，可准确模拟不同类型桩基础的桩土在实际工程中的力学特性，为实际工程桩基设计提供理论依据。
(2)、本发明的膜箱包括圆形的膜筒、透水板和封盖，透水板包括透水板本体和第一柔性膜；膜筒由柔性塑料膜制成，通过从侧面对膜筒施加水平推力，实现对桩土施加水平应力传递效果，真实模拟实际工程中桩土受力状态，提高模拟准确度；同时，本发明的膜箱内可放置较大试样的实心圆柱混凝土桩试样和空心圆柱等多种桩型材料，并使用已有的土工仪器来研究桩-土接触面在静荷载作用下的力学特性。
(3)、本发明的推力装置包括推力筒组、多个推力组件以及防护筒；推力筒组包括可径向收缩的多个推力筒，多个推力筒沿其轴向叠加设置在底板上，且相邻两推力筒之间不固连；推力筒包括同轴套装的内层筒体与外层筒体，内层筒体由沿其周向均匀间隔设置的多片弧形钢片围成，外层筒体由沿其周向均匀间隔设置的多块弧形钢板围成；通过调整推力杆的长度使套设在其上的推力弹簧从膜箱的外周对桩土施加不同的水平推力，适应不同状 态下桩土所受水平地压不同的情况模拟，并能适应任意覆盖层、任意桩土位置水平地压不同情况的真实模拟，适用范围广。
(4)、本发明中套设在同一层推力杆上的推力弹簧的自由长度相等，从上至下每层推力杆上的推力弹簧的弹性系数线性递增。通过向内调整推板的位置，推力杆的长度缩短，套设在推力杆上的推力弹簧被压缩相同的压缩量，推力弹簧给予桩土接触面从上到下呈线性增加的水平推力，这与桩土在实际工程中所受水平地压随深度的增加而不断增加的情况一致；可以真实的模拟桩土水平地压的分布，尤其适用于长桩。
(5)、本发明中推力杆包括实心杆和空心杆，实心杆的内端与弧形钢板的外壁相连、外端插设在空心杆中；空心杆上设置有螺母；推力弹簧设置在螺母与弧形钢板之间，且所有推力弹簧的长度相等、弹性系数也相等。扩大推力弹簧给予桩土压力的适用范围，可以不调整桩土接触度，通过调整螺母对推力弹簧的压缩量改变从上到下推力弹簧压缩给予桩土接触面压强增大的速率，适应实际工程不同长度桩与土接触面剪切试验。
除了上面所描述的目的、特征和优点之外，本发明还有其它的目的、特征和优点。下面将参照图，对本发明作进一步详细的说明。
附图说明
构成本申请的一部分的附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1是本发明桩土接触面剪切力学特性试验装置的立体结构示意图；
图2是图1中桩土接触面剪切力学特性试验装置的剖面结构示意图；
图3是本发明中支撑装置的结构示意图；
图4是本发明中膜箱的剖面结构示意图；
图5是发明中推力装置的结构示意图；
图6是图5中推力筒的结构示意图；
图7是本发明中推力杆与螺母配合的结构示意图；
图8是图5中防护筒的结构示意图；
其中，1、支撑装置，1.1、底板，1.2、顶板，1.3、支撑梁，1.4、支撑柱，1a、长槽孔，1b、卡柱，1c、插销，2、压力装置，2.1、竖向加载装置，2.1a、传力杆，2.2、位移传感器，2.3、压力传感器，3、膜箱，3.1、膜筒，3.2、透水板，3.3、封盖，3.4、压紧杆，4、 推力装置，4.1、推力筒，4.1a、弧形钢片，4.1b、弧形钢板，4.2、推板，4.3、推力杆，4.3a、实心杆，4.3b、空心杆，4.3c、螺母，4.4、推力弹簧，4.5、防护筒，4.5a、侧孔，5、桩试样，6、土试样。
具体实施方式
以下结合附图对本发明的实施例进行详细说明，但是本发明可以根据权利要求限定和覆盖的多种不同方式实施。
如图1和图2所示，本发明的一种桩土接触面剪切力学特性试验装置，包括支撑装置1、压力装置2、膜箱3和推力装置4，具体结构如下：
结合图3所示，支撑装置包括底板1.1、顶板1.2、支撑梁1.3和多根支撑柱1.4；底板和顶板均为圆形钢板，底板的中心部位设有用于桩试样5插入的通孔A，顶板的中心部位设有用于桩试样5插入的通孔B，通孔A与通孔B上下同轴设置且孔径大小相等。底板和顶板上均设有沿其中心周向均布的多个定位装置，每个定位装置均包括沿底板(顶板)径向方向设置的长槽孔1a、设置在长槽孔长度方向两侧的卡柱1b和用于定位推板在支撑装置上的内外位置的插销1c。
具体地，支撑柱的数量优选3根，该3根支撑柱均贯穿底板和顶板设置，支撑柱的底端比底板低60cm，支撑柱的顶端比顶板高50cm；方便对桩试样进行测试。支撑梁位于顶板的上方，该支撑梁为三叉型梁，每个梁叉上设有一个连接孔，梁叉通过连接孔与支撑柱固定连接；通孔C设置在支撑梁的中心部上。
进一步的，压力装置包括竖向加载装置2.1、传力杆2.2、压力传感器2.3和位移传感器2.4；竖向加载装置为设置在支撑梁上的伺服液压机；传力杆上下贯穿通孔C设置，传力杆的顶端与竖向加载装置相连，传力杆的底端用于与桩试样的顶端相接触；位移传感器设置在传力杆用于与桩试样接触的端面上，压力传感器与位移传感器相连接，并夹设在位移传感器与桩试样之间。该结构中，竖向加载装置通过传力杆将竖向压力施加在桩试样上；位移传感器用于检测桩试样的位移，压力传感器用于感应伺服液压机对桩试样所施加的压力。
结合图4所示，膜箱竖向设置在底板上，其包括圆形的膜筒3.1、透水板3.2和封盖3.3；膜箱还包括将封盖与膜筒压紧的3个压紧杆3.4；顶板上设有与3个通孔F，每个通孔F内穿设一压紧杆。透水板设置在膜筒的底部并将膜筒的下端口堵住，封盖用于密封膜 筒的上端口；膜筒用于套设在桩试样的径向外侧，且当桩试样插设在膜箱内时，膜筒与桩试样之间具有容置土试样的容置腔。透水板和封盖上分别设有通孔D和通孔E；试验时，桩试样的上、下两端分别贯穿通孔E和通孔D设置。具体地，膜筒由橡胶膜制成；为了防止脱水板对推力装置施加的水平力产生不利影响，透水板由设置在其中心的圆形透水板本体和设置在该透水板本体外周侧的柔性膜，通孔D设置在透水板本体的中心；该柔性膜分别与膜筒和透水板密封连接；优选的，柔性膜也为橡胶膜。封盖为活动盖设在膜筒上端的钢板，并通过压紧杆将封盖压紧在膜筒(膜筒内装有土试样)上，防止试验时膜箱内的土试样向上冒出而导致压力失效。该结构设置既方便往膜筒内填装土试样，又不会对膜筒径向受压时膜筒缩小直径造成不利影响，从而避免影响模拟效果。
结合图5所示，推力装置套设在膜筒上，用于向膜筒施加多个水平推力以对膜筒内的土试样沿垂直于桩试样轴向的方向进行挤压，多个水平推力从上到下线性递增。具体地，推力装置包括推力筒组、沿推力筒组中心周向均布的多个推力组件以及套设在推力筒组外周壁上的防护筒4.5；需要特别说明的，为了便于更清晰的显示推力装置的内部结构，图5中的防护筒未示出，但本领域技术人员可以理解的，推力杆的外端与推板固定连接，推力杆的内端贯穿防护筒的侧孔后与推力筒的弧形钢板固定连接；套设在推力杆上的推力弹簧也贯穿该侧孔，且至少在推力作用时与弧形钢板接触并对其产生水平推力。
结合图6和图7所示，推力筒组包括可径向收缩的多个推力筒4.1，多个推力筒大小相等且沿其轴向叠加设置在底板上，且相邻两推力筒之间不固连；上下相邻两个推力筒4.1之间、最顶层的推力筒与封盖3.3之间以及最低层的推力筒与底板1.1之间做润滑处理。侧向受水平推力时，每个推力筒根据其所受水平压力的大小而径向收缩，进而对膜箱内的土试样和桩试样上下施加不同的压力。优选的，推力筒为双层筒体结构，内层筒体与外层筒体同轴套装，内层筒体由沿其周向均匀间隔设置的多片弧形钢片4.1a围成，外层筒体由沿其周向均匀间隔设置的多块弧形钢板4.1b围成，两相邻弧形钢板的间隔缝与两相邻弧形钢片的间隔缝内外错开设置，且每一块弧形钢板均与位于其内侧的两片弧形钢片能在推力筒的周向上水平滑动配合。当推力筒侧向受水平压力时，相邻两块弧形钢板以及相邻两片弧形钢片的间隔缝变小，包覆在膜筒外侧壁上的推力筒的直径变小。
每个推力组件均包括一竖向布置的推板4.2、水平状布置且可伸缩的多根推力杆4.3和多个推力弹簧4.4，多根推力杆4.3在同一竖直面内沿上下方向布置，多根推力杆的外端均 与推板相连，多根推力杆的内端与弧形钢板分别相连且推力杆和弧形钢板一一对应设置；每根推力杆上套设有一推力弹簧。该结构中，上下叠加设置的多个推力筒的弧形钢板也上下对应设置，同一列弧形钢板称为一组；每个推力组件包括的推力杆数量与一组弧形钢板中弧形钢板的数量相等，推力组件的个数与弧形钢板的组数相等。推板的上下两端贯穿分别贯穿顶板和底板上的长槽孔设置，并在长槽孔内沿该孔的长度方向移动。
结合图8所示，防护筒的侧壁上开设有多个侧孔4.5a，用于推力杆及推力弹簧穿设；防护筒可有效防止膜筒内的土试样产生向外的张力而对膜筒造成损坏。
本发明中，推力杆与弧形钢板一一对应设置；与同一推力筒相连的同一层推力杆位于同一水平面内，且同一层推力杆的内端均指向推力筒的中轴线。具体地，推力杆包括实心杆4.3a和空心杆4.3b，实心杆的内端与弧形钢板的外壁相连，实心杆的外端插设在空心杆中。推板被向内移动一定距离后，将插销置于推板外侧且插在两相邻卡柱之间以定位推板，推力弹簧被压缩并对推力筒施加侧向水平压力，而推力杆的长度由推板和推力弹簧共同确定。本发明中，推力筒所受的水平压力可根据推力弹簧的弹性系数以及推力弹簧的压缩量来计算获得。
本发明中，多个推力筒的叠加高度与膜筒的高度相等，推力筒包覆在膜筒的外周壁上；便于推力装置对膜箱内的桩试样和土试样施加水平推力。
采用本发明的桩土接触面剪切力学特性试验装置对桩土接触面剪切力学特性进行试验，通过推力装置对推力筒施加水平压力使其径向收缩，进而对膜箱内的土试样施加上下大小不同的水平推力，有效模拟桩土在实际工程中所受水平地压，有利于桩土试验的研究。具体的试验方法包括以下步骤：
(1)、按工程实际预制桩试样5，并准备与实际工程相同土质的土试样6。
(2)、装置桩试样、土试样：先将预制的桩试样5从试验装置的顶部插入膜筒3.1中，再将备好的土试样6填筑到膜筒中，并根据实际工程压实土试样，压实完成后将封盖3.3盖到膜筒上，并通过压紧杆3.4将封盖与膜筒压紧。
(3)、安装压力装置：将竖向加载装置2.1可拆卸安装在支撑梁上，桩试样的顶端通过传力杆2.2与竖向加载装置相连，桩试样与传力杆之间夹设有压力传感器2.3和位移传感器2.4；竖向加载装置优选伺服液压机。
(4)、对桩土施加水平推力：在膜筒的外周侧向其中轴线方向施加多层水平推力，以对所述膜筒内的土试样沿垂直于桩试样轴向的方向进行挤压，多层水平推力从上到下线性递增；当顶层推力和底层推力对土试样产生的压强与实际工程中要测量桩段的上截面和下截面处压强分别相等时，维持各层水平推力不变。“桩段”指根据工程需要选取桩的一部分或者整根桩。
(5)、桩土接触面剪切试验：启动竖向加载装置对桩试样施加竖向压力，在竖向压力所用下，桩试样在竖向发生移动，桩试样所受压力和位移，分别通过压力传感器和位移传感器获得。
(6)、桩土接触面剪切力计算：根据桩土接触面剪切试验获取的试验数据计算桩土接触面剪切应力，桩土接触面剪切应力J G＝J S×L G/L T，J S为本发明试验获取的剪应力，L G为桩试样的长度，L T为顶层推力弹簧与底层推力弹簧的间距。具体地，“桩试样的长度”为选取整个桩的长度或选取桩的其中一段的长度，只要保证试验装置的水平压力和选取实际工程桩的水平地压相等即可。
上述步骤(4)可通过下述两种方法实现对桩土施加水平推力，具体地：
第一种方法：套设在同一层推力杆上的推力弹簧的自由长度相等，且从上至下每层推力杆上的推力弹簧的弹性系数线性递增。安装好桩试样和土试样后，通过向内(膜筒中轴线方向)调整推板，此时推力杆的长度缩短，进而套设在推力杆上的推力弹簧被压缩，推力弹簧给予桩土接触面从上到下呈线性增加的水平压力，这与桩土在实际工程中所受水平地压随深度的增加而不断增加的情况一致；可以真实的模拟桩土覆土压力的分布，尤其适用于长桩。
第二种方法：空心杆上设置有螺母(空心杆上设置有螺纹)，推力弹簧设置在螺母与弧形钢板之间，且所有推力弹簧的长度和弹性系数均相等。安装好桩试样和土试样后，从上至下调整每层推力杆上的螺母距离推力筒的距离线性递减；再通过向内调整推板，使得推力弹簧给予桩土接触面从上到下呈线性增加的水平压力。该结构还可扩大推力弹簧给予桩土压力的适用范围，可以不调整桩土接触度，通过调整螺母对推力弹簧的压缩量改变从上到下推力弹簧给予桩土接触面压强增大的速率，适应实际工程不同长度桩与土接触面剪切试验。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种桩土接触面剪切力学特性试验装置，其特征在于，包括支撑装置(1)、压力装置(2)、膜箱(3)和推力装置(4)；所述支撑装置包括底板(1.1)、顶板(1.2)和支撑梁(1.3)，底板和顶板通过多根支撑柱(1.4)相连，所述支撑梁设置在顶板的上方；所述压力装置设置在所述支撑梁上，用于向桩试样(5)施加竖向压力；所述膜箱的膜筒(3.1)竖向设置在所述底板上且套设在桩试样的径向外侧，所述膜筒与桩试样之间具有容置腔；所述推力装置套设在所述膜筒上，用于向所述膜筒施加多个水平推力以对所述膜筒内的土试样(6)沿垂直于桩试样轴向的方向进行挤压，多个水平推力从上到下线性递增。
  2. 根据权利要求1所述的桩土接触面剪切力学特性试验装置，其特征在于，所述推力装置包括推力筒组、沿所述推力筒组中心周向均布的多个推力组件以及套设在所述推力筒组外周壁上的防护筒(4.5)；
    所述推力筒组包括可径向收缩的多个推力筒(4.1)，多个所述推力筒沿其轴向叠加设置在所述底板上，且相邻两所述推力筒之间不固连；
    每个所述推力组件均包括一竖向布置的推板(4.2)、水平状布置且可伸缩的多根推力杆(4.3)和多个推力弹簧(4.4)，多根推力杆(4.3)在同一竖直面内沿上下方向布置，多根推力杆的外端均与推板相连，多根推力杆的内端与推力筒分别相连且推力杆和推力筒一一对应设置；每根推力杆上套设有一所述推力弹簧；
    所述防护筒的侧壁上开设有多个侧孔(4.5a)，用于所述推力杆及所述推力弹簧穿设。
  3. 根据权利要求2所述的桩土接触面剪切力学特性试验装置，其特征在于，所述推力筒为双层筒体结构，内层筒体与外层筒体同轴套装，所述内层筒体由沿其周向均匀间隔设置的多片弧形钢片(4.1a)围成，所述外层筒体由沿其周向均匀间隔设置的多块弧形钢板(4.1b)围成，两相邻弧形钢板的间隔缝与两相邻弧形钢片的间隔缝内外错开设置，且每一块弧形钢板均与位于其内侧的两片弧形钢片能在所述推力筒的周向上水平滑动配合；多根推力杆的内端与弧形钢板分别相连且推力杆和弧形钢板一一对应设置；
    与同一所述推力筒相连的同一层推力杆位于同一水平面内，且同一层推力杆的内端均指向所述推力筒的中轴线。
  4. 根据权利要求3所述的桩土接触面剪切力学特性试验装置，其特征在于，所述推力杆包括实心杆(4.3a)和空心杆(4.3b)，所述实心杆的内端与所述弧形钢板的外侧壁相连，所述实心杆的外端滑动插设在所述空心杆内。
  5. 根据权利要求4所述的桩土接触面剪切力学特性试验装置，其特征在于，套设在同一层推力杆上的推力弹簧的自由长度相等，且从上至下每层推力杆上的推力弹簧的弹性系数线性递增。
  6. 根据权利要求4所述的桩土接触面剪切力学特性试验装置，其特征在于，所述空心杆上设置有螺母(4.3c)，所述推力弹簧设置在所述螺母与所述弧形钢板之间，且所有推力弹簧的自由长度和弹性系数均相等。
  7. 根据权利要求2所述的桩土接触面剪切力学特性试验装置，其特征在于，所述底板和顶板均为圆形板，所述底板和顶板上均设有沿其中心周向均布的多个定位装置，每个所述定位装置均包括沿所述底板径向方向设置的长槽孔(1a)、设置在所述长槽孔长度方向两侧的卡柱(1b)和用于定位所述推板在所述支撑装置上的内外位置的插销(1c)。
  8. 根据权利要求1所述的桩土接触面剪切力学特性试验装置，其特征在于，所述底板和所述顶板上分别设有用于所述桩试样插入的通孔A和通孔B，所述通孔A与所述通孔B同轴设置；多根所述支撑柱均上下贯穿所述底板和所述顶板设置；所述支撑梁与多根所述支撑柱连接，所述支撑梁上设有通孔C；
    所述压力装置包括竖向加载装置(2.1)、传力杆(2.2)、压力传感器(2.3)和位移传感器(2.4)；所述竖向加载装置可拆卸设置在所述支撑梁上；所述传力杆贯穿所述通孔C设置，其一端与所述竖向加载装置相连、另一端用于与所述桩试样的顶端相接触；所述压力传感器和所述位移传感器夹设在所述传力杆与所述桩试样之间；
    所述膜箱包括膜筒(3.1)、透水板(3.2)和封盖(3.3)；所述膜筒由柔性材料制成；所述透水板设置在所述膜筒内并将膜筒的下端口堵住，所述封盖设置在所述膜筒的顶部并将膜筒的上端口密封；所述透水板和封盖上分别设有通孔D和通孔E，所述桩试样的上、下两端分别贯穿所述通孔E和通孔D设置。
  9. 根据权利要求8所述的桩土接触面剪切力学特性试验装置，其特征在于，所述透水板包括透水板本体和设置在透水板本体周边的柔性膜，所述通孔D设置在透水板本体上；所述膜箱还包括将封盖与所述膜筒压紧的至少三根压紧杆(3.4)；所述顶板上设有与多个通孔F，每个所述通孔F内穿设一所述压紧杆，所述压紧杆的下端用于压在所述封盖上。
  10. 根据权利要求8所述的桩土接触面剪切力学特性试验装置，其特征在于，所述支撑装置包括3根支撑柱，所述支撑柱的底端比所述底板低50～200cm，所述支撑柱的顶端比所述顶板高30～200cm；所述支撑梁为三叉型梁，每个梁叉与一根所述支撑柱固定连接。
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