WO2021244185A1 - Appareil et procédé d'essai pour simuler l'influence d'une cavité existant sur une extrémité de pieu sur la performance de palier de fondation de pieu - Google Patents

Appareil et procédé d'essai pour simuler l'influence d'une cavité existant sur une extrémité de pieu sur la performance de palier de fondation de pieu Download PDF

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Publication number
WO2021244185A1
WO2021244185A1 PCT/CN2021/089804 CN2021089804W WO2021244185A1 WO 2021244185 A1 WO2021244185 A1 WO 2021244185A1 CN 2021089804 W CN2021089804 W CN 2021089804W WO 2021244185 A1 WO2021244185 A1 WO 2021244185A1
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Prior art keywords
pile
water injection
cavity
model
sand layer
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PCT/CN2021/089804
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English (en)
Chinese (zh)
Inventor
周佳锦
龚晓南
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浙江大学
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Publication date
Application filed by 浙江大学 filed Critical 浙江大学
Priority to JP2022504726A priority Critical patent/JP7236781B2/ja
Publication of WO2021244185A1 publication Critical patent/WO2021244185A1/fr

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D33/00—Testing foundations or foundation structures

Definitions

  • the invention relates to a test device for studying the influence of the existence of an underground cavity on the bearing performance of a pile foundation in the field of geotechnical engineering.
  • the current research on underground cavities mainly focuses on the shallow underground cavities and the influence of the existence of underground cavities on the stability of road subgrade. There is no research on the bearing performance of the building foundation when the underground cavities are deep. When there is a cavity near the pile end of a building's pile foundation, it will affect the bearing performance of the pile foundation. When the distance between the cavity and the pile end is relatively close or the cavity volume is large, the ultimate bearing capacity of the pile foundation will be greatly reduced. , And may cause the building to collapse, causing serious loss of life and property.
  • the purpose of the present invention is mainly to study the influence on the bearing performance of the pile foundation when there is a cavity near the pile end, which can be used to simulate the influence on the bearing performance of the pile foundation when the cavity position is different and the cavity size is different.
  • a test device for simulating the influence of a cavity near the end of the pile on the bearing performance of the pile foundation including a semicircular model box, a plexiglass plate, a water injection system, a loading motor, and an industrial camera;
  • the semicircular model box is composed of a model box base and a semicircular model box frame welded on the base;
  • the model box base is composed of a bottom plate and a support, and the bottom plate is directly welded to the support;
  • Water injection holes are arranged at certain intervals;
  • the plexiglass plate is fixed on the frame of the semicircular model box as an observation surface;
  • the bottom of the semicircular model box is filled with a sand layer of a certain thickness;
  • the sand layer A clay layer is filled on it; marking points need to be arranged during the filling process of the sand layer to observe the displacement of the sand layer during the test;
  • the sand layer area inside the plexiglass plate is equipped with a control for image analysis
  • the inside of the plexiglass plate is also covered with a thin plexiglass plate so that the control point will not move during the test; an earth pressure sensor is also embedded in the sand layer to test the soil pressure at the end of the pile during
  • the model piles can be prefabricated piles or on-site cast-in-place piles.
  • the cross-section of the model piles is semicircular;
  • the water injection system consists of an air compressor, It is composed of a water storage tank and a water injection pipe. One end of the water injection pipe is connected to the water storage tank, and the other end enters the sand layer through the water injection hole on the bottom plate; the loading motor is fixed above the semicircular model box; for the industrial camera During the test, photographs of the sand layer in the semi-circular model box were taken at regular intervals to record the displacement of the sand layer during the test.
  • the ratio of the diameter of the semicircular model box frame to the diameter of the model pile is not less than 10;
  • the distance between the end of the model pile and the bottom plate is not less than 20 times the diameter of the model pile.
  • the pile end of the model pile needs to enter the sand layer 1-3, and the depth of the pile end into the sand layer needs to be greater than 2 times the diameter of the model pile.
  • the earth pressure sensor is arranged at different depths and different distances below the end of the model pile to measure the vertical earth pressure.
  • the model pile may be a prefabricated pile or an on-site cast-in-place pile. If it is a prefabricated pile, after the soil is filled, the model pile is pressed into the soil by a loading motor; if it is an on-site cast-in-place pile, the soil After the filling of the body is completed, drill holes and pour model piles in the drilled space.
  • water injection holes on the bottom plate of the model box at regular intervals, and in each test, one of the water injection holes is opened and the other water injection holes are closed.
  • the water injection system uses an air compressor to inject water into the water injection hole, simulating the process of overflowing from a broken underground pipeline.
  • the sand layer in the model box is affected by the water flow at the water injection hole, internal erosion will occur, and a cavity will be generated near the water injection hole.
  • the size of the cavity is adjusted according to the water injection pressure and the water injection time. Stop water injection when the test requirements are met.
  • the semicircular model box frame is provided with two pillars, the loading motor is fixed above the semicircular model box through the two pillars, and the beam of the loading motor can be vertically moved along the pillars through pulleys. Move, thereby driving the loading motor to move up and down.
  • the photos taken by the industrial camera can be analyzed through the computer program to obtain the sand displacement changes in the sand layer during the test.
  • the present invention also provides a test method for simulating the impact on the bearing performance of the pile foundation when there is a cavity at the end of the pile.
  • the method is implemented based on the above device and includes the following steps:
  • Mark points are arranged during the sand layer filling process to observe the displacement change of the sand layer during the test; at the same time, during the sand layer filling process, different depths below the pile end of the model Several soil pressure sensors are buried at different distances; after the sand layer is filled, a clay layer is filled on it; after the clay layer is filled, the model piles are placed in the semi-circular model box, and the model piles are prefabricated piles or on-site pouring Pile: After the model pile is set up, open a certain water injection hole on the bottom plate, and inject water from the water injection hole into the sand layer through the water injection system, so that a cavity appears near the water injection hole.
  • the size of the cavity can be adjusted according to the water injection pressure and water injection time. Control (the development process of the cavity can be directly observed through the plexiglass plate). During the water injection process, the sandy soil area is photographed by an industrial camera; after the cavity size reaches the design requirements, the water injection hole is closed, and the model pile is loaded by the loading motor. During the process, the industrial camera took pictures of the sandy soil layer area.
  • a water injection system is used to inject water through a water injection hole set at the bottom of the model box, which can simulate the overflow of broken underground pipelines and the resulting voids in the soil layer.
  • the formation process of the hollow hole in the bottom water injection sand layer can be analyzed by the particle image velocity method, and the sand during the loading process of the model pile The displacement changes of sand particles in the soil layer.
  • the position relationship between the underground cavity and the pile foundation and the size of the underground cavity can be adjusted, and the law of influence on the bearing performance of the pile foundation can be studied when the relative position of the cavity and the pile foundation are different and the size of the cavity is different.
  • Figure 1 is a schematic front view of the test device
  • Figure 2 is a top view of the test device
  • Figure 3 is a schematic diagram of the bottom water injection process
  • Figure 4 is a schematic diagram of the test device when the cavity is small
  • Figure 5 is a schematic diagram of the test device when the cavity is large
  • semicircular model box 1 model box base 1-1, bottom plate 1-1-1, support 1-1-2, water injection hole 1-1-3, semi-circular model box frame 1-2, Sand layer 1-3, clay layer 1-4, model pile 1-5, marking point 1-6, earth pressure sensor 1-7, cavity 1-8, plexiglass plate 2, control point 2-1, second Plexiglass plate 2-2, water injection system 3, air compressor 3-1, pressure gauge 3-1-1, pressure regulating switch 3-1-2, water storage tank 3-2, water injection pipe 3-3, water injection valve 3-3-1, load motor 4, pillar 4-1, beam 4-2, pulley 4-3, industrial camera 5.
  • test device As shown in Figures 1-5, it is a test device that can simulate the impact on the bearing performance of the pile foundation when there is a cavity near the pile end. At the same time, it can test the bearing performance of the pile foundation when the relative position of the cavity and the pile foundation are different, and the size of the cavity is different. Research on the law of influence.
  • the test device includes five parts: semicircular model box 1, plexiglass plate 2, water injection system 3, loading motor 4 and industrial camera 5.
  • the semicircular model box 1 is composed of a model box base 1-1 and a semicircular model box frame 1-2 welded on the model box base 1-1;
  • the model box base 1-1 is composed of a bottom plate 1-1 -1 and the support 1-1-2, the bottom plate 1-1-1 is directly welded to the support 1-1-2;
  • the thickness of the bottom plate 1-1-1 is 50mm, and the bottom plate 1-1-1
  • the semicircular model box frame 1-2 is a semicircular arc made of 10mm thick steel plate, The diameter is 2m;
  • the plexiglass plate 2 is fixed on the semicircular model box frame 1-2 as an observation surface, and the thickness of the plexiglass plate 2 is 10mm;
  • the interior of the semicircular model box 1 is first filled in the bottom The thickness of the sand layer 1-3; during the filling process of the sand layer 1-3, marking points 1-6 need to be
  • the horizontal and vertical spacing of the marking points is generally between Between 20-50mm, it is necessary to bury several soil pressure sensors 1-7 at different depths and distances below the pile ends of model piles 1-5; 4; After the clay layer 1-4 is filled, the model piles 1-5 are placed in the model box.
  • the model piles can be prefabricated piles or on-site cast-in-place piles, and the diameter of the model piles needs to be less than 200mm; the plexiglass board 2Fixed on the semicircular model box frame 1-2 as the observation surface, the inside of the plexiglass plate 2 is filled with sandy soil layer 1-3, and the control points 2-1 for image analysis are pasted, and the control points are horizontal and vertical.
  • the spacing is generally 100-200mm, and then a thin second plexiglass plate 2-2 is covered on the inside of the plexiglass plate 2, so that the control point 2-1 will not move during the test; the water injection system 3 is compressed by air The machine 3-1, the water storage tank 3-2 and the water injection pipe 3-3.
  • One end of the water injection pipe 3-3 is connected to the water storage tank 3-2, and the other end enters through the water injection hole 1-1-3 on the bottom plate Sand layer 1-3;
  • the semicircular model box frame 1-2 is welded with two pillars 4-1, the loading motor 4 is fixed on the top of the model box through the two pillars 4-1, and the loading motor
  • the beam 4-2 can be moved in the vertical direction along the pillar 4-1 through the pulley 4-3, thereby driving the loading motor 4 to move up and down;
  • the industrial camera 5 photographs the sand and soil in the model box at regular intervals during the test
  • the photos of layers 1-3 record the displacement changes of the sand layer during the test.
  • test method of the present invention for simulating the influence on the bearing performance of the pile foundation when there is a cavity at the end of the pile is as follows:
  • model piles 1-5 are placed in the soil layer.
  • the model piles can be prefabricated piles or on-site cast-in-place piles. When the model piles are prefabricated piles, load the motor after the soil is filled. Press the model pile 4 to press the prefabricated pile into the soil.
  • model pile When the model pile is an on-site cast-in-place pile, drill the hole after the soil is filled and pour the model pile in the drilled space; after the model pile is set, it will be A certain water injection hole 1-1-3 on the bottom plate 1-1-1 of the model box is opened, and the water is injected from the water injection hole 1-1-3 into the sand layer 1-3 through the water injection system 3, so that a water injection hole appears near the water injection hole 1-1-3.
  • Cavities 1-8, the size of the cavity can be controlled according to the water injection pressure and water injection time.
  • the development process can be directly observed through the plexiglass plate), during the water injection process, the sand layer 1-3 areas are photographed by the industrial camera 5; after the hole size meets the design requirements, the water injection hole 1-1-3 is closed, and the motor 4 is loaded Load the model piles 1-5, and during the loading process, the industrial camera 5 photographs the sandy soil layer 1-3 areas.
  • the load and displacement applied by the loading motor 4 can be automatically read and stored.
  • the soil pressure change law of the soil at the end of the pile is automatically measured by a static strain tester, and the displacement change law of the sand particles in the sand layer during the test.
  • the photos taken by industrial cameras can be analyzed by computer software.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
  • Foundations (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

La présente invention concerne un appareil et un procédé d'essai pour simuler une influence d'une cavité existant à proximité d'une extrémité de pieu sur la performance de palier d'une fondation de pieu. L'appareil d'essai comprend une boîte de modèle semi-circulaire, une plaque de verre organique, un système d'injection d'eau, un moteur de chargement et une caméra industrielle. Selon la présente invention, le système d'injection d'eau est utilisé pour injecter de l'eau dans une couche de sol sableux dans la boîte de modèle pour simuler le cas où une canalisation souterraine est rompue et l'eau déborde et le cas résultant où une cavité apparaît dans une couche de sol ; un point de commande et un point de repère sont disposés dans une zone de couche de sol sableux, et le processus de formation de cavité et le déplacement de particules de sol sableux dans la couche de sol sableux pendant le processus de chargement d'un pieu modèle sont analysés au moyen du procédé de vélocimétrie d'image de particules et selon une photo prise par la caméra industrielle. La présente invention présente une structure raisonnable et une opération simple, peut être utilisée pour étudier l'influence de la cavité existant à proximité de l'extrémité de pieu sur les performances de palier de la fondation de pieu, et la règle d'influence de différentes positions de cavité et différentes tailles de cavité sur les performances de palier de la fondation de pieu, et fournit un moyen efficace pour étudier l'influence de la cavité existant à proximité de l'extrémité de pieu sur les performances de palier de la fondation de pieu.
PCT/CN2021/089804 2020-06-01 2021-04-26 Appareil et procédé d'essai pour simuler l'influence d'une cavité existant sur une extrémité de pieu sur la performance de palier de fondation de pieu WO2021244185A1 (fr)

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JP2022504726A JP7236781B2 (ja) 2020-06-01 2021-04-26 杭端に空洞が存在することによる杭基礎の軸受性能への影響をシミュレーションする試験装置及び試験方法

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CN115369932A (zh) * 2022-08-31 2022-11-22 广州地铁设计研究院股份有限公司 一种室内工程桩模型的承载力试验装置及试验方法

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CN114277858B (zh) * 2021-11-30 2023-07-18 中国能源建设集团安徽电力建设第一工程有限公司 一种孤石地层管桩沉降及应变测量的室内模拟试验装置

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CN115369932A (zh) * 2022-08-31 2022-11-22 广州地铁设计研究院股份有限公司 一种室内工程桩模型的承载力试验装置及试验方法
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