CN111413485A - Small hole expansion test device and method - Google Patents

Small hole expansion test device and method Download PDF

Info

Publication number
CN111413485A
CN111413485A CN202010227635.0A CN202010227635A CN111413485A CN 111413485 A CN111413485 A CN 111413485A CN 202010227635 A CN202010227635 A CN 202010227635A CN 111413485 A CN111413485 A CN 111413485A
Authority
CN
China
Prior art keywords
elastic membrane
pressure
water
soil
expander
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202010227635.0A
Other languages
Chinese (zh)
Inventor
马建军
黄林冲
梁禹
赖正首
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sun Yat Sen University
National Sun Yat Sen University
Original Assignee
National Sun Yat Sen University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Sun Yat Sen University filed Critical National Sun Yat Sen University
Priority to CN202010227635.0A priority Critical patent/CN111413485A/en
Priority to CN201910535486.1A priority patent/CN110208493B/en
Publication of CN111413485A publication Critical patent/CN111413485A/en
Pending legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24Earth materials
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00Measuring arrangements or details thereof in so far as they are not adapted to particular types of measuring means of the preceding groups
    • G01B21/02Measuring arrangements or details thereof in so far as they are not adapted to particular types of measuring means of the preceding groups for measuring length, width, or thickness
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00Sampling; Preparing specimens for investigation
    • G01N1/28Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/286Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/08Investigating permeability, pore-volume, or surface area of porous materials
    • G01N15/0806Details, e.g. sample holders, mounting samples for testing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G01N3/10Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
    • G01N3/12Pressure testing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003Generation of the force
    • G01N2203/0042Pneumatic or hydraulic means
    • G01N2203/0048Hydraulic means

Abstract

The invention discloses a small hole expansion test device and a method, wherein an expander is embedded in saturated soft clay, a plurality of soil pressure cells and pore water pressure sensors are radially arranged at intervals on a plane where the cross section of an elastic membrane of the expander is located, the radial expansion of the elastic membrane can be realized by controlling the internal pressure of a closed space, so as to simulate the mechanical behavior of small hole expansion, meanwhile, the data of the hydraulic sensors, the pore water pressure sensors and the soil pressure cells are obtained by a monitoring device, the internal pressure change of the closed space before and after the expansion of the elastic membrane and the change situation of the pore pressure and the radial stress around the elastic membrane are obtained, the displacement change situation of the top of the saturated soft clay before and after the expansion of the elastic membrane is obtained by the auxiliary measurement of the auxiliary reference of surface displacement measurement, and finally, the data of the pore pressure, the radial stress, the surface displacement and the like obtained by, to assist in obtaining a constitutive model that can accurately explain the small pore expansion in saturated soft clay.

Description

Small hole expansion test device and method
Technical Field
The invention relates to the technical field of small hole expansion tests, in particular to a small hole expansion test device and a small hole expansion test method.
Background
When external objects (such as pile foundations, feeler levers and the like) are pressed into the rock-soil medium under the action of acting force, the rock-soil medium at the original position can be squeezed open and generate displacement. Therefore, the deformed rock-soil body generates pressure on the entering object, and the stress field and the displacement field of the rock-soil body around the object can be changed. In order to explore the changes of stress, displacement, pore water pressure and the like of rock-soil media around an object caused by the 'squeezing in' of an external object, the problem of interaction between the end part of the object and a rock-soil body is simplified into the expansion of a spherical small hole, and the interaction between the non-end part and the rock-soil body is simplified into the expansion of a cylindrical small hole.
As shown in FIG. 1, taking the expansion of a spherical pore as an example, a saturated soft clay hollow sphere has an inner radius of R, an outer radius of R, an internal pressure of p, and an external pressure of p0When the ball hole expands or contracts under the influence of external force, the inner diameter, the outer diameter, the inner pressure and the outer pressure of the ball hole are changed, and the pore water pressure and the displacement of the soil body are changed. Therefore, the stress and the displacement of the soil body can be researched according to the theory of small hole expansion, and whether the soil body reaches a critical state or not and whether the structure has the risk of damage or not can be judged. In addition, the external pressure P of the small hole can be reversely obtained according to the expansion solution of the small hole and the test data in the engineering0The distribution of initial stress is tested (the hydraulic fracturing method is the principle); or the bearing capacity of the foundation (or the end resistance and the side resistance of the pile foundation and the anchor rod) is obtained through the solution of the column hole expansion and the strength parameter of the soil body. In the soilIn wood engineering, for example, in the cases of tunnel excavation, anchor rod drilling, well drilling and the like, complete soil is excavated and lost, and small holes generated by excavation under the action of ground stress can contract and deform, so that the problems of instability of hole walls and the like are generated. The research on the problem of the expansion of the small holes in the saturated clay can provide help for the prediction of tunnel excavation deformation in a soft soil area, the stability of drilling and the like.
Whether the research on the problem of the small hole expansion in the saturated clay can provide help for tunnel excavation deformation prediction, drilling stability and the like in soft soil areas is mainly characterized by whether a constitutive model for accurately explaining the small hole expansion in the saturated soft clay can be obtained, the acquisition of the constitutive model is mainly characterized by whether the mechanical behavior of the small hole expansion in the saturated soft clay can be accurately simulated, and the stress, the displacement and the pore water pressure distribution of the rock-soil body are calculated according to a mechanical balance equation, a compatible equation of rock-soil body deformation and the constitutive model of the rock-soil body on the basis of data such as the stress, the pore pressure and the displacement of the rock-soil body obtained by a simulation test.
The current simulation methods for pinhole expansion include: centrifugal model test methods, which can be combined with the test of hole expansion, but centrifuge tests are expensive; in addition, other materials such as rocks, rubber, etc. have been used by researchers to simulate the mechanical behavior of small hole expansion. In general, there has been little experimental study to simulate the expansion and contraction problems of cylindrical and spherical pores in saturated soft clay, and no similar model experimental design.
Disclosure of Invention
The invention mainly aims to provide a small hole expansion test device and a small hole expansion test method, which aim to accurately simulate the mechanical behavior of small hole expansion in saturated soft clay so as to assist in obtaining a constitutive model capable of accurately explaining the small hole expansion in the saturated soft clay.
In order to achieve the above object, the present invention provides a small hole expansion test device, comprising:
the model box is filled with saturated soft clay;
the expander is embedded in the saturated soft clay and comprises a rigid support body and an elastic membrane, the elastic membrane is directly connected with the support body or connected with the support body through an intermediate piece to surround part or all of the support body to form a columnar or spherical closed space, the support body or the elastic membrane is connected with a water injection pipe and a water outlet pipe which are communicated with the closed space and the outside, the water injection pipe is communicated with a water supply device positioned outside the model box, the water outlet pipe extends to the outside of the model box directly or through an intermediate connecting pipe, the water outlet pipe is provided with a water outlet control valve, a hydraulic sensor for detecting the internal pressure is also arranged in the closed space, and when the internal pressure of the closed space changes, the elastic membrane can realize;
the soil pressure boxes are embedded in the saturated soft clay, are distributed at intervals in the radial direction of the plane where the cross section of the elastic membrane is located, and are used for detecting the change of radial stress around the elastic membrane before and after the elastic membrane is expanded;
the pore water pressure sensors are embedded in the saturated soft clay, radially distributed on the plane where the cross section of the elastic membrane is located at intervals and used for detecting the change of the pore pressure around the elastic membrane before and after the elastic membrane expands;
the auxiliary reference for measuring the surface displacement is arranged in a region above the saturated soft clay corresponding to the expander and is used for assisting in measuring the displacement change of the top of the saturated soft clay before and after the expansion of the elastic membrane; and
the monitoring system is used for acquiring detected data of the hydraulic sensor, the pore water pressure sensor and the soil pressure cell before and after the elastic membrane is expanded;
the expander is a spherical expander, a supporting body of the spherical expander comprises a rigid hollow sphere, a plurality of through holes are formed in the wall of the hollow sphere, the elastic membrane is in a spherical shell shape and surrounds the hollow sphere to form the spherical closed space, the hydraulic sensor is arranged on the outer wall of the hollow sphere, a pressure measuring cable of the hydraulic sensor extends out of the closed space from the spherical shell-shaped elastic membrane, the matching position of the pressure measuring cable and the elastic membrane is sealed, a water inlet hole is formed in the hollow sphere, the water injection pipe extends into the elastic membrane and then is installed in the water inlet hole, the matching position of the elastic membrane and the water injection pipe is sealed, the elastic membrane is further provided with the water outlet hole for installing a water outlet pipe, and the water outlet pipe partially extends into the elastic membrane and is communicated with the space where the gap between the hollow sphere and the elastic membrane is located.
The invention also provides a small hole expansion test method, which comprises the following steps:
s1, according to the test requirements, in the process of adding saturated soft clay into a model box in a layered mode and compacting, placing an expander, a plurality of pore water pressure sensors and a plurality of soil pressure boxes into the model box so that the expander, the plurality of pore water pressure sensors and the plurality of soil pressure boxes are buried in the saturated soft clay in the model box, wherein a closed space is filled with water and certain initial internal pressure is kept;
s2, acquiring and recording initial internal pressure values detected by the pore water pressure sensors, the soil pressure boxes and the hydraulic sensors in the closed space through a monitoring system;
s3, arranging an auxiliary reference for measuring the displacement of the earth surface above the saturated soft clay corresponding to the area of the dilator, and measuring the initial position of the earth surface;
s4, increasing or decreasing the water quantity in the closed space through the cooperation of the water outlet control valve and the water supply device until the water pressure of the closed space is increased or decreased to a preset value, so that the elastic membrane radially expands or contracts and drives the saturated soft clay around the elastic membrane to deform;
and S5, acquiring new values detected by the plurality of pore water pressure sensors, the plurality of soil pressure boxes and the hydraulic pressure sensor after the elastic membrane is radially expanded or contracted through the monitoring system, and simultaneously measuring the new position of the earth surface under the assistance of the earth surface displacement measurement auxiliary reference to obtain the earth surface displacement value.
The technical scheme of the invention is that an expander is embedded in saturated soft clay contained in a model box, a plurality of soil pressure boxes and pore water pressure sensors are arranged at intervals on the plane of the cross section of an elastic membrane of the expander, wherein the elastic membrane of the expander partially or completely surrounds a support body to form a cylindrical or circular enclosed space and is provided with a hydraulic sensor for detecting the water pressure of the enclosed space, meanwhile, the expander is provided with a water injection pipe and a water outlet pipe communicated with the enclosed space to control the internal pressure of the enclosed space, the radial expansion of the elastic membrane can be realized by controlling the internal pressure of the enclosed space in the test process, so as to simulate the mechanical behavior of the expansion of small pores in the saturated soft clay, and meanwhile, the internal pressure change of the enclosed space before and after the expansion of the elastic membrane, the change of the pore pressure around the elastic membrane and the change of the radial stress are obtained through the data of the hydraulic sensor, the pore water pressure sensors and the soil pressure, and obtaining the displacement change condition of the top of the saturated soft clay before and after the expansion of the elastic membrane through the auxiliary measurement of the auxiliary reference of the surface displacement measurement, and finally analyzing and calculating the data such as pore pressure, radial stress, internal pressure, surface displacement and the like obtained by the test to obtain a constitutive model capable of accurately explaining the expansion of the small holes in the saturated soft clay in an auxiliary manner.
Drawings
FIG. 1 is a schematic view of the expansion of a spherical orifice;
FIG. 2 is a schematic view of the mating of a cylindrical expander with a mold box;
FIG. 3 is a distribution diagram of the soil pressure cell and pore water pressure sensor in the mold box during the cylindrical expansion test;
FIG. 4 is a schematic view of the mating of the ball expanders to the mold boxes;
FIG. 5 is a diagram of the distribution of the soil pressure cell and pore water pressure sensor within the mold box during a ball expansion test;
FIG. 6 is a schematic view of a seal structure;
FIG. 7 is a schematic view of a cylindrical dilator;
fig. 8 is a cross-sectional view of a ball dilator.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that if directional indications (such as … …, which is up, down, left, right, front, back, top, bottom, inner, outer, vertical, transverse, longitudinal, counterclockwise, clockwise, circumferential, radial, axial) are provided in the embodiments of the present invention, the directional indications are only used for explaining the relative position relationship, motion condition, etc. of the components at a specific posture (as shown in the attached drawings), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description relating to "first" or "second", etc. in the embodiments of the present invention, the description of "first" or "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides a small hole expansion test device.
In the embodiment of the invention, as shown in fig. 2 to 8, the small hole expansion test device comprises a model box 1, an expander, a plurality of soil pressure boxes 3, a plurality of pore water pressure sensors 4, a ground surface displacement measurement auxiliary reference 5 and a monitoring system (not shown).
Wherein, the model box 1 is filled with saturated soft clay (not shown), the dilator is embedded in the saturated soft clay, and comprises a rigid support body and elastic membranes 21-1 and 21-2, the elastic membranes 21-1 and 21-2 are preferably made of rubber, the elastic membranes 21-1 and 21-2 are connected with the support body directly or through an intermediate piece and surround the support body partially or completely to form columnar or spherical closed spaces 20-1 and 20-2, the support body or the elastic membranes 21-1 and 21-2 are connected with a water injection pipe 6 and a water outlet pipe 7 which are communicated with the closed spaces 20-1 and 20-2 and the outside, the water injection pipe 6 is communicated with a water supply device (not shown) which is positioned outside the model box 1, the water supply device can inject water into the closed spaces 20-1 and 20-2 according to needs, the water outlet pipe 7 extends to the outside of the model box 1 directly or through an intermediate connecting pipe, the water outlet pipe 7 is provided with a water outlet control valve 71, the closed spaces 20-1 and 20-2 are also internally provided with a hydraulic sensor 8 for detecting internal pressure, and when the internal pressure of the closed spaces 20-1 and 20-2 changes, the elastic membranes 21-1 and 21-2 can realize radial expansion to simulate the mechanical behavior of small hole expansion in saturated soft clay; a plurality of soil pressure cells 3 (generally, micro soil pressure cells 3) are embedded in the saturated soft clay and radially distributed at intervals on the plane where the cross sections of the elastic membranes 21-1 and 21-2 are located, and are used for detecting the change of radial stress around the elastic membranes 21-1 and 21-2 before and after the elastic membranes 21-1 and 21-2 are expanded; a plurality of pore water pressure sensors 4 (generally micro pore water pressure sensors 4) are embedded in the saturated soft clay, are radially distributed at intervals on the plane where the cross sections of the elastic membranes 21-1 and 21-2 are located, and are used for detecting the change of the pore pressure around the elastic membranes 21-1 and 21-2 before and after the elastic membranes 21-1 and 21-2 expand; the auxiliary reference 5 for measuring the surface displacement is arranged above the saturated soft clay in a region corresponding to the expander and is used for assisting in measuring the displacement change (namely equivalent to the surface displacement change) of the top of the saturated soft clay before and after the expansion of the elastic membranes 21-1 and 21-2; the monitoring system is used for acquiring data detected by the hydraulic sensor 8, the pore water pressure sensor 4 and the soil pressure box 3 before and after the elastic membranes 21-1 and 21-2 are expanded, the monitoring system is in the prior art and can be directly or indirectly connected with the hydraulic sensor 8, the pore water pressure sensor 4 and the soil pressure box 3, the specific connection mode and the working principle are in the prior art, and repeated description is omitted here. After the test is finished, the similarity ratio is considered, and the pore pressure, radial stress, internal pressure, surface displacement and other data obtained by the test are analyzed and calculated to obtain a constitutive model capable of accurately explaining the small pore expansion in the saturated soft clay in an auxiliary mode. For how to analyze and calculate specifically, details are not repeated here, for example, refer to the analysis and calculation method in the prior art.
In the embodiment of the present invention, the mold box 1 is preferably a square container with an opening at the top and a top cover 10, the overall size can be determined according to the test requirements, for example, the size can be 1.5m × 1.0m × 1.0.0 m, the left, right and bottom surfaces of the mold box 1 are formed by using angle steel as frameworks and then welding steel panels at the inner side, the front and rear sides of the mold box 1 are also formed by using angle steel as frameworks, and according to the test requirements, three schemes of adopting tempered glass panels inside the front and rear sides, or adopting a tempered glass panel only on the front side and welding a steel panel on the rear side, or adopting a tempered glass panel only on the front side.
In one embodiment of the present invention, as shown in fig. 2 and 7, the expander is a cylindrical expander 2-1 for performing an expansion simulation test of a cylindrical small hole, the support body of the cylindrical expander 2-1 comprises a rigid circular tubular inner tube 22 (preferably made of steel tube), the open two ends of the inner tube 22 are respectively connected with a first end cap 23 and a second end cap 24, the elastic membrane 21-1 is in a circular tubular shape, the open two ends of the elastic membrane 21-1 are respectively connected with the first end cap 23 and the second end cap 24, and the connection is sealed (for example, by disposing sealing rings 25 and 26) so that the elastic membrane 21-1 and the first end cap 23 and the second end cap 24 enclose the cylindrical closed space 20-1 for enclosing the inner tube 22 therein, the portion of the elastic membrane 21-1 between the first end cap 23 and the second end cap 24 is a radially expandable portion, the hydraulic sensor 8 is arranged on the outer wall of the inner pipe 22, a pressure measuring cable 81 of the hydraulic sensor 8 extends out of the closed space 20-1 from the first end cover 23, the matching position of the pressure measuring cable 81 and the first end cover 23 is sealed, and the first end cover 23 is further provided with a water inlet (not shown) and a water outlet (not shown) for installing the water injection pipe 6 and the water outlet pipe 7. Specifically, the water outlet pipe 7 partially extends into the gap between the inner pipe 22 and the elastic membrane 21-1, and the water injection pipe 6 extends into the inner pipe 22 and is communicated with the space where the gap between the inner pipe 22 and the elastic membrane 21-1 is located. More specifically, the end of the water injection pipe 6 located at the inner pipe 22 is connected to a hollow cavity 62, a circulation hole 621 is formed in the peripheral wall of the cavity 62, and water from the water injection pipe 6 flows into the cavity 62 and then flows through the circulation hole 621 to fill the closed space 20-1. The water injection pipe 6 can be provided with a water inlet control valve 61, when water is injected into the closed space 20-1, the water inlet control valve 61 needs to be opened, and when the water is stopped being injected into the closed space 20-1, the water inlet control valve 61 can be closed. After the water inlet control valve 61 is opened and the water outlet pipe 7 is closed, water is injected into the closed space 20-1, and the specified expansion pressure can be loaded according to the indication of the hydraulic sensor 8, so that the elastic membrane 21-1 is driven to realize radial expansion to simulate the expansion of the cylindrical small holes in the saturated soft clay. And the water outlet control valve 71 is opened, so that water slowly flows out of the closed space 20-1 through the water outlet pipe, and pressure reduction of shrinkage of the cylindrical small holes can be realized according to the indication of the hydraulic sensor 8, so that the elastic membrane 21-1 is radially shrunk to simulate shrinkage of the cylindrical small holes in the saturated soft clay.
Furthermore, positioning holes (not shown) are reserved in the middle of the front side surface and the middle of the rear side surface of the model box 1 respectively, and two ends (generally, the first end cap 23 and the second end cap 24) of the cylindrical expander 2-1 are erected in the two positioning holes and partially extend out of the model box 1, so that the cylindrical expander 2-1 is positioned during a simulation test, and meanwhile, the water injection pipe 6, the water outlet pipe 7 and the like are convenient to connect. It will be appreciated that the ends of the cylindrical expander 2-1 should be water-tightly sealed to the pilot hole, for example by a sealing arrangement 9.
Specifically, the sealing structure 9 includes a sealing ring 93 which can be partially clamped into the positioning hole and is in sealing contact with the peripheral wall of the end portion of the cylindrical expander 2-1 and the wall of the positioning hole, and a first clamping plate 91 and a second clamping plate 92, a semicircular clamping hole with a diameter slightly smaller than the outer diameter of the sealing ring 93 is formed in the position where the first clamping plate 91 and the second clamping plate 92 are opposite to each other, the first clamping plate 91 and the second clamping plate 92 are clamped on the sealing ring 93 through the semicircular clamping hole and then are fixedly connected through a fastening device, so that the portion, located outside the positioning hole, of the sealing ring 93 is tightly pressed and fastened on the end portion of the. Specifically, screw holes are respectively formed on two sides of the first clamping plate 91 and the second clamping plate 92, and the fastening device comprises at least two connecting strips 94, wherein two ends of each connecting strip 94 are respectively fixed at the corresponding screw holes of the first clamping plate 91 and the second clamping plate 92 through screws 95, so that the first clamping plate 91 and the second clamping plate 92 are tightly pressed on the sealing ring 93. It should be noted that the sealing structure 9 may also take other forms of structure, for example, according to the prior art. Preferably, the first clamping plate 91 and the second clamping plate 92 are made of hard rubber, and the first clamping plate 91 and the second clamping plate 92 are frosted on the side close to the model box 1 to prevent slipping and seepage.
In another embodiment of the present invention, as shown in fig. 4 and 8, the dilator is a spherical dilator 2-2 for performing a dilation simulation test of a spherical stoma, the support of the spherical dilator 2-2 includes a rigid hollow sphere 27, the hollow sphere 27 is preferably made of steel, the wall of the hollow sphere 27 is formed with a plurality of through holes 271, the through holes 271 are preferably uniformly distributed along the hollow sphere 27, the elastic membrane 21-2 is in a spherical shell shape and surrounds the hollow sphere 27 therein to form the spherical enclosed space 20-2, the hydraulic sensor 8 is arranged on the outer wall of the hollow sphere 27, the pressure measuring cable 81 of the hydraulic sensor 8 extends out of the enclosed space 20-2 from the spherical shell-shaped elastic membrane 21-2, the matching part of the pressure measuring cable 81 and the elastic membrane 21-2 is sealed, the hollow sphere 27 is provided with a water inlet, the water injection pipe 6 is arranged in the water inlet hole after extending into the elastic membrane 21-2, the matching part of the elastic membrane 21-2 and the water injection pipe 6 is sealed, and the elastic membrane 21-2 is also provided with the water outlet hole for installing the water outlet pipe 7. The water outlet pipe 7 partially extends into the elastic membrane 21-2 and is communicated with the space where the gap between the hollow sphere 27 and the elastic membrane 21-2 is positioned. After the water from the water injection pipe 6 flows into the hollow sphere 27, the closed space 20-2 is filled through the hole 271. When the water is filled into the closed space 20-2, the water inlet control valve 61 needs to be opened, and when the water is not filled into the closed space 20-2, the water inlet control valve 61 can be closed. After the water inlet control valve 61 is opened and the water outlet pipe 7 is closed, water is injected into the closed space 20-2, and the specified expansion pressure can be loaded according to the indication of the hydraulic sensor 8, so that the elastic membrane 21-2 is driven to realize radial expansion to simulate the expansion of spherical small holes in the saturated soft clay. And the water outlet control valve 71 is opened, so that water slowly flows out of the closed space 20-2 through the water outlet pipe, and pressure reduction can be realized according to the indication of the hydraulic sensor 8, so that the elastic membrane 21-2 is radially contracted to simulate the contraction of spherical small holes in the saturated soft clay. It should be noted that the spherical expander 2-2 and the cylindrical expander 2-1 can be used together with a mold box 1, and in the case of using the same mold box 1, the positioning hole should be sealed and closed when the spherical small hole expansion simulation test is performed.
In the present invention, the number of the soil pressure cells 3 may be set according to specific experimental requirements, for example, five soil pressure cells may be provided, for the simulation of cylindrical expansion, as shown in fig. 3, a cylindrical expander 2-1 is horizontally embedded in the saturated soft clay, the cross section of the cylindrical expander is parallel or approximately parallel to the vertical plane, the soil pressure cells 3 are radially and vertically spaced apart from the plane of the cross section of the elastic membrane 21-1, and the distances from the elastic membrane 21-1 are 0.5R, 1R, 2R, 3R, 4R, respectively, where R is the initial outer diameter of the elastic membrane 21-1 of the cylindrical expander 2-1, and for the spherical expander 2-2, since the water injection pipe 6 and the water outlet pipe 7 of the spherical shell-shaped elastic membrane 21-2 are in the gravity direction, the cross section of the spherical shell-shaped elastic membrane 21-2 is selected to be on the horizontal plane and pass through the center of the sphere, and the soil pressure cells 3 are radially and horizontally spaced from the elastic membrane 21-2, and the distances from the elastic membrane 21-2 are respectively, 0.5R, 1R, 2R, 3R, 2R, and the initial outer diameter of the type of the spherical expander 2-2 is preferably about 20 mm or about 8516 mm.
In the present invention, the number of pore water pressure sensors 4 may be set according to specific test requirements, for example, five sensors may be provided. Aiming at the cylindrical expansion simulation, the cylindrical expander 2-1 is horizontally embedded in the saturated soft clay, the cross section of the cylindrical expander is parallel to a vertical plane, the pore water pressure sensors 4 are distributed on the plane where the cross section of the elastic membrane 21-1 is located in a radial and horizontal mode at intervals, the distances from the elastic membrane 21-1 are 0.5R, 1R, 2R, 3R and 4R respectively, and R is the initial outer diameter of the elastic membrane 21-2 of the cylindrical expander 2-1. For the spherical expansion simulation, the water injection pipe 6 and the water outlet pipe 7 of the spherical expander 2-2 are in the gravity direction, so that the cross section of the spherical shell-shaped elastic membrane 21-2 is selected to be on the horizontal plane and pass through the center of the sphere, the pore water pressure sensors 4 are radially and horizontally distributed on the plane where the cross section of the elastic membrane 21-2 is located, are perpendicular to the distribution direction of the soil pressure cell, are respectively 0.5R, 1R, 2R, 3R and 4R away from the elastic membrane 21-2, and R is the initial outer diameter of the elastic membrane 21-2 of the spherical expander 2-2. The pore water pressure sensor 4 is preferably an AD-25 type micro pore water pressure sensor or an HC-25 type micro pore water pressure sensor, the diameter of the pore water pressure sensor is about 5mm, and the measuring range can cover-100 KPa to 100 KPa.
In the embodiment of the invention, for the measurement of the cylindrical expanded ground surface displacement, the auxiliary reference 5 for measuring the ground surface displacement is a reference line 51 which is arranged on the top cover 10 of the model box 1 and is positioned above the cross section of the elastic membrane 21-1 in the horizontal direction, and in the test process, the distance between the measurement point of the top soil body and the reference line 51 before and after the expansion can be measured by a ruler or other measuring means, so that the change of the ground surface displacement of the model before and after the cylindrical expansion and the distribution condition of the ground surface displacement before and after the expansion are determined. Specifically, before the test, a plurality of measurement points 52 are set on a cylindrical expanded ground surface (i.e., the top of the saturated soft clay), and displacements of the plurality of measurement points 52 before and after the simulation test are measured with reference to the reference line 51.
For the measurement of the ground surface displacement of the spherical expansion, two vertical and horizontal reference lines 51 can be arranged on the top cover 10 of the model box 1, a plurality of measuring points 52 are arranged on the expanded ground surface (namely the top of the saturated soft clay), the distance between the measuring points and the reference lines 51 before and after the expansion can be measured by a ruler or other measuring means, and the change of the ground surface displacement before and after the spherical expansion and the distribution of the ground surface displacement before and after the expansion in the vertical direction and the horizontal direction can be obtained.
It is understood that the diameters of the circular tubular elastic membrane 21-1 and the spherical shell-shaped elastic membrane 21-2 can be determined according to the experimental requirements, for example, 10cm is selected for each. In the design of the simulation test, it is difficult to satisfy all the conditions to satisfy the similarity relationship. Therefore, the main factors affecting the test results of the test are selected so as to satisfy the similarity relationship, and the test results are not so affected, and the similar conditions are allowed to be not satisfied when the similar conditions are difficult to satisfy. In the test, the soil material has the largest influence on the test, the expander is a device for actively applying pressure, and the test does not need to measure the displacement and the deformation of the expander, so whether the displacement and the deformation of the expander meet the similar relation or not is not considered, and whether the soil material (namely the saturated soft clay) meets the similar relation or not is only considered.
According to the test conditions, determining the geometric scale of the test soil body to be 1/M, namely the geometric similarity constant C1M. The similarity constant of the relevant physical quantities is denoted by C plus a subscript, wherein the geometric similarity constant C is1And volume weight similarity constant Cγ1 is the basis of the design. Based on the existing elastic mechanics method and the derivation of the existing similar first theorem, similar second theorem and similar third theorem, the design similarity constants of the relevant physical quantities are as follows:
table 1: design similarity constant of various related physical quantities
For test soil (namely saturated soft clay), the main mechanical parameters comprise compression modulus, cohesive force, internal friction angle, Poisson's ratio and the like, and the corresponding theoretical similarity constants are respectively CE=M,Cc=M,(due to internal friction angleBy tangent valueInfluence the shear strength, the internal friction angle of the prototype soil and the test soilIs kept consistent), Cμ1. The cohesive force and the internal friction angle mainly affect the strength of the soil body, when the test is considered in the elastic range, the cohesive force and the internal friction angle can not satisfy the similar relation, and the influence of the cohesive force and the friction angle still needs to be considered in the test. The poisson ratio of the soil body has certain influence on the pressure coefficient of the lateral soil, and when the test soil is simulated by adopting a real soil body or other similar granular materials, the poisson ratio of the actual soil body and the test soil approximately meets similar requirements. Therefore, the compressive modulus of the test soil needs to be considered with emphasis. According to the similar theory of the test, if the volume weight of the test soil is the same as that of the actual rock mass material, namely the volume weight scale is equal to 1.0, the elastic modulus scale and the stress scale are the same as the geometric scale. This will greatly simplify and facilitate the conversion between the model parameters and the actual engineering physical parameters.
Furthermore, the inner wall of the steel panel of the model box 1 can be coated with butter and a plastic film (such as a polytetrafluoroethylene plastic film) is adhered to reduce the boundary friction, thereby improving the test precision. The soil body is filled in layer by layer, and the boundary treatment is firstly carried out when one layer of soil is filled. Only the dead weight stress field is considered in the test. If the test soil body is a single-material soil body, when the condition of the stratum is not considered, the volume-weight scale positioning of the soil body material is 1: 1, the formation range is simulated to the surface, and then the initial stress field is automatically formed in proportion.
The saturated soft clay adopted in the simulation test generally refers to the cohesive soil which is in a soft plastic state and a flow plastic state and has large natural water content, high compressibility, low bearing capacity and very low shear strength. In the prior art, there are various methods for preparing saturated soft clay, for example, it can be prepared by remolding soil or other materials. Taking other substances as an example, when saturated soft clay is simulated, clean river sand, barite powder and vaseline are generally mixed, the proportion of each material is controlled by a single variable method, and then parameters are measured by a direct shear tester. For example, soft clay with a standard penetration N of not more than 5 is added with a certain proportion of a hot-melt mixture of barite powder, coarse quartz sand, fine quartz sand, vaseline, rosin and engine oil in materials mainly comprising river sand and fly ash by referring to engineering geological handbook and the like to determine the index range, and the proportion of each substance is obtained by repeated proportioning tests.
The invention also provides a small hole expansion test method based on the small hole expansion test device.
In an embodiment of the present invention, the small hole expansion test method includes the steps of:
s1, according to the test requirements, in the process of adding saturated soft clay layer by layer into a model box 1 and compacting, putting an expander, a plurality of pore water pressure sensors 4 and a plurality of soil pressure boxes 3 into the model box 1 so as to enable the expander, the plurality of pore water pressure sensors 4 and the plurality of soil pressure boxes 3 to be buried in the saturated soft clay in the model box 1, wherein closed spaces 20-1 and 20-2 are filled with water and maintain certain initial internal pressure;
specifically, a layering compaction method is used in the adding process of the saturated soft clay of the model box 1, the proper thickness is filled each time, then the soil body is evenly spread out and compacted, and the upper surface is napped after compaction, so that the close contact between filling layers is ensured; after the expander is placed, soil mass around the expander needs to be filled, and the soil mass around the expander needs to be compacted carefully, so that the expander 2 is prevented from being damaged, and the position of the expander is prevented from being changed; the pore water pressure sensor 4 and the soil pressure box 3 are timely tested after being buried, the soil on the upper layer is filled after the sensors survive, and careful treatment is carried out when the soil around and on the upper layer of the pore water pressure sensor 4 and the soil pressure box 3 is filled, so that the pore water pressure sensor 4 and the soil pressure box 3 are prevented from being disturbed or damaged; after the soil body is filled, the pore water pressure sensors 4 and the soil pressure boxes 3 need to be tested, all the pore water pressure sensors 4 and the soil pressure boxes 3 are guaranteed to be in a normal working state, and the sensors are calibrated.
S2, acquiring and recording initial internal pressure values detected by the pore water pressure sensors 4, the soil pressure boxes 3 and the hydraulic sensors 8 in the closed spaces 20-1 and 20-2 through a monitoring system;
in the present invention, the number of the soil pressure cells 3 may be set according to specific experimental requirements, for example, five soil pressure cells may be provided, for the simulation of cylindrical expansion, as shown in fig. 3, cylindrical expanders 2-1 are horizontally embedded in the saturated soft clay, the cross sections of which are parallel or approximately parallel to the vertical plane, the soil pressure cells 3 are radially and vertically spaced apart from the plane of the cross section of the elastic membrane 21-1 by a distance of 0.5R, 1R, 2R, 3R, 4R, respectively, with respect to the elastic membrane 21-1, and R is the initial outer diameter of the elastic membrane 21 of the cylindrical expander 2-1, whereas for the spherical expanders 2-2, the cross sections of the spherical shell-shaped elastic membrane 21-2 are selected on the horizontal plane and pass through the spherical center, the soil pressure cells 3 are radially and horizontally spaced from the elastic membrane 21-2 by a distance of 0.5R, 1R, 2R, 3R, 4R, the initial outer diameter of the spherical pressure cells 21-2 is about 350 mm, or about 83 mm, respectively, of the pressure cells of the type AD 21-2.
In the present invention, the number of pore water pressure sensors 4 may be set according to specific test requirements, for example, five sensors may be provided. Aiming at the cylindrical expansion simulation, the cylindrical expander 2-1 is horizontally embedded in the saturated soft clay, the cross section of the cylindrical expander is parallel to a vertical plane, the pore water pressure sensors 4 are distributed on the plane where the cross section of the elastic membrane 21-1 is located in a radial and horizontal mode at intervals, the distances from the elastic membrane 21-1 are 0.5R, 1R, 2R, 3R and 4R respectively, and R is the initial outer diameter of the elastic membrane 21-1 of the cylindrical expander 2-1. For the spherical expansion simulation, because the water injection pipe 6 and the water outlet pipe 7 of the spherical expander 2-2 are in the gravity direction, the cross section of the spherical shell-shaped elastic membrane 21-2 is selected to be on the horizontal plane and pass through the center of the sphere, the pore water pressure sensors 4 are radially and horizontally distributed on the plane of the cross section of the elastic membrane 21-2, the distances from the elastic membrane 21-2 are respectively 0.5R, 1R, 2R, 3R and 4R, and R is the initial outer diameter of the elastic membrane 21-2 of the spherical expander 2-2. The pore water pressure sensor 4 is preferably an AD-25 type micro pore water pressure sensor or an HC-25 type micro pore water pressure sensor, the diameter of the pore water pressure sensor is about 5mm, and the measuring range can cover-100 KPa to 100 KPa.
S3, a surface displacement measurement auxiliary reference 5 is arranged above the saturated soft clay corresponding to the area of the dilator, and the initial position of the surface is measured.
Specifically, for the measurement of the cylindrical expanded ground surface displacement, the ground surface displacement measurement auxiliary reference 5 is a reference line 51 arranged in the horizontal direction of the top cover 10 of the model box 1 above the cross section of the elastic membrane 21-2, and in the test process, the distance between the top soil body measurement point and the reference line 51 before and after the expansion can be measured by a ruler or other measurement means, so that the change of the ground surface displacement of the model before and after the cylindrical expansion and the ground surface displacement distribution before and after the expansion are determined. Specifically, before the test, a plurality of measurement points 52 are provided on the surface of the cylindrical dilator 2-1 (i.e., on top of the saturated soft clay), and the surface displacements of the plurality of measurement points 52 before and after the simulation test are measured with reference to the reference line 51.
For the measurement of the ground surface displacement of the spherical expansion, two vertical and horizontal reference lines 51 can be arranged on the top cover 10 of the model box 1, a plurality of measuring points 52 are arranged on the expanded ground surface (namely the top of the saturated soft clay), the distance between the measuring points and the reference lines 51 before and after the expansion can be measured by a ruler or other measuring means, and the change of the ground surface displacement before and after the spherical expansion and the distribution of the ground surface displacement before and after the expansion in the vertical direction and the horizontal direction can be obtained.
S4, increasing or decreasing the water quantity in the closed spaces 20-1, 20-2 through the cooperation of the water outlet control valve 71 and the water supply device until the internal pressure of the closed spaces 20-1, 20-2 increases or decreases to a preset value, so as to radially expand or contract the elastic membranes 21-1, 21-2 and drive the saturated soft clay around the elastic membranes 21-1, 21-2 to generate deformation.
And S5, acquiring new values detected by the pore water pressure sensors 4, the soil pressure boxes 3 and the hydraulic pressure sensors 8 after the elastic membranes 21-1 and 21-2 are radially expanded or contracted through the monitoring system, and simultaneously measuring the new position of the earth surface under the assistance of the earth surface displacement measurement auxiliary reference 5 to obtain the earth surface displacement value.
Example 1:
the process of the invention for carrying out the cylindrical small hole expansion simulation test comprises the following steps:
1) filling the lower soil (saturated soft clay) into the model box 1 as required, inserting the second end cover 24 of the cylindrical expander 2-1 into one positioning hole, and then clamping the first end cover 23 into the other positioning hole of the model box 1 to keep the cylindrical expander 2-1 horizontally stable and sealed;
2) opening the water inlet control valve 61, simultaneously opening the water outlet control valve 71, filling water into the elastic membrane 21-1 of the cylindrical expander 2-1 until the elastic membrane 21-1 keeps the surface flush (the outer diameter of the elastic membrane 21-1 in this state is the initial outer diameter), discharging the gas in the enclosed space 20-1 from the water outlet pipe 7, closing the water inlet control valve 61, stopping water injection, checking whether the enclosed space 20-1 leaks water, if the water does not leak, closing the water outlet control valve 71, and opening the water inlet control valve 61 to inject water into the enclosed space 20-1 until the enclosed space 20-1 keeps a certain initial internal pressure;
3) arranging a soil pressure box 3 and a pore water pressure sensor 4 on the soil around the cylindrical expander 2-1, reading and recording initial display values of the soil pressure box 3, the pore water pressure sensor 4 and the hydraulic sensor 8, completing subsequent soil filling, and keeping the internal pressure measured by the hydraulic sensor 8 in the closed space 20-1 basically unchanged;
4) after the soil is filled, the top cover 10 of the model box 1 is covered, and the initial position of the earth surface is measured by combining the reference line 51;
5) and opening the water inlet control valve 61, increasing the internal pressure of the closed space 20-1 to a preset value by injecting water, closing the water inlet control valve 61 to increase the radius of the elastic membrane 21-1 so as to deform the soil around the elastic membrane, reading new values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, and measuring the displacement value of the earth surface.
Example 2:
the process of the invention for carrying out the cylindrical small hole shrinkage simulation test comprises the following steps:
(1) after filling the lower soil (saturated soft clay) into the model box 1 as required, inserting the second end cover 24 of the cylindrical expander 2-1 into one positioning hole, and then clamping the first end cover 23 into the other positioning hole of the model box 1 to keep the cylindrical expander 2-1 horizontally stable and sealed;
(2) opening the water inlet control valve 61, simultaneously opening the water outlet control valve 71, filling water into the elastic membrane 21-1 of the cylindrical expander 2-1 until the elastic membrane 21-1 keeps the surface level, discharging the gas in the closed space 20-1 from the water outlet pipe 7, closing the water inlet control valve 61, stopping water injection, checking whether the closed space 20-1 leaks water, if the water does not leak, closing the water outlet control valve 71, opening the water inlet control valve 61, filling water into the closed space 20-1 until the closed space 20-1 keeps a certain initial internal pressure
(3) Arranging a soil pressure box 3 and a pore water pressure sensor 4 on the soil around the cylindrical expander 2-1, reading and recording initial display values of the water pressure sensor, the soil pressure box 3 and the pore water pressure sensor 4, completing subsequent soil filling, and keeping the pressure measured by a hydraulic sensor 8 in the closed space 20-1 basically unchanged;
(4) after the soil is filled, the top cover 10 of the model box 1 is covered, and the initial position of the earth surface is measured by combining the reference line 51;
(5) and opening the water outlet control valve 71, reducing the internal pressure of the closed space 20-1 to a preset value through drainage, closing the water outlet control valve 71 to reduce the radius of the elastic membrane 21-1 so as to deform the soil around the elastic membrane, reading new values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, and measuring the displacement value of the earth surface.
Example 3:
the process of the invention for carrying out the spherical small hole expansion simulation test comprises the following steps:
A. after the lower layer of soil (saturated soft clay) is filled in the model box 1 as required, a small groove is reserved for the spherical expander 2-2, the spherical expander 2-2 is placed in the small groove, the spherical expander 2-2 is kept horizontally placed, and the water injection pipe 6 is upward;
B. opening a water inlet control valve 61 of the spherical expander 2-2, simultaneously opening a water outlet control valve 71, filling water in a rubber film of the spherical expander 2-2 until the elastic rubber film keeps close to a perfect circle, discharging the gas in the closed space 20-2 from a water outlet pipe 7, closing the water inlet control valve 61, checking whether water is leaked, and if the water is not leaked, opening the water inlet control valve 61 and continuously filling water into the closed space 20-2 for pressurization until the interior of the spherical expander 2-2 keeps a certain initial internal pressure after closing the water outlet control valve 71;
C. soil around the spherical expander 2-2 is filled and compacted to ensure that the spherical expander 2-2 is kept stably placed;
D. filling soil around the spherical expander 2-2, arranging the soil pressure box 3 and the pore water pressure sensor 4, reading and recording initial display numerical values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, completing subsequent soil filling, and keeping the internal pressure measured by the hydraulic sensor 8 in the closed space 20-2 basically unchanged;
E. after the soil is filled, covering a top cover 10 of the model box 1 and measuring the initial position of the earth surface;
F. and opening the water inlet control valve 61, increasing the internal pressure of the closed space 20-2 to a preset value through water injection, closing the water inlet control valve 61 to increase the radius of the spherical shell-shaped elastic membrane 21-2 so as to deform the soil body around the spherical shell-shaped elastic membrane, reading new values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, and measuring the displacement value of the ground surface.
Example 4:
the process of the invention for carrying out the spherical small hole shrinkage simulation test comprises the following steps:
a. after the lower layer of soil (saturated soft clay) is filled in the model box 1 as required, a small groove is reserved for the spherical expander 2-2, the spherical expander 2-2 is placed in the small groove, the spherical expander 2-2 is kept horizontally placed, and the water injection pipe 6 is upward;
b. opening a water inlet control valve 61 of the spherical expander 2-2, simultaneously opening a water outlet control valve 71, filling water in a rubber film of the spherical expander 2-2 until the elastic rubber film keeps close to a perfect circle, and after the gas in the closed space 20-2 is exhausted from a water outlet pipe 7, closing the water inlet control valve 61, checking whether water is leaked, if no water is leaked, after closing the water outlet control valve 71, opening the water inlet control valve 61 and continuously pressurizing the closed space 20-2 until the interior of the spherical expander 2-2 keeps a certain initial internal pressure;
c. soil around the spherical expander 2-2 is filled and compacted to ensure that the spherical expander 2-2 is kept stably placed;
d. filling soil around the spherical expander 2-2, arranging the soil pressure box 3 and the pore water pressure sensor 4, reading and recording initial display numerical values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, completing subsequent soil filling, and keeping the internal pressure measured by the hydraulic sensor 8 in the closed space 20-2 basically unchanged;
e. after the soil is filled, covering a top cover 10 of the model box 1 and measuring the initial position of the earth surface;
f. and opening the water outlet control valve 71, reducing the internal pressure of the closed space 20-2 to a preset value through drainage, closing the water inlet control valve 61, increasing the radius of the spherical shell-shaped elastic membrane 21-2, deforming the soil body around the spherical shell-shaped elastic membrane, reading the numerical values of the hydraulic sensor 8, the soil pressure box 3 and the pore water pressure sensor 4, and measuring the displacement value of the ground surface.
After the test is finished, the similarity ratio is considered, and the pore pressure, the radial stress, the internal pressure, the earth surface displacement and other data obtained by the test are analyzed and calculated to obtain an constitutive model capable of accurately explaining the small hole expansion in the saturated soft clay in an auxiliary mode. For how to analyze and calculate specifically, details are not repeated here, for example, refer to the analysis and calculation method in the prior art.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (4)

1. An aperture expansion test device, comprising:
the model box is filled with saturated soft clay;
the expander is embedded in the saturated soft clay and comprises a rigid support body and an elastic membrane, the elastic membrane is directly connected with the support body or connected with the support body through an intermediate piece to surround part or all of the support body to form a spherical closed space, the support body or the elastic membrane is connected with a water injection pipe and a water outlet pipe which are communicated with the closed space and the outside, the water injection pipe is communicated with a water supply device positioned outside the model box, the water outlet pipe extends to the outside of the model box directly or through an intermediate connecting pipe, the water outlet pipe is provided with a water outlet control valve, a hydraulic sensor for detecting the internal pressure is also arranged in the closed space, and when the internal pressure of the closed space changes, the elastic membrane can realize radial expansion;
the soil pressure boxes are embedded in the saturated soft clay, are distributed at intervals in the radial direction of the plane where the cross section of the elastic membrane is located, and are used for detecting the change of radial stress around the elastic membrane before and after the elastic membrane is expanded;
the pore water pressure sensors are embedded in the saturated soft clay, radially distributed on the plane where the cross section of the elastic membrane is located at intervals and used for detecting the change of the pore pressure around the elastic membrane before and after the elastic membrane expands;
the auxiliary reference for measuring the surface displacement is arranged in a region above the saturated soft clay corresponding to the expander and is used for assisting in measuring the displacement change of the top of the saturated soft clay before and after the expansion of the elastic membrane; and
the monitoring system is used for acquiring detected data of the hydraulic sensor, the pore water pressure sensor and the soil pressure cell before and after the elastic membrane is expanded;
the expander is a spherical expander, a supporting body of the spherical expander comprises a rigid hollow sphere, a plurality of through holes are formed in the wall of the hollow sphere, the elastic membrane is in a spherical shell shape and surrounds the hollow sphere to form the spherical closed space, the hydraulic sensor is arranged on the outer wall of the hollow sphere, a pressure measuring cable of the hydraulic sensor extends out of the closed space from the spherical shell-shaped elastic membrane, the matching position of the pressure measuring cable and the elastic membrane is sealed, a water inlet hole is formed in the hollow sphere, the water injection pipe extends into the elastic membrane and then is installed in the water inlet hole, the matching position of the elastic membrane and the water injection pipe is sealed, the elastic membrane is further provided with the water outlet hole for installing a water outlet pipe, and the water outlet pipe partially extends into the elastic membrane and is communicated with the space where the gap between the hollow sphere and the elastic membrane is located.
2. The small hole expansion test device of claim 1, wherein: the cross section of the spherical shell-shaped elastic membrane is selected on a horizontal plane and penetrates through the center of a sphere, the water injection pipe and the water outlet pipe are arranged in the gravity direction, the soil pressure boxes are radially and horizontally distributed on the plane of the cross section of the elastic membrane, the pore water pressure sensors are radially and horizontally distributed on the plane of the cross section of the elastic membrane and are vertical to the distribution direction of the soil pressure boxes, the number of the pore water pressure sensors and the number of the soil pressure boxes are five, the distances between the pore water pressure sensors and the soil pressure boxes and the elastic membrane are respectively 0.5R, 1R, 2R, 3R and 4R, and R is the initial outer diameter of the elastic membrane of the spherical expander.
3. A method of testing the small hole expansion test device of claim 1 or 2, comprising the steps of:
s1, according to the test requirements, in the process of adding saturated soft clay into a model box in a layered mode and compacting, placing an expander, a plurality of pore water pressure sensors and a plurality of soil pressure boxes into the model box so that the expander, the plurality of pore water pressure sensors and the plurality of soil pressure boxes are buried in the saturated soft clay in the model box, wherein a closed space is filled with water and certain initial internal pressure is kept;
s2, acquiring and recording initial internal pressure values detected by the pore water pressure sensors, the soil pressure boxes and the hydraulic sensors in the closed space through a monitoring system;
s3, arranging an auxiliary reference for measuring the displacement of the earth surface above the saturated soft clay corresponding to the area of the dilator, and measuring the initial position of the earth surface;
s4, increasing or decreasing the water quantity in the closed space through the cooperation of the water outlet control valve and the water supply device until the internal pressure of the closed space is increased or decreased to a preset value, so that the elastic membrane radially expands or contracts and drives the saturated soft clay around the elastic membrane to deform;
and S5, acquiring new values detected by the plurality of pore water pressure sensors, the plurality of soil pressure boxes and the hydraulic pressure sensor after the elastic membrane is radially expanded or contracted through the monitoring system, and simultaneously measuring the new position of the earth surface under the assistance of the earth surface displacement measurement auxiliary reference to obtain the earth surface displacement value.
4. The method of testing a small hole expansion test device of claim 3, wherein: in step S1, after the pore water pressure sensor and the soil pressure cell are buried and the soil is filled, the method further includes testing the pore water pressure sensor and the soil pressure cell respectively to ensure the survival of the sensors.
CN202010227635.0A 2019-06-20 2019-06-20 Small hole expansion test device and method Pending CN111413485A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN202010227635.0A CN111413485A (en) 2019-06-20 2019-06-20 Small hole expansion test device and method
CN201910535486.1A CN110208493B (en) 2019-06-20 2019-06-20 Small hole expansion test device and test method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010227635.0A CN111413485A (en) 2019-06-20 2019-06-20 Small hole expansion test device and method

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
CN201910535486.1A Division CN110208493B (en) 2019-06-20 2019-06-20 Small hole expansion test device and test method thereof

Publications (1)

Publication Number Publication Date
CN111413485A true CN111413485A (en) 2020-07-14

Family

ID=67793758

Family Applications (2)

Application Number Title Priority Date Filing Date
CN202010227635.0A Pending CN111413485A (en) 2019-06-20 2019-06-20 Small hole expansion test device and method
CN201910535486.1A Active CN110208493B (en) 2019-06-20 2019-06-20 Small hole expansion test device and test method thereof

Family Applications After (1)

Application Number Title Priority Date Filing Date
CN201910535486.1A Active CN110208493B (en) 2019-06-20 2019-06-20 Small hole expansion test device and test method thereof

Country Status (1)

Country Link
CN (2) CN111413485A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113063713A (en) * 2021-03-23 2021-07-02 西南石油大学 Method for testing non-uniform pressure distribution on seepage section of large-diameter long core

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112345729B (en) * 2020-10-28 2021-10-29 中国地质大学(武汉) Device for indoor soil body cavity expansion experiment
CN112965378B (en) * 2021-02-05 2022-02-11 中山大学 High-speed railway foundation deformation self-adaptive control system and method

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060088388A1 (en) * 2004-10-27 2006-04-27 Wissmann Kord J Method and apparatus for providing a rammed aggregate pier
CN101545841A (en) * 2008-03-25 2009-09-30 四川升拓检测技术有限责任公司 Method and device for falling-sphere spot testing of mechanics characteristics of rock and soil materials
CN103995097A (en) * 2014-06-06 2014-08-20 中国科学院武汉岩土力学研究所 Test method and test device for simulating stratum deformation caused by pipe jacking construction
CN203881760U (en) * 2014-06-06 2014-10-15 中国科学院武汉岩土力学研究所 Test device for simulating stratum loss caused by pipe-jacking construction
CN105116101A (en) * 2015-06-09 2015-12-02 山东科技大学 Simulation test system for prevention and control of mine disasters and application method thereof
CN206497110U (en) * 2016-12-26 2017-09-15 暨南大学 A kind of flexible lateral spacing consolidation device for being used to determine weak soil compression property
CN107328370A (en) * 2017-06-23 2017-11-07 中国科学院武汉岩土力学研究所 The fiber grating aperture deformation-sensor of long-term measurement surrouding rock stress

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109596814A (en) * 2019-01-10 2019-04-09 中山大学 The layer of sand three-dimensional grouting test device and its test method of analog actual condition

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060088388A1 (en) * 2004-10-27 2006-04-27 Wissmann Kord J Method and apparatus for providing a rammed aggregate pier
CN101545841A (en) * 2008-03-25 2009-09-30 四川升拓检测技术有限责任公司 Method and device for falling-sphere spot testing of mechanics characteristics of rock and soil materials
CN103995097A (en) * 2014-06-06 2014-08-20 中国科学院武汉岩土力学研究所 Test method and test device for simulating stratum deformation caused by pipe jacking construction
CN203881760U (en) * 2014-06-06 2014-10-15 中国科学院武汉岩土力学研究所 Test device for simulating stratum loss caused by pipe-jacking construction
CN105116101A (en) * 2015-06-09 2015-12-02 山东科技大学 Simulation test system for prevention and control of mine disasters and application method thereof
CN206497110U (en) * 2016-12-26 2017-09-15 暨南大学 A kind of flexible lateral spacing consolidation device for being used to determine weak soil compression property
CN107328370A (en) * 2017-06-23 2017-11-07 中国科学院武汉岩土力学研究所 The fiber grating aperture deformation-sensor of long-term measurement surrouding rock stress

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
HANLONG LIU 等: "《High pressure jet-grouting column installation effect in soft soil:Theoretical model and field application》", 《COMPUTERS AND GEOTECHNICS》 *
JIDONG ZHAO 等: "《Unloading and reverse yielding of a finite cavity in a bounded cohesive–frictional medium》", 《COMPUTERS AND GEOTECHNICS》 *
孙更生 郑大同 主编: "《软土地基与地下工程》", 30 September 1984 *
王树元 主编: "《大地与建筑物变形测量》", 30 October 1994 *
陈湘桂 等: "《连续基坑群开挖的影响效应研究》", 《铁道科学与工程学报》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113063713A (en) * 2021-03-23 2021-07-02 西南石油大学 Method for testing non-uniform pressure distribution on seepage section of large-diameter long core
CN113063713B (en) * 2021-03-23 2022-04-05 西南石油大学 Method for testing non-uniform pressure distribution on seepage section of large-diameter long core

Also Published As

Publication number Publication date
CN110208493A (en) 2019-09-06
CN110208493B (en) 2020-04-28

Similar Documents

Publication Publication Date Title
CN110208493B (en) Small hole expansion test device and test method thereof
Lade Triaxial testing of soils
US10060898B2 (en) Expandable jacket for triaxial, unconfined and uniaxial compression tests and test device for three-dimensional consolidation and settlement tests
CN105334142B (en) A kind of experimental provision formed for simulating shield mud film
CN102590468B (en) Testing system for deep soil freezing/thawing process
US9880081B1 (en) Expandable jacket for triaxial, unconfined and uniaxial compression tests and test device for three-dimensional consolidation and settlement tests
CN106018740A (en) Piezocone penetration test calibration tank system
CN103105310A (en) Testing device and method of ground deformation caused by simulating metro shield tunnel construction
CN104074210B (en) Pile foundation side friction shop experiment device and test method thereof
Liu et al. Experimental research on water retention and gas permeability of compacted bentonite/sand mixtures
WO2019232983A1 (en) Pile-soil contact surface shear mechanical property testing equipment
CN106198890A (en) A kind of indoor grouting simulation test device and using method thereof
CN109297880A (en) Buried hydraulic tunnel osmotic gradient simulation experiment system and test method
CN205262912U (en) Experimental device for it constructs sludge -biofilm formation to be used for simulating shield
CN106404567A (en) Pile-soil simulating device and method under wave load
Estabragh et al. Consolidation behavior of an unsaturated silty soil during drying and wetting
Zakaria Yielding of unsaturated soil.
Al-Shamrani et al. Swelling behavior under oedometric and triaxial loading conditions
Tan Pressuremeter and cone penetrometer testing in a calibration chamber with unsaturated Minco silt
CN106644733A (en) Testing equipment for simulating response on embedded type pile-seabed by one-dimensional wave load
US11092588B2 (en) Measurement cell and associated measurement method
CN208586595U (en) A kind of soil lateral pressure monitoring device
CN107560570B (en) A kind of high methane cherry coal drilling produces the test method of the quantity of slag and drilling deformation
CN109974593A (en) A kind of experimental rig and test method for simulating soil body cavity expansion
CN208270333U (en) Measure any depth soil layer side friction device

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
RJ01 Rejection of invention patent application after publication
RJ01 Rejection of invention patent application after publication

Application publication date: 20200714