CN108560616B - Simulation method for excavation process of single-support structure foundation pit - Google Patents

Simulation method for excavation process of single-support structure foundation pit Download PDF

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CN108560616B
CN108560616B CN201810401766.9A CN201810401766A CN108560616B CN 108560616 B CN108560616 B CN 108560616B CN 201810401766 A CN201810401766 A CN 201810401766A CN 108560616 B CN108560616 B CN 108560616B
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pile
pressure
simulation
positioning
cross beam
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CN108560616A (en
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李建军
常慧
裴勇
连勇
徐鹏程
李剑锋
韩云山
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North University of China
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North University of China
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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

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Abstract

The invention discloses a simulation method for the excavation process of a single-support type structure foundation pit, which has the advantages of reasonable design, flexible use and low cost; firstly, applying the initial soil pressure of the pile side of the support pile according to the set side static soil pressure form, and then applying a loading device a on the topmost layer of one side of the simulation device1Loading ofThe handle rotates, and the number b of sets of symmetrical loading devices arranged on the right side of the model pile1Continuously acting on the simulation pile, and sequentially unloading all the loading devices a above the single-support loading position according to the simulation working conditioniAfter the forces on the two sides of the simulation pile are balanced, the unloaded right pressing component corresponding to the single-support loading position is loaded on the supporting pile again according to the size of the internal supporting force loaded as required, single-support loading simulation is realized, and finally the pressing components on the right side of the lower part of the single support are sequentially unloaded according to a preset working condition until soil body unloading in all ranges of the excavation side of the foundation pit is completed, so that dynamic simulation of changes of soil pressure inside and outside the pile side of the single-support supporting structure is realized.

Description

Simulation method for excavation process of single-support structure foundation pit
Technical Field
The invention discloses a simulation method for a single-support structure foundation pit excavation process, and belongs to the technical field of civil engineering design and construction.
Background
In the continuous development process of modern cities, buildings tend to be densified, high-rise buildings and underground facilities are increased, and the problems of deep foundation pit excavation and stability exist in the construction of a lower structure of the high-rise buildings in a building dense area. Because the calculation of supporting engineering is more complicated along with the change of soil layers, a plurality of soil layers are often simplified in the design process, the deep foundation pit construction and supporting are usually based on experience and engineering analogy methods, and particularly, the optimization of the supporting scheme and the optimization research of the supporting member are not deep systems.
In fact, in the calculation of the internal force of the single-support type structure of the foundation pit, firstly, a calculation simplified model of the supporting structure, an assumption of the soil pressure outside the supporting structure and a change of the soil pressure in the excavation process of the foundation pit need to be determined, when the existing technical regulation for supporting the foundation pit of the building (JGJ120) calculates the single-support or anchor-pull type supporting structure, the soil pressure outside the supporting pile is regarded as active soil pressure, the soil counter-force inside the foundation pit is adopted as a linear elastic model, the supporting pile is calculated by looking at an elastic beam, and the dynamic change of the soil pressure is not considered in the calculation. How to adopt a physical model to intuitively and visually express the calculation process and reasonably consider the change of the soil pressure in the excavation process of the foundation pit with the single-support structure is a problem which needs to be faced by civil engineering teaching and engineering calculation.
Disclosure of Invention
Aiming at the problem of the existing single-support structure foundation pit supporting pile, the invention discloses a simulation method for the excavation process of a single-support structure foundation pit, which has the advantages of reasonable design, flexible use and low cost, and aims to realize better theoretical analysis and simulation teaching and complete reasonable support design and optimal economic benefit.
In order to solve the technical problems, the invention adopts the technical scheme that: a simulation method for the excavation process of a foundation pit with a single-support structure is implemented according to the following steps:
the first step is as follows: installing a counterforce frame;
fixing the counterforce frame on the ground to ensure that the bottom cross beams are horizontally arranged and the side beams are vertically arranged;
the second step is that: determining parameters of the model pile;
determining the pile length of the model pile, wherein the pile length is the pile top reserved length + the calculated pile length + the pile end reserved length, the calculated pile length is the length determined by the distance between the pile top and the pile end of the support pile according to the proportion, and the width of the pile for applying a lateral soil pressure surface, the shape of a pile length lateral soil pressure curve and the shape of static soil pressure along the edge before the excavation of a pile lateral soil layer are used;
the third step: installing a positioning adjusting assembly;
the supporting plate is arranged between the top cross beam and the bottom cross beam, the upper end and the lower end of the supporting plate are fixed in the grooves, and the vertical axis of the supporting plate is enabled to be coincident with the plumb line; an adjusting rod is arranged in an insertion hole in the notch of each cross beam, the adjusting rod penetrates through an adjusting nut, the upper end of the adjusting rod is fixed on the positioning cross beam, and all the positioning cross beams at the same height are positioned on the same horizontal plane by rotating the adjusting nut;
the fourth step: installing a pressure applying assembly and a pressure transmitting assembly on the side of the model pile;
the pressing assembly is processed in advance, two ends of the sleeve penetrate through the side beams of the counter-force frame, a spring is arranged outside the positioning rod, one end of the positioning rod is sequentially connected with the piston and the dowel bar, the dowel bar penetrates through the limiting plate and is inserted into the U-shaped groove of the connecting plate, contacts with the bottom plane of the U-shaped groove and is fixed with the connecting plate through a connecting pin, the other end of the positioning rod is inserted into the hollow threaded rod, the hollow threaded rod is connected with the sleeve through a screw thread, and a loading handle is additionally arranged at the outer end; mounting a pressure sensor at a reserved position of the geometric center of a bearing plate of a pressure transmission assembly, wherein the surface of the pressure sensor facing the model pile is flush with the surface of the bearing plate, mounting a cushion block on the surface of one side of the bearing plate facing the model pile, and connecting each pressure transmission assembly to a corresponding positioning beam through a positioning plate;
the fifth step: manufacturing and installing a model pile;
filling a proper amount of filling soil into a bottom hole of the counter-force frame, compacting according to a set compactness, then hoisting a prefabricated model pile into the counter-force frame through a pile feeding hole reserved in a top cross beam, inserting the bottom end of the model pile into the bottom hole, determining the depth of the model pile inserted into the bottom hole according to the embedding condition of the model pile, adjusting the verticality of the model pile to enable the longitudinal axis of the model pile to coincide with a plumb line, and filling and compacting a gap between the bottom hole and the model pile by using the filling soil;
and a sixth step: adjusting the loading direction of the model pile side pressing assembly and loading;
ensuring that the normals of the bearing plates symmetrically distributed on the two sides of the model pile are on the same horizontal straight line, determining the eccentricity of the two bearing plates symmetrically arranged on the left and right sides of each set of pressure transmission assembly by determining the height deviation between the horizontal axes of the two bearing plates symmetrically arranged on the left and right sides of each set of pressure transmission assembly and the horizontal axis of the force transmission rod according to the distribution form of the lateral soil pressure of the pile, then adjusting the vertical position of the end part of the force transmission rod in a U-shaped groove to ensure that the axes of the two symmetrical force transmission rods are superposed, fixing the force transmission rod on a connecting plate by a connecting pin penetrating through a positioning hole and a connecting through hole of the force transmission rod, ensuring reliable connection, thus completing the horizontal adjustment of the set of pile lateral pressure application assembly and the pressure transmission assembly, and repeating the steps until the adjustment of the pile lateral pressure application assembly and the pressure; rotating a loading handle of the pressure applying assembly to apply initial soil pressure to the pile side of the model pile according to the calculated pile length pile side soil pressure distribution form determined in the second step;
the seventh step: excavating a first layer of soil body according to the actual working conditions of excavation of the foundation pit, namely, a loading device a of the topmost layer on one side in the simulation device1The loading handle rotates to make the dowel bar of the loading device move to the outer side of the side beam, and then the dowel plate of the pressure transmission assembly is dragged to be separated from the simulation pile, so that the counter force F originally acting on the simulation pile10, is equivalent to the first layer soil layer is excavated, because original symmetrical atress balanced state is destroyed, arranges the cover number b of symmetrical loading device on model stake right side1Continuously acting on the simulation pile, namely acting on the support pile under the action of the active soil pressure of the soil body outside the foundation pit, and bending and deforming the top of the simulation pile leftwards, and then acting on the loading device b at the right side1The middle spring extends, static soil pressure is converted into active soil pressure, and other parts along the length of the simulation pile can generate corresponding bending deformation until finally reaching the force balance state again, so that the first-step excavation simulation of the foundation pit is realized;
eighthly, recording readings of the displacement sensors and readings of the pressure sensors on two sides along the length range of the pile, and processing the data to obtain horizontal soil pressure and horizontal displacement of different sections of the pile body of the excavation working condition support pile;
the ninth step: in the seventh step, the loading device a is rotated2The loading handle makes the dowel bar of the loading device move to the outer side of the side beam, and then pulls the dowel plate of the pressure transmission assembly to separate from the simulation pile, so that the counter force F originally acting on the simulation pile2Simultaneously recording the readings of the displacement sensors and the readings of the pressure sensors along the two sides of the pile length range to realize the second-step excavation simulation of the foundation pit;
the tenth step: rotary loading device a2Loading handle ofThe force transmission rod of the loading device moves towards the simulation pile, then pushes the force transmission plate of the pressure transmission component to contact the simulation pile, and continuously rotates the loading device a2The loading handle of (2) to make the counter force F acting on the simulation pile2＝F2＇，F2' acting force of the anchor rod on the simulation pile is recorded, and the readings of the displacement sensors and the readings of the pressure sensors on two sides along the length range of the pile are recorded simultaneously, so that the simulation of the single-layer anchor rod support of the foundation pit is realized;
the eleventh step: in the seventh step, the loading device a is rotated in sequence3And a4The loading handle makes the dowel bar of the loading device move to the outer side of the side beam, and then pulls the dowel plate of the pressure transmission assembly to separate from the simulation pile, so that the counter force F originally acting on the simulation pile3Simultaneously recording the readings of the displacement sensors and the readings of the pressure sensors along the two sides of the pile length range when the number is 0, and realizing excavation simulation of the fourth step and the fifth step of the foundation pit; the steps are circulated until soil body unloading in all ranges of the excavation side of the foundation pit is completed, and horizontal soil pressure and horizontal displacement of different sections of the pile body of the corresponding support pile after the soil body is excavated in each step are recorded;
the twelfth step: and processing the data to calculate the internal force of the supporting pile and the horizontal displacement of different positions of the pile length corresponding to each working condition, thereby realizing the simulation of the whole excavation process of the foundation pit with the single-support structure.
Compared with the prior art, the invention has the beneficial effects that: the foundation pit supporting structure is simplified into a plane strain condition, the soil pressures on two sides of the supporting structure are simplified into springs, the static soil pressures are assumed on two sides of the supporting structure before foundation pit excavation, then the spring on the uppermost layer on the right side is unloaded, which is equivalent to pile side soil layer excavation, then the static balance on two sides of the supporting structure is destroyed, the soil pressure on the side, which is not excavated, of the supporting pile is converted into active soil pressure from the static soil pressure, and new balance is reestablished by taking the supporting pile as an object along with the deformation of the supporting pile, so that foundation pit first-step excavation simulation and dynamic change simulation of the soil pressure on the outer side of the pile side are realized; and repeating the process to complete the second-step excavation simulation, then loading the unloaded second group of pressure applying assemblies on the right side to the supporting pile again according to the internal supporting force loaded as required to realize the single-support loading simulation, finally unloading the pressure applying assemblies on the right side of the lower part of the single support in sequence according to the preset working condition until the unloading of the soil body in all ranges of the excavation side of the foundation pit is completed, automatically stretching and deforming the springs on the two sides of the supporting pile after each step of loading and unloading, and reestablishing the static balance on the inner side and the outer side of the supporting pile after the foundation pit is excavated, thereby realizing the dynamic change simulation of the soil pressure change on the inner side. Therefore, the simulation device realizes physical simulation and visualization of the stress process of the single-support supporting and retaining structure of the foundation pit, can realize dynamic change of soil pressure, is closer to the actual stress condition of the foundation pit, and has certain guiding significance on foundation pit engineering research.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic view of a loading device composed of a pressure applying assembly and a pressure transmitting assembly according to the present invention.
Fig. 3 is a sectional view of section a-a in fig. 1.
Fig. 4 is a schematic structural view of a positioning adjustment assembly according to the present invention.
Fig. 5 is a schematic structural view of a pressing assembly according to the present invention.
In the figure: in the figure: the device comprises a counter-force frame 1, a top cross beam 11, a bottom cross beam 12, a side beam 13, a groove 14, a pile feeding hole 15, a bottom hole 16, a pressure applying assembly 2, a hollow threaded rod 21, a spring 22, a sleeve 23, a force transmission rod 24, a limiting plate 25, a piston 26, a loading handle 27, a positioning rod 28, a pressure transmission assembly 3, a bearing plate 31, a connecting plate 32, a force transmission plate 33, a U-shaped groove 34, a cushion block 35, a positioning hole 36, a connecting pin 37, a positioning adjusting assembly 4, a positioning plate 41, a supporting plate 42, a reserved hole 43, a positioning cross beam 44, an adjusting nut 45, an adjusting rod 46, an inserting hole 47, a model pile 5, a testing system 6, a pressure sensor 61, a displacement sensor 62, a pressure sensor control system 63 and a displacement sensor control system 64.
Detailed Description
As shown in fig. 1 to 5, the invention relates to a simulation device for a single-support type structure foundation pit excavation process, which comprises a counterforce frame 1, a pressure applying assembly 2, a pressure transmitting assembly 3, a positioning and adjusting assembly 4, a model pile 5 and a test system 6; the pressure applying assemblies 2 are symmetrically arranged on the side surfaces of two sides of the reaction frame 1, the pressure transmitting assemblies 3 and the positioning adjusting assemblies 4 correspond to the pressure applying assemblies 2 and are both positioned in the reaction frame 1, the pressure applying assemblies 2 and the pressure transmitting assemblies 3 are correspondingly connected together to apply loads to the model piles 5 arranged in the reaction frame 1, and the testing system 6 is used for testing the pressure and the offset displacement on the side surfaces of the model piles 5;
the reaction frame 1 is a rectangular closed frame, the reaction frame 1 comprises a top cross beam 11, a bottom cross beam 12 and side beams 13, the top cross beam 11 and the bottom cross beam 12 are both horizontally arranged, the two side beams 13 are vertically arranged between the top cross beam 11 and the bottom cross beam 12 and are matched with the top cross beam 11 and the bottom cross beam 12 to form a rectangular frame structure, grooves 14 are respectively arranged on the inner sides of the top cross beam 11 and the bottom cross beam 12, the grooves 14 are oppositely arranged, a pile feeding hole 15 is arranged in the middle of the top cross beam 11 in the vertical direction, the pile feeding hole 15 is a through hole, a bottom hole 16 is arranged on the bottom cross beam 12 corresponding to the position right below the pile feeding hole 15, and the bottom hole 16 is a blind hole;
the structure of the pressing component 2 is as follows: including hollow threaded rod 21, spring 22, sleeve 23, dowel steel 24, limiting plate 25, piston 26, loading handle 27 and locating lever 28, sleeve 23 transversely runs through the curb girder 13 of reaction frame 1 one side, just the both ends of sleeve 23 all are provided with the internal thread, the outer end of the relative curb girder 13 of sleeve 23 is connected with hollow threaded rod 21, the inner of the relative curb girder 13 of sleeve 23 is provided with limiting plate 25, threaded connection is passed through on sleeve 23 to the one end of hollow threaded rod 21, the other end of hollow threaded rod 21 is provided with loading handle 27, be provided with locating lever 28 in the sleeve 23, the one end of locating lever 28 inserts in the hollow threaded rod 21, the other end of locating lever 28 is connected on the piston 26 that is located sleeve 23, and piston 26 can move in sleeve 23 along with locating lever 28, the cover is equipped with spring 22 on the locating lever 28 between piston 26 and the hollow threaded rod 21, the dowel bar 24 penetrates through the limiting plate 25, one end of the dowel bar 24 is connected with the piston 26, the other end of the dowel bar 24 is connected with the pressure transmission assembly 3, and a connecting through hole is formed in the side face of the rod end at the connecting position of the dowel bar 24 and the pressure transmission assembly 3;
the structure of the pressure transmission component 3 is as follows: the pressure bearing plates 31 are symmetrically arranged on the left side and the right side of the model pile 5, the cushion blocks 35 are arranged between the pressure bearing plates 31 and the model pile 5, the pressure bearing plates 31 are connected with the connecting plates 32 through the two force transfer plates 33, the two force transfer plates 33 are arranged in a splayed shape, the U-shaped grooves 34 are vertically arranged on the connecting plates 32, the force transfer rods 24 are inserted into the U-shaped grooves 34, the positioning holes 36 are vertically arranged on two side faces of the U-shaped grooves 34, and the force transfer rods 24 are fixed on the connecting plates 32 through the connecting pins 37 penetrating through the positioning holes 36 and the connecting through holes of the force transfer rods 24;
the positioning and adjusting assembly 4 has the structure that: the pile model structure comprises positioning plates 41 and supporting plates 42, wherein the two supporting plates 42 are respectively arranged on the front side and the rear side of a model pile 5, the upper end and the lower end of each supporting plate 42 are correspondingly arranged in grooves 14 of a top cross beam 11 and a bottom cross beam 12, two rows of preformed holes 43 are longitudinally and equidistantly arranged on each supporting plate 42, each preformed hole 43 comprises a cross beam notch and a test notch, the cross beam notches and the test notches are arranged at intervals up and down, positioning cross beams 44 are arranged in the cross beam notches, the test notches are used for installing pile side displacement sensors, two positioning plates 41 are arranged between the corresponding positioning cross beams 44 on the two supporting plates 42, one ends of the two positioning plates 41 are arranged on the positioning cross beams 44, and the other ends of the two positioning plates 41 are respectively arranged on a bearing plate 31 and a connecting;
the structure of the test system 6 is as follows: including pressure sensor 61, displacement sensor 62, pressure sensor control system 63 and displacement sensor control system 64, it is a plurality of pressure sensor 61 corresponds the setting respectively in the geometric center department of every bearing plate 31 towards the surface that model pile 5 belongs to, and is a plurality of displacement sensor 62 corresponds the setting respectively in the test groove mouth of backup pad 42, pressure sensor 61 and displacement sensor 62 are connected with pressure sensor control system 63 and the displacement sensor control system 64 that set up outside reaction frame 1 respectively.
An adjusting rod 46 is vertically arranged at the bottom side of the positioning cross beam 44, threads are arranged on the outer side of the adjusting rod 46, the lower end of the adjusting rod 46 is correspondingly inserted into a jack 47 arranged at the bottom edge of the opening of the cross beam, an adjusting nut 45 is installed, the depth of the jack 47 is larger than the length of the adjusting rod 46, the internal thread of the adjusting nut 45 is matched with the external thread of the adjusting rod 46, and the adjusting nut 45 is rotated to position the upper position and the lower position of the adjusting rod 46, so that the positioning cross beam 44 reaches a corresponding height and keeps.
The dowel bar 24 can only be adjusted up and down in the U-shaped groove 34 and can rotate at a small angle in a vertical plane, so that the axle center or small eccentric loading of the bearing plate can be realized.
The invention relates to a simulation method for the excavation process of a foundation pit with a single-support structure, which is implemented according to the following steps:
the first step is as follows: installing a counterforce frame 1;
fixing the counterforce frame 1 on the ground to ensure that the bottom cross beam 12 is horizontally arranged and the side beam 13 is vertically arranged;
the second step is that: determining parameters of the model pile 5;
determining the pile length of the model pile 5, wherein the pile length is the pile top reserved length + the calculated pile length + the pile end reserved length, the calculated pile length is the length determined by the distance between the pile top and the pile end of the support pile according to the proportion, and the width of the pile for applying a lateral soil pressure surface, and the shape of the lateral soil pressure curve of the pile length and the shape of static soil pressure along the edge before the excavation of a soil layer on the side of the pile;
the third step: installing a positioning adjusting component 4;
the support plate 42 is arranged between the top cross beam 11 and the bottom cross beam 12, the upper end and the lower end of the support plate 42 are fixed in the groove 14, and the vertical axis of the support plate 42 is ensured to be coincident with the plumb line; an adjusting rod 46 is arranged in a jack 47 in the notch of each cross beam, the adjusting rod 46 penetrates through an adjusting nut 45, the upper end of the adjusting rod 46 is fixed on the positioning cross beam 44, and all the positioning cross beams 44 at the same height are positioned on the same horizontal plane by rotating the adjusting nut 45;
the fourth step: installing a pressure applying component 2 and a pressure transmitting component 3 on the side of the model pile 5;
the pressing assembly 2 is processed in advance, two ends of a sleeve 23 penetrate through side beams 13 of the reaction frame 1, a spring 22 is arranged outside a positioning rod 28, one end of the positioning rod 28 is sequentially connected with a piston 26 and a dowel bar 24, the dowel bar 24 penetrates through a limiting plate 25 and is inserted into a U-shaped groove 34 of a connecting plate 32, contacts with the bottom plane of the U-shaped groove 34 and is fixed with the connecting plate 32 through a connecting pin, the other end of the positioning rod 28 is inserted into a hollow threaded rod 21, the hollow threaded rod 21 is connected with the sleeve 23 through a screw thread, and a loading handle 27 is additionally arranged at the outer end of the hollow; mounting a pressure sensor at a reserved position of the geometric center of a bearing plate 31 of each pressure transmission assembly 3, wherein the surface of the pressure sensor facing the model pile 5 is flush with the surface of the bearing plate 31, mounting a cushion block 35 on the surface of one side, facing the model pile 5, of the bearing plate 31, and connecting each pressure transmission assembly 3 to a corresponding positioning cross beam 44 through a positioning plate 41;
the fifth step: manufacturing and installing a model pile;
filling a proper amount of filling soil into a bottom hole 16 of the reaction frame 1, compacting according to a set compactness, then hoisting a prefabricated model pile 5 into the reaction frame 1 through a pile feeding hole 15 reserved in the top cross beam 11, inserting the bottom end of the model pile 5 into the bottom hole 16, determining the depth of the model pile 5 inserted into the bottom hole 16 according to the embedding condition of the model pile 5, adjusting the verticality of the model pile 5 to enable the longitudinal axis of the model pile 5 to coincide with a plumb line, and filling and compacting a gap between the bottom hole 16 and the model pile 5 by using the filling soil;
and a sixth step: adjusting the loading direction of the model pile side pressing assembly and loading;
the normals of the symmetrically arranged bearing plates 31 distributed on both sides of the model pile 5 are ensured to be on the same horizontal straight line, according to the distribution form of the pile lateral soil pressure, the eccentricity of the two bearing plates 31 which are symmetrical to the left and the right of each pressure transmission assembly 3 is determined by determining the height deviation between the horizontal axis of the two bearing plates 31 which are symmetrical to the left and the right of each pressure transmission assembly 3 and the horizontal axis of the force transmission rod 24, then the vertical position of the end part of the dowel bar 24 in the U-shaped groove 34 is adjusted to ensure that the axes of the symmetrical dowel bars 24 at the two sides are superposed, the dowel bar 24 is fixed to the connection plate 32 by the connection pin 37 penetrating the positioning hole 36 and the connection through-hole of the dowel bar 24, ensuring a reliable connection, thus, the horizontal adjustment of a set of pile side pressure applying assembly 2 and pressure transmitting assembly 3 is completed, and the process is circulated until the adjustment of all the pile side pressure applying assemblies 2 and pressure transmitting assemblies 3 within the pile length calculation range is completed; rotating the loading handle 27 of the pressure applying assembly 2 to apply initial soil pressure to the pile side of the model pile 5 according to the calculated pile length pile side soil pressure distribution form determined in the second step;
the seventh step: excavating a first layer of soil body according to the actual working conditions of excavation of the foundation pit, namely, a loading device a of the topmost layer on one side in the simulation device1The loading handle 27 is rotated to move the force transmission rod 24 of the loading device to the outside of the side beam 13, and then the force transmission plate 33 of the pressure transmission assembly 3 is pulled to be separated from the simulation pile 5, so that the reaction force F originally acting on the simulation pile 5 is10, is equivalent to the first layer soil layer is excavated, because the original symmetrical stress balance state is destroyed, the number b of the symmetrical loading devices arranged on the right side of the model pile 5 is equal to the number b of the symmetrical loading devices arranged on the right side of the model pile1Continuously acting on the simulation pile 5, namely acting on the support pile under the action of the active soil pressure of the soil body outside the foundation pit, and bending and deforming the top of the simulation pile 5 to the left, and then acting on the loading device b at the right side1The middle spring 22 extends, static soil pressure is converted into active soil pressure, and other parts along the length of the simulation pile 5 are subjected to corresponding bending deformation until finally reaching the force balance state again, so that the first-step excavation simulation of the foundation pit is realized;
eighthly, recording the readings of the displacement sensors 62 and the readings of the pressure sensors 61 along the two sides of the pile length range, and processing the data to obtain the horizontal soil pressure and the horizontal displacement of different sections of the pile body of the excavation working condition support pile;
the ninth step: in the seventh step, the loading device a is rotated2The loading handle 27 of the loading device makes the force transmission rod 24 of the loading device move towards the outer side of the side beam 13, and then the force transmission plate 33 of the pressure transmission assembly 3 is dragged to be separated from the simulation pile 5, so that the counter force F originally acting on the simulation pile 52Simultaneously recording the readings of the displacement sensors 62 and the readings of the pressure sensors 61 along the two sides of the pile length range to realize the second-step excavation simulation of the foundation pit;
the tenth step: rotary loading device a2The loading handle 27 of the loading device makes the dowel bar 24 of the loading device move towards the simulation pile 5, then the dowel plate 33 of the pressure transmission assembly 3 is pushed to contact the simulation pile 5, and the loading device a is continuously rotated2By applying a counter-force F acting on the dummy pile 52＝F2＇，F2' acting force of the anchor rod on the simulation pile 5, and simultaneously recording the readings of the displacement sensors 62 and the readings of the pressure sensors 61 along the two sides of the pile length range to realize the simulation of the single-layer anchor rod support of the foundation pit;
the eleventh step: in the seventh step, the loading device a is rotated in sequence3And a4The loading handle 27 of the loading device makes the force transmission rod 24 of the loading device move towards the outer side of the side beam 13, and then the force transmission plate 33 of the pressure transmission assembly 3 is dragged to be separated from the simulation pile 5, so that the counter force F originally acting on the simulation pile 53Simultaneously recording the readings of the displacement sensors 62 and the readings of the pressure sensors 61 along the two sides of the pile length range when the pile length is equal to 0, and realizing excavation simulation of the fourth step and the fifth step of the foundation pit; the steps are circulated until soil body unloading in all ranges of the excavation side of the foundation pit is completed, and horizontal soil pressure and horizontal displacement of different sections of the pile body of the corresponding support pile after the soil body is excavated in each step are recorded;
the twelfth step: and processing the data to calculate the internal force of the supporting pile and the horizontal displacement of different positions of the pile length corresponding to each working condition, thereby realizing the simulation of the whole excavation process of the foundation pit with the single-support structure.
The simulation process of the present invention is explained in detail below.
1. And (5) installing a counterforce frame. And fixing the bottom cross beam of the reaction frame on the ground, enabling the top surface of the bottom cross beam to be horizontal, sequentially assembling the side beams and the top cross beam on two sides, keeping the axes of the side beams on two sides on a plumb line, and simultaneously ensuring that the axes of the top cross beam and the bottom cross beam are vertical to the axes of the side beams on two sides, thereby completing the installation of the reaction frame.
2. Determining the pile length (pile length is the pile top reserved length + calculating the pile length + pile end reserved length, and calculating the pile length is the length determined by the distance from the pile top to the pile bottom of the support pile according to the similarity ratio) of the simulation pile and the surface for applying lateral soil pressureThe width (B) of the pile and the shape of the lateral soil pressure curve (and the shape of static soil pressure) along the length of the pile before the excavation of the soil layer on the side of the pile are calculated, the lateral soil pressure curve is divided into n equal parts along the length of the pile, n is more than or equal to 6, generally 6 to 10, then the midpoint coordinate (i) of each section is determined, the midpoint coordinate (i) of each section is taken as a base point, and p of the lateral soil pressure curve at the corresponding point of the upper L/2(L is the length of the bearing plate) and the lower L/2(L is the length of the bearingi onAnd pi below，pi onAnd pi belowThe soil counter force between the two bearing plates is approximately linearly determined, and the force F required to be applied by the section of bearing plate isiComprises the following steps:
Fi＝(pi on+pi below)BL/2
Corresponding eccentricity eiComprises the following steps:
ei＝(L/6)×(pi below-pi on)/(pi on+pi below)。
Thus, the number of sets a of the pile-side loading device is determinedi(bjJ), wherein any 1 set of pile side loading device ai(bj) Comprises 1 group of pile side pressing components and pressure transmitting components.
3. And installing a positioning adjusting assembly. The front supporting plate and the rear supporting plate are symmetrically arranged between the top cross beam and the bottom cross beam relative to the axis of the side beam, and are fixed in the grooves of the counter cross beams from top to bottom, and the vertical axes of the front supporting plate and the rear supporting plate are ensured to coincide with a plumb line. And an adjusting rod is arranged in a jack in the notch of each cross beam, the adjusting rod penetrates through an adjusting nut, the upper end of the adjusting rod is fixed on the positioning cross beam, and the adjusting nut is rotated to enable the positioning cross beam to be horizontal, so that the positioning cross beam is arranged. The number of the beam notches on the front supporting plate and the rear supporting plate is 2n, and the height of each beam notch is matched with the midpoint coordinate (i) of each subsection of the lateral soil pressure curve.
4. And installing a pile side loading device. The bearing plate, the connecting plate, the force transmission plate and the positioning plate are integrated components and are machined in advance, a pressure sensor is installed at a reserved position of the geometric center of the bearing plate, the surface of the sensor facing the simulation pile is flush with the surface of the bearing plate, and then a cushion block is installed on the surface of one side, facing the model pile, of the bearing plate. Each pressure transmission assembly is placed in the long hole of the corresponding positioning cross beam 22 through the positioning plate, a connecting rod is respectively led out from the centers of the left side edge and the right side edge of the bearing plate and the connecting plate, the connecting rods on the two sides of the bearing plate are front positioning plates, the connecting rods on the two sides of the connecting plate are rear positioning plates, when the front positioning plates and the rear positioning plates on one side of the bearing plate and the connecting plate are installed in the long hole of the positioning cross beam of a certain testing notch of the front supporting plate, the front positioning plates and the rear positioning plates on the other side of the bearing plate and the connecting plate are installed in the long hole of. And then installing the matched pressure applying assembly. The sleeves of the 1 group of pressure applying assemblies are fixed in reserved holes of the side beams of the counterforce frame, and two ends of each sleeve penetrate through the side beams. The external spring of locating lever is connected with piston and dowel steel in proper order, and the dowel steel passes limiting plate and inserts the U type groove and the tank bottom plane contact of connecting plate to it is fixed with the connecting plate through the connecting pin. The other end of the positioning rod in the tube is sleeved in a hollow threaded rod, the threaded rod is connected with the sleeve through a screw thread, and the loading handle is additionally arranged at the outer end of the threaded rod. Thereby completing 1 set of the pile side pressure applying assembly and the pressure transmitting assembly. Repeating the above processes to complete another 1 group of pile side pressure applying assembly and pressure transmitting assembly which are symmetrical with the pile side pressure applying assembly and the pressure transmitting assembly, thus completing any set of pile side loading device. And then all pile side loading devices are installed according to the installation program, and the connecting line of each pressure sensor is connected with a sensor control system.
5. And (5) manufacturing and installing the model pile. Filling a proper amount of filling soil into the bottom hole, compacting according to a certain compactness, then hoisting the prefabricated model pile into a simulation device through a pile feeding hole reserved in the top cross beam, inserting the bottom end of the model pile into the bottom hole, determining the depth of the model pile inserted into the bottom hole according to simulation embedment conditions (free or embedment), adjusting the verticality of the model pile to ensure that the longitudinal axis of the pile coincides with a plumb line, and filling and compacting the peripheral gap of the bottom hole pile by using the filling soil.
6. Adjusting the pile side loading devices to ensure that every 1 set of symmetrically-arranged pile side loading device force transfer plates with the same left and right sides in the pile length range are closely attached to the side surfaces of the model piles through the cushion blocks, and simultaneously determining e corresponding to each pile side loading device set determined by the lateral soil pressure curve in the step 2iAdjusting 4 sets of settings associated with the set of pile side loading meansAdjusting nuts for the cross-beam, when pi below≥pi onWhen the pressure transmission component is arranged at a distance e above the symmetry axis of the pressure application componentiAnd vice versa. Meanwhile, all horizontal pipes on positioning cross beams on two sides of the model pile and horizontal round levels on the pressure transmission assemblies are ensured to be centered, namely, the horizontal pipes are ensured to be distributed on the same horizontal straight line of the normal lines of the pressure transmission plates symmetrically arranged on two sides of the model pile, symmetrical shafts of the pressure application assemblies symmetrically arranged are also on the same horizontal straight line, then nuts on the rotary connecting pins are used for fixing the vertical positions of the pressure transmission rods in the U-shaped grooves, the reliable connection between the pressure transmission rods and the connecting plates is realized, and thus, the horizontal adjustment of the pile side loading device 1 set is completed. And the pile side loading devices are adjusted within all the pile length ranges through the circulation.
7. And applying pressure to the side soil of the pile before excavation of the foundation pit. F corresponding to each group of pile side loading devices determined according to the step 2iSimultaneously rotating the loading handles at both sides, and adjusting the length of the spring to pre-calculate the applied force F of each segment iiApplying a force FiThe size of the model pile is determined according to the reading of the pressure sensor, so that symmetrically distributed lateral soil pressure curves are applied to the two sides of the model pile, and the loading of the lateral soil pressure of the support pile before the foundation pit is excavated is realized. At this time, because the soil pressure on the two sides of the model pile is symmetrically applied, the longitudinal axis of the model pile is vertical to the ground.
8. And (3) symmetrically installing displacement sensors at the central point of the gap of the model pile installation dowel plates along the pile length, and fixing the displacement meter on the displacement support frame. The sensors are adjusted and the initial reading of each sensor is recorded. Thus, the installation of the foundation pit excavation simulation device and the loading of the static soil pressure are completed.
9. And excavating and unloading the first layer of soil body on the inner side of the foundation pit. Assuming that the static soil pressure on the side surface of the simulation pile is distributed in a triangular mode, the sectional length L of the soil pressure on the side surface of the pile represents the thickness of 1 layer of soil and the thickness of 1 layer of soil of the corresponding foundation pit excavated each time, and excavating the first layer of soil according to the actual working condition of excavation of the foundation pit from the pile top, namely excavating the loading device a on the topmost layer on one side of the simulation device1The loading handle rotates to make the dowel bar of the loading device move towards the outer side of the side beam,the force-transmitting plate with the pressure-transmitting assembly is pulled away from the simulation pile, so that the counter-force F originally acting on the simulation pile1Equal to 0, the first layer of soil is excavated. The number b of sets of symmetrical loading devices arranged on the right side of the model pile (support pile) is reduced due to the original symmetrical stress balance state being destroyed1Continuously acting on the simulation pile, namely acting on the support pile under the action of the active soil pressure of the soil body outside the foundation pit, and bending and deforming the top of the simulation pile leftwards, and then acting on the loading device b at the right side1And (3) extending the middle spring, converting static soil pressure into active soil pressure, and generating corresponding bending deformation along the length of the simulation pile and at other parts until finally reaching the force balance state again, thereby realizing the first-step excavation simulation of the foundation pit.
10. Recording the readings of the displacement meters and the readings of the pressure sensors at two sides along the length range of the pile, and processing the data to obtain the horizontal soil pressure and the horizontal displacement of different sections of the pile body of the excavation working condition support pile;
11. in the same step 9, the loading device a is rotated2The loading handle makes the dowel bar of the loading device move to the outer side of the side beam, and then pulls the dowel plate of the pressure transmission assembly to separate from the simulation pile, so that the counter force F originally acting on the simulation pile2And simultaneously recording the readings of the displacement meters and the readings of the pressure sensors along the two sides of the pile length range to realize the second-step excavation simulation of the foundation pit.
12. Rotary loading device a2The loading handle makes the force transfer rod of the loading device move towards the simulation pile, then pushes the force transfer plate of the pressure transfer component to contact the simulation pile, and continues to rotate the loading device a2The loading handle of (2) to make the counter force F acting on the simulation pile2＝F2＇，F2' is the force of the anchor rod on the simulated pile, and simultaneously records the readings of the displacement meter and the readings of the pressure sensor along the two sides of the pile length range. And the simulation of the single-layer anchor rod support of the foundation pit is realized.
13. In the same step 9, the loading device a is rotated in sequence3And a4The loading handle enables the dowel bar of the loading device to move towards the outer side of the vertical side beam, and then the dowel plate of the pressure transmission assembly is dragged to be separated from the simulation pile, so thatOriginal reaction force F acting on simulation pile3The readings of the displacement gauge and the pressure sensor along both sides of the pile length range are recorded simultaneously as 0. The excavation simulation of the fourth step and the fifth step of the foundation pit is realized; the steps are circulated until soil body unloading in all ranges of the excavation side of the foundation pit is completed, and horizontal soil pressure and horizontal displacement of different sections of the pile body of the corresponding support pile after the soil body is excavated in each step are recorded;
14. and processing the data to calculate the internal force of the supporting pile and the horizontal displacement of different positions of the pile length corresponding to each working condition, thereby realizing the simulation of the whole excavation process of the foundation pit single-support retaining structure.
The reaction frame is a rectangular closed frame, the middle part of the top cross beam is provided with a pile feeding hole, the center of the bottom cross beam is provided with a bottom hole, and the geometric centers of the pile feeding hole and the bottom hole are on the same vertical line. The size of the pile feeding hole is larger than that of the simulation pile, and the simulation pile can be placed in the simulation device through the pile feeding hole. The simulation pile is placed in the symmetric center of the simulation device. The bottom hole is perpendicular to the axial direction of the beam and is equal to B, the direction parallel to the axial direction of the beam is L, the depth of a pile end entering hole is not less than B and not less than 100mm (B and L are respectively the section width and the length of the model pile), filling soil with certain thickness and compactness can be filled in the bottom hole as required, and the filling soil thickness can be used for determining the embedding and fixing conditions of the simulation pile. The rigidity requirement of reaction frame is great rather than the reaction that its provided, and the in-process deformation that provides the reaction can be ignored, and the matter material can select for use reinforced concrete prefabrication or steel sheet preparation.
The section of the model pile is a rod piece with the shape of rectangle, square or I shape, and the like, and the material can be reinforced concrete, steel, wood and the like.
The loading device comprises a pressure applying assembly and a pressure transmitting assembly, the loading device is sequentially and symmetrically arranged from top to bottom for at least more than 6 groups, each group of loading devices is provided with a left group and a right group, the two groups of loading devices are symmetrically arranged at two sides of the model pile, the loading devices are numbered from top to bottom, and the numbering of the left side is a from the front viewi(i-1, 2, … n) with the numbering a on the rightj(j ═ 1,2, … n). The specifications and the models of the left and the right systems of the same group of loading devices are the same, but notThe specifications and the types of the two sets of loading spring systems in the same group can be the same or different, but the components of the two sets of loading spring systems are consistent. The loading plates on the left side and the right side of the loading device are identical in specification, rigidity and quality. Any pile side loading device comprises a pile side pressing assembly and a pressure transmitting assembly.
Any set of pile side loading device a of the inventioni(or a)j) In the subassembly of exerting pressure, the sleeve is fixed in the reservation hole of curb girder, the curb girder is passed at both ends, the sleeve both ends set up the internal thread, the middle part inner wall is smooth, sleeve outer end installation hollow threaded rod, hollow threaded rod tip installation loading handle, other end outer tube wall is the screw thread, screw thread and sleeve internal thread phase-match, and with sleeve outer end threaded connection, hollow threaded rod inner wall is smooth, the locating lever is gone into to the cover in the pipe, the external spring of locating lever just is connected with piston and dowel steel in proper order, and install in the sleeve, the dowel steel passes the stopper at the sleeve other end and is connected with the connecting plate of biography pressure subassembly, the stopper passes through screw thread and muffjoint. The outer diameter of the positioning rod is matched with the inner diameter of the loading handle, the outer diameter of the piston is matched with the inner diameter of the sleeve, and the outer diameter of the dowel bar is matched with the inner diameter of the limiter, and lubricating oil is smeared on the dowel bar and can smoothly move. The pressure applying assembly controls the extension and retraction of the spring by rotating the hollow threaded rod through the loading handle so as to change the output force and provide counter force for the pile side. The material and the elastic modulus of the spring are determined according to the mechanical characteristics of the soil body, and the control error is within a reasonable range. The model and specification of the spring are determined according to the specification of the model pile and the size of the counterforce required to be provided.
Any set of pile side loading device a of the inventioni(or a)j) The pressure transmission assembly comprises a bearing plate, a connecting plate, a force transmission plate, a groove, a front positioning rod, a rear positioning rod, a positioning hole, a horizontal circle level, a connecting pin and a cushion block. The bearing plates are symmetrically arranged on two sides of the model pile and are rectangular thick plates, the width of each bearing plate is the same as that of the model pile, the height of each bearing plate is determined according to the length of the model pile and the number of the pile side loading plates, steel plates or high polymer composite materials are selected for use as quality materials, the thickness of each bearing plate can be selected for use according to the loading counter force, and the counter force applied to the pile by the loading process plates is guaranteed to be linear load. One side of the bearing plate is contacted with the side surface of the model pile through the cushion block, and the other side of the bearing plate is sequentially connected with 2 eight blocksThe force transmission plates arranged in a shape like the Chinese character 'ji' are connected with the connecting plate and connected with a force transmission rod of the pressure applying assembly, and the force transmission rod is inserted into a U-shaped groove of the connecting plate to be contacted with the bottom plane of the groove and is fixed with the connecting plate through a connecting pin. The dowel bar can be adjusted up and down in the U-shaped groove and can rotate in a vertical plane at a small angle. The upper and lower face of connecting plate is the plane, goes up the horizontal circle level of plane installation, and one side of connecting plate towards the dowel steel is two vertical face confined U type grooves, and U type bottom of the groove portion is the plane, and the notch width matches with dowel steel tip size, and notch length is 1/3L + D, and L is the length of bearing plate, and D is hydro-cylinder fore-set tip diameter. Two vertical surfaces of the U-shaped groove are vertically provided with strip-shaped positioning holes, and the length of each positioning hole is 1/3L + d1，d1Is the diameter of the connecting pin. A connecting rod is respectively led out from the centers of the left side edge and the right side edge of the bearing plate and the connecting plate, the connecting rods on the two sides of the bearing plate are front positioning rods, the connecting rods on the two sides of the connecting plate are rear positioning rods, the front positioning rods and the rear positioning rods are cylindrical, the diameters of the front positioning rods and the rear positioning rods are the same, and the size of the front positioning rods2The positioning rod is supported on the positioning beam of the positioning adjusting system, the pressure transmission assembly can select stainless steel, steel and high-strength plastic except for the cushion block, and the cushion block can select flexible materials such as rubber and cork.
The positioning adjusting device comprises a support frame and a positioning cross beam. The support frame comprises a front support frame and a rear support frame, wherein the front support frame and the rear support frame are symmetrically arranged between the upper cross beam and the lower cross beam about the axis of the upright column and are vertically fixed in the clamping grooves of the cross beams. The front support frame and the rear support frame are identical in specification, size, material, style and the like. The support frame is the platelike component that multiunit hole was reserved to upper portion, and reserve the hole and be two, and follow the vertical central line symmetrical arrangement of support frame, and every row of reservation hole includes crossbeam notch and test notch, and crossbeam notch and test notch are arranged along vertical line in turn, and the group number and the vertical position of crossbeam notch and pressure device's group number and vertical position phase-match. The vertical position of the test notch is the height corresponding to the gap between the two groups of pressure plates. The crossbeam notch is used for installing the location crossbeam, and the test notch is used for installing stake side displacement sensor. The support frame is made of steel.
Any set of pile side loading device a of the inventioni(or a)j) 2 sets of positioning beams are arranged in the middle support, and 1 set of positioning beam is arranged in the front support and is connected with a pile side loading device ai(or a)j) In the corresponding height beam notch, another set of positioning beam is mounted in the rear supporting frame and is connected with pile side loading devicei(or a)j) In the corresponding height beam notch, the specifications, models and adjustment modes of the front and rear 2 sets of positioning beams are the same, so that the number of the front support frame and the rear support frame upper beam notches 20 is the same and is 2n (the number of n sets of loading devices).
Any set of positioning beam comprises a U-shaped groove, a positioning beam, a horizontal pipe, an adjusting rod, an insertion hole, an adjusting nut and a long hole. The positioning beam is installed in the notch position of the beam, the axis of the positioning beam is parallel to the horizontal axis of the dowel of the corresponding pressurizing device, and the initial position is lower than the horizontal axis 1/2d of the dowel of the corresponding pressurizing device2(d2Where the diameter of the front or rear positioning rods). The positioning beam is a rod piece with a rectangular cross section, the long side direction of the cross section is parallel to the vertical direction, a long hole is formed in the direction perpendicular to the long side of the cross section along the axis of the rod piece, and the length of the short side of the long hole is d2And the positioning plate is arranged in the long hole of the positioning beam. The utility model discloses a support frame, including support frame crossbeam notch lateral wall, the support frame crossbeam notch lateral wall is installed in the vertical U type recess, outside side mid-mounting horizontal tube, be close to 2 vertical regulation poles of location crossbeam both ends base installation, the connecting rod outward appearance is carved with the screw thread, the lower extreme inserts in the corresponding jack on crossbeam notch base, and install oblate adjusting nut, the degree of depth of jack is greater than the length of adjusting rod, the internal screw thread of nut and the external screw thread phase-match of adjusting the pole, rotatory nut location adjusting pole upper and lower position makes the location crossbeam reach and corresponds the height and keep the level. 4 sets of positioning beams with corresponding heights can be adjusted through the front and rear support frames before work, so that the horizontal pipes of the positioning beams and the horizontal circle level on the upper plane of the connecting plate are centered, the axes of a group of pile side loading systems opposite to each other at the unified position can be on the same straight line respectively, and the normals of the 2 opposite bearing plates are located on the same straight line and are perpendicular to the pile side plane. Or according to the test requirements, determining the distance between the horizontal axis of the two bilaterally symmetrical loading plates of each set of loading system and the horizontal axis of the dowel barThe eccentricity of the two loading bearing plates which are symmetrical left and right of each set of loading system is determined, and then the distribution form of the pile side soil pressure is determined.
The test system comprises a displacement sensor, a displacement sensor control system, a displacement support frame, a pressure sensor and a pressure sensor control system. The pile side pressure sensor is arranged at the geometric center of the surface of each bearing plate facing the model pile, is connected with the sensor control system and is used for testing the side pressure of the model pile in the loading process. The displacement sensor can select a dial indicator or other electronic displacement sensors, the displacement sensor is arranged in a gap between adjacent bearing plates and extends out of the test notch, the base is fixed on the displacement support frames on two sides of the frame, the measuring sections of each group of the model piles are symmetrically arranged, and the number of the measuring sections is n +1 (the number of the n loading devices). The displacement sensor is used for testing the lateral displacement of different sections of the model pile in the loading process, and the displacement sensor control system is used for acquiring displacement data of all the tested sections.
The invention unloads any height position, and other positions automatically realize corresponding stress and displacement change through loading the spring, and the excavation process of the foundation pit soil body is simulated in real time without manual adjustment.
The present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge of those skilled in the art.

Claims (2)

1. A simulation method for the excavation process of a foundation pit with a single-support structure is characterized by comprising the following steps:
the first step is as follows: mounting a counterforce frame (1);
fixing the counterforce frame (1) on the ground to ensure that the bottom cross beam (12) is horizontally arranged and the side beam (13) is vertically arranged;
the second step is that: determining parameters of the model pile (5);
determining the pile length of the model pile (5), wherein the pile length = pile top reserved length + calculated pile length + pile end reserved length, the calculated pile length is the length determined in proportion by the distance between the pile top and the pile end of the support pile, the width of the pile for applying a lateral soil pressure surface, and the lateral soil pressure curve form of the pile length along the edge before the excavation of the soil layer on the side of the pile, namely the form of the static soil pressure;
the third step: installing a positioning adjusting component (4);
the supporting plate (42) is arranged between the top cross beam (11) and the bottom cross beam (12), the upper end and the lower end of the supporting plate (42) are fixed in the groove (14), and the vertical axis of the supporting plate (42) is ensured to be coincident with the plumb line; an adjusting rod (46) is arranged in a jack (47) in a notch of each cross beam, the adjusting rod (46) penetrates through an adjusting nut (45), the upper end of the adjusting rod (46) is fixed on the positioning cross beam (44), and all the positioning cross beams (44) at the same height are positioned on the same horizontal plane by rotating the adjusting nut (45);
the fourth step: a pressure applying component (2) and a pressure transmitting component (3) are arranged on the side of the model pile (5);
the pressing assembly (2) is processed in advance, two ends of a sleeve (23) penetrate through side beams (13) of a counter-force frame (1), a positioning rod (28) is externally provided with a spring (22), one end of the positioning rod (28) is sequentially connected with a piston (26) and a dowel bar (24), the dowel bar (24) penetrates through a limiting plate (25) and is inserted into a U-shaped groove (34) of a connecting plate (32) and is in contact with the bottom plane of the U-shaped groove (34) and is fixed with the connecting plate (32) through a connecting pin, the other end of the positioning rod (28) is inserted into a hollow threaded rod (21), the hollow threaded rod (21) is connected with the sleeve (23) through a screw thread, and a loading handle (27) is additionally arranged at the outer; a pressure sensor is arranged at a reserved position of the geometric center of a bearing plate (31) of a pressure transmission assembly (3), the surface of the pressure sensor facing a model pile (5) is flush with the surface of the bearing plate (31), then a cushion block (35) is arranged on the surface of one side, facing the model pile (5), of the bearing plate (31), and each pressure transmission assembly (3) is connected to a corresponding positioning cross beam (44) through a positioning plate (41);
the fifth step: manufacturing and installing a model pile;
filling a proper amount of filling soil into a bottom hole (16) of a reaction frame (1), compacting according to a set compactness, then hoisting a prefabricated model pile (5) into the reaction frame (1) through a pile feeding hole (15) reserved in a top cross beam (11), inserting the bottom end of the model pile (5) into the bottom hole (16), determining the depth of the model pile (5) inserted into the bottom hole (16) according to the embedding condition of the model pile (5), adjusting the verticality of the model pile (5) to enable the longitudinal axis of the model pile (5) to coincide with a plumb line, and filling and compacting a gap between the bottom hole (16) and the model pile (5) by using the filling soil;
and a sixth step: adjusting the loading direction of the model pile side pressing assembly and loading;
ensuring that normal lines of bearing plates (31) symmetrically distributed on two sides of a model pile (5) are on the same horizontal straight line, adjusting the vertical positions of the end parts of dowel bars (24) in a U-shaped groove (34) according to the distribution form of pile side soil pressure to ensure that the axes of the symmetrical dowel bars (24) on the two sides are superposed, fixing the dowel bars (24) on a connecting plate (32) by penetrating connecting pins (37) through connecting through holes of a positioning hole (36) and the dowel bars (24) to ensure reliable connection, thus completing the horizontal adjustment of a set of pile side pressure applying assembly (2) and a set of pressure transferring assembly (3), and circulating the steps until the adjustment of the pile side pressure applying assemblies (2) and the set of pressure transferring assemblies (3) within the calculated pile length range is completed; rotating a loading handle (27) of the pressure applying assembly (2) to apply initial soil pressure to the pile side of the model pile (5) according to the calculated pile length pile side soil pressure distribution form determined in the second step;
the seventh step: excavating a first layer of soil body according to the actual working conditions of excavation of the foundation pit, namely, a loading device a of the topmost layer on one side in the simulation device1The loading handle (27) rotates to make the force transmission rod (24) of the loading device move towards the outer side of the side beam (13), and then the force transmission plate (33) of the pressure transmission assembly (3) is dragged to be separated from the simulation pile (5), so that the reaction force F originally acting on the simulation pile (5)1=0, which is equivalent to the first layer of soil layer being excavated, and the original symmetrical stress balance state is destroyed, the number b of the symmetrical loading devices arranged on the right side of the model pile (5) is the number b of the symmetrical loading devices 1 To the simulation pile (5)Continuous action, namely the active soil pressure of the soil body outside the foundation pit acts on the supporting pile to simulate the leftward bending deformation of the top of the pile (5), and then the right loading device b 1 The middle spring (22) extends, static soil pressure is converted into active soil pressure, and other parts along the length of the simulation pile (5) can be correspondingly bent and deformed until the force balance state is reached again finally, so that the foundation pit first-step excavation simulation is realized;
eighthly, recording readings of the displacement sensors (62) and readings of the pressure sensors (61) along the two sides of the pile length range, and processing the data to obtain the horizontal soil pressure and the horizontal displacement of different sections of the pile body of the excavation working condition support pile;
the ninth step: in the seventh step, the loading device a is rotated2The loading handle (27) makes the force transmission rod (24) of the loading device move towards the outer side of the side beam (13), and then the force transmission plate (33) of the pressure transmission assembly (3) is dragged to be separated from the simulation pile (5), so that the counter force F originally acting on the simulation pile (5)2=0, simultaneously recording the readings of the displacement sensors (62) and the readings of the pressure sensors (61) along the two sides of the pile length range, and realizing the second-step excavation simulation of the foundation pit;
the tenth step: rotary loading device a2The loading handle (27) makes the force transmission rod (24) of the loading device move towards the simulation pile (5), then pushes the force transmission plate (33) of the pressure transmission component (3) to contact the simulation pile (5), and continues to rotate the loading device a2The loading handle (27) makes the reaction force F acted on the simulation pile (5)2=F2 ＇，F2 ＇Simultaneously recording the readings of the displacement sensors (62) and the readings of the pressure sensors (61) along the two sides of the pile length range for the action of the support on the simulation pile (5), thereby realizing the simulation of the single-layer support of the foundation pit;
the eleventh step: in the seventh step, the loading device a is rotated in sequence3And a4The loading handle (27) makes the force transmission rod (24) of the loading device move towards the outer side of the side beam (13), and then the force transmission plate (33) of the pressure transmission assembly (3) is dragged to be separated from the simulation pile (5), so that the simulation pile (5) is separated from the force transmission plateThe reaction force F originally acting on the simulation pile (5)3=0, simultaneously recording the readings of the displacement sensors (62) and the readings of the pressure sensors (61) along the two sides of the pile length range, and realizing excavation simulation of the foundation pit in the fourth step and the fifth step; the steps are circulated until soil body unloading in all ranges of the excavation side of the foundation pit is completed, and horizontal soil pressure and horizontal displacement of different sections of the pile body of the corresponding support pile after the soil body is excavated in each step are recorded;
the twelfth step: processing the data to calculate the internal force of the supporting pile and the horizontal displacement of different positions of the pile length corresponding to each step of working condition, thereby realizing the simulation of the whole excavation process of the foundation pit with the single-support structure;
the counterforce frame is a rectangular closed frame and comprises a top cross beam, a bottom cross beam and side beams, wherein the top cross beam and the bottom cross beam are horizontally arranged, the two side beams are vertically arranged between the top cross beam and the bottom cross beam and are matched with the top cross beam and the bottom cross beam to form a rectangular frame structure, grooves are formed in the inner sides of the top cross beam and the bottom cross beam and are oppositely arranged, a pile feeding hole is formed in the middle of the top cross beam in the vertical direction and is a through hole, a bottom hole is formed in the bottom cross beam corresponding to the position right below the pile feeding hole, and the bottom hole is a blind hole;
the structure of the pressure applying assembly is as follows: the device comprises a hollow threaded rod, a spring, a sleeve, a dowel bar, a limiting plate, a piston, a loading handle and a positioning rod, wherein the sleeve transversely penetrates through a side beam on one side of a counter-force frame, inner threads are arranged at two ends of the sleeve, the outer end of the side beam opposite to the sleeve is connected with the hollow threaded rod, the limiting plate is arranged at the inner end of the side beam opposite to the sleeve, one end of the hollow threaded rod is connected onto the sleeve through threads, the loading handle is arranged at the other end of the hollow threaded rod, the positioning rod is arranged in the sleeve, one end of the positioning rod is inserted into the hollow threaded rod, the other end of the positioning rod is connected onto the piston in the sleeve, the piston can move in the sleeve along with the positioning rod, the spring is sleeved on the positioning rod between the piston and the hollow threaded rod, the other end of the dowel bar is connected with the pressure transmission assembly, and a connecting through hole is formed in the side face of the bar end at the joint of the dowel bar and the pressure transmission assembly;
the structure of the pressure transmission assembly is as follows: the device comprises bearing plates, a connecting plate, dowel plates, U-shaped grooves, cushion blocks, positioning holes and connecting pins, wherein the bearing plates are symmetrically arranged on the left side and the right side of a model pile, the cushion blocks are arranged between the bearing plates and the model pile, the bearing plates and the connecting plate are connected together through the two dowel plates which are arranged in a splayed shape, the connecting plate is vertically provided with the U-shaped grooves, the dowel bars are inserted into the U-shaped grooves, the two side surfaces of each U-shaped groove are vertically provided with the positioning holes, and the dowel bars are fixed on the connecting plate through the connecting pins penetrating through the positioning holes and the connecting through holes of the dowel bars;
the structure of the positioning and adjusting assembly is as follows: the pile-side displacement sensor comprises positioning plates and supporting plates, wherein the two supporting plates are respectively arranged on the front side and the rear side of a model pile, two rows of preformed holes are longitudinally arranged on the supporting plates at equal intervals and comprise cross beam notches and testing notches, the cross beam notches and the testing notches are arranged at intervals up and down, positioning cross beams are arranged in the cross beam notches and are used for mounting pile-side displacement sensors, two positioning plates are arranged between corresponding positioning cross beams on the two supporting plates, one end of each positioning plate is arranged on each positioning cross beam, and the other end of each positioning plate is respectively arranged on a bearing plate and a connecting plate;
still include test system, test system's structure is: including pressure sensor, displacement sensor, pressure sensor control system and displacement sensor control system, it is a plurality of pressure sensor corresponds the setting respectively and locates at every bearing plate towards the geometric center on model stake place surface, and is a plurality of displacement sensor corresponds the setting respectively and examines the inslot at the backup pad, pressure sensor and displacement sensor are connected with pressure sensor control system and the displacement sensor control system that sets up outside the reaction frame respectively.
2. The simulation method for the excavation process of the foundation pit with the single-support type structure as claimed in claim 1, wherein the eccentricity of the two bearing plates (31) which are bilaterally symmetrical to each other for each set of the pressure transmission assembly (3) is determined by determining the height deviation between the horizontal axis of the two bearing plates (31) which are bilaterally symmetrical to each other and the horizontal axis of the force transmission rod (24), thereby determining the initial distribution form of the soil pressure on the pile side of the support pile before excavation.
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