CN103882894B - Prestressed concrete pipe pile horizontal bearing characteristic test model and test method - Google Patents

Abstract

The invention discloses prestressed concrete pipe pile horizontal bearing characteristic test model and test method, comprise a model groove, be provided with the cushion cap for carrying Model Pile in described model groove, and the upper end of Model Pile being embedded in cushion cap; Be provided with above described model groove one be connected with reaction frame and cushion cap is implemented to the vertical pneumatic loading system of vertical force, be provided with connected and to cushion cap carrying out horizontal power horizontal pneumatic loading system inside model groove, and be provided with monitoring device in described cushion cap, Model Pile and loading system.The invention provides a kind of loading condition requirement that can control load on pile foundation test preferably, simulate the practical working situation of pile foundation more realistically, probe into the experimental rig of pile tube single pile and clump of piles bearer properties under horizontal loads.

Description

Prestressed concrete pipe pile horizontal bearing characteristic test model and test method

Technical field

The present invention relates to a kind of civil engineering test model and method, especially a kind of bearer properties test model of building structure prestressed concrete pipe pile and method.

Background technology

The bearer properties research of prestressed concrete pipe pile mainly comprises the bearer properties research of pile tube single pile, the bearer properties research of a pile tube clump of piles and a pile tube clump of piles and bears bearer properties research under vertical uniform load q.Because pile foundation belongs to underground construction, uncertain factor is more, and field trial, by the impact of construction period of engineering, environmental factor, human factor, is difficult to the bearer properties of the analysis and research pile foundation of comprehensive multi-state.Therefore present stage depends on the method such as numerical computations, theory analysis for the research of pile foundation.But the methods such as numerical computations are comparatively large by the impact of physical parameter and constitutive model, therefore the authenticity of result of calculation and accuracy are difficult to judge, result differs greatly with engineering is actual sometimes.

Summary of the invention

The object of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of loading condition requirement that can control load on pile foundation test is preferably provided, simulate the practical working situation of pile foundation more realistically, probe into the experimental rig of pile tube single pile and clump of piles bearer properties under horizontal loads.

The technical solution used in the present invention is as follows:

Prestressed concrete pipe pile horizontal bearing characteristic test model, comprises a model groove, be provided with the cushion cap for carrying Model Pile, and the upper end of Model Pile is embedded in cushion cap in described model groove; Be provided with above described model groove one be connected with reaction frame and cushion cap is implemented to the vertical pneumatic loading system of vertical force, be provided with connected and to cushion cap carrying out horizontal power horizontal pneumatic loading system inside model groove, and be provided with monitoring device in described cushion cap, Model Pile and loading system.

Described monitoring device is the dial gauge be arranged on cushion cap, the foil gauge be arranged in Model Pile, be arranged at earth pressure cell around Model Pile.

Described vertical pneumatic loading system comprises Pneumatic jack I, and described Pneumatic jack I is vertically arranged on reaction frame, and described reaction frame is arranged on the top of cushion cap; And be provided with pressure sensor I in jack I end;

Described horizontal pneumatic loading system comprises Pneumatic jack II, and described Pneumatic jack II level is arranged on the inwall of connected model groove, and is provided with pressure sensor II in jack II end.

Described model groove comprises multiple steel plate framework unit linked together, and is embedded with tempered glass at described frame unit; Described tempered glass middle part is provided with the drain hole communicated with the external world; Described Model Pile is organic glass pile tube, outside it, be pasted with resistance strain gage.

The test method of prestressed concrete pipe pile horizontal bearing characteristic test model is as follows:

Step 1 tests the preparatory stage, comprises the sticky note of pile strain sheet, the burying underground of Model Pile, the building of cushion cap;

Step 2 design experiment operating mode, comprises Adjustment Tests stage, horizontal addload experimental stage, horizontal addload and complementary testing stage;

Step 3 determines load mode and the monitoring scheme of load.

The sticky note of the pile strain sheet described in described step 1 comprises the following steps:

(1) chip select: first whether parallel with lens examination wire grid, whether have mildew, rust spot, measure each foil gauge resistance value with digimer;

(2) cleaning on measuring point surface: direct cotton ball dips in acetone and cleans organic glass pile tube surface; Mark the grid line of strain meter again in survey sheet position with marking pen;

(3) paster: foil gauge is pasted on Model Pile grid line according to measurement direction; Then use glue itself and Model Pile to be bondd, at upper cover layer of polyethylene plastic foil as interlayer, in the length direction roll extrusion of strain meter, extrudate piece bubble and unnecessary glue, until strain meter and Model Pile close adhesion;

(4) wiring: twin cable is connected with the wiring terminal of paster, and numbers;

(5) damp-proof treatment: after foil gauge carefully connects the wire and insulaion resistance reaches requirement, adopts glue to carry out damp-proof treatment to strain meter immediately;

(6) measuring point protection: paste adhesive waterproof tape again after using foamed glue to cover;

(7) connect up: concentrate after all first horizontal laying of foil gauge survey line is outer to stake soil deformation effect scope again and go between earthward, in lateral extent, serpentine wire mode taked by survey line.

Model Pile described in described step 1 is buried underground and is comprised the following steps:

(1) Model Pile is fixed in the cushion cap of model groove by the mode that machinery is fixing, and uses spirit level and line pendant to carry out the accurate adjustment of level and vertical direction;

(2) successively fill in model groove, tamp sandy soil, often two-layer banket after choose 3 place's measuring points, use core cutter method to carry out the mensuration of degree of compaction, to control filled soils;

(3) earth pressure cell adopts the mode of anti-excavation to bury underground, lays according to distance model stake outward flange 5cm, ensures that earth pressure cell stress surface is perpendicular to loading direction;

(4), after earth pressure cell has been buried underground, backfill sand is also tamped.

Building of cushion cap described in step 1 comprises the following steps:

Spirit level is first utilized to flatten pile peripheral earth, then cushion cap template is set up, and guarantee the center of pile body in template of Model Pile, C50 self-compacting concrete is adopted to build cushion cap, concrete is stirred, concrete after stirring will carry out slump consistancy test, treats the after-pouring test base slab of Pass Test requirement.

Three phases described in described step 2 is specific as follows:

1. the Adjustment Tests stage: this stage carries out debugging test by D=60mm single pile and (1 × 2) form clump of piles two kinds of operating modes;

2. horizontal addload experimental stage: carry out the test of multi-state horizontal addload to pile tube list, a clump of piles, operating condition of test is as shown in table 1;

3. horizontal addload and the complementary testing stage: feasibility checking and effect analysis are carried out to the pile foundation level bearing power increase measure proposed by model testing;

Table 1 model testing operating condition design

D represents a diameter, S _athe pile spacing represented.

Described step 3 particular content is as follows:

(1) loading method

Adopt single cycle continuous Loading Method to carry out test loading, every grade of load is estimate ultimate bearing capacity or maximum trial load 1/12 ~ 1/10, and every grade of discharging quantity is 2 times of heap(ed) capacity; Loading every grade and maintain 20min, unload every grade and maintain 10min, is all that 5min survey in interval is read once; Maintaining 30min, interval 10min survey when being discharged to zero load reads once;

Loading classification is as shown in table 2 below:

Table 2 horizontal loading loads grade

Stop loading environment:

1. pile body fractures;

2. horizontal movement is more than 30 ~ 40mm;

3. horizontal movement reaches the horizontal movement permissible value of designing requirement;

4. horizontal loading reaches designing requirement maximum value;

(2) monitoring method

1) pile strain monitoring

The laying mode of pile strain piece collection upper tightly lower sparse, every root Model Pile glues note 20 resistance strain plates;

2) pile body displacement and soil around pile pressure monitoring

Adopt dial gauge monitoring model displacement at pile top; Adopt the distribution situation of earth pressure cell level monitoring load action drag pile peripheral earth soil pressure;

3) horizontal loading controls and monitoring

Measuring instrument is adopted to measure horizontal load, control, and by the coaxial transmission of strict mechanical position assurance load.

Beneficial effect of the present invention is as follows:

This model can not only logarithm value calculate result accuracy verify, and easy and simple to handle, Modulatory character is high, avoid the limitation of field trial.Test model of the present invention and method can not only carry out the model testing of pile foundation list, clump of piles bearer properties, and can study a working property when clump of piles bears vertical load and horizontal loading simultaneously.And model of the present invention can Dismountable, reusable, also can simulate the various indoor model tests such as seepage stability, grouting mechanism, stability of slope.

This test method is carried out in strict accordance with building test pile specification, and content intact, designs rigorous, simple to operate, can simulate the mechanical characteristic of pile tube under horizontal loads comparatively really.This test method gained experimental data condition that is put to the test affects less, and confidence level is higher, adds quality control assurances system in this test method, guarantees to test precision, reduces testing error.

Accompanying drawing explanation

Fig. 1 model groove stereogram

Fig. 2 is model testing loading system sectional drawing.

Fig. 3 is model testing monitoring system and Model Pile sectional drawing.

In figure: 1 model groove, 2 vertical reaction frames, 3 horizontal pneumatic loading systems, 4 vertical pneumatic loading systems, 5 pressure sensors, 6 cushion caps, 7 Model Pile, 8 sands, 9 dial gauges, 10 earth pressure cells, 11 foil gauges.

Detailed description of the invention

Below in conjunction with accompanying drawing, the present invention is described in detail:

As shown in Figure 1-Figure 3, prestressed concrete pipe pile horizontal bearing characteristic test model, comprises a model groove 1, be provided with the cushion cap 6 for carrying Model Pile, and the upper end of Model Pile 7 is embedded in cushion cap 6 in described model groove 1; The lower end of Model Pile 7 is embedded in sand 8; Be provided with above described model groove 1 one be connected with vertical reaction frame 2 and cushion cap is implemented to the vertical pneumatic loading system 4 of vertical force, be provided with connected and to cushion cap carrying out horizontal power horizontal pneumatic loading system 3 inside model groove 1, and be provided with monitoring device in described cushion cap 6, Model Pile 7 and loading system.

Monitoring device is the dial gauge 9 be arranged on cushion cap, the foil gauge 11 be arranged in Model Pile, be arranged at earth pressure cell 10 around Model Pile.

Vertical pneumatic loading system 4 comprises a year Pneumatic jack I, and described Pneumatic jack I is vertically arranged on reaction frame, and described reaction frame is arranged on the top of cushion cap; And be provided with pressure sensor 5I in jack I end;

Horizontal pneumatic loading system 3 comprises a year Pneumatic jack II, and described Pneumatic jack II level is arranged on the inwall of connected model groove, and is provided with pressure sensor 5II in jack II end.

Model groove 1 comprises multiple steel plate framework unit linked together, and is embedded with tempered glass at described frame unit; Described tempered glass middle part is provided with the drain hole communicated with the external world; Described Model Pile is organic glass pile tube, is pasted with resistance strain gage 11 outside it.

According to similitude mechanics principle and prototype condition design, modeling with carry out model testing.The present invention is the simulation carrying out the test of pile tube horizontal bearing characteristic model based on similar second theorem.

One, model testing similar Design:

1, similar second theorem (Buckingham theorem)

The dimension relation that the present invention adopts similar second theorem (Buckingham theorem) to determine between the test model of prototype.Similar second theorem can be expressed as: if establish a physical phenomenon containing n physical quantity, and wherein have m for fundamental physical quantity (its dimension is separate), so this n physical quantity can be expressed as being (n-m) individual similarity criterion π ₁, π ₂..., π _n-mbetween functional relation.By this theorem, that is:

F ₁=(π ₁, π ₂..., π _n-m)=0(formula 1)

In formula: π ₁-the 1 physical quantity, π ₂-the 2 physical quantity, π _n-m-the n-th-m physical quantity, n, m are natural number.

Formula (1) is similarity criterion relational expression or π relational expression, and in formula, π item is similarity criterion.

The effect of Buckingham theorem: for phenomenon similar each other, engraves similarity criterion when corresponding points and correspondence and all keeps same value, so its π relational expression also should be identical.Generally represent prototype and model respectively by subscript " p " and " m ", then π relational expression is respectively:

F ₁=(π _1p, π _2p..., π _{(n-m) p})=0(formula 2)

F ₂=(π _1m, π _2m..., π _{(n-m) m})=0(formula 3)

Wherein: π _1m=π _1p; π _2m=π _2p; π _{(n-m) m}=π _{(n-m) p}(formula 4)

In formula: π _1mfirst physical quantity in-model; π _2msecond physical quantity in-model; π _{(n-m) m}n-th-m physical quantity in-model;

π _1pfirst physical quantity in-prototype; π _2psecond physical quantity in-prototype; π _{(n-m) p}n-th-m physical quantity in-prototype;

F ₁-functional relation 1; f ₂-functional relation 2.

From formula (4), if the result of the test of certain phenomenon is arranged the nondimensional π relational expression shown in an accepted way of doing sth (1), then this relational expression just extends to all other phenomenons similar to it and gets on.And in the process promoted, from formula (4), do not need to list relation equation (no matter whether this equation finds) real between each π item.

2, the derivation of similarity criterion

Institute of the present invention research object is the long stake of elasticity, and load type is horizontal static load, can be similar to modelling according to static(al); And load and displacement are all less, beam on elastic foundation curve differential equation can be selected to be basis, use equational analysis to derive similarity criterion, this method has following advantage:

1. vertebration, physical law the most essential in energy reflecting phenomena, therefore conclusion is reliable;

2. analytic process program is clear and definite, not easily makes mistakes;

3. the level that affects of each factor is clear and definite, is beneficial to deduction, compares and check.

$\mathrm{EI}\frac{d^{4}y}{{\mathrm{dZ}}^4}+b_p{p}_z=\mathrm{EI}\frac{d^{4}y}{{\mathrm{dZ}}^4}+b_p{\mathrm{mZy}}_z=0$ (formula 5)

In formula: E-Young's module of pile (kN/m ²);

I-pile body second moment of area (m ⁴);

B _pthe molded breadth (m) of-pile body;

M-factor of proportionality;

Z-pile body the degree of depth (m);

Y _z-pile body displacement (m);

P _zthe intensity of pressure in-unit area.

Consider physics and fringe conditions similar, and according to dimension principle of homogeneity, can affinity constant be obtained as follows: wherein the first phenomenon (i.e. the actual index of engineering) represents with " ' "; Second phenomenon (i.e. model testing index) is with " " " represent:

$C_E=\frac{E^{\′}}{E^{\′\′}},C_I=\frac{I^{\′}}{I^{\′\′}}={C_L}^4,C_{b_p}=C_z=C_L=\frac{L^{\′}}{L^{\′\′}},C_{y_z}=\frac{{y_z}^{\′}}{{y_z}^{\′\′}},C_m=\frac{m^{\′}}{m^{\′\′}}=1$ (formula 6)

In formula: C _e-modulus of elasticity affinity constant; E '-engineering actual elastic modulus; E ' '-model modulus of elasticity;

C _i-second moment of area affinity constant; I '-engineering actual cross-section moment of inertia; I ' '-model second moment of area;

C _bP-molded breadth affinity constant; The actual geometric constant of L '-engineering; L ' '-model geometric constant;

C _z-pile body degree of depth affinity constant; y _zthe actual pile body displacement of '-engineering; y _z' ' displacement of-model pile body;

C _yZ-pile body displacement affinity constant; M '-engineering actual ratio coefficient; M ' '-model scale coefficient;

C _m-factor of proportionality affinity constant;

C _l-geometric similarity constant;

L-geometric constant.

The differential equation is write out by different phenomenon:

$E^{\′}{I}^{\′}\frac{d^4{y}^{\′}}{{\mathrm{dZ}}^{\′4}}+b_p^{\′}{m}^{\′}{Z}^{\′}{y}_z^{\′}=0$ (formula 7)

$E^{\′\′}{I}^{\′\′}\frac{d^4{y}^{\′\′}}{{\mathrm{dZ}}^{\′\′4}}+b_p^{\′\′}{m}^{\′\′}{Z}^{\′\′}{y}_z^{\′\′}=0$ (formula 8)

B _pthe engineering developed width of '-pile body; b _p' ' model width of-pile body;

The engineering actual grade of Z '-stake; The model depth of Z ' '-pile body;

Carry out similarly transformation, by " " " replacement of parameter " ' " parameter, formula (8) substitutes into by the relation of formula (2), wherein

C _Z=C _L：

$C_E{C}_I\frac{C_L}{{C_L}^4}{E}^{\′}{I}^{\′}\frac{d^4{y}^{\′}}{{\mathrm{dZ}}^{\′4}}+{C_L}^2{C}_m{C}_{y_z}{b_p}^{\′}{m}^{\′}{Z}^{\′}{y_z}^{\′}=0$ (formula 9)

When doing similarity transformation, in order to ensure the uniformity of fundamental differential, each term coefficient must be equal to each other, that is:

$C_E{C}_I\frac{C_L}{{C_L}^4}={C_L}^2{C}_m{C}_{y_z}\⇒\frac{C_E}{C_L{C}_{y_z}}=1$ (formula 10)

Therefore similarity criterion formula (1) can be obtained:

(formula 11)

Its evolution of many physical phenomenons is directly by the impact of initial state, and therefore the present invention is when model testing similar Design, and the primary condition considering test is similar, as described below:

For horizontal loading F ₀and moment M ₀coefficient complete embedding stake:

${\left[\mathrm{EI}\frac{d^2{y}_z}{{\mathrm{dZ}}^2}\right]}_{Z=0}=M_0,{\left[\mathrm{EI}\frac{d^3{y}_z}{{\mathrm{dZ}}^3}\right]}_{Z=0}=F_0$ (formula 12)

Consider that primary condition is similar, in like manner can obtain:

$E\′I\′\frac{d^2{y\′}_z}{{\mathrm{dZ}\′}^2}=M\′$ (formula 13)

$C_E{C}_{I}E\′I\′\frac{C_{y_z}{d}^2{y\′}_z}{{C_L}^2{\mathrm{dZ}\′}^2}=C_{M}M\′$ (formula 14)

In like manner carry out obtaining do similarity transformation:

In formula: C _m-bending affinity constant;

Therefore similarity criterion formula (2) can be obtained:

(formula 15)

$E\′I\′\frac{d^3{y\′}_z}{{\mathrm{dZ}\′}^3}=F\′$ (formula 16)

$C_E{C}_{I}E\′I\′\frac{C_{y_z}{d}^2{y\′}_z}{{C_L}^3{\mathrm{dZ}\′}^2}=C_{F}M\′$ (formula 17)

In like manner carry out obtaining do similarity transformation:

In formula: C _f-load affinity constant;

The theoretical moment of flexure of M-pile body; M '-actual moment of flexure of pile body engineering; M ' '-pile body model moment of flexure;

F-theory load; F '-engineering actual loading; F ' '-model testing load;

Therefore similarity criterion formula (3) can be obtained:

(formula 18)

3, model similarity factor is determined

According to test conditions and content requirement, model testing main phase is as follows like factor design value:

Geometric similarity constant: C _l=C _{l model}/ C _{l is actual}=0.1;

Filling material affinity constant: C _e1=1

Model Pile modulus of elasticity affinity constant is: C _e2=C _{e model}/ C _{e is actual}=0.1;

Displacement affinity constant can be obtained: C by similarity criterion formula (1) _yz=1;

Moment of flexure affinity constant can be obtained: C by similarity criterion formula (2) _m=0.001;

Load affinity constant can be obtained: C by similarity criterion formula (3) _f=0.01.

Two, model testing content design:

1, testing equipment

Testing equipment forms primarily of loading system, model groove and monitoring system.

Loading system comprises loading equipemtn and Loading Control System, and monitoring system comprises monitoring element and data collecting system.

(1) mould Blanking cavity design

According to bulk testing requirement, model groove should meet the test requirements document of list, each operating mode of clump of piles model testing.Consider single, a clump of piles stress and the stress distribution scope under horizontal loads that the functional requirement of model groove and numerical computations determine and tentatively determine form of structure and the size of model groove; Numerical computations display single pile (getting D=100mm operating mode) maximum effect scope under Limiting Level load action is: load direction 16.25m, load vertical direction 5.6m, a clump of piles (gets 2 × 3, pile spacing 3D, D=60mm operating mode) maximum effect scope under Limiting Level load action is: load direction 22.4m, load vertical direction 13.6m;

Consider above-mentioned result of calculation, the test factor such as feasibility, test period, design adopts pin-connected panel model groove capable of being combined, namely according to test dimensional requirement, model groove is designed to size two kinds of forms.Can Confirming model groove size according to the geometric similarity ratio (1:10) chosen, adopt the clump of piles of (1.2m × 2.0m) model groove to single pile and (1 × 2) form to test; The clump of piles of (2.0m × 2.4m) model groove to (1 × 3), (2 × 2) and (2 × 3) form is adopted to test.

Consider the many factors such as content of the test, operation, function, use for reference existing model testing experience and choose iron frame+tempering organic glass formula model groove, model groove top is furnished with lifting and counterforce device, it is 500kN that load is born in the design of reaction frame, utilizes model groove sidewall to provide horizontal reacting force.This model groove is adapted to the model testings such as different size needs, loading form, filling property and Contents for Monitoring, can fully meet model testing demand.

It is 2m × 2.4m × 2m that model groove of the present invention is of a size of length, model groove is surrounded by counter force wall, sidewall, organic glass observation window, model groove top is furnished with reaction frame, driving, the design load that reaction frame can be born is 500kN, the sidewall of model groove as counter force wall, can provide horizontal reacting force.Wherein organic glass is accompanied with preformed hole, can simulate the scale (model) test under different water cut condition.This test model groove have can assembled, be convenient to transport, be convenient to regulate the advantage such as physical dimension.

(2) loading system

Pressurized equipment comprises oil pump, jack.Horizontal thrust is applied by Pneumatic jack, jack range 20cm, and the maximum load that can provide is 300kN, coordinates pressure sensor to carry out the size of control load.

(3) monitoring system

The monitoring system used in test comprises dial gauge (range 50mm), resistance-type earth pressure cell 10(range 0.6MPa), resistance strain plate, pressure sensor.Adopt sound state strain acquirement instrument to gather soil pressure and pile strain data, adopt pressure sensor to carry out Real-Time Monitoring and check and correction to load application.

2, experimental material is chosen

Model testing material mainly comprises: Model Pile, model filler and cushion cap material.

(1) Model Pile material and size are determined

1) determination of Model Pile material

Sum up lot of domestic and foreign pile foundation model testing and selecting some basic principles of material of body of a pile:

A, better can simulate the soft or hard difference of stake soil; B, suitably can simulate the roughness of a Soil Interface;

C, be easy to processing and testing element is set; D, selected materials affordable, draw materials conveniently;

The dimensions of e, selected materials is alternative strong, is beneficial to the control analysis of the factors such as test simulation piles with different footpath, wall thickness.

Sum up existing test experience and found that: lucite tube can reflect the stress deformation characteristic of soil-pile-raft very well, and material homogeneity good, be easy to "one off" production, it is a kind of ideal Model Pile alternative materials, and organic glass modulus of elasticity and pile tube actual elastic modular ratio are about 1:10, i.e. modulus of elasticity affinity constant C _e=0.1, be beneficial to model testing design and data analysis.Therefore model testing selects lucite tube as Model Pile alternative materials.

2) determination of Model Pile physical dimension

According to geometric similarity ratio (1:10) Confirming model stake size.Wherein, according to theory calculate and numerical computations, effective working depth of stake is about 15m(25D) in, consider the factor such as test requirements document and test conditions, Model Pile underground length can reduced scale be 1.5m.

(2) filling material is chosen

For ease of testing the stress deformation rule of enforcement and quality control, better reaction clump of piles structure, model testing sieve gets medium sand (average grain diameter is 0.5 ~ 0.25mm), and, as model filling material, it is consistent with real material, and namely similarity factor is 1.

(3) cushion cap material selection

Limit by operating space in dimension of platform and template, be difficult to when cushion cap is built vibrate.But Model Pile and concrete material differ greatly, two kinds of persons are difficult to when fully not vibrating be closely connected, and can have a strong impact on the compatible deformation of clump of piles horizontal bearing capacity and soil-pile-raft.Therefore, for better simulating the compatible deformation characteristic of soil-pile-raft, in model testing, select C50 self-compacting concrete to build cushion cap, and 7 days intensity reach C40 strength criterion.

3, operating condition of test design

According to research needs, be divided into for three stages implemented this model testing, that is:

1. the Adjustment Tests stage: this stage is debugged, optimizes by D=60mm single pile and (1 × 2) form clump of piles two kinds of operating modes test key contents such as experiment process, safeguard, loading scheme, monitoring systems, to instruct follow-up test;

2. horizontal addload experimental stage: carry out the test of multi-state horizontal addload to pile tube list, a clump of piles, operating condition of test is as shown in table 1;

3. horizontal addload and the complementary testing stage: feasibility checking (operation, method, material, form etc.) and effect analysis are carried out to the pile foundation level bearing power increase measure proposed by model testing.

Table 1 model testing operating condition design

4, loading and Contents for Monitoring design

(1) loading scheme design

This model testing adopts single cycle continuous Loading Method to carry out test loading, specifies: every grade of load is estimate ultimate bearing capacity or maximum trial load 1/12 ~ 1/10 according to " pile foundation engineering handbook ", and every grade of discharging quantity is 2 times of heap(ed) capacity; Loading every grade and maintain 20min, unload every grade and maintain 10min, is all that 5min survey in interval is read once.Maintain 30min, interval 10min survey when being discharged to zero load to read once.According to theoretical calculation method, determine to load classification as shown in table 2.

Table 2 horizontal loading loads grade

Stop loading environment:

1. pile body fractures;

2. horizontal movement is more than 30 ~ 40mm;

3. horizontal movement reaches the horizontal movement permissible value of designing requirement;

4. horizontal loading reaches designing requirement maximum value.

Loading system of the present invention comprises horizontal pneumatic loading system and vertical pneumatic loading system, and load is controlled by pressure sensor.

(2) monitoring plan design

1) pile strain monitoring

According to the bending regularity of distribution, the laying mode of pile strain piece collection upper tightly lower sparse, every pile glues note 20 resistance strain plates.

2) pile body displacement and soil around pile pressure monitoring

Dial gauge (range 50mm) is adopted to monitor displacement at pile top; The distribution situation of pile peripheral earth soil pressure under employing earth pressure cell 10 level monitoring load action.

3) horizontal loading controls and monitoring

For strict level of control loaded value, precision is adopted to be that the measuring instrument of 2N measures it, controls, and by the coaxial transmission of strict mechanical position assurance load.

Three tests prepare

1, the sticky note of pile strain sheet

(1) chip select: first use whether lens examination wire grid is parallel, whether mildew, rust spot, measuring each foil gauge resistance value with digimer, selecting the foil gauge of resistance value difference in ± 0.5 Ω for pasting.

(2) cleaning on measuring point surface: organic glass tube-surface is very smooth, can dip in acetone scrub surfaces by direct cotton ball; Mark the grid line of strain meter again in survey sheet position with marking pen.

(3) paster: foil gauge and wiring terminal are made complete, after foil gauge is pasted on Model Pile grid line according to measurement direction; Then use 502 glue itself and Model Pile to be bondd, at upper cover layer of polyethylene plastic foil as interlayer, with the length direction roll extrusion of finger at strain meter, extrudate piece bubble and unnecessary glue, until strain meter and Model Pile close adhesion.

(4) wiring: twin cable is welded with wiring terminal, and number.

(5) damp-proof treatment: after foil gauge carefully connects the wire and insulaion resistance reaches requirement, adopts AB glue to carry out damp-proof treatment to strain meter immediately.

(6) measuring point protection: at stickup adhesive waterproof tape after using foamed glue to cover.

(7) connect up: for reducing testing element to the impact of experimental data, concentrate after all first horizontal laying of foil gauge survey line is outer to stake soil deformation effect scope again and go between earthward, in lateral extent, serpentine wire mode taked by survey line.

2, Model Pile is buried underground

Model Pile is buried underground in process and is performed in strict accordance with experimental design scheme.

(1) committed step that Model Pile is buried underground is exactly the horizontal range of Controlling model stake and ensures the vertical of pile body.Therefore, test model strictly controls the locus of pile body by the mode that machinery is fixing, and uses spirit level and line pendant to carry out accurate adjustment.

(2) (every layer of 20cm), compacting is successively filled according to quality control requirement, ensure that each layer soil body degree of compaction is close, use homemade large hammer ram to carry out large area sand 8 to tamp, then carry out the compacting of stake week with homemade little hammer ram, in compacting process, damage model stake and survey line should be prevented; Often two-layer banket after choose 3 place's measuring points (piles with different distance, based on loaded segment face) and use core cutter method to carry out the mensuration of degree of compaction, to control filled soils.

(3) earth pressure cell 10 adopts the mode of anti-excavation to bury underground, and the strict installation position (distance stake outward flange 5cm) controlling earth pressure cell 10, ensure that earth pressure cell 10 stress surface is perpendicular to loading direction.After pressure cell has been buried underground, sand 8 should be backfilled and carry out the compacting of same way, to ensure that degree of compaction is with originally identical.

3, the building of cushion cap (only clump of piles test needs)

After Model Pile has been buried underground, start building of cushion cap.According to test requirements document, the connection of Model Pile and cushion cap is highly 5cm, in order to the accuracy tested, first utilizes spirit level to flatten pile peripheral earth, then sets up template, in the middle of this process, position and the direction of strict Control architecture, guarantees pile body heart position wherein.The present invention adopts C50 self-compacting concrete to build cushion cap, and therefore mix proportion design and stirring means are called the committed step of this process.Concrete after stirring will carry out slump consistancy test, can build test base slab after waiting to meet the requirements.

4, monitoring system is installed and is connected

Model has filled installs horizontal addload and displacement monitor afterwards according to designing requirement.Strict control appliance installation position, ensures the coaxial transmission of horizontal loading and effective reading of horizontal movement.

After test model and monitoring device have been installed, pile strain is connected with Acquisition Instrument with Monitoring on Earth Pressure element, and installs signal compensation apparatus and carry out system debug; After system debug success, test can be prepared and load.

Four, test loads and data monitoring

(1) record the initial reading of dial gauge, and detect the service behaviour of monitoring system, balancing run is carried out to monitoring element.

(2) apply two-stage horizontal loading and carry out prestrain, hold after carrying 10min and unload, the initial reading of record load reading instrument and dial gauge.

(3) carry out test according to design loading requirement load and record experimental data; Answer Slow loading during loading, and conscientiously observe pile body shifting situation.

Five, Data Processing Method and foundation

1, stake ground place horizontal movement

In test model of the present invention, two dial gauges are installed more than test pile (cushion cap) ground and carry out Horizontal Displacement measurement, according to the rotational angle theta on stake top under formula (19) calculated level load action _o, then stake can calculate by formula (20) or formula (21) in the horizontal movement of ground place.

(formula 19)

X _o=X _on-L _on× sin θ _o(formula 20)

Or X _o=X _under-L _under× sin θ _o(formula 21)

In formula: θ _othe corner on-stake top;

X _othe place's horizontal movement of-stake ground;

X _on-upper dial gauge is to the horizontal range of pile center's line;

X _under-lower dial gauge is to the horizontal range of pile center's line;

L _on-upper dial gauge is to the vertical distance at ground place;

L _under-lower dial gauge is to the vertical distance at ground place.

2, bending

According to the mechanics of materials about deflection of beam deformation and stress analysis theories, the moment of flexure suffered by the arbitrary cross-section of pile body can calculate by formula (22).

$M=\frac{\mathrm{EI}\·({\mathrm{\ϵ}}_{+}-{\mathrm{\ϵ}}_{-})}{b_0}$ (formula 22)

In formula: b ₀the spacing of-tension and compression strain measuring point;

The moment of inertia of I-stake cross section centering axle;

The flexural modulus of elasticity of E-pile body, all adopts each diameter Model Pile stake flexural modulus measured value when carrying out moment of flexure data analysis;

ε ₊, ε _--to be respectively in each cross section that two measuring point places draw, compressive strain value, namely foil gauge surveys read data.

3, soil pressure against piles

Soil pressure against piles value is obtained according to the calculating formula (23) that Dandong City three reaches single mode earth pressure cell 10 that tester factory produces supporting.

P=a (X+b) (formula 23)

In formula: P-soil pressure force value (kPa);

The strain value of X-earth pressure gauge;

The design factor of a, b-be respectively earth pressure gauge.

Claims (5)

1. the test method of prestressed concrete pipe pile horizontal bearing characteristic test model, is characterized in that, as follows:

Step 1 tests the preparatory stage, comprises the stickup of pile strain sheet, the burying underground of Model Pile, the building of cushion cap;

Step 2 design experiment operating mode, comprises Adjustment Tests stage, horizontal addload experimental stage, horizontal addload and complementary testing stage;

Step 3 determines load mode and the detection scheme of load;

Wherein, the stickup of the pile strain sheet described in step 1 comprises the following steps:

(1) chip select: first whether parallel with lens examination wire grid, whether have mildew, rust spot, measure each foil gauge resistance value with digimer;

(2) cleaning on measuring point surface: direct cotton ball dips in acetone and cleans organic glass pile tube surface; Mark the grid line of strain meter again in survey sheet position with marking pen;

(3) paster: foil gauge is pasted on Model Pile grid line according to measurement direction; Then use glue itself and Model Pile to be bondd, at upper cover layer of polyethylene plastic foil as interlayer, in the length direction roll extrusion of strain meter, extrudate piece bubble and unnecessary glue, until strain meter and Model Pile close adhesion;

(4) wiring: twin cable is connected with the wiring terminal of paster, and numbers;

(5) damp-proof treatment: after foil gauge carefully connects the wire and insulaion resistance reaches requirement, adopts glue to carry out damp-proof treatment to strain meter immediately;

(6) measuring point protection: paste adhesive waterproof tape again after using foamed glue to cover;

(7) connect up: concentrate after all first horizontal laying of foil gauge survey line is outer to stake soil deformation effect scope again and go between earthward, in lateral extent, serpentine wire mode taked by survey line.

2. the test method of prestressed concrete pipe pile horizontal bearing characteristic test model as claimed in claim 1, it is characterized in that, the Model Pile described in step 1 is buried underground and is comprised the following steps:

(1) Model Pile is fixed in the cushion cap of model groove by the mode that machinery is fixing, and uses spirit level and line pendant to carry out the accurate adjustment of level and vertical direction;

(2) successively fill in model groove, tamp sandy soil, often two-layer banket after choose 3 place's measuring points, use core cutter method to carry out the mensuration of degree of compaction, to control filled soils;

(3) earth pressure cell adopts the mode of anti-excavation to bury underground, lays according to distance model stake outward flange 5cm, ensures that earth pressure cell stress surface is perpendicular to loading direction;

(4), after earth pressure cell has been buried underground, backfill sand is also tamped.

3. the test method of prestressed concrete pipe pile horizontal bearing characteristic test model as claimed in claim 1, it is characterized in that, building of the cushion cap described in step 1 comprises the following steps:

Spirit level is first utilized to flatten pile peripheral earth, then cushion cap template is set up, and guarantee the center of pile body in template of Model Pile, C50 self-compacting concrete is adopted to build cushion cap, concrete is stirred, concrete after stirring will carry out slump consistancy test, treats the after-pouring test base slab of Pass Test requirement.

4. the test method of prestressed concrete pipe pile horizontal bearing characteristic test model as claimed in claim 1, it is characterized in that, the three phases in step 2 is specific as follows:

1. the Adjustment Tests stage: this stage carries out debugging test by single pile and a clump of piles two kinds of operating modes;

2. horizontal addload experimental stage: the test of multi-state horizontal addload is carried out to pile tube list, a clump of piles;

3. horizontal addload and the complementary testing stage: feasibility checking is carried out to the pile foundation level bearing power increase measure proposed by model testing.

5. the test method of prestressed concrete pipe pile horizontal bearing characteristic test model as claimed in claim 1, it is characterized in that, described step 3 particular content is as follows:

(1) loading method

Adopt single cycle continuous Loading Method to carry out test loading, every grade of load is estimate ultimate bearing capacity or maximum trial load 1/12 ~ 1/10, and every grade of discharging quantity is 2 times of heap(ed) capacity; Loading every grade and maintain 20min, unload every grade and maintain 10min, is all that 5min survey in interval is read once; Maintaining 30min, interval 10min survey when being discharged to zero load reads once;

Stop loading environment:

1. pile body fractures;

2. horizontal movement is more than 30 ~ 40mm;

3. horizontal movement reaches the horizontal movement permissible value of designing requirement;

4. horizontal loading reaches designing requirement maximum value;

(2) monitoring method

1) pile strain monitoring

The laying mode of pile strain piece collection upper tightly lower sparse, every root Model Pile adhering resistance formula foil gauge;

2) pile body displacement and soil around pile pressure monitoring

Adopt dial gauge monitoring model displacement at pile top; Adopt the distribution situation of earth pressure cell level monitoring load action drag pile peripheral earth soil pressure;

3) horizontal loading controls and monitoring

Measuring instrument is adopted to measure horizontal load, control, and by the coaxial transmission of strict mechanical position assurance load.