CN202133592U

CN202133592U - Direct shear apparatus for frozen soil-structure

Info

Publication number: CN202133592U
Application number: CN201120234102U
Authority: CN
Inventors: 杨平; 陈红斌; 王海波; 何文龙; 赵联桢
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2011-07-05
Filing date: 2011-07-05
Publication date: 2012-02-01
Anticipated expiration: 2021-07-05

Abstract

The utility model relates to a direct shear apparatus for frozen soil-structure, comprising a horizontal pusher, a step motor, a displacement sensor, a vertical pressure dowel bar, a horizontal rolling ball guide rail, an upper shear box, a thermocouple, a lower shear box, a semiconductor refrigeration block, a load sensor, a horizontal end fixing device, a cooling liquid conveying pipe, a low and constant temperature groove, a strain rate controller, a balance weight, a lever end fixing device, a horizontal bearing platform, a level and a weight. The direct shear apparatus for frozen soil-structure is applicable to researching mechanical characteristics among contact surfaces of different materials at low temperature; the apparatus can provide different normal stresses and temperatures to act on the contact surfaces of the materials based on the test demand; when the frozen situation on the contact surfaces of the different materials reaches the corresponding demand, a shear force is applied to the contact surfaces at the selected shear speed till the contact surfaces of a test sample are damaged. The direct shear apparatus for the frozen soil integral structure can be used for measuring a relationship curve between shear force and shear displacement of the contact surfaces of frozen soil-structure.

Description

Frozen soil-structure direct shear apparatus

Technical field

The utility model relates to a kind of frozen soil-structure direct shear apparatus that in frozen soil-structure interface mechanical behavior research, uses.Belong to frozen soil-structure indoor model test Instrument technology field.

Technical background

Direct shear apparatus directly is applied in frozen soil-structure interface mechanical behavior research, and report is not arranged at present as yet.

Summary of the invention

What the utility model proposed is a kind of frozen soil-structure direct shear apparatus; Its purpose is intended to for further furtheing investigate frozen soil-structure interface mechanical characteristic; Set up frozen soil-structure interface

relation curve and correlation parameter, inquire into fundamental strength index, constitutive relation and the Changing Pattern under each factor of frozen soil-structure interface mechanical characteristic.

The technical solution of the utility model: the structure of frozen soil-structure direct shear apparatus is that the output shaft of stepper motor and the gear shaft in the horizontal propeller join, and displacement transducer is installed on the horizontal propeller; The corresponding setting of the signals collecting end of displacement transducer with last shear box, the letter that the signal output part of displacement transducer connects CPU is input end, and the horizontal spherical guide of A is contained on the shear box; The pressure at right angle transmission rod is connected on the horizontal spherical guide; Last shear box and corresponding joining of pushing ram in the horizontal propeller are provided with thermopair between last shear box and down cut box, and the semiconductor refrigerating piece is equipped with in down cut box bottom; The below of down cut box connects the horizontal spherical guide of B; The corresponding setting of load sensor with the down cut box, load sensor is fixed on the horizontal ends stationary installation, and the liquid coolant delivery pipe in the low temperature thermostat bath connects the semiconductor refrigerating piece; The signal controlling end of strain rate controller connects the signal input part of horizontal propeller; The below of horizontal cushion cap and lever end stationary installation fix; Lever and the activity of lever end stationary installation are joined, and the left side topspin of lever connects the counterweight counterweight, and counterweight is hung the right side at lever.

The advantage of the utility model: be applicable to the mechanical characteristic between the different materials surface of contact under the research cryogenic conditions.This instrument can be according to testing requirements; Provide different normal stress and temperature action in the material surface of contact; After the situation of freezing on the different materials surface of contact reaches corresponding requirements; Under selected shear rate, surface of contact is applied shearing force, produce until the sample surface of contact and destroy, measure the relation curve of shear stress and shear displacemant.

Description of drawings

Accompanying drawing 1 is the structural representation of frozen soil-structure direct shear apparatus.

Among the figure 1 is horizontal propeller; The 2nd, stepper motor; The 3rd, displacement transducer; The 4th, the pressure at right angle transmission rod; The 5th, horizontal spherical guide; The 6th, last shear box; The 7th, thermopair; The 8th, the down cut box; The 9th, the semiconductor refrigerating piece; The 10th, load sensor; The 11st, the horizontal ends stationary installation; The 12nd, the liquid coolant delivery pipe; The 13rd, low temperature thermostat bath; The 14th, the strain rate controller; The 15th, the counterweight counterweight; The 16th, the lever end stationary installation; The 17th, horizontal cushion cap; The 18th, lever; The 19th, counterweight.

Embodiment

Contrast accompanying drawing 1, the structure of frozen soil-structure direct shear apparatus is that the output shaft of stepper motor 2 and the gear shaft in the horizontal propeller 1 join, displacement transducer 3 is installed on the horizontal propeller 1; The signals collecting end of displacement transducer 3 and last shear box 6 corresponding settings; The displacement signal of shear box 6 in the collection, the signal output part of displacement transducer 3 connects CPU, and the horizontal spherical guide 5 of A is contained on the shear box 6; Pressure at right angle transmission rod 4 is connected on the horizontal spherical guide 5; Corresponding joining of pushing ram in last shear box 6 and the

horizontal propeller

1,8 in last shear box 6 and down cut box are provided with thermopair 7, and semiconductor refrigerating piece 9 is equipped with in down cut box 8 bottoms; The below of down cut box 8 connects the horizontal spherical guide 5 of B; Load sensor 10 and the 8 corresponding settings of down cut box, load sensor 10 is fixed on horizontal ends stationary installation 11, and the liquid coolant delivery pipe 12 in the low temperature thermostat bath 13 connects semiconductor refrigerating piece 9; The signal controlling end of strain rate controller 14 connects the signal input part of horizontal propeller 1; The below of horizontal cushion cap 17 and lever end stationary installation 16 fix; Lever 18 joins with 16 activities of lever end stationary installation; The left side topspin of lever 18 connects counterweight counterweight 15, and counterweight 19 is hung the right side at lever 18.

Method of application,

Soil sample is located under 105～110 ℃ of temperature oven dry 8 hours; After the oven dry soil sample is ground diffusing and passed through the 0.5mm sieve; Water percentage configuration manipulated soil by former soil sample; To pack into after fully stirring and soak into 24 hours in the polybag as manipulated soil, the difference of the water percentage of manipulated soil and former soil sample water percentage is controlled at ± and 1%; Manipulated soil is divided in 3 layers of rectangular parallelepiped mould of inserting volume 100 * 60 * 40mm, and with the equating of both mold ends face, measure manipulated soil density, the difference of manipulated soil and former soil sample density is controlled at ± 0.01g/cm ³

The prepared sample into the cryogenic remolded as incubators, each according to test plan under constant negative temperature curing 4 hours; remove the sample into the frozen soil - structure direct shear apparatus shear box, the sample surface at a predetermined position the drilling two shallow grooves, groove depth 5mm, the thermocouple into the shallow groove cover compaction repair smooth surface of the sample; the sheet after immersion into the wet cutting Cut box and secure; requirements placed on the upper and lower shear box and filled with insulating material gap between the upper and lower shear box; startup semiconductor cooling block 9, while adjusting weight 19 weight change on the shear box 6, shear cassette 8 different materials contact surface of the normal stress, the contact surface temperature reading, the read frequency of 1 times / min, when the contact surface temperature to meet the design requirements and the temperature in 1 hour when temperature is less than 0.2 ℃ shear test ; collect temperature, pressure, displacement, and its acquisition frequency was adjusted to 1 times / s, the stepper motor starts shear strain increment with constant load test are loaded, and by the strain rate controller 14 controls, when the stress after the peak , (1) to continue to increase until the stress strain displacement stable, (2) to increase the displacement of 2% strain, stop the test; obtained through the acquisition of the pressure change of the displacement amount obtaining shear stress

with shear displacement

of

curve; Machine unloaded, removed from the sample, recorded after the destruction of the contact surface of the sample, and to determine soil moisture stratification, access to soil moisture and surface water in the depth direction of migration.

Embodiment

Contoured cradle size: long 750 * high by 860 * wide 250mm, horizontal cushion cap 17 sizes: long 750 * wide 250mm.Frame bottom is equipped with roller, moves with convenient.

The shear box system is positioned at the middle part of horizontal cushion cap 17, is made up of with down cut box 8 two parts last shear box 6, and particular location is as shown in Figure 1.Insulation material is all adhered in last shear box, the down cut box outside.Last shear box volume is long 120mm * wide 70mm * high 30mm, can change structured material easily, to simulate the various structural planes that possibly run in the engineering field, like concrete, metal etc.The down cut box is used to place soil sample, and mold volumes is for being long 100mm * wide 60mm * high 40mm, and the sample shear area is: 100mm * 60mm.Down cut box 8 bottoms are semiconductor refrigerating pieces 9 of sealing.Shear box system (surface of contact tangential) in the horizontal direction is freely; In the vertical direction (surface of contact normal direction) is not subjected to displacement; The material of model configuration face can be done level (surface of contact tangential) motion, the relative tangential motion of frozen soil and structure on the realization surface of contact under horizontal stepping motor system drives.

Loading system comprises: horizontal thrust device (horizontal propeller 1, stepper motor 2), strain rate controller 14, normal pressure device (pressure at right angle transmission rod 4, counterweight counterweight 15, lever end stationary installation 16, lever 18, counterweight 19) three parts.The horizontal thrust device is positioned at horizontal cushion cap right-hand member, shear box left end; The normal pressure device is positioned at the shear box vertical line position; The strain rate controller can freely be placed.

The horizontal thrust device applies shear load, and its maximum shear stress is 30kN, precision 1.5%; Strain rate controller control shear rate.Shear rate is stepless change, scope 0.01～4.99mm/min, error 5%; Apply the normal direction load through lever normal stress device (existing), class of loading is 12.5kPa, 25kPa, 50kPa, 100kPa, 200kPa.

Refrigeration system: refrigeration adopts semiconductor refrigerating; Semiconductor refrigerating piece 9 is embedded in the cavity of down cut box 8 bottoms, soil sample is carried out the freezing knot of unilateral system, lowest refrigerating temperature-30 ° C through the semiconductor refrigerating piece; Guarantee to realize surface of contact temperature 0～-15 ° C, precision ± 0.1 ° C.Through being embedded in thermopair 7 detected temperatures on soil body surface (the following 5mm in soil sample surface place) and cold-making block surface.

Data acquisition system (DAS) comprises load sensor 10, displacement transducer 3, thermopair 7 and datataker DT80G Acquisition Instrument.Load sensor 10 is positioned at shear box system right side, and displacement transducer 3 is positioned at shear box system left side, and thermopair 7 is positioned at the shear box internal system; The three finally passes to the data that collect in the CPU computing machine through datataker DT80G Acquisition Instrument.Wherein, load sensor synthesis precision 0.5%FS; Nonlinearity erron≤0.5%FS, 30～70 ℃ of serviceability temperature scope ﹣, range 0～30kN.Displacement transducer linearity 0.3%FS, range 0～25mm.

Measurement parameter comprises shear stress, shear displacemant, temperature and shear rate, and shear load, shear displacemant, temperature adopt drawing and pressing type load sensor 8, displacement transducer, thermopair to measure respectively.Through data acquisition system (DAS) relevant data is passed to collection automatically in the computing machine.

Test shows

In the conventional direct shear apparatus shear history; Because shear displacemant increases gradually; The contact area of sample and material block reduces gradually, and the pressure distribution in the surface of contact can change, and causes the error of measurement result; Frozen soil-structure direct shear apparatus soil sample shear area is 100mm * 60mm, and the structural slab area is 120mm * 70mm.Because the strain of sample destruction is less than 0.03 in frozen soil and the structure interface direct shearing test, so in the experimentation, can guarantee that the surface of contact area is constant.

Test is found: when the refrigeration beginning, loading normal stress and refrigeration at once, to reload the surface of contact maximum shear stress that normal stress obtains after beginning a period of time widely different; The former, loads normal stress at once during the refrigeration beginning and more tallies with the actual situation through thinking much larger than the latter; Simultaneously because in the process of refrigerastion; Soil sample surface frozen-heave factor everywhere is inconsistent, can make to be assurance frozen soil and the effective contact area of structure interface by the soil sample surface irregularity.Therefore the final mode that loads normal stress when freezing beginning at once that adopts makes an experiment.

Because soil sample is positioned in the mould that stainless steel processes, the structural slab area is greater than the soil sample shear area simultaneously, and under the normal pressure effect, structural slab has contact with mould possible, and then has disperseed to act on the normal stress on the soil sample shear surface.At first below the down cut box is positioned at mould, locate to carve one the dark groove of 4mm, make that the mould in the vertical direction is freely, simultaneously, make full use of the frost heaving characteristic of frozen soil, make structural slab and mould separating.Relation according to final frozen soil-structure interface sliding frictional force and normal stress can know that pressure is added to specimen surface fully.

The technical indicator that reaches

(1) sample shear area: 100 * 60mm;

(2) maximum normal stress: 400kPa, lever loading structure, the lever ratio of 1:12;

(3) maximum shear stress: 30kN, the precision of exerting oneself: 1.5%;

(4) shear rate: 0.01～4.99mm/min.Step motor drive, stepless change, error 5%;

(5) shear displacemant: 0～25mm;

(6) semiconductor refrigerating piece lowest refrigerating temperature-30 ° C guarantees to realize surface of contact temperature 0～-15 ° C, precision ± 0.1 ° C;

(7) instrument physical dimension: long 750 * high by 860 * wide 250mm.

Claims

1. frozen soil-structure direct shear apparatus is characterized in that the output shaft of stepper motor and the gear shaft in the horizontal propeller join, and displacement transducer is installed on the horizontal propeller; The corresponding setting of the signals collecting end of displacement transducer with last shear box, the letter that the signal output part of displacement transducer connects CPU is input end, and the horizontal spherical guide of A is contained on the shear box; The pressure at right angle transmission rod is connected on the horizontal spherical guide; Last shear box and corresponding joining of pushing ram in the horizontal propeller are provided with thermopair between last shear box and down cut box, and the semiconductor refrigerating piece is equipped with in down cut box bottom; The below of down cut box connects the horizontal spherical guide of B; The corresponding setting of load sensor with the down cut box, load sensor is fixed on the horizontal ends stationary installation, and the liquid coolant delivery pipe in the low temperature thermostat bath connects the semiconductor refrigerating piece; The signal controlling end of strain rate controller connects the signal input part of horizontal propeller; The below of horizontal cushion cap and lever end stationary installation fix; Lever and the activity of lever end stationary installation are joined, and the left side topspin of lever connects the counterweight counterweight, and counterweight is hung the right side at lever.