This article cites:MT/T593"Test of physical and mechanical properties of artificial frozen soil"Part 2:Soil frost heave test method

1 Scope

This part of MT/T593 specifies the test instruments,equipment,test procedures,and result calculation for artificial frozen soil frost heave testing.

This part applies to the determination of frost heave rate and frost heave force in artificial frozen soil.

2 Normative References

The following documents,in whole or in part,are normatively referenced in this part of MT/T 593 and are indispensable for its application.For dated references,subsequent amendments to,or revisions of,any of these publications do not apply.However,parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the documents indicated below.For undated references,the latest edition of the referenced document applies.MT/T 593.1 Physical and mechanical tests on artificially frozen soil-Part 1:Sampling and specimen preparation methods for artificially frozen soil tests

3 Terms and Definitions

The following terms and definitions apply to this standard.

3.1 Frost Heave Ratio

The ratio of the longitudinal height increase of a specimen to its original height after unidirectional freezing under conditions of no lateral deformation and no longitudinal load.

3.2 Frost Heave Pressure

The axial thrust per unit area generated by a specimen after unidirectional freezing under conditions of no lateral deformation,no longitudinal load,and constraint(no deformation)of the upper and lower end faces.

3.3 Frost Heave Test of Open System

A frost heave test conducted by supplying a constant-temperature water source to one end of the specimen and maintaining a constant negative temperature at the other end.

3.4 Frost Heave Test of Closed System

A frost heave test is conducted where one end of the specimen is kept at a constant ambient temperature without an external water supply,while the other end is kept at a constant negative temperature.

4.Test Instruments and Equipment

4.1 Freeze-Heave Tester:Cold end temperature below-10℃,accuracy 0.2℃.

4.2 Stress and Deformation Testing Elements:Pressure sensor(range 0kN～100kN,accuracy 1%);displacement sensor(axial range 0mm~50mm,accuracy 1%;radial range 0mm～25mm,accuracy 1%),automatic data acquisition system.

4.3 Temperature sensor:Range-40℃to+40℃,accuracy 0.2℃.

4.4 Measuring instruments:Dial indicator,stopwatch,balance,timer,etc.

5 Basic Requirements

5.1 Specimen

5.1.1 Specifications:Cylindrical specimens at room temperature,φ(50 mm~150 mm)×(25 mm~75 mm),height-to-diameter ratio of 0.5.

5.1.2 Accuracy:Dimensional error less than 1.0%,parallelism error of both end faces not greater than 0.5 mm.

5.1.3 Preparation:Proceed according to MT/T 593.1.

5.1.4 Quantity:No less than 3 samples.

5.2 Test environment temperature:(20±2)℃or the original ground temperature of the soil sample.

5.3 All instruments and equipment used in the test should be calibrated and qualified before the test.

6.Test Procedure

6.1 Adjust the temperature of the cold plate in the frost heave apparatus to the required test temperature,with a fluctuation range of±0.2℃.For open system frost heave tests,the constant temperature water source temperature should be adjusted to(20±2)℃or the original ground temperature,with a fluctuation of±0.2℃.

6.2 Frost Heave Rate Test

6.2.1 When the cold plate temperature reaches the test temperature,place the sample in the specified position in the frost heave apparatus and install and adjust the gauge or displacement sensor.For open systems,a constant temperature water source need be connected.

6.2.2 Measure the change in sample height at 1 min,2 min,5 min,10 min,20 min,30 min,1 h,2 h,3 h,6 h,and 12 h(measure the change in sample height every 2 h after 12 h).If it is a closed system freeze-thaw test,continue until the reading remains unchanged for 1 h.If it is an open system freeze-thaw test,continue until the change in sample height is less than or equal to 0.02 mm within 2 h,or until it is automatically recorded by the data acquisition system.

6.3 Freeze-Heave Test

6.3.1 When the cold plate reaches the test temperature,place the sample in the specified position in the freeze-heave tester,install and adjust the gauge or pressure sensor.If it is an open system,a constant temperature water source needs to be connected.

6.3.2 When the specimen no longer exhibits frost heave at a given load level after a 2-hour interval,the specimen has reached stability under that load level.The allowable frost heave should not exceed 0.01 mm.Record the applied balance load,or have it automatically recorded by the data acquisition system.

7 Calculation Results

7.1 Calculation of Freeze Heave Rate

εfh=Δh/h0×100…………………………………………………（1）

Where:

εfh——Freeze-thaw rate of the sample at time t,%;

Δh——Axial deformation of the sample during the time interval from 0 to t,in millimeters(mm);h0——Height of the sample before the test,in millimeters(mm).

7.2 Calculation of frost heave force

σfh=F/A………………………………………………………（2）

Where:

σfh——Frost heave force of the specimen at time t,in megapascals(MPa);

F——Axial load of the specimen at time t,in newtons(N);

A——Cross-sectional area ofthe specimen at time t,in square millimeters(mm2).

7.3 Plot the relationship curves between the frost heave rate and time,and between the frost heave force and time based on the test results.

7.4 For the frost heave rate test or frost heave force test,the average value of the three measured valuesis taken as the test result.The calculated results are entered in Appendix A or Appendix B.If the difference between the maximum and minimum valuesof the frost heave rate or frost heave force of the three samples and the median value all exceed 15%of the median value,the test should be repeated.