TCVN 8861 2011 to replace 22TCN 211 2006

Phiên bản tiếng Anh của TCVN 8861: 2011 XÁC ĐỊNH MÔ ĐUN ĐÀN HỒI BẰNG TẤM ÉP CỨNG, thay thế 22TCN 211200, lĩnh vực xây dựng. TCVN 8861: 2011 is composed by Institute of Transport Science and Technology, proposed by Ministry of Transport, verified by Directorate for Standards, Metrology and Quality, and announced by Ministry of Science and Technology.

Flexible Pavement - Determination of Elastic modulus of soils and pavement components using Static Plate Load

Method

HANOI - 2011

TCVN 8861 : 2011

4 Principal 5

5 Devices and Tools 6

6 Conduction 6

7 Showing results 7

8 Test report 8

Appendix A (Reference): Form of Test Report 9

3

TCVN 8861 : 2011

Foreword

TCVN 8861: 2011 is composed by Institute of Transport

Science and Technology, proposed by Ministry of Transport, verified by Directorate for Standards, Metrology and Quality, and announced by Ministry of Science and Technology

1.1 This standard provides regulations on testing procedure to determine elastic modulus of soils and

pavement structure components using static plate load method

1.2 This standard is used for design of pavement structure, inspection and evaluation of elastic modulus of

soils and flexible pavement structures

2 References

The following references are necessary for applying these standards For those with year of issuance, apply the versions stated expressly For references without year of issuance, apply the latest version including amendment thereof (if any)

TCVN 4196–1995, Construction Soils - Soils Laboratory methods of determination of moisture and hygroscopic water amount

22 TCN 346-06* ) , Testing procedure for determination of embankment abd base density with sand cone

method.

3 Terminology and Definitions

This Standard use the following terms and definitions:

3.1 Deflection

Displacement in vertical direction of the surface under the impact of a load placed on such surface

3.2 Rebound deflection

Refers to vertical displacement of the surface at load removal

4 Principle

To place a static plate on the flattened surface, to put a load on the static plate with hydraulic jack and loading system With each level of load, measure to determine rebound deflection under the static plate Based on measured data, to draw a diagram for relationship between pressure and rebound deflection, and to determine elastic modules of the structure below the static plate

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TCVN 8861 : 2011

*) TCN will be converted into TCVN.

5 Devices and Tools

5.1 Loading system: Truck, loading frame or fixing frame to create required counterpressure on the testing

surface Spacing from bearer of the loading system (that is, the wheel in case of truck) to external edge of the static plate is no less than 2.4m

5.2 Hydraulic jack: Hydraulic jack is capable of loading in levels as required, to be equipped with a meter to

determine magnitude of the pressure exerted on the static plate Hydraulic jack is calibrated and to create a pressure force on the static plate with accuracy up to 0.01Mpa

5.3 Static plate: A round shaped steel plate, with adequate hardness and thickness of no less than 25mm To

use a static plate with diameter of 76cm for testing soils, and diameter of 33cm for testing surface of pavement components When using static plate of 76cm diameter, to ensure hardness of the plate, it is necessary to use more 3 intermediate plates with diameter respectively 61cm, 46cm and 33cm to be overlapped concentrically

on 76cm plate to create a pyramid on the testing surface

5.4 Deformation indicator: two deformation indicators with divisions accurate to 0.01mm, measurement range

to 25mm

5.5 Holder for deformation indicator: to be fabricated appropriately to mount deformation indicator measuring

deflection of the static plate under the impact of loading The attachment set must be hard enough and not deformed; horizontal carrying bar to mount indicator allows two deformation indicators symetrically fastened by center of the static plate; distance from footing of deformation indicator holder to the external edge of the static plate or loading truck wheel is at least 1.2m

5.6 Dry and clean sand (passing square sieve 0.6mm and retained on sieve 0.3mm) to flatten the testing

surface

5.7 Level: to check surface flatness before measurement.

6 Conduction

6.1 Preparation of testing surface

6.1.1 To skim and to level the testing surface, do not disturb structure of materials in the testing area To use

fine sand with quantities at least to create a horizontal surface under the static plate

6.1.2 When testing with layers below the pavement, to excavate and remove the upper material layers

Handle with care to avoid destroying structure The excavated hole must have dimensions at least as twice as diameter of the static plate

6.2 Installation of measuring instrument: To place the static plate on the flattened surface, then get the truck

move to measuring position, install loading jack on to the static plate so that center of the jack is the same with that of the static plate To install holder of deformation indicator, making sure that the holder is horizontally

Giá truyền tải

Đồng hồ đo biến dạng Đồng hồ đo biến dạng

Tấm ép Cát đệm

Figure 1 Diagram for measuring device installation

6.3 Testing

6.3.1 Level of loading pressure: at least 4 levels Maximum pressure pmax depends on location of the testing surface: pmax= 0.60 Mpa for pavement; pmax =0.45 Mpa for base courses; pmax =0.25 Mpa for embankment Based on pmax to select intermediate level, selecting subequilateral pressure levels and easy to determine on the jack meter

6.3.2 Pre-loading to stabilize the measuring system: After finishing installation of measuring system, conduct

pre-loading to the maximum pressure pmax and maintain loading in 2 minutes, then remove load and wait until deformation becomes stable

6.3.3 To carry out loading and loading removal corresponding to each pressure level pmax For each level, to

load to the selected value, monitor deformation indicators to wait until deflection becomes stable (deformation speed does not exceed 0.02mm/min), recording measured deflection value when loading (referred to as initial reading) Then remove the load entirely (to the pressure value of Zero) by oil release of the hydraulic jack Do not remove loading suddenly to prevent unstabilizing the measuring system Record measured deflection value after removal (called final reading)

6.3.4 The test determining dry volumetric weight of the material layer in the position that is about 10cm far

from the static load edge with sand cne method according to 22 TCN 346 - 06, taking sample to determine moisture according to TCVN 4196 -1995

7 Showing results

Deformation indicator

Load carrier Deformation indicator

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TCVN 8861 : 2011

7.1 Calcualtion of rebound deflection value: Value of rebound deflection for each pressure level is the

difference between initial reading and final reading

7.2 To draw a chart of relationship betwene rebound deflection and pressure: Baed on pairs of value for

rebound deflection and pressure, to mark these points on the relationship chart, where x-axis indicates rebound deflection To draw a line to display this relationship with least square error method The equation has formula: y’ = ax + b

7.3 To adjust the relationship line of rebound deflection – pressure: Adjustment is made by translational

motion of y’ line to the origin of grid The equation after adjustment is y = ax;

7.4 Elastic modulus is determined with the formulae:



) 1 ( 4

= x x pxDx E

Where:

E Elastic modulus, Mpa;

p Loading pressure on the static plate, Mpa;

ℓ value of rebound deflection determined on the adjusted relationship line of rebound deflection

– pressure, mm;

D diameter of the static plate, m

µ Poisson ratio, taken as 0.30 for pavement structure, 0.25 for base and 0.35 for embankment

soils

8 Test Report

The test report shall cover the following informatioin (refer to Appendix A):

- Name of the works;

- Testing position;

- Testing date;

- Weather conditions;

- Tested material layer;

- Testing depth;

- State of testing surface;

- Moisture of material;

- Dry volumetric weight of the material layer;

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TCVN 8861 : 2011

Appendix A

(For reference)

Form of Test Report

RESULTS OF FIELD TEST FOR ELASTIC MODULUS

WITH STATIC PLATE LOAD METHOD

Standard TCVN 8861:2011

1 The Client:

2 Works:

< Work item>

3 Testing position:

4 Tested material layer:

5 Testing depth:

6 Testing date;

7 Weather conditions;

8 Test results:

Readings on deformation indicator

Pressure

Initial reading Final reading Rebound deflection

Pressure – P (MPa)

After adjustment

Reb oun

d defl ecti

on (m m)

7.1 Testing result Edh

Edh = 177MPa

7.2 Moisture of material sample 17.5%

7.3 Dry volumetric weight of material sample: 1.68 (g/cm 3 )

9 Remark

10 Operators:

Tested by:

Calculated by:Checked by:

The Engineer:

LABORATORY MANAGING AGENCY

(Signed and sealed)

Day…

LABORATORY (LAS-XD, VILAS)

(Signed and sealed)