承压板实验法-6.1

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6 Deformation Test of theRock Mass

6.1Bearing PlateMethod Test

6.1.1The test can be divided into rigid bearing plate method and flexible bearing plate method.The former method is applicable to all types of rock mass,whilst the later method is applicable to completeand comparatively complete rock mass and can be further divided into two-pillow method, four-pillow method, ring-pillow method and central-hole method.

6.1.2Tests shall be carried out in theadit whilst in special case they can also be carried out at open area or in a shaft.

6.1.3Tests shall be exercised as follows:

1 Loading direction of the specimenshall be at the same direction ofeffective loading

directionof engineering rock mass.

2Bearing areas shall not be less than 2000cm2.

3 The spacing from the verge of the specimen to that of the aditshall be 1.5 times greater than the length ofdiameter or the side length of the bearing plate. The spacing from the verge of the specimen to the mouth ofadit or to the heading face shall be 2 times greater than the length of diameter or the side length of the bearing plate.The spacing from the verge of the specimen to the open side shall be 6 times greater than the length of diameter or the side length of the bearing plate. And the spacing distances between specimens shall be 3 times greater than the length of diameter or the side length of the bearing plate.

4 Lithology of the rock mass 3 times of the length of diameter or the side length of the bearing plate under the specimen shall be homogeneous.

5 The specimen surface shall be cleaned and free from disturbance of rock mass.

6Thebearing face shall be leveled, and grinded by grinding wheel whilst asperities of it shall less than 1% of the length of diameter or the side length of the bearing plate. The rock surface 1.5 times of the bearing plate beyond the bearing face shall be leveled and without loosening rock.

7 Drilling for core sampling shall be conducted at the center of the specimen prior tothe commencement of test forcentral-hole method. The drilling depth shall not be less than 6 times the diameter of the bearing plate, and shall be suitable to the multiple point displacement equipment.

6.1.4Geological logging prior to the test shall conform to Appendix E to this specifications book.

6.1.5Major testing apparatus applied in the test include

-Hydraulic jack;

-Hydraulic pillow;

-Pressure measuring pillow;

-Hydraulic pump;

-Piping;

-Hydraulic gage;

-Pressure-maintaining devices;

-Rigid bearing plate;

-Steel base plate;

- Load transfer box;

- Load transfer column;

-Wedge spacer;

-Reaction mechanism;

-Support of gauges;

-Measurement devices;

-Stands for measurement devices;

-Multiple point displacement equipment;

-Survey points;

-Drilling machine and auxiliary equipment.

6.1.6The pressurization system and the actuating system for the rigid bearing plate method shall be installed as follows：

1Wash the specimen surface and pour a layer of mortar. Then the rigid bearing plateshall be placed and the surplusmortar shall be extrudedout to ensure the bearing plate parallel to the specimen surface.The thickness of the mortar shall 1% less than the diameter or the side length of the bearing plate.

2 The rigid bearing plate shall befree frommovingprior to the completeness of the test.

3The rigid bearing plate shall meet the requirementforstiffness, and thus the thickness for a single rigid bearing plate shall not less than 6cm. When the requirement cannot be satisfied, superimposed steel or load transfer box can be used to improve the stiffness.

4 Install the jack, steel base plate, load transfer column and steel base plate on the bearing plate in sequentially, whilst fill mortar and install the reaction mechanismbetween the steel base plate and the rock mass.( Figure 6.1.6)

5Impose the contact pressure to ensure the system connection tightly.

6The stiffness and strength for whole system shall besufficient, whilst the centroids of all the componentsshall be kept on the same axis of loading direction.

Figure 6.1.6 Installationdiagram fortest of rigid bearing plate method

(a)Loadingat vertical direction; (b) Loading at horizontal direction

1—mortar; 2, 4, 10—steel spacer plates; 3—load transfer column; 5—hydraulic gage; 6—hydraulic jack; 7—piping; 8—stands for measurement devices;9—support of gauges;11—Rigid bearing plate; 12—survey points; 13—measurement devices; 14—rollers; 15—supporting seat; 16—wooden pole; 17—hydraulic pump; 18—wooden pad; 19—wooden beam

6.1.8The deformation measuring system shall be installed as follows：

1Install supportof gaugesat both sides of the bearing plate, and the support of gauges should meet the requirements for stiffness.The supporting pointshall be arranged4 times the length of diameter or the side length of the bearing plateaway from the centroid of the specimen.

2 Fourmeasurement gauges shall be symmetrically installed onto the bearing plateregarding the test ofrigid bearing plate method.

3 One measurement gauge shall be installed onto the centroid of the bearing plate regarding the test of flexible bearing plate method.One measurement gauge shall be installed onto the centroid of the bearing plate regarding the tests of two-pillow method and four-pillow method,and two or four measurementgauges shall be furtherinstalled atthe center lines of gap of the hydraulic pillow, and the distances from the centroid to each measurement gaugeshall be 0.25 timegap length. (Figure

6.1.8)

Figure 6.1.8Installation diagram for test of flexible bearing plate method

(a)Two-pillow method; (b) Four-pillow method

4 Certain measurement gauges shall be symmetrically arranged at the outside of the bearing plate along or perpendicular to the adit axis direction through the centroid of the plate.

5 The stands for measurement devices shall meet the requirement for stiffness.