CN102221501A - Device and method for measuring mechanical properties of rocks - Google Patents

Abstract

The invention relates to a device and a method for measurement, in particular to the method for calculating the mechanical properties of a series of rock sample materials by recording relationships between testing forces/loads and indentation depths/displacements at different moments. The device comprises a rack, a DC motor, displacement measurers, a rigid flat-bottom pressure head and a sample fixing station, wherein the rack is divided into two layers; the upper layer of the rack is provided with the DC motor of which one end is connected with the rigid flat-bottom pressure head; the displacement measurers are distributed about the rigid flat-bottom pressure head; and the sample fixing station is fixed on a base of the lower layer of the rack. The reliability and effectiveness of the method can be evaluated by comparing basic rock mechanical property measurement results with those obtained by other conventional testing means. In addition, compared with conventional mechanical test methods such as single-pressing tests, single-pulling tests, triaxial compression tests and the like in laboratories, the method has the advantages of short test process, simplicity and convenience of operation, low requirements on samples, economy and the like.

Description

A kind of rock mechanics characteristic detecting apparatus and assay method

Technical field

The present invention relates to a kind of determinator and assay method, specifically relate to the test power (load) in a kind of different moment of passing through to write down and the relation between the depth of cup (displacement), the method for inquiring into the mechanical characteristic of a series of rock sample materials.

Background technology

In modern Geotechnical Engineering, rock mechanics properties is the very important technical parameter of a class.For example, usually can run into the rock stratum drillability and how to select this two classes problem of drill bit according to the mechanical property of rock stratum in field of petroleum exploitation.Current, using more method is the physical characteristics (as acoustic velocity, porosity etc.) of in-site measurement rock.By database, determine the mechanical characteristic of the rock mass of studying with reference to different rock physical properties of setting up and mechanical characteristic relation.Yet, these site tests and research complicated operation, experimental period is long, economic consumption greatly.Therefore, press for a kind of new method of determining the rock mechanics characteristic fast and effectively of research.Under this background, developed a kind of new rock mechanics characteristic measurement method, invented a kind of new rock mechanics characteristic test system that adopts the impression test technology.This method is based on the impression theory of flat pressure head, by the stress field that produces in the impression process is carried out theory and numerical analysis, analyze load-displacement curve, the mechanical characteristic of material, the geometric configuration of test head, size, and then calculate the basic mechanical characteristic of rock.

Summary of the invention

The objective of the invention is to overcome the complicated operation that exists in the prior art, experimental period is long, problems such as economic consumption is big, the test power (load) in a kind of different moment of passing through to record and the relation between the depth of cup (displacement) are provided, the method for inquiring into the mechanical characteristic of a series of rock sample materials.This method is applicable to different sizes, different types of sillar.

The present invention adopts following technical scheme:

Rock mechanics characteristic detecting apparatus provided by the invention comprises frame, direct current generator, deviation meter, the flat pressure head of rigidity, sample fixed station; Described frame is divided into two-layer, and direct current generator is arranged on the upper strata of frame, and motor one end connects the flat pressure head of rigidity, arranges deviation meter around the flat pressure head of rigidity, and the sample fixed station is fixed on the base of frame lower floor frame.

Rock mechanics characteristic detecting apparatus of the present invention, the flat pressure head of described rigidity is made by tungsten carbide material.

The assay method of rock mechanics characteristic detecting apparatus of the present invention, assay method is as follows:

1), according to the test rock sample sample, select the suitable flat pressure head of rigidity to be installed on the direct current generator;

2), the system stiffness of the flat pressure head of rigidity in the calibration above-mentioned steps 1;

3), the rock sample with test grinds smooth, smooth;

4), the rock sample after the processing in the above-mentioned steps 4 is placed on the sample fixed station startup sample fixed station, the displacement data of the flat pressure head of rigidity under the corresponding load action of deviation meter opening entry;

5), according to the measurement in the cloth step 4, draw out the relation curve of load-displacement, the form of analytic curve obtains the mechanics parameters of rock sample.

Beneficial effect

This assay method is applicable to the sillars of different sizes, as landwaste etc.The rock kind of measuring has a lot, as sandstone, ls, tonstein etc.The result of the mensuration of rock basic mechanical characteristic and other conventionally test means compare, and can assess the reliability and the validity of this method.In addition, with respect to traditional laboratory mechanical test, as single press test, singly draw test, triaxial compression test etc., this method have process of the test short, simple to operation, to low, the economic dispatch advantage of sample requirement.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the indentation test load-displacement curve figure of the embodiment of the invention 1;

Fig. 3 is the indentation test load-displacement curve figure of the embodiment of the invention 2;

1 is frame among the figure, the 2nd, and direct current generator, the 3rd, deviation meter, the 4th, the flat pressure head of rigidity, the 5th, sample fixed station, the 6th, rock sample.

Embodiment

The present invention is described in more detail below in conjunction with accompanying drawing:

As shown in Figure 1: a kind of rock mechanics characteristic detecting apparatus comprises frame 1, direct current generator 2, deviation meter 3, the flat pressure head 4 of rigidity, sample fixed station 5.

Described frame 1 is divided into two-layer, and direct current generator 2 is arranged on the upper strata of frame 1, and motor 2 one ends connect the flat pressure head 4 of rigidity, arranges deviation meter 3 around the flat pressure head 4 of rigidity, and sample fixed station 5 is fixed on the base of frame 1 lower floor's frame.The flat pressure head of described rigidity 4 is made by tungsten carbide material.

Assay method of the present invention is as follows:

1), according to the test rock sample sample, select the flat pressure head 4 of suitable rigidity to be installed on the direct current generator (2);

2), the system stiffness of the flat pressure head 2 of rigidity in the calibration above-mentioned steps 1;

3), the rock sample with test grinds smooth, smooth;

4), the rock sample after the processing in the above-mentioned steps 4 is placed on the sample fixed station 5 startup sample fixed station 5, the displacement data of the flat pressure head 4 of rigidity under the corresponding load action of deviation meter 3 opening entries;

5), according to the measurement in the cloth step 4, draw out the relation curve of load-displacement, the form of analytic curve obtains the mechanics parameters of rock sample

Simply press dark h (displacement of pressing head just) to represent the relational expression of stiffness K for one with load power F peace base pressure head:

$K=\mathrm{dF}/\mathrm{dh}=2\sqrt{A/\mathrm{\π}}{E}_r={2\mathrm{aE}}_r={\mathrm{DE}}_r---\left(1\right)$

A is surface of contact area (for flat pressure head, A remains unchanged in the process of the test, is the sectional area of pressure head) in the formula, and a is the radius of pressure head, and D is the diameter of pressure head, i.e. A=π a ²=π D ²/ 4, consider the mechanical property of pressure head itself, define a contact modulus E _r, be expressed as:

$1/E_r=(1-v^2)/E+(1-v_i^2)/E_i---\left(2\right)$

E in the formula _i, v _iBe respectively the Young's modulus of elasticity and the Poisson ratio of pressure head, E and v are the Young's modulus of elasticity and the Poisson ratios of material.

When analyzing data, consider the distortion of machine and pressure head itself, before experiment, need calibration.The calibration testing test can be modeled as two springs that are cascaded representing instrument and contact respectively.Like this, overall flexibility (C _t) be the flexibility (C of instrument _s) and contact flexibility (C _m) summation:

C _t＝C _s+C _m (3)

Adopt the rigidity symbol, can be expressed as:

1/K _d＝1/K+1/K _m (4)

K in the formula _dBe global stiffness, can determine by the slope of unloading curve initial stage linearity range; K _mBe the rigidity of instrument; K is the rigidity of contact, calculates by formula (1).Then formula (4) can be write as again:

$1/K_d=(1-v^2)/\left(\mathrm{DE}\right)+(1-v_i^2)/\left({\mathrm{DE}}_i\right)+1/K_m---\left(5\right)$

Parameter K of back two usefulness in the wushu (5) _i(being called system stiffness) replaces, and promptly has:

1/K _d＝(1-v ²)/(DE)+1/K _i (6)

In the formula $1/K_i=1/K_m+(1-{\mathrm{\υ}}_i^2)/\left({\mathrm{DE}}_i\right).$

By the above-mentioned formula of formula (6) as can be seen, if the Elasticity parameter (elastic modulus and Poisson ratio) of material of test is known, system stiffness K then _iBe easy to determine by calibration test.The selection of calibration materials is also very important.In general, good calibration materials hardness is very big and elastic modulus is relatively low and the height isotropy.Usually the calibration materials of recommending to use is a quartz material.But because its price is higher, we have adopted aluminum alloy materials (Al7049).The basic mechanical parameter of this material is: E=71.4GPa, v=0.33, elastic buckling limit σ _y=655MPa.

LVDT is a linear variable difference transformer, is a kind of displacement transducer.The mensuration system comprises compositions such as the flat pressure head of rigidity, direct current generator, displacement measurement system LVDT, framework, sample fixed station, vertical rigidity main shaft.

Described flat cylindrical pressure head is contained in and is used to transmit under the vertical rigidity main shaft of pressure, and diameter range is that 0.5mm is to 2mm.

Described direct current generator is used for load application, and the highest 2kN that is loaded as is accurate to 1N, and loading velocity is shown 1 * 10 with offset table ^-3～2mm/min.

Displacement transducer LVDT in the described displacement measurement system, greatest measurement is 2mm, is accurate to 1 μ m.

Described displacement measurement system includes four LVDT, arranges on four sides along the rigidity main shaft, measures from sample bench to the displacement the central shaft position that connects LVDT.Sample has also been eliminated in the employing of four displacement sensor LVDT because the local error that moves or tilt to cause among a small circle.

Described pressure head is cylindrical flat pressure head, and the employing tungsten carbide is a material, has guaranteed the requirement of low distortion and high rigidity.

Embodiment 1:

1) this example is at first calibrated the system stiffness of different tack diameter pressure heads for measuring the elastic modulus of sandstone, adopts aluminum alloy materials (Al7049) as this mechanics parameter of calibration materials to be: E=71.4GPa, v=0.33, elastic buckling limit σ _y=655MPa does not calibrate bit diameter and is 0.5,1, the system stiffness during 2mm

2) because the particle of sandstone is thicker, be the flat cylindrical pressure head of 2m so select diameter for use.

3) get 3 groups of sandstone samples, with 5 be one group, the about 10mm of rock sample thickness, the about 40mm of diameter.Different rock samples are distinguished by numeral number, have represented different sampling spots.Top and bottom are all ground smooth, smooth with machine.Rock sample is not on the same group distinguished by numeral number, has represented different sampling spots.

4) rock sample is placed on the sample fixed station, starts direct current generator and begin to load, loading speed represents that with displacement simultaneous displacement measuring system LVDT writes down the displacement of pressing head under the corresponding load action.

5) according to measurement, draw out the relation curve of load-displacement, detail record sees Table 1.

6) form of curve in the analysis chart 2, the straight-line segment slope that the stage is carried in unloading is K _d, (for sandstone and ls, supposing v=0.3) calculates the mechanics parameters of rock sample according to above-mentioned formula (6).

Embodiment 2:

1) this example as example 1, is at first calibrated the system stiffness of different tack diameter pressure heads for measuring the elastic modulus of ls with known mechanical characteristic material such as aluminium alloy.

2) because the particle of ls is thicker, be the flat cylindrical pressure head of 0.5m so select diameter for use.

3) get 3 groups of ls rock samples, with 5 be one group, the about 10mm of rock sample thickness, the about 40mm of diameter.Different rock samples are distinguished by numeral number, have represented different sampling spots.Top and bottom are all ground smooth, smooth with machine.Rock sample is not on the same group distinguished by numeral number, has represented different sampling spots.

4) rock sample is placed on the sample fixed station, starts direct current generator and begin to load, loading speed represents that with displacement simultaneous displacement measuring system LVDT writes down the displacement of pressing head under the corresponding load action.

5) according to measurement, draw out the relation curve of load-displacement, detail record sees Table 2.

6) form of curve in the analysis chart 3, the straight-line segment slope of getting load phase is K _d, (for sandstone and ls, supposing v=0.3) calculates the mechanics parameters of rock sample according to above-mentioned formula (6).

Claims (3)

1. a rock mechanics characteristic detecting apparatus is characterized in that: comprise frame (1), direct current generator (2), deviation meter (3), the flat pressure head of rigidity (4), sample fixed station (5); Described frame (1) is divided into two-layer, direct current generator (2) is arranged on the upper strata of frame (1), motor (2) one ends connect the flat pressure head of rigidity (4), arrange that deviation meter (3), sample fixed station (5) are fixed on the base of frame (1) lower floor frame around the flat pressure head of rigidity (4).

2. rock mechanics characteristic detecting apparatus according to claim 1 is characterized in that: the flat pressure head of described rigidity (4) is made by tungsten carbide material.

3. utilize the assay method of the described rock mechanics characteristic detecting apparatus of claim 1, it is characterized in that: assay method is as follows:

1), according to the test rock sample sample, select the suitable flat pressure head of rigidity (4) to be installed on the direct current generator (2);

2), the system stiffness of the flat pressure head of rigidity (2) in the calibration above-mentioned steps 1;

3), the rock sample with test grinds smooth, smooth;

4), the rock sample after the processing in the above-mentioned steps 4 is placed on the sample fixed station (5) startup sample fixed station (5), the displacement data of the flat pressure head of rigidity (4) under the corresponding load action of deviation meter (3) opening entry;

5), according to the measurement in the cloth step 4, draw out the relation curve of load-displacement, the form of analytic curve obtains the mechanics parameters of rock sample.

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