CN104330474A - Calibration method for rock damage fracture system - Google Patents

Abstract

The invention discloses a calibration method for a rock damage fracture system. The calibration method comprises the following steps: preparing a standard rock test sample with the diameter of 50mm and the height of 100mm from a complete rock block; respectively performing freezing and thawing cycle on the standard rock test sample for zero time, four times, eight times, 12 times and 16 times to obtain five groups of rock test samples with different fracture damages; drying the standard rock test sample, and performing ultrasonic test to obtain longitudinal wave velocities of the five groups of rock test samples; testing the extreme single-axis compressive strength of the five groups of the rock test samples by a rock testing machine; constructing a relation curve of the longitudinal wave velocities and the extreme single-axis compressive strength; and testing the longitudinal wave velocity of the rock to be tested by using ultrasonic waves, thereby obtaining the extreme single-axis compressive strength of to-be-tested rock according to the position on the relation curve. Quick and accurate detection on the dynamic performance of the rock is realized.

Description

A kind of damage of rock fissure system scaling method

Technical field

Belong to fissure rock damage detection technology field, be specifically related to a kind of rock sample damage fissure system scaling method.

Background technology

For engineering rock mass, due to the impact of the Engineering Disturbances such as explosion, loading, excavate and unload, inevitably on protolith basis, produce new crack, these cracks newly-increased because of Engineering Disturbance will make rock be damaged, and cause adverse effect to the mechanical characteristic of rock mass.By test method, quantitatively detect the basis that damage of rock variable is rock damage mechanics analysis and research.

Damage refers to that the microdefect (as micro-crack and space) of material occurs expand and be interconnected under load action, causes the decay of its mechanics parameters, and material is deteriorated gradually and cause the phenomenon of destruction.Visible, the essence of material damage is the expansion of its internal crack system.Based on this prerequisite, carrying out quantitatively characterizing material damage by crack rate then becomes possibility.But due to the restriction of experimental technique level, rock fracture rate is difficult to directly record.

At present, the quantitatively characterizing method of rock fracture rate mainly contains CT scan, Digital Image Processing, mercury intrusion method, nuclear magnetic resonance, sonic test etc.CT scan, image processing techniques can obtain the crack rate on rock limited section, belong to two-dimentional category; Energy spectrum analysis, mercury intrusion method, nuclear magnetic resonance, sonic test technology then can obtain the volume crack rate of rock indirectly.Wherein, ultrasonic investigation all belongs to lossless detection method, multistage, multi-mode continuance test can be carried out to same sample, effectively prevent the error that the sample individual difference that produces because each stage adopts various sample when damaging detection causes, and operation is relatively simple, and be widely applied in Practical Project.

In the ultrasound wave research in damage of rock crack, the initial damage variable that Zhao Mingjie (2000) be not subject to the ultrasonic velocity under loading condition to define rock with rock, and give the method using rock ultrasonic velocity to estimate rock strength; Xu Songlin (2011) have studied rock mass ultrasonic velocity feature under load-bearing condition and Excavation; Li Peng (2013) have studied the method by ultrasonic velocity estimation rock-mass quality.But at present adopt ultrasonic wave measurement technique indirectly to set up longitudinal wave velocity and mechanics parameter more, damage relation between the factors such as number of times, and clearly propose to adopt longitudinal wave velocity sign rock volume crack rate.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, provides a kind of new method of demarcating rock sample volume crack rate, for research engineering Rock Damage crack propagation rule and provide foundation with the correlation analysis of mechanics parameter.

For achieving the above object, adopt technical scheme as follows:

A kind of rock sample damage fissure system scaling method, comprises the following steps:

1) the key rock sample that intact rock is made into diameter 50mm, height 100mm is got;

2) key rock sample is carried out respectively to the Frozen-thawed cycled of 0,4,8,12,16 time, obtain the rock sample of five groups of different cracks damages;

3) by key rock sample drying, obtained the longitudinal wave velocity of five groups of rock samples by ultrasonic investigation, and obtain the limit uniaxial compressive strength of five groups of rock samples by uniaxial compression test;

4) relation curve of longitudinal wave velocity and limit uniaxial compressive strength is set up;

5) utilize supersonic wave test instrument to test the longitudinal wave velocity of rock to be measured, at the correspondence position of above-mentioned longitudinal wave velocity and limit uniaxial compressive strength relation curve, the limit uniaxial compressive strength of rock to be measured can be obtained.

By such scheme, described freezing and thawing test, process is as follows:

1) carried out by sample bleeding saturated, and the sample after saturated is placed in refrigeration system, cooling time is 4 hours, and during refrigeration system work, internal temperature remains on-20 ~-10 DEG C;

2) after freezing end, be immersed in normal-temperature water by sample and thaw, the duration of thawing is no less than 4 hours.

By such scheme, described drying course baking temperature is no more than 105 DEG C, the stopping until quality remains unchanged.

Beneficial effect of the present invention is:

(1) quantification achieving damage of rock crack rate is demarcated;

(2) with rock fracture rate for bridge, establish the relation between rock longitudinal wave velocity and mechanics parameter, achieve the quick detection of rock mechanics parameters.

Accompanying drawing explanation

Fig. 1: the different injury stage limit uniaxial compressive strength of sample and longitudinal wave velocity relation curve.

Embodiment

Following embodiment explains technical scheme of the present invention further, but not as limiting the scope of the invention.

A kind of rock sample damage fissure system calibration process is as follows:

1) the key rock sample that intact rock is made into diameter 50mm, height 100mm is got;

2) key rock sample is carried out respectively to the Frozen-thawed cycled of 0,4,8,12,16 time, obtain the rock sample of five groups of different cracks damages;

3) by key rock sample drying, ultrasonic investigation is utilized to obtain the longitudinal wave velocity of five groups of rock samples; Utilize the limit uniaxial compressive strength of rock test rig five groups of rock samples;

4) relation curve of longitudinal wave velocity and limit uniaxial compressive strength is set up;

5) utilize the longitudinal wave velocity of ultrasonic investigation rock to be measured, the position on corresponding relation curve, obtain the limit uniaxial compressive strength of rock to be measured.

Embodiment

First, fresh schist sillar is made the key rock sample (numbering is respectively 1,2,3,4,5) of diameter 50mm, high 100mm, and this state is defined as original state.According to method described in claims, by sample drying, and the longitudinal wave velocity of test sample.

Freezing and thawing test method: first carried out by sample bleeding saturated, and the sample after saturated is placed in refrigeration system, cooling time is 4 hours, during refrigeration system work, internal temperature remains on-20 ~-10 DEG C.After freezing end, be placed in by sample and fill in the container of water, water temperature is normal temperature, requires that sample is all submerged in below the water surface, and the duration of thawing is no less than 4 hours.

According to above-mentioned freezing and thawing test method, 4,8,12,16 freezing and thawing tests (sample being numbered 1 does not carry out freezing and thawing test) are carried out respectively to the sample being numbered 2,3,4,5.

After freezing and thawing test terminates, by sample drying, test its longitudinal wave velocity.Then said sample is again saturated, and carry out indoor uniaxial test, obtain the limit uniaxial compressive strength of each sample, the results are shown in Table 1.

Table 1 each injury stage sample longitudinal wave velocity and mechanics parameter relation are added up

The different injury stage limit uniaxial compressive strength of sample and longitudinal wave velocity relation curve, with reference to shown in accompanying drawing 1.According to above result, the relational expression between sample limit uniaxial compressive strength and longitudinal wave velocity under different faulted condition can be set up:

$f=35.1864-\frac{6.468}{1+e^{\left(\frac{V-3083.252}{50.257}\right)}}$ (formula 1)

In formula, f represents uniaxial compressive strength, and V represents longitudinal wave velocity.Through type 1, just can be estimated the limit uniaxial compressive strength of rock by rock longitudinal wave velocity.

Claims (3)

1. a rock sample damage fissure system scaling method, is characterized in that comprising the following steps:

1) the key rock sample that intact rock is made into diameter 50mm, height 100mm is got;

2) key rock sample is carried out respectively to the Frozen-thawed cycled of 0,4,8,12,16 time, obtain the rock sample of five groups of different cracks damages;

3) by key rock sample drying, obtained the longitudinal wave velocity of five groups of rock samples by ultrasonic investigation, and obtain the limit uniaxial compressive strength of five groups of rock samples by uniaxial compression test;

4) relation curve of longitudinal wave velocity and limit uniaxial compressive strength is set up;

5) utilize supersonic wave test instrument to test the longitudinal wave velocity of rock to be measured, at the correspondence position of above-mentioned longitudinal wave velocity and limit uniaxial compressive strength relation curve, the limit uniaxial compressive strength of rock to be measured can be obtained.

2. rock sample damage fissure system scaling method as claimed in claim 1, it is characterized in that described freezing and thawing test, process is as follows:

1) carried out by sample bleeding saturated, and the sample after saturated is placed in refrigeration system, cooling time is 4 hours, and during refrigeration system work, internal temperature remains on-20 ~-10 DEG C;

2) after freezing end, be immersed in normal-temperature water by sample and thaw, the duration of thawing is no less than 4 hours.

3. rock sample damage fissure system scaling method as claimed in claim 1, is characterized in that described drying course baking temperature is no more than 105 DEG C, the stopping until quality remains unchanged.