CN104359772B - The normal stress threshold value determination method of rock mass discontinuity peak value angle of friction - Google Patents

Abstract

The normal stress threshold value determination method of a kind of rock mass discontinuity peak value angle of friction, comprises the following steps: 1) rating test direction；2) Selection experiment structural plane and sample quantities；3) roughness value of each structural plane is measured4) the peak value angle of friction φ of structural plane under every grade of normal stress is obtained by direct shear test_1i、φ_2i, each structural fece sample is carried out the direct shear test under the conditions of different normal stress；5) the relative error magnitudes δ of engineering rock structural face is determined；6) normal stress threshold value σ of each structural plane peak value angle of friction is determined_i；7) the final normal direction stress threshold of this group structural plane peak value angle of friction is determined: when this group m structural plane peak value angle of friction normal stress threshold value σ_iExtreme difference less than meansigma methods 15% time, take normal stress threshold value σ of m structural plane peak value angle of friction_iMeansigma methodsNormal stress threshold value as this group structural plane peak value angle of friction.The principle of the invention is clear and definite, easy to operate, low cost, using effect are good, it is simple to carry out engineer applied.

Description

The normal stress threshold value determination method of rock mass discontinuity peak value angle of friction

Technical field

The invention belongs to field of engineering technology, the normal direction relating to rock mass discontinuity peak value angle of friction should Power threshold value determination method, it is adaptable to water conservancy, traffic, mining, geology, nuclear waste disposal, The correlation engineering such as oil have the normal stress of the rock mass discontinuity peak value angle of friction of stress effect Threshold value determination method.

Background technology

Before the present invention makes, the most still there is no the normal stress threshold of rock mass discontinuity angle of friction The determination method of value.Rock mass discontinuity peak value angle of friction is engineering rock structural face Stability Assessment Important parameter.Joint straight shear test under the conditions of different normal stresses shows, structural plane peak value Angle of friction presents nonlinear attenuation with the increase of normal stress, as shown in Figure 1.

Being shown by the result of the test of Fig. 1, when normal stress is less, peak value angle of friction is bigger； When normal stress is bigger, peak value angle of friction diminishes；When normal stress increases to certain value, peak Value angle of friction substantially tends towards stability value, at this moment disclosure satisfy that Practical Project rock mass discontinuity peak value The minimum normal stress that angle of friction relative error requires is referred to as normal stress threshold value, peak value angle of friction The stress effect of rock mass discontinuity angle of friction it is referred to as with the effect of normal stress change.Due to engineering The normal stress of rock mass is the biggest, therefore, needs employing to tend towards stability in actual rock mass engineering project Structural plane peak value angle of friction.But the normal direction used due to direct shear test under normal test conditions Stress loading is limited in scope, especially for large-scale structure face, due to the Normal stress applied Excessive, the conventional loading equipemtn of laboratory is difficult to meet loading normal stress requirement, therefore can not obtain The normal stress threshold value required to engineering rock structural face peak value angle of friction ultimate value, and multistage High normal stress direct shear test is expensive, the cycle is long, it is difficult to meet engine request.Therefore, as What determines that structural plane peak value angle of friction normal stress threshold value is urgently to solve in engineering quickly and easily Key issue certainly.

Summary of the invention

In order to solve prior art cannot determine the normal stress of rock mass discontinuity peak value angle of friction The deficiency of threshold value, the present invention provides a kind of definite principle, easy to operate, low cost, use effect The best, it is simple to carry out the normal stress threshold value of the rock mass discontinuity peak value angle of friction of engineer applied Determine method.

In order to solve the technical scheme that above-mentioned technical problem is proposed:

A kind of normal stress threshold value determination method of rock mass discontinuity peak value angle of friction, described really The method of determining comprises the following steps:

1) rating test direction: rating test direction on selected engineering rock structural face；

2) Selection experiment structural plane and sample quantities: according to the scale of engineering rock structural face, Selected one group of structural plane size not changed with dimensional effect, and the structural plane of selected size is entered Row sampling processing；This group structural fece sample number be m, m be the natural number not less than 3；

3) the roughness value JRC of i-th structural plane in this group m structural plane is measured_i。 I-th structural plane is rule according to certain intervals, and measures the roughness of every scribing position Coefficient；Then the roughness value to surveys line all on this structural plane is averaged and is obtained this structure Face JRC_i；

4) by the peak of i-th structural plane under the conditions of the direct shear test acquisition low normal stress of two-stage Value angle of friction φ_1i、φ_2i.I-th structural fece sample in this group is carried out two-stage low normal stress bar Direct shear test under part, normal stress is taken as σ respectively_1i=0.25MPa, σ_2i=0.5MPa, can obtain Obtain the structural plane peak shear strength τ under the conditions of the low normal stress of two-stage_1iAnd τ_2i, then according to public affairs FormulaObtain this structural plane structural plane peak value under the conditions of the low normal stress of two-stage Angle of friction ${\mathrm{\φ}}_{1i}=\arctan \left(\frac{{\mathrm{\τ}}_{1i}}{{\mathrm{\σ}}_{1i}}\right),{\mathrm{\φ}2}_i=\arctan \left(\frac{{\mathrm{\τ}}_{2i}}{{\mathrm{\σ}}_{2i}}\right);$

5) the relative error magnitudes δ of engineering rock structural face peak value angle of friction is determined；

6) normal stress threshold value σ of i-th structural plane peak value angle of friction is determined_i；Should by normal direction The rate of change formula of powerObtain the normal stress threshold value of i-th structural plane peak value angle of friction σ_i≥2.3·JRC_i/(g_2iδ), wherein: $g_{\mathrm{ni}}=\frac{{\mathrm{\φ}}_{\mathrm{ni}}-{\mathrm{\φ}}_{\mathrm{ni}-1}}{{\mathrm{\σ}}_{\mathrm{ni}}-{\mathrm{\σ}}_{\mathrm{ni}-1}},g_{2i}=\frac{{\mathrm{\φ}}_{2i}-{\mathrm{\φ}}_{1i}}{{\mathrm{\σ}}_{2i}-{\mathrm{\σ}}_{1i}},$ N in subscript is N-th grade of normal stress, i is the i-th structural plane in this group m structural plane, and 2 is the second level Normal stress；g_niFor the structural plane peak value friction under n-th grade of normal stress of the i-th structural plane The rate of change at angle, g_2iRub for i-th structural plane structural plane peak value under the 2nd grade of normal stress Wipe the rate of change at angle；

7) the average normal direction stress threshold of this group structural plane peak value angle of friction is determinedWhen this group M structural plane peak value angle of friction normal stress threshold value σ_iExtreme difference less than meansigma methods 15% time, institute State the difference that extreme difference is maximum and minima, take the normal stress of m structural plane peak value angle of friction Threshold value σ_iMeansigma methodsNormal stress threshold value as this group structural plane peak value angle of friction.

Further, described step 7) in, when the normal stress of m structural plane peak value angle of friction Threshold value extreme difference σ_iDuring more than meansigma methods 15%, the structural fece sample being stepped up same size is carried out Direct shear test, until wherein there being extreme difference the putting down less than m selected sample of m sample All normal stress threshold value 15% time, take selected m sample peak value angle of friction normal stress threshold The meansigma methods of value is as the final normal direction stress threshold of this group structural plane peak value angle of friction.

The present invention compared with prior art, has the advantage that and is mainly reflected in: rock mass structure The normal stress threshold value determination method of face peak value angle of friction have definite principle, simple to operate, Low cost, using effect are good, have bigger implementary value and economic results in society.

Accompanying drawing explanation

Fig. 1 is the stress effect threshold figure of structural plane peak value angle of friction.

Detailed description of the invention

The present invention will be further described below.

With reference to Fig. 1, the determination side of the normal stress threshold value of a kind of rock mass discontinuity peak value angle of friction Method, comprises the following steps:

1) rating test direction: rating test direction on selected engineering rock structural face；

2) Selection experiment structural plane and sample quantities: according to the scale of engineering rock structural face, Selected one group with the structural plane size of dimensional effect change, (usual scope does not exists Between 300mm × 300mm-1000mm × 1000mm), and the structural plane of selected size is carried out Sampling processing；This group structural fece sample number be m, m be the natural number not less than 3；

3) the roughness value JRC of the i-th structural plane of m structural plane in this group is measured_i.? Rule according to certain intervals on i-th structural plane, and measure the roughness system of every scribing position Number；Then the roughness value to surveys line all on this structural plane is averaged and is obtained this structural plane JRC_i；

4) by the peak of i-th structural plane under the conditions of the direct shear test acquisition low normal stress of two-stage Value angle of friction φ_1i、φ_2i.I-th structural fece sample in this group is carried out two-stage low normal stress bar Direct shear test under part, normal stress is respectively σ_1i=0.25MPa, σ_2i=0.5MPa, can obtain Structural plane peak shear strength τ under the conditions of the low normal stress of two-stage_1iAnd τ_2i, then according to formulaObtain this structural plane structural plane peak value under the conditions of the low normal stress of two-stage to rub Wipe angle ${\mathrm{\φ}}_{1i}=\arctan \left(\frac{{\mathrm{\τ}}_{1i}}{{\mathrm{\σ}}_{1i}}\right),{\mathrm{\φ}2}_i=\arctan \left(\frac{{\mathrm{\τ}}_{2i}}{{\mathrm{\σ}}_{2i}}\right);$

5) the relative error magnitudes δ of engineering rock structural face peak value angle of friction is determined；

6) normal stress threshold value σ of i-th structural plane peak value angle of friction is determined_i, should by normal direction The rate of change formula of powerObtain the normal stress threshold value of i-th structural plane peak value angle of friction σ_i≥2.3·JRC_i/(g_2iδ), wherein: $g_{\mathrm{ni}}=\frac{{\mathrm{\φ}}_{\mathrm{ni}}-{\mathrm{\φ}}_{\mathrm{ni}-1}}{{\mathrm{\σ}}_{\mathrm{ni}}-{\mathrm{\σ}}_{\mathrm{ni}-1}},g_{2i}=\frac{{\mathrm{\φ}}_{2i}-{\mathrm{\φ}}_{1i}}{{\mathrm{\σ}}_{2i}-{\mathrm{\σ}}_{1i}},$

7) the average normal direction stress threshold of this group structural plane peak value angle of friction is determinedWhen this group M structural plane peak value angle of friction normal stress threshold value σ_iExtreme difference less than meansigma methods 15% time, Described extreme difference is the difference of maximum and minima, and the normal direction taking m structural plane peak value angle of friction should Power threshold value σ_iMeansigma methodsNormal stress threshold value as this group structural plane peak value angle of friction.

Further, described step 7) in, when the normal stress of m structural plane peak value angle of friction Threshold value extreme difference σ_iDuring more than meansigma methods 15%, the structural fece sample being stepped up same size is carried out Direct shear test, until wherein there being extreme difference the putting down less than m selected sample of m sample All normal stress threshold value 15% time, take m selected structural fece sample peak value and rub horn cupping To the meansigma methods of stress threshold as the final normal stress threshold of this group structural plane peak value angle of friction Value.

In order to obtain executing a normal stress threshold value for slope project structural plane peak value angle of friction, use The normal stress threshold value determination method of rock mass discontinuity angle of friction.Meet engineering rock mass angle of friction Relative error be 10%.

The normal stress threshold value determination method of the rock mass discontinuity angle of friction of the present embodiment, its Determine that step is as follows:

1) rating test direction.Rating test direction on selected engineering rock structural face；

2) Selection experiment structural plane and sample quantities.According to the scale of engineering rock structural face, Selected one group of structural plane a size of 600mm not changed with dimensional effect, and to selected size Structural plane is sampled processing；This group structural fece sample quantity is 3.

3) the roughness value JRC of i-th structural plane is measured_i.Between i-th structural plane is carried out It is divided into the line of 100mm, and measures the roughness value of every scribing position；Then to this The roughness value of all surveys line of structural plane is averaged JRC_i.Wherein, i=1,2,3.Such as table 1 Shown in.

The roughness value of each structural plane of table 1 is averaged JRC_i

4) obtain the peak value of i-th structural plane under the low normal stress of two-stage by direct shear test to rub Wipe angle φ_1i、φ_2i.I-th structural plane is carried out direct shear test, and normal stress is taken as respectively σ_1i=0.25MPa, σ_2i=0.5MPa, can obtain the structural plane peak under the conditions of the low normal stress of two-stage Value shearing strength τ_1iAnd τ_2i, then according to formulaObtain this structural plane in two-stage Peak value angle of friction φ under the conditions of low normal stress_1i, φ_2i.Wherein, i=1,2,3.As shown in table 2.

Structural plane	1st structural plane	2nd structural plane	3rd structural plane
				φ1i	51.16°	50.78°	49.68°
φ2i	46.25°	45.77°	45.20°

The peak value angle of friction φ of each structural plane of table 2_1i、φ_2i

5) the relative error magnitudes δ of engineering rock structural face peak value angle of friction is determined.According to engineering Require as δ=10%.

6) normal stress threshold value σ of i-th structural plane peak value angle of friction is determined_i.By structural plane The rate of change formula of peak value angle of frictionObtain i-th structural fece sample peak value angle of friction Normal stress threshold value σ_i≥2.3·JRC_i/(g_2iδ), wherein: $g_{\mathrm{ni}}=\frac{{\mathrm{\φ}}_{\mathrm{ni}}-{\mathrm{\φ}}_{\mathrm{ni}-1}}{{\mathrm{\σ}}_{\mathrm{ni}}-{\mathrm{\σ}}_{\mathrm{ni}-1}},g_{2i}=\frac{{\mathrm{\φ}}_{2i}-{\mathrm{\φ}}_{1i}}{{\mathrm{\σ}}_{2i}-{\mathrm{\σ}}_{1i}}.$ As Shown in table 3.

Structural plane	1st structural plane	2nd structural plane	3rd structural plane
				g2i	19.65	18.85	17.93
σi(MPa)	11.01	10.63	10.40

The g of each structural plane of table 3_2iWith normal stress threshold value σ_i

7) the final normal direction stress threshold of this group structural plane peak value angle of friction is determinedThis group 3 Normal stress threshold value σ of individual structural fece sample peak value angle of friction_iExtreme difference is meansigma methods 5.7%, Less than the 15% of meansigma methods, therefore take the normal stress threshold value of all 3 structural plane peak value angle of frictions Meansigma methods 10.68MPa as final normal direction stress threshold.

Claims (2)

1. a normal stress threshold value determination method for rock mass discontinuity peak value angle of friction, its feature exists In: described determine that method comprises the following steps:

1) rating test direction: rating test direction on selected engineering rock structural face；

2) Selection experiment structural plane and sample quantities: according to the scale of engineering rock structural face, Selected one group of structural plane size not changed with dimensional effect, and the structural plane of selected size is entered Row sampling processing；This group structural fece sample number be m, m be the natural number not less than 3；

3) the roughness value JRC of i-th structural plane in this group m structural plane is measured_i, I-th structural plane is rule according to certain intervals, and measures the roughness of every scribing position Coefficient；Then the roughness value to surveys line all on this structural plane is averaged and is obtained this structure Face JRC_i；

4) by the peak of i-th structural plane under the conditions of the direct shear test acquisition low normal stress of two-stage Value angle of friction φ_1i、φ_2i, i-th structural fece sample in this group is carried out two-stage low normal stress bar Direct shear test under part, normal stress is taken as σ respectively_1i=0.25MPa, σ_2i=0.5MPa, can obtain Obtain the structural plane peak shear strength τ under the conditions of the low normal stress of two-stage_1iAnd τ_2i, then according to public affairs FormulaObtain this structural plane structural plane peak value under the conditions of the low normal stress of two-stage Angle of friction

5) the relative error magnitudes δ of engineering rock structural face peak value angle of friction is determined；

6) normal stress threshold value σ of i-th structural plane peak value angle of friction is determined_i；Should by normal direction The rate of change formula of powerObtain the normal stress threshold value of i-th structural plane peak value angle of friction σ_i≥2.3·JRC_i/(g_2iδ), wherein:N in subscript is N level normal stress, i is the i-th structural plane in this group m structural plane, and 2 is second level method To stress；g_niFor i-th structural plane structural plane peak value angle of friction under n-th grade of normal stress Rate of change, g_2iFor the structural plane peak value friction under the 2nd grade of normal stress of the i-th structural plane The rate of change at angle, δ represents the relative error magnitudes of rock mass discontinuity peak value angle of friction；

7) the average normal direction stress threshold of this group structural plane peak value angle of friction is determinedWhen this group m Individual structural plane peak value angle of friction normal stress threshold value σ_iExtreme difference less than meansigma methods 15% time, described Extreme difference is the difference of maximum and minima, takes the normal stress threshold of m structural plane peak value angle of friction Value σ_iMeansigma methodsNormal stress threshold value as this group structural plane peak value angle of friction.

2. the determination of the normal stress threshold value of rock mass discontinuity peak value angle of friction as claimed in claim 1 Method, it is characterised in that: described step 7) in, when the method for m structural plane peak value angle of friction To stress threshold σ_iDuring more than meansigma methods 15%, the structural fece sample being stepped up same size enters Row direct shear test, until wherein having the extreme difference of m sample less than m selected sample Average normal direction stress threshold 15% time, take selected m structural fece sample peak value angle of friction normal direction The meansigma methods of stress threshold is as the final normal direction stress threshold of this group structural plane peak value angle of friction.