CN107194038B - Determination method for smooth surface energy gathering blasting parameters in layered rock tunnel - Google Patents

Determination method for smooth surface energy gathering blasting parameters in layered rock tunnel Download PDF

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CN107194038B
CN107194038B CN201710274776.6A CN201710274776A CN107194038B CN 107194038 B CN107194038 B CN 107194038B CN 201710274776 A CN201710274776 A CN 201710274776A CN 107194038 B CN107194038 B CN 107194038B
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苏玉宝
郭立军
徐奎
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China Tiesiju Civil Engineering Group Co Ltd CTCE Group
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Abstract

The invention discloses a smooth surface energy-gathering explosion in a layered rock tunnelThe method for determining the breaking parameters comprises the following steps: designing an energy gathering pipe influence factor lambda; calculating the detonation pressure P generated by the smooth blasting detonation product in a general state; calculating strain energy converted by blasting; under the action of the energy collecting pipe detonation pressure P generated under energy gathering blasting 1 、P 2 Relationship with λ, P; calculating the tensile stress and the compressive stress of the rock wall under the energy gathering blasting; calculating the relation between the peripheral eye distance and the angle of the lamellar rock mass structural plane under the coulomb criterion condition; and calculating the relation between the peripheral eye distance and lambda under the condition of the maximum tensile stress criterion. The invention can accurately calculate the proper value of the corresponding change of the peripheral eye distance under the influence of different energy gathering tube rigidity lambda when the angle of the structural surface in the layered rock body and the peripheral eye distance is different. Therefore, the problems that the overexplosion is serious in the layered rock mass, the excavation contour line is not uniform, and the smooth blasting excavation contour line is controlled more simply and accurately are solved.

Description

Determination method for smooth surface energy gathering blasting parameters in layered rock tunnel
Technical Field
The invention relates to the technical field of civil engineering, in particular to a method for determining a smooth surface energy gathering blasting parameter in a layered rock tunnel.
Background
Smooth blasting is a controlled blasting technique which enables post-blasting contour lines to meet design requirements through correctly selecting blasting parameters and reasonable construction methods and partitioning and sectioning differential blasting. The smooth blasting technique can obtain ideal blasting surface without over-digging, the method has the advantages of no lack of excavation and the like, and is widely used for blasting tunnels. The energy gathering smooth blasting is characterized in that on the basis of smooth blasting, an energy gathering device is adopted to concentrate the energy of explosive to transfer in a preset blasting direction, so that the energy release of the explosive is better controlled, the rock of a preset contour line of a tunnel is cut, a smoother and ideal blasting surface is obtained, and the assurance that the blasting parameters of peripheral eyes are blasted out of the preset contour surface is correctly determined. However, the theoretical research results of the determination of blasting parameters in transverse isotropic rock mass and the influence of the development directions of structural surfaces and joint cracks on the peripheral eye distance are relatively few at present.
Disclosure of Invention
The invention aims to provide a scientific and accurate determination method of a smooth surface energy gathering blasting parameter in a layered rock tunnel, which solves the problems of severe smooth surface blasting overexcavation, uneven profile surface and the like caused by the existence of a structural surface in the layered rock.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a method for determining a smooth surface energy gathering blasting parameter in a layered rock tunnel comprises the following steps:
(1) The explosive energy is uniformly transferred along the periphery, and the energy released in explosion is divided into two parts due to the existence of the energy-gathering seam, and one part is the energy V uniformly transferred to the periphery of the hole wall 1 Which generates a peripheral internal pressure P to the periphery 1 Wherein the internal peripheral pressure P 1 The accumulated strain energy is upsilon ε1 Part is the energy V collected along the slit 2 Generating a concentrated internal pressure P 2 The accumulated strain energy is upsilon ε2 The method comprises the steps of carrying out a first treatment on the surface of the Strain energy v accumulated by detonation product acting on rock wall ε Represented by the formula:
Figure BDA0001278259200000011
wherein: v—poisson ratio of rock mass;
σ 1 、σ 2 、σ 3 -respectively representing hoop stress, axial stress and radial stress at any point on the thin wall;
e-elastic modulus of rock mass;
(2) Let the influence factor lambda, wherein 0.ltoreq.lambda.ltoreq.1, the influence factor lambda is related to the material of the energy collecting pipe, the width and length of the energy collecting gap, let the energy distribution be distributed according to the following formula:
υ ε1 ＝(1-λ)υ ε
υ ε2 ＝λυ ε
(3) From the internal pressure P 1 The generated circumferential load F 1 Calculated as follows:
Figure BDA0001278259200000021
wherein: alpha, a slight angle of variation along the radial direction, rad;
d b -hole diameter, m;
l c -charge length, m;
load around F 1 Force is divided into two directions, and an acting force is generated on the x axis and an acting force is generated on the y axis; the force generated in the x-axis is the compressive stress on the rock at the surrounding rock side; the acting force generated in the positive direction of the y axis is a tensile stress acting on the rock temporary surface side; for the four-side load F 1 Integrating along the y-axis direction, by the circumferential load F 1 Tensile stress generated by working rock
Figure BDA0001278259200000025
The method comprises the following steps:
Figure BDA0001278259200000022
in the formula ：Ee -peripheral eye distance, cm;
for the four-side load F 1 Integrating along the x direction to obtain the surrounding load F 1 Compressive stress generated by working rock
Figure BDA0001278259200000023
The method comprises the following steps:
Figure BDA0001278259200000024
(4) From the concentrated internal pressure P 2 The resultant concentrated load F 2 Calculated as follows:
from the concentrated internal pressure P 2 The resulting concentrated load F on the rock wall 2 The size of (2) is:
Figure BDA0001278259200000031
in the formula ：ρ0 Density of explosive, g/cm 3 ；
D, explosive explosion speed, m/s;
l b -big gun hole lengthDegree, m;
d c -explosive diameter, m;
θ—the central angle corresponding to the width of the energy-gathering seam, rad;
delta-thickness of thin-walled cylinder;
n-the increase in stress produced when the gas generated after blasting hits the rock wall;
its tensile stress
Figure BDA0001278259200000032
Expressed by the following formula:
Figure BDA0001278259200000033
compressive stress
Figure BDA0001278259200000034
The representation is:
Figure BDA0001278259200000035
under the action of the energy collecting pipe, the peripheral load F 1 Concentrated load F 2 Tensile stress sigma on rock under combined action y The method comprises the following steps:
Figure BDA0001278259200000036
from the above arrangement, we obtain:
Figure BDA0001278259200000037
in the x-axis direction, the circumferential load F 1 Concentrated load F 2 Compressive stress sigma to rock under combined action x The method comprises the following steps:
Figure BDA0001278259200000041
Figure BDA0001278259200000042
(5) Assume that the included angle between the structural surface and the contour line of two blast holes is beta i Positive stress sigma on structural face γ The clamping angle with the x-axis is as follows:
γ i ＝|β i -90°|
the unit body is under compressive stress sigma x And tensile stress sigma y Under the action of the shear stress tau x Zero, so that the unit body has positive stress sigma in the gamma direction γ And shear stress τ γ Expressed by the following formula:
Figure BDA0001278259200000043
Figure BDA0001278259200000044
when the explosive explodes to act on the rock, the tensile stress is greater than the ultimate tensile strength sigma of the rock p During the process, the rock is pulled and damaged along the y direction of the contour line, and the shear stress in the direction of the structural surface is smaller than the shear strength of the rock; namely the failure criterion equation is:
σ y ≥σ p
Figure BDA0001278259200000045
the following steps are obtained:
Figure BDA0001278259200000046
wherein ,
Figure BDA0001278259200000047
-internal friction angle of the structural face, C-cohesion on the structural face.
As a further scheme of the invention: the boundary conditions of the influencing factor λ are:
(1) when λ=0, the rigidity of the energy gathering tube is zero, the effect of detonation products on the rock wall in this case is equal to that of a general explosion, and the influence of the energy gathering tube on the explosion is not great; namely P 2 ＝0，P 1 ＝P；
(2) When λ=1, the energy-collecting pipe is made of rigid material, and the energy is concentrated in the energy-collecting slits at two sides for diffusion, i.e. P 1 ＝0。
As a further scheme of the invention: gamma, influencing factor lambda and peripheral eye distance E e The expression of (2) is:
Figure BDA0001278259200000051
as a further scheme of the invention: the thickness W of the light surface layer is obtained according to the peripheral eye distance: w=1.25e e 。
Compared with the prior art, the invention has the beneficial effects that:
according to the method, different angles are calculated according to angles between the structural surface and the peripheral eye distance, coulomb and maximum tensile stress damage criteria are introduced, the change of the peripheral eye distance under different influence factors is accurately calculated, the conventional peripheral eye parameter determination is improved to accurate calculation according to practical experience analogy, the distance between the peripheral eyes of the energy-gathering smooth blasting and the thickness of the smooth surface layer are obtained, and the algorithm can accurately calculate proper values of the corresponding change of the peripheral eye distance under the influence of different energy-gathering pipe rigidity lambda when the angles between the structural surface and the peripheral eye distance in the layered rock body are different. Therefore, the problems that the overexplosion is serious in the layered rock mass, the excavation contour line is not uniform, and the smooth blasting excavation contour line is controlled more simply and accurately are solved.
Drawings
FIG. 1 is a schematic diagram of a structure of a cumulative tube;
FIG. 2 is a cross-sectional view of FIG. 1;
FIG. 3 is a graph showing the internal pressure profile after the action of a focused burst;
FIG. 4 is a diagram showing the state of stress of the unit cell under the action of unidirectional concentrated internal pressure;
FIG. 5 is a diagram showing the state of stress of the unit body under the action of uniform internal pressure;
FIG. 6 is a schematic diagram of a peripheral interocular spacing between two blastholes;
FIG. 7 is a schematic diagram of the rock wall under the action of uniform pressure;
FIG. 8 is a stress distribution diagram of transverse tensile stress generated when a rock wall is subjected to unidirectional concentrated pressure;
FIG. 9 is a schematic view of the angle between the two blast holes and the structural surface of the layered rock mass;
FIG. 10 is a schematic diagram of the stress experienced by a unit rock mass between two blastholes.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The invention relates to a method for determining tunnel energy-gathering smooth blasting parameters, which is described in detail below with reference to the accompanying drawings and a specific algorithm. The blastholes (peripheral holes) on the energy-collecting smooth blasting contour line are detonated finally after blasting of other blastholes, and the peripheral holes adopt energy-collecting pipe for charging, so that the explosive energy is concentrated, and the rock mass is blasted out along the excavation contour line. The invention uses PVC pipe with length of 3.5m and diameter of 36mm as energy gathering pipe to make energy gathering seam cutting (figure 1-2), the energy gathering seam blasting means that the energy released by explosive explosion is gathered into energy gathering flow along the seam cutting groove hole, and high-pressure and high-speed high-temperature jet flow is produced at the seam cutting groove hole, so that it has super-strong penetrating power, so that the rock can be cut, and a relatively flat profile surface can be obtained.
In general smooth blasting, uncoupled charge is adopted, and when uncoupled charge is adopted, detonation waves firstly press air in a gap between the condensation energy pipe and the rock wall to cause air shock waves, and then the air shock waves act on the rock wall. Therefore, in the case of a pair of calculation for applying a rock wall load, it is assumed that:
(1) The expansion of the explosive product in the gap is adiabatic expansion, and the expansion rule is PV 3 Equal to a constant, the impact pressure is excited by the rock wall, and an explosion stress wave is caused in the rock;
(2) Neglecting the presence of air in the gap (smaller gap);
(3) Pressure at which detonation products begin to expand is the average detonation pressure P m And (5) calculating.
Figure BDA0001278259200000061
in the formula ：ρ0 -explosive density (g/cm) 3 ) The method comprises the steps of carrying out a first treatment on the surface of the D-explosive detonation velocity (m/s);
is obtained by the method of the formula (1), the relationship of the blast hole internal pressure before the detonation product impacts the rock wall is as follows:
Figure BDA0001278259200000071
in the formula ：
V c -volume of explosive (m 3 )； V b -blasthole volume (m) 3 )；
According to the related research, when detonation products strike the rock wall of the blast hole, the pressure is obviously increased by a multiple n=8-11. n-the increase in stress produced when the gas generated after blasting hits the rock wall. Thus, the blasthole rock wall is subjected to detonation pressure as follows:
Figure BDA0001278259200000072
charging a drilling column in the tunneling process:
Figure BDA0001278259200000073
in the formula ：db -hole diameter (m); d, d c -explosive diameter (m);
l b -the blast hole length (m); l (L) c -charge length (m);
the detonation pressure to which the blasthole rock wall is subjected is obtained by the formula (3) and the formula (4):
Figure BDA0001278259200000074
for the convenience of analysis, the pressure to the rock wall when the explosive explodes is set to act in a thin-wall cylindrical cylinder with two closed ends, the detonation products are uniformly spread in the cylinder, the internal pressure born by the container is P, and the rock wall is regarded as an ideal elastoplastic body and is deformable. Similarly, thin-walled containers are considered ideal elastic bodies. By calculating the stress distribution state of any point on the cylinder, the strain energy v accumulated by the rock wall is obtained ε . The strain energy accumulated by the detonation product acting on the rock wall can be represented by the following formula:
Figure BDA0001278259200000075
wherein: v—poisson ratio of rock mass;
σ 1 、σ 2 、σ 3 -respectively representing the hoop, axial and radial stresses at any point on the thin wall;
e-elastic modulus of rock mass;
let delta < d c Delta is the thickness of the thin-walled cylinder, and the normal stress sigma at each point on the longitudinal section 1 Resultant force F on y-axis of the cylinder surface of the segment y ＝P·d c From the equilibrium equation relationship of the y-axis:
∑F y ＝0，P·d c -2σ 1 ×δ×1＝0 (7)
calculating the normal stress sigma according to the axial stretching 2 Is that;
Figure BDA0001278259200000081
radial normal stress sigma 3 The method comprises the following steps:
σ 3 ＝-P (9)
substituting (7), (8) and (9) into (6) to obtain strain energy v accumulated by the action of detonation products on the rock wall ε Value:
Figure BDA0001278259200000082
the explosive energy is uniformly transferred along the periphery. However, due to the existence of the energy gathering seam, the energy released during explosion is divided into two parts, one part is the energy V uniformly transferred to the periphery of the hole wall 1 Which generates a peripheral internal pressure P to the periphery 1 Wherein the internal peripheral pressure P 1 The accumulated strain energy is upsilon ε1 Part is the energy V collected along the slit 2 Generating a concentrated internal pressure P 2 The accumulated strain energy is upsilon ε2 Its function is that effects (fig. 3):
it is not necessary to assume that the energy distribution should be distributed as follows, when the influencing factors λ are introduced, and the influencing factors are related to the material of the energy collecting tube, the width and the length of the energy collecting slot, and the like:
υ ε1 ＝(1-λ)υ ε (11)
υ ε2 ＝λυ ε (12)
the boundary conditions for λ are:
(1) when λ=0, the stiffness of the energy gathering tube is zero, the effect of the detonation product on the rock wall in this case is equivalent to that of a general explosion, and the impact of the energy gathering tube on the explosion is not great. Namely P 2 ＝0，P 1 ＝P。
(2) When λ=1, that is, the energy-collecting pipe is made of rigid material, energy only diffuses into the energy-collecting slits at two sides. Namely P 1 =0. P is derived by equalizing the strain energy in both cases 1 ，P 2 Relationship to P.
Due to the additivity of the force and energy, can first concentrate internal pressure P 2 Part of the generated strain energy is analyzed, and the two sides of the cylinder are only subjected to concentrated internal pressure to act as P 2 The balancing square of the column x-axis as shown in FIG. 4 (a)Relationships of the program obtaining:
Figure BDA0001278259200000094
positive stress sigma at points on the cylinder cross section 2 Equal, calculate its normal stress sigma by axial stretching 2 ' from FIG. 4 (b);
Figure BDA0001278259200000091
wherein: a represents the width (mm) of the energy gathering gap;
radial normal stress sigma' 3 The method comprises the following steps:
σ 3 ′＝-P 2 (15)
σ 3 ' absolute value is much smaller than sigma 1 ' so approximate sigma 3 ′＝0。
As is clear from (13), (14) and (15), only the internal pressure P is concentrated 2 Any point of the cylinder is in a uniaxial tension state under partial action, and the expression of strain energy is as follows:
Figure BDA0001278259200000092
is composed of (10), (12) (16) the internal pressure P in the concentration can be obtained 2 Is represented by the expression:
Figure BDA0001278259200000093
at an internal pressure P of four sides 1 Part of the generated strain energy analysis, which is analogous to the strain energy generated by a general explosion, is shown in FIG. 5 (a) and is related to the equilibrium equation of the x-axis:
∑F y ＝0，P 1 ·d c -2σ 1 ″×δ×1＝0 (18)
calculated by axial stretching, as shown in FIG. 5 (b) its normal stress sigma 2 "yes;
Figure BDA0001278259200000101
radial normal stress sigma 3 "is:
σ 3 ″＝-P 1 (20)
substituting (18), (19) and (20) into (6) to obtain strain energy v accumulated by the action of detonation products on the rock wall ε1 Value:
Figure BDA0001278259200000102
is prepared from (10), (11) and (22), and the internal pressure P 1 Is represented by the expression:
Figure BDA0001278259200000103
substituting the boundary conditions into (17), (23), when verifying that λ=0 is available, P 1 ＝P，P 2 =0. λ=1, P 1 =0, satisfying the boundary condition.
The peripheral holes are drilled along the contour lines, so that the rock between two adjacent blast holes is subjected to the explosion action of the explosive charges to cut the rock mass, as shown in fig. 6. The internal pressure P on the periphery of the rock wall is uniformly distributed along the periphery of the hole wall 1 Thus, a peripheral load F acts on the periphery 1 Uniformly spread 360 ° around, and thus can be expressed as:
Figure BDA0001278259200000104
according to (5), (23), it is possible to write (24) as:
Figure BDA0001278259200000105
wherein: α—a slight angle (rad) of its variation along the radial direction;
establishing a rectangular coordinate system (e.gFIG. 7), four-side load F 1 Force is split into two directions, force is generated in the x-axis and force is generated in the y-axis. The force generated on the x-axis is the compressive stress on the rock on the surrounding rock side, and the force generated on the y-axis is the tensile stress on the rock on the free surface side. Since the tensile strength of rock is 1/10 to 1/20 of the compressive strength, the rock is mostly broken by tension. The direction between two blast holes is the x axis, the side which is vertical to the x axis and points to the rock free surface is the y axis, and the surrounding load F 1 Integrating along the y direction to obtain the surrounding load F 1 Tensile stress sigma generated by working rock y The method comprises the following steps:
Figure BDA0001278259200000111
in the formula ：Ee -peripheral eye distance (cm);
from (26), (25):
Figure BDA0001278259200000112
for the four-side load F 1 Integrating along the x direction to obtain the surrounding load F 1 Compressive stress sigma generated by working rock x The method comprises the following steps:
Figure BDA0001278259200000113
substituting (25) into (28) to obtain:
Figure BDA0001278259200000114
from the concentrated internal pressure P 2 The resulting concentrated load F on the rock wall 2 As shown in the diagram (fig. 8 (a)), the load F is concentrated 2 Under the action of the pressure, the rock between the two blast holes is extruded firstly, and then due to the concentrated load F 2 Generates a tensile stress in the x-axis direction (fig. 8 (b)), and the rock is broken in tension (according to literature rock mechanics) which concentrates the load F 2 The size of (2) can be expressed as:
Figure BDA0001278259200000115
in the formula ：
θ—Central angle (rad) corresponding to energy-gathering slit width
From (5), (17), can write (30) to:
Figure BDA0001278259200000121
the tensile stress can be represented by the following formula:
Figure BDA0001278259200000122
from (31), (32):
Figure BDA0001278259200000123
the compressive stress may be represented by the formula (34):
Figure BDA0001278259200000124
substituting (31) into (34) to obtain the finished product:
Figure BDA0001278259200000125
under the action of the energy collecting pipe, the peripheral load F 1 Concentrated load F 2 The tensile stress generated on the rock under the combined action is as follows:
Figure BDA0001278259200000126
by the arrangement of the formulae (27), (33), (36), it is possible to obtain:
Figure BDA0001278259200000127
in the x-axis direction, the circumferential load F 1 Concentrated load F 2 The compressive stress to the rock under the combined action is:
Figure BDA0001278259200000128
substituting (29) (35) into (38) to obtain the finished product:
Figure BDA0001278259200000131
in a transversely isotropic rock mass, the failure state of the rock is mostly related to the development of the structural face, namely, the different included angles between the structural face and the connecting lines of the two blast holes affect the generation of the through cracks of the two blast holes. Precisely because of the structural surface, there are three conditions for the destructive form of the rock mass: (1) Y-direction stretch-breaking occurs along the contour line between two blast holes; (2) shear failure along the structural face; (3) And simultaneously, the stretch-breaking along the contour line between the two blast holes and the shearing damage along the structural surface of the layered rock mass occur.
The invention assumes that the included angle between the structural surface and the contour line of two blast holes is beta i The positions of the blast holes are inconsistent with the development of the structural surface of the layered rock mass, so that the included angles of the structural surface and the contour lines between the two blast holes are also changed continuously as shown in fig. 9, the rock mass analysis between the structural surface and the contour lines is carried out, and the stress state of the unit body is shown in fig. 10. Normal stress sigma on structural face γ The clamping angle with the x-axis is as follows:
γ i ＝|β i -90°| (40)
the unit body is under main stress sigma x And sigma (sigma) y Under the action of the shear stress tau x Zero, so that the unit body has positive stress sigma in the gamma direction γ And shear stress τ γ Can be represented by the following formula:
Figure BDA0001278259200000132
Figure BDA0001278259200000133
from the above, it is apparent that the second and third forms of blasting both have different degrees of influence on the photo-blasting effect in the smooth blasting. If a good photo-explosion effect is to be achieved in the layered rock mass, namely a first type of damage occurs, when the tensile stress generated by the explosion of the explosive on the rock is greater than the ultimate tensile strength of the rock, the rock will be pulled and damaged in the y direction along the contour line, and the shear stress in the structural plane direction is less than the shear strength of the rock itself. Thus, the following relationships can be broken:
σ y ≥σ p (43)
Figure BDA0001278259200000141
in the formula ：
Figure BDA0001278259200000142
-internal friction angle of structural face, C-cohesion on structural face
Substituting (37) into (43) can obtain:
Figure BDA0001278259200000143
substituting (37), (39), (40), (41), (42) into the destruction criterion equation (44) results in the arrangement:
Figure BDA0001278259200000144
the expression of (46) is replaced to obtain gamma, lambda and the distance E between peripheral eyes e Is represented by the expression:
Figure BDA0001278259200000151
peripheral eye distance E e The relation with the thickness of the photosurface layer is generally expressed by a dense coefficient K, the size of the photosurface layer has a great influence on the blasting effect of the photosurface layer, and the relation is as follows:
Figure BDA0001278259200000152
theory and practice prove that the ratio of the smooth blasting blasthole spacing to the smooth surface layer thickness is more proper to be 0.8, so that the smooth surface layer thickness is as follows:
W＝1.25E e (49)
wherein: w-light surface layer thickness (cm);
considering that the fracture surface can be made to follow the contour lines of two blast holes by simultaneously meeting the fracture criteria (45), (47), the peripheral eye distance E can be obtained e The thickness of the light surface layer is W, lambda and gamma i Can be found in table 1.
TABLE 1
Figure BDA0001278259200000153
Figure BDA0001278259200000161
Figure BDA0001278259200000171
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims (4)

1. A method for determining a smooth surface energy gathering blasting parameter in a layered rock tunnel is characterized by comprising the following steps:
(1) The explosive energy is uniformly transferred along the periphery, and the energy released in explosion is divided into two parts due to the existence of the energy-gathering seam, and one part is the energy V uniformly transferred to the periphery of the hole wall 1 Which generates a peripheral internal pressure P to the periphery 1 Wherein the internal peripheral pressure P 1 The accumulated strain energy is upsilon ε1 Part is the energy V collected along the slit 2 Generating a concentrated internal pressure P 2 The accumulated strain energy is upsilon ε2 The method comprises the steps of carrying out a first treatment on the surface of the Strain energy v accumulated by detonation product acting on rock wall ε Represented by the formula:
Figure FDA0001278259190000011
wherein: v—poisson ratio of rock mass;
σ 1 、σ 2 、σ 3 -respectively representing hoop stress, axial stress and radial stress at any point on the thin wall;
e-elastic modulus of rock mass;
(2) Let the influence factor lambda, wherein 0.ltoreq.lambda.ltoreq.1, the influence factor lambda is related to the material of the energy collecting pipe, the width and length of the energy collecting gap, let the energy distribution be distributed according to the following formula:
υ ε1 ＝(1-λ)υ ε
υ ε2 ＝λυ ε
(3) From the internal pressure P 1 The generated circumferential load F 1 Calculated as follows:
Figure FDA0001278259190000012
wherein: alpha, a slight angle of variation along the radial direction, rad;
d b -hole diameter, m;
l c -charge length, m;
load around F 1 Force is divided into two directions, and an acting force is generated on the x axis and an acting force is generated on the y axis; the force generated in the x-axis is the compressive stress on the rock at the surrounding rock side; the acting force generated in the positive direction of the y axis is a tensile stress acting on the rock temporary surface side; for the four-side load F 1 Integrating along the y-axis direction, by the circumferential load F 1 Tensile stress generated by working rock
Figure FDA0001278259190000026
The method comprises the following steps:
Figure FDA0001278259190000021
in the formula ：Ee -peripheral eye distance, cm;
for the four-side load F 1 Integrating along the x direction to obtain the surrounding load F 1 Compressive stress generated by working rock
Figure FDA0001278259190000022
The method comprises the following steps:
Figure FDA0001278259190000023
(4) From the concentrated internal pressure P 2 The resultant concentrated load F 2 Calculated as follows:
from the concentrated internal pressure P 2 The resulting concentrated load F on the rock wall 2 The size of (2) is:
Figure FDA0001278259190000024
in the formula ：ρ0 Density of explosive, g/cm 3 ；
D, explosive explosion speed, m/s;
l b -borehole length, m;
d c -explosive diameter, m;
θ—the central angle corresponding to the width of the energy-gathering seam, rad;
delta-thickness of thin-walled cylinder;
n-the increase in stress produced when the gas generated after blasting hits the rock wall;
its tensile stress
Figure FDA0001278259190000027
Expressed by the following formula:
Figure FDA0001278259190000025
compressive stress
Figure FDA0001278259190000028
The representation is:
Figure FDA0001278259190000031
under the action of the energy collecting pipe, the peripheral load F 1 Concentrated load F 2 Tensile stress sigma on rock under combined action y The method comprises the following steps:
Figure FDA0001278259190000032
from the above arrangement, we obtain:
Figure FDA0001278259190000033
in the x-axis direction, the circumferential load F 1 Concentrated load F 2 Compressive stress sigma to rock under combined action x The method comprises the following steps:
Figure FDA0001278259190000034
Figure FDA0001278259190000035
(5) Assume that the included angle between the structural surface and the contour line of two blast holes is beta i Positive stress sigma on structural face γ The clamping angle with the x-axis is as follows:
γ i ＝|β i -90°|
the unit body is under compressive stress sigma x And tensile stress sigma y Under the action of the shear stress tau x Zero, so that the unit body has positive stress sigma in the gamma direction γ And shear stress τ γ Expressed by the following formula:
Figure FDA0001278259190000036
Figure FDA0001278259190000037
when the explosive explodes to act on the rock, the tensile stress is greater than the ultimate tensile strength sigma of the rock p During the process, the rock is pulled and damaged along the y direction of the contour line, and the shear stress in the direction of the structural surface is smaller than the shear strength of the rock; namely the failure criterion equation is:
σ y ≥σ p
Figure FDA0001278259190000041
the following steps are obtained:
Figure FDA0001278259190000042
wherein ,
Figure FDA0001278259190000044
-internal friction angle of the structural face, C-cohesion on the structural face.
2. The method for determining a smooth surface energy concentrating blasting parameter in a layered rock tunnel according to claim 1, wherein the boundary condition of the influencing factor λ is:
(1) when λ=0, the rigidity of the energy gathering tube is zero, the effect of detonation products on the rock wall in this case is equal to that of a general explosion, and the influence of the energy gathering tube on the explosion is not great; namely P 2 ＝0，P 1 ＝P；
(2) When λ=1, the energy-collecting pipe is made of rigid material, and the energy is concentrated in the energy-collecting slits at two sides for diffusion, i.e. P 1 ＝0。
3. The method for determining a smooth surface energy concentrating blasting parameter in a layered rock tunnel according to claim 1, wherein γ, a factor λ, and a peripheral eye distance E e The expression of (2) is:
Figure FDA0001278259190000043
4. the method for determining a smooth surface energy gathering blasting parameter in a layered rock tunnel according to claim 1, wherein the thickness W of the smooth surface layer obtained from the distance between the peripheral eyes is: w=1.25e e 。
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