CN111368481A - Method for analyzing stability of directional perforation - Google Patents
Method for analyzing stability of directional perforation Download PDFInfo
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- CN111368481A CN111368481A CN202010233167.8A CN202010233167A CN111368481A CN 111368481 A CN111368481 A CN 111368481A CN 202010233167 A CN202010233167 A CN 202010233167A CN 111368481 A CN111368481 A CN 111368481A
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Abstract
The invention discloses a method for analyzing the stability of a directional penetration hole, which comprises the following steps: step 1, establishing a rock-soil constitutive model for directionally penetrating through a hole; step 2, establishing a stress distribution model of rock and soil around the directional penetration hole; step 3, carrying out numerical simulation analysis on the stability of the directional penetration hole according to the geotechnical constitutive model of the directional penetration hole and the stress distribution model of the geotechnical around the directional penetration hole established in the step 1 and the step 2; and 4, obtaining corresponding preventive measures according to the analysis result in the step 3. The invention has the beneficial effects that: by analyzing the properties of a target stratum, evaluating the stability of the penetrated hole by adopting a plurality of groups of mechanical key parameters according to different stratums, and optimizing related drilling process technologies aiming at specific problems, the stability of the wall of the drilled hole in the drilling process is ensured, and the subsequent construction operation is not influenced.
Description
Technical Field
The invention relates to the technical field of petroleum pipelines, in particular to a method for analyzing the stability of a directional through hole.
Background
The horizontal directional drilling and crossing technology is used as a branch of a non-excavation construction technology of an oil and gas pipeline, is developed on the basis of an oilfield directional drilling technology, and is formed by combining a traditional pipeline laying technology and the oilfield directional drilling technology. The process principle is as follows: during construction, a drill tool and a drill rod are driven by the drill according to a designed drilling track to construct an approximately horizontal guide hole, after the drill tool of the guide hole passes through the other side of the barrier and emerges, a drill bit and an instrument unit for guiding are dismounted, and an appropriate drill tool is selected according to the diameter of the passing pipeline and the passing geological condition to perform reverse reaming. And when the pore canal meets the requirement of back dragging of the pipeline, the drilling machine is used for pulling the prefabricated pipeline to the soil entry point from the soil exit point of the drilling machine through the pore canal formed by reaming, so that the laying of the pipeline is completed. The horizontal directional drilling and crossing is widely applied in the field of construction of long-distance oil and gas pipelines in China and becomes a preferred scheme of a trenchless crossing technology. However, the horizontal directional drilling technology is convenient to construct and has a lot of construction risks, and the stability of the hole wall mainly shows that the hole is reduced in diameter, collapsed and oversized, and even the ground is collapsed and adjacent underground and above-ground structures are damaged seriously. Therefore, it is necessary to comprehensively analyze the stability of the directional through-hole and to make corresponding preventive measures.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a method for analyzing the stability of a directional perforation, which evaluates the stability of the perforation, optimizes the related drilling process technology according to specific problems, and ensures that the borehole wall remains stable in the drilling process without affecting the subsequent construction operation.
The invention provides a method for analyzing the stability of a directional penetration hole, which comprises the following steps:
step 2, establishing a stress distribution model of rock and soil around the directional penetration hole;
and 4, obtaining corresponding preventive measures according to the analysis result in the step 3.
As a further improvement of the invention, the geotechnical constitutive model directionally penetrating the hole in the step 1 comprises an elastic model and a plastic model.
As a further improvement of the present invention, the elastic model includes a volume stress strain model and a shear stress strain model.
As a further improvement of the present invention, the volume stress strain model is:
in the formula, e0As initial void ratio, p0In order to be the initial average stress,
tensile stress limit value for elastic state, JelFor elastic volume strain, K is the logarithmic volume modulus and p is the equivalent compressive stress.
As a further improvement of the present invention, the shear stress strain model is:
S＝2Geel
wherein S is shear stress, G is shear modulus of elasticity, eelIs the elastic bias strain.
As a further improvement of the invention, the plastic model is a modified Drucker-Prager model, which includes a yield surface and a plastic potential surface.
As a further improvement of the invention, the yielding surface comprises a shear failure surface and a cap curved surface and a transition surface.
As a further improvement of the present invention, the shear failure plane is:
Fs＝t-ptanβ-d＝0
in the formula, FsThe shear failure stress of the shear failure surface is shown as t, equivalent stress is shown as p, equivalent soil pressure is shown as β, the slope of the linear yield surface on a pressure-stress curve is shown as d, and cohesive force of the material is shown as d.
As a further improvement of the present invention, the curved surface of the cap is:
in the formula (I), the compound is shown in the specification,Fcis the shear failure stress of the cap surface, p is the equivalent stress of the soil body, paIs the stress value corresponding to the focal point of the cap surface and the transition surface, R is the parameter for controlling the cap curved geometry, t is the equivalent stress, α is a constant, β is the slope of the linear yield surface on the pressure-stress curve, d is the cohesive force of the material, p is the cohesive force of the materialbIs the compressive yield average stress.
As a further improvement of the present invention, the transition surface is:
in the formula, FtIs the shear failure stress of the transition surface, p is the equivalent stress of the soil body, paThe stress value corresponding to the focal point of the cap surface and the transition surface is shown, t is equivalent stress, α is a constant, β is the slope of the linear yield surface on a pressure-stress curve, and d is the cohesive force of the material.
As a further refinement of the invention, the plastic potential surfaces include plastic potential surfaces on the curved surface of the cap, and plastic potential surfaces of the shear failure surface and the transition surface.
As a further improvement of the present invention, the plastic potential surface on the curved surface of the cap is:
in the formula, GcIs the shear failure stress of the plastic potential surface on the curved surface of the cap, p is the equivalent compressive stress of the soil body, paThe stress values corresponding to the focal points of the cap surface and the transition surface are shown, R is a parameter for controlling the cap curved geometry, t is equivalent stress, α is a constant, and β is the slope of the linear yield surface on the pressure-stress curve.
As a further improvement of the present invention, the plastic potential surfaces of the shear failure surface and the transition surface are:
in the formula (I), the compound is shown in the specification,Gsshear failure stress of plastic potential surfaces of a shear failure surface and a transition surface, p is equivalent compressive stress of soil bodyaFor the stress values corresponding to the cap face and transition face foci, β is the slope of the linear yield face on the pressure-stress curve, t is the equivalent stress, α is a constant.
As a further improvement of the invention, the stress distribution model of rock soil penetrating through the periphery of the drill hole is as follows:
σr＝p-δf×(p-p0)-αp
τrθ＝-2τxysin2θ+τyxcos2θ
τzθ＝0
τrz＝0
in the formula, σrRadial stress, σθCircumferential stress, σzzAxial stress, τrθ、τzθ、τrzThree tangential stresses, p is equivalent pressure of soil body, p0Is the initial soil pressure, delta is the parameter of infiltration state, f is the compressive strength of soil, α is a constant, mu is the internal friction angle, sigmaxStress in the x direction, σyStress in the y direction, σzIs the stress in the z direction, theta is the principal stress angle, tauxyFor xy-plane shear stress, τyxThe yx plane shear stress.
As a further improvement of the present invention, the specific method for performing numerical simulation analysis on the stability of the directional penetration hole in step 3 is to perform preliminary analysis on the stability characteristics of the collected relevant data of the research target stratum and perform numerical simulation analysis on the stability of the directional penetration hole according to the confining pressure of the stratum, the overburden pressure and the construction process parameters.
The invention has the beneficial effects that: by analyzing the properties of a target stratum, evaluating the stability of the penetrated hole by adopting a plurality of groups of mechanical key parameters according to different stratums, and optimizing related drilling process technologies aiming at specific problems, the stability of the wall of the drilled hole in the drilling process is ensured, and the subsequent construction operation is not influenced.
Drawings
FIG. 1 is a schematic flow chart of a method for analyzing stability of a directional perforation according to an embodiment of the present invention;
FIG. 2 is a graph of the yield surface of the modified Drucker-Prager cap model;
FIG. 3 is a diagram of the plastic potential surface of the modified Drucker-Prager cap model;
FIG. 4 is a graph of the original ground stress component;
FIG. 5 is a transformed geostress component;
FIG. 6 is a converted force system;
FIG. 7 is a sectional force diagram of a slant hole.
Detailed Description
The present invention will be described in further detail below with reference to specific embodiments and with reference to the attached drawings.
As shown in fig. 1, an embodiment of the present invention is directed through-hole stability analysis method, including:
Step 2, establishing a stress distribution model of rock and soil around the directional penetration hole;
and 4, obtaining corresponding preventive measures according to the analysis result in the step 3.
Further, the geotechnical constitutive model directionally penetrating through the hole in the step 1 comprises an elastic model and a plastic model.
Further, the elastic model comprises a volume stress strain model and a shear stress strain model. Since directionally openworked rock is actually a material with a porous medium whose elastic modulus is a nonlinear isotropic elastic modulus, the elastic model in the openworked rock constitutive model should include a volume stress-strain relationship and a shear stress-strain relationship.
Further, the volume stress strain model is:
in the formula, e0As initial void ratio, p0In order to be the initial average stress,
tensile stress limit value for elastic state, JelFor elastic volume strain, K is the logarithmic volume modulus and p is the equivalent compressive stress. The model considers the mean stress as an exponential function of the volume strain, more precisely the elastic volume strain is proportional to the logarithm of the mean stress.
Further, the shear stress strain model is:
S＝2Geel
wherein S is shear stress, G is shear modulus of elasticity, eelIs the elastic bias strain. Shear modulus is defined in two ways: one is to directly give the shear modulus, i.e. the shear modulus is constant; the other is that given a poisson's ratio, i.e. the shear modulus is determined by poisson's ratio and bulk modulus, it is also relevant for the average stress, i.e. the shear modulus increases after compression.
Further, the plastic model is a modified Drucker-Prager model, which includes a yield surface and a plastic potential surface.
The conventional geotechnical plastic models comprise a Mohr-Coulomb model and a Drucker-Prager model. However, the biggest problem of the two models is that the yield caused by soil body compression cannot be reflected, namely, the material can never yield under the action of the equal-direction compressive stress, which is obviously not consistent with the characteristics of the soil body. In order to solve the problem, a modified Drucker-Prager model is selected, a cap-shaped yielding surface is added on the linear Drucker-Prager model, yielding caused by compression is introduced, and meanwhile, the unlimited shear-expansion phenomenon of the material under the shearing action can be controlled.
Further, the yielding surface includes a shear failure surface and a cap curvature and transition surface. The yield surface of the modified Drucker-Prager model is shown in FIG. 2. As can be seen, the yield surface is composed of two sections, the shear failure surface given by Drucker-Prager and the cap curved surface on the right. Shearing the "fracture surface" means that this part does not harden, i.e. is ideally plastic, causing an increase in volume with a consequent reduction (softening) of the cap. The cap surface is an elliptic curve which can be enlarged or reduced (related to plastic volume strain). The gradual curve smooth connection between the shear failure face and the cap yield face.
Further, the shear failure surface is:
Fs＝t-ptanβ-d＝0
in the formula, FsThe shear failure stress of the shear failure surface is shown as t, equivalent stress is shown as p, equivalent soil pressure is shown as β, the slope of the linear yield surface on a pressure-stress curve is shown as d, and cohesive force of the material is shown as d.
Further, the curved surface of the cap is:
in the formula, FcIs the shear failure stress of the cap surface, p is the equivalent stress of the soil body, paIs the stress value corresponding to the focal point of the cap surface and the transition surface, R is the parameter for controlling the cap curved geometry, t is the equivalent stress, α is a constant, β is the slope of the linear yield surface on the pressure-stress curve, d is the cohesive force of the material, p is the cohesive force of the materialbIs the compressive yield average stress. p is a radical ofbThe cap is controlled for the intersection of the cap face and the P axis, called the compressive yield mean stressThe size of (2).
Further, the transition surface is:
in the formula, the shear failure stress p of the transition surface is the equivalent stress of the soil body, paThe stress value corresponding to the focal point of the cap surface and the transition surface is represented, t is equivalent stress, α is a number with a small value, generally 0.01- α -0.05, α -0 represents that no transition surface exists, softening does not occur on the cap surface because the normal direction of the cap surface points to the right (volume compression), α obtains larger curvature of the transition surface, which is beneficial to fitting shear failure data points, β is the slope of a linear yield surface on a pressure-stress curve, and d is material cohesion.
Further, the plastic potential surface includes a plastic potential surface on the curved surface of the cap, and a plastic potential surface of the shear fracture surface and the transition surface. The modified Drucker-Prager model also uses a few-segment composition (as shown in fig. 3) that is correlated on the cap surface and uncorrelated on the shear failure and transition surfaces.
Further, the plastic potential surface on the curved surface of the cap is as follows:
in the formula, GcIs the shear failure stress of the plastic potential surface on the curved surface of the cap, p is the equivalent compressive stress of the soil body, paThe stress values corresponding to the focal points of the cap surface and the transition surface are shown, R is a parameter for controlling the cap curved geometry, t is equivalent stress, α is a constant, and β is the slope of the linear yield surface on the pressure-stress curve.
Further, the plastic potential surfaces of the shear failure surface and the transition surface are as follows:
in the formula, GsShear failure stress of plastic potential surfaces of a shear failure surface and a transition surface, p is equivalent compressive stress of soil bodyaFor the stress values corresponding to the cap face and transition face foci, β is the slope of the linear yield face on the pressure-stress curve, t is the equivalent stress, α is a constant.
The direction of the hole deviates from the vertical direction, so the ground stress in the original vertical direction is not consistent with the direction of the hole any more, and the two ground stresses in the horizontal direction are not perpendicular to the direction of the hole any more, so that coordinate transformation is required for calculation.
Before the formation is not drilled, the rock is under original earth stress. The three principal stress directions of the original ground stress are generally considered to be along the vertical and horizontal directions, respectively (as shown in fig. 4, 5). In three-dimensional original ground stress σV、σH、σhAfter drilling a hole with a borehole inclination angle of α and an azimuth angle of β in the affected stratum, establishing a borehole rectangular coordinate system XYZ, wherein an original coordinate system is 1-2-3, a converted coordinate system is XYZ, and the conversion process between the original coordinate system and the converted coordinate system is as follows:
firstly, the coordinate system 1-2-3 is rotated β anticlockwise around the Z axis to be changed into an x, y and Z coordinate system, and then the x, y and Z coordinate system is rotated α degrees around the y axis to be changed into a X, Y, Z coordinate system.
The X axis passes through the highest point on the cross section of the borehole, and the Z axis is coincident with the axis of the borehole and faces upwards. The conversion relation between the original ground stress component in the 1-2-3 coordinate system and the original ground stress component in the X-Y-Z coordinate system is as follows:
the converted stress components are:
σx＝cos2α(σHcos2β+σhsin2β)+σVsin2β
σy＝σHsin2β+σhcos2β
σz＝sin2α(σHcos2β+σhsin2β)σVcos2α
τxy＝cosαsinβcosβ(σh-σH)
τxz＝cosαsinα(σHcos2β+σhsin2β-σV)
τyz＝sinαcosβsinβ(σh-σH)
after coordinate transformation, the hole is from sigmaV、σH、σhThe force system acting becomes influenced by sigmax、σy、σz、τxy、τxz、τyzThe force system of the composition acts. The force system causes a redistribution of the geotechnical stresses around the borehole, the redistributed force system including a radial stress σrrCircumferential stress σθθAxial stress σzzAnd three tangential stresses sigmarθ、σzθ、σrzThe stress situation is shown in fig. 6.
Analyzing the stress condition of an inclined plane (as shown in figure 7), which is vertical to the axis of the hole and is subjected to uniform shearing stress tau all aroundxyThe upper and lower sides are subjected to uniform compressive stress sigmayLeft and right are uniformly pressedx. The middle hole is acted by uniform pressure p, and the front and back surfaces are acted by uniform pressure sigmaZAnd uniform shear stress tauxz、τyz. Due to sigmaZ、τxz、τyzIs constant on the plane and does not contribute to the stress redistribution of the plane, so the problem can be treated as solving the infinite plane strain problem with circular holes.
Superposition by σxDistribution of induced stress, from σyInduced stress distribution, fromxyInduced stress distribution, calculated stress σzzFrom τxzInduced stress distribution, fromyzStress distribution caused by the pressure p of drilling fluid column in the hole, and drilling fluid seepage effect, so as to obtain the holes r of the inclined well and the horizontal wellStress distribution of the R rock soil.
Further, the stress distribution model of rock soil penetrating through the periphery of the drill hole is as follows:
σr＝p-δf×(p-p0)-αp
τrθ＝-2τxysin2θ+τyxcos2θ
τzθ＝0
τrz＝0
in the formula, σrRadial stress, σθCircumferential stress, σzzAxial stress, τrθ、τzθ、τrzThree tangential stresses, p is equivalent pressure of soil body, p0Is the initial soil pressure, delta is the parameter of infiltration state, f is the compressive strength of soil, α is a constant, mu is the internal friction angle, sigmaxStress in the x direction, σyStress in the y direction, σzIs the stress in the z direction, theta is the principal stress angle, tauxyFor xy-plane shear stress, τyxThe yx plane shear stress. When the wall surface of the hole has seepage, delta is 1, and when the wall surface of the hole has no seepage, delta is 0.
Further, the specific method for performing numerical simulation analysis on the stability of the directional penetration hole in the step 3 is to perform preliminary analysis on the stability characteristics of the collected relevant data of the research target stratum and perform numerical simulation analysis on the stability of the directional penetration hole according to the confining pressure of the stratum, the overburden pressure and the construction process parameters.
The horizontal length of the yellow river directional drilling crossing of the crude oil pipeline engineering is 1911.7 meters, the real crossing length is 1915.27 meters, the designed crossing curve soil entry angle is 10 degrees, the soil exit angle is 6 degrees, the crossing depth is 21 meters, the designed pressure of the crossing main pipeline is 6.3MPa, the pipe diameter phi 457 × 7.1.1 mm, when a pilot hole is completed, the reaming operation is immediately carried out after the 60-meter casing is removed, three-stage reaming is carried out, 5-1/2 ' S-135 drill rods qualified through field detection are adopted for reaming operation, 18 ' plate type reamers are used for the first stage, 24 ' plate type reamers are used for the second stage, 30 ' plate type reamers are used for the third stage, 24 ' barrel type reamers are used for hole washing, the crossing stratum is mainly a fine sand layer, local gravel is contained in the gravel, the crossing distance is long, the drill rods are easy to be blocked, the torque is increased, and the thrust or the tension is increased.
The method comprises the steps of establishing an eyelet stability finite element model according to the oriented crossing drill guide hole and reaming operation of the yellow river, wherein the rock soil adopts a modified Drucker-Prager model, the elastic modulus of a rock soil material is 90MPa, the Poisson ratio is 0.4, the internal friction angle is 33, the cohesive force is 22kPa, and the tensile strength is 40 kPa. The lowest elevation of the river channel which is subjected to flood scouring for 100 years is taken as the top of the model, 5m below the holes of the guide holes is taken as the bottom of the model to establish a model section, the top of the model is used for applying the gravity load P (x) of rock soil, water and the like above a scouring line, and the inner wall of the holes is applied with the mud hydrostatic column pressure. In the model, the gravity compaction effect of rock soil and river water on the flushing surface which directionally penetrates through the stratum is 300kPa, the gravity compaction effect of rock soil under the flushing surface is 140kPa, and the supporting effect of mud liquid column pressure on the pore is 230 kPa. And setting tensile failure and shear failure criteria of the hole-expanding rock soil in the model at the same time, dynamically simulating the shear stress and tensile stress states of the hole-expanded rock soil, and judging the stability of the hole.
During directional crossing, the original stress is disturbed during hole expanding, stress concentration is generated on the wall surface of the hole, and the affected area is only in a limited range near the hole. With the increase of the reaming times, the diameter of the hole is continuously increased, and the range of the hole rock where stress disturbance occurs is larger. From the numerical view, the maximum main stress at the top of each stage of reaming holes is a negative value, and the holes cannot be stretched and damaged under the action of pressure.
The maximum shearing stress value of the hole enlarging holes appears on the oblique angles of the holes, the shearing stress value is larger and exceeds 150kPa, but the shearing stress value of each stage of hole enlarging holes does not exceed Drucker-Prager shearing yield surfaces, and the hole enlarging holes are not subjected to shearing failure, which shows that the holes are stable under the supporting action of mud pressure when the directional crossing drilling and hole enlarging of the yellow river are completed.
In conclusion, the yellow river crude oil pipeline directionally passes through the holes of the gravel layer without tensile and shearing damage, and the holes are stable.
It has been found from analysis that under judicious choice of formation crossing, the reamed borehole is initially stable but there is also a risk of instability, particularly in the top region of the borehole. In order to effectively prevent the instability of the eyelet, the following preventive measures are proposed:
1) optimizing the design of the track of the directional crossing borehole, and adjusting the design curve of the directional crossing to ensure that the directional crossing avoids unfavorable strata or strata which are easy to cause slurry leakage and overflow; tamping sleeves at two ends to reinforce the hole wall in the stratum of the inclined shaft section at the loosening soil inlet end and the soil outlet end or the inclined shaft section which is likely to have the risk of hole collapse;
2) reasonably selecting a directional crossing stratum, and selecting a rock stratum or a rock stratum with higher strength as much as possible to carry out crossing, wherein the larger the stratum rock cohesion and the internal friction angle are, the better the well wall stability is;
3) optimizing the slurry performance design, enhancing the slurry wall building performance, improving the slurry hydration inhibition, reducing the amount of filtered water, properly improving the slurry viscosity and the mineralization degree, forming a high-performance filter cake or a net-shaped film structure, and effectively protecting the holes and the supporting holes;
4) the reaming speed is improved, scientific management is realized, the complex condition in the well is avoided, and the mud soaking time is reduced. The strength reduction of the rock and soil caused by the dehydration of the slurry is an important reason for the occurrence of the problem of the stability of the hole.
5) Further developing deep research, establishing a grading method and a calculation model of the rock and soil strength of the directional crossing stratum, and forming a grading technology of the stability of the directional crossing stratum eyelet.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (15)
1. A method for analyzing stability of a directional perforation, comprising:
step 1, establishing a rock-soil constitutive model for directionally penetrating through a hole;
step 2, establishing a stress distribution model of rock and soil around the directional penetration hole;
step 3, carrying out numerical simulation analysis on the stability of the directional penetration hole according to the geotechnical constitutive model of the directional penetration hole and the stress distribution model of the geotechnical around the directional penetration hole established in the step 1 and the step 2;
and 4, obtaining corresponding preventive measures according to the analysis result in the step 3.
2. The method for analyzing the stability of the directional crossing hole according to claim 1, wherein the geotechnical model of the directional crossing hole in the step 1 comprises an elastic model and a plastic model.
3. A method for directional cross-hole stability analysis according to claim 2, wherein the elastic model comprises a volumetric stress-strain model and a shear stress-strain model.
4. A method for analysis of stability of a directional crossing borehole according to claim 3, wherein said volumetric stress-strain model is:
in the formula, e0As initial void ratio, p0In order to be the initial average stress,
tensile stress limit value for elastic state, JelIs an elastic volumeStrain, K log bulk modulus, p equivalent compressive stress.
5. A method for analyzing stability of a directionally traversing borehole according to claim 3, wherein the shear stress strain model is:
S＝2Geel
wherein S is shear stress, G is shear modulus of elasticity, eelIs the elastic bias strain.
6. A method for directional perforation stability analysis according to claim 2, wherein the plastic model is a modified Drucker-Prager model comprising a yield surface and a plastic potential surface.
7. The method of analyzing stability of a directionally traversing aperture of claim 6, wherein the yielding surface comprises a shear failure surface, a cap curvature surface, and a transition surface.
8. A method for analyzing the stability of a directional crossing borehole according to claim 7, wherein said shear failure plane is:
Fs＝t-ptanβ-d＝0
in the formula, FsThe shear failure stress of the shear failure surface is shown as t, equivalent stress is shown as p, equivalent soil pressure is shown as β, the slope of the linear yield surface on a pressure-stress curve is shown as d, and cohesive force of the material is shown as d.
9. The method of analyzing stability of a directional through-the-hole of claim 7, wherein the cap surface is:
in the formula, FcIs the shear failure stress of the cap surface, p is the equivalent stress of the soil body, paThe stress value corresponding to the focal point of the cap surface and the transition surface, R is a parameter for controlling the cap curved geometric shape, and t isEquivalent stress, α is a constant, β is the slope of the linear yield surface on the pressure-stress curve, d is the material cohesion, p isbIs the compressive yield average stress.
10. A method for analyzing stability of a directional perforation according to claim 7, wherein said transition surface is:
in the formula, FtIs the shear failure stress of the transition surface, p is the equivalent stress of the soil body, paThe stress value corresponding to the focal point of the cap surface and the transition surface is shown, t is equivalent stress, α is a constant, β is the slope of the linear yield surface on a pressure-stress curve, and d is the cohesive force of the material.
11. The method of analyzing stability of a directional through-the-hole of claim 7, wherein the plastic potential surfaces comprise plastic potential surfaces on a curved surface of the cap, and plastic potential surfaces of a shear failure surface and a transition surface.
12. A method for analysis of stability of a directional through-the-hole according to claim 11, wherein the plastic potential surface on the curved surface of the cap is:
in the formula, GcIs the shear failure stress of the plastic potential surface on the curved surface of the cap, p is the equivalent compressive stress of the soil body, paThe stress values corresponding to the focal points of the cap surface and the transition surface are shown, R is a parameter for controlling the cap curved geometry, t is equivalent stress, α is a constant, and β is the slope of the linear yield surface on the pressure-stress curve.
13. A method for analysis of stability of a directionally traversing borehole according to claim 11, wherein the plastic potentials of said shear failure and transition surfaces are:
in the formula, GsShear failure stress of plastic potential surfaces of a shear failure surface and a transition surface, p is equivalent compressive stress of soil bodyaFor the stress values corresponding to the cap face and transition face foci, β is the slope of the linear yield face on the pressure-stress curve, t is the equivalent stress, α is a constant.
14. The method for analyzing stability of a directional through-hole according to claim 1, wherein the stress distribution model of the rock soil surrounding the through-hole is:
σr＝p-δf×(p-p0)-αp
τrθ＝-2τxysin2θ+τyxcos2θ
τzθ＝0
τrz＝0
in the formula, σrRadial stress, σθCircumferential stress, σzzAxial stress, τrθ、τzθ、τrzThree tangential stresses, p is equivalent pressure of soil body, p0Is the initial soil pressure, delta is the parameter of infiltration state, f is the compressive strength of soil, α is a constant, mu is the internal friction angle, sigmaxStress in the x direction, σyStress in the y direction, σzIs the stress in the z direction, theta is the principal stress angle, tauxyFor xy-plane shear stress, τyxThe yx plane shear stress.
15. The method for analyzing the stability of the directional penetration hole according to claim 1, wherein the step 3 of performing numerical simulation analysis on the stability of the directional penetration hole includes performing preliminary analysis on the stability characteristics of the collected relevant data of the research target stratum, and performing numerical simulation analysis on the stability of the directional penetration hole according to the confining pressure of the stratum, the overburden pressure and the construction process parameters.
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