Method and system for determining impact load of shield hob in composite stratum with soft upper part and hard lower part

Abstract

The invention belongs to the technical field of tunnel construction, and discloses an upper-soft lower-hard composite stratum shield hob impact load determination method and system.The method comprises the steps that rock is divided into a plurality of concentric circle areas through a cavity expansion model, the radius of each area is determined, and the relation between the damage states of different positions of rock mass and the distance position of the center of a blade is obtained; the influence of section penetration is introduced, and based on the influence of the damage difference between a vertical crack area and a dense nuclear area in the hob rock breaking process, the damage state of the hob section away from the center of a blade within the range of a hob lower contact area and the damage distribution state of the hob lower hard rock side in the interface vertical crack expansion process are determined; and determining an expression of stress change of the transition section based on a CSM model, and realizing impact load prediction when the shield hob passes through the upper-soft and lower-hard composite stratum in combination with the influence of damage of the lateral shearing region. The damage effect and cavity expansion model theory is introduced for the first time, the compatibility of the prediction model and the actual situation is improved, and the abnormal damage rate of the hob is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel construction, and particularly relates to a method and system for determining the impact load of a shield cutter in a soft-over-hard composite stratum. BACKGROUND

[0002] At present, large-diameter shield tunnels in China are in a high-speed construction and development stage. A large number of large-diameter shield tunnel projects crossing rivers and seas promote the development of shield technology in the direction of super-large section, super-long distance, and complex geological conditions. With the increase of the size of the shield section, the geological conditions faced develop in the direction of soft and hard composite stratum from homogeneous stratum.

[0003] The stress of the cutter of a large-diameter shield under a composite stratum is significantly different from that of a homogeneous hard rock. Among them, the soft-over-hard composite stratum is the most common, that is, the upper region of the tunnel section is a relatively low-strength stratum such as soft soil, strongly weathered rock, fissure zone of rock stratum, and karst cave, which generally has low strength, poor self-stability, and high water content; and the lower part is a medium or weakly weathered stratum, which generally has high strength, good self-stability, and high quartz content, and requires high rock breaking ability and wear resistance of the cutter. When a large-diameter shield is excavated in a composite stratum, the cutter is abnormally damaged at the soft and hard interface due to the impact, and the abnormal damage of the cutter caused by the interface impact in the composite stratum has become a key problem that restricts the safe and efficient construction of large-diameter shields. Although existing force prediction models of the cutter are based on different rock breaking mechanisms, they are mostly established based on the assumption of homogeneous stratum conditions and experimental data, and the rock breaking mechanism of the composite stratum is quite different from that of the homogeneous stratum. Therefore, a method for determining the size and distribution of the impact load of the cutter of a shield in a composite stratum is needed. The existing domestic and foreign technologies in the field of determining the impact load of the cutter of a shield in a composite stratum mostly use the CSM model, but the pressure distribution of the cutter analyzed by the CSM model based on homogeneous hard rock is nearly linear, and only a monotonous normal force value with different slopes can be obtained in the transition period. If this assumption is directly used for analysis, the result cannot reflect the impact problem at the interface, and if the mechanical joint of the soft and hard rock bodies is not tight and the mechanical parameters differ greatly, this assumption is not valid.

[0004] Through the above analysis, the problems and defects of the prior art are: on the one hand, when the traditional CSM model is applied to the composite stratum, the prediction error exceeds 40%, and it is difficult to accurately reflect the actual stress of the cutter; on the other hand, the existing composite stratum load prediction method does not consider the degradation of the lower rock mass of the cutter, and the prediction and control effect of the abnormal damage of the cutter is limited. And the present scheme obtains the impact load prediction formula of the transition zone cutting by taking the CSM model as the basis, from the angle of damage mechanics and spatial expansion model combined with the influence of the side shear zone, which can improve the prediction accuracy to more than 85%, accurately make up for the shortcomings of the prior art, and provide more reliable support for the stress analysis of the cutter in the composite stratum. SUMMARY

[0005] In order to overcome the problems in the related art, the present application discloses a kind of upper soft lower hard composite stratum shield cutter impact load determination method and system, to aim at the upper soft lower hard composite stratum when it is cut by cutter at the interface of soft and hard, the size and distribution law of the impact load that its cutter bears are predicted, the technical solution is as follows: The present application is realized in this way, a kind of upper soft lower hard composite stratum shield cutter impact load determination method, comprising the following steps: S1, adopt cavity expansion model to divide rock into multiple concentric circular regions, determine the radius of each partition and obtain the relationship between the damage state of rock mass at different positions and the distance position of cutter center; S2, introduce the influence of cross-section penetration, based on the influence of damage difference between vertical crack zone and dense core zone in the process of cutter rock breaking, determine the damage state of cutter section at the distance of cutter center in the contact area of lower cutter, and obtain the damage distribution state of hard rock side of lower cutter in the process of vertical crack propagation at the interface; S3, deduce the expression of stress change in transition section based on CSM model, combined with the influence of lateral shear zone damage, realize the impact load prediction when shield cutter penetrates the upper soft lower hard composite stratum.

[0006] In step S1, in the analysis, the damage evolution of the lower rock mass of the cutter is described from the perspective of damage mechanics, and the determination of the damage range is based on the related assumptions and conclusions of the cavity expansion theory; the central vertical crack expands in a semicircular shape, and the expansion radius is r c The internal damage degradation zone of the rock mass and the vertical crack propagation range are consistent when the cutter breaks the rock, and a composite stratum cutter rock breaking mechanics model based on damage influence is constructed; Construct a cavity expansion model, divide the soft rock area below the cutter into multiple concentric circular regions from the center point of the cutter ring blade; according to the differences in the damage mechanism of each region, from inside to outside, they are: a dense core zone with an outer radius of r d , the width is consistent with 2 w ; the outer radius ofr p of the broken zone; outer radius r c of the cracked zone, outer radius r e of the elastic zone, outermost is the undisturbed zone, the confining pressure of the rock mass at infinity σ 0; Damage and failure occur inside the rock mass under the expansion of the dense core zone. According to the partition condition of the damage mechanics combined with the cavity expansion model, when the equivalent attenuation coefficient of the rock mass has a linear relationship with the average damage and failure degree of the rock mass, and the rock mass damage changes linearly along the expansion direction, the damage factor is used to describe the damage state of the rock in the process, and the relationship between the damage state of the soft rock mass at different positions D S ( r ) and the distance position of the center of the blade r ; In the formula, the superscript S represents the soft rock, is an absolute value symbol, and represents r is a non-negative number. In the formula, H represents a truncation function, when x > 0, when x < 0, . is the radius of the radial crack zone of the soft rock, is the radius of the broken zone of the soft rock.

[0007] Further, the relationship between the damage state of the soft rock mass at different positions D S ( r ) and the distance position of the center of the blade r is averaged to obtain the equivalent damage of the soft rock at different positions ; According to the relationship between the material damage and the damage state, the relationship between the equivalent attenuation coefficient of the soft rock mass and the damage state is obtained as follows: In the formula, a is the attenuation coefficient of the broken rock mass, is the attenuation coefficient of the undisturbed intact rock mass, is the equivalent attenuation coefficient of the soft rock mass.

[0008] In step S2, the model is analyzed according to the plane strain problem: based on the analysis method of the plane strain problem, the radial stress and the tangential stress inside the soft rock mass are obtained according to the balance equation and stress-displacement relationship obtain general solution ; in which, , E and μ are the elastic modulus and Poisson's ratio of the material respectively, is the radial displacement, r s C1 and C2 are integral constants determined by boundary conditions; Relationship one: according to stress boundary conditions , , in which, is the tensile strength of the soft rock, represents the pressure of the surrounding rock at infinity; is the pressure of the surrounding rock at infinity of the soft rock; bring and into the general solution , based on the displacement boundary conditions in the elastic zone , the relationship between the radius of the elastic zone and the radius of the radial crack zone is: Relationship two: bring the stress conditions in the radial crack zone , into the equilibrium equation, obtain the stress in the radial crack zone , is the uniaxial compressive strength of the soft rock; based on the boundary stress continuity condition in which, , are the limit approaching expressions of the inside and outside radii of the interface between the radial crack zone and the crushing zone, obtain the relationship between the radius of the radial crack zone and the radius of the crushing zone : Relationship three: the crushing zone is calculated based on the Mohr-Coulomb strength criterion , in which the coefficient related to is the uniaxial compressive strength of the rock related to , σ θ is the tangential stress, is the internal friction angle of the rock mass, c is the cohesion of the material; bring the Mohr-Coulomb strength criterion equation into the equilibrium equation, when the rock inside the crushing zone yields and fails due to vertical stress p and horizontal stress​q If the dense core region is equivalent to the roller penetration load being transmitted in the form of hydrostatic pressure, then... p = q = p 0, p 0 is the reference pressure; according to the stress boundary conditions , The radius of the fractured zone in soft rock was obtained. radius of dense core region The relation is: In the formula, For soft rock, the coefficient is related to the internal friction angle; This is the reference pressure for soft rock.

[0009] In step S2, based on the geometry of each zone of the soft rock and the radius of the elastic zone in the soft rock... Radial crack zone radius Relationship, radial crack zone radius With the radius of the fracture zone Relationship, radius of the broken zone radius of dense core region The relationship determines the distribution and change of the damage range inside the soft rock during the roller cutter cutting process, and obtains the range of each damage area in the hard rock after the roller cutter has completely entered the hard rock through the interface. As the cutting tool gradually approaches the interface between the soft rock and hard rock in the soft rock, the damage and disturbance zone of the soft rock will come into contact with the hard rock due to the typical composite rock mass. Therefore, the damaged zone in the soft rock will be interrupted at the interface, and a dense core zone will be reformed in the hard rock when the cutter makes point contact with the hard rock. When the cutter fully penetrates the hard rock in the pressure zone, the lower damaged area expands to the level of the homogeneous rock mass. The size of the expansion range during this process is approximately equal to the length of the cutter. L The size of the contact zone entering hard rock Proportional to the damage distribution of hard rock during the propagation process, the relationship between the equivalent attenuation coefficient of soft rock and the damage state is used to obtain the damage distribution of hard rock during the propagation process. ; In the formula, the superscript H indicates hard rock. The length of the first half of the contact area of ​​the hob. The length of the contact zone into hard rock. For in position r The basic damage distribution function at the location, This is the hard rock damage distribution function after scaling transformation. At that time, through The location parameter r is scaled and then substituted into the hard rock foundation damage distribution function. In the middle, for the description of the front half of the contact area length L exceeds the contact area into the hard rock length When, the hard rock damage distribution with the scale transformation.

[0010] In step S2, according to the constructed cutter rock breaking force model, in soft rock based on the cutter rock breaking process vertical crack zone And dense core area The impact of damage difference, deduce the damage state of the cutter section at the distance of the cutter edge center r Where >0; r In the formula, 、 The soft rock cutter linear cutting test parameters are determined, the value range is related to the nature of the rock mass and the crack development degree; wherein, soft rock =0.3, =0.95, hard rock =0.35, =0.95, the relationship between the penetration of the cutter section at the distance of the cutter edge center r , The cutter radius is, The penetration of the cutter section at the cutter edge center is, The position parameter is, The position of the soft and hard rock interface is.

[0011] In step S2, the damage state of the cutter after entering the hard rock D H ( x , r ) is consistent with D S ( x , r ), wherein ; When the lower contact area of the cutter is close to the soft and hard rock interface, the vertical crack will be interrupted; after the contact area contacts the hard rock, it will expand in the hard rock again, and the expansion law of the fracture damage area satisfies the linear variation law of the damage distribution assumption of the hard rock; combined with the damage state of the cutter section, the damage distribution state of the lower hard rock side of the cutter during the vertical crack expansion process at the interface is obtained; In the formula, 、 The hard rock cutter linear cutting test parameters are determined, the value range is related to the nature of the rock mass and the crack development degree; ,​ .

[0012] In step S3, the dynamic change of the cutter force at the composite stratum interface is based on the CSM model used in homogeneous hard rock strata. By analyzing the influence of system deformation and composite rock mass damage on the pressure distribution and penetration of the cutter at the bottom, a predictive model for the impact load of the cutter in composite strata is constructed. The contact stress at the bottom of the CSM model is expressed as: in, φ θ is the contact angle between the cutter and the rock; C is a dimensionless coefficient. S The distance between the blades; σ c , σ t These are the rock mass compressive and tensile strengths, respectively. p s This represents the distributed contact stress at the bottom of the cutter ring; It is an integral variable used to describe the contact area from the beginning to the angular range; ψ This is the pressure distribution coefficient at the tool tip, ranging from -0.2 to 0.2, and varies with the tool tip width. T If the increase is due to the increase in size, 0.1 should be taken first. Integrating the load at the bottom of the hob, simplifying the expression... To obtain the stress changes in the soft rock section for: Similarly, the stress changes in the hard rock section can be obtained. for: The stress on the transition section is divided into two parts: the force of the soft rock section and the force of the intrusive hard rock section. By solving and summing the forces of the two parts separately, the stress variation formula of the transition section is obtained. ; In the formula, the superscript T represents the composite interface. , .

[0013] In step S3, the contact area length between the rock-breaking cycle and the cutter head is... LConsistent with the advance of the cutter, the normal component provided by the shear zone is constantly rising; when the shear zone of the bearing is damaged, this part of the component becomes 0, and the limit stress balance state analysis of the rock mass shear zone of the cutter center section is obtained: In the formula, is the angle between the bottom of the shear zone and the horizontal plane, θ c is the rake angle of the cutter blade, p l is the lateral force; According to the Mohr-Coulomb failure criterion , the formula is obtained ; the partial derivative is obtained ; the partial derivative is obtained , and the lateral force is obtained ; according to the contact geometry relationship between the front half part of the cutter and the shear zone, the normal force component provided by the shear zone is obtained F Nl , with the destruction of the shear zone F Nl the amplitude appears up and down fluctuation; according to the characteristic of the trigonometric function, the rock breaking period is consistent with the size of the cutter contact zone, and the rock mass parameters are simplified by judging the position of the cutter centroid, so that: According to the cavity expansion model, the stress change process of the transition section of the composite stratum is analyzed from the damage mechanics angle, and the normal force component provided by the shear zone is calculated based on the influence of the lateral shear zone damage ; the stress of the transition section and the normal force caused by the lateral shear zone damage are summed up, and the final calculation formula + is established; .

[0014] Another purpose of the present application is to provide a soft upper and hard lower composite stratum shield cutter impact load determination system, which is used for regulating and controlling the soft upper and hard lower composite stratum shield cutter impact load determination method, and the system comprises: The rock division module is used for dividing the rock into a plurality of concentric circular regions by using the cavity expansion model, determining the radii of the partitions, and obtaining the relationship between the damage state of the rock mass at different positions and the distance position of the cutter blade center. The damage state determination module is used for introducing the influence of the cross-section penetration, determining the damage state of the cross-section of the cutter at the center of the cutter in the lower contact area of the cutter based on the influence of the damage difference between the vertical crack zone and the dense core zone in the rock breaking process of the cutter, and obtaining the damage distribution state of the hard rock side of the lower cutter in the vertical crack propagation process at the interface. The impact load prediction module derives the expression of the stress change of the transition section based on the CSM model, and realizes the impact load prediction of the shield cutter when penetrating the upper-soft lower-hard composite stratum by combining the influence of the destruction of the lateral shear zone.

[0015] In combination with all the technical solutions described above, the present application has the following beneficial effects: Firstly, the present application focuses on the determination method of the impact load of the shield composite stratum, uses the cavity expansion model to divide the rock into multiple concentric circular regions, determines the damage state of the rock body at different positions and the distance position from the center of the cutter, introduces the influence of the cross-section penetration, considers the influence of the damage difference between the vertical crack zone and the dense core zone in the rock breaking process of the cutter, obtains the damage state of the cross-section of the cutter at the center of the cutter in the lower contact area of the cutter, and derives the damage distribution state of the hard rock side of the lower cutter in the vertical crack propagation process at the interface. In combination with the CSM model formula, the stress formula of the transition section of the composite rock body is obtained. On the basis of the above, the influence of the destruction of the lateral shear zone is introduced to obtain + which is closer to the actual situation. The existing domestic and foreign technologies in the field of determination of the impact load of the shield cutter in the composite stratum mostly use the CSM model based on the uniform hard rock stratum, and the present application firstly introduces the damage effect and the cavity expansion model theory on the basis of the CSM model, describes the damage evolution of the rock body below the cutter from the damage mechanics, realizes the function that the CSM model cannot realize (accurately reflects the actual stress of the cutter), fills the technical gap in the field of determination of the impact load of the shield cutter in the upper-soft lower-hard composite stratum, promotes the upgrading of the industry technology, and the commercial value is not only reflected in the direct economic benefit, but also in the improvement of the self-controllable ability of China in this field.

[0016] Second, the upper-soft and lower-hard composite stratum shield cutter impact load determination method of the application adopts a cavity expansion model to divide the rock into a plurality of concentric circular regions, determines the radius of each partition to obtain the relationship between the damage state of the rock body at different positions and the distance position of the cutter center; the influence of the cross-sectional penetration is introduced, the influence of the damage difference between the vertical crack zone and the dense core zone in the rock breaking process of the cutter is considered, the damage state of the cutter cross section at the lower contact area of the cutter is obtained, and the damage distribution state of the lower hard rock side of the cutter in the vertical crack propagation process at the interface is derived. The application deduces the expression of the stress change of the transition section based on the CSM model, and combines the influence of the lateral shear zone damage to deduce the impact load prediction formula when passing through the composite stratum, thereby providing theoretical guidance for the determination of the impact load of the large-diameter shield when passing through the composite stratum in actual engineering.

[0017] Considering the compatibility with the existing cutter uniform rock mass stress theoretical model, the dynamic change of the cutter stress at the interface of the composite stratum in the application is based on the CSM model used in the uniform hard rock stratum. By analyzing the influence of system deformation and composite rock damage on the pressure distribution and penetration of the lower part of the cutter, a composite stratum cutter impact load prediction model is constructed, the compatibility of the prediction model with the actual situation is improved, the impact of the cutter on the soft and hard interface is reduced, and the abnormal damage rate of the cutter is reduced. The application analyzes the impact load of the shield cutter in the upper-soft and lower-hard composite stratum by theoretical analysis and deduction, and can predict the impact load and distribution law of the cutter when the cutter cuts the soft and hard interface of the upper-soft and lower-hard composite stratum.

[0018] Third, the application can provide accurate theoretical guidance for the determination of the impact load of the large-diameter shield when passing through the upper-soft and lower-hard composite stratum in actual engineering, reduce the cost of equipment maintenance and replacement caused by excessive wear and damage of the cutter, and reduce the loss caused by construction delay. From the commercial value, it promotes the upgrading of the composite stratum cutter impact load prediction technology in the field of tunnel construction, improves the self-controlling ability of China in this field, helps the application and promotion of related technologies and equipment in domestic and foreign engineering, and has a broad market prospect.

[0019] Fourth, the existing domestic and foreign technologies in the field of composite stratum shield cutter impact load determination are mostly based on the CSM model of uniform hard rock stratum, and the application first introduces the theories of damage mechanics and cavity expansion model based on the CSM model, describes the damage evolution of the lower part of the cutter from the perspective of damage mechanics, perfects the CSM model, and fills the technical gap in the determination method of the impact load of the shield cutter in the upper-soft and lower-hard composite stratum.

[0020] Fifth, the problem of abnormal damage of cutter caused by interface impact in composite stratum has long restricted the safe and efficient construction of large-diameter shield, and the traditional model has large prediction error in composite stratum and does not consider the directionality of interface crack propagation. The present application realizes the accurate prediction of the impact load of the cutter in the complex stratum by innovative method, solving this difficult problem. There is a technical bias in the industry to establish a cutter stress prediction model based on homogeneous stratum conditions, which ignores the large difference between the damage mechanism of composite stratum rock mass and homogeneous stratum. The present application breaks this bias and proposes a special impact load determination method for the characteristics of the upper-soft lower-hard composite stratum. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and serve to explain the principles of the present disclosure, together with the description; Figure 1 is a flow chart of the upper-soft lower-hard composite stratum shield cutter impact load determination method provided by the embodiment of the present application; Figure 2 is a principle diagram of the upper-soft lower-hard composite stratum shield cutter impact load determination method provided by the embodiment of the present application; Figure 3 is a schematic diagram of the composite stratum cutter rock breaking mechanical model provided by the embodiment of the present application (a diagram is a x-axis phase plane schematic diagram; b diagram is a y-axis phase plane schematic diagram); Figure 4 is a schematic diagram of the composite stratum cutter rock breaking cavity expansion model provided by the embodiment of the present application (a diagram is a model partition schematic diagram; b diagram is a partition schematic diagram when the cutter is close to the interface); Figure 5 is a stress change diagram of the lower part of the composite stratum cutter provided by the embodiment of the present application; Figure 6 is a comparison diagram of the normal force of the cutter provided by the embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application, therefore the present application is not limited by the specific implementation disclosed below.

[0023] The innovation of this invention lies in the fact that it introduces damage action and cavity expansion model theories on the basis of the CSM model for the first time. It describes the failure evolution of the rock mass below the cutter from the perspective of damage mechanics, and incorporates the influence of cross-sectional penetration when calculating the damage distribution. Based on the difference in damage between the vertical crack zone and the dense core zone during the cutter's rock-breaking process, it determines the damage state of the cutter cross-section at the distance from the cutter's center within the contact area below the cutter, and obtains the damage distribution state of the hard rock side below the cutter during the vertical crack propagation process at the interface. Furthermore, by combining the influence of the cutter's shear zone failure, it achieves a function that the CSM model could not realize (accurately reflecting the actual force magnitude and distribution law of the cutter).

[0024] Example 1, such as Figure 1 As shown in the embodiment of the present invention, the method for determining the cutterhead impact load of a shield tunneling machine in a composite stratum with soft upper and hard lower formations includes the following steps: S1, using a cavity expansion model, the rock is divided into multiple concentric circular regions, the radius of each region is determined, and the relationship between the damage state of the rock mass at different locations and the distance from the center of the cutting edge is obtained; S2, Introducing the influence of cross-sectional penetration, based on the difference in damage between the vertical crack zone and the dense core zone during the rock breaking process of the cutter, the damage state of the cutter cross-section at the distance from the center of the cutter edge within the lower contact area of ​​the cutter is determined, and the damage distribution state of the lower hard rock side of the cutter during the vertical crack propagation process at the interface is obtained. S3, based on the CSM model, derives an expression for the stress change in the transition section and, combined with the influence of lateral shear zone failure, realizes the prediction of impact load when the shield cutter passes through a composite stratum of soft upper and hard lower.

[0025] Firstly, based on the cavity expansion model, the failure evolution of the rock mass under the cutter is described from the perspective of damage mechanics. The determination of the damage range is based on the relevant assumptions and conclusions of the cavity expansion theory. The establishment of the cavity expansion model, parameter calculation, and the formula for the damage distribution state of the rock side under the cutter are derived.

[0026] Considering the central vertical crack extends in a semi-circular pattern with a radius of curvature of [missing information]. r c When using a roller cutter to break rock, the damage and deterioration zone inside the rock mass should be consistent with the range of vertical crack propagation. A composite stratum roller cutter rock breaking mechanical model considering the damage effect should be constructed, such as... Figure 3 As shown.

[0027] As a further implementation, a cavity expansion model is constructed, dividing the soft rock region below the hob into multiple concentric circular regions from the center point of the cutter ring's cutting edge. Based on the differences in the failure mechanisms of each region, from the inside out, the regions are arranged as follows: outer radius... r d The dense core region, whose width is (2 w Keep it consistent; outer radius isr p of the crack zone, the outer radius r c of the crack zone, the outer radius r e of the elastic zone, the outermost is the undisturbed zone, the confining pressure of the rock mass at infinity σ 0, as shown in (a) of FIG. 1. Figure 4

[0028] As a further implementation, damage and failure occur inside the rock mass under the expansion of the dense core zone. According to the partition condition of the damage mechanics combined with the cavity expansion model, it is assumed that the equivalent attenuation coefficient of the rock mass has a linear relationship with the average damage and failure degree of the rock mass, and the rock mass damage changes linearly along the expansion direction, so a certain form of damage factor can be used to describe the damage state of the rock in this process, and the damage state of the soft rock mass at different positions D S ( r ) and the distance position of the center of the blade r .

[0029] (1) In the formula, the superscript S represents soft rock, H represents hard rock, T represents the composite interface, is an absolute value symbol, which represents r is a non-negative number. In the formula, represents a truncation function, when x > 0, when x < 0, . is the radius of the radial crack zone of the soft rock, is the radius of the broken zone of the soft rock.

[0030] The equivalent damage of the soft rock at different positions is obtained by averaging formula (1), see formula (2); and the relationship formula (3) between the equivalent attenuation coefficient of the soft rock mass and the damage state is further obtained from the relationship formula between the material damage and the damage state (the more serious the damage, the stronger the attenuation), as shown in (a) of FIG. 2. Figure 4

[0031] (2) (3) In the formula, is the attenuation coefficient of the broken rock mass, is the attenuation coefficient of the undisturbed intact rock mass, is the equivalent attenuation coefficient of the soft rock mass.

[0032] ​​​The model is analyzed as a plane strain problem: Based on the analysis method of plane strain problems, the radial stress inside soft rock masses is analyzed. With tangential stress Based on the equilibrium equation (4) and the stress-displacement relationship (5), its general solution is obtained as equation (6).

[0033] (4) (5) (6) In the formula, , These are the elastic modulus and Poisson's ratio of the material, respectively. For radial displacement, r s The distance between the center of the cutting edge in soft rock is denoted as C1 and C2, which are integral constants determined by the boundary conditions. According to stress boundary conditions , achievable , .in This refers to the tensile strength of soft rock. Represents the pressure of the surrounding rock at infinity; The surrounding rock pressure at infinity in soft rock; and Substituting into equation (6), based on the displacement boundary conditions of the elastic zone Obtain the radius of the elastic zone in soft rock. Radial crack zone radius Relation (7).

[0034] (7) Stress conditions in the radial crack zone , Substitute into equation (4) to obtain the stress in the radial crack zone. , Uniaxial compressive strength of soft rock; based on boundary stress continuity condition ,in, , These are the limiting approximation methods for the inner and outer radii of the interface between the radial crack zone and the fractured zone, respectively, to obtain the radius of the radial crack zone in soft rock. With the radius of the broken zone Relation (8).

[0035] (8) In the formula, For soft rock, the coefficient is related to the internal friction angle; This is the reference pressure for soft rock.

[0036] As a further implementation, the crushing zone is based on the Mohr-Coulomb strength criterion The calculation is performed, wherein the coefficient related to the uniaxial compressive strength of the rock related to the uniaxial compressive strength of the rock related to the uniaxial compressive strength of the rock , σ θ is the tangential stress, is the internal friction angle of the rock mass, c is the cohesion of the material, equation (9) is brought into equation (4), assuming that the rock inside the crushing zone generates a vertical stress p and a horizontal stress q due to yielding and failure p , the compact core zone can be approximately considered to transfer the roller penetration load in the form of hydrostatic pressure, i.e. q = p 0( p 0 is the reference pressure) according to the stress boundary conditions , the relationship between the radius of the crushing zone in soft rock and the radius of the compact core zone in hard rock equation (10) can be obtained.

[0037] (9) (10) As a further implementation, based on the geometric shapes of the various zones in soft rock in (a) of FIG. 7 and equations (7), (8), and (10), the distribution of the damage range inside the soft rock during the cutting process of the roller can be determined, and the range of the various damage zones in hard rock can be obtained based on the analysis of equations (1) to (10) after the roller completely enters the hard rock through the interface. Figure 4 When the roller gradually approaches the hard rock at the interface in the soft rock, as shown in (b) of FIG. 7, the damage disturbance zone of the soft rock will be in contact with the hard rock, and since

[0038] in the typical composite rock mass, the damage zone in the soft rock will be interrupted at the interface, and a compact core zone will be reformed in the hard rock when the roller and the hard rock are in point contact. Figure 4 As a further implementation, it is assumed that when the roller completely enters the hard rock in the pressure zone, the lower damage zone extends to the level of the uniform rock mass, and during the process, the size of the extension range is proportional to the size of the contact area of the roller length 2

[0039] entering the hard rock, and the damage distribution of the hard rock during the extension process can be obtained by combining equation (3), as shown in equation (11). L

[0040] ​​​ (11) where the superscript H denotes hard rock, is the length of the front half contact zone of the cutter, is the length of the contact zone entering hard rock, is the base damage distribution function at position r is the hard rock damage distribution function after scale transformation. When , the position parameter r is scaled by and substituted into the hard rock base damage distribution function to describe the case when the length of the front half contact zone of the cutter L exceeds the length of the contact zone entering hard rock .

[0041] Based on the above assumptions, the damage state of each point in the lower composite rock mass during the cutting process of the cutter can be completely determined.

[0042] According to the constructed force model of rock breaking by the cutter, the cross section is analyzed along the advancing direction of the cutter. As the cross section and the center of the cutting edge r increase, the cutter penetration decreases, and the contact force at the corresponding position P also decreases.

[0043] Considering the influence of the difference in damage between the vertical crack zone D and the dense core zone D during the rock breaking process of the cutter, the damage state of the cross section of the cutter at a distance r from the center of the cutting edge r >0) in the lower contact zone of the cutter can be derived. D S ( x , r ): (12) where D 、D is a parameter measured by the linear cutting test of the cutter, and its value range is related to the properties of the rock mass and the degree of crack development. Among them, the soft rock D =0.3, D =0.95, and the hard rock D =0.35, D ​​=0.95, the penetration relationship of the hob section at a distance r from the center of the cutting edge. , Where is the radius of the hob. The penetration depth of the section where the hob is located at the center of the cutting edge. For position parameters, This indicates the location of the interface between soft and hard rocks.

[0044] After the hobbing cutter fully penetrates the hard rock ( Its damage state D H ( x , r This is consistent with equation (12). When the contact zone at the lower part of the cutter is close to the interface between soft and hard rock, the vertical crack will be interrupted, such as... Figure 3 As shown in Figure (b). After contacting hard rock in the contact zone, the crack propagates again within the hard rock. The propagation law of the fracture damage zone satisfies the linear variation law assumed by equation (11). Combining equation (12), the damage distribution state of the lower hard rock side of the cutter during the vertical crack propagation process at the interface is established as follows: (13) In the formula, 、 The parameters for linear cutting tests of hard rock roller cutters are related to the properties of the rock mass and the degree of crack development. , .

[0045] As a further implementation, considering compatibility with existing homogeneous rock mass stress theory models for cutterheads, this application uses the CSM model employed in homogeneous hard rock strata to predict the dynamic changes in cutterhead stress at the composite stratum interface. By considering the influence of system deformation and composite rock mass damage on the pressure distribution and penetration depth of the cutterhead, a predictive model for the impact load on cutterheads in composite strata is constructed. The contact stress at the bottom of the CSM model is expressed as: (14) (15) (16) (17) in, φ θ is the contact angle between the cutter and the rock; C is a dimensionless coefficient. S The distance between the blades; σ c , σ t These are the rock mass compressive and tensile strengths, respectively. p s This represents the distributed contact stress at the bottom of the cutter ring; It is an integral variable used to describe the contact area from the beginning to the angular range. ψ This is the pressure distribution coefficient at the tool tip, ranging from -0.2 to 0.2, and varies with the tool tip width. T It increases with increasing size, and is generally taken as 0.1.

[0046] Based on the above analysis, the stress variation in the soft rock section is obtained by integrating the load at the bottom of the cutter. As shown in equation (18), the stress variation of the hard rock section can be obtained similarly. As shown in equation (19).

[0047] (18) (19) Considering equation (13), the force on the transition section is divided into two parts: the force of the soft rock section and the force of the intrusive hard rock section. By solving and summing the forces of the two parts separately, the force variation equation of the transition section is obtained. As shown in equation (20).

[0048] (20) In the formula, the superscript T represents the composite interface. ; .

[0049] The force changes in the transition section obtained in this aspect The invention incorporates the influence of penetration depth and considers the impact of damage differences between the vertical crack zone and the dense core zone during the rock breaking process of the roller cutter. Furthermore, it sums the force of the roller cutter penetrating the hard rock section with the force of the soft rock section, resulting in a more realistic outcome. This enhances the approximation between the formula calculation results and actual conditions, reduces calculation errors, and avoids economic losses and safety issues caused by inaccurate calculations, thus enabling this application to better serve practical engineering projects.

[0050] Secondly, the calculation of the fluctuation of the force amplitude of the roller cutter in cutting and breaking rock mainly considers the impact of the failure of the lateral shear zone.

[0051] Assuming the contact zone length between the rock-breaking cycle and the cutter head... L Consistently, as the cutter advances, the normal component provided by the shear zone continuously increases. When the load-bearing shear zone fails, this component becomes zero. Limit force equilibrium analysis of the rock mass shear zone at the cutter's central section yields the following: (twenty one) In the formula, The angle between the bottom of the shear zone and the horizontal plane. θ c The cutting edge angle of the hobbing cutter. p lThe lateral force is

[0052] According to the Mohr-Coulomb failure criterion (formula (22)), formula (21) is brought into, and formula (23) is obtained.

[0053] (22) (23) As a further implementation, according to formula (23), partial derivatives are taken The calculation can be obtained by bringing in (see formula (24)), which is brought into formula (23) to obtain the lateral force p l , as shown in formula (25). According to the contact geometry relationship between the front half contact area of the cutter and the shear zone, the normal force component provided by the shear zone is obtained F Nl , with the destruction of the shear zone F Nl The amplitude appears up and down fluctuation, generally according to the trigonometric function, the rock breaking period is consistent with the cutter contact area size, for the purpose of simplifying the calculation of rock mass parameters, the cutter centroid position is judged, and the result is formula (26).

[0054] (24) (25) (26) The above derivation process is summarized: the first aspect is to analyze the stress change process of the transition section of the composite stratum based on the cavity expansion model from the perspective of damage mechanics, and the second aspect is to consider the influence of the lateral shear zone destruction, and calculate the normal force component provided by the shear zone The result of the present application is to consider the influence of the above two aspects, and the final result is obtained by adding the formula derived according to each aspect.

[0055] According to the derivation results of the first two aspects, the stress of the transition section and the normal force caused by the destruction of the lateral shear zone are added, and the final calculation formula is established by adding formula (20) and formula (26) + .

[0056] (27) Compared to the traditional CSM cutterhead stress model (near-linear pressure distribution) in homogeneous rock strata, this final formula better reflects the nonlinear pressure distribution characteristics of the cutterhead, making the pressure distribution calculation closer to actual engineering conditions and enhancing the safety of construction under complex geological conditions. Simultaneously, it provides a reliable theoretical basis for calculating the stress state in shield tunneling, enriches and improves the theoretical analysis system for predicting shield impact loads, and lays the foundation for subsequent theoretical analysis and technological development.

[0057] Example 2: To verify the rationality and accuracy of the formula derived in this invention, the stress at the lower part of the composite stratum cutter was predicted by the formula as a function of the moving distance. During the process of the cutter moving from soft rock to hard rock, the vertical angle β of the resultant force of the cutter first increases and then decreases due to the change in the force distribution at the interface, which is consistent with the actual situation. The predicted results were compared and analyzed with the force changes at the interface of the composite stratum obtained by the linear cutting test. After introducing the failure effect of the lateral shear zone, the theoretical model of the calculation is more closely matched with the experimental results.

[0058] Example 3: The shield tunnel cutterhead impact load determination system for composite strata with soft upper and hard lower formations provided in this embodiment of the invention includes: The rock partitioning module is used to divide the rock into multiple concentric circular regions using a cavity expansion model, determine the radius of each partition, and obtain the relationship between the damage state of the rock mass at different locations and the distance from the center of the cutting edge. The damage state determination module is used to introduce the influence of cross-sectional penetration. Based on the influence of the damage difference between the vertical crack zone and the dense core zone during the cutter rock breaking process, it determines the damage state of the cutter cross-section at the distance from the center of the cutter edge within the lower contact area of ​​the cutter and the damage distribution state of the lower hard rock side of the cutter during the vertical crack propagation process at the interface. The impact load prediction module is used to determine the expression of stress change in the transition section based on the CSM model, and to predict the impact load when the shield cutter passes through the composite strata of soft upper and hard lower.

[0059] To further demonstrate the positive effects of the above embodiments, the present invention conducts the following experiments based on the above technical solutions.

[0060] The rationality and accuracy of the formula derived in this invention are verified by comparing and analyzing the predicted results with the stress changes at the interface of the composite strata obtained from the linear cutting test.

[0061] The dimensions of the cuboid rock blocks used for cutting were set to 420mm × 250mm × 250mm (length × width × height). Standard cylinders with a diameter of 50mm and a height of 100mm and standard cylinders with a diameter of 50mm and a height of 25mm were prepared from the same batch of rock blocks used for the physical parameter determination.

[0062] The soft rock and hard rock samples with a diameter of 50 mm and a height of 25 mm in the form of a semicircular cylinder are prepared, the bonding interface of the rock mass is polished and wiped to ensure that the interface is smooth and dry, about 50 g of epoxy resin and epoxy resin curing agent are mixed in a ratio of 100:3, and then the mixture is evenly applied to the joint surface of the soft rock and hard rock. After the bonding and splicing of the rock mass, the two samples are clamped using a clamp. After 24 hours of fixation to ensure that the rock samples are firmly bonded, the rock samples are used to carry out cutting tests.

[0063] During the experiment, the interface normal of the composite rock sample is perpendicular to the direction of the applied force. In addition to the composite rock sample, uniaxial compression tests and Brazilian splitting tests are performed on other samples to measure the uniaxial compressive strength, tensile strength, and elastic modulus of the rock samples. The experimental results are shown in Table 1.

[0064] Table 1: Cutting test results The rock breaking experiment uses a linear test bench for rock breaking with a rolling cutter. The vertical pressure value of the rolling cutter is measured by a strain pressure sensor located on the vertically connected guide flange, with a maximum range of 3000 kN.

[0065] The composite rock sample is clamped, and the hydraulic cylinder is adjusted to an output pressure of 8 MPa to push the rock sample box to move under the rolling cutter. The height of the rolling cutter is adjusted downward by the elevator until the bottom of the rolling cutter contacts the surface of the rock sample. When the vertical pressure value of the control system interface changes to 0.001 T, the vertical displacement of the rolling cutter is reset in the control panel, so that the vertical displacement value at this time is 0.00 mm. After adjustment, the rock is reset, and the initial penetration depth of the rolling cutter is set to -3 mm by the elevator. The movement speed of the rock sample in the horizontal direction is determined to be 350 mm / s. The total length of the composite rock sample is 500 mm (the length of the soft rock section is 250±1 mm, and the length of the hard rock section is 250±1 mm). Start the hydraulic station motor and adjust the hydraulic pressure to 16 MPa.

[0066] After cutting, the test results for this cutting test are exported, and the test result curve is shown in Figure 6 .

[0067] The stress change of the lower part of the rolling cutter during the process of passing through the interface is calculated based on the test parameters of the composite rock mass with a bonding interface A-B type, and the following formula is used: The normal force of the rolling cutter is obtained by integration, and the theoretical calculation results are compared with the rolling cutter normal force data obtained by test monitoring. The results are shown in Figure 5 , Figure 6 .

[0068] Figure 5To calculate the stress distribution obtained, which is consistent with the actual distribution, has stress concentration and the characteristics of the existence of two sides of the zero load area, in addition to the transition zone when the roller through the hard rock contact part stress concentration phenomenon is further strengthened, in the process of the roller from soft rock into hard rock roller force vertical angle β Because of the interface stress distribution changes show that first increased and then decreased, in line with the actual situation.

[0069] Figure 6 For the whole process of the roller rock breaking roller normal force test and theoretical results, the theoretical results are calculated considering only the influence of damage evolution and considering damage and lateral shear zone damage. Theoretical analysis of both sides does not consider the influence of the free interface, so there is no test result of two sides of 0. The normal load considering the influence of lateral shear zone damage at the interface ( F N + F Nl ) calculation theoretical model and test results are more close to match, which corresponds to the phenomenon of composite rock mass damage at the interface in the process of rock breaking test.

[0070] The above, only for the preferred specific embodiments of the present application, but the scope of protection of the present application is not limited to this, any skilled in the art of the technical range disclosed by the present application, within the spirit and principles of the present application, any modification, equivalent replacement and improvement, etc. should be covered within the scope of protection of the present application.

Claims

1. A method for determining a shield cutter impact load in a soft-over-hard composite stratum, characterized in that, The method comprises the following steps: S1, adopting a cavity expansion model to divide the rock into a plurality of concentric circular regions, determining the radii of the regions and obtaining the relationship between the damage state of the rock mass at different positions and the distance position of the blade center; S2, introducing the influence of the cross-sectional penetration, based on the influence of the damage difference between the vertical crack zone and the dense core zone in the rock breaking process of the cutter, determining the damage state of the cutter section at the center of the blade in the lower contact area of the cutter, and obtaining the damage distribution state of the hard rock side of the lower cutter in the vertical crack propagation process at the interface; S3, based on the CSM model, the expression of the stress change of the transition section is derived, and the impact load prediction of the shield cutter when penetrating the upper-soft lower-hard composite stratum is realized by combining the influence of the lateral shear zone damage.

2. The method according to claim 1, wherein, In step S1, in the analysis, the damage evolution of the lower rock mass of the cutter is described from the perspective of damage mechanics, the central vertical crack expands in a semicircular shape, and the expansion radius is r c , a composite stratum cutter rock breaking mechanics model based on damage influence is constructed; A cavity expansion model is constructed, and the lower soft rock region of the hob is divided into multiple concentric circular regions from the center point of the blade of the hob ring. According to the differences in the failure mechanisms of the regions, they are sequentially from inside to outside: a compact core region with a width of 2 r d ; a broken region with an outer radius of w ; and a broken region with an outer radius of r p ; outer radius r c The outer radius of the crack zone is r e The outermost radius is the undisturbed zone, with the far-field confining pressure on the rock mass σ 0; The damage and failure are generated in the rock mass under the expansion of the dense core area. According to the damage mechanics and the partition situation of the cavity expansion model, when the equivalent attenuation coefficient of the rock mass has a linear relationship with the average damage and failure degree of the rock mass, and the rock mass damage changes linearly along the expansion direction, the damage factor is used to describe the damage state of the rock in this process, and the damage state of the soft rock mass at different positions is established D S ( r ) and the distance between the blade center and the position r , the expression is wherein the superscript S denotes soft rock, is the absolute value sign, and denotes r is non-negative; denotes the Heaviside function, which is x > 0, ; and x < 0, ; is the radius of the soft rock radial crack zone, is the radius of the soft rock fracture zone.

3. The method according to claim 2, wherein Damage status at different locations of soft rock mass D S ( r Distance from the center of the blade r The relationship is averaged to obtain the equivalent damage at different locations in the soft rock. ; From the relationship between material damage and damage state, the relationship between the equivalent attenuation coefficient of soft rock mass and damage state is obtained as: wherein is the decay coefficient of the fractured rock mass, is the decay coefficient of the undisturbed intact rock mass, is the equivalent decay coefficient of the soft rock mass.

4. The method according to claim 3, wherein, In step S2, the model is analyzed according to a plane strain problem: based on the analysis method of the plane strain problem, the radial stress and the tangential stress in the soft rock body are obtained according to the balance equation and the stress-displacement relationship to obtain a general solution ; in the formula, , are the elastic modulus and the Poisson's ratio of the material respectively, is the radial displacement, r s is the distance from the center of the soft rock blade, and C1 and C2 are integral constants determined by the boundary conditions. Relationship 1: According to the stress boundary condition , , we have: , , where, is the tensile strength of the rock, represents the pressure of the surrounding rock at infinity; is the pressure of the surrounding rock at infinity; we have and into the general solution , based on the displacement boundary conditions in the elastic zone , we obtain the relationship between the radius of the elastic zone and the radius of the radial crack zone : ; Relationship 2: Stress condition in the radial crack zone , The stress in the radial crack zone is obtained by substituting the equilibrium equation into the stress condition , σr=σc(1-2rRc)1 / 2 where σc is the uniaxial compressive strength of the soft rock; and , where limr→Rc+and limr→Rc- are the limit expressions of the inner and outer radius of the interface between the radial crack zone and the fractured zone, respectively. The relationship between the radius of the radial crack zone and the radius of the fractured zone is Rc=2σcσt-σc2 where σt is the tensile strength of the soft rock. ; Relationship three: the crushing zone is based on the Mohr-Coulomb strength criterion The calculation is carried out with The coefficient related to The uniaxial compressive strength of the rock related to The uniaxial compressive strength of the rock related to The tangential stress θ The tangential stress The internal friction angle of the rock mass c The cohesion of the material; the Mohr-Coulomb strength criterion formula is brought into the equilibrium equation, when the rock inside the crushing zone produces vertical stress p and horizontal stress q because of yielding and destruction, the compact core zone is equivalent to transmitting the roller penetration load in the form of hydrostatic pressure, then p = q = p 0, p 0 is the reference pressure; according to the stress boundary condition , The relationship formula of the radius of the crushing zone and the radius of the compact core zone in soft rock is: ; The coefficient related to the internal friction angle corresponding to soft rock, The reference pressure of soft rock.

5. The method according to claim 4, wherein, In step S2, the distribution of the damage range in the soft rock during the cutting process of the roller cutter is determined based on the relationship between the geometric shape of each partition of the soft rock and the radius of the elastic zone in the soft rock the relationship between the radius of the radial crack zone and the radius of the broken zone the relationship between the radius of the radial crack zone and the radius of the dense core zone the relationship between the radius of the broken zone and the radius of the dense core zone the relationship between the radius of the broken zone and the radius of the dense core zone the relationship between the radius of the broken zone and the radius of the dense core zone the relationship between the radius of the broken zone and the radius of the dense core zone When the cutter gradually approaches the hard rock at the interface in the soft rock, the damage disturbed zone in the soft rock will contact the hard rock. In the typical composite rock mass , so the damage zone in the soft rock will be interrupted at the interface, and a dense core zone will be reformed in the hard rock when the cutter makes point contact with the hard rock. When the cutter is fully into the hard rock in the pressure zone, the lower damage zone extends to the level of the uniform rock mass, and the size of the extension range is proportional to the length of the cutter L The size of the contact area of the cutter into the hard rock The damage distribution of the hard rock in the extension process is obtained by combining the equivalent attenuation coefficient of the soft rock mass and the relationship formula of the damage state ; where the superscript H denotes hard rock, L is the length of the front half contact zone of the cutter, LH is the length of the hard rock entering contact zone, is the base damage distribution function at position r is the hard rock damage distribution function after scale transformation; when L > LH, the hard rock damage distribution is scaled by L > LH, the hard rock damage distribution is scaled by L > LH, the hard rock damage distribution is scaled by L > LH, the hard rock damage distribution is scaled by L > LH, the hard rock damage distribution is scaled by 6. The method according to claim 1, wherein, In step S2, according to the constructed roller cutter rock breaking stress model, the vertical crack zone in soft rock based on the roller cutter rock breaking process is determined and the dense core zone The impact of damage difference is derived, and the damage state of the roller cutter section at the lower contact zone of the cutter edge center r from the cutter edge center , wherein r > 0; In the formula, 、 The parameter for the linear cutting test of soft rock cutter is related to the nature of the rock mass and the degree of crack development. Among them, the soft rock = 0.3, = 0.95, hard rock = 0.35, = 0.95, the relationship between the penetration of the section where the cutter is located and the distance r from the center of the cutter edge , is the radius of the cutter, is the penetration of the section where the cutter is located at the center of the cutter edge, is the position parameter, is the position of the soft and hard rock interface.

7. The method according to claim 6, wherein, In step S2, the damage state of the cutter after it fully enters the hard rock D H ( x , r ) are consistent with D S ( x , r ), wherein ; the vertical crack will be interrupted when the lower contact area of the cutter is close to the interface between the soft and hard rocks; the fracture damage area will expand in the hard rock again after the contact area contacts the hard rock, and the expansion law satisfies the linear change law of the damage distribution assumption of the hard rock; the damage distribution state of the lower hard rock side of the cutter during the vertical crack expansion process at the interface is obtained by combining the damage state of the cutter section. In the formula, 、 The parameters for the linear cutting test of the hard rock cutter are determined, and the value range is related to the properties of the rock mass and the crack development degree. , .

8. The method according to claim 1, wherein, In step S3, the dynamic change of the force of the cutter at the interface of the composite stratum is based on the CSM model used in the uniform hard rock stratum, the influence of system deformation and composite rock damage on the pressure distribution and penetration of the lower cutter is analyzed, and a cutter impact load prediction model for composite stratum is constructed; The contact stress at the bottom of the CSM model is represented as: in, φ θ is the contact angle between the cutter and the rock; C is a dimensionless coefficient. S The distance between the blades; σ c , σ t These are the rock mass compressive and tensile strengths, respectively. p s This represents the distributed contact stress at the bottom of the cutter ring; It is an integral variable used to describe the contact area from the beginning to the angular range; ψ This is the pressure distribution coefficient at the tool tip, ranging from -0.2 to 0.2, and varies with the tool tip width. T If the increase is due to the increase in size, 0.1 should be taken first. Integrating the load at the bottom of the hob, simplifying the expression... To obtain the stress changes in the soft rock section for: Similarly, the stress change of the hard rock section is obtained is: The force of the transition section is divided into the force of the soft rock section and the force of the hard rock section, and the force variation formula of the transition section is obtained by separately solving and summing the two forces ; wherein the superscript T denotes the complex conjugate, , .

9. The method according to claim 1, wherein, In step S3, when the contact area length of each rock breaking cycle with the cutter L Consistent with the cutter advances, the normal component provided by the shear zone is constantly rising; when the shear zone is damaged, this part of the component becomes 0, and the limit stress balance state analysis of the rock shear zone of the cutter center section is obtained: In the formula, is the angle between the bottom of the shearing zone and the horizontal plane, θ c is the angle of the cutting edge of the roller cutter, p l is the lateral force; According to the Mohr-Coulomb failure criterion , we have Substituting into the Mohr-Coulomb failure criterion gives ; for partial derivative substitute into the calculation , take back lateral force ; according to the contact geometry relationship between the front half contact area of the cutter and the shear zone, the normal force component provided by the shear zone is obtained F Nl , with the destruction of the shear zone F Nl the amplitude appears up and down fluctuation; according to the characteristic of trigonometric function, the rock breaking period is consistent with the size of the cutter contact area, and through the cutter centroid position to simplify the calculation of rock mass parameters, then: According to the cavity expansion model, the stress variation process of the transition section of the composite stratum is analyzed from the damage mechanics angle, and the process of calculating the normal force component provided by the lateral shear zone based on the damage influence of the shear zone is calculated The stress of the transition section And the normal force Caused by the lateral shear zone damage is summed up to establish the final calculation formula + ; 。 10. A system for determining the impact load of shield tunnel cutterhead in composite strata with soft upper layer and hard lower layer, characterized in that, The system is used to regulate and control the upper-soft lower-hard composite stratum shield cutter impact load determination method of any one of claims 1-9, and the system comprises: A rock division module is used to divide the rock into a plurality of concentric circular regions by adopting a cavity expansion model, determine the radii of the regions and obtain the relationship between the damage state of the rock mass at different positions and the distance position of the blade center; A damage state determination module is used to introduce the influence of the cross-sectional penetration, based on the influence of the damage difference between the vertical crack zone and the dense core zone in the rock breaking process of the cutter, determine the damage state of the cutter section at the center of the blade in the lower contact area of the cutter, and obtain the damage distribution state of the hard rock side of the lower cutter in the vertical crack propagation process at the interface; An impact load prediction module is used to derive the expression of the stress change of the transition section based on the CSM model, and realize the impact load prediction of the shield cutter when penetrating the upper-soft lower-hard composite stratum by combining the influence of the lateral shear zone damage.

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