阅读说明：本技术 一种盾构滚刀法向切削力预测方法 (Method for predicting normal cutting force of shield hob ) 是由 张军伟 张骁 郭亮 纪佑军 李雪 于 2019-09-29 设计创作，主要内容包括：本发明公开了一种盾构滚刀法向切削力预测方法,包括以下步骤：判断盘形滚刀贯入度是否小于滚刀挤压破坏区垂直高度,若是,岩石仅发生挤压破坏,不发生剪切破坏,刀刃两侧对岩石的作用力为零,采用以下滚刀法向切削力模型对法向力进行计算：<Image he="113" wi="700" file="DDA0002221706800000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>若否,则对应计算法向力的滚刀法向切削力模型为：<Image he="81" wi="700" file="DDA0002221706800000012.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>式中,F<Sub>V1</Sub>为刀刃对挤压区岩石作用力的法向力,F<Sub>V2</Sub>和F<Sub>V3</Sub>分别为滚刀推进过程中刀刃两侧对岩石作用力的法向力,P为滚刀对剪切块的作用力。本发明用于对滚刀法向切削力进行测试时,能同时兼顾挤压和剪切破坏,进而能提升测试精度。(The invention discloses a method for predicting normal cutting force of a shield hob, which comprises the following steps: judging whether the penetration of the disc cutter is smaller than the vertical height of the extrusion damage area of the hob cutter, if so, only carrying out extrusion damage on the rock and not carrying out shearing damage, wherein the acting force of the two sides of the cutting edge on the rock is zero, and the following hob cutter normal cutting force model is adopted to calculate the normal force: if not, the hob normal cutting force model for correspondingly calculating the normal force is as follows: in the formula, F V1 Normal force of the blade against the rock in the pinch region, F V2 And F V3 Normal force of two sides of the cutting edge to rock acting force in the process of propelling the hob cutter respectively, and P is the shear block of the hob cutter pairThe force of (2). When the device is used for testing the normal cutting force of the hob, extrusion and shearing damage can be considered simultaneously, and the testing precision can be further improved.)

1. A method for predicting normal cutting force of a shield hob is characterized by comprising the following steps:

judging whether the penetration of the disc cutter is smaller than the vertical height of the extrusion damage area of the hob cutter, if so, only carrying out extrusion damage on the rock and not carrying out shearing damage, wherein the acting force of the two sides of the cutting edge on the rock is zero, and the following hob cutter normal cutting force model is adopted to calculate the normal force:

if not, the hob normal cutting force model for correspondingly calculating the normal force is as follows:

in the formula, F_V1Normal force of the blade against the rock in the pinch region, F_V2And F_V3The normal force of two sides of the cutting edge to the rock acting force in the process of the hob propulsion and the P acting force of the hob to the shear block are respectively.

2. The method for predicting the wear of the shield hob cutter according to claim 1, wherein the calculation formula of the acting force of the hob on the shear block is as follows:

wherein c is the cohesion of the rock, phi_bThe internal friction angle of the rock is beta which is half of the cutting edge angle of the hob, alpha is the included angle between the shearing plane and the horizontal plane, and psi is the friction angle between the hob and the rock.

3. The method for predicting the wear of the shield hob cutter according to claim 2, wherein the force of the hob on the shear block is derived as follows:

the calculation of the shear stress τ on the shear failure face of an approximate constant section hob follows the Moore-Coulomb failure criterion:

τ＝c+σtanφ_b；

according to the stress balance of the shear block:

and substituting the formula of stress balance of the shear block into a Morkelan-coulomb failure criterion to obtain the acting force of the hob on the shear block.

4. The method of claim 1, wherein the method comprises applying force to rock in the region of extrusion by the cutting edgeA force F_V1The specific derivation process comprises the following steps:

F_V1the calculation of (A) is as follows:

F_V1＝σ_cA；

when the penetration h of the disc cutter is smaller than the vertical height of the crushing damage area of the hob cutter, the rock is only crushed, the projection area is a function which is correspondingly increased along with the increase of the depth h, and at the moment:

wherein B is the top width of the cutting edge, r is the excessive arc radius of the cutting edge, theta is the contact angle between the hob and the rock,

when the penetration h of the disc cutter is greater than or equal to the vertical height of the damage area extruded by the hob cutter, the area of the projection area of the damage area is a fixed value, and at the moment:

F_V1≈S_ABCD·σ_c＝R sinθ(B+2r sinβ')·σ_c

wherein β' is the shear failure critical angle.

5. The method for predicting shield hob cutter wear according to claim 1,

normal force F of two sides of cutting edge to rock acting force in hob propelling process_V2And F_V3The specific derivation process comprises the following steps:

when the penetration of the disc cutter is smaller than the vertical height of the extrusion damage area of the hob, the arc blade of the cutter point only performs the extrusion damage function, the rock is not sheared and damaged, and the shearing force F_V2＝F_V3＝0；

When the penetration of the disc cutter is greater than or equal to the vertical height of the crushing area of the hob, the side of the hob with the constant cross section is acted on the rock to cause the rock to be sheared and damaged, and the shearing force F_V2＝F_V3Not less than 0, namely:

in the formula, S_hThe normal projection of the contact surface of the shearing body and the cutter is as follows:

then:

6. the method for predicting the wear of the shield hob cutter according to any one of claims 1 to 5, wherein the calculation formula of the critical angle of the rock crushing failure and shearing failure is as follows: beta' ═ pi/2- (. alpha. + psi. + phi_b)。

Technical Field

The invention relates to a shield tunnel construction technology, in particular to a method for predicting the normal cutting force of a shield hob.

Background

With the rapid expansion of population and the increase of urbanization speed, the problems of poor land resources and crowded ground traffic become more severe, and public facilities, roads and bridges have covered the ground space in a large range, so that the development of underground space and the rapid construction of urban subways are very urgent for urban construction. The shield tunneling method has the advantages of high construction speed, strong adaptability to complex stratums, less interference to surrounding environments and the like, is developed rapidly and widely applied, and increasingly becomes the preferred construction method of urban subways.

In the shield construction process, the hob installed on the cutter head is used as a main tool for excavating the stratum, and abrasion of different degrees can occur during excavation. The machine is stopped for tool changing, and the tool is checked, maintained and replaced, so that the construction efficiency, the cost and the construction safety are affected. When the shield tunneling machine encounters a sandy gravel stratum or a composite stratum in the tunneling process, the original point contact is changed into line or surface contact when the cutter acts on the pebble with large particle size, the stress surface is enlarged, and the abrasion is more serious.

In shield engineering, the common hob forms can be divided into three types: similar constant cross-section hobs, sharp-edged wedge hobs and arc-edged wedge hobs. Compared with the sections of the sharp-edge wedge and the arc-edge wedge, the constant-section hob has better effect of continuously crushing rocks under the condition of hard rock stratum. The conventional research on a hob normal cutting force model is mostly an arc-edge wedge-shaped or sharp-edge wedge-shaped section hob, the failure mechanism of rock is assumed to be single extrusion or shear failure, and the calculation result and the actual input and output are large.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a shield hob normal cutting force prediction method which is used for simultaneously considering extrusion and shearing damage when the hob normal cutting force is tested, so that the test precision can be improved.

The purpose of the invention is mainly realized by the following technical scheme: a method for predicting normal cutting force of a shield hob comprises the following steps:

judging whether the penetration of the disc cutter is smaller than the vertical height of the extrusion damage area of the hob cutter, if so, only carrying out extrusion damage on the rock and not carrying out shearing damage, wherein the acting force of the two sides of the cutting edge on the rock is zero, and the following hob cutter normal cutting force model is adopted to calculate the normal force:

if not, the hob normal cutting force model for correspondingly calculating the normal force is as follows:

in the formula, F_V1Normal force of the blade against the rock in the pinch region, F_V2And F_V3The normal force of two sides of the cutting edge to the rock acting force in the process of the hob propulsion and the P acting force of the hob to the shear block are respectively. The rock breaking force is a function related to the cutter, the rock breaking geometric shape and the rock physical properties, the cutter geometric shape refers to the diameter of a disc, the width of a cutter tip, the distance between cutters and the penetration depth, and the rock physical mechanical properties mainly comprise unconfined compressive strength and tensile strength of the rock.

Further, the calculation formula of the acting force of the hob on the shear block is as follows:

wherein c is the cohesion of the rock, phi_bThe internal friction angle of the rock is beta which is half of the cutting edge angle of the hob, alpha is the included angle between the shearing plane and the horizontal plane, and psi is the friction angle between the hob and the rock.

Further, the derivation process of the force of the hob on the shear block is as follows:

the calculation of the shear stress τ on the shear failure face of an approximate constant section hob follows the Moore-Coulomb failure criterion:

τ＝c+σtanφ_b；

according to the stress balance of the shear block:

and substituting the formula of stress balance of the shear block into a Morkelan-coulomb failure criterion to obtain the acting force of the hob on the shear block.

Further, the normal force F of the blade to the rock force of the crushing area_V1The specific derivation process comprises the following steps:

F_V1the calculation of (A) is as follows:

F_V1＝σ_cA；

when the penetration h of the disc cutter is smaller than the vertical height of the crushing damage area of the hob cutter, the rock is only crushed, the projection area is a function which is correspondingly increased along with the increase of the depth h, and at the moment:

wherein B is the top width of the cutting edge, r is the excessive arc radius of the cutting edge, theta is the contact angle between the hob and the rock,

when the penetration h of the disc cutter is greater than or equal to the vertical height of the damage area extruded by the hob cutter, the area of the projection area of the damage area is a fixed value, and at the moment:

F_V1≈S_ABCD·σ_c＝R sinθ(B+2r sinβ')·σ_c

wherein β' is the shear failure critical angle.

Further, the normal force F of two sides of the cutting edge to the rock acting force in the process of propelling the hob cutter_V2And F_V3The specific derivation process comprises the following steps:

when the penetration of the disc cutter is smaller than the vertical height of the extrusion damage area of the hob, the arc blade of the cutter point only performs the extrusion damage function, the rock is not sheared and damaged, and the shearing force F_V2＝F_V3＝0；

When the penetration of the disc cutter is greater than or equal to the vertical height of the crushing area of the hob, the side of the hob with the constant cross section is acted on the rock to cause the rock to be sheared and damaged, and the shearing force F_V2＝F_V3Not less than 0, namely:

in the formula, S_hThe normal projection of the contact surface of the shearing body and the cutter is as follows:

then:

further, the calculation formula of the critical angle of the rock crushing failure and shearing failure effect is as follows: beta' ═ pi/2- (. alpha. + psi. + phi_b)。

In conclusion, compared with the prior art, the invention has the following beneficial effects: according to the invention, stress analysis is carried out on the rock mass broken by the hob, a hob rock breaking normal force average value prediction model is established, extrusion and shearing damage can be simultaneously considered when the hob normal cutting force is tested, and the test precision can be improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic diagram of hob rock breaking in hard rock;

FIG. 2 is a schematic view of the stress of the pebbles under the action of the cutter;

FIG. 3 is a hob excavation stress analysis diagram;

FIG. 4 is a diagram of a rock breaking state of a constant-section hob;

FIG. 5 is a force analysis diagram of a blade-side shear body;

FIG. 6 is a destructive form critical point pattern;

FIG. 7 is a stress analysis diagram of a constant cross-section hob;

FIG. 8 is a normal projection view of the contact surface of the side surface of the hob and the shearing body with the approximate constant cross section;

FIG. 9 is a schematic view of the cutting edge of the hob used in the experiment;

FIG. 10 is a graph comparing experimental data with normal force of the prediction model of the present embodiment;

FIG. 11 is a graph comparing experimental data with normal force calculations for each model.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.