Method for predicting stratum settlement caused by curvature radius change of space curve shield

Abstract

The invention discloses a method for predicting stratum settlement caused by space curve shield based on curvature radius change, and the method comprises the following steps: S1, building a space rectangular coordinate system, and constructing a space curve shield tunnel calculation model according to the tunneling posture of a shield tunneling machine; the shield tunneling machine enters the abnormal tunneling section from the normal tunneling section, the shield tunneling machine turns right around a new rotating shaft l1 to conduct tunneling with the curvature radius Qyaw, the tunneling distance is converted into the angle of rotating around the new rotating shaft l1 by theta s, and the new rotating shaft l1 is parallel to the z-axis and intersects with the x-axis; s2, a space equation of a new rotating shaft l1 is obtained, and translation processing is conducted on the abnormal tunneling section; and S3, on the basis of three-dimensional space column coordinate transformation, soil body settlement caused by various soil body losses under the condition that the curvature radius is changed can be obtained. The method has the advantages that stratum settlement of the space curve shield caused by curvature radius change is predicted, and reference is provided for actual tunnel construction.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a method for predicting stratum settlement caused by a change in curvature radius of a space curved shield. Background Art

[0002] Shield construction has the advantages of little interference with urban ground traffic, short construction period, and adaptability to complex and changeable underground environments. It is currently the preferred construction method for urban tunnels. With the continuous development of underground space and the further improvement of tunnel selection requirements, more and more space arc shield tunnels are designed and constructed. The construction of space line shield tunnels is more difficult and the impact on the ground is more complicated. In order to ensure that the shield machine excavates according to the predetermined space axis, the attitude control requirements of the shield machine are also relatively high. These are the main problems in space line shield construction.

[0003] The main factors that affect soil settlement during shield construction are soil loss and construction load. Soil loss mainly comes from the integration gap at the shield tail, and there is also an over-excavation gap in the small radius turning section. The construction loads with greater influence include: additional front thrust, axial friction of the shield shell on the soil, and grouting pressure at the shield tail.

[0004] The deviation of shield tunneling will separate an originally complete tunnel section into a normal excavation section and an abnormal excavation section. In the case of front and back separation, the curvature radius will also change. Summary of the invention

[0005] The purpose of the present invention is to provide a method for predicting ground settlement caused by changes in the radius of curvature of a space curved shield machine based on the deficiencies of the above-mentioned prior art, to translate the abnormal excavation section as a whole, and to obtain soil settlement caused by various types of soil losses when the radius of curvature changes based on three-dimensional spatial cylindrical coordinate transformation, thereby realizing the prediction of ground settlement caused by changes in the radius of curvature of a space curved shield machine based on changes in the radius of curvature, and providing a reference for actual tunnel construction.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A method for predicting ground settlement caused by a change in curvature radius of a space curved shield tunnel, involving a large-scale, long-distance, large-section shield tunnel, the prediction method comprising the following steps:

[0008] S1: Establish a spatial rectangular coordinate system and construct a spatial curved shield tunnel calculation model based on the tunneling posture of the shield machine;

[0009] The coordinate origin O, the x-axis and the y-axis in the spatial rectangular coordinate system are all located on the surface of the earth, and the z-axis is vertically downward;

[0010] Assume that the shield machine is located at a depth of h underground, starting from the negative half-axis part of the y-axis (normal excavation section), turning right with a curvature radius Q, and the excavation distance is converted into an angle of rotation θ around the z-axis; the shield machine excavates to the xOz surface, at which time an instantaneous change in the curvature radius occurs. The shield machine enters the abnormal excavation section from the normal excavation section, and turns around the new rotation axis l1 with a curvature radius Q yaw Turn right and dig, the digging distance is converted into a rotation of θ around the new rotation axis l1 s The new rotation axis l1 is parallel to the z-axis and intersects the x-axis; the shield machine advances θ in the abnormal excavation section s Q yaw The distance ends;

[0011] S2: Get the spatial equation of the new rotation axis l1 and perform translation processing on the abnormal excavation section;

[0012] S3: Based on the three-dimensional cylindrical coordinate transformation, the soil settlement caused by various soil losses when the curvature radius changes can be obtained as follows:

[0013] The calculation formula for over-excavation clearance is:

[0014]

[0015] The calculation formula of the shield tail integration gap is:

[0016]

[0017] In the formula, G t is the shield tail integration gap; ω is the calculated over-excavation layer thickness, which is calculated by the theoretical over-excavation volume G a Multiply by the reduction factor 1 / 3 to get G a It is determined by the curvature radius Q and the shield machine excavation radius R; L is the length of the shield machine; q is the change value of the curvature radius; s z is the vertical displacement of any point in the half space caused by the spherical void with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body; s' z 'It's in z The general solution expression after the rotation axis translation of x, y, and z is modified. The specific changes are:

[0018]

[0019] Theoretical over-excavation G a The calculation formula is:

[0020]

[0021] Where, L tail =2D, D is the width of the segment.

[0022] Based on the three-dimensional mirror theory and the three-dimensional space integration method, the vertical displacement s of any point in the half space caused by the spherical gap with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body is obtained. z The calculation formula is:

[0023]

[0024] in:

[0025]

[0026] Where s is the variable on the x-axis, t is the variable on the y-axis, b and c are the upper and lower limit variables of integration, and μ is Poisson's ratio.

[0027] The spatial equation of the new rotation axis l1 is:

[0028]

[0029] The advantages of the present invention are: the abnormal excavation section is translated as a whole, and based on the three-dimensional space cylindrical coordinate transformation, the soil settlement caused by various soil losses when the curvature radius changes is obtained, thereby realizing the prediction of stratum settlement caused by the change of curvature radius of the spatial curved shield, and providing a reference for actual tunnel construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a calculation model of a space curved shield tunnel with a changed curvature radius in the present invention;

[0031] Figure 2 This is a schematic diagram of the location of the new rotation axis in the present invention. DETAILED DESCRIPTION

[0032] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0033] Example: Figure 1-2 As shown, this embodiment specifically relates to a method for predicting ground settlement caused by a change in curvature radius of a space curved shield, involving a large-scale, long-distance, large-section shield tunnel, and passing through a soil body under homogeneous multi-layer geological conditions with an arbitrary excavation axis. The prediction method mainly includes the following steps:

[0034] S1: Establish a spatial rectangular coordinate system and construct a spatial curved shield tunnel calculation model based on the tunneling posture of the shield machine.

[0035] Among them, Figure 1As shown, the coordinate origin O, x-axis and y-axis in the spatial rectangular coordinate system are all located on the surface, while the z-axis is vertically downward. Assume that the shield machine is located at a depth of h underground, starting from the negative half of the y-axis, turning right with a curvature radius Q, and the excavation distance is converted into an angle of rotation θ around the z-axis; the shield machine excavates to the xOz surface, that is, when y=0, it reaches the end point of the normal excavation surface, at which time an instantaneous change in the curvature radius occurs, and the shield machine enters the abnormal excavation section from the normal excavation section, and rotates around the new rotation axis l1 with a curvature radius Q. yaw Turn right and dig, the digging distance is converted into a rotation of θ around the new rotation axis l1 s The new rotation axis l1 is parallel to the z-axis and intersects the x-axis; the shield machine advances θ in the abnormal excavation section s Q yaw The distance ends.

[0036] S2: Obtain the spatial equation of the new rotation axis l1 and perform translation processing on the abnormal excavation section.

[0037] Among them, Figure 2 As shown in the figure, when the shield machine excavates to the end of the normal excavation section, the curvature radius changes instantaneously, and the shield machine still maintains the original basic turning posture, but the turning axis changes. The new rotation axis l1 is still parallel to the z-axis and keeps intersecting with the x-axis. The spatial rectangular coordinates of the new rotation axis l1 are:

[0038]

[0039] S3: Based on the three-dimensional cylindrical coordinate transformation, the soil settlement caused by various types of soil losses when the curvature radius changes can be obtained, which are the over-excavation gap and the shield tail integration gap.

[0040] The calculation formula for over-excavation clearance is:

[0041]

[0042] The calculation formula of the shield tail integration gap is:

[0043]

[0044] In the formula, G t is the shield tail integration gap; ω is the calculated over-excavation layer thickness, which is calculated by the theoretical over-excavation volume G a Multiply by the reduction factor 1 / 3 to get G a It is determined by the curvature radius Q and the shield machine excavation radius R; L is the length of the shield machine; q is the change value of the curvature radius; s z is the vertical displacement of any point in the half space caused by the spherical void with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body; s' z 'It's in zThe general solution expression after the rotation axis translation of x, y, and z is modified. The specific changes are:

[0045]

[0046] Theoretical over-excavation G a The calculation formula is:

[0047]

[0048] Where, L tail =2D, D is the segment width, in other words, the theoretical overbreak G a It is sufficient to cover the tail of the shield machine with 2 rings of segments.

[0049] Based on the three-dimensional mirror theory and the three-dimensional space integration method, the vertical displacement s of any point in the half space caused by the spherical gap with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body is obtained. z The calculation formula is:

[0050]

[0051] in:

[0052]

[0053] Where s is the variable on the x-axis, t is the variable on the y-axis, b and c are the upper and lower limit variables of integration, and μ is Poisson's ratio.

[0054] The beneficial effects of this embodiment are: the abnormal excavation section is translated as a whole, and based on the three-dimensional cylindrical coordinate transformation, the soil settlement caused by various soil losses when the curvature radius changes is obtained, which realizes the prediction of stratum settlement caused by the change of curvature radius of the spatial curved shield, and provides a reference for actual tunnel construction.

Claims

1. A method for predicting ground settlement caused by the change of curvature radius of a space curved shield machine, involving a large-scale, long-distance, large-section shield tunnel, characterized in that The prediction method comprises the following steps: S1: Establish a spatial rectangular coordinate system and construct a spatial curved shield tunnel calculation model based on the tunneling posture of the shield machine; The coordinate origin O, the x-axis and the y-axis in the spatial rectangular coordinate system are all located on the surface of the earth, and the z-axis is vertically downward; Assume that the shield machine is located at a depth of h underground, starting from the negative half of the y-axis, turning right with a curvature radius Q, and the excavation distance is converted into an angle of rotation θ around the z-axis; when the shield machine excavates to the xOz surface, an instantaneous change in the curvature radius occurs, and the shield machine enters the abnormal excavation section from the normal excavation section, turning right with a curvature radius Q around the new rotation axis l1. yaw Turn right and dig, the digging distance is converted into a rotation of θ around the new rotation axis l1 s The new rotation axis l1 is parallel to the z-axis and intersects the x-axis; the shield machine advances θ in the abnormal excavation section s Q yaw The distance ends; S2: Get the spatial equation of the new rotation axis l1 and perform translation processing on the abnormal excavation section; S3: Based on the three-dimensional cylindrical coordinate transformation, the soil settlement caused by various soil losses when the curvature radius changes can be obtained as follows: The calculation formula for over-excavation clearance is: The calculation formula of the shield tail integration gap is: In the formula, G t is the shield tail integration gap; ω is the calculated over-excavation layer thickness, which is calculated by the theoretical over-excavation volume G a Multiply by the reduction factor 1 / 3 to get G a It is determined by the curvature radius Q and the shield machine excavation radius R; L is the length of the shield machine; q is the change value of the curvature radius; s z is the vertical displacement of any point in the half space caused by the spherical void with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body; s' z 'It's in z The general solution expression after the rotation axis translation of x, y, and z is modified, and the specific changes are:

2. A method for predicting ground settlement caused by a change in curvature radius of a space curved shield according to claim 1, characterized in that Theoretical over-excavation G a The calculation formula is: Where, L tail =2D, D is the width of the segment.

3. The method for predicting ground settlement caused by a change in curvature radius of a space curved shield according to claim 1 is characterized in that Based on the three-dimensional mirror theory and the three-dimensional space integration method, the vertical displacement s of any point in the half space caused by the spherical gap with a radius of 1 at the midpoint (x0, y0, z0) of the elastic semi-infinite body is obtained. z The calculation formula is: in: Where s is the variable on the x-axis, t is the variable on the y-axis, b and c are the upper and lower limit variables of integration, and μ is Poisson's ratio.

4. The method for predicting ground settlement caused by a change in curvature radius of a space curved shield according to claim 1 is characterized in that The spatial equation of the new rotation axis l1 is:

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