Construction stability judgment method and construction control method for shield to pass through bead-stringed karst cave

Abstract

The invention relates to a construction stability discrimination method and a construction control method for a shield to pass through a bead-stringed karst cave, and the method comprises the steps: sequentially discriminating whether multiple layers of karst caves of the bead-stringed karst cave can form a soil arch from bottom to top, if the current layer of karst cave is discriminated to form a soil arch, judging that the whole bead-stringed karst cave can be kept stable in the construction process, and if the current layer of karst cave is discriminated to form a soil arch, judging that the whole bead-stringed karst cave is not stable; if all layers of karst caves are judged to be incapable of forming soil arches, it is judged that the bead-stringed karst caves cannot be kept stable in the construction process, and by means of the method, stability prediction of the bead-stringed karst caves in irregular shapes during shield crossing construction is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering, and in particular to a stability judgment method and a construction control method for shield tunneling through a beaded karst cave. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Under karst geological conditions, shield construction faces severe challenges, especially complex underground structures such as caves and fissures, which are prone to cause geological disasters such as ground collapse and tunnel collapse, seriously threatening construction safety and project progress. The karst filling structure in the cave is fragile, its instability is closely related to the location of the cave, and it is easily affected by external disturbances. The existing analysis methods (such as empirical formula method, etc.) are mostly aimed at single and relatively regular caves, while in some areas where caves are developed, beaded caves will be formed, and the karst fillings are unevenly distributed up and down, which significantly affects the accuracy of stability analysis and may lead to inaccurate results of karst filling stability determination, thereby increasing construction risks. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for judging the construction stability of a shield tunneling through a beaded cave and a construction control method, which can judge the stability of the filling inside the cave when the shield tunneling passes through, thereby reducing construction risks.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] The embodiment of the present invention provides a method for judging the construction stability of a shield tunnel passing through a beaded cave, comprising the following steps:

[0007] In order from bottom to top, it is judged whether the multi-layer caves can form soil arches. If the current layer of caves is judged to be able to form soil arches, it is judged that the entire beaded cave can remain stable during the construction process. If all layers of caves are judged to be unable to form soil arches, it is judged that the beaded cave cannot remain stable during the construction process. The method for judging whether the current layer of caves can form soil arches includes the following steps:

[0008] The maximum width and bottom width of the current layer of the cave are obtained, a simplified model of the cave is established according to the obtained maximum width and bottom width, and the boundary model of the cave is obtained according to the simplified model of the cave.

[0009] The arch height of the assumed soil arch model is obtained according to the arch clearance of the assumed soil arch model and the friction angle of the filling material in the cave, and the final soil arch model that can be formed by shield construction is obtained according to the arch height;

[0010] The final soil arch model and the boundary model of the current layer of cave are combined to determine whether the current layer of cave can form a soil arch.

[0011] Optionally, when the current layer of karst cave is a karst cave traversed by a shield machine, the arch clearance is the distance between the current layer of karst cave and two boundary positions of the shield machine along the width direction.

[0012] Optionally, when the current layer of cave is not a cave traversed by a shield machine, the arch clearance is the width of the bottom of the current layer of cave.

[0013] Optionally, the assumed soil arch model is a three-hinged arch model in a parabolic shape.

[0014] Optionally, the simplified model of the cave is a model with a quadrilateral vertical cross-section, and correspondingly, the boundary model of the cave is a straight line model.

[0015] Optionally, if there is an intersection between the final soil arch model and the karst cave boundary model, it is determined that a stable soil arch cannot be formed in the karst cave; if there is no intersection, it is determined that a stable soil arch can be formed inside the karst cave.

[0016] Optionally, a setting coefficient is obtained according to the internal friction angle of the filling material in the cave, and the arch height is obtained according to the setting coefficient and the arch clearance. After the obtained arch height is brought into the assumed soil arch model, the final soil arch model is obtained.

[0017] Optionally, a relationship model between the set coefficient and the internal friction angle is obtained based on a critical state relationship model between horizontal force and vertical force at the arch foot of the assumed soil arch model combined with a soil limit stress calculation model at the mid-span position, and the set coefficient is obtained based on the relationship model between the set coefficient and the internal friction angle combined with the internal friction angle.

[0018] In the second aspect, an embodiment of the present invention provides a construction control method for a shield tunneling through a beaded cave. First, the construction stability judgment method for a shield tunneling through a beaded cave described in the first aspect is used to judge whether the beaded cave can remain stable during shield construction. If it can remain stable, shield crossing construction is carried out. If it cannot remain stable, the beaded cave is reinforced before the shield crossing construction, and shield crossing construction is carried out after the reinforcement is completed.

[0019] Optionally, the reinforcement method is to perform grouting reinforcement on the filling in the cave.

[0020] The beneficial effects of the present invention are as follows:

[0021] The discrimination method of the present invention can establish a boundary model of the cave by obtaining the maximum width and bottom width of each layer of the beaded cave, obtain the final soil arch model through the arch clearance and the internal friction angle of the filling in the cave, and combine the boundary model with the final geotechnical model to judge whether a stable soil arch can be formed in the cave, so as to judge the construction stability when the shield passes through the cave, realize the stability prediction of the shield passing construction of irregularly shaped beaded caves, and can effectively evaluate and predict the formation stability problems that may occur during the construction process, so as to significantly improve the construction safety, and provide a new theoretical support and technical method for tunnel construction under such complex geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 is a flow chart of the method of embodiment 1 of the present invention;

[0024] Figure 2 It is a schematic diagram of the relationship between the karst cave model and the shield machine position established in Example 1 of the present invention;

[0025] Figure 3 is a simplified schematic diagram of a karst cave model according to Embodiment 1 of the present invention;

[0026] Figure 4 is a schematic diagram of a hypothetical soil arch model according to Embodiment 1 of the present invention;

[0027] Figure 5 This is a schematic diagram of determining the stability state of the first layer of caves according to Embodiment 1 of the present invention;

[0028] Figure 6 This is a schematic diagram of determining the instability of the first layer of caves according to the first embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram of judging the stability of the second layer of caves in Example 1 of the present invention;

[0030] Figure 8 This is a schematic diagram of judging the instability of the second layer of caves in Example 1 of the present invention;

[0031] Fig. 9 This is a schematic diagram of judging the stability of the third layer of caves in Example 1 of the present invention;

[0032] Fig.10 This is a schematic diagram of judging the instability of the third layer of caves in Example 1 of the present invention;

[0033] Among them, 1. karst cave model, 2. shield machine, 3. filling material, 4. limestone, 5. assumed soil arch model. DETAILED DESCRIPTION

[0034] Example 1

[0035] This embodiment provides a method for judging the construction stability of a shield tunnel through a beaded cave. From bottom to top, it is judged whether the multiple layers of caves in the beaded cave can form a soil arch. If the current layer of caves is judged to be able to form a soil arch, it is judged that the entire beaded cave can remain stable during the construction process. If all layers of caves are judged to be unable to form a soil arch, it is judged that the beaded cave cannot remain stable during the construction process. Figure 1 As shown, the specific steps include:

[0036] Step 1: Geological survey, investigate the characteristics of karst landforms, identify bad geological bodies such as caves and underground rivers. Through drilling, seismic wave reflection and other methods, determine the distribution, scale and filling material 3 characteristics of karst, evaluate the stability of the stratum and groundwater activity; the survey results are used to optimize the shield construction plan, prevent risks such as water inrush and landslides, and improve the safety and construction efficiency of the project. In this embodiment, the stratum is limestone 4 with beaded caves, and the caves have filling materials 3.

[0037] like Figure 2-Figure 3 As shown, according to the survey results, a cave model is established. First, the cave morphology is identified. According to the identification results, a cave model is established and the cave model is simplified. In this embodiment, in the simplified cave model 1 established, the vertical cross-section of each layer of caves is a quadrilateral. According to the survey results, the maximum width of each layer of caves and the bottom width of each layer of caves in the beaded caves are obtained. According to the obtained maximum width and bottom width, a simplified model of the cave is established, and then a coordinate system is established to obtain the boundary model of the cave model.

[0038] In the cave on one side that the shield machine passes through, the origin of the coordinate system is the midpoint of the line connecting the shield machine 2 and the two intersection points 6 of the cave, and the origin of the coordinate system of the remaining layers of the cave is the midpoint of the bottom edge of the cave. The x-axis of the coordinate system is the horizontal axis, and the y-axis is the vertical axis. Since the vertical section of the cave model is a quadrilateral, the boundary model of the cave is a straight line model, and its equation is: y = kx + m.

[0039] Where x is the x-axis coordinate of any point on the boundary of the cave model, y is the y-axis coordinate of any point on the boundary of the cave, k is the slope of the cave boundary, and m is the intercept of the cave boundary.

[0040] like Figure 4 As shown, an assumed soil arch model 5 is established. It is assumed that the soil arch model 5 is a three-hinged arch model in a parabolic shape, and its equation is:

[0041]

[0042] It is assumed that the soil arch model and the boundary model of the karst cave share a coordinate system, where x is the x-axis coordinate of any point on the assumed soil arch model, y is the y-axis coordinate of any point on the assumed soil arch model, l is the arch clearance of the assumed soil arch model, and f is the arch height of the assumed soil arch model.

[0043] In a layer of caves that the shield machine passes through, l is the distance between the two intersection positions of the shield machine and the assumed soil arch model along the width direction of the cave. In the remaining layers of caves, l is the width of the bottom of the cave.

[0044] Step 2: From bottom to top, whether the multi-layer caves of the beaded cave can form soil arches is judged in turn, and whether the current layer of caves can form soil arches is judged. If the current layer of caves is judged to be able to form soil arches, it is judged that the entire beaded cave can remain stable during the construction process. If all layers of caves are judged to be unable to form soil arches, it is judged that the beaded cave cannot remain stable during the construction process. Specifically, the following steps are included:

[0045] Step 2.1 determines whether the first layer of caves can form soil arches. The first layer of caves is the current layer of caves. In this embodiment, the first layer of caves is the caves traversed by the shield machine. Through geological surveys, the internal friction angle of the filling soil in the first layer of caves can be obtained. The net distance l of the arch is the distance between the two intersection points of the shield machine and the first layer of caves, which can be obtained through the relationship between the relative positions of the shield machine and the caves.

[0046] Assume that the equation of the soil arch model is:

[0047]

[0048] Since l is obtained through geological survey, if the arch height f is determined, the equation of the final soil arch model can be determined.

[0049] According to the critical state relationship model between the horizontal force and the vertical force at the arch foot of the assumed soil arch model and the calculation model of the ultimate stress of the soil at the mid-span position, the setting coefficient A and the internal friction angle are obtained. The relationship model is based on the set coefficient A and internal friction angle The relationship model is combined with the internal friction angle to obtain the setting coefficient A.

[0050] The arch height is obtained according to the set coefficient and the arch clearance. After the obtained arch height is brought into the assumed soil arch model, the final soil arch model is obtained.

[0051] Assume that the relationship between the horizontal force and the vertical force at the arch foot of the soil arch model is:

[0052]

[0053] F h 、F vare the horizontal force and vertical force at the arch foot, respectively, and c is the cohesion of the soil filling in the cave. Taking the critical state, the critical state relationship model between the horizontal force and the vertical force at the arch foot is obtained:

[0054]

[0055] Where q is the earth pressure on the soil arch.

[0056] make

[0057] t is the thickness of the assumed soil arch model

[0058] Combining formula (1) we can get:

[0059]

[0060] The calculation model of soil ultimate stress at mid-span position is:

[0061]

[0062] The mid-span position is the center of the arch crown of the soil arch model.

[0063] Combining formula (3), formula (4), and formula (2) yields:

[0064]

[0065] Due to the internal friction angle of the soil filling in the cave Can be obtained through geological exploration, therefore, the setting coefficient A can be obtained

[0066] Since f = Al

[0067] Therefore, the arch height f can be calculated. By substituting the arch height f into the assumed soil arch model, the final soil arch model and the corresponding equation that can be formed by shield construction can be obtained.

[0068] Step 2.2: Combine the boundary model of the cave and the final soil arch model to determine whether a soil arch can be formed in the first layer of the cave. Specifically:

[0069] The final soil arch model is:

[0070] The boundary model of the cave is: y = kx + m

[0071] Combining the two equations and eliminating y, we get:

[0072]

[0073] like Figure 5-Figure 6 As shown, if Then the straight line corresponding to the equation of the boundary model in the coordinate system is parallel to or coincides with the symmetry axis of the parabola corresponding to the equation of the final soil arch model in the coordinate system. If the straight line and the parabola intersect and have only one intersection point, a stable soil arch cannot be formed.

[0074] like Then its discriminant is

[0075] when When , the straight line corresponding to the equation of the boundary model in the coordinate system and the parabola corresponding to the equation of the final soil arch model in the coordinate system have two intersection points, and a stable soil arch cannot be formed;

[0076] when When , the straight line corresponding to the equation of the boundary model in the coordinate system is tangent to the parabola corresponding to the equation of the final soil arch model in the coordinate system and has only one intersection point, so a stable soil arch cannot be formed;

[0077] when When , the straight line corresponding to the equation of the boundary model in the coordinate system and the parabola corresponding to the equation of the final soil arch model in the coordinate system are separated and have no intersection, then a stable soil arch can be formed.

[0078] In summary, if we obtain Then a soil arch can be formed, indicating that the first layer of the cave is in a stable state, and the entire beaded cave can remain stable during shield tunneling construction; if the above conditions are not met, a soil arch cannot be formed.

[0079] Step 3: If the first layer of caves cannot form a stable soil arch, it is necessary to use step 2 to determine whether the second layer of caves can form a stable soil arch. At this time, the second layer of caves is the current layer of caves. The calculation is that the arch net distance l is the width of the bottom surface of the second layer of caves. The other calculation methods are the same as step 2 and will not be repeated here.

[0080] like Figure 7-10 As shown in the figure, if the second layer of caves can form soil arches, it can be judged that the entire beaded cave can remain stable during the shield construction process. Otherwise, it is necessary to judge whether the third layer of caves can form stable soil arches.

[0081] The same method is used to determine whether the cave can form a stable soil arch layer by layer. As long as the current layer of cave calculated can form a soil arch, it is judged that the entire beaded cave can remain stable during shield construction. If all layers of caves are judged to be unable to form a soil arch, it is judged that the entire beaded cave cannot remain stable during shield construction and the cave will collapse.

[0082] The discrimination method of this embodiment proposes a method for discriminating the construction stability of shield tunneling through beaded caves based on the soil arch effect, which provides a new theoretical support and technical method for tunnel construction under such complex geological conditions. By combining the soil arch effect with the mechanical properties during the construction process, it is possible to effectively evaluate and predict the stratum stability problems that may occur during the construction process, thereby significantly improving construction safety. The discrimination method of this embodiment significantly improves construction efficiency and reduces construction costs caused by geological complexity while ensuring safety. This method provides a new theoretical basis and technical means for the stability discrimination of shield construction in karst areas, and has important application and promotion value. Especially in the increasingly complex tunnel projects, the technical route proposed in this embodiment will provide a reference for future construction practices in karst areas and help promote the overall improvement of the industry's technical level.

[0083] In a practical application of the discrimination method of this embodiment:

[0084] The distance l between the shield machine and the intersection of the cave is 6m, and the internal friction angle of the filling soil in the cave is Assume that the equation of the soil arch model is Substitute it into In, can be obtained

[0085]

[0086] That is, f = Al = 0.302 × 12 = 3.624 m

[0087] According to the simplified karst cave morphology, the slope k of the straight line corresponding to the karst cave boundary model equation is 2, and the intercept m is 2. The karst cave boundary model is a straight line: y=kx+m;

[0088] Combining the above two equations and eliminating y, we can get:

[0089] Substituting the above data into the equation, we get: 0.403x 2 -0.416x+2=0, where A=0.403, B=-0.416, C=2, we get Δ=B 2 -4AC=(-0.416) 2 -4×0.403×2=-3.05<0, the straight line and the parabola are separated and have no intersection, which meets the conditions; from this, it can be concluded that the cave can form a soil arch and the cave is in a stable state.

[0090] Example 2

[0091] The present embodiment provides a construction control method for a shield tunneling through a beaded cave. First, according to the construction stability judgment method for a shield tunneling through a beaded cave described in Example 1, it is judged whether the cave can remain stable when the shield tunneling passes through the beaded cave. If it can remain stable, the shield tunneling construction can continue. If it cannot remain stable, it is necessary to perform grouting reinforcement on the filling material in the beaded cave, and then perform the shield tunneling construction after grouting reinforcement.

[0092] The methods of shield tunneling construction and grouting reinforcement can adopt existing technologies and will not be described in detail here.

[0093] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the stability of shield tunneling through a beaded cave, characterized in that: In order from bottom to top, it is judged in turn whether the multi-layer caves of the beaded cave can form a soil arch. If the current layer of caves is judged to be able to form a soil arch, it is judged that the entire beaded cave can remain stable during the construction process. If all layers of caves are judged to be unable to form a soil arch, it is judged that the beaded cave cannot remain stable during the construction process. The method for judging whether the current layer of caves can form a soil arch includes the following steps: The maximum width and bottom width of the current layer of the cave are obtained, a simplified model of the cave is established according to the obtained maximum width and bottom width, and the boundary model of the cave is obtained according to the simplified model of the cave. The arch height of the assumed soil arch model is obtained according to the arch clearance of the assumed soil arch model and the friction angle of the filling material in the cave, and the final soil arch model that can be formed by shield construction is obtained according to the arch height; The final soil arch model and the boundary model of the current layer of cave are combined to determine whether the current layer of cave can form a soil arch.

2. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: When the current layer of karst cave is the karst cave that the shield machine passes through, the arch clearance is the distance between the current layer of karst cave and the two intersection positions of the shield machine along the width direction.

3. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: When the current layer of cave is not a cave traversed by a shield machine, the arch clearance is the width of the bottom of the current layer of cave.

4. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: The assumed soil arch model is a three-hinged arch model in a parabolic shape.

5. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: The simplified model of the cave is a model with a quadrilateral vertical cross section, and correspondingly, the boundary model of the cave is a straight line model.

6. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: If there is an intersection between the final soil arch model and the cave boundary model, it is judged that a stable soil arch cannot be formed in the cave. If there is no intersection, it is judged that a stable soil arch can be formed inside the cave.

7. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 1, characterized in that: The setting coefficient is obtained according to the internal friction angle of the filling material in the cave, and the arch height is obtained according to the setting coefficient and the arch clearance. After the obtained arch height is brought into the assumed soil arch model, the final soil arch model is obtained.

8. The method for judging the stability of shield tunneling through beaded cave construction as claimed in claim 7, characterized in that: According to the critical state relationship model between the horizontal force and the vertical force at the arch foot of the assumed soil arch model combined with the soil ultimate stress calculation model at the mid-span position, the relationship model between the setting coefficient and the internal friction angle is obtained. According to the relationship model between the setting coefficient and the internal friction angle combined with the internal friction angle, the setting coefficient is obtained.

9. A construction control method for a shield tunnel passing through a beaded cave, characterized in that: First, the method for judging the construction stability of a shield tunneling through a beaded cave as described in any one of claims 1 to 8 is used to judge whether the beaded cave can remain stable during shield construction. If it can remain stable, shield crossing construction is carried out. If it cannot remain stable, the beaded cave is reinforced before the shield crossing construction, and shield crossing construction is carried out after the reinforcement is completed.

10. A construction control method for a shield machine passing through a beaded cave as claimed in claim 9, characterized in that: The reinforcement method is to perform grouting reinforcement on the filling material in the cave.

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