A method for preventing and controlling ground subsidence induced by the "pot cover effect" of buried geothermal pipes

Abstract

The present invention discloses a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes, which relates to the technical field of geotechnical engineering. The method includes analyzing the heat radiation area of the hot pipes, determining the laying position and arc length of the water and vapor isolation structure layer, and the structure is a symmetric arc-shaped geotextile with water and vapor isolation properties. The temperature difference formed between the high-temperature area caused by the buried hot pipes and the low-temperature area of the road surface drives the water vapor in the unsaturated soil of the foundation to migrate to the colder area under the ground, and the water returns to the high-temperature area under the action of gravity. This process leads to an increase in the moisture content of the soil, which is called the "pot lid effect" of buried hot pipes. The long-term action of water vapor circulation and the action of external loads induce ground collapse, which is a common engineering disaster. The present invention adopts a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes, which can prevent the migration of gaseous water in the lower layer to the shallow foundation, and can avoid the disaster of ground collapse induced by the increase in the moisture content of the roadbed.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and particularly to a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes. Background Art

[0002] The "pot lid effect" of buried hot pipes refers to the phenomenon that there is a temperature difference between the heat source of the buried hot pipe and the ground. Under the action of the temperature gradient, water in the unsaturated soil near the buried hot pipe migrates from the high-temperature area to the low-temperature area under the ground in a gaseous state, resulting in an increase in the moisture content of the shallow foundation soil. Coupled with the action of external loads, it will change the physical and mechanical properties of the shallow foundation soil, thus causing uneven settlement of the ground and inducing engineering disasters such as ground collapse.

[0003] In the design process of buried hot pipes, measures such as increasing the thickness of the insulation layer, selecting high-quality insulation materials, designing a reasonable insulation layer structure, and choosing an appropriate burial depth are usually taken, aiming to control the heat loss of the buried hot pipe. However, there is always a temperature difference between the shallow soil layer and the soil around the buried hot pipe, resulting in the upward migration of the lower gaseous water and generating the "pot lid effect" of the buried hot pipe. Researchers have overlooked that the "pot lid effect" of buried hot pipes is one of the reasons for ground collapse. To solve such engineering disasters, it is necessary to consider the "pot lid effect" of buried hot pipes.

[0004] Based on the above analysis, the "pot lid effect" of buried hot pipes induces damage to the ground, which is a common engineering disaster. The traditional method only treats the buried hot pipe itself to reduce heat loss and protect the construction quality and safety of the pipeline itself. However, it does not solve the harm caused by the water vapor cycle in the shallow foundation due to the migration of gaseous water to the ground.

[0005] Therefore, it is necessary to provide a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes, which can prevent the migration of the lower gaseous water to the shallow foundation, ensure the safety and stability of the upper foundation structure and the ground, and avoid disasters such as ground collapse induced by the increase in the moisture content of the roadbed.

[0007] To achieve the above purpose, the present invention provides a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes, including analyzing the radiation area of the buried hot pipe, determining the laying position and arc length of the water and vapor isolation structure layer, and the water and vapor isolation structure layer is set as an arc-shaped symmetric water and vapor isolation geotextile, specifically including the following steps:

[0008] S1: Determine the laying parameters, calculate the influence radius of the temperature rise influence area through an empirical formula combined with construction experience, and determine the boundary of the temperature rise influence area;

[0009] S2: Determine the laying position of the water and vapor barrier geotextile. The bottom of the water and vapor barrier geotextile is set at 10 cm above the boundary of the temperature rise influence zone. The vertical distance between the bottom of the water and vapor barrier geotextile and the upper edge of the buried hot pipe is set to 50 cm, and calculate the arc length of the water and vapor barrier geotextile.

[0010] S3: Determine the minimum burial depth of the buried hot pipe. According to the position of the buried hot pipe and the diameter of the heat pipe, dig a trench wider than the diameter of the heat pipe.

[0011] S4: Set a shotcrete protective layer around the trench. A concrete cushion is provided at the bottom of the trench. Fine sand is filled between the concrete cushion and the buried hot pipe. After placing the buried hot pipe, backfill the original soil.

[0012] Preferably, in step S1, the influence radius R of the temperature rise influence zone is obtained by using an empirical formula based on the thermal diffusivity of the soil and the operation time of the buried hot pipe:

[0013]

[0014] where α is the thermal diffusivity of the soil, t is the operation time of the buried hot pipe, and r is the radius of the buried hot pipe.

[0015] Preferably, in step S2, it is determined that the projection area of the arc length S of the water and vapor barrier geotextile completely covers the projection area of the temperature rise influence zone. The width of the horizontal projection S1 of the water and vapor barrier geotextile is greater than the horizontal projection width of the temperature rise influence zone by 10 cm; the thickness of the water and vapor barrier geotextile is set to 0.2 cm;

[0016] According to the geometric relationship between the vertical distance from the bottom of the water and vapor barrier geotextile to the center of the buried hot pipe and the horizontal projection width of the water and vapor barrier geotextile, calculate the arc length S of the water and vapor barrier geotextile:

[0017]

[0018] where d is the vertical distance from the outer edge of the buried hot pipe to the lower surface of the geotextile, D is the diameter of the buried hot pipe, and S1 is the horizontal projection length of the water and vapor barrier geotextile.

[0019] Therefore, by adopting the above method for preventing the "pot lid effect" of buried hot pipes from inducing ground collapse, the present invention has the following beneficial effects:

[0020] (1) The present invention can effectively prevent the migration of the lower gaseous water to the upper foundation, ensure the safety and stability of the upper foundation structure and the ground, and provide a strong guarantee for the normal operation of urban infrastructure and the safety of people's travel.

[0021] (2) The present invention has high operability, convenient construction, and cost savings.

[0022] (3) The present invention prevents the occurrence of engineering disasters such as uneven road subsidence and collapse caused by the "pot cover effect" of buried heat pipes.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a plan view of the layout of a water-proof and steam-proof structure for preventing and controlling the ground collapse induced by the "pot cover effect" of a buried heat pipe according to the present invention;

[0025] Figure 2 It is the AA section view of the water and vapor barrier arrangement;

[0026] Description of the accompanying drawings: 1. Ground; 2. Water-proof and vapor-proof geotextile; 3. Boundary of the temperature rise influence zone; 4. Buried heat pipe; 5. Temperature rise influence zone. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0028] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0029] The words "include" or "comprises" and the like used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms "inside", "outside", "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "attachment" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Example

[0031] like Figure 1As shown in the figure, the present invention provides a method for preventing and controlling ground collapse induced by the "pot lid effect" of buried hot pipes, including analyzing the radiation area of the buried hot pipe 4, determining the laying position and arc length of the water and steam isolation structure layer, and setting the water and steam isolation structure layer as the arc-shaped symmetric water and steam isolation geotextile 2. The arc-shaped water and steam isolation geotextile 2 is laid on the upper part of the temperature rise influence area 5 to prevent the vaporous water in the unsaturated soil in the high-temperature area from migrating to the lower part of the ground 1, and engineering disasters such as uneven settlement or collapse of the ground 1 caused by the increase in the moisture content of the shallow foundation soil can be avoided. The specific steps are as follows:

[0032] S1: Determine the laying parameters, calculate the influence radius of the temperature rise influence area 5 through an empirical formula combined with construction experience, and determine the boundary 3 of the temperature rise influence area; in step S1, the influence radius R of the temperature rise influence area 5 is obtained by using the empirical formula according to the thermal diffusivity of the soil and the operation time of the buried hot pipe 4:

[0033]

[0034] where α is the thermal diffusivity of the soil, t is the operation time of the buried hot pipe, and r is the radius of the buried hot pipe.

[0035] S2: Determine the laying position of the water and steam isolation geotextile 2. As Figure 1 shown in the figure, the bottom of the water and steam isolation geotextile 2 is set at 10 cm above the boundary 3 of the temperature rise influence area, the vertical distance d between the bottom of the water and steam isolation geotextile 2 and the upper edge of the buried hot pipe 4 is set to 50 cm, and the arc length S of the water and steam isolation geotextile 2 is calculated; in step S2, it is determined that the projection area of the arc length S of the water and steam isolation geotextile 2 completely covers the projection area of the temperature rise influence area 5, and the width of the horizontal projection S1 of the water and steam isolation geotextile 2 is 10 cm greater than the horizontal projection width of the temperature rise influence area 5; the thickness of the water and steam isolation geotextile 2 is set to 0.2 cm, and the length is set to 1.7 m; ensure that the water and steam isolation geotextile 2 completely covers the range of the temperature rise influence area 5.

[0036] According to the geometric relationship between the vertical distance from the bottom of the water and steam isolation geotextile 2 to the center of the buried hot pipe 4 and the horizontal projection width of the water and steam isolation geotextile 2, the arc length S of the water and steam isolation geotextile is calculated:

[0037]

[0038] where d is the vertical distance from the outer edge of the buried hot pipe to the lower surface of the geotextile, D is the diameter of the buried hot pipe, and S1 is the horizontal projection length of the water and steam isolation geotextile.

[0039] S3: Determine the minimum burial depth of the buried hot pipe 4. According to the position of the buried hot pipe 4 and the diameter D of the heat pipe, a trench wider than the diameter D of the heat pipe is dug;

[0040] S4: A shotcrete protective layer is provided around the trench, and a concrete cushion is provided at the bottom of the trench. Fine sand is filled between the concrete cushion and the buried geothermal pipe 4. After placing the buried geothermal pipe 4, the original soil is backfilled to the laying position of the moisture-proof and vapor-proof geotextile 2. The geotextile is set according to the laying parameters calculated in step S2. After the laying is completed, the trench is continuously backfilled with the original soil to the ground and compacted.

[0041] Therefore, by adopting the above method for preventing and controlling the ground collapse induced by the "pot lid effect" of the buried geothermal pipe, the present invention can prevent the migration of the lower-layer gaseous water to the shallow foundation, and can avoid the disaster of ground collapse induced by the increase of the moisture content of the roadbed.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preventing and controlling ground collapse caused by the "pot cover effect" of buried heat pipes, characterized in that: The method includes analyzing the radiation area of ​​the buried heat pipe, determining the laying position and arc length of the water-insulating and vapor-insulating structural layer, wherein the water-insulating and vapor-insulating structural layer is arranged as an arc-shaped symmetrical water-insulating and vapor-insulating geotextile, and specifically includes the following steps: S1: Determine the laying parameters, calculate the influence radius of the temperature rise influence zone through empirical formulas combined with construction experience, and determine the boundary of the temperature rise influence zone; In step S1, the influence radius of the temperature rise influence zone is obtained by using an empirical formula according to the thermal diffusion coefficient of the soil and the operation time of the buried heat pipe. : ； in, is the thermal diffusivity of the soil, is the operating time of the buried heat pipe, is the radius of the buried heat pipe; S2: Determine the laying position of the water-proof and vapor-proof geotextile. The bottom of the water-proof and vapor-proof geotextile is set 10 cm above the boundary of the temperature rise influence zone. The vertical distance between the bottom of the water-proof and vapor-proof geotextile and the upper edge of the buried heat pipe is set to 50 cm. Calculate the arc length of the water-proof and vapor-proof geotextile. In step S2, it is determined that the projection area of ​​the arc length S of the water-proof and steam-proof geotextile completely covers the projection area of ​​the temperature rise influence zone, and the width of the horizontal projection S1 of the water-proof and steam-proof geotextile is greater than the horizontal projection width of the temperature rise influence zone by 10 cm; the thickness of the water-proof and steam-proof geotextile is set to 0.2 cm; According to the geometric relationship between the vertical distance between the bottom of the water-proof and steam-proof geotextile and the center of the buried heat pipe and the horizontal projection width of the water-proof and steam-proof geotextile, the arc length of the water-proof and steam-proof geotextile is calculated. : ； Wherein, d is the vertical distance from the outer edge of the buried heat pipe to the lower surface of the geotextile, D is the diameter of the buried heat pipe, and S1 is the horizontal projection length of the water-proof and steam-proof geotextile; S3: Determine the minimum burial depth of the buried heat pipe, and dig a groove larger than the diameter of the heat pipe according to the position of the buried heat pipe and the diameter of the heat pipe; S4: A shotcrete protective layer is set around the trench, a concrete cushion layer is set at the bottom of the trench, and fine sand is filled between the concrete cushion layer and the buried heat pipe. After the buried heat pipe is placed, the original soil is backfilled.

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