Method for preventing and treating ground collapse induced by pot cover effect of buried heat pipe

Abstract

The invention discloses a method for preventing and treating ground collapse induced by the pot cover effect of a buried heat pipe, and relates to the technical field of geotechnical engineering.The method comprises the steps that a heat radiation area of the heat pipe is analyzed, the laying position and the arc length of a water-proof and vapor-proof structural layer are determined, and the structural shape is a piece of symmetrical arc-shaped water-proof and vapor-proof geotechnical cloth. A temperature difference is formed between a high-temperature area caused by the buried geothermal pipe and a low-temperature area of a road surface, water vapor in unsaturated soil of a foundation is driven to migrate to a cold area under the ground, water returns to the high-temperature area under the action of gravity, the water content of a soil body is increased in the process, and the process is called the pot cover effect of the buried geothermal pipe. Long-time water vapor circulation action and induction of ground collapse under the action of external load are common engineering disasters. According to the method for preventing and treating the ground collapse induced by the pot cover effect of the buried heat pipe, vapor-state water on the lower layer can be prevented from migrating to the shallow foundation, and the disaster of the ground collapse induced by increase of the water content of the roadbed can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering, and in particular to a method for preventing and controlling ground collapse induced by a "pot cover effect" of a buried heat pipe. Background Art

[0002] The "pot lid effect" of buried heat pipes refers to the temperature difference between the heat source of buried heat pipes and the ground. Under the action of temperature gradient, water in the unsaturated soil near the buried heat pipes migrates from the high temperature area to the low temperature area under the ground in the form of vapor, resulting in an increase in the moisture content of the shallow foundation soil. In addition, the physical and mechanical properties of the shallow foundation soil will change under the action of external loads, causing uneven settlement of the ground and inducing engineering disasters such as ground collapse.

[0003] In the design process of buried heat pipes, measures such as increasing the thickness of the insulation layer, selecting high-quality insulation materials, designing a reasonable insulation layer structure, and selecting a suitable burial depth are usually taken, with the aim of controlling the heat loss of the buried heat pipes. However, there is always a temperature difference between the shallow soil and the soil around the buried heat pipes, which leads to the upward migration of the vapor water in the lower layer, resulting in the "pot cover effect" of the buried heat pipes. Researchers have overlooked that the "pot cover effect" of buried heat pipes is one of the causes of ground collapse. In order to solve this type of engineering disaster, it is necessary to consider the "pot cover effect" of buried heat pipes.

[0004] Based on the above analysis, the "pot cover effect" of buried heat pipes induces ground damage, which is a common engineering disaster. Traditional methods only treat the buried heat pipes themselves to reduce heat loss and protect the construction quality and safety of the pipes themselves. However, the damage to the ground caused by water vapor circulation in the shallow foundation caused by the migration of steam water is not solved.

[0005] Therefore, it is necessary to provide a method for preventing and controlling the "pot cover effect" of buried heat pipes from inducing ground collapse 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 cover effect" of buried heat pipes, which can prevent the lower layer of vapor water from migrating to the shallow foundation, ensure the safety and stability of the upper foundation structure and the ground, and avoid the disaster of ground collapse induced by increased water content of the roadbed.

[0007] To achieve the above object, the present invention provides a method for preventing and controlling ground collapse induced by the "pot cover effect" of buried heat pipes, comprising analyzing the radiation area of ​​the buried heat pipes, determining the laying position and arc length of the water-proof and vapor-proof structural layer, wherein the water-proof and vapor-proof structural layer is arranged as an arc-shaped symmetrical water-proof and vapor-proof geotextile, and specifically comprising the following steps:

[0008] 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;

[0009] 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.

[0010] 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;

[0011] 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.

[0012] Preferably, in step S1, the influence radius R 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:

[0013]

[0014] Among them, α is the thermal diffusion coefficient of the soil, t is the operating time of the buried heat pipe, and r is the radius of the buried heat pipe.

[0015] Preferably, 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;

[0016] 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 S of the water-proof and steam-proof geotextile is calculated:

[0017]

[0018] Among them, 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 vapor-proof geotextile.

[0019] Therefore, the present invention adopts the above-mentioned method for preventing and controlling the ground collapse induced by the "pot cover effect" of buried heat pipes, which has the following beneficial effects:

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

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

[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 those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0030] Example

[0031] like Figure 1As shown, the present invention provides a method for preventing and controlling the ground collapse induced by the "pot cover effect" of buried heat pipes, comprising analyzing the radiation area of ​​the buried heat pipe 4, determining the laying position and arc length of the water-proof and steam-proof structural layer, wherein the water-proof and steam-proof structural layer is arranged as an arc-shaped symmetrical water-proof and steam-proof geotextile 2, and an arc-shaped water-proof and steam-proof geotextile 2 is laid on the upper part of the temperature rise influence zone 5 to prevent the vapor water in the unsaturated soil in the high temperature zone from migrating to the lower part of the ground 1, thereby avoiding engineering disasters such as uneven settlement or collapse of the ground 1 induced by the increase in the moisture content of the shallow foundation soil; specifically comprising the following steps:

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

[0033]

[0034] Among them, α is the thermal diffusion coefficient of the soil, t is the operating time of the buried heat pipe, and r is the radius of the buried heat pipe.

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

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

[0037]

[0038] Among them, 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 vapor-proof geotextile.

[0039] S3: Determine the minimum burial depth of the buried heat pipe 4, and dig a groove with a width greater than the diameter D of the heat pipe according to the position of the buried heat pipe 4 and the diameter D of the heat pipe;

[0040] 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 4. After placing the buried heat pipe 4, backfill the original soil to the laying position of the water-proof and vapor-proof geotextile 2, and set the geotextile according to the laying parameters calculated in step S2. After the laying is completed, continue to backfill the trench with original soil to the ground and compact it.

[0041] Therefore, the present invention adopts the above-mentioned method for preventing and controlling the "pot cover effect" of buried heat pipes and inducing ground collapse, which can prevent the lower layer of vapor water from migrating to the shallow foundation and avoid the disaster of ground collapse induced by increased moisture content of the roadbed.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution 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-proof and vapor-proof structural layer, wherein the water-proof and vapor-proof structural layer is arranged as an arc-shaped symmetrical water-proof and vapor-proof 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; 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. 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.

2. A method for preventing and controlling ground collapse caused by the "pot cover effect" of buried heat pipes according to claim 1, characterized in that: In step S1, the influence radius R 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: Among them, α is the thermal diffusion coefficient of the soil, t is the operating time of the buried heat pipe, and r is the radius of the buried heat pipe.

3. A method for preventing and controlling ground collapse caused by the "pot cover effect" of buried heat pipes according to claim 1, characterized in that: 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 S of the water-proof and steam-proof geotextile is calculated: Among them, 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 vapor-proof geotextile.

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