CN107201701B

CN107201701B - Full-wall ventilation type frozen soil ventilation embankment

Info

Publication number: CN107201701B
Application number: CN201610152073.1A
Authority: CN
Inventors: 俞祁浩; 钱进; 袁昌
Original assignee: Northwest Institute of Eco Environment and Resources of CAS
Current assignee: Northwest Institute of Eco Environment and Resources of CAS
Priority date: 2016-03-17
Filing date: 2016-03-17
Publication date: 2023-07-07
Anticipated expiration: 2036-03-17
Also published as: CN107201701A

Abstract

The invention relates to a full-wall ventilation type frozen soil ventilation embankment, which comprises a semicircular groove arranged in embankment filling soil and an inverted U-shaped ventilation pipe buried on the semicircular groove and communicated with the outside. The invention changes the heat exchange mechanism of the traditional ventilation pipe, greatly improves the heat exchange efficiency of the ventilation pipe roadbed, not only effectively reduces the conditions for generating roadbed diseases through the evaporation of water, but also effectively utilizes the natural cold energy conditions of the permafrost region to the greatest extent through effective convective heat exchange regulation and control, and effectively improves the stability of the permafrost roadbed while continuously reducing the temperature of the permafrost.

Description

Full-wall ventilation type frozen soil ventilation embankment

Technical Field

The invention relates to the technical field of frozen soil engineering, in particular to a full-wall ventilation type frozen soil ventilation embankment.

Background

In permafrost areas such as Qinghai-Tibet plateau and northeast of China, thick-layer underground ice with a thickness of several meters, even more than ten meters and various forms is formed through long-term evolution, development and change. With the change of climate environment and the influence of human engineering activities, frozen soil and underground ice can be degraded and melted, so that various engineering disasters are caused, and the stability of various important engineering buildings is greatly influenced.

By adopting the measures of protecting the frozen soil engineering, the frozen soil foundation is actively cooled, which is a key way for ensuring the long-term safe operation and stability of the frozen soil engineering, and in the measures, the convection heat exchange process of the frozen soil engineering is effectively regulated and controlled, thus being one type of engineering measures important for protecting the frozen soil foundation. The measures can effectively promote the heat exchange process of the foundation and the external environment under the low-temperature environment condition in winter or at night and effectively inhibit the heat exchange process of the foundation under the high-temperature environment condition in warm seasons or daytime, thereby achieving the purposes of continuous storage of cold energy in the roadbed, continuous reduction of the frozen ground temperature and continuous enhancement of the foundation stability.

The ventilated roadbed is one of important engineering measures for protecting frozen soil in a frozen soil area for many years. However, due to different structural types and different heat exchange performances of the walls of the ventilation pipes, the whole heat exchange efficiency of the roadbed can be greatly influenced. Thus, it is also important to pay attention to and develop various technologies.

The wall-penetrating ventilation pipes (Ge Xiurun, 02139009.6) used in frozen soil engineering have a large number of ventilation holes on the pipe wall, and the air can directly exchange heat with the soil around the ventilation pipe, but the convection heat exchange effect is difficult to realize due to the smaller holes and the smaller air flow velocity in the ventilation pipe. In contrast, the air heat conductivity coefficient is only 0.027W/m.K, and the air layer retained in the hole has the heat insulation effect and reduces the heat convection effect of the ventilation pipe.

The wide roadbed structure of the ventilation block stone layer (Fang Jianhong, 201420799258.8) is limited by the air permeability of the block stone in a limited space, the air flowing process and the convection heat exchange in the block stone layer are greatly limited, and the roadbed is difficult to cool effectively.

In addition, due to the extremely severe natural environment of the Qinghai-Tibet plateau, the concrete prefabrication production of the ventilation pipe is difficult to carry out on a construction site. In contrast, the ventilation pipes produced in the areas with low altitude are mainly hollow members occupying the volume, so that the traffic per vehicle is greatly limited, thereby greatly increasing the engineering construction cost.

The Qinghai-Tibet expressway is about to face construction facing the out-of-counter of the national 'thirteen-five' strategic planning, but the frozen soil problem is more prominent in the expressway compared with the common highway and the railway. The research shows (Qihao, etc. the key problems of highway construction in the permafrost area of China are researched, china science (technical science), 2014, 44 (4): 425-432), the heat absorption strength of the highway subgrade under the same condition is more than 3 times of that of a railway due to the strong heat absorption of the black road surface, the water insulation of the asphalt road surface and the influence of preventing the water evaporation and heat dissipation, and the main heat absorption path of the subgrade is mainly concentrated at the central part of the embankment and is difficult to dissipate heat to surrounding permafrost. And the expressway has more remarkable appearance than the common expressway. When the width of the roadbed of the highway is increased by about 1 time, the heat absorption intensity of the bottom surface of the embankment is increased by about 0.6 time, and the roadbed absorbs heat to be further concentrated at the central part of the roadbed, thereby generating more obvious heat-gathering effect and causing the frozen soil to be degraded more rapidly. The thermal effect between the expressway and the frozen soil is more remarkable in the face of higher technical standards and wider highway pavements, and the more outstanding frozen soil problems and the more outstanding building technical problems can be faced when the expressway is built in the frozen soil area for many years. Due to the fundamental changes in heat transfer paths, strength, etc., successful experience obtained by the Qinghai-Tibet railways, etc., advanced techniques are difficult to directly apply in Qinghai-Tibet expressway construction.

Disclosure of Invention

The invention aims to solve the technical problem of providing a full-wall ventilation type frozen soil ventilation embankment for enhancing the convective heat transfer efficiency of a frozen soil roadbed.

In order to solve the problems, the full-wall ventilation type frozen soil ventilation embankment is characterized in that: the embankment comprises a semicircular groove arranged in embankment filling soil and an inverted U-shaped ventilation pipe buried on the semicircular groove and communicated with the outside.

The inverted U-shaped ventilation pipe is matched with the semicircular groove and is composed of a semicircular or parabolic top surface section, an inclined wall supporting section and a base section which are connected into a whole.

The height of the top surface section is 5-20 cm.

The height of the inclined wall supporting section is 0-20 cm, and the included angle between the inclined wall supporting section and the vertical line is 0-45 degrees.

The depth of the semicircular groove is 0-20 cm.

The inverted U-shaped ventilation pipe is one of prefabricated reinforced concrete precast elements, reinforced concrete cast in situ, concrete and foaming concrete.

Compared with the prior art, the invention has the following advantages:

1. and (3) changing a heat exchange mechanism.

Firstly, the original ventilation road bed convection heat exchange process of the ventilation pipe is changed, and the heat exchange process of the ventilation pipe road bed in the past is realized by heat transfer of the wall of the concrete ventilation pipe, so that indirect heat exchange between embankment filling and convection air is realized. The invention is the direct heat exchange between the filling soil and the convection air; and secondly, the heat exchange process of water evaporation and heat consumption is increased. The traditional ventilation pipe has the partition effect on the soil body, so that the water in the embankment is difficult to disperse, and the change of the heat exchange mode and the way can absorb a large amount of heat through the evaporation and phase change processes of the water. Due to drought environmental conditions of Qinghai-Tibet plateau, the heat exchange mechanism occupies a larger proportion in the whole heat exchange.

2. More remarkable heat exchange and cooling efficiency.

Firstly, the double heat exchange mechanism is changed, so that the whole heat exchange capacity of the roadbed is greatly enhanced; secondly, due to the reduction of the water content of the embankment, the heat conductivity coefficient of the soil body is increased, the heat conductivity is enhanced, and the whole heat exchange capacity of the embankment is improved substantially; the effective combination of the two aspects greatly increases the cooling efficiency of the measure.

3. And the potential engineering diseases are effectively reduced.

Engineering diseases of the frozen soil roadbed mainly comprise frost heaving and thawing, and the reasons for generating the diseases are freezing and thawing of water in the roadbed. In the original ventilation roadbed structure, the precast concrete pipeline cuts off the evaporation channel of the water in the embankment to the closed structure of the water in the embankment. The breathable structure at the bottom of the convective heat exchange enables moisture in the embankment to be effectively dispersed, so that the moisture content in the roadbed is effectively reduced, and the frost heaving and thawing disease rate can be greatly reduced.

4. The cost of engineering building materials is reduced, and the cost performance is improved.

Firstly, the reduction of the precast reinforced concrete material is about 30-40%; secondly, the reinforced concrete prefabricated parts designed by the invention have the advantage of being capable of being mutually stacked, and can greatly improve the traffic volume of a bicycle, reduce the transportation cost and simultaneously reduce the damage rate of goods. The problems of hollow structure, large occupied space, high transportation cost and high breakage rate of the conventional ventilation pipe are effectively solved. Thereby effectively reducing the cost of engineering building materials.

5. And the engineering construction period is reduced.

In the construction of the conventional precast concrete ventilation pipe, in order to ensure the stability of the buried ventilation pipe, the ventilation pipe is required to be excavated again in the compacted embankment filling soil, buried in the groove and spliced again for installation. Meanwhile, the ventilation pipe is difficult to be in close contact with surrounding soil, and the heat conduction process of the ventilation pipe and the surrounding soil is influenced. The invention can directly lay and assemble the ventilation pipe on the compacted embankment filling layer at the specified position, thereby simplifying the process and shortening the construction period.

Drawings

The following describes the embodiments of the present invention in further detail with reference to the drawings.

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a side view of the present invention.

FIG. 3 is a schematic view of the structure of the inverted U-shaped ventilation pipe according to the present invention.

Fig. 4 is a three-dimensional schematic diagram of an engineering structure in an embodiment of the invention.

In the figure: 1-embankment filling; 2-inverted U-shaped ventilation tube; 3-a top section; 4-a diagonal wall support section; 5-a base section; 6-semicircular grooves.

Detailed Description

As shown in fig. 1 to 4, the full-wall ventilation type frozen soil ventilation embankment comprises a semicircular groove 6 arranged in embankment filling 1 and an inverted U-shaped ventilation pipe 2 buried on the semicircular groove 6 and communicated with the outside.

Wherein:

the inverted U-shaped ventilation pipe 2 is matched with the semicircular groove 6 and is composed of a semicircular or parabolic top surface section 3, an inclined wall supporting section 4 and a base section 5 which are connected into a whole. The height of the top surface section 3 is 5-20 cm. The height of the inclined wall supporting section 4 is 0-20 cm, and the included angle between the inclined wall supporting section and the vertical line is 0-45 degrees.

The inverted U-shaped ventilation pipe 2 is one of prefabricated reinforced concrete precast elements, reinforced concrete cast in situ, concrete and foaming concrete.

The depth of the semicircular groove 6 is 0-20 cm.

Specific application example 1 of the present invention:

the method comprises the steps of directly layering and paving natural ground surfaces in permafrost areas according to the thickness of 0.3-0.5 m, and compacting embankment filling 1 to the height of 1.5 m.

The land is leveled, and the compaction degree of the embankment filling 1 is compacted to 0.95 by using a vibrating press.

And thirdly, constructing the ventilation semicircular grooves 6 according to the distance of 100 cm. The method comprises the following steps of sequentially impacting to a depth of 10cm along a pre-drawn construction line by using a semicircular impact hammer and perpendicular to the trend of the roadbed. Thereby forming a continuous, flat, semicircular recess 6 of depth 10 cm.

The inverted U-shaped ventilation pipe 2 with a semicircular shape and the height of 20cm and the top surface section 3 is adopted.

And fifthly, paving and sequentially splicing the inverted U-shaped ventilation pipes 2 mechanically or manually. Meanwhile, the bottom of the inverted U-shaped ventilation pipe 2 extends out of two sides of the embankment filling 1 by 20cm. Thereby completing the installation of one of the inverted U-shaped ventilation pipes 2. Thereby, the installation of the reverse U-shaped ventilation pipe 2 in the whole construction section is completed.

According to the conventional construction procedure, filling and pushing the embankment filling 1 are carried out at one end of the inverted U-shaped ventilation pipe 2 at the whole construction section. To secure the inverted U-shaped ventilation tube 2, the fill control thickness of this time was 50cm. Then leveling, and vibrating rolling. And then carrying out subsequent engineering construction according to the conventional method.

Specific application example 2 of the present invention:

and the construction of the step is not needed. The installation of the inverted U-shaped ventilation tube 2 is directly performed. And then carrying out subsequent construction according to the conventional sequence. Thereby further improving the working efficiency.

Claims

1. Full wall ventilation formula frozen soil ventilation embankment, its characterized in that: the embankment comprises a semicircular groove (6) arranged in embankment filling soil (1) and an inverted U-shaped ventilation pipe (2) buried on the semicircular groove (6) and communicated with the outside; the inverted U-shaped ventilation pipe (2) is matched with the semicircular groove (6) and is composed of a semicircular or parabolic top surface section (3), an inclined wall supporting section (4) and a base section (5) which are connected into a whole; the inverted U-shaped ventilation pipe (2) is of a bottom opening structure.

2. The full wall ventilated and ventilated frozen soil ventilated embankment according to claim 1, characterized in that: the height of the top surface section (3) is 5-20 cm.

3. The full wall ventilated and ventilated frozen soil ventilated embankment according to claim 1, characterized in that: the height of the inclined wall supporting section (4) is 0-20 cm, and the included angle between the inclined wall supporting section and the vertical line is 0-45 degrees.

4. The full wall ventilated and ventilated frozen soil ventilated embankment according to claim 1, characterized in that: the depth of the semicircular groove (6) is 0-20 cm.

5. The full wall ventilated and ventilated frozen soil ventilated embankment according to claim 1, characterized in that: the inverted U-shaped ventilation pipe (2) is one of prefabricated reinforced concrete precast products, reinforced concrete cast in situ, concrete and foaming concrete.