JPH0447020A - Ground freezing method using heat pipe - Google Patents

Abstract

PURPOSE:To heighten efficiency by providing heat pipes in the excavating direction of an adit in the ground in the circumference of the portion to be excavated, and also by arranging the heat pipes so that they are inclined in such a way that the evaporating part side of each heat pipe becomes low. CONSTITUTION:A plurality of thermosyphon-type heat pipes 1 are embedded in the ground in the circumference of the portion where an adit D is excavated in such a way that respective evaporating part 1a side slightly become lower than condensating part 1b sides. Each condensating part 1b is projectedly extended inside a vertical shaft S, and also a cooling device 2 is fitted to the condensating part 1b. Then, the devices 2 are driven to transfer the heat in the ground absorbed by the evaporating parts 1a to the condensating part 1b for radiating heat, so that the ground G is cooled to be frozen together with the water contained in the ground, and a frozen ground F is formed in the circumference of the evaporating parts 1a. Thus, since the pipes 1 are operated in a bottom-heat mode, the ground can be efficiently frozen.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is one of the ground improvement methods, in which a heat pipe is used to cool soft ground and freeze the wood contained in the ground. This relates to a ground freezing method that prevents ground collapse due to excavation.

Conventional technology When excavating soft ground or other easily collapsible ground during concealment work, root cutting work, etc., ground improvement work is carried out prior to the excavation work to prevent the excavation wall from collapsing. There may be cases where In this ground improvement work, various ground improvement materials such as cement milk and water glass are generally injected into the soil and allowed to coagulate, and the soil in the area to be excavated is impregnated with water. The so-called ground freezing method is used to cool the ground and freeze the moisture in the ground together with the ground. In this ground freezing method, a heat pipe may be used as a means of freezing underground moisture. In this case, the heat pipe has its evaporating section buried in the ground to be excavated, and its condensing section extending to the surface.
This portion extending to the outside is cooled by a cooling device.

Therefore, in a heat pipe whose condensing part side is cooled by a cooling device, the sealed working fluid collects underground heat and evaporates in the evaporating part, which has a higher temperature than the condensing part.
The steam moves to the condensing section, where it radiates heat,
It condenses and returns to the liquid phase working fluid, which is then refluxed to the evaporation section. The hydraulic fluid inside the heat pipe then repeats the above cycle, pumping out heat from the ground, cooling the ground to below freezing, and freezing the moisture contained in the ground. As a result, the soft ground is frozen and strengthened, preventing it from collapsing during excavation. Then, excavation is carried out while the ground is frozen, and once the excavation has been completed, the excavated wall is reinforced with shoring, concrete retaining walls, etc., and the excavation is continued further.

Problems to be Solved by the Invention However, in the conventional ground freezing method described above, a hole is formed with a drill etc. in the ground to be excavated, and the evaporation part side of the heat pipe is inserted into this hole to cool the ground. Although,
When cutting roots or excavating vertical shafts, a hole is drilled diagonally downward from the excavated peripheral wall, etc., and a heat pipe is inserted into this hole with the evaporation part side facing downward (bottom heat mode). Thermosiphon heat pipes can be used because they can efficiently cool and freeze the ground in the excavated area. Since the hole is drilled in the direction of digging from the inner wall of the shaft and the heat pipe is inserted and installed, heat pipes installed at the top of the shaft are in the so-called top heat mode, where the evaporation part is higher than the condensation part. Therefore, the working fluid does not necessarily flow back sufficiently and smoothly to the evaporation section, resulting in problems such as poor freezing ability and inability to achieve uniform freezing.

This invention was made in view of the above-mentioned circumstances, and it is an object of the present invention to fully draw out the heat transport ability of the heat pipe and perform cooling efficiently in a ground freezing method using a heat pipe when excavating a side shaft. The purpose is to provide a ground freezing method that allows for

Means for Solving the Problems As a means for solving the above problems, the ground freezing method using a heat pipe of the present invention is such that when a horizontal shaft is excavated from an underground tunnel, the ground freezing around the part to be excavated is , the heat pipes are oriented in the direction of excavation of the horizontal shaft, and are arranged at an angle so that the evaporation section side at the end of each heat pipe is lower.

Operation By having the above-described structure, the ground freezing method using a heat pipe of the present invention is capable of freezing the ground around the excavated portion using the heat pipe when excavating a horizontal shaft from an underground tunnel in a substantially horizontal direction. It cools and freezes, and all heat tubes are installed so that the evaporation section at the front end of each is lower than the condensation section at the rear end. Then, the evaporation section located at a lower position of the heat I tube absorbs heat from the surrounding ground and heats the hydraulic fluid sealed inside.

The heated working fluid evaporates and rises to the condensing section as vapor, and the latent heat of vaporization is released in the condensing section, thereby smoothly operating in a so-called bottom heat mode in which heat is transferred from the evaporating section to the condensing section. In this way, by releasing the latent heat of vaporization held by the vapor of the working fluid in the condensing section, the underground heat is pumped out to the outside, cooling the ground around the heat pipe body, and Freeze the remaining water.

EXAMPLES Below, the ground freezing method using the heat pipe of this invention will be explained.
Referring to Figs. 1 and 2, an embodiment is applied to ground improvement work in which a horizontal shaft with a circular cross section is excavated almost horizontally from near the bottom of a vertical shaft formed in soft ground. I will explain.

This ground freezing method uses a plurality of thermosiphon-type heat pipes 1. After the inside of the heat pipes 1 is evacuated, a working fluid such as water, alcohol, or chlorofluorocarbons that evaporates and condenses in a target temperature range is used. It is enclosed.

When a horizontal shaft is excavated in a substantially horizontal direction from near the bottom of a vertical shaft S formed almost vertically in the soft ground G, the ground G in the portion where the horizontal shaft is excavated is first frozen. In order to freeze this ground G, a plurality of heat pipes 1 are buried in the ground around the part where the horizontal shaft is excavated so that the evaporation part 1a side of each is slightly lower than the condensation part 1b side, The condensing section 1b is extended into the shaft S, and a cooling device 2 is attached to this condensing section 1b.

The intervals at which the heat pipes 1 are installed are determined by the cooling capacity of the heat pipes 1 and the slipperiness of the ground G. In addition to arranging them approximately concentrically around the area where the side shaft is to be excavated, If the diameter is large, double or
Set up in three concentric circles. Furthermore, since a heat pipe longer than the diameter of the shaft S is used, a flexible vibe is used as a container for the heat pipe.

In addition, the inclination R of each heat pipe 1 should be as small as possible with respect to the horizontal so that the evaporation section 1a side is lower, and if the inclination is 2% or more, it will operate as a thermosiphon type heat pipe. do.

When the cooling device 2 is driven to cool the condensing section 1b of the heat pipe 1, the evaporating section 1a buried in the ground G of the heat pipe 1 becomes hotter than the condensing section 1b. As a result, the working fluid in the evaporator section 1a of the heat pipe 1 is heated and becomes vapor, which rises in the direction of the cooled condensing section 1b, contacts the peripheral wall inside the condensing section 1b, and is transported as vaporization latent heat. The heat is radiated, condensed and returned to liquid phase working fluid,
It flows downward along the peripheral wall and refluxes to the evaporation section 1a. By transporting the underground heat absorbed by the evaporation part 1a to the condensation part 1b and dissipating it, the ground G around the evaporation part 1a of the human vibrator 1 is cooled, and the ground G is cooled together with the moisture contained in the ground. After the frozen ground F is formed around the evaporation part 1a and the frozen ground F is formed in a predetermined range, excavation of the horizontal shaft is started.

As a result, even if a horizontally extending horizontal shaft is excavated, since the frozen ground F is integrally formed around the excavated portion, it is possible to reliably prevent the occurrence of cave-ins and the like.

In addition, when the evaporation section 1a of the heat pipe 1 is long, when the horizontal shaft is excavated by the length, a plurality of heat pipes 1 are connected to each evaporation section 1a in the direction of further excavation. Arrange it so that the side is lower, and as before,
By cooling the condensing part 1b with the cooling device 2, the ground G around the part where the horizontal shaft is to be excavated is frozen, and then the horizontal shaft is repeatedly excavated. can also be completed.

Effects of the Invention As explained above, the ground freezing method using a heat pipe of the present invention, when excavating a side shaft from an underground tunnel, inserts a heat pipe into the ground around the part to be excavated. The heat pipes are oriented in the excavation direction and are tilted so that the evaporation section at the end of each heat pipe is lower, and all heat pipes operate in bottom heat mode, making full use of the heat transport ability of each heat pipe. It is possible to freeze the ground efficiently.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the method of the present invention. Figure 1 is a sectional view showing the underground condition when construction is performed using the ground freezing method of this embodiment, and Figure 2 is 2 is a sectional view taken along the line ■-■ in FIG. 1. FIG. 1... Hild pipe, 1a... Evaporation part, 1
b...Condensing section, ground binding, 2...Cooling device, D...Horizontal shaft, G...Ground, S...Vertical shaft. F...Frozen

Claims (1)

[Claims] When excavating a horizontal shaft from an underground tunnel, heat pipes are placed in the ground around the excavated area, oriented in the direction of the horizontal shaft excavation, and tilted so that the evaporation section at the end of each heat pipe is lower. Ground freezing method using heat pipes.