KR101673322B1 - Soft ground improvement method with air hammering - Google Patents

Abstract

The present invention relates to a method for improving soft ground, comprising the steps of: placing a vertical drainage material on a soft ground, connecting the vertical drainage material to a horizontal pipe installed on the upper part, and connecting a vacuum pump and an air inlet valve to the horizontal pipe; A second step of activating the vacuum pump to transmit the vacuum pressure to the ground through the horizontal pipe and the vertical drainage and to periodically open or shut off the air inlet valve to amplify the pore water pressure in the ground; And a third step of closing the air inlet valve when the planned excess pore water pressure value is reached through the second step and maintaining the operation of the vacuum pump to dissipate the pore water pressure in the ground, The pore water pressure in the ground is amplified and dissipated in the second and third steps, and the pore water is discharged through the vertical drainage pipe and the horizontal pipe, so that settlement of the soft ground is promoted.

Description

{Soft ground improvement method with air hammering}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of improving a soft ground using a vacuum consolidation method, and more particularly, to a method of improving a soft ground by using a vacuum consolidation method, The present invention relates to a method for efficiently improving soft ground by amplifying pore water pressure and discharging pore water by dissipating generated excess pore water pressure by operating a vacuum pump.

Generally, a vertical drainage method using embankment load has been used as an improvement method for improving the strength of soft ground. However, the conventional embankment loading method causes the shear failure of the foundation due to the rapid increase of the ground shear stress when the overburden load is applied. In order to prevent this, the embankment load is applied step by step over a long period of time. However, it has various problems such as the extension of the construction period due to the long - term loading, labor costs, and the price of huge embankment materials.

To solve these problems, Walter Kjellman (1952) proposed a new method using atmospheric pressure instead of embankment load. In this method, a vertical drainage material is installed on a soft ground, a sand mat is installed, a gas-tight sheet is covered, and a vacuum pump is operated to use atmospheric pressure. However, this method maintains only 65-75% efficiency due to the reduction of pump efficiency due to long operation, the quality problem of the airtight sheet, and the airtightness of the airtight sheet connection part (Cortlever, NG, 2002). In addition, the existing vacuum consolidation (atmospheric pressure) method such as reduction of efficiency according to depth, decrease of vacuum pressure transmitted to the drainage material, and efficiency and applicability of large-scale ground handling decrease as the distance between pump and drainage material becomes longer Many problems are involved. Especially, in case of vacuum consolidation method, it is not possible to load more than atmospheric pressure. Therefore, it is inevitable to increase air delay and earthworks cost because embankment load must be applied to load shortage.

In addition, the bi-directional loading method (patent No. 10-2011-0026550) using vacuum pressure and positive pressure has recently been developed, but there is a limit to the excessive pore water pressure generated in the ground, and the excessive gap There are limitations such as economical efficiency and lowering of efficiency because it is necessary to establish the limit of hydraulic pressure generation, additional drainage material and system for positive pressure loading.

In the soft ground improvement method using a vacuum consolidation method, the air inflow valve is repeatedly opened and closed in a very short time during the operation of the vacuum pump so that an air impact is applied to the ground, To provide a method for improving the soft ground in a short period of time by increasing the effective stress by dissipating the generated excess pore water pressure after the excessive pore water pressure is induced.

According to an aspect of the present invention, there is provided a method of improving soft ground, comprising the steps of: placing a vertical drainage material in a soft ground; connecting the vertical drainage material to a horizontal pipe installed at an upper portion; A first step of joining and installing; A second step of activating the vacuum pump to transmit the vacuum pressure to the ground through the horizontal pipe and the vertical drainage and to periodically open or shut off the air inlet valve to amplify the pore water pressure in the ground; And a third step of closing the air inlet valve when the planned excess pore water pressure value is reached through the second step and maintaining the operation of the vacuum pump to dissipate the pore water pressure in the ground, The pore water pressure in the ground is amplified and dissipated in the second and third steps, and the pore water is discharged through the vertical drainage and the horizontal piping, thereby promoting the settlement of the soft ground. .

According to the constitution of the present invention, it is possible to overcome the problem of shearing failure due to environmental damage and embankment by replacing the embankment pressure in the conventional embankment with the vacuum pressure, and the pore water pressure amplified by the air impact is reduced It is eco-friendly and economical because it can replace the effect of load.

In addition, the present invention improves the drainage performance even in the hardening area by applying the air impact in addition to the vacuum pressure in the ground, thereby improving the soft ground in a short period of time without being affected by the depth and the distance to the drainage material.

1 is a cross-sectional view showing an implementation concept of a soft ground improvement method using an air impact according to the present invention.
2 is a cross-sectional view illustrating another embodiment of the method for improving the soft ground using the air impact according to the present invention.
3 is a graph showing the theoretical concept of the method of improving the soft ground using the air impact according to the present invention.
4 (a) to 4 (c) are graphs comparing the conventional vacuum pressure applying method and the vacuum pressure applying method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments.

The present invention has been developed in order to overcome the disadvantages of the embankment load method and the vertical drainage method which were used for improving the conventional soft ground 10, and in particular, in the conventional vacuum consolidation method, When the load is needed, it is characterized by overcoming the need for additional embankment by applying air-hammering in the ground.

FIG. 1 is a cross-sectional view showing an embodiment of the improvement method of the soft ground 10 using the air impact according to the present invention, and FIG. 2 is a view showing another embodiment of the improvement method of the soft ground 10 using the air impact according to the present invention FIG. 3 is a graph showing the theoretical concept of the method of improving the soft ground 10 using the air impact according to the present invention.

The vertical drainage material 20 is buried in the soft ground 10 and the vertical drainage material 20 is connected to a horizontal pipe 30 installed in the upper part of the soft ground 10, 30 to a vacuum pump (40) and an air inlet valve (50); The vacuum pump 40 is operated so that the vacuum pressure is transmitted to the ground through the horizontal pipe 30 and the vertical drainage member 20 and at the same time the air inlet valve 50 is periodically opened or blocked to reduce the pore water pressure in the ground A second step of amplifying; And a third step of closing the air inlet valve (50) when the planned excess pore water pressure value is reached through the second step, while maintaining the operation of the vacuum pump (40) to dissipate the pore water pressure in the ground The pore water pressure in the ground is amplified and dissipated in the second and third steps so that the pore water is discharged through the vertical water pipe 20 and the horizontal pipe 30 so that the settlement of the soft ground 10 is promoted .

The first step is to install the vertical drainage material 20 on the soft ground 10 and to connect the horizontal piping 30 installed on the upper part with the connector 60. Although not shown in the drawings, The horizontal pipe 30 and the vacuum pump 40 are connected to each other by using a water collecting device of the horizontal pipe 30 and the air inlet valve 50 is installed at a part of the horizontal pipe 30.

A circular or polygonal drainage material is used as the vertical drainage material 20, and the vertical drainage material 20 is inserted into the ground of the soft ground 10 to be improved and absorbs moisture contained in the ground. At this time, an anchor is coupled to one end of the vertical drainage material 20 cut to the depth of the pouring so that it can be fixed to the ground of the soft ground 10.

Also, although not shown in the drawings, the first stage may be provided with a hermetic cap which connects the horizontal pipe 30 to the top of the vertical drainage 20.

In the second step, the vacuum pressure applied through the vacuum pump 40 is transmitted to the ground through the horizontal pipe 30, the connector 60, and the vertical drainage 20, and a plurality of air And repeatedly opening and closing the inflow valve 50. That is, the process of opening and closing the air inlet valve 50 which was closed when the vacuum pump 40 is operated is repeated. At this time, when the air inlet valve 50 is opened / closed in a very short time, air-hamming occurs and the pore water pressure in the ground is amplified.

The air inlet valve 50 is connected to the horizontal pipe 30 to regulate the inflow of air and serves to apply the air pressure in the ground through the vertical drainage 20 in a short period.

At this time, instead of the air inflow valve 50, the present invention may amplify excess pore water pressure in the ground by using a forced air injection device such as an air vibrator.

In addition, the second step may further include a process of amplifying the pore water pressure in the ground and discharging the pore water. In addition, the pore water pressure is increased by increasing the pressure in the ground by using the air pressure in the process of discharging the pore water with the constant total stress using the vacuum pressure, and the pore water consolidation speed can be increased.

The vacuum pump 40 is combined with the water collecting tank through which the pore water and air discharged from the vertical drainage member 20 and the horizontal pipe 30 are introduced through the water collecting pipe to make the inside of the collecting tank into a vacuum state .

As shown in <Figure 1>, the vacuum pump (40) is equipped with a controller capable of controlling the pulse pressure, so that the vacuum pressure can be adjusted according to the ground conditions and circumstances.

<Figure 1>

In this case, it is preferable that the second step opens or blocks the air inlet valve 50 at intervals of 1 to 1/60 (sec / s), and FIG. 3 and FIG. 3, The drainage effect can be improved by applying an air impact to the soft ground 10 in addition to the vacuum pressure.

<Figure 2>

<Figure 3>

That is, the present invention is repeated for a short period of time to cause the air to be inflowed / interrupted to cause an impact in the ground, and to generate excess pore water pressure in the low permeability soft ground (10). This can compensate for a load deficiency phenomenon (such as a problem of vacuum pressure loss) due to an efficiency drop occurring when only the vacuum pump 40 is used in the soft ground 10 such as a superconducting duct.

4 (a) to 4 (c) are graphs comparing a conventional vacuum pressure applying method and a vacuum pressure applying method of the present invention. FIG. 4 (a) And (c) show an improved vacuum pressure loading system according to the present invention.

More specifically, as shown in FIG. 4 (a), it can be seen that the acceleration is constant when only the vacuum pressure is applied to the ground without an additional amount of impact. In addition, as shown in Figs. 4 (b) and 4 (c), it can be seen that a change occurs in the acceleration when the vacuum pressure is changed. Here, Fig. 4 (b) shows the change of the vacuum pressure at a constant time interval (linear) and Fig. 4 (c) shows the change of the vacuum pressure temporarily. The change in the load pressure is manifested by the opening / closing of the air inlet valve in both of the above-mentioned linear / open-close type, which is formed by additionally applying an impact force by air impact.

As the improved vacuum pressure applying method is used, the present invention can solve the problem of deterioration of the drainage performance due to the occurrence of the hardening region and improve the drainage efficiency.

In the third step, the air inlet valve 50 is closed and only the vacuum pump 40 is operated to dissipate the excessive pore water pressure generated in the second step. In other words, the third step is to completely block the inflow of air when the required excess pore water pressure is generated in the preliminary stage, thereby inducing the excessive pore water pressure to dissipate. In this case, as shown in Fig. 3, the ground increases due to the increase of the effective stress by the amount of excess pore water pressure, so that the ground improvement and the ground improvement are completed.

In addition, the present invention can be constructed by adding a second step of amplifying the pore water pressure in the ground and a fourth step of repeating the third step of dissipating the pore water pressure in the ground. In this case, the fourth step may be applied when it is necessary to further improve the deduction ground.

In summary, the present invention is characterized in that a large amount of pore water contained in the ground of the soft ground 10 is drained through the permeable vertical drainage material 20 and is treated in a stabilized manner, with the vacuum pressure by the vacuum pump 40, 50), the excessive pore water pressure is generated and dissipated, thereby improving the ground effectively in a short period of time.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, the present invention is not limited to the above-described exemplary embodiments, and various modifications, additions and substitutions may be made without departing from the scope of the present invention. And the scope of the present invention is defined by the appended claims.

10: Soft ground
20: Vertical drainage
30: Horizontal piping
40: Vacuum pump
50: Air inlet valve
60: Connector

Claims (5)

In soft ground (10) improvement method,
The vertical drainage material 20 is buried in the soft ground 10 and the vertical drainage material 20 is connected to a horizontal pipe 30 installed in the upper part, and the vacuum pump 40 and the air inlet valve (50);
The vacuum pump 40 is operated so that the vacuum pressure is transmitted to the horizontal pipe 30 and the vertical drainage member 20 and the air inlet valve 50 is periodically opened or blocked so that each of the vertical A second step of amplifying the pore water pressure in the ground in the drainage material 20; And
And a third step of closing the air inlet valve (50) when the planned excess pore water pressure value is reached through the second step and maintaining the operation of the vacuum pump (40) to dissipate the pore water pressure in the ground Respectively,
In the second step, the air inlet valve 50 is opened or blocked at intervals of 1 to 1/60 (sec / s)
The pore water pressure in the ground is amplified and dissipated in the second and third steps so that the pore water is discharged through the vertical drainage material 20 and the horizontal pipe 30 so that the settlement of the soft ground 10 is promoted. Improvement of soft ground using impact method. delete The method of claim 1,
The second step comprises:
Wherein a device capable of forcibly injecting air is used in place of the air inlet valve (50). The method according to claim 1 or 3,
The second step comprises:
The method further comprising the step of amplifying the pore water pressure in the ground and discharging the pore water. The method according to claim 1 or 3,
A second step of amplifying the pore water pressure in the ground after the third step and a third step of dissipating the pore water pressure in the ground are repeatedly carried out. Improved construction method.

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