JPS6290438A - Soft ground improvement work - Google Patents

Abstract

PURPOSE:To prevent the exertion of adverse influence on existing structures on the surrounding ground by a method in which an air ventilator is provided near the surrounding of an improved ground in such a way as to reduce the flow of air toward the surrounding ground from the improved ground. CONSTITUTION:While a rotary shaft 3 is penetrated into a soft ground having upper and lower soft cohesive soil layers 2 between which a sand layer 1 is present, a powdery ground-improving agent is jetted, together with compressed air, from a stirring blade 4 to harden the soft ground. The used air is directed to the direction of arrows, enters an air ventilator 5, and is allowed to escape to the ground's surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a soft ground improvement method that involves discharging compressed air underground during construction.

(Problems to be solved by the invention and its characteristics) For example, a construction method in which a powder or granular soil conditioner is conveyed by compressed air and ejected into the ground, and then stirred and mixed with the ground soil using a stirring blade (Japanese Patent Publication No. 57-58493). , a construction method in which compressed air is mixed with a liquid ground hardening agent and injected into the ground, and the injection force is used to stir and mix it with the ground soil (Special Publication No. 51-849).
No. 6), a construction method in which the hollow pipe is re-penetrated while applying compressed air pressure to the sand column discharged from the lower end of the hollow pipe to create an enlarged-diameter sand pile in soft ground (Unexamined Japanese Patent Publication No. Showa 53-1458
When improving soft ground using a construction method that involves discharging compressed air into the ground during construction, such as No. This may cause damage to existing structures (houses, etc.) on the surrounding ground.

The present invention aims to provide a method for improving soft ground that can prevent the occurrence of the above-mentioned undesirable phenomenon, and the structural features thereof are as described in the claims. It is.

The air venting facility of the present invention can be installed, for example, by drilling a hole in the ground, building a perforated pipe in the center of the hole, and filling the surrounding area with filter material such as crushed stone. Therefore, it is preferable to carry out this work prior to ground improvement work.

(Description of the invention with drawings) Fig. 1 schematically shows one embodiment of the present invention, and in this case, soft ground has a sand layer 1 sandwiched therebetween and soft cohesive soil layers 2, 2 above and below. using the conventionally well-known powder injection stirring method (
A powdered ground improvement agent is transported using compressed air, squirted into the ground near the stirring blade 4 protruding from the lower end of the rotating shaft 3, and then hardened using a method of stirring and mixing with the ground soil using the stirring blade 4. It is shown that the spent air flows in the direction of arrow A (towards the periphery of the improved ground) through the highly permeable sand layer 1.

Reference numeral 5 denotes an air vent facility installed in the vicinity of the improved ground in the manner described later, and this air vent facility 5, which extends vertically through the sand layer 1 to the ground, releases the above-mentioned air to the ground and flows from the improved ground to the surrounding ground. This serves to reduce the incoming airflow.

The air vent facility 5 shown in FIGS. 2 and 3 is installed by installing a perforated pipe 6 in the center of a vertical hole bored with an auger-type drilling machine and filling the surrounding area with filter material such as crushed stone. However, the installation mode of the air venting facility 5 is not limited to this. For example, instead of the perforated pipe 6, the center may be filled with crushed stone 8 whose particle size is larger than that of the filter material 7. (See Figure 4).

(Effects of the Invention) The present invention is as described above, and is very meaningful because it allows improvement work on soft ground to be carried out in a state where the compressed air discharged into the improved ground does not have an adverse effect on the surrounding ground. It is.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of an embodiment of the present invention, Fig. 2 is a longitudinal sectional illustration of an example of an air venting facility, Fig. 3 is an enlarged sectional view of Fig. 2, and Fig. 4 is a separate cross section of the air venting facility. It is a diagram. In the figure, 5...air vent facility, 6...perforated pipe, 7...filter material...

Claims (1)

[Claims] When improving soft ground using a construction method that involves discharging compressed air into the ground during construction, an air vent facility is installed near the periphery of the improved ground to reduce air flow from the improved ground to the surrounding ground. Improved construction method.