JPS648137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a sand drain pile in which a part of the sand pile is covered with a water-permeable cylinder.

(Problems and Features of the Invention) The most common sand drain pile for improving soft ground made of cohesive soil by drainage methods is one consisting only of sand piles. In addition to sand piles covered with water-permeable cylinders, sand piles that are partially covered with water-permeable cylinders are also known (Japanese Unexamined Patent Application Publication No. 1983-1999).
(See Publication No. 116824).

This known partially covered sand drain pile is economical with a small amount of covering material by covering only the outer periphery of the sand pile in the layer of clay, silt, etc. with weak binding force in soft ground with a water-permeable cylinder. However, the problem with this method is that the top and bottom of the permeable cylinder end at the boundary between a layer with weak binding force and a layer with relatively strong binding force. When a horizontal external force is applied,
Sand piles shift, constrict, or break at this boundary,
The continuity of the sand drain pile is impaired.

The present invention aims to solve this problem, and its structural features are as described in the claims.

According to experiments conducted by the present inventors, the appropriate penetration length of the end of the water-permeable cylindrical body is about 2 to 3 m, although it depends on the relationship with soil quality, pile diameter, pile length, etc.

(Specific description of the invention using drawings) In the figure, layer 1 is the entire soft ground layer to be improved, layer 2 is a layer of clay, silt, etc. with weak binding force, layer 3 is a clay layer with relatively binding force, Layer 4 is a sandstone layer of sand, mountain soil, water slag, etc. loaded on layer 1. In A, if layer 2 is on top of layer 1, B
In C, if layer 2 is in the middle of layer 1, layer 2 is in the middle of layer 1.
The case where is at the bottom of layer 1 is shown respectively.

Reference numeral 5 denotes a sand pile for a drain constructed by penetrating layer 4 and layer 1, and the outer periphery of the layer 2 portion is covered with a water-permeable cylinder 6.

The length of the permeable cylindrical body 6 is longer than the thickness of layer 2, and both ends thereof are layers adjacent to layer 2 (layer 3 and layer 4, layer 3 and layer 3, layer 3 and the lower layer of layer 1) extends inward;
It is embedded within these layers where the binding force is relatively strong. As mentioned above, the length of the embedded portion 7 is suitably about 2 to 3 m, although it depends on the relationship with soil quality, pile diameter, pile length, etc.

Next, to explain the method for constructing the above-mentioned partially covered sand drain pile, a casing of a predetermined length suspended above layer 4 has a length equal to the thickness of layer 2 plus the upper and lower penetration lengths. A pre-cut water permeable cylindrical body is inserted into the casing, and the casing is suspended by a wire at a position corresponding to the position of layer 2 and set. Sand is introduced from the upper hopper, and then, while gradually pulling out the casing, the permeable cylinder 6 is discharged from the lower end of the casing along with the sand in the layer 2, and the sand is discharged in the other layers. A pile body is formed that extends from a predetermined depth in the ground to an appropriate height on the ground surface. In addition, as a means for setting the water-permeable cylinder 6 at a predetermined position inside the casing, a funnel-shaped guide tube is fixed at a predetermined position inside the casing, and the water-permeable cylinder 6 is suspended by a wire and pulled into the casing. In addition to fitting the upper end opening edge into the gap between the inner surface of the casing and the outer surface of the guide tube, the aforementioned guide tube is fixed to the upper inner side of the casing, and the guide tube is extended downward to the lower end of the casing by its own weight. Connect the bellows pipe, connect a water-permeable cylinder to the bellows pipe at the lower end of the casing, and then lift it with a wire and hold it in a predetermined position inside the casing.The above-mentioned guide pipe is suspended inside the casing with a wire. , it is conceivable to connect a water-permeable cylinder to the guide tube at the lower end of the casing and then lift it up and hold it in a predetermined position.

(Effects of the Invention) Since the partially covered sand drain pile of the present invention is as described above, the pile body in the layer where the binding force is weak maintains its independence, and even when an external force in the horizontal direction is applied to this part, the pile body maintains its independence. Of course, there will be no displacement, constriction, or cutting at the top or bottom of the covered portion, and any displacement, constriction, or disconnection at the upper and lower ends of the covered portion will be completely prevented, and the continuity of the entire pile body will be maintained. The length of the water-permeable cylinder in the partially covered sand drain pile of the present invention is longer than that of the above-mentioned known partially covered sand drain pile, but shorter than that of the fully covered sand drain pile, so it is economical in terms of materials.

[Brief explanation of drawings]

The drawings are explanatory diagrams of the present invention, and A shows the case where the covering part is located at the top of the sand pile, B shows the case where the covering part is located in the middle part of the sand pile, and C shows the case where the covering part exists at the bottom of the sand pile. are shown respectively. In the figure, 5: sand pile, 6: permeable cylinder, 7: embedded part.

Claims (1)

[Claims] 1. The length of the permeable cylindrical body that covers the outer periphery of the layer of a sand pile constructed in soft ground where a layer of clay, silt, etc. with weak binding force exists is longer than the thickness of the layer. A partially covered sand drain pile, characterized in that the end of the permeable cylindrical body is embedded in a layer adjacent to the layer and having a relatively strong restraining force.