JP2003253671A - Rotational embedding method for existing pile with less soil displacement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotational embedding method for an existing pile capable of reducing the amount of displacement soil excavated and safely and surely performing rotational embedding. <P>SOLUTION: After excavation is carried out to a predetermined depth by a pre-auger construction method, cement milk is injected to the periphery of the tip for turning the periphery of the tip into a soil cement form, and inside the excavated hole, an existing pile serving as an upper pile is arranged on an existing pile having a spiral blade at the pile tip periphery of the pile and serving as a lower pile. In the rotational embedding, a rod is arranged in a hollow part of the upper pile, and a rotational force is applied to the lower pile via the rod, so that the amount of displacement soil can be reduced in this rotational embedding method for the existing pile. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burying existing piles, and in particular, it is possible to reduce excavated soil discharged from a construction site as much as possible in consideration of the environment. The present invention relates to a method for burying existing piles that can obtain high bearing capacity after burial. More specifically, the present invention relates to a method for forming a composite structure of a ready-made pile and soil cement, which can reduce excavation and excavation during construction and can obtain a high bearing capacity after burying the existing pile. 2. Description of the Related Art Conventionally, in the method of embedding a ready-made pile, a pile tip is enlarged and excavated, and cement milk is injected into this portion.
Many pre-boring expanded root consolidation methods of embedding ready-made piles by creating expanded bulbs at the tip of the pile have been implemented (Fig. 3). However, the supporting force at the tip of the pile is smaller than that of the driving method, and it is not sufficient. For this reason, an ST pile (Fig. 4) in which only the tip of the pile has a large diameter or a knotted pile having a convex portion around the tip of the pile is used.
A method (FIG. 5) has been proposed in which the supporting force is increased by also adding the peripheral frictional force near the tip of the pile. However, in this method, the pile outer diameter has a convex part and a large diameter part, so in order to bury the pile by the embedded pile method, the excavation hole is excavated over the entire length of the pile with a diameter larger than the diameter of the large diameter part of the pile. It is necessary to remove as much as possible from the inside of the drilling hole and to fluidize the inside of the drilling hole and soften it in order to bury the pile, so the construction machine becomes large, and when drilling, drilling liquid such as a lot of water and bentonite muddy water It was necessary to fluidize while injecting cement milk. As a result, a large amount of earth and sand is discharged at the time of excavation and pile burial, and these are industrial wastes, and therefore have many environmental problems. Further, Japanese Patent Application Laid-Open No. Sho 60-2
No. 38515 proposes a method in which a pile provided with a spiral wing at the tip of the pile is rotationally penetrated and embedded into a pile burial hole filled with soil-consolidated cement milk to enhance pile supporting capacity. However, in this method, since the pile head is rotated and settled by applying a rotational force to the pile head, a large rotational torque is generated in the pile if the ground is hard, which may cause the pile body to be cut off in the case of a concrete pile. There was a problem. SUMMARY OF THE INVENTION The present invention improves the reliability of the support force at the bottom of an excavation hole and has a high support force capable of transmitting the upper load safely and reliably to the ground without the above-mentioned problems. It is an object of the present invention to provide a method for rotating and burying existing piles. Means for Solving the Problems The present inventor paid attention to the use of the function of rotating and setting the spiral wing and the function of consolidating cement milk to develop the supporting force, and further studied the function of setting and rotating. Then, the present invention has been reached. That is, according to the present invention, excavation is performed to a predetermined depth by a pre-auger method, and then cement milk is injected into the vicinity of the tip to form a soil cement in the vicinity of the tip. A ready-made pile that is to be an upper pile is installed on the ready-made pile that is to be a lower pile having wings, and when performing a rotary burial of the ready-made pile, a rod is arranged in a hollow portion of the upper pile, and through the rod. A method of rotating and burying pre-made piles with less earth removal, wherein a rotating force is applied to the lower pile to bury the lower pile. [0007] Preferably, the pre-auger is excavated to a predetermined depth with a diameter equal to or less than the spiral blade diameter of the ready-made pile to reduce the amount of earth removal,
Next, after excavating near the tip, cement milk is injected into the enlarged drilling hole to make it into a soil cement state, and then a pre-made pile having a spiral wing near the tip of the pile is rotationally pressed into the drilling hole to form a spiral wing. This is a method of burying ready-made piles with little earth removal, which is buried in an enlarged excavation hole. The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an outline of this method. 1 shown in FIG.
Is a pile main body, and 3 is a spiral wing fixed to the pile main body. Reference numeral 2 denotes an excavation hole, and reference numeral 4 denotes a hardened soil cement near the tip of the pile. Reference numeral 5 shown in FIG. 2 is an enlarged excavation hole larger than the pre-auger diameter. [0009] Soil cement is filled in the vicinity of the tip of the pile, which hardens with the passage of time after construction to become a hardened soil cement 4, which is integrated with the pile to form a composite structure. The excavator used for construction of this structure has an auger bit at the lowermost part and a rigid rod without bending at the upper part. The rod is provided with a plurality of stirring rods for stirring the ground as necessary. The auger bit at the tip may have any shape as long as it has a cutting edge. In the case of enlarged excavation, the enlarged excavation blade may be a hydraulic type that mechanically opens and closes, or may be a system that opens and closes by resistance to surrounding soil by reverse rotation. However, it is necessary that the tip of the bit has a nozzle and has a structure capable of discharging drilling fluid and cement milk. Using such an excavator, the excavation hole 2 is provided to a predetermined depth by a normal pre-auger method. At this time, excavation may be performed while pouring a drilling fluid such as water or bentonite mud, or when the ground is soft, the drilling may be performed without using the drilling fluid or the like to reduce the amount of soil excavated. When a loose sand layer is sandwiched in the middle part of the stratum, it is advisable to inject a drilling liquid containing bentonite or the like only into the stratum to prevent collapse of the sand layer due to excavation. When the enlarged drilling hole shown in FIG. 2 is provided in the vicinity of the tip, the enlarged drilling blade is expanded to perform the enlarged drilling, and cement milk is injected through a nozzle or the like at the bit tip to make the inside of the enlarged drilling hole a soil cement. . After pulling out the drilling rig, the lower pile 7 having the spiral wing 3 near the tip of the pile in the drilling hole is lowered by rotation, and the spiral wing 3 of the lower pile 7 is made of soil cement near the tip. It is fixed in the excavation hole 5. At this time, the rod 8 inserted into the hollow portion of the ready-made pile that becomes the upper pile 1 is detachably connected to a part of the lower pile having the spiral wing 3 and the rotational force of the rod is given only to the lower pile to rotate the lower pile. Lower by sinking. As shown in FIG. 7, if the rotatable joint 9 is provided at the joint between the lower pile and the upper pile, only the lower pile can be rotated. In order to connect the rod inserted in the hollow part of the upper pile to the lower pile, the end of the rod is generally a hexagonal coupler type joint, so fix the end plate with a hexagonal hollow part on the lower pile head If the hexagonal coupler of the rod is inserted into this hollow portion, the connection and removal can be easily performed. The larger the diameter of the excavation hole is, the larger the effect of loosening the ground is. Therefore, it is preferable that the pile is easily settled. However, a large excavation hole requires a large construction machine, and the amount of excavated soil is increased. A smaller diameter is desirable.
From the setting speed of the pile, it is preferable that the excavation hole is smaller than the outer diameter of the spiral blade because the propulsive force when rotating and setting the pile is larger. Therefore, the excavation hole may be quite small because the pile is easy to settle when the ground is soft.However, when the ground is hard, the rotational torque required for rotary subsidence increases, and the pile may be cut by the rotational force in the concrete pile. is there. Therefore, it is necessary to provide a large excavation hole to loosen the ground. In this case, it is sufficient that the borehole is larger than the pile diameter, but it is sufficient if the borehole diameter is smaller than the maximum. The length of the enlarged excavation hole may be selected according to the type of the ground and the required supporting force. About three times the diameter of the helical wing is sufficient, but five times or more is sufficient. The diameter of the enlarged excavation hole may be larger than the diameter of the spiral blade, but may be slightly smaller than the blade diameter when the ground is hard. If the drilling rig has sufficient capacity to enable large-scale excavation, it is desirable to make the diameter larger than the spiral blade diameter. In order to sufficiently transmit the load from the spiral blade to the enlarged bulb, it is sufficient that the enlarged excavation diameter is about 1.2 times the diameter of the spiral blade. The pile to be used can be any pile such as a steel pipe pile, a ready-made concrete pile, a steel pipe concrete pile, and an H-shaped steel pile. In the case of ready-made concrete, it is necessary to take measures to attach the spiral wing to the outer peripheral surface of the pile. A plurality of short steel pipes may be installed in the formwork in advance during the production of the concrete pile, and the helical wing may be fixed to the steel pipe portion by welding after the concrete is hardened. The spiral wing attached to the tip of the pile only needs to make one full turn of the spiral. At least one spiral wing is sufficient, but installing multiple spiral wings is more advantageous in terms of pile support capacity and rotational sinking capacity. When a plurality of spiral blades are installed, they are installed at substantially equal intervals, and the interval depends on the pile diameter, but it is effective to install them at intervals of about 2 to 10 times the diameter of the pile body. The diameter of the spiral wing is preferably about 1.5 to 3 times the diameter of the pile body. If it is less than 1.5 times, the effect of dispersing the load is small, and if it is more than 3 times, the sharing force of the blades becomes large, the thickness of the blades becomes thick, and the resistance at the time of rotation subsidence increases, making subsidence difficult. At least one spiral wing may be mounted near the tip of the pile, but it is more effective to mount a plurality of spiral wings near the tip of the pile as shown in FIG. In the case of one spiral wing, as shown in FIG. 6, it is more effective to dispose the spiral wing so that it is fixed above the soil cement hardened body in terms of the vertical support force of the pile and the rotational sinking ability. According to the present invention, it is possible to reduce the amount of sediment discharged during excavation since rotation and subsidence are possible. Also,
After the pile is buried, a high bearing capacity can be obtained, and if the spiral wing is enlarged, the soil cement and the pile can be integrated, so that the load transmission of the pile becomes good. In addition, the risk of torsion breakage of the pile used can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view showing an example of the present invention. FIG. 2 is a schematic explanatory view showing an example of the present invention in which a tip portion is enlarged and excavated. FIG. 3 is a schematic explanatory view showing an example of a conventional construction method in which a tip portion is enlarged and excavated. FIG. 4 is a schematic explanatory view showing an example of a conventional construction method using an ST pile with an enlarged tip. FIG. 5 is a schematic explanatory view showing an example of a conventional construction method using a knotted pile at the tip of the pile. FIG. 6 is an explanatory view showing another embodiment of the present invention. FIG. 7 is an explanatory view in the case where a joint between an upper pile and a lower pile is a rotatable joint. [Description of Signs] 1 Upper pile 2 Drilling hole 3 Spiral wing 4 Soil cement hardened body 5 Lower drilling hole 6 Upper non-forming layer 7 Lower pile 8 Rod inserted in hollow part 9 Rotatable joint

Claims (1)

[Claim 1] Excavation to a predetermined depth by the pre-auger method, and then cement milk is injected into the vicinity of the tip to make the vicinity of the tip into a soil cement state. A pre-made pile that is to be an upper pile is installed on the pre-made pile that is to be a lower pile having a spiral wing, and a rod is disposed in a hollow portion of the upper pile when rotating and burying the pre-made pile. A method of rotating and burying a ready-made pile with a small amount of earth removal, wherein a rotational force is applied to the lower pile via the lower pile.