JP5766974B2 - Investigation method of cast-in-place pile driving ground and ground surveying machine attachment - Google Patents

Description

  The present invention relates to a survey method and a ground survey machine attachment for a cast-in-place pile placement ground, and more specifically, a cast-in-place pile placement ground capable of reducing work man-hours and accurately grasping the supporting force of the ground. It relates to survey methods and ground survey machine attachments.

  When placing cast-in-place piles, in order to understand the bearing capacity of the ground, surveys are usually made on the ground to be cast. Conventionally, as shown in FIG. 4, first, this ground survey is conducted by boring at a position PB in the vicinity of positions P1, P2, P3, P4, P5, and P6 where cast-in-place piles are placed. Know the geology in advance. Next, the ground was excavated at positions P1, P2, P3, P4, P5, and P6 where the cast-in-place piles were actually placed, and the geology of the excavated ground was visually compared with the boring sample. This method has a problem that it lacks accuracy because it cannot quantitatively grasp the bearing capacity of the ground on which the cast-in-place pile is placed.

  An automatic ram sounding surveying machine is known as a surveying machine that surveys the ground relatively easily (see, for example, Patent Document 1). The automatic ram sounding investigation machine is an investigation machine in which a rod having a tip cone is hit with a hammer to penetrate into the ground. The hammer is automatically dropped from the position of 50 cm to the rod, and the number of hits required for the tip cone to penetrate 20 cm into the ground is recorded, and the supporting force of the ground is grasped based on the recorded number of hits. be able to. That is, if this surveying machine is used, it becomes possible to quickly and quantitatively grasp the supporting force of the ground.

  However, when investigating the placement ground of cast-in-place piles, there is a problem in using it as it is, unlike when investigating the ground by installing an investigation machine on the normal ground. That is, since the target ground is the ground at the bottom of the excavation hole, it is necessary to lower the survey machine and install it at the bottom of the excavation hole. Therefore, the deeper the drilling hole, the longer it takes to lower and install the survey machine, and the longer it takes to lift the survey machine after the survey, the more work man-hours are required. was there.

  In addition, if there is groundwater inside the excavation hole, the survey machine cannot be lowered directly to the bottom of the hole, and the survey machine needs to be waterproof. However, it is difficult to make the survey machine waterproof.

  Therefore, if the survey machine is installed at a position above the excavation hole, it can be installed quickly, so that the working time can be shortened. However, in this case, the rod is exposed from the ground to the bottom of the excavation hole (not buried in the ground), so the hammer was hit by the hammer as the depth of the excavation hole increased. In such a case, there is a high risk of large rod runout or buckling of the rod. When a large rod runout occurs or the rod buckles, accurate data cannot be obtained, and there is a problem that it is impossible to accurately grasp the supporting force of the ground.

JP 2003-213661 A

  An object of the present invention is to provide a method for investigating a cast-in-place pile placing ground and a ground surveying machine attachment that can reduce work man-hours and can accurately grasp the supporting force of the ground.

In order to achieve the above object, a method for investigating a cast-in-place pile placing ground according to the present invention includes a cast-in-place pile driving method using an automatic ram sounding survey machine including a rod having a tip cone and a hammer for striking the rod. A method for investigating the ground, in which a ground rod is excavated using a casing rod at a position where a cast-in-place pile is to be cast to form a borehole, and from the ground to the bottom of the borehole where the casing rod is installed holds the upper and lower ends of the protective tube that extends in a predetermined position, the rod was inserted, and the upper end of the rod in the state of protruding from the upper end surface of the protective tube in the protective tube, the the survey apparatus installed at a position above the borehole to complete the setting, then the tip with the upper end of the rod and struck by said hammer, to protrude downward from the protective tube Which comprises carrying out a survey of the soil by the over down the survey device to penetrate the ground of the bottom of the hole.

The ground survey machine attachment of the cast-in-place pile placing ground of the present invention is a ground survey of cast-in-place pile placing ground attached to an automatic ram sounding survey machine equipped with a rod having a tip cone and a hammer that strikes the rod. A protection tube that extends under the surveying machine installed on the excavation hole in which a casing rod having an excavation hole is installed, and is inserted into the rod, and the protection pipe attached to, have a holding member extending to the outer peripheral side from the protective tube, with said protective tube is extended to the bottom hole of the borehole, the upper end of the rod from the upper end surface of the protective tube In a projecting state, the outer peripheral portion of the holding member is opposed to the inner wall surface of the casing rod, so that the protective tube is positioned at a predetermined position in the left-right direction in the excavation hole. The structure is set so as to hold, and the top end of the rod protruding from the upper end surface of the protective tube is struck by the hammer, and the tip cone protruding downward from the protective tube is inserted into the ground at the bottom of the hole characterized in that the.

  According to the method for investigating cast-in-place piles according to the present invention, an automatic ram sounding investigation machine is installed above the excavation hole, so that the number of work steps required for installation and withdrawal of the investigation machine is reduced, and the work speed is increased. Can be achieved.

  In addition, the upper end and the lower end of the protective pipe extending from the ground to the bottom of the excavation hole in which the casing rod is provided are held at predetermined positions, and the rod is inserted into the protective pipe. The survey machine is installed above the excavation hole and the setting is completed. As a result, even when the excavation hole is deep, the lateral deflection when the rod is hit by the hammer is restricted by the protective tube, so that the deflection is suppressed and large rod deflection occurs or the rod buckles. Problems are avoided and it is advantageous to accurately grasp the support force of the ground.

  Here, for example, by attaching a holding member extending from the protective tube to the outer peripheral side to the protective tube, and by making the outer peripheral portion of the holding member face the inner wall surface of the casing rod, the protective tube is placed in the excavation hole. Set to hold at a predetermined position in the left-right direction. Since the protective tube can be held more stably by this holding member, it becomes more and more advantageous to prevent the struck and buckling of the hit rod.

  The holding member has at least three legs extending radially outward from the protective tube as a center, and the ends of the legs are opposed to the inner wall surface of the casing rod as the outer periphery of the holding member. You can also.

  In addition, when the depth of the excavation hole is 5 m or more, the left and right runout when the rod is hit by a hammer is likely to increase, so it is more effective to apply the present invention.

  According to the ground surveying machine attachment of the cast-in-place pile driving ground of the present invention, a protective tube that extends below the automatic ram sounding surveying machine and in which the rod of this surveying machine is inserted, and is attached to this protective tube. In addition, since the holding member that extends from the protective tube to the outer peripheral side is provided, the automatic ram sounding survey machine can be installed at a position above the excavation hole, and the number of work steps required for the installation can be reduced. In addition, even when the drilling hole is deep, the lateral deflection when the rod is hit by a hammer is restricted by the protective tube, so the deflection is suppressed and large rod deflection occurs or the rod buckles. Is avoided, and it is advantageous for accurately grasping the supporting force of the ground.

  Here, for example, the holding member is configured to have at least three legs extending radially outward from the protective tube.

  Moreover, it can also be set as the specification comprised so that the length of the said leg part may expand-contract. According to this specification, even with one type of holding member, it is possible to stably hold the protective tube corresponding to the excavation holes having various inner diameters.

  The holding member can be moved in the longitudinal direction of the tube relative to the protective tube, and can be configured to be configured to be fixed to the protective tube at a predetermined position. According to this specification, since the holding member can be fixed at a desired position in the longitudinal direction of the protective tube, the holding member can be arranged at an appropriate position according to the situation at the site.

It is explanatory drawing which illustrates the whole geological survey machine equipped with the attachment of this invention. It is AA sectional drawing of FIG. It is explanatory drawing which shows the modification of an attachment. It is a top view which illustrates the position which borings and the position which casts a cast-in-place pile.

  Hereinafter, the survey method and the ground survey machine attachment of the cast-in-place pile placing ground of this invention are demonstrated based on embodiment.

  As illustrated in FIG. 1, when placing a cast-in-place pile, the ground is excavated using the casing rod 11 at a position where the cast-in-place pile is placed. The formed excavation hole H is in a state in which the casing rod 11 is installed. In the present invention, the ground at the bottom of the excavation hole H is the object of investigation.

  As illustrated in FIGS. 1 and 2, a ground surveying machine attachment 5 (hereinafter referred to as “attachment 5”) of a cast-in-place pile placing ground according to the present invention is a known automatic ram sounding surveying machine 1 (hereinafter referred to as “surveying machine 1”). ). The investigation machine 1 includes a rod 3 having a tip cone 3a, a hammer 2 that strikes the rod 3, and an arithmetic unit 4. The mass of the hammer 2 is 63.5 kg. The outer diameter of the rod 3 is 32 mm, and the outer diameter of the tip cone 3a is 45 mm. The investigation machine 1 is installed on a stage plate 12 spanning the upper end opening of the casing rod 11 and supported by a support 1a.

  The attachment 5 is provided at a lower position of the investigation machine 1 and includes a protective tube 6 that extends downward from the investigation device 1 and into which the rod 3 is inserted, and a holding member 7 that is attached to the protective tube 6. Yes. The protective tube 6 is a rigid tube, and for example, a metal tube such as a steel tube is used.

  The inner diameter of the protective tube 6 is a size that allows the rod 3 to move smoothly, and is, for example, about 36 mm to 60 mm. In addition to making the inner diameter of the protective tube 6 larger than the outer diameter of the tip cone 3a, it is possible to make it smaller than the outer diameter of the tip cone 3a. When the protective tube 6 having an inner diameter equal to or smaller than the outer diameter of the tip cone 3a is used, the protect tube 6 is extrapolated from the rear end side to the rod 3 to which the tip cone 3a is attached.

  The holding member 7 has a cylindrical fixing portion 8 fitted on the protective tube 6 and four legs 9 extending radially from the fixing portion 8 in the horizontal direction. The fixing portion 8 is fixed to the protective tube 6. Has been. The number of leg portions 9 may be 3, 5, or at least three. In this embodiment, each leg tip 9 a is formed in a circular arc shape that warps toward the protective tube 6. The holding member 7 is made of, for example, a metal such as steel or a hard resin. Note that the holding member 7 is not limited to the configuration having the cylindrical fixing portion 8 that is externally fitted to the protection tube 6, and may be configured to be interposed between the protection tubes 6 to be added.

  When the holding member 7 is attached to the protective tube 6, a shape that extends from the protective tube 6 to the outer peripheral side can be employed. For example, a disk-like body or something similar thereto can be employed as the holding member 7.

  The attachment 5 and the survey machine 1 are set according to the following procedure.

  First, the protective tube 6 is inserted into the excavation hole H in which the casing rod 11 is provided from the ground and extended to the bottom of the hole. If the length of one protective tube 6 is insufficient, a plurality of protective tubes 6 are added. The lower end portion of the protective tube 6 is embedded in the ground at the bottom of the hole, and the upper end portion is fixed to the stage plate 12 so that the upper and lower end portions are held at predetermined positions. The main body of the investigation machine 1 is installed on the stage plate 12 located above the excavation hole H, and the setting is completed by inserting the rod 3 into the protective tube 6 arranged at the lower position of the investigation machine 1.

  Next, the upper end of the rod 3 is automatically and continuously hit by the hammer 2 to carry out the ground investigation normally performed by the investigation machine 1. That is, the hammer 2 is automatically and continuously dropped from the position of the height 50 cm with respect to the upper end of the rod 3 (24 times / min) to strike the rod 3. The number of hits Nd required for the tip cone 3a to penetrate 20 cm into the ground is recorded by the arithmetic unit 4.

Specifically, the corrected number of hits Nd is calculated and recorded by the following equation (1).
Nd = Ndm-Nmantle = Nd-0.00041 Mv (1)
Nd: Corrected number of hits Ndm: Measured number of hits Nmantle: Number of hits corresponding to peripheral friction Mv: Rotational torque (N · cm)

  Torque measurement for correcting the circumferential friction is as follows. When the Ndm value exceeds five times, the rod 3 is rotated twice with a torque wrench for every 20 cm of penetration of the tip cone 3a, and the maximum torque (Mv) at that time is measured. When the Ndm value is 5 times or less, the rod 3 is only rotated twice when the rod 3 is connected every 1 m, and the maximum torque (Mv) is not measured (Mv = 0).

  This Nd value is assumed to be approximately equal to the N value (value indicating the ground bearing capacity) by the standard penetration test. Therefore, it is possible to quickly and quantitatively grasp the supporting force of the ground at the bottom of the hole (the ground where the cast-in-place pile is actually placed) based on the calculated hit count Nd.

  As described above, in the survey method of the present invention, the survey machine 1 is installed above the excavation hole H. Therefore, the survey machine 1 is lowered and installed on the bottom of the hole. The work to be withdrawn becomes unnecessary, and the work can be speeded up. Since the survey machine 1 is installed above the excavation hole H, even if groundwater exists in the excavation hole H, it is not necessary to make the survey machine 1 waterproof.

  In addition, since the upper end and the lower end of the protective tube 6 extending from the ground to the bottom of the excavation hole H are held at predetermined positions, the rod 3 inserted into the protective tube 6 is hit with the hammer 2. Even if the excavation hole H is deep, even if the rod 3 is swung to the left and right when hit, it is restricted by the protective tube 6. Therefore, problems such as large rod deflection or buckling of the rod 3 are avoided. If the runout is not restricted at all and a large rod runout or buckling occurs, the striking force by the hammer 2 will be dissipated, but in the present invention, such a problem can be prevented, so that the support force of the ground can be grasped accurately. Is advantageous.

  When the depth of the excavation hole H is 5 m or more, the left and right runout when the rod 3 is hit by the hammer 2 is likely to increase, and therefore it is more effective to apply the present invention.

  In this embodiment, the leg portion 9 of the holding member 7 attached to the protective tube 6 extends radially outward from the protective tube 6, and the leg portion tip 9 a is slightly spaced from the inner wall surface of the casing rod 11 ( 10 mm or less (for example, 5 mm to 10 mm) or in contact with each other. Thereby, the protective tube 6 is held in the excavation hole H at a predetermined position in the left-right direction. That is, the protective tube 6 is more stably held in the excavation hole H by the holding member 7. Therefore, even if the rod 3 is about to swing, the swinging of the struck rod 3 is reliably suppressed by the protective tube 6 held at a predetermined position by the holding member 7 (leg portion 9). And it becomes more and more advantageous to prevent buckling.

  When the disc-like body or the holding member 7 having a shape similar to this is used, the outer peripheral portion of the holding member 7 is opposed to the inner wall surface of the casing rod 11 with some clearance or in contact with it. The pipe 6 is held in a predetermined position in the left-right direction in the excavation hole H.

  If the upper and lower ends of the rod 6 can be held at predetermined positions in the left-right direction, the holding member 7 can be omitted. That is, the attachment 5 can also be configured with only the protective tube 6. If the holding member 7 can be omitted, it is more advantageous for speeding up the work.

  The number of the holding members 7 is appropriately determined according to the length of the protective tube 6 (depth of the excavation hole H). Alternatively, the holding member 7 can be configured to be movable in the longitudinal direction of the tube with respect to the protective tube 6 and fixed to the protective tube 6 at a predetermined position. According to this specification, since the holding member 7 can be fixed at a desired position in the longitudinal direction of the protective tube 6, the holding member 7 can be flexibly arranged at an appropriate position according to the situation at the site.

  For example, the cylindrical fixing portion 8 constituting the holding member 7 is sized so as to be slidably fitted to the protective tube 6, and the fixing portion 8 is fixed to the longitudinal direction of the protective tube 6 with a stopper such as a fixing bolt. It can be fixed at any position in the direction. In order to fix the holding member 7 at a desired position in the longitudinal direction of the protective tube 6, other structures can be adopted.

  The holding member 7 can be fixed to a predetermined position with respect to the protective tube 6 so that the holding member 7 and the protective tube 6 are integrated.

  Further, in this embodiment, since the leg tip 9a is arcuate, even if the leg tip 9a contacts the inner wall surface of the casing rod 11 when the protective tube 6 is inserted into or removed from the casing rod 11, smooth movement is ensured. The protective tube 6 can be inserted into and removed from.

  After the survey is completed, a reinforcing bar is built in the excavation hole H, and then concrete is driven. Next, the casing rod 11 is pulled out on the ground to complete the casting of the cast-in-place pile.

  As illustrated in FIG. 3, the leg portion 9 of the holding member 7 can be configured to extend and contract by providing an expansion / contraction mechanism 10 in the middle of the length direction. In FIG. 3, it is a telescopic leg portion 9 in which a thin leg portion 9B enters and exits from a thick leg portion 9A. Then, by tightening the fixing screw of the expansion / contraction mechanism 10 at a position where the small-diameter leg 9B is appropriately protruded from the large-diameter leg 9A, the small-diameter leg 9B is fixed and the length of the leg 9 is increased. Is set.

  The inner diameter of the excavation hole H varies depending on the site or the like, but the length of the leg portion 9 can be changed so as to correspond to the excavation hole H of various inner diameters even if there is only one type of holding member 7. It is a highly versatile specification. Therefore, the protection tube 6 can be stably held in the excavation hole H by the holding member 7 regardless of the inner diameter of the excavation hole H.

  Further, by adjusting the length of each leg 9, the tip cone 3 a can be penetrated into an appropriate position of the ground at the bottom of the excavation hole H. For example, the tip cone 3a can penetrate into the ground not only at the hole bottom center position but also at a position eccentric from the center.

DESCRIPTION OF SYMBOLS 1 Automatic ram sanding investigation machine 1a Support 2 Hammer 3 Rod 3a Tip cone 4 Arithmetic unit 5 Attachment 6 Protective tube 7 Holding member 8 Fixing part 9, 9A, 9B Leg part 9a Leg part tip 10 Expansion / contraction mechanism 11 Casing rod 12 Stage plate H Drilling hole

Claims (8)

A method for investigating cast-in-place pile placement ground using an automatic ram sounding survey machine equipped with a rod having a tip cone and a hammer for striking the rod. And excavating the ground to form an excavation hole, and holding the upper end and lower end of the protective tube extending from the ground to the bottom of the excavation hole in which the casing rod is provided, and the protection the rod is inserted into the tube, the upper end of the rod in the state of protruding from the upper end surface of the protective tube, to complete the setting of the survey equipment installed at the upper position of the borehole, then this the upper end of the rod and struck by said hammer, actual investigation of soil by the research unit for penetrating the tip cone which projects downward from the protective tube in the ground of the bottom of the hole Cast-in-place Kuida 設地 panel of survey methods which is characterized in that.   A holding member that extends from the protective tube to the outer peripheral side is attached to the protective tube, and the outer peripheral portion of the holding member is opposed to the inner wall surface of the casing rod, so that the protective tube is placed at a predetermined position in the left-right direction in the excavation hole The method for investigating cast-in-place pile placement ground according to claim 1, wherein the cast-in-place pile setting ground is set so as to be held.   The holding member has at least three legs extending radially outward from the protective tube as a center, and the ends of the legs are opposed to the inner wall surface of the casing rod as the outer periphery of the holding member. Method for investigating cast-in-place pile placement ground according to Item 2.   The depth of said excavation hole is 5 m or more, The investigating method of the cast-in-place pile placing ground in any one of Claims 1-3. A ground surveying machine attachment for cast-in-place pile installation ground attached to an automatic ram sounding surveying machine equipped with a rod having a tip cone and a hammer for striking this rod, and a casing rod having an excavation hole is installed inside A protective tube that extends below the surveying machine installed above the excavated hole and into which the rod is inserted, and a holding member that is attached to the protective tube and extends outward from the protective tube. have a, together with the protection tube is extended to the bottom hole of the borehole, and the upper end surface of the protective tube in a state where the upper portion is protruded in the rod, the casing an outer peripheral portion of the holding member By facing the inner wall surface of the rod, the protective tube is set to be held at a predetermined position in the left-right direction in the excavation hole. The upper end of the rod out by striking by said hammer-place concrete Kuida設地Release, characterized in that said tip cone which projects downward from the protective tube has a configuration to penetrate the ground of the bottom of the hole Ground survey machine attachment.   The ground surveying machine attachment of a cast-in-place pile placing ground according to claim 5, wherein the holding member has at least three legs extending radially outward from the protective tube as a center.   The ground surveying machine attachment of a cast-in-place pile placing ground according to claim 6, wherein the length of the leg portion is configured to expand and contract.   The cast-in-place pile driving device according to any one of claims 5 to 7, wherein the holding member is movable with respect to the protective tube in a longitudinal direction of the tube and is fixed to the protective tube at a predetermined position. Ground investigation machine attachment.

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