JP2007169988A - Bearing pile press-in method and load testing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for pressing a pile into depth where sufficient bearing power can be obtained without rotating the pile even when sufficient press-in load cannot be applied to the pile like the case of driving the pile under an existing structure, and easily and accurately carrying out a load test after driving. <P>SOLUTION: An object bearing pile 4A is pressed downward by the resultant force of vertical load from a structural member 1 and the reaction in a pull-up direction of adjacent bearing piles 4B, 4C, and pressed into the ground again until the object bearing pile obtains sufficient bearing power. The object bearing pile is sequentially changed and pressed in until all the bearing piles obtain sufficient bearing power. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for press-fitting a support pile of a structure such as a building so as to obtain a sufficient support force, and a load for confirming that the press-fitted support pile has a sufficient support force. The present invention relates to a test method, and particularly to a press-fitting method and a loading test method suitable for placing a support pile below an existing structure.

  The support pile must be able to support the load of the structure sufficiently and be placed so that the support force does not decrease even if the ground changes due to various causes such as earthquakes and groundwater level fluctuations.

  There are various methods for placing support piles, but there is a method of applying pressure to the upper end of the pile by applying pressure from above using the weight of the existing structure, generally called the underpeening method. ing.

  Specifically, a jack is attached between the upper end of the support pile to be press-fitted and the structure, the jack is extended to push the structure upward against its weight, and the reaction of this lifting force Press the pile into the ground.

  The above-described underpeening method uses the weight of the existing structure to load the pile, so it is basically impossible to obtain a supporting force greater than the load of the structure, and the pile is press-fitted by the underpeening method. In this case, the contact point between the jack attached to the pile to be press-fitted and the structure is the force point, the contact point between the upper end of the other pile and the structure is the fulcrum, and the contact point between the upper end of the other pile and the structure is the action point. A lever is formed, and the load of the structure located above the pile to be press-fitted is lifted without being sufficiently applied, and the total weight of the structure cannot be applied to the press-fitting of the target pile There is a problem.

  Moreover, since a sufficient load cannot be applied to the pile after placement, the load test of the pile after placement cannot be performed accurately.

  Therefore, instead of simply press-fitting the pile by the weight of the structure, a rotary press-fitting method that obtains sufficient support force by press-fitting while rotating the pile may be used together (for example, see Patent Document 1).

  That is, since a sufficient support force cannot be obtained by a simple underpeening method, it is a method of trying to reach a depth at which a sufficient support force can be obtained by press-fitting while rotating the pile.

  However, apart from press-fitting equipment such as jacks used in the underpeening method, the rotary press-fitting method requires equipment for rotating the pile, which increases the equipment cost and requires time and expense for equipment installation and setting. There is a problem of hanging.

  Also, to determine whether a support pile placed by the rotary press-fitting method has the required support force, measure the torque to rotate the pile and determine the support force by the magnitude of the torque. However, the determination of the supporting force by the rotational torque measurement does not necessarily provide satisfactory accuracy, and there is a problem that a separate torque measuring device is required for the measurement.

Japanese Patent Laid-Open No. 8-100136 (pages 1 to 4, FIGS. 1 to 9)

  The present invention supports a case where a sufficient load for press-fitting cannot be applied to a support pile to be placed, such as when a support pile is placed below an existing structure. It is an object of the present invention to provide a method capable of press-fitting a pile to a depth at which a sufficient supporting force can be obtained without rotationally press-fitting and performing a loading test after placing easily and accurately.

  In order to solve the above-mentioned problem, the press-fitting method according to the present invention is such that after at least three or more support piles are individually temporarily press-fitted, a structural material is placed above the two support piles adjacent to the target support pile. By connecting the adjacent support pile and the structural material 1, and attaching a jack between the lower surface of the structural material and the upper end of the support pile to be placed, and extending the jack, Pressurizing the target support pile downward by the resultant force of the vertical load of the adjacent support pile and the reaction force in the pull-up direction of the adjacent support pile, and re-pressing into the ground until sufficient support force is obtained in the target support pile, The target support piles are sequentially changed so that all the support piles are press-fitted until a sufficient support force is obtained, and the structural material is used as the foundation of an existing structure.

  In the loading test method according to the present invention, the structural material is exposed above the two supporting piles adjacent to the target supporting pile, the adjacent supporting pile and the structural material 1 are connected, and the lower surface of the structural material By attaching a jack between the upper end of the support pile to be placed and extending this jack, the target is supported by the resultant force of the vertical load from the structural material and the reaction force in the pulling-up direction of the adjacent support pile. The pile is loaded with the required pressure downward, the amount of settlement of the target support pile in this loaded state is measured, and the strength of the support pile is measured from the amount of settlement. As the basis of.

According to the press-fitting method according to the present invention, in addition to the load of the structural material such as the foundation of the existing structure, the pile can be press-fitted using the pull-out stress of the adjacent pile that has been temporarily press-fitted in advance. Even if the rotary press-fit method is not adopted, it is possible to press-fit the pile with a sufficient load.
Therefore, a highly reliable support pile can be constructed with a minimum of equipment and man-hours.

  According to the loading test method according to the present invention, it is possible to perform a test by applying a sufficient load to the support pile after placement, and therefore it is possible to construct a highly reliable support pile, and the safety of the structure. You can get enough.

Hereinafter, the Example of the press-fit method which concerns on this invention is described in detail based on the specific example in the case of placing a support pile under the foundation of an existing structure.
First, among the planned placement positions 2 and 2 of the support pile in the foundation 1 of the structure, the work holes 3 are dug around at least three planned positions, and the three support piles 4 are formed by a normal underpeening method, 4 is placed (temporary press-fitting).

  Specifically, a hydraulic jack 6 is attached to the upper end of a short steel pipe pile 5, the rod upper end of the hydraulic jack is brought into contact with the lower surface of the foundation 1, the rod is extended, and the steel pipe pile is grounded by reaction due to the weight of the structure. Press-fit inside and connect the steel pipe piles 5 and 5 one after another by means such as welding the short pipe to the steel pipe pile using a short pipe 5a having an outer diameter fitted inside the steel pipe pile 5 as a connecting tool. Then, it is driven to a depth that allows press-fitting according to the weight of the structure.

  Next, as shown in FIG. 3, brackets 7 are attached to the upper ends of the target support piles 4A and the other support piles 4B and 4C adjacent to the support piles, and the brackets 7 in the adjacent support piles 4B and 4C are attached. , 7 and the base 1 are connected by a connecting tool 8 made of, for example, a bolt or a nut.

  The connection tool 8 may be connected so as to withstand the force in the pulling direction between the bracket 7 and the foundation 1. For example, as shown in FIG. 4, the holder part 9 fastened to the outer periphery of the support pile 4 at the lower part. It is also possible to suitably use a connector having a structure in which a latching portion 10 configured to embrace the footing portion 1a of the foundation 1 is provided on the upper portion and the holder portion and the latching portion are coupled by an arm 11.

  Then, a hydraulic jack 6 is attached between the bracket 7 of the central support pile 4A to be driven and the lower surface of the foundation 1, and the rod of the hydraulic jack is extended to drive the support pile 4A into the ground (this Press fit).

  In this way, the hydraulic jack 6 is pressed into the support pile 4A by using the reaction force in the pulling-up direction of the adjacent support piles 4B and 4C in addition to the load from the structure, and thus the support pile 4A can be pressed deeper. it can.

  At this time, depending on the configuration of the stratum, the friction force between the outer periphery of the support pile 4A and the surrounding earth and sand (natural ground) may be large and the press-fitting resistance of the support pile may be large. A protrusion is attached to the outer periphery at an appropriate position around 4A, for example, the outer periphery near the tip of the support pile, and the ground on the outer periphery of the support pile is shaved by this protrusion to reduce the frictional force between the outer periphery of the support pile and the ground. (Friction cut) In this way, it is possible to press-fit the support pile 4A to a position where a deeper and greater support force can be obtained.

  Note that, for example, a means of winding a reinforcing bar around the support pile or fixing an iron plate to the outer periphery of the support pile by welding or the like can be used for the protrusion.

  After completing the press-fitting of the support pile 4A by the above-mentioned process, the support pile 4D next to the next support pile 4B or 4C (4C in FIG. 5) is temporarily press-fitted, and the support pile that has been press-fitted with this support pile 4D. Attach the connecting tool 8 between the upper end of 4A and the foundation 1, press-fit the support pile 4B or 4C (4C in FIG. 5), repeat the temporary press-fit and the main press-fit of adjacent support piles one after another, and Complete press-fitting to the pile.

  In order to determine whether or not sufficient support force has been obtained for the support pile that has been placed as described above, a loading test according to the present invention is performed according to the following procedure.

  As shown in FIG. 6, brackets 7 are attached to the upper ends of the support piles 4 </ b> A to be tested as well as the other support piles 4 </ b> B and 4 </ b> C adjacent to the support piles, as in the press-fitting of the support piles 4. The brackets 7 and 7 and the foundation 1 in the support piles 4B and 4C are connected to each other by a connector 8 made of, for example, a bolt or a nut.

  Next, a hydraulic jack 12 for testing is attached between the support pile 4A to be tested and the lower surface of the foundation 1. This hydraulic jack is provided with a pressure gauge and a galvanometer, and with a settlement amount measuring device 13 such as a dial gauge for accurately measuring the settlement amount of the support pile due to loading.

  In the state described above, the rod of the hydraulic jack 12 is extended to load the support pile 4A to reach the required load strength necessary for the test.

  At this time, in addition to the load applied from the structure to the support pile 4A, the stress in the pulling direction of the adjacent support piles 4B and 4C is added as a reaction force, so that sufficient load strength is obtained. And a reliable loading test can be performed.

  After completing the loading test described above and confirming that sufficient support force was obtained for all the support piles, the test equipment was removed and the upper ends of the support piles 4 and 4 and the lower surface of the foundation 1 were appropriately fixed. Then, the hole dug for work is backfilled and all the placing work and the loading test are completed.

The top view which shows the relationship between the foundation of a structure, and the placement position of a pile. The longitudinal section showing the process of temporary press-fitting in the press-fitting method of the present invention. The longitudinal cross-sectional view which shows the process of this press injection in the press injection method of this invention. The longitudinal cross-sectional view which shows the other example of a connection tool. The longitudinal cross-sectional view which shows the process after this press injection in the press injection method of this invention. The longitudinal cross-sectional view which shows an example of the implementation state of the loading test method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foundation of structure 2 Planned placement position of support pile 3 Work hole 4, 4A, 4B, 4C, 4D Support pile 5 Steel pipe pile 6 Hydraulic jack 7 Bracket 8 Connector 9 Holder part 10 Latch part 11 Arm 12 Hydraulic jack 13 Settlement measuring instrument

Claims (4)

  After at least three support piles are temporarily press-fitted separately, the structural material is placed above the two support piles adjacent to the target support pile, and the adjacent support pile and the structural material 1 are connected. By attaching a jack between the lower surface of the structural material and the upper end of the support target pile, and extending the jack, the vertical load from the structural material and the reaction force in the pull-up direction of the adjacent support pile The target support pile is pressed downward by the resultant force and re-injected into the ground until a sufficient support force is obtained for the target support pile. A method for press-fitting a support pile that is press-fitted until the is obtained.   The method for press-fitting a support pile according to claim 1, wherein the structural material is a foundation of an existing structure.   The structural material is exposed above the two supporting piles adjacent to the target supporting pile, the adjacent supporting pile and the structural material 1 are connected, and the lower surface of this structural material and the upper end of the placing target supporting pile By attaching a jack between the two and extending the jack, the target support pile is moved downward by the resultant force of the vertical load from the structural material and the reaction force in the pulling-up direction of the adjacent support pile. A loading test method for a supporting pile, in which the amount of settlement of the target supporting pile in this loaded state is measured and the yield strength of the supporting pile is measured from the amount of settlement.   The loading test method for a support pile according to claim 4, wherein the structural material is a foundation of an existing structure.

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