JP6617022B2 - Support pile arrival confirmation method of support pile and support pile construction method - Google Patents

Description

  The present invention relates to a support layer arrival confirmation method for a support pile and a construction method for the support pile.

The support pile secures a supporting force at the tip end portion of the pile by allowing the tip end (lower end) of the pile to penetrate the support layer for a predetermined length, and supports an upper load such as an upper structure.
For the construction management of support piles, it is necessary to confirm pile length and support layer arrival, confirmation of pile construction accuracy (angle, position, etc.), quality confirmation of pile diameter, rebar, etc.

  The pile length of the support pile is set to a length that can reach the support layer. The support layer is estimated from a ground layer cross-sectional view created based on previously conducted ground surveys, existing ground data, or the like. The formation cross section is generally created on the basis of locally performed boring data.

  However, the strata are not necessarily straight, and may be accompanied by slopes and folds. For this reason, the actual position (depth) of the support layer may differ from the position of the support layer shown in the formation cross-sectional view due to the inclination or folding of the formation. If the depth of the support layer is different from the formation cross section, the tip of the pile will not reach the support layer even if the pile is constructed as designed.

  Therefore, the construction of the support pile is generally performed while confirming that the tip of the pile reaches the support layer by measuring changes in the torque and current of the excavator (see, for example, Patent Document 1). ).

JP 2011-047274 A

  If there is a boulder or a bedrock layer with a small layer thickness in the ground, the torque and current of the excavator will rise temporarily, and it may be mistaken for the tip of the pile to reach the support layer. . In addition, if a construction record entry error or loss occurs, the arrival of the pile tip at the support layer may not be confirmed.

  From such a viewpoint, an object of the present invention is to propose a support layer arrival confirmation method and a support pile construction method that enable the support pile to be constructed more reliably.

  The method for confirming the arrival of a support layer of a support pile according to the present invention for solving the above-mentioned problem is that an elastic wave is generated at an excitation point set in the support layer, and is formed at a position apart from the excitation point in a plane. Receiving the elastic wave by a receiver provided on the pile, and confirming whether the tip of the pile has reached the support layer by the arrival time or amplitude of the elastic wave received by the receiver. It is a feature.

  According to the support layer arrival confirmation method of the support pile, it is possible to confirm whether or not the support pile has reached the support layer by receiving the elastic wave propagated through the support layer. The elastic wave propagating through the support layer is transmitted faster than the elastic wave propagating through the soft layer, and the amplitude is not greatly reduced. By confirming the arrival time and amplitude of the elastic wave received by the receiver, it can be confirmed that the tip of the support pile has reached the support layer.

If the elastic wave is oscillated from the tip of another pile reaching the support layer, it is efficient because it is not necessary to construct a boring hole or the like for providing an oscillation point.
Moreover, if the said elastic wave is received by the receiver provided in the several pile, since the arrival to a support layer can be confirmed at once about several pile, it is efficient.

  Moreover, the construction method of the support pile according to the present invention includes a pile installation step of installing the pile on the ground, and an elastic wave is generated at an excitation point provided in the support layer, and a receiver provided in the pile. A measuring step for receiving the elastic wave, and a confirmation step for checking whether or not the tip of the pile has reached the support layer based on the arrival time or amplitude of the elastic wave received by the receiver. In the confirmation step, when it is confirmed that the tip of the pile has reached the support layer, the press-fitting or driving of the pile is finished, and it is confirmed that the tip of the pile has not reached the support layer. In some cases, the stake is further press-fitted or driven.

  According to the construction method of the support pile, since it is confirmed that the tip of the pile has reached the support layer by confirming the elastic wave propagated through the support layer, highly reliable construction is possible. .

  According to the support layer arrival confirmation method and the support pile construction method of the present invention, the support pile can be constructed more reliably.

It is a sectional view showing the foundation structure of the building concerning the embodiment of the present invention. It is a plane sectional view of the basic structure shown in FIG. (A) is explanatory drawing of propagation of an elastic wave, (b) is explanatory drawing of propagation of the elastic wave which concerns on another form. It is explanatory drawing of the support layer arrival confirmation method of a support pile. It is a graph which shows the relationship between the arrival speed of an elastic wave, and distance.

  In embodiment of this invention, as shown in FIG. 1, about the building B which has several support piles 1, 1, ..., when performing a pile foundation construction, confirming the arrival to the support layer G1 of the support pile 1 Will be described. In this embodiment, as shown in FIG. 2, when constructing a pile foundation in which five support piles 1, 1,... Arranged in parallel at a predetermined interval are arranged in five rows (25 in total). Will be described. In addition, the number, arrangement | positioning, etc. of the support pile 1 in a pile foundation are not limited. Here, the support layer 2 in this specification refers to a hard formation whose N value exceeds 50.

The construction method of the support pile of this embodiment is provided with the pile installation process, the measurement process, and the confirmation process.
A pile installation process is a process of installing the support pile 1 in the ground G1, G2. This embodiment demonstrates the case where the support pile 1 is constructed by a pre-boring method. The support pile 1 is formed by excavating the ground G1 and G2 with an auger to form an excavation hole having a predetermined depth, and then inserting the existing pile into the excavation hole, and a gap between the inner wall of the excavation hole and the outer surface of the existing pile. It is constructed by filling the material with filler. In addition, after inserting an existing pile into a drilling hole, it finally press-fits or drives in to the bottom part of a drilling hole. In this embodiment, a hollow ready-made pile is used as the ready-made pile.

  In addition, the construction method of the support pile 1 is not limited to the pre-boring method. For example, another embedded pile method such as a steel pipe soil cement method or a driven pile method such as a hydraulic hammer method is adopted. Also good.

As shown in FIG. 3, the measurement step is a step of generating an elastic wave at the excitation point 2 provided in the support layer G <b> 1 and receiving the elastic wave by the receiver 3 provided in the support pile 1. .
In this embodiment, as shown in FIG. 2, the vibrator 2 is installed at the lower end (bottom part) of the support pile 1 (hereinafter referred to as “vibration pile 11”) disposed at the center of the pile group. An elastic wave is generated in the support layer by the vibrator 2. Here, the structure of the vibrator 2 is not limited. For example, what generates a vibration by dropping a weight, or what generates a vibration using a blur at the time of rotation may be used.

  In addition, the vibration pile 11 (support pile 1 in which the vibrator 2 is installed) needs to have a tip reaching the support layer G1. Therefore, in this embodiment, the vibration pile 11 is the support pile 1 that is the closest to the position where the previous geological survey (boring) was performed and the position (depth) of the support layer G1 is known. And

  As shown in FIG. 3A, the receiver 3 is provided at the upper end of a support pile 1 (hereinafter referred to as “reception pile 12”) other than the vibration pile 11 provided with the vibrator 2. The receiver 3 receives the elastic wave generated in the vibration pile 11. In addition, reception of an elastic wave may be received for every receiving pile 12, and in the state which has installed the receiver 3 in the some support pile 1, multiple elastic waves transmitted by the vibrator 2 were received. You may receive at once by the receiving pile 12 of a book.

As shown in FIG. 3 (a), the elastic wave has a route a passing through the support layer G1 and the support pile 1 (reception pile 12), and a route b passing through the ground G1 and G2 obliquely from the vibrator 3. And it is estimated that it is propagated by the route c which passes the vibration pile 11 and the ground surface. Here, the ground other than the support layer (hereinafter referred to as “soft layer G2”) has a lower elastic wave velocity than the support layer G1, concrete (support pile 1), and the like. For example, the elastic wave of sandy soil having an N value of 2 can be estimated to be about 70 m / s, and the elastic wave of viscous soil having an N value of 5 can be estimated to be about 140 m / s. On the other hand, it can be estimated that the elastic wave of the support layer G1 is about 300 m / s and the elastic wave of concrete is 1000 m / s or more. Therefore, the elastic wave propagated by the route a passing through the support layer G1 is received earliest.
Therefore, in the measurement process, the elastic wave that reaches the earliest among the elastic wave data measured by the receiver 3 is stored.

  In addition, as shown in FIG.3 (b), when setting an exciting point (exciter 2) to the head of the support pile 1, an elastic wave is a receiving pile after passing the ground from the exciting pile 11. A route d passing through 12 and a route e passing through the ground surface are expected. At this time, when the pile length of the support pile 1 is long, the propagation speed of the route e passing through the ground surface may be faster than the propagation speed of the route d. Therefore, if both the vibrator 2 and the receiver 3 are set to the head of the support pile 1, it is difficult to distinguish the elastic wave that has propagated the route d from the elastic wave that has propagated the route e. Therefore, it is desirable to set the vibration point at the lower end of the support pile 1 (vibration pile 12).

The confirmation step is a step of confirming whether or not the tip of the support pile 1 (reception pile 12) has reached the support layer G1 based on the arrival time of the elastic wave received by the receiver 3.
As shown in FIG. 4, the support pile 1 that has not reached the support layer G1 reaches the support layer G1 when the elastic wave w passes through the soft layer G2 because the support layer G1 has an inclination or a curvature. The arrival time t of the elastic wave w is delayed as compared with the supporting pile 1 that is doing. Therefore, by confirming the arrival time t of the elastic wave w, it is possible to confirm whether or not the tip of the support pile 1 has reached the support layer G1.

  When the elastic wave velocity of the support layer G1 is grasped in advance based on the geological survey result or the like, the arrival time t of the elastic wave w and the horizontal distance L from the excitation point (excitation pile 11) to the receiver 3 It is confirmed whether the front-end | tip of the receiving pile 12 has reached | attained the support layer G1 by comparing the elastic wave velocity calculated by (1) with the elastic wave velocity of the support layer G1.

  When the elastic wave velocity of the support layer G1 is unknown, as shown in FIG. 5, the relationship between the arrival time t of the elastic wave and the horizontal distance L from the vibrator 2 to the receiver 3 is graphed (plot). By doing this, it is confirmed that the tip of each receiving pile 12 has reached the support layer G1.

  If the receiver 3 is provided in the receiving pile 12 that has reached the support layer G1, the relationship between the arrival time t of the elastic wave w and the horizontal distance L falls within a certain range. On the other hand, when the receiving pile 12 does not reach the support layer G2, the relationship between the arrival time t of the elastic wave w and the horizontal distance L is out of a certain range. Therefore, as a result of summarizing the measurement results of the plurality of support piles 1 in a graph, a pile whose relationship between the arrival time t of the elastic wave w and the horizontal distance L is out of a certain range has not reached the support layer G1. to decide.

In the graph, a value (arrival time t) obtained by subtracting the propagation time t ₁ of the support pile 1 from the measured value of the total arrival time t ₀ of the elastic wave w from the vibrator 2 to the receiver 3 is plotted. This is to prevent the arrival time t from being affected by the difference in pile length when the depths of the support layers G1 are not the same and the pile lengths of the support piles 1 are different. When the soil quality of the support layer G1 is uniform, the relationship between the propagation time (elastic wave arrival time t) of the support layer G1 and the distance L is a linear relationship, so it is easy to find an abnormal value.

In addition, since the formation which can become the support layer G1 may have a crack, the support layer G1 is not necessarily uniform. Therefore, it is necessary to determine whether or not the support pile 1 has reached the support layer G1 in consideration of non-uniformity.
The determination of the non-uniformity is made by comparing the arrival times t of the elastic waves measured by the plurality of receiving piles 12 at substantially the same distance. The limit value and the lower limit value are set from the data excluding the protruding abnormal values compared to the plurality of arrival times t, and the range between the upper limit value and the lower limit value is set as the normal range. On the other hand, a value outside the normal range is recognized as an abnormal value.

  In this embodiment, first, the arrival time t of the elastic wave w from the central support pile 1 (vibration pile 11) to the support pile 1 (the support piles 1, 1,. And a horizontal distance L, a graph is created. When the measurement results of the four support piles 1, 1,... Are plotted, the presence or absence of abnormal values is confirmed. Next, an upper limit value and a lower limit value are set by each plot, and a normal range is set by drawing a straight line from the origin (0, 0) to the upper limit value and the lower limit value. When an abnormal value is found, this value (abnormal value) is excluded.

  Thereafter, the measurement results of the other receiving piles 12 are plotted to confirm that they are within the normal range. When the tip of the support pile 1 does not reach the support layer G1 due to the inclination or bending of the support layer G1, since the arrival time t of the elastic wave is delayed, the plot is out of the normal range.

  In the confirmation step, the support pile 1 determined to have not reached the support layer G1 (the support pile 1 outside the normal range) further press-fits or drives in the support pile 1. On the other hand, the support pile 1 determined to have reached the support layer G1 is filled with a filler in the gap between the outer surface of the existing pile and the inner wall surface of the excavation hole, and the construction of the support pile 1 is completed.

In the confirmation process, whether or not the support pile 1 has reached the support layer G1 is confirmed by the magnitude of the amplitude of the elastic wave as necessary.
The S wave is attenuated by viscous soil containing a large amount of water content. Therefore, in the case where the soft layer G2 is a viscous soil or the support layer G1 is weathered and softened, if the amplitude of the elastic wave is reduced, the soft layer G2 is attenuated in the soft layer G2 (softened support layer). The elastic wave will not propagate. Therefore, the intervention of the soft layer G2 can be grasped by the magnitude of the amplitude of the elastic wave.

  According to this embodiment, it is possible to confirm in a short time whether or not the tip of the support pile 1 has reached the support layer G1 by receiving the elastic wave w propagated through the support layer G1. Therefore, the construction of the support pile 1 can be performed efficiently and reliably.

Even if the elastic wave velocity of the support layer G1 is unknown, the tip of the support pile 1 is supported by the support layer G1 depending on the relationship between the arrival time t of the elastic wave w created based on the measurement result and the horizontal distance L. It is possible to confirm whether or not
Further, by confirming the arrival of the support layer G1 for each support pile 1, it is possible to grasp the three-dimensional shape of the support layer G1 (the inclination of the formation, the progress of weathering, etc.).

The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.
In the above embodiment, whether or not the support pile 1 has reached the support layer G1 is confirmed based on the arrival time and the amplitude of the elastic wave, but depending on either the arrival time or the amplitude of the elastic wave. The arrival of the support pile 1 to the support layer G1 may be confirmed.

  Although the said embodiment demonstrated the case where the support layer arrival confirmation of a support pile was performed after constructing a some support pile, the timing which performs a support layer arrival confirmation is not limited to this. For example, it may be performed every time the support pile 1 is constructed. That is, after the arrival of one support pile 1 to the support layer is confirmed and the construction is completed, the construction of the next support pile 1 may be started.

In the said embodiment, although the support pile 1 arrange | positioned in the center among the several support piles 1 was used as the vibration pile 11, the vibrator 2 was provided in the lower end, but the installation location of the vibrator 2 is to this It is not limited. For example, you may provide in the boring hole formed in the ground.
Moreover, you may set an oscillation point (boring hole etc.) outside the area of a support pile construction location.

  Moreover, in a measurement process, you may measure the vibration (elastic wave) which arises at the time of pile stop management of the support pile 1 with the receiver provided in the other support pile 1 (reception pile 12). By carrying out like this, the effort and expense which are required for use of the vibrator 2 can be omitted.

  When confirming the arrival of the support layer of the cast-in-place pile, a hollow support pile 1 is formed by providing a steel pipe or the like in advance in the center of the vibration-generating pile 11, and the steel pipe is used to start the pile. The vibrator 2 may be provided at the lower end of the vibration pile 11.

  Moreover, in the all casing method, when the support layer arrival confirmation method of the support pile of the present invention is applied, the measurement process and the confirmation process may be performed in a state where the casing (steel pipe) is press-fitted into the ground.

1 Support pile (pile)
DESCRIPTION OF SYMBOLS 11 Excitation pile 12 Reception pile 2 Exciter 3 Receiver G1 Support layer G2 Soft layer

Claims (4)

Generate elastic waves at the excitation point set in the support layer,
The elastic wave is received by a receiver provided on a pile formed at a position away from the excitation point in plan view,
A support layer arrival confirmation method for a support pile, wherein it is confirmed whether or not the tip of the pile has reached the support layer based on the arrival time or amplitude of the elastic wave received by the receiver.   The support layer arrival confirmation method for a support pile according to claim 1, wherein the excitation point is provided at a tip of another pile different from the pile.   The support pile arrival confirmation method for a support pile according to claim 1 or 2, wherein the elastic wave is received by a receiver provided on a plurality of piles. Pile installation process to install piles on the ground,
A measurement step of generating an elastic wave at an excitation point provided in the support layer and receiving the elastic wave by a receiver provided in the pile,
A confirmation step of confirming whether or not the tip of the pile has reached the support layer by the arrival time or amplitude of the elastic wave received by the receiver, and a construction method of the support pile comprising:
In the confirmation step, when it is confirmed that the tip of the pile has reached the support layer, the press-fitting or driving of the pile is finished, and it is confirmed that the tip of the pile has not reached the support layer Is a method for constructing a support pile, wherein the pile is further press-fitted or driven.

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