JP2017115533A - Pile construction management method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile construction management method capable of saving time and efforts for re-implementation of pile erection construction caused due to an insufficient support strength, by extremely easily and surely determining, before pile erection, whether a pile distal end support strength of a pile hole is sufficient when erecting a cast-in-place pile or a precast pile within the pile hole that is opened on a ground.SOLUTION: After a pile hole H is opened on a ground G and before erecting a pile in the pile hole H, a penetration test machine 10 is inserted into the pile hole H and grounded. The penetration test machine comprises: a shaft-like knocking block 1 of which the distal end protrudes downwards; a drive hammer 2 which freely falls to strike the knocking block 1; and a suspension mechanism 3 which suspends the fallen drive hammer 2 and releases it down at a predetermined height. A support strength of a hole bottom Hb is determined from the number of times of striking required for the knocking block 1 to penetrate up to a predetermined depth from the hole bottom Hb. In the case where the support strength is equal to or more than a predetermined value, the pile is erected in the pile hole H.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pile construction management method in which a cast-in-place pile or a ready-made pile is built in a pile hole previously drilled in the ground, such as an earth drill method or a pre-boring method.

  Conventionally, the Kelly bar type earth drill method has been widely used for the construction of cast-in-place piles. In this construction method, for example, as shown in the order of steps in FIG. 5, (a) pile core alignment with the ground G, (b) excavation for a stunt pipe with the shaft excavation bucket B1, (c) press-fitting of the stunt pipe Ps, (d) Drilling with a small-diameter shaft excavation bucket B2 that is exchanged while injecting a stabilizing liquid Ls such as bentonite into the hole, (e) drilling to a hard support layer Gh below the ground G, (f) drilling depth with a measure M with a weight (G) Reinforcing rod Fc insertion, (h) Tremy tube Tp insertion, (i) Slime S discharge by introducing air A, (j) Raw concrete C placement, (k) Tremy tube Tp The cast-in-place pile PC is built in the procedure of (1) pulling out the stunt pipe Ps. In the figure, Gs indicates a soft layer made of soil or sand on the upper side of the ground G. In addition, as a bottom-pile construction, the cast-in-place pile PC may be built after expanding the bottom part of the pile hole H with a bottom-up bucket.

  On the other hand, in the pre-boring method, the ground is excavated using a screw rod or excavation bit attached to an earth auger, and after the rooting solution such as soil cement and pile fixing solution is injected into the formed pile hole, Prefabricated piles such as RC piles and steel pipe piles are laid down.

  Therefore, in these earth drilling methods and pre-boring methods, it is generally possible to determine whether the support strength of the pile after completion of construction is sufficient by a loading test, but if this proves that the support strength is insufficient Since much labor, time and cost will be spent on the re-execution of the pile construction, it is ideal if it can be determined before pile installation whether the support force at the tip of the pile is sufficient for the excavated pile hole. Conventionally, from this point of view, there has been a method of capturing changes in excavation load from the current value of the rotation drive motor of the excavation member and confirming that the pile hole has reached a hard support layer deep in the ground due to this increase in excavation load. It has been proposed (Patent Documents 1 to 3).

  However, in the method of detecting the change in the excavation load from the current value of the rotation drive motor, the frictional resistance between the excavation member and the hole wall increases as the digging hole becomes deeper, so that the excavation can be performed even if it does not reach the support layer. Excessive increase in load, slippage at the excavation site, conversely, even if the support layer is reached, the excavation load decreases, and the excavation load varies greatly depending on the skill of the operator's excavation work. Therefore, it is poor in reliability as an index for confirming the arrival at the support layer. Therefore, in general, based on the data of the geological sample obtained exclusively by the test boring at the planned construction site, it is usually considered that the material reached the support layer by drilling to a predetermined depth. The underground depth of the entire construction site is not always uniform with a uniform stratigraphy. Depending on the geological history, the depth of the support layer may vary locally, or the difference in hardness of the support layer itself may be large. In many cases, it cannot be said that the bottom of each pile hole actually has a sufficient supporting force at the tip of the pile.

JP-A-5-280031 JP 2000-245058 A JP 2003-74045 A

  In view of the above-mentioned circumstances, the present invention provides a method for constructing a cast-in-place pile or a ready-made pile in a pile hole previously drilled in the ground, such as an earth drill method or a pre-boring method. Providing a pile construction management method that makes it possible to determine whether or not the bearing capacity is sufficient before and after laying a pile in a very simple and reliable manner, thereby eliminating the need for re-working pile laying construction due to insufficient support strength. It is aimed.

  If the means for achieving the above-mentioned object is shown with reference numerals in the drawings, the pile construction management method according to the invention of claim 1 is that after the pile hole H is drilled in the ground G, Before building the pile (the cast-in-place pile P1, the ready-made pile P2), the shaft-shaped knocking block 1 whose tip protrudes downward, the drive hammer 2 that strikes the knocking block 1 by free fall, and the drive after the fall A penetration tester 10 having a lifting mechanism 3 that lifts the hammer 2 and releases it at a predetermined height is inserted into the pile hole H and settled, and the knocking block 1 is required to penetrate from the hole bottom Hb to a predetermined depth. The support strength of the hole bottom Hb is determined from the number of hits, and when the support strength is equal to or higher than a predetermined value, the pile (the cast-in-place pile P1, the ready-made pile P2) is built in the pile hole H.

  The invention according to claim 2 is the pile construction management method according to claim 1, wherein the penetration test machine 10 is inserted into the pile hole H when the pile hole H is liquid (stable liquid Ls, root-solidifying liquid Lh, hole It is assumed that the operation is performed in a state filled with the peripheral fixing liquid Lf).

  According to a third aspect of the present invention, in the pile construction management method according to the second aspect, in the penetration testing machine 10, the upper and lower end portions (the peripheral surface portions 41a and 42a of the end members 41 and 42) of the main body casing 4 are both tapered. It is supposed to be.

  According to a fourth aspect of the present invention, in the pile construction management method according to any one of the first to third aspects, the penetration testing machine 10 has a cylindrical shape in which the lifting mechanism 3 and the drive hammer 2 are built in the cylindrical main body casing 4. The hammer casing 5 is held up and down freely, the upper end portion (disk portion 12) of the knocking block 1 is fixed to the lower end of the hammer casing 5, and the lower side (penetrating shaft 11) of the knocking block 1 is the main body. The lower end side of the casing 4 is penetrated to protrude downward and the plurality of grounding legs 6 are provided around the lower end portion of the main casing 4.

  According to a fifth aspect of the present invention, in the pile construction management method according to any one of the first to fourth aspects, the penetration testing machine 10 includes a sensor 7 that detects the drive hammer 2 at an upper limit position and a lower limit position.

  According to a sixth aspect of the present invention, in the pile construction management method according to any of the first to fifth aspects, the penetration testing machine 10 includes an encoder 8 for measuring the amount of settlement of the hammer casing 1.

  Next, effects of the present invention will be described with reference numerals in the drawings. First, according to the invention of claim 1, before the pile (cast-in-place pile P1, ready-made pile P2) is built in the pile hole H drilled in the ground G, the penetration testing machine 10 is inserted into the pile hole H. From the number of hits of the drive hammer 2 required for the knocking block 1 to penetrate from the hole bottom Hb to a predetermined depth, the support strength of the hole bottom Hb is measured (N value) in an extremely simple and reliable manner. Since it can be measured, it can be determined that it can be built when the support strength is equal to or higher than a predetermined value, and a pile can be built in the pile hole H to complete pile construction efficiently. On the other hand, if the support strength is less than the predetermined value, it will be impossible to embed it. Therefore, excavate deeper, or backfill the pile hole H and newly drill at a different position. This determination may be made. Therefore, it is possible to avoid a situation in which a great amount of labor, time and cost are spent to redo the pile erection work, as in the case where a lack of support strength is found in a loading test after completion of the pile work in the past. In addition, since a standard penetration testing device that has been widely used for determining the N value of the ground can be used as the penetration testing machine 10, no special new equipment is required to implement this pile construction management method. There are advantages that the construction cost can be reduced and the international standard N value can be managed, so that a reliable evaluation of the measured value can be obtained.

  According to the invention of claim 2, since the penetration tester 10 can be manufactured at a low cost with a simple structure, the penetration tester 10 in the pile hole H is provided with the plurality of grounding legs 6 around the lower end of the main casing 4. Since the bottoming posture 10 is stable in the vertical state and the striking force of the drive hammer 2 is constant, the support strength can be determined more accurately.

  According to invention of Claim 3, insertion of the penetration testing machine 10 to the pile hole H was filled with the liquid substance (stable liquid Ls, root-solidifying liquid Lh, hole circumference fixing liquid Lf). Since it carries out in a state, collapse of the hole wall by the entrance / exit of the penetration testing machine 10 can be suppressed.

  According to the invention of claim 4, since the upper and lower ends 4a and 4b of the main casing 4 of the penetration tester 10 are both tapered, the inside of the pile hole H is a liquid material (stabilizing liquid Ls, rooting liquid Lh). In this state, the disturbance of the liquid material when the penetration tester 10 is made to enter and exit is reduced, and the collapse of the hole wall can be prevented more reliably.

  According to the invention of claim 5, since the penetration tester 10 incorporates the sensor 7 that detects the upper limit position and the lower limit position of the drive hammer 2, the number of hits by the drive hammer 2 can be assured by the output signal from the sensor 7. Can be caught.

  According to the invention of claim 6, since the penetration testing machine 10 incorporates the encoder 8 that measures the amount of settlement of the hammer casing 1, the amount of penetration into the hole bottom Hb due to the knocking block 1 can be accurately captured. .

It is a vertical side view which shows the measurement condition of the support strength of the hole bottom in the pile construction management method of 1st Embodiment which concerns on this invention. The penetration testing machine used for the measurement of the support strength is shown, (a) is the state before the drive hammer is activated, (b) is the state where the drive hammer is lifted, (c) is the state where the drive hammer is freely dropped, It is a vertical side view shown, respectively. It is sectional drawing of the XX line of Fig.2 (a). The operation of the lifting mechanism in the penetration testing machine is shown, (a) is a side view when the drive hammer is lifted, and (b) is a side view when the drive hammer is released. It is a schematic longitudinal cross-sectional view which shows a Kelly bar type earth drill construction method in order of the process of (a)-(l). It is a schematic longitudinal cross-sectional view which shows the pile construction management method of 2nd Embodiment which concerns on this invention in order of the process of (a)-(i). It is a vertical side view which shows the measurement condition of the support strength of the hole bottom in the pile construction management method of 3rd Embodiment which concerns on this invention.

  Below, the embodiment of the pile construction management method concerning the present invention is described concretely with reference to drawings. In the first embodiment, the pile construction management method of the present invention is applied to the construction of cast-in-place piles by the kelly bar type earth drill method, and in the second and third embodiments, the construction of ready-made piles by the pre-boring method.

  In the pile construction management method of the first embodiment, in the kelly bar type earth drill method shown in FIG. 5 described above, a pile hole H having a depth reaching the support layer Gh in the deep underground is assumed in step (e). Then, the bucket B2 was pulled up and the excavation depth was measured in the step (f), and then suspended by the winch wire W1 of the earth drill excavator DM and held through the yoke Y as shown in FIG. The penetration tester 10 is connected to the tip of the kelly bar K instead of the bucket B2, and the penetration tester 10 is inserted into the pile hole H filled with the stabilizing liquid Ls and settled on the pile bottom Hb. Then, the support strength of the pile bottom Hb is measured by the operation of the penetration testing machine 10.

  The penetration testing machine 10 uses a standard penetration testing apparatus that has been widely used for determining the N value of the ground, and as shown in FIGS. 2 and 3, A guide cylinder 43 having a square cross section is disposed in the center, and a cylindrical hammer casing 5 is loaded in the guide cylinder 43 so as to be movable up and down, and the knocking block 1 is installed at the lower end of the hammer casing 5 on the proximal side. It is fixed by the disc part 12, and the penetrating shaft 11 of the knocking block 1 penetrates the lower end side of the main body casing 4 through the cylindrical water sealing packing 44 and protrudes downward. Further, as shown in FIG. 3, the guide cylinder 43 comprises guide frame portions 43a having a substantially square cross section in the longitudinal direction at the inner four corners, and the guide frame portions 43a are in sliding contact with the hammer casing 5. The resistance is reduced. In the hammer casing 5, a hydraulic cylinder 31 having a downwardly extending telescopic rod 31a as a lifting mechanism 3 is fixed on the upper side, and a drive hammer 2 is loaded below the hydraulic cylinder 31 so as to be movable up and down.

  A pair of hooks 32, 32 having inwardly engaging claws 32a at their lower ends are pivotally attached to the distal end portion of the telescopic rod 31a of the hydraulic cylinder 31 via pivot pins 31b at intermediate portions so that they can be opened and closed with each other. In addition, a pair of grip release flanges 34, 34 whose inner side is tapered are fixed to the outer peripheral portion of the lower end of the hydraulic cylinder 31. Both hooks 32 and 32 are normally biased in the closing direction via springs 33, and the outer portion 32 b at the upper end of each hook 32 has a tapered shape corresponding to the inner portion of the grip release flange 34. . On the other hand, on the upper surface side of the drive hammer 2, a locking shaft 21 having a top portion having a large cone portion 21a is implanted.

  As shown in FIGS. 2 (a) and 4 (a), the lifting mechanism 3 is configured such that when the telescopic rod 31a of the hydraulic cylinder 31 is extended, the locking claws 32a and 32a of both hooks 32 and 32 are locked. 21. The hooks 32 and 32 are brought into contact with the tapered surface of the conical portion 21a and are tilted to cause the engaging claws 32a and 32a overcoming the conical portion 21a to be engaged with the lower side of the conical portion 21a. To do. Next, when the telescopic rod 31a is shortened in this engaged state, the drive hammer 2 is gripped and lifted as shown in FIG. 2B, but when the telescopic rod 31a is further retracted, FIG. 4B, the outer portions 32b of the upper ends of the hooks 32 and 32 are brought into contact with the grip release flange 34 at the tapered surfaces, and the hooks 32 and 32 are urged by the spring 33 by the inclination inducing action. When the drive hammer 2 released from gripping freely falls and hits the bottom plate 11 of the hammer casing 5, the hammer casing 5 is lowered by this striking force, and the knocking block 1 The penetration shaft 11 is protruded downward.

  The penetrating shaft 11 of the knocking block 1 has a cylindrical shaft shape with an open tip so that a geological sample can be collected. Although not shown, a tip shoe, an intermediate split barrel, The base end side of the connector head containing the ball valve is screwed coaxially and integrated.

  As shown in FIGS. 2A to 2C, the main body casing 4 includes a cylindrical member 40 and end members 41 and 42 that are detachably fitted to the top and bottom of the main body casing 4 with bolts. An inspection window 45 is provided on the peripheral surface near the lower portion of the member 40, and the upper and lower end members 41 and 42 are both tapered by tapered peripheral surface portions 41a and 42a. The guide cylinder 43 has an upper end fixed to the upper end member 41, a lower end bolted to the inner mounting plate 42b of the lower end member 42, and a cylinder in an outward flange portion 43b provided on the upper side. It is bolted to an inward flange portion 40 a provided on the member 40. The upper end member 41 is provided with a kelly bar connecting portion 46 and a cable connecting portion 47, while a plurality (four in the illustrated case) are provided on the taber-shaped peripheral surface portion 42a of the lower end member 42. The grounding legs 6 are equally formed in the circumferential direction.

  Further, the body casing 4 utilizes an annular space 40b between the guide cylinder 43 and sensors 7 and 7 for detecting the drive hammer 2 at the upper limit position and the lower limit position, and the amount of settlement of the hammer casing 1 is measured. An encoder 8 is built in, and an automatic measuring device on the ground (not shown) is provided via a hydraulic / electric cable Ca (see FIG. 1) connected to the cable connecting portion 47 with the detection signals of the sensors 7 and 7 and the measurement signal of the encoder 8 connected to the cable connecting portion 47. ), The number of hits (N value) is counted and recorded and displayed, and the amount of subsidence per hit, that is, the amount of penetration of the knocking block 1 into the ground and the total amount of penetration is recorded and displayed. Is done.

  In the pile construction management method of the present invention, the penetration shaft 11 of the knocking block 1 penetrates from the hole bottom Hb to a predetermined depth by operating the penetration testing machine 10 that is attached to the pile bottom Hb as shown in FIG. The number of hits required is measured, and it is determined whether or not the support strength of the ground of the pile bottom Hb is greater than or equal to a predetermined value based on the number of hits. Therefore, in the standard penetration test defined by JIS A 1219, the drive hammer 2 having a mass of 63.5 ± 0.5 kg is freely dropped by 76 ± 1 cm, and the knocking block 1 is hit, and the outer diameter is 51 ± 1 mm and the inner diameter is 35. Since the number of impacts required for the penetration shaft 11 of ± 1 mm to penetrate 30 cm into the ground is expressed as an N value, the penetration testing machine 10 used here can grasp the support strength as an N value in accordance with the standard penetration test. Good.

  If the support strength of the ground thus measured is equal to or higher than the predetermined value, the ground has sufficient support force at the tip of the pile as the support layer Gh, and it is determined that the pile can be built. 5 through the insertion of the reinforcing bar Rc in the step (g) in FIG. 5 to the pulling out of the stunt pipe Ps in the step (l), the cast-in-place pile P1 is built in the pile hole H, and the pile construction is performed. It can be completed quickly. On the other hand, if the support strength is less than a predetermined value, it is determined that piles cannot be built, so drill deeper, or backfill the pile holes H and drill new holes at different positions, Similarly, the support strength may be determined.

  The pile construction management method of 2nd Embodiment is applied to the construction of the ready-made pile by a pre-boring method. In this pre-boring method, first, as shown in step (a) of FIG. 6, the screw rod Rs of the earth auger A that moves up and down along a leader (not shown) such as a three-point pile driver is vertically set on the ground G. As shown in the step (b), the screw rod Rs is lowered while being rotated to excavate the ground G (soft layer Gs). As shown in the step (c), the support layer Gh in the assumed deep underground is formed. After forming the pile hole H with the depth to be reached, the screw rod Rs is pulled up, and a root-setting liquid Ls such as soil cement is injected as in the step (d), and then the hole periphery fixing liquid Lf as in the step (e). To the top of the pile hole H, and the screw rod Rs is extracted. Next, as shown in the step (f), the penetration tester 10 similar to the first embodiment is connected to the earth auger A via the connecting rod R1, and the penetration test is performed as shown in the step (g). The machine 10 is inserted into the pile hole H and settled, and the support strength of the pile bottom Hb is measured by the penetration test machine 10. In addition, CR shown to the figure of a process (g) is the reel of the hydraulic / electrical cable Ca connected to the penetration testing machine 10, and is installed in the pile driving machine.

  Even in this case, the penetration tester 10 is operated in the same manner as in the first embodiment, and the number of hits required for the penetration shaft 11 (see FIG. 2) of the knocking block 1 to penetrate from the hole bottom Hb to a predetermined depth is calculated. It measures and it determines whether the support strength of the ground of the pile bottom Hb is more than predetermined value based on the frequency | count of impact. If the supporting strength is equal to or greater than a predetermined value, the penetration tester 10 is lifted, and then, as shown in step (h), the ground auger A is ready-made such as a PHC pile or RC pile via a connecting rod R2. The pile P2 is connected, and this ready-made pile P2 is inserted into the pile hole H, and as shown in step (i), the ready-made pile P2 is embedded in the pile hole H and separated from the connecting rod R2, To complete. If the support strength is less than the predetermined value, as in the case of the first embodiment, deeper excavation is performed, or the pile hole H is backfilled and newly excavated at a different position and supported similarly. The strength may be determined.

  In the second embodiment, the penetration testing machine 10 is suspended and connected to the earth auger A via the connecting rod R1, but a pile driving machine equipped with an earth auger as in the third embodiment shown in FIG. Alternatively, the penetration tester 10 may be hung on a wire W2 of an auxiliary crane (not shown) separate from the vertical crane 9 and the penetration tester 10 may be inserted into the pile hole H to be bottomed. The CP shown in FIG. 7 is an automatic recording device installed on the ground, and is connected to a hydraulic / electric cable Ca extending from the penetration testing machine 10.

  As illustrated in the first to third embodiments, in the pile construction management method of the present invention, before the cast-in-place pile P1 and the ready-made pile P2 are built into the pile hole H drilled in the ground G, the penetration tester is used. 10 is inserted into the pile hole H to be bottomed, and the support strength of the hole bottom Hb is measured from the number of times the drive hammer 2 is hit for the knocking block 1 to penetrate from the hole bottom Hb to a predetermined depth (N Value) can be measured very easily and reliably. Therefore, when the support strength is equal to or greater than a predetermined value, the pile construction can be completed efficiently by building the pile in the pile hole H. If the support strength is less than the predetermined value, it is determined that the erection is impossible. Therefore, excavation is performed further deeply, or the pile hole H is backfilled and newly excavated at a different position, and similarly supported. Although the strength will be judged, a situation in which much labor, time and cost are spent to redo the pile erection work, as in the case where a lack of support strength was found in the loading test after the pile work was completed in the past. Can be avoided.

  In addition, since a standard penetration test apparatus that has been widely used for determining the N value of the ground can be used as the penetration test machine 10, no special new equipment is required to implement this pile construction management method. The construction cost can be reduced, and the international standard N value can be managed, so a high reliability evaluation of the measured value can be obtained. In addition, since the penetration testing machine 10 illustrated in the embodiment has a simple structure and can be manufactured at low cost, and has a plurality of grounding legs 6 around the lower end of the main casing 4, the bottoming posture in the pile hole H is Since the striking force due to the free fall of the drive hammer 2 is constant in a vertical state, the support strength can be determined more accurately.

  In the embodiment, the penetration tester 10 is inserted into the pile hole H filled with the liquid material (stabilizing liquid Ls, root hardening liquid Lh, hole circumference fixing liquid Lf), but the pile construction management method of the present invention. Then, it is possible to measure the supporting strength of the hole bottom ground by inserting and grounding the penetration tester 10 even in the pile hole H which is empty. Thus, when the penetration tester 10 is inserted for the pile hole H filled with the liquid material in order to suppress the hole wall collapse, the upper and lower end portions 4a and 4b of the main body casing 4 are both as in the embodiment. If the penetration tester 10 having a tapered shape is used, there is an advantage in that the collapse of the hole wall can be prevented more reliably because the disturbance of the liquid material when the penetration tester 10 is made to enter and exit is reduced.

  Further, by incorporating a sensor 7 that detects the upper limit position and the lower limit position of the drive hammer 2 as in the penetration testing machine 10 of the embodiment, the number of hits by the drive hammer 2 can be reliably captured by the output signal from the sensor 7. Moreover, there is an advantage that the amount of penetration into the hole bottom Hb caused by the knocking of the knocking block 1 can be accurately grasped by incorporating the encoder 8 for measuring the amount of settlement of the hammer casing 1.

  On the other hand, although the ready-made pile P2 is a concrete pile in 2nd Embodiment, the pile construction management method of this invention is applicable also to the construction method which inserts a steel pipe pile as a ready-made pile in the pile hole H. Moreover, the pile hole H which is the object of the present invention may be a bottomed hole whose bottom side is enlarged by a bottomed bucket or the like. On the other hand, the penetration testing machine 10 used in the present invention has the detailed configuration such as the configuration of the lifting mechanism 3, the detailed shape of the main body casing 4, the shape of the lifting guide portion of the hammer casing 5, the shape of the grounding leg 6, etc. It may be different from the example.

DESCRIPTION OF SYMBOLS 1 Knocking block 2 Drive hammer 3 Lifting mechanism 4 Main body casing 5 Hammer casing 5
6 Grounding leg 7 Sensor 8 Encoder 10 Penetration testing machine H Pile hole Hb Hole bottom G Ground Gh Support layer Lf Hole perimeter fixing liquid (liquid)
Lh root hardening liquid (liquid)
Ls Stabilizer (Liquid)
P1 Cast-in-place pile P2 Ready-made pile

If the means for achieving the above-mentioned object is shown with reference numerals in the drawings, the pile construction management method according to the invention of claim 1 is that after the pile hole H is drilled in the ground G, Before building the pile (the cast-in-place pile P1, the ready-made pile P2), the shaft-shaped knocking block 1 whose tip protrudes downward, the drive hammer 2 that strikes the knocking block 1 by free fall, and the drive after the fall A penetration tester 10 having a lifting mechanism 3 that lifts the hammer 2 and releases it at a predetermined height is inserted into the pile hole H and settled, and the knocking block 1 is required to penetrate from the hole bottom Hb to a predetermined depth. It determines strength of supporting the bottom hole Hb from the striking number of times, the support strength pile該杭hole H when a predetermined value or more (place pile P1, ready-made pile P2) a pile construction management method Tatekomu the ,
In the penetration testing machine 10, a cylindrical hammer casing 5 containing a lifting mechanism 3 and a drive hammer 2 is held up and down in a cylindrical main body casing 4, and the upper end of the knocking block 1 is placed at the lower end of the hammer casing 5. And the lower part (penetration shaft 11) of the knocking block 1 penetrates the lower end side of the main body casing 4 and protrudes downward to the outside. It is characterized by having a grounding leg 6 of a book.

According to a fourth aspect of the present invention, in the pile construction management method according to any one of the first to third aspects, the penetration testing machine 10 includes a sensor 7 that detects the drive hammer 2 at an upper limit position and a lower limit position.

According to a fifth aspect of the present invention, in the pile construction management method according to any one of the first to fourth aspects, the penetration tester 10 includes an encoder 8 for measuring the amount of settlement of the hammer casing 1.

Next, effects of the present invention will be described with reference numerals in the drawings. First, according to the invention of claim 1, before the pile (cast-in-place pile P1, ready-made pile P2) is built in the pile hole H drilled in the ground G, the penetration testing machine 10 is inserted into the pile hole H. From the number of hits of the drive hammer 2 required for the knocking block 1 to penetrate from the hole bottom Hb to a predetermined depth, the support strength of the hole bottom Hb is measured (N value) in an extremely simple and reliable manner. Since it can be measured, it can be determined that it can be built when the support strength is equal to or higher than a predetermined value, and a pile can be built in the pile hole H to complete the pile construction efficiently. On the other hand, if the support strength is less than the predetermined value, it will be impossible to embed it. Therefore, excavate deeper, or backfill the pile hole H and newly drill at a different position. This determination may be made. Therefore, it is possible to avoid a situation in which a great amount of labor, time and cost are spent to redo the pile erection work, as in the case where a lack of support strength is found in a loading test after completion of the pile work in the past. In addition, since a standard penetration testing device that has been widely used for determining the N value of the ground can be used as the penetration testing machine 10, no special new equipment is required to implement this pile construction management method. There are advantages that the construction cost can be reduced and the international standard N value can be managed, so that a reliable evaluation of the measured value can be obtained.
In addition, according to the present invention, the penetration tester 10 can be manufactured with a simple structure at a low cost, and the plurality of grounding legs 6 are provided around the lower end of the main casing 4. Since the bottoming posture is stable in the vertical state and the hitting force of the drive hammer 2 is constant, the support strength can be determined more accurately.

According to the invention of claim 2 , when the penetration tester 10 is inserted into the pile hole H, the inside of the pile hole H is filled with liquid substances (stabilizing liquid Ls, root-solidifying liquid Lh, hole peripheral fixing liquid Lf). Since it carries out in a state, collapse of the hole wall by the entrance / exit of the penetration testing machine 10 can be suppressed.

According to the invention of claim 3 , since the upper and lower ends 4a, 4b of the main casing 4 of the penetration testing machine 10 are both tapered, the inside of the pile hole H is a liquid material (stabilizing liquid Ls, rooting liquid Lh). In this state, the disturbance of the liquid material when the penetration tester 10 is made to enter and exit is reduced, and the collapse of the hole wall can be prevented more reliably.

According to the invention of claim 4 , since the penetration tester 10 incorporates the sensor 7 for detecting the upper limit position and the lower limit position of the drive hammer 2, the number of hits by the drive hammer 2 is surely determined by the output signal from the sensor 7. Can be caught.

According to the invention of claim 5 , since the penetration tester 10 incorporates the encoder 8 for measuring the amount of settlement of the hammer casing 1, the amount of penetration into the hole bottom Hb due to the knocking block 1 being hit can be accurately captured. .

Claims (6)

  After drilling a pile hole in the ground, before laying the pile into the pile hole, a shaft-shaped knocking block whose tip protrudes downward, a drive hammer that strikes the knocking block by free fall, A penetration tester equipped with a lifting mechanism that lifts the drive hammer and releases it at a predetermined height is inserted into the pile hole and settled down, and the bottom of the hole is calculated from the number of times that the knocking block penetrates from the hole bottom to the predetermined depth. The pile construction management method characterized by determining the support strength of this and building a pile in this pile hole when this support strength is more than predetermined value.   The pile construction management method according to claim 1, wherein the penetration testing machine is inserted into the pile hole in a state where the pile hole is filled with a liquid material.   The pile construction management method according to claim 2, wherein the penetration tester has a tapered shape at both upper and lower ends of the cylindrical main body casing.   In the penetration testing machine, a cylindrical hammer casing containing the lifting mechanism and a drive hammer is held in a cylindrical main body casing so as to be movable up and down, and an upper end portion of a knocking block is fixed to a lower end of the hammer casing. The lower side of the knocking block penetrates the lower end side of the main casing and protrudes downward and has a plurality of grounding legs around the lower end of the main casing. Pile construction management method.   The pile penetration management method according to any one of claims 1 to 4, wherein the penetration testing machine includes a sensor for detecting a drive hammer at an upper limit position and a lower limit position.   The pile penetration management method according to any one of claims 1 to 5, wherein the penetration testing machine includes an encoder for measuring a sinking amount of a hammer casing.

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