JP4753132B2 - Pile hole drilling method - Google Patents

Description

  Pile hole excavation method characterized by the procedure of processing and managing excavation data related to pile hole excavation when constructing a pile hole excavation (pre-excavation method, medium excavation method) when building a ready-made pile About.

  In particular, the present invention is suitable for the creation of foundation piles using ready-made piles, or the management of excavation work, and is a method that can be expected to be effective for the creation of reliable and stable pile holes or the reduction of excavated soil. is there. In particular, when embedding prefabricated piles with irregularities at the bottom and side surfaces, high-quality pile hole formation is required, and the prefabricated piles are installed at the roots of pile holes. It is effective for the creation of foundation piles that develop stable and reliable bearing capacity.

  Conventionally, the following methods for managing pile hole excavation have been proposed.

(1) Invention of Patent Document 1

  Usually, in the pre-digging method, a drilling rod attached to a pile hole excavator is rotated, and a drilling hole with a predetermined diameter is excavated from the ground surface with a drilling head at the tip of the drilling rod. A pile hole is created.

  This root consolidation part is expanded as necessary and excavated as an expanded bottom consolidation part. Cement milk is injected into the pile hole and mixed with excavated soil to form soil cement. The bottom of the ready-made pile is submerged in this soil cement layer to solidify and integrate the soil cement. . In the support pile, the load on the ground was transmitted from the lower end portion of the ready-made pile to the support layer through the soil cement layer to develop a predetermined support force. Therefore, in the support pile, it was necessary to determine the support ground and to form the pile hole consolidation portion at an appropriate depth.

  In excavation of this pile hole, by monitoring the load current value of the auger that rotates the drill rod, the position of the hard support layer is ascertained by the correlation between the hardness of the ground and the load current value, and the solidified part is located at that position. The pile hole excavation is managed by constructing.

  In other words, the geological survey data collected in advance or the surrounding geological survey data (usually the N value of the standard penetration test) is displayed for each depth, and the pile load excavator auger load current integration during pile hole excavation The excavation was performed while comparing the value (excavation current x excavation time) with the geological survey data, and the position where the integrated current value was increased near the ground depth of a predetermined N value was recognized as the depth of the supporting ground. In addition, since the strength of the root consolidation part is an important factor for the expression of bearing capacity, various measured values of drilling data, water injection amount, cement milk injection amount, etc. are recorded and displayed. It also controlled the cement milk injection depth and amount, and the agitation operation of the drilling head.

(2) Patent Document 2

  In pile hole excavation, in order to level the inner wall of the pile hole so that the ground is not destroyed by the excavation blade, or to excavate the pile hole efficiently, the excavation blade with the rotation speed N of the excavation rod, the descending speed v, and the same height An invention is disclosed in which excavation is managed under optimum conditions according to the characteristics of the ground by variously adjusting the number n, the length L of the excavating blade in the axial direction, and the like. Moreover, this optimal condition was properly used for excavation of the pile hole shaft and excavation of the pile hole consolidation part.

At this time, the amount of drilling water injected is measured at each drilling depth, together with the rotation speed N of the drilling rod, the lowering speed v, the number n of drilling blades of the same height, the axial length L of the drilling blade, etc. Was recording data.
JP 2002-348868 JP2003-213679A

  Generally, when excavating, if there is more water around the excavating head, the ground becomes soft and the time required for excavation can be shortened. However, excessive water injection has caused the collapse of pile hole walls and increased the volume of excavated mud that must be treated so that excess water can be lifted to the ground and discarded.

  In the prior art, water injection amount data can be stored and displayed on the excavation management display. However, the data could not be provided so that the excavation management operator could make full use of the data. Therefore, as a result, the excavated pile hole varied in the total amount of injected drill water, the specific gravity of the mud in the pile hole varied, and the amount of soil discharged also varied according to this variation. Therefore, the cost for industrial waste management is increased, which is not preferable from the viewpoint of environmental management.

  However, according to the present invention, since the accumulated current value of the auger is processed at the time of excavation of the pile hole, and the value as energy is utilized for excavation management of the pile hole, the above-mentioned problems are solved.

That is, the present invention is a method of excavating the ground with a drilling rod having a drilling head at the tip to form a pile hole, and the value of Ep is set in advance or during a drilling operation according to the following equation 1. In this case, the pile hole excavation method is characterized in that, when the value becomes, the ground is estimated as the supporting ground, and a solidified portion of the pile hole is constructed.
A _ave1 is an average integrated current value when excavating at a depth L ₁ at an excavation speed v ₁ in a certain section. V is the auger voltage of the excavator. D is a pile hole diameter.
(Expression 1) Ep = A _ave1 × V / (v ₁ · D ² · π / 4)
[J / m ³ ] (= [W · S / m ³ ])

  Further, another invention is a method of forming a pile hole by excavating the ground with a drill rod having a drill head at the tip, wherein the pile hole is drilled as follows Excavation method.

(1) According to the following formula 1, when excavating a pile hole, the excavation load current is measured for each depth, the excavation load current is converted into an energy amount, and the data A is stored as data A in relation to the depth. .
A _ave1 is an average integrated current value when excavating at a depth L ₁ at an excavation speed v ₁ in a certain section. V is the auger voltage of the excavator. D is a pile hole diameter.
(Expression 1) Ep = A _ave1 × V / (v ₁ · D ² · π / 4)
[J / m ³ ] (= [W · S / m ³ ])
(2) The N value of the standard penetration test is converted into an energy amount according to the following formula 2, and the data B is stored as data B in association with the depth.
m is the mass of the hammer of the standard penetration test, h is the drop height of the hammer, and φ is the sectional area of the cone. g is a gravitational acceleration. N is an N value.
(Formula 2) En = mgh · N / (0.3 × φ) [J / m ³ ] (= [W · S / m ³ ])
(3) Drilling while displaying data A in (1) and data B in (2) in comparison with each depth.

Moreover, in the above, the pile hole excavation method is characterized by performing the following processing.
(1) Data C is stored with the appropriate amount of excavated water generated in association with the ground type and N value at each depth as data C.
(2) A value obtained by correcting data A with data C is stored as data AA in association with each depth.
(3) Display data AA instead of data A.

Moreover, in the above, it is a pile hole excavation method characterized by taking the following procedures.
(1) Set the amount of drilling water to be injected in advance according to the soil quality.
(2) Estimate the soil quality grasped from data A and data B.
(3) The drilling water determined in (1) is injected based on the estimated soil quality.

(1) Since the value Ep obtained by converting the integrated current value into energy is displayed, it is easy to grasp the supporting ground, and the solidified part can be reliably constructed at a more appropriate depth to improve the quality of the pile hole. Can do. In this case, the quality can be further improved by multiplying the excavation correction coefficient for each construction site to correct the energy-converted value Ep.

(2) Convert the N value of the standard penetration test (number of times of driving at the time of the test) into an energy amount, and further convert or further correct the excavation load current into a similar energy amount, and compare them for each depth. By displaying, changes in excavation work contents and changes in quality (soil quality and ground strength) during excavation can be easily grasped in real time.

(3) The specific gravity of the drilling mud can be maintained at a constant level by adjusting the amount of water injected during excavation according to the soil quality before or during the excavation work. The excavated soil and the excavated water are appropriately mixed, and the separation between the two can be reduced. That is, the specific gravity of the soil cement after cement milk injection can be controlled to be constant (predetermined range).

  Therefore, the excavated soil and the excavated water are not separated, and the possibility of the separated sediment of the excavated soil or the collapse of the pile hole wall is greatly reduced. The construction period of piles can be stabilized.

  In addition, since the amount of water injected is reduced by appropriately controlling the amount of water injected into the pile hole during excavation, the amount of soil discharged during the formation of the pile hole can be reduced by an amount corresponding to the injected amount, that is, about 20%. is there. Therefore, the environmentally friendly high bearing capacity construction method becomes an even more environmentally friendly construction method.

(4) By comparing the display of the N value and the excavation load current in the same unit, it is possible to grasp the variation similar to each excavation work and the soil quality of the pile hole in a realistic and accurate manner. By controlling the drilling water injected according to the soil quality, it is possible to manage the specific gravity of the mud in the stable pile hole.

(5) Since the injection amount of drilling water is also displayed realistically together with the unit energy value of the ground, the drilling operator can easily and reliably adjust and manage at a glance.

(1) In a certain section, data obtained by converting excavation load current (integrated current value) into energy per unit volume is defined as “integrated resistance value”. That is, the integrated resistance value is a value obtained by dividing the integrated current amount by the excavation speed (unit: excavation depth / elapsed time) and the excavation cross-sectional area.

Regarding the accumulated current amount ΣA in the accumulated resistance value, excavation is considered as a function of electric energy, and for excavation, the amount of electric power (W · sec) required for excavation in that section is calculated from the accumulated current amount in the unit section. The electric energy Ep (W · sec / m ³ ) required for excavation per unit volume of the section is obtained by calculating and dividing by the excavation volume of the section (section length × excavation cross-sectional area).

Section 1, at a depth _{L 1,} time drilling takes _{T 1,} an average integrated current A _ave1. Since the voltage of the auger of the excavator is 200 (V), the amount of power required for excavation in the section 1 is
A _ave1 × 200 × T ₁
It becomes.

Therefore, Ep is calculated | required if converted per unit excavation volume.
Ep = A _ave1 × 200 × T ₁ / (L ₁ · D ² · π / 4)
[W · S / m ³ ] (= [J / m ³ ])
= A _ave1 × 200 / ((L ₁ / T ₁ ) · (D ² · π / 4) [J / m ³ ]
= A _ave1 × 200 / (v ₁ · D ² · π / 4) [J / m ³ ]
Here, v ₁ is a drilling speed of tunneling in the depth direction,
v ₁ = L ₁ / T ₁ [m / sec]
It is.
The Ep data thus obtained is stored in association with each depth.

(2) On the other hand, the N value is defined as the number of hits for dropping a hammer of mass m (= 63.5 kg) from a height h (= 75 cm) and penetrating a cone (sampler) 30 cm. In this case, the cross-sectional area of the cone is φ (cm ² ).

Since the N value is considered as a function of the potential energy of the hammer, the amount of penetration energy (potential energy) per unit volume in the 30 cm penetration section is defined as En.
En = mgh · N / (0.3 × φ) [J / m ³ ]
In this way, the obtained En data is stored in association with the depth.

(3) Ep and En obtained in this way were expressed in coordinates with the digging depth as the vertical axis and the horizontal axis as the energy per unit volume (FIG. 2). Actually, the En data is stored in advance, the Ep data is calculated for each depth during the excavation of the pile hole, and the En data and the Ep data are superimposed and displayed on the excavation management screen ( 2) or displayed side by side (not shown).

The En data and the Ep data have the same energy dimension (FIG. 3). In FIG. 2, it can be seen that En and 10 × Ep are in a substantially proportional relationship. In general,
En = k × Ep (k: excavation correction coefficient)
There is a relationship.

(4) Regarding the relationship between soil quality and water injection volume, in the case of silt layer, the conventional water injection volume has a lower specific gravity, the excavated soil is separated, the excavated mud is increased, and it tends to stay high during anti-sinking. Therefore, the amount of drilling water injected is adjusted according to the soil quality.

  Also, if the specific gravity of drilling mud is low, it will not be mixed well and will be separated easily, so the specific gravity should be set high, but since the specific gravity of the soil cement in the rooting part is 1.7, the mixing management with the soil cement is ensured Therefore, it is desirable to keep the specific gravity of drilling mud below 1.6, and if possible, to around 1.5.

(5) In the pile hole excavation method of the present invention, as described above, the set En and Ep are displayed on the personal computer screen of the operator room or the control room of the excavator during the excavation work. While digging. Such En, Ep information, and N value information of the ground or the surrounding ground are displayed in association with ground type information and the like. By comparing these displays, it is possible to more accurately grasp that the excavation head has reached the support ground. After reaching the supporting ground is confirmed, a rooting portion is constructed at the bottom of the pile hole by a conventional method.

(6) The adjustment of the water injection amount in the above is performed, for example, by statistically processing data including excavation data in the past site and the water injection amount data, and setting an optimum water injection amount for each depth in the ground. To do. The past excavation data is one or a plurality of data such as ground type, N value, excavation load current and the like. In addition, by applying the optimal water injection amount data to the ground during excavation work and comparing it with the actual water injection amount, it is possible to correct the Ep value and display the corrected Ep data.

  An embodiment of the present invention will be described with reference to FIGS. Data was collected and analyzed during pile hole excavation, and the correlation between the integrated resistance value and N value was confirmed.

(1) In the pile driving machine 1, an auger 3 is installed on a mast 2 so as to be movable up and down, and an excavation rod 4 is attached to the auger 3 so as to be rotatable. The excavation rod 4 has an excavation head 5 at the tip, and the excavation head 5 has an excavation blade 7 formed at the tip of the excavating arms 6 and 6 that swing.

  Further, a hose 9 of a drilling water supply device 8 is connected to the pile driving machine 1 so that drilling water can be supplied to the drilling head 5.

In the pile driving machine 1, excavation of the pile hole 17 is started from the ground 16 with the excavation head 5. According to pile hole 17 drilling,
・ Accumulated current value of the auger 3 from the current measuring device 10 ・ Depth data for measuring the feed amount with the depth meter 12 by the depth / speed meter measurement wire 11 ・ Speed data for excavation ・ From the flow meter 13 digging water and cement milk The injection flow rate data is measured, stored in the personal computer of the operator seat 14 and processed, and the related data is displayed on the monitor of the personal computer of the operator seat 14. The operator can manage excavation while looking at the screen. The data stored in the personal computer at the operator seat 14 is sent from the antenna 15 to a data processing room installed in another room and processed (FIG. 4).

(2) The same study was conducted with 60 data sites (300). Furthermore, using the data from 8 sites (40 cases) by the same operator, the effect of "individual differences in construction" was also investigated.

(3) In order to quantitatively grasp the relationship between the ground and excavation resistance, the N value was compared with the corrected integrated resistance value (considering the influence of the amount of excavation water). FIG. 5 shows the fine sand layer data. FIG. 5A shows the whole (a plurality of operators: the number of data 1223), and FIG. 5B shows the data of one operator (the number of data 203).

For the entire data, the regression equation was integrated resistance value R = 12.7N × 10 ³ and correlation coefficient r = 0.40. For the average value of the integrated resistance values for each N value (circles), the regression equation was R = 12.5N × 10 ³ and the correlation coefficient r = 0.93. Further, in the case of the fine sand layer, the average value of the integrated resistance value tended to be different in the three groups having N values of 0 to 20, 25 to 40, and 40 or more.

On the other hand, as a result of analyzing the data by limiting one operator (same construction machine), the regression equation is integrated resistance value R = 5.0N × 10 ³ , correlation coefficient r = 0.68, and the entire data (FIG. 5 (a )) The correlation coefficient became larger. Further, as can be seen from FIG. 5B, the width of the data variation is considerably narrow. For the average value of the integrated resistance values for each N value (circles), the regression equation was R = 4.6N × 10 ³ , the correlation coefficient r = 0.93, and the correlation coefficient was the same as the whole data. Moreover, the average value of the integrated resistance value tended to be different in the three groups as in the whole data, but the N value interval was 0-25, 30-45, 50 or more, and the whole data The result was slightly different. However,
Electric energy Ep = (Integrated resistance value) × (Auger voltage)
It is.

(4) As described above, for excavation, first, the electric energy [W · sec] required for excavation of the section is calculated from the accumulated current amount of the unit section, and the excavation volume (section length × excavation) of the section is calculated. Dividing by the cross-sectional area), an electric energy Ep [W · sec / m ³ ] required for excavation per unit volume in the section is obtained. The N value is N times the potential energy mgh of the weight, divided by the unit volume (30 cm × cone cross-sectional area), and the amount of penetration energy En [ J / m ³ ] is calculated.

Because these two energies are of the same dimension, En∝k × Ep
(Fig. 3). Here, k is an excavation correction coefficient, and is a constant that varies depending on the ground type (sandy soil, cohesive soil, gravel, etc.). This excavation correction factor is considered to be influenced by excavation conditions such as construction depth, amount of excavated water, and individual differences during construction.

Comparative examples of Ep and En are shown in FIGS. Both tendencies are very similar and the correlation is high. In these two examples, the constant k is about 10 in total,
En ≒ 10 × Ep
There is a relationship.

(5) From the above, the following results were obtained.

  In the investigation of the relationship between the corrected integrated resistance value and the N value, the number of individuals as a whole increased as a whole (a plurality of operators), and the influence of variations due to individual differences and individual differences increased. In addition, as a result of considering only one operator / construction machine, the width of variation was smaller than that studied by a plurality of operators. The excavation correction coefficient is set and displayed every time excavation work is performed at the construction site, and by performing fine construction management, a desired pile hole can be excavated more stably.

  Further, as a result of examining the relationship between the integrated resistance value and the N value from the viewpoint of energy, a correlation between Ep and En was recognized (FIGS. 6 and 7).

It is a graph of the depth-digging current value used for implementation of this invention. It is a graph of "depth-energy" which compares the integrated resistance value Ep of this invention with the N value data En converted into energy. It is the figure which outlined the relationship between Ep and En of this invention. It is a front view of the pile hole excavator used in the Example of this invention. It is a graph showing distribution in the integrated resistance value in N value, (a) Data of all operators, (b) represents data of individual operators, respectively. It is a graph showing the relationship between depth and Ep and En. It is a graph which similarly represents the relationship between depth and Ep and En.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pile driver 2 Mast 3 Auger 4 Drilling rod 5 Drilling head 6 Drilling arm 7 Drilling blade 8 Drilling water supply device 9 Hose 10 Current measuring device 11 Wire 12 Depth meter 13 Flow meter 14 Operator room 15 Antenna 16 Ground 17 Pile hole

Claims (4)

This is a method of excavating the ground with a drilling rod having a drilling head at the tip to form a pile hole, and the value of Ep becomes a preset value or a value set during excavation work according to the following formula 1. A method for excavating a pile hole, characterized in that the ground is estimated as a supporting ground, and a solidified portion of the pile hole is constructed.
A _ave1 is an average integrated current value when excavating at a depth L ₁ at an excavation speed v ₁ in a certain section. V is the auger voltage of the excavator. D is a pile hole diameter.
(Expression 1) Ep = A _ave1 × V / (v ₁ · D ² · π / 4) [J / m ³ ] A method for excavating the ground with a drill rod having a drill head at the tip to form a pile hole, wherein the pile hole is excavated as follows.
(1) According to the following formula 1, when excavating a pile hole, the excavation load current is measured for each depth, the excavation load current is converted into an energy amount, and the data A is stored as data A in relation to the depth. .
A _ave1 is an average integrated current value when excavating at a depth L ₁ at an excavation speed v ₁ in a certain section. V is the auger voltage of the excavator. D is a pile hole diameter.
(Expression 1) Ep = A _ave1 × V / (v ₁ · D ² · π / 4) [J / m ³ ]
(2) The N value of the standard penetration test is converted into an energy amount according to the following formula 2, and the data B is stored as data B in association with the depth.
m is the mass of the hammer of the standard penetration test, h is the drop height of the hammer, and φ is the sectional area of the cone. g is a gravitational acceleration. N is an N value.
(Formula 2) En = mgh · N / (0.3 × φ) [J / m ³ ]
(3) Drilling while displaying data A in (1) and data B in (2) in comparison with each depth. The pile hole excavation method according to claim 2, wherein the following processing is performed.
(1) Data C is stored with the appropriate amount of excavated water generated in association with the ground type and N value at each depth as data C.
(2) A value obtained by correcting data A with data C is stored as data AA in association with each depth.
(3) Display data AA instead of data A. The pile hole excavation method according to claim 2 or 3, wherein the following procedure is taken.
(1) Set the amount of drilling water to be injected in advance according to the soil quality.
(2) Estimate the soil quality grasped from data A and data B.
(3) The drilling water determined in (1) is injected based on the estimated soil quality.