JP4837849B2 - Construction method of soil cement composite pile - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for constructing a soil cement pile in which a steel pipe pile is inserted into a formed soil cement column, and more particularly, a soil cement composition in which a bladed steel pipe pile is inserted into a formed soil cement pillar. It relates to the method of building piles.
[0002]
[Prior art]
It is described in, for example, JP-A-1-250523, that a soil cement pillar having a lower end reaching a support layer is formed in the ground, and a steel pipe or the like is inserted into the soil cement pillar to form a soil cement composite pile. As is known.
[0003]
[Problems to be solved by the invention]
In the ground where a soft and viscous soil layer exists, the above conventional method is a useful method for preventing the uneven settlement of the structure. However, constructing a long soil cement pile up to the support layer in the ground increases the amount of solidified material to be injected and increases the material cost, and it takes more time for construction because it requires deeper excavation and requires large construction machinery. Therefore, not only the cost is increased, but the amount of soil discharged to the ground is increased by the amount of solidified material and water to be injected, and the treatment cost is also increased. Moreover, since the steel pipe pile is buried up to the support layer, the burial time and the material cost of the steel pipe pile increase.
[0004]
The object of the present invention is to relieve the consolidation settlement of the soft soil layer even if the soft soil soil layer exists even if the lower end does not reach the support layer, and the amount of settlement of the structure is within the allowable settlement range. An object of the present invention is to provide a method for producing a soil cement synthetic pile that can be stored and has a horizontal resistance in the vicinity of the ground surface portion that is further superior to the above known one.
[0005]
[Means for Solving the Problems]
As shown in FIG. 1, the first invention inserts a winged steel pipe pile having wings at least near the head and the bottom of the pile into a soil cement pillar formed on the ground where a soft viscous soil layer exists. A method for constructing a soil cement composite pile, wherein the hollow portion of the winged steel pipe pile is hollow so that air in the hollow portion acts as buoyancy, and the length of the soil cement column existing below the winged steel pipe pile The length (Ls) is 0.5 to 3 times the length of the steel pipe pile, and the soil cement composite pile has a lowermost part of the soil cement column that does not reach the supporting ground.
[0006]
The second invention is a method for constructing a soil cement synthetic pile used in a design in which a structure is supported by a large number of soil cement synthetic piles in the ground where a soft and viscous soil layer exists. using the winged steel pipe pile is present wings around at least the head and near the Kuisoko section as steel pipe pile, the bottom of a number of soil cement pillar does not reach to the supporting ground, of the large number of soil cement pillar The surface connecting the tips has a convex shape protruding downward, and the hollow part of each winged steel pipe pile is in a hollow state so that the air in the hollow part acts as buoyancy, and exists in the lower part of each winged steel pipe pile The length of soil cement columns (Ls) is 0.5 to 3 times the length of steel pipe piles, and the mutual spacing (B) of soil cement columns is 2 to 20 times the diameter of soil cement columns. Has a length of Sea urchin is a reclamation process of soil cement synthetic pile to construct a soil cement synthetic pile.
[0007]
In any of the above forming methods, a winged steel pipe pile having wings at least near the head and near the pile bottom is used. Therefore, a wing part may exist in the middle part of a steel pipe pile, and does not need to exist.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As shown schematically in Fig. 2, the length of this steel pipe pile is not less than the length to the depth at which the bending moment and shear stress generated in the steel pipe pile when the horizontal load is applied to the pile head are almost zero. As shown schematically in FIG. 3, it is sufficient that the length is sufficient to support the structural load with the peripheral friction force in all the soil cement composite piles that support the structure.
[0009]
If it is more than such length, it is enough as the length of a steel pipe pile. However, if the length of the steel pipe pile is made longer than necessary, the material cost of the steel pipe pile becomes high, and the time for embedding the steel pipe will be excessive, and should be avoided.
[0010]
This steel pipe pile part is also a soil cement composite pile in which a winged steel pipe pile with wings at least near the head and the bottom of the pile is inserted into the soil cement pillars that have been created. Compared to a soil cement composite pile using steel pipe piles that do not have wings near the head, the soil cement composite pile is more excellent in horizontal resistance near the ground surface.
[0011]
On the other hand, the length (Ls) of the soil cement column is the length existing in the lower part of the winged steel pipe pile by the length of 0.5 to 3 times the length of the steel pipe pile, and the lowermost part of the soil cement column. Is the length that does not reach the supporting ground.
[0012]
If this length is less than 0.5 times the length of the steel pipe pile, the soil cement length is shorter than the thickness of the soft viscous soil layer that may cause consolidation settlement, thus reducing the consolidation settlement of the soft viscous soil layer. There is little effect to do. As a result, the subsidence amount of the structure may exceed the range of the allowable subsidence amount (especially the permissible value for pile foundations) shown in Section 4.4 of the “Building Foundation Structural Design Guidelines” of the Architectural Institute of Japan. On the contrary, if the steel pipe pile length exceeds 3 times, the amount of settlement of the structure will be within the range of the allowable settlement, but it is disadvantageous in terms of construction and cost as mentioned above due to the long soil cement column. Should be avoided.
[0013]
In the present invention, the steel pipe pile used is a winged steel pipe pile having wings at least near the head and the bottom of the pile, and the winged steel pipe pile and the soil are bonded to each other by the adhesion effect between the wing and the soil cement column. The cement pillar is integrated, and the load acting on the pile head is smoothly transmitted to the soil cement pillar via the wings and further to the ground, so there is a steel pipe pile as shown in FIG. The structure can be supported by exerting a large peripheral frictional force at the portion.
[0014]
Furthermore, in this invention, the steel pipe pile used is a winged steel pipe pile having wings at least near the head and the bottom of the pile, and since this pile is inserted into the soil cement column, the load on the upper structure Is transmitted to the bottom of the pile through the shaft of the winged steel pipe pile, and is transmitted to the soil cement pillar through the wing at the bottom of the pile. In order to resist by the supporting force of the column, it exerts a large vertical supporting force compared to the case where there is no soil cement column at the bottom of the pile.
[0015]
When the bottom of the winged steel pipe pile is closed by the bottom plate, the hollow part of the steel pipe pile can be present in a hollow state, and the air in the hollow part of the steel pipe pile acts as buoyancy. , The settlement suppression effect is improved.
[0016]
Furthermore, when it is used in a design where the structure is supported by a large number of soil cement composite piles in the ground where soft clay soil exists, the wings are at least near the head and the pile bottom as steel pipe piles in the soil cement composite piles. The winged steel pipe pile with a part is used, the bottom part of the soil cement column does not reach the supporting ground, and the length (Ls) of the soil cement pillar existing at the lower part of the winged steel pipe pile is the steel pipe pile. Soil cement composite piles were created so that the distance between the soil cement columns (B) was 2 to 20 times the diameter of the soil cement columns. It is preferable to do.
[0017]
When soil cement composite piles are constructed at such intervals, a ground in which the soil cement columns existing at the lower part of the steel pipe pile and the soft and soft soil layers present around the composite are formed, that is, a composite ground is formed.
[0018]
As a result, since the composite ground has higher rigidity than a soft viscous soil layer in which no soil cement column is present, the consolidation settlement phenomenon is alleviated and the uneven settlement of the structure can be prevented.
[0019]
If the distance (B) between the soil cement columns is less than twice the diameter of the soil cement columns, the soil cement composite piles are close to each other. Support force due to surface friction is reduced. As a result, in order to obtain a predetermined bearing capacity, it is necessary to construct a large number of soil cement composite piles, which is uneconomical.
[0020]
Conversely, if the distance (B) between the soil cement columns exceeds 20 times the diameter of the soil cement columns, the load that one soil cement composite pile should bear increases, and the length of the winged steel pipe pile increases. It is necessary to increase the diameter and thickness of the steel pipe part of the winged steel pipe pile or to enlarge the wing, which is not economical, and the depth section where the soil cement composite pile exists The effect of restraining the soft clay ground in the area is reduced, and the effect of reducing the consolidation settlement is reduced.
[0021]
As a precaution, the length (Ls) of the soil cement columns existing in the lower part of the above-described winged steel pipe pile and the actual length of the mutual interval (B) between the soil cement columns are specifically exemplified below. .
[0022]
For example, when the length of the steel pipe pile is 10 meters, the length of 0.5 times to 3 times the length of the steel pipe pile is in the range of 5 meters to 30 meters. Therefore, in this case, the length (Ls) of the soil cement column existing in the lower part of the winged steel pipe pile may be set in the range of 5 to 30 meters. Of course, it may be within this range. For example, the length may be changed as shown in FIG.
[0023]
On the other hand, when the diameter of the soil cement column is 0.6 m, the distance (B) between the soil cement columns is 2 to 20 times the diameter of the soil cement column is 1.2 m to 12 m. Meter.
[0024]
For example, as shown in FIG. 5, when there are portions where the heights of the structures are different, it is preferable to construct the soil cement synthetic piles under the same conditions in the portions where the same height continues. In the part where the height of the structure is high, the load is applied to the pile as much, so the number of piles can be increased or the length of the soil cement composite pile, especially the length of the soil cement column existing in the lower part of the winged steel pipe pile. It is preferable to make it longer. However, within the above length requirements.
[0025]
Of course, in the part where the height of the structure is low, the load applied to the pile is less than that in the high part, so the number of piles can be reduced or the length of the soil cement composite pile, especially in the lower part of the winged steel pipe pile It is preferable to shorten the length of the soil cement column. However, within the above length requirements.
[0026]
For example, as shown in FIG. 6, the soil cement synthetic pile described above has a sand layer in the lower portion of the winged steel pipe pile, and even when the supporting force is exhibited by the sand layer, When a soft viscous soil layer that tends to cause a consolidation settlement phenomenon exists under the sand layer, the effect of the present invention is exhibited by creating a soil cement column that reaches the soft viscous soil layer. Is applicable.
[0027]
In addition, although the creation method of the soil cement pillar in this invention is preferably created by a mechanical deep layer mixing treatment method, it can be created by a jet type or a substitution type deep layer treatment method.
[0028]
Furthermore, in the present invention, when the soil cement column body existing in the lower part of the winged steel pipe pile is created, the amount of solidified material to be added is increased, or the concentration of cement milk is increased to increase the strength of the soil cement column. May be.
[0029]
【Example】
[Example 1]
The winged steel pipe pile used in Example 1 and the comparative example is a steel pipe pile having spiral wings in the vicinity of the pile head, near the pile bottom and in the middle of the pile as shown in FIG. It is closed, the length is 6 meters, the outer diameter of the steel pipe pile body (i.e., the steel pipe part without the wing part) is 267.4 millimeters, and the outer diameter of the wing part is 500 millimeters.
[0030]
As shown in FIG. 8A, the soil cement column body is provided with a device capable of excavating the ground by rotating a rod 3 having at least a plurality of excavation blades 1 and agitation blades 2 at its tip by a drive unit 4. Using the soil cement construction machine 6, the ground 5 on which soft viscous soil is deposited is dug while discharging cement milk from the lower end of the rod 3, and the outer diameter is 700 mm as shown in FIG. A 12 meter deep soil cement column 7 was constructed for the example.
[0031]
The steel pipe pile 10 with wings 9 is embedded in the soil cement column 7. The figure (c) shows the figure in burial, and the figure after sunk is shown in the figure (d). The soil cement synthetic pile 11 thus created is created.
[0032]
In FIG. 9, the construction depth of the soil cement column body was made slightly longer than the length of the winged steel pipe pile in Comparative Example 1, and the construction depth of the soil cement column body was reached to the support layer. Is Comparative Example 2.
[0033]
FIG. 9 shows a pile that supports the structure by changing the length of the soil cement pillar in this way.
[0034]
Case 1 is a comparative example, Case 2 is Example 1, and Case 3 is Comparative Example 2.
[0035]
FIG. 10 shows the change over time of the amount of settlement of the structure in case 1, case 2, and case 3.
[0036]
The amount of settlement in case 1 is larger than in case 2 and case 3. The amount of settlement in case 2 was slightly larger than that in case 3, but was within the range of allowable settlement, and even in the end and center of the building, the settlement was even and did not cause uneven settlement.
[0037]
Further, the same soil cement column as in the above example was constructed, and a steel pipe pile having a length of 6 meters and an outer diameter of 267.4 mm without a wing portion was used, and a soil cement composite pile of Comparative Example 3 was constructed. .
[0038]
On the other hand, the winged steel pipe pile used in the example was directly twisted into the ground to obtain a pile of Comparative Example 4.
[0039]
Using the piles of these three conditions, a horizontal load was applied to the pile head, and the horizontal displacement of the pile head was measured.
[0040]
The result is shown in FIG. The horizontal displacement amount in the case of the present embodiment indicated by the rhombus marks is smaller than the horizontal displacement amount of the comparative example 4 indicated by the triangle marks and smaller than the horizontal displacement amount of the comparative example 3 indicated by the broken line, and has excellent horizontal The bearing capacity performance was demonstrated.
[0041]
[Example 2]
A soil cement composite pile having the same conditions as in Example 1 was constructed with the mutual distance between the soil cement pillars being 1 meter (about 1.5 times the diameter of the soil cement pillars).
[0042]
Soil cement composite piles were constructed under the same conditions as in Comparative Example 1 and Comparative Example 2 with the same spacing between the soil cement pillars, and these were used as comparative examples.
[0043]
Even in this condition, the superiority or inferiority of the reduction effect of the consolidation settlement amount was excellent in the case of Example 2 as in the superiority or inferiority difference between Example 1 and Comparative Example 1 or Comparative Example 2.
[0044]
[Example 3]
A soil cement composite pile having the same conditions as in Example 1 was constructed with the mutual distance between the soil cement pillars being 1.4 meters (about twice the diameter of the soil cement pillars).
[0045]
Soil cement composite piles were constructed under the same conditions as in Comparative Example 1 and Comparative Example 2 with the same spacing between the soil cement pillars, and these were used as comparative examples.
[0046]
Even in this condition, the superiority or inferiority of the reduction effect of the consolidation settlement amount was excellent in the case of Example 3 as in the superiority / inferiority difference between Example 1 and Comparative Example 1 or Comparative Example 2.
[0047]
[Example 4]
A soil cement composite pile having the same conditions as in Example 1 was constructed with the mutual distance between the soil cement pillars being 14 meters (about 20 times the diameter of the soil cement pillars).
[0048]
Soil cement composite piles were constructed under the same conditions as in Comparative Example 1 and Comparative Example 2 with the same spacing between the soil cement pillars, and these were used as comparative examples.
[0049]
Even in this condition, the superiority or inferiority of the reduction effect of the consolidation settlement amount was excellent in the case of Example 4 as in the superiority or inferiority difference between Example 1 and Comparative Example 1 or Comparative Example 2.
[0050]
[Example 5]
A soil cement composite pile having the same conditions as in Example 1 was constructed with a mutual interval between the soil cement pillars of 18.5 meters (about 25 times the diameter of the soil cement pillars).
[0051]
Soil cement composite piles were constructed under the same conditions as in Comparative Example 1 and Comparative Example 2 with the same spacing between the soil cement pillars, and these were used as comparative examples.
[0052]
Even in this condition, the superiority or inferiority of the reduction effect of the consolidation settlement amount was excellent in the case of Example 5 as in the superiority or inferiority difference between Example 1 and Comparative Example 1 or Comparative Example 2.
[0053]
[Example 6]
As a result of comparing the vertical supporting force per one of the soil cement composite piles of the conditions of Example 2, Example 3, Example 4 and Example 5, with the vertical supporting force of Example 1, Example 3 and Example 4 and Example 5 exhibited the same vertical support force as Example 1, but in the case of Example 2, a smaller value than that of Example 1 was shown.
[0054]
[Example 7]
The amount of settlement was calculated on the assumption that a building having the same shape was constructed on the soil cement composite pile group under the conditions of Example 2, Example 3, Example 4, and Example 5.
[0055]
As a result, the amount of subsidence increased little by little in the order of Example 2, Example 3, Example 4, and Example 5, but this was in the depth section of the soil cement column existing at the bottom of the winged steel pipe pile. There was a difference in the amount of settlement, and there was no difference in the amount of settlement in the soft viscous soil layer below the soil cement column.
[0056]
Moreover, the amount of subsidence of Example 2, Example 3, and Example 4 was in the range of allowable subsidence amount, and the amount of subsidence in Example 5 showed a value a little larger than allowable subsidence amount.
[0057]
【The invention's effect】
According to the creation method of the present invention, the amount of settlement of the soft and soft soil layer can be reduced despite the presence of the soft and viscous soil layer in the ground, and the amount of settlement of the structure falls within the allowable amount of settlement. Since there is no need to construct a long soil cement pillar that reaches the support layer unlike the conventional method, the amount of solidified material to be injected is reduced, and it is not necessary to dig deeply as in the conventional method. Construction can be done with a machine, construction time is shortened, and cost can be reduced.
[0058]
Moreover, it can be set as the soil cement synthetic | combination pile in which the horizontal resistance in the vicinity of a ground part is further superior to the conventional one.
[Brief description of the drawings]
FIG. 1 is a view showing a soil cement composite pile constructed according to the present invention together with a structure.
FIG. 2 is a diagram showing an example in which the length of a steel pipe portion is determined by a horizontal load, a moment acting on the steel pipe, and a shearing force.
FIG. 3 is a diagram showing an example in which the length of a steel pipe portion is determined by a vertical load and a supporting force.
FIG. 4 is a view showing a soil cement synthetic pile constructed according to the present invention together with a structure.
FIG. 5 is a view showing a soil cement synthetic pile constructed according to the present invention together with a structure.
FIG. 6 is a diagram showing a soil cement synthetic pile constructed according to the present invention together with a structure when a sand layer is present in the middle.
FIG. 7 is a view showing an example of a winged steel pipe pile used in the present invention.
FIG. 8 is a diagram showing a construction procedure of a soil cement synthetic pile according to the present invention.
FIG. 9 is a view showing a soil cement synthetic pile according to an embodiment of the present invention and a comparative example together with a structure.
FIG. 10 is a graph showing changes over time in the amount of settlement.
FIG. 11 is a graph of horizontal load and horizontal displacement.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Excavation part, 2 ... Stirring blade, 3 ... Excavation rod, 4 ... Drive part, 5 ... Ground, 6 ... Soil cement pillar production apparatus, 7 ... Soil cement pillar body, 9 ... Wing part, 10 ... Steel pipe with wing | blade Pile, 11 ... Soil cement composite pile

Claims (2)

A reclamation method of soil cement synthetic pile inserting a winged steel pipe pile wings around at least the head and around Kuisoko portion is present in the soil cement pillar that is reclamation in Ground soft cohesive soil layer is present, wings The hollow part of the steel pipe pile has a hollow state so that the air in the hollow part acts as buoyancy, and the length of the soil cement column existing in the lower part of the winged steel pipe pile is 0.5 to the length of the steel pipe pile. A method for constructing a soil cement synthetic pile characterized in that it is three times longer and the bottom of the soil cement pillar does not reach the supporting ground. A method for constructing a soil cement synthetic pile used in a design in which a structure is supported by a large number of soil cement synthetic piles in a ground where a soft viscous soil layer exists, and at least a head as a steel pipe pile in the soil cement synthetic pile Using a winged steel pipe pile with wings in the vicinity and the bottom of the pile, the bottom of many soil cement pillars does not reach the support ground , and the surface connecting the tips of the many soil cement pillars Convex shape that protrudes downward, the hollow part of each winged steel pipe pile is hollow so that the air in the hollow part acts as buoyancy, the length of the soil cement column existing at the bottom of each winged steel pipe pile Soil cement composite piles so that the length of steel pipe piles is 0.5 to 3 times the length of the steel pipe piles and the distance between the soil cement pillars is 2 to 20 times the diameter of the soil cement pillars Construction Construction method of soil cement synthetic pile, characterized by.

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