KR20180077364A - Construction method of mall-scale precast piles considering cement milk influenence - Google Patents

Abstract

The present invention relates to a method to construct a reduced model of a buried pile in consideration of effect of cement paste, capable of recommending an excavation diameter and a cement paste/cement ratio suitable for a real buried pile. According to the present invention, the method comprises: a step (a) of preparing construction of a reduced model of a buried pile; a step (b) of drilling a hole on a construction position; a step (c) of mixing cement paste and primarily injecting the mixed cement paste into a drilled position; a step (d) of inserting a test pile into the drilled position; a step (e) of secondarily injecting the cement paste into the drilled position around the inserted test pile and reinjecting the cement paste after checking a water loss; and a step (f) of performing a load test after curing the cement paste.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a method of constructing a concrete pile,

The present invention relates to a method of constructing a pile, more particularly, to a reliable test construction method that reflects a method of actual construction by a reduced scale model of pile behavior analysis considering the influence of cement pool.

In recent years, the application of the pile method to the pile has been rapidly increasing as the bridge foundation of the general highway including the highway due to the problems of construction noise and vibration regulation. Especially, as the construction of highway bridges in recent years has been concentrated in mountainous areas, the use of pile foundation has been increasing, and steel pipe piles having excellent horizontal stiffness and easy connection of pile head and pile sound have been preferred.

The difference between the piles and other piles is that they are injected into the tip and main surface by using cement paste to stabilize the excavation wall and to induce the vertical and horizontal stiffness of the pile. At this time, the landing force is affected by the strength of the cement paste.

In the existing pile study, the bearing behavior analysis and the engineering study on the cement paste were carried out. The results of this study are summarized as follows: (1) The strength of the cement paste was higher than that of the cement paste, but the compressive strength of the cement paste was higher than that of the cement paste. In this study, the pore-perforation technique and the grouting technique play an important role in bearing capacity (Neely et al. 1999). In the case of Hongwon Pyo et al. (2008), it was confirmed that the unit main surface frictional force increases with increasing the cement paste water / cement ratio.

The excavation pile of the pile has various criteria for each institution, but it is a reality that is unified and scattered. Currently, it is stated that it is 5 ~ 10cm or more than 10cm than the pile diameter such as Korea Highway Corporation and LH Corporation. At this time, the study on the thickness of cement paste injected between excavation pores has been studied intensively, and the criteria for excavation pore size is not clear.

In other words, the influence on the existing buried pile cement pool is limited by the economical and temporal difficulties in the actual model size test, and in particular, the cement pool itself was tested through the indoor test, The test is trivial.

As described above, recently, the application of the piling method to the pile is more increased than the pile for the bridge of the general highway including the highway due to the problems such as construction noise and progress control. Currently, there is no precise standard for excavation pore size and cement paste mixing ratio when constructing a pile, which is causing confusion.

Korean Registered Patent No. 10-0869815 (Registered Date: November 14, 2008) Korean Registered Patent No. 10-1039554 (Registered Date: June 01, 2011)

The method of constructing a pile-down model considering the influence of the cement pool according to the present invention has the following problems.

First, the present invention aims to provide a method of selecting the mixing ratio of the cement pool optimized for the pile diameter and the excavation attack through the miniature model test.

Second, the present invention confirms the effect of the cement pool water / cement ratio and excavation pore size through the miniature model test, and the construction of the pile shrinkage model which can propose proper excavation pore and cement pool water / cement ratio for the real model pile And the like.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus and method for controlling the same.

According to a first aspect of the present invention, there is provided a pit construction method comprising: (a) a construction preparing step for constructing a reduced-scale embedding pile; (b) performing drilling at a construction site; (c) blending the cement paste and first injecting the combined simeta pulp into the perforated position; (d) penetrating the test pile into the pierced hole where the cement paste is injected; (e) secondly injecting the cement paste into the perforated position around the intruded test pile, and re-injecting the cement paste after confirming the watering phenomenon; And (f) performing a load test after curing the cement paste.

In the step (e), the step of re-injecting the cement paste may include: (e1) first checking the phenomenon of cement paste days after completion of the application; (e2) checking a second time after a predetermined time elapses; And (e3) injecting the main surface fixing liquid to the surface of the ground after the water development check.

The method for constructing a pile-backed pile model considering the effect of the cement paste according to the present invention has the following effects.

First, the present invention can be economically and efficiently carried out in the construction of a pile taking into account the cement pool mixing ratio, excavation pore size, and the like which were not considered in the conventional laboratory test through the miniature model test.

Second, to confirm the behavior of the pile on the basis of frictional force, the effect of cement pool water / cement ratio and excavation pore size was verified by field scale shrinkage model test and the appropriate excavation pore and cement pool water / cement ratio And to provide a method of constructing a miniature pile of a pile which can propose a pile reduction model.

Third, it provides a construction method of the reduced pile shrinkage model that can prevent the unfavorable bearing capacity after completion of construction.

The effects of the present invention are not limited to those mentioned above, and other solutions not mentioned can be clearly understood by those skilled in the art from the following description.

FIG. 1 is a view showing a flow of a method of constructing a pile-down type model considering the influence of cement pool according to an embodiment of the present invention.
FIG. 2 is a graph comparing the results of unconfined compressive strength of cement paste between Korea Highway Corporation and LH Corporation.
Figure 3 shows the soil profile for the test files.
4 is a schematic of a site test, showing a site plan having a site test location.
5 is a schematic diagram of a reduced scale model file test.
6 is a view comparing excavation pore diameters of the model pile and the thread model.
FIG. 7 is a photograph showing a construction procedure of applying a method of constructing a buried pile shrinkage model considering the influence of cement paste according to an embodiment of the present invention.
Figure 8 shows the results for each excavation pore when the cement pool water / cement ratio is the same.
Figure 9 shows the results according to the variation of the cement paste water / cement ratio.
Fig. 10 is a photograph showing the destruction form around the reduced model file.
Fig. 11 shows the result of confirming the yield load according to the change of the pore size and the change of the cement paste water / cement ratio by the PS method.
12 is a graph showing a yield load result of cement paste water / cement ratio.

Further objects, features and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Before describing the present invention in detail, it is to be understood that the present invention is capable of various modifications and various embodiments, and the examples described below and illustrated in the drawings are intended to limit the invention to specific embodiments It is to be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Further, terms such as " part, "" unit," " module, "and the like described in the specification may mean a unit for processing at least one function or operation.

In the following description of the present invention with reference to the accompanying drawings, the same components are denoted by the same reference numerals regardless of the reference numerals, and redundant explanations thereof will be omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing a flow of a method for constructing a buried pile shrinkage model considering the influence of a cement paste according to an embodiment of the present invention. FIG. 7 is a cross- This is a photograph showing the construction sequence to which the method is applied.

As shown in FIG. 1, a method for constructing a buried pile shrinkage model considering the influence of cement paste according to an embodiment of the present invention includes: (a) a construction preparation step for constructing a shrinkage model buried pile; (b) performing drilling at a construction site; (c) blending the cement paste and first injecting the combined simeta pulp into the perforated position; (d) penetrating the test pile into the pierced hole where the cement paste is injected; (e) secondly injecting the cement paste into the perforated position around the intruded test pile, and re-injecting the cement paste after confirming the watering phenomenon; And (f) performing a load test after curing the cement paste.

In this way, the method of construction of the pile shrinkage model considering the influence of the cement paste according to the embodiment of the present invention proposes a method of shrinkage model construction to reflect the field conditions on the influence of the cement paste upon the pile construction.

Hereinafter, with reference to FIG. 1 and FIG. 7, a method for constructing an embedded pile shrinkage model considering the influence of a cement pool according to an embodiment of the present invention will be described in detail with reference to FIGS.

① Step 1) Preparation

A) The construction location is selected by referring to the ground survey data.

B) Determine cement and water content for cement paste formulation.

C) Prepare equipment for test piles and drilling.

(When selecting test piles, be careful to select equipment so that there is no problem with verticality.)

② Step 2) Perforation

A) Using a perforator machine, pay attention to the verticality and drill.

B) When drilling, consider treatment for excavated soil.

C) Check whether or not the ridgeline of the tip is present.

D) Confirm the retention of the anticontact wall when drilling, and re-puncture using the casing when the wall breaks down.

(When using a boring machine, do not flush.)

③ Step 3) Cement pool  combination

A) The water used in the formulation is fresh water.

B) Determine the target compounding ratio and select the amount of water and cement. (The amount of water is measured using a measuring cylinder, and the amount of cement is measured using a scale.)

C) Allow the cement paste to harden for a sufficient time.

④ Step 4) First Cement pool  Injection

A) After puncture, inject 4D of the root muscle mass.

B) Injection with a funnel to prevent loss of cement paste during injection.

⑤ Step 5) Test pile penetration

A) The test pile shall be penetrated by observing the verticality.

B) Slowly infiltrate to the tip using a device to prevent ingrowth.

C) After the penetration of the test pile, use a horizontal ruler to finally check the verticality.

⑥ Step 6) Secondary Cement pool  Injection

A) After the test pile penetration, the main surface fixing solution is injected.

B) Fill the fixation solution to the surface of the ground sufficiently and pay attention to overflow.

⑦ Step 7) Days Phenomenon  after confirmation Cement pool  Reinjection

A) Check the cement pool days after the completion of construction (primary)

B) Perform re-check after 24 hours of construction (2nd phase)

(C) After the check of the day's phenomenon, inject the surface fixation fluid sufficiently to the surface of the earth.

⑧ Step 8) Curing and Loading test

A) Load test after 28 days of curing.

B) Load method should be selected based on the reduced model size.

C) Rapid load test is carried out with attention to displacement convergence by load step.

D) After completion of the loading test, confirm the failure behavior through excavation.

A pile bearing surface Cement pool  effect

Generally, pile-up pile method is performed by piercing the ground 100 mm larger than the diameter of the pile and injecting cement paste. At this time, the injected cement pool helps to stabilize the excavation wall and serves as a medium to transfer the load applied to the pile to the surrounding ground. The friction bearing capacity of the embedded pile is known to be proportional to the strength of the ground and the strength of the cement paste.

In addition, a study on the end bearing capacity and surface friction of a similar cement-filled pile has been conducted rather than a direct study of the pile, Neely et al. (1991) Lee and Poulos (1990) investigated the characteristics of the ground friction force based on the load transfer phenomena of the cement-filled piles, and found that the decrease in frictional force was related to the diameter of the pile. .

In 2015, the uniaxial compressive strength of the cement paste was 20 MPa or more, and the theoretical cement paste / cement ratio was 100%. At this time, 70% of the cement paste water / cement ratio was considered appropriate. FIG. 2 is a graph comparing the results of unconfined compressive strength of cement paste between Korea Highway Corporation and LH Corporation.

Park, Jongbae (2004) analyzed the results of the dynamic test according to the strength of cement paste. At this time, when the E.O.I.D. results before curing and the restrike result after curing were compared and analyzed, it was reported that the friction supporting force is proportional to the strength of cement paste. And, it is confirmed that the horizontal yield load and the bearing capacity of the pile are about 2 ~ 3 times larger than that of 0.5 when the cement pool injection ratio is 1.0.

The strength of the cement paste, which is the main factor of the friction force of the pile, is mainly determined by the water / cement ratio, but there is no clear standard in Korea. After the pre-drilling, the final root-to-edge method uses 70% of the near-surface liquid / cement ratio and 120% of the main-surface fixer, or the tip / main fixer is mixed at the water / cement ratio of 83%.

Field scale model test

end. Selection of field scale model test

In the field scale model test using the method of construction of the pile load model considering the influence of the cement pool according to the embodiment of the present invention, the influence of the pile on the tip of the test pile is excluded and the behavior between the pile pile- It is designed to overcome the economic burden and construction difficulties that occur when testing the effect of excavation pore and water / cement ratio using actual piles.

In this paper, we propose a pile-type pile-type pile-type pile, which is used as a pile-type pile-type pile. And placed in the form of a friction pile.

Based on the results, we investigated the effects of osseointegration and water / cement ratio on the frictional force and investigated the fracture surface between cement paste and ground. The load test for the reduction test pile was based on the static load test (rapid load test) and was performed by using the dead load.

The test load was divided into 8 steps or more, and the load was maintained until the settlement rate per load step was less than 0.25 mm per hour. The loading time for each load step was 20 minutes, and then the load was maintained for 5 minutes while maintaining the load, and the load was continuously loaded to confirm the destruction of the pile.

The results are analyzed basically by the ultimate bearing capacity of the load - settlement curves and analyzed by excavation pore and water / cement ratio. In this case, when the result of the ultimate bearing capacity is difficult to analyze, the results are compared with each other to confirm the behavior.

I. Ground condition

The field scale model test was conducted in Chungcheongnam-do 00 area, and the ground consists of buried layer, sediment layer and weathering layer from the surface as shown in Fig. Figure 3 shows the soil profile for the test files.

In order to estimate the physical properties of the landfill, the field test and the room test for the disturbed specimens were carried out. The soil properties were estimated through comparison with existing ground survey report and various literature data. The summary properties are shown in [Table 1]. The ground depth at which the test was carried out is composed of silty sand as N 2/30 layer (buried layer).

4 is a schematic of a site test, showing a site plan having a site test location.

All. Loading equipment  And test piles

All the tests of the embodiment of the present invention were performed to check the influence of the supporting force of the main surface portion and the interface behavior according to the conditions of the cement paste in the construction process of the pile, so that the construction was not performed to the deep depth. Excavation was carried out using a drill used for the soil investigation.

We measured the pile displacement by load gauge by installing a dial gauge on top of the pile cap. In addition, a 10ton hydraulic jack was used to allow sufficient load and displacement to occur at the top of the pile cap, and the sectional view after completion of installation of the load test apparatus is shown in FIG. 5 is a schematic diagram of a reduced scale model file test.

In the case of the test pile used, a steel pipe rod type was used and it was determined that the diameter was 67 mm and the length was 1.3 m in consideration of a 50 m diameter 50 m long and 20 m long steel pipe pile which is currently used in the field (refer to FIG. 3) In the test, the same piles were used for all the test cases because the purpose of the analysis was to analyze the behavior of the pile according to the conditions of the surrounding cement pool, not the effect of the diameter of the pile.

la. Pile installation and Loading test

For the water / cement ratio of this study, 15 drill holes were constructed with drilling diameters of 150, 125, 90, 86, and 74mm for 60, 70 and 90%, respectively. The detailed test cases are summarized in [Table 2], and Fig. 6 is a diagram comparing excavation pore sizes of the model pile and the thread model.

Test results and analysis

end. On excavation  Ultimate bearing capacity

The excavation pore diameter was compared between 125mm (1.86D) and 90mm (1.34D). Fig. 8 shows the results of excavation pore diameter when the cement paste water / cement ratio is the same. 8 (a), when the cement paste water / cement ratio was 90%, the ultimate load range was 30 kN when the pore diameter was 125 mm (1.86 D) or more, and the settlement of about 77 to 92 mm occurred. In case of 90mm (1.34D) or less, the ultimate load range is 15 ~ 21kN and settlement of 80 ~ 86mm occurs.

8 (b) shows that the ultimate load range is 35 kN when the cement pool water / cement ratio is 70%, the settlement amount is 85-92 mm, and 90 mm (1.34 D) or less 13 to 18 kN, and the settling amount was 71 to 91 mm.

8 (c) shows that the ultimate load range is 35 kN when the pore diameter is more than 125 mm (1.86 D) and 78 to 87 mm when the pore water / cement ratio is 60% 21 kN, and settlement of 92 mm or more was confirmed. As a result, the bearing capacity tended to increase with increasing excavation pore size.

I. Cement pool  Ultimate bearing capacity due to water / cement ratio

The results of the change in cement paste water / cement ratio are shown in FIG. The load - settlement curves were different between 125mm (1.86D) and 90mm (1.34D). Fig. 10 is a photograph showing the destruction form around the reduced model file.

9 (a) shows the excavation pore size of 150 mm (2.2 D). When the water / cement ratio was 70% at the ultimate load, it was 30 kN at 35 kN, 90% and 60% , And thus the bearing capacity was the largest at 70%. At this time, when the cement pool water / cement ratio was 60%, the bearing capacity was the smallest, which generally caused fracture between the cement pool and the ground (see FIG. 10 (b)). However, (Fig. 10 (a)) is generated and it is judged that it has affected the supporting force.

Figure 10 shows fracture morphology with an excavation pore diameter of 1.86D or greater and fracture shape below 1.34D. FIG. 9 (b) shows that when the pore diameter was 125 mm (1.86 D), the settlement was small as the water / cement ratio was reduced, and the settlement amount was 78 and 92 mm, and the ultimate bearing capacity was 35 kN and 30 kN, respectively.

9 (c) to 9 (e) show that the excavation pore size is 90 mm (1.34 D) or less, and the ultimate bearing capacity is increased as the cement paste / cement ratio is increased. The ultimate bearing capacity range is 13 to 21 kN. ~ 95mm. As a result of analysis, the bearing capacity tends to increase with the dissymmetry at 90mm (1.34D) or less, but the bearing capacity decreases at 125mm (1.86D) or more.

All. Yield Rating

Fig. 11 shows the yield load according to the change of the pore diameter and the change of the cement paste water / cement ratio by the P-S method. In the analysis of the behavior through the ultimate bearing capacity, the results of the cement paste water / cement ratio were not clear, so the analysis by the yield load was carried out.

As a result of the analysis, FIG. 11 (a) to (c) shows that the yield load increases as the pore diameter increases with the yield load according to the pore size. As a result, it was found that the yield load and the ultimate bearing capacity increase as the excavation pore size increases.

12 (a) to (e) are graphs showing yield load results of cement paste water / cement ratio. In this case, it was found that the yield stress is larger when the water / cement ratio is worse than 1.86D, which is different from the result of ultimate bearing capacity. The reason for this is that when the internal fracture occurs in the cement pool due to the increase of excavation pore, the shear force is higher than the fracture state between the cement pool and the ground and the bearing capacity is relatively large. At this time, it is considered that the influence of internal fracture in the cement pool and especially the quality control of the pile and the ground condition are also considered.

conclusion

In the embodiment of the present invention, a scaled model test was performed to examine the behavior analysis according to the influence of the cement paste, which is a fixative of the main surface of the pile, in consideration of the overhead cost. As a result of the test using the embodiment of the present invention, the following conclusions were obtained.

1. Comparison of the effects on excavation pore shows that the excavation pore size is less than 1.34D (actual pore diameter 550 ~ 700mm) and 1.86D (actual pore diameter 950 ~ 1,137mm). In case of general excavation pile, bearing capacity increased as excavation pore increased.

2. The effect of cement paste on water / cement ratio was investigated. As a result of the cement pool strength test of the existing study, the increase in the strength was found to be the increase in the strength, resulting in an increase in the bearing capacity of the pile.

3. As a result of the reduced scale test, when the excavation pore was the same, the cement pool water / cement ratio showed the largest bearing capacity at 60%. However, in case of 60%, proper water / cement ratio is considered as 70% when considering the quality control such as the situation where there is no smooth casting (poor workability) and the daytime phenomenon in the field.

4. Embodiments of the present invention performed a miniature model test for pore sizes less than 1.34 D (actual pore size 550 to 700 mm) and pore sizes greater than 1.86 D (actual pore size 950 to 1,137 mm). Test results showed that the closer to the dissimilarity and the larger the pore diameter, the greater the bearing capacity. This is due to the fact that the shear behavior for friction force generation occurs in the general case (excavation pore diameter less than 1.34D) between the cement pool and ground, but when the pore diameter is increased to 1.84D or more, the failure mode is changed by internal fracture in the cement pool Could know. Therefore, the excavation pore size is considered to be less than the general behavior of 1.34D.

The embodiments and the accompanying drawings described in the present specification are merely illustrative of some of the technical ideas included in the present invention. Accordingly, the embodiments disclosed herein are for the purpose of describing rather than limiting the technical spirit of the present invention, and it is apparent that the scope of the technical idea of the present invention is not limited by these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (2)

(a) Construction preparation stage for the construction of a miniature model pile;
(b) performing drilling at a construction site;
(c) blending the cement paste and first injecting the combined simeta pulp into the perforated position;
(d) penetrating the test pile into the pierced hole where the cement paste is injected;
(e) secondly injecting the cement paste into the perforated position around the intruded test pile, and re-injecting the cement paste after confirming the watering phenomenon; And
(f) curing the cement paste and then carrying out a load test. The method according to claim 1,
The step of re-injecting the cement paste in the step (e)
(e1) firstly checking the phenomenon of cement pool days after completion of the construction;
(e2) checking a second time after a predetermined time elapses; And
(e3) injecting the main surface fixing liquid to the ground surface after the check of the water development, and taking into account the effect of the cement pool.

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