JP5969350B2 - Vertical loading test method of existing pile and construction method of concrete reaction body - Google Patents

Description

  The present invention relates to a vertical loading test method of an existing pile for confirming whether or not the existing pile used in the existing building has a supporting performance that can withstand reuse, and the concrete used for this test. It is related with the construction method of the reaction force body.

  When rebuilding a building, the existing pile used in the existing building is reused as a pile in a new building to shorten the construction period and cost. Prior to its reuse, in order to test the support performance of an existing pile, the head of the existing pile to be tested in an existing building was cut at a predetermined height to cut the foundation slab and the edge, A jack is installed between the foundation piles and a loading force is obtained by obtaining a reaction force on the foundation slab (Patent Document 1).

JP-A-11-264247 Japanese Patent No. 4378241 JP-A-8-312140 JP 58-156627 A

According to the method of Patent Document 1, there are the following disadvantages.
First, since a loading test is performed by obtaining a reaction force on the foundation slab of an existing building, a large test load cannot be applied to the test pile.
Secondly, since the ground below the foundation slab is excavated in order to secure a space for installing the jack between the existing pile and the foundation slab, it is necessary to construct a retaining wall around the work space.
Thirdly, it is difficult for the underground work space to carry in equipment such as jacks used for carrying out excavated soil generated during excavation and loading tests, and the workability is poor.

  Therefore, the present applicant has proposed a test method for obtaining a reaction force from a building instead of a basic slab. This method cuts the edge between the existing pile to be tested and the foundation frame, and then constructs a concrete reaction body that can obtain the reaction force of the test load from the existing building above the existing building. The jack installed above is connected to the concrete reaction force body, and a test load is applied to the existing pile by the jack (Patent Document 2), whereby a large test load can be applied to the existing pile.

  In order to obtain a large reaction force, the concrete reaction force body needs to be connected over a wide range of an existing building. For this purpose, the volume needs to be increased to some extent. However, when placing a concrete structure with a large volume, the heat of hydration of the cement is accumulated inside during the curing period, and if the temperature distribution of the concrete structure due to the heat generation is uneven, temperature cracks may occur. Is known, and this does not give a large reaction force.

  As a technique for suppressing the above-described temperature crack, Patent Document 3 discloses that concrete that is poured into the center of mass concrete (referred to as massive concrete) has a slower heating rate than concrete that is cast into the periphery. Propose that. Moreover, patent document 4 discloses forming the lowermost layer part of the wall-shaped mass concrete installed on a foundation with the concrete which mixed the solidification retarder, and forming the remaining part with normal concrete.

  However, when constructing a concrete reaction body that is used for the test load test of existing piles and is scheduled to be demolished after the test, it is more rapid and less expensive than a normal building frame. What has intensity | strength is calculated | required.

The first object of the present invention is a vertical loading test method for testing the support performance of an existing pile of an existing building, and a concrete reaction body for obtaining a reaction force from the existing building exhibits a sufficient reaction force. It is to propose what can be done.
A second object of the present invention is a vertical loading in which the concrete reaction force body is divided into a plurality of layers in the vertical direction and the concrete placed in each layer is set to exhibit a predetermined strength on the same day. It is to propose a test method.
The third object of the present invention is to propose a method for constructing a concrete reaction body suitable for the vertical loading test method.

The first means is
A vertical loading test method for reusing existing piles used in an existing building when rebuilding a building,
Cutting the edge between the existing pile to be tested and the foundation frame of the existing building,
Above the existing pile, a concrete reaction body construction step for constructing a concrete reaction body having a predetermined strength with a configuration capable of obtaining a reaction force of a test load from an existing building;
A jack is installed at the upper end of the existing pile, the jack and the concrete reaction body are connected, and a test load is applied to the existing pile by the jack to measure the support performance, and the measurement step comprises:
The concrete reaction body construction step is as follows:
The concrete reaction force casting area is divided into at least two horizontal partial layer areas in the vertical direction, and each partial layer area is required to achieve a predetermined strength through a curing period from the placement date. A first sub-step for determining the management age, which is the number of days;
Set a target date that should achieve a predetermined strength common to all partial layer areas, and determine the placement date of each partial layer area by calculating backward from the target date according to the management age of each partial layer area A second sub-step;
In order from the lower partial layer area, the third sub-step is repeated to repeat placing concrete on the casting date determined for each partial layer area,
The predetermined strength of all the partial layer regions is achieved on the same target date.

In this means, as shown in FIGS. 2 to 3, the concrete reaction force body 7 is divided into a plurality of layers L ₁ ... And separately placed from the lower layer to the upper layer, and the management age is determined for each layer. The casting date is set so that the concrete cast in each layer reaches a predetermined strength on the same day from the management age of each layer (FIG. 4). In general, if the “water cement ratio [W / C] or water binder ratio [W / B] is small, the strength of the concrete increases, and if there are many pozzolanic materials such as fly ash with a slow reaction rate, the strength will increase in the long term. In addition, because “the smaller the unit cement amount, the lower the amount of hydration, the less hydration heat is generated”. By setting the placement date for each layer as described above, the amount of cement is reduced and the construction period is shortened. -It can contribute to the reduction of cracks caused by heat of hydration. This will be described later. Here, C is the amount of cement, B is the amount of binder [B = C + F] obtained by adding fly ash [F], which is cement and pozzolanic material, and W is the amount of water.

The second means is
It is a construction method of a concrete reaction body added to the frame of an existing building in order to perform the vertical loading test method of the existing pile described in the first means,
The concrete reaction force casting area is divided into at least two horizontal partial layer areas in the vertical direction, and each partial layer area is required to achieve a predetermined strength through a curing period from the placement date. A first stage for determining the management age, which is the number of days,
Set a target date that should achieve a predetermined strength common to all partial layer areas, and determine the placement date of each partial layer area by calculating backward from the target date according to the management age of each partial layer area The second stage,
In order from the lower partial layer area, it consists of a third stage that repeats the placement of concrete on the casting date determined for each partial layer area,
The concrete reaction force body is constructed by being connected to at least the lowest column beam structure facing the existing pile in the building frame composed of the column beam frame. A jack insertion gap is formed between the lower end surface and the existing pile.

  This means shows a construction method of the concrete reaction body 7 suitable for the test method which is the first means. The concrete reaction body 7 is connected to at least the lowest column beam structure of the existing building (FIGS. 2 to 3).

The third means has the second means,
The concrete reaction body is composed of at least one concrete reaction wall that connects the columns of one column beam structure and is integrated with the beam. Divided into partial layer regions, formed by sequentially placing each partial layer region,
The management age of concrete in each partial layer region was shortened from the lower side to the upper side.

  In this means, the concrete reaction body is used as a reaction wall. The management age of the concrete in each partial layer region of the reaction wall becomes shorter from the lower side to the upper side.

The fourth means is
The concrete reaction force body was formed by the two concrete reaction force walls described in the third means intersecting each other and uniting above the existing pile.

  In this means, the concrete reaction force body 7 is formed by combining the two concrete reaction force walls 7A and 7B so as to intersect (see FIG. 1). As a result, the connection between the concrete reaction body and the existing building becomes strong, and a sufficient reaction force can be obtained.

The fifth means includes the fourth means, and the placement area of the concrete reaction force body is large at a location where the wall thickness of both concrete reaction force walls is close to the existing pile, and is reduced at a location far from the existing pile. Was set as follows.

  In this means, as shown in FIG. 1, the wall thickness of the two concrete reaction wall 7A, 7B is made large at a location close to the existing pile. That is, during the vertical loading test, a reaction force from the existing pile is generated, and the reaction force on the walls of the concrete reaction wall 7A, 7B acts more as the bending stress is closer to the existing pile. For this reason, even if the wall thickness at the wall ends of the concrete reaction walls 7A and 7B is reduced and the amount of concrete used is reduced, the wall thickness is increased and the structural mechanically rational arrangement is closer to the existing piles. By doing so, the required strength of the concrete reaction wall can be secured.

According to the invention relating to the first means and the second means, the concrete reaction force bodies are placed in a plurality of regions, and the day when the strength of the concrete placed in each region reaches a predetermined value is the same. Therefore, the amount of cement used can be reduced, or the placing work can be performed quickly. In addition, it becomes possible to divert formwork and the like in formwork support work, and a formwork diversion plan can be made without waste.
According to the invention relating to the third means, since the concrete management age of the concrete in each partial layer region is shortened from the lower side to the upper side, the amount of cement can be reduced toward the lower side.
According to the invention relating to the fourth means, the concrete reaction force body is formed by combining the two concrete reaction force walls so that they cross each other above the existing pile, so that they are mutually outside the wall surface itself. The buckling is prevented and sufficient reaction force is obtained.
According to the fifth aspect of the invention, since the wall thickness of the concrete reaction wall is large at a location close to the existing pile and decreases at a location far from the existing pile, sufficient bending strength can be obtained.

It is a plane sectional view of the concrete reaction body applied to the existing building concerning a 1st embodiment of the present invention. It is II-II direction sectional drawing of the concrete reaction force body of FIG. It is a III-III direction sectional view of the concrete reaction body of Drawing 1. It is action | operation explanatory drawing of the concrete reaction force body of FIG. It is a figure which shows the relationship between the strength of the concrete of each layer at the time of curing of the concrete reaction body of FIG. 1, and the elapsed time from the placement date. It is a figure which shows the relationship between the intensity | strength of concrete and the elapsed time from a placement date in the comparative example with the concrete reaction body of FIG. It is a graph showing the relationship between the binder water ratio and the compressive strength in the pile loading test for every elapsed days from the placement date. It is a graph showing the relationship between the age in the load test of a pile, and compressive strength for every binder water ratio. FIG. 9 is a graph for deriving the age for achieving a certain compressive strength based on the result of FIG. 8.

  1 to 6 show a concrete reaction body 7 according to a first embodiment of the present invention together with an existing building 1. For convenience of explanation, these structures will be explained first.

  First, the existing building 1 includes a plurality of existing piles 2, a foundation frame 6, a plurality of pillars 4, and a plurality of beams 5a and 5b. The existing pile 2 is driven into the ground except for the upper end portion, and the foundation frame 6 is laid so as to be connected to the upper end portion of the existing pile 2. The pillars 4 are erected upward from the foundation housing 6 and are arranged in a lattice pattern at regular intervals in the X and Y directions, as shown in FIG. The beam 5a extends between the columns 4 so that the beam 5a extends in the X direction and the beam 5b extends in the Y direction. In the present specification, a structure formed by the columns 4 and the beams 5a is referred to as a column beam frame 3a, and a structure formed by the columns 4 and the beams 5b is referred to as a column beam frame 3b. Then, one test pile 2a for the vertical loading test is selected from the plurality of existing piles 2.

The column 4 located right above the test pile 2a is cut out of a column base for a vertical load test to form a leg-cut column 4a. This is because a gap G for jack insertion is provided between the column and the test pile 2a. As a preferred embodiment, it is preferable that a concrete reinforcement is added around the existing pillars to form a large-diameter reinforcing pillar before placing a concrete reaction body 7 described later. Dotted lines N ₁ , N ₂ , N ₃ ,... In the figure represent the contour lines of these reinforcing columns. These reinforcing columns are preferably substantially encased in the concrete reaction body 7. Further, the above-described leg cutting column 4a is connected to the reaction force wall and the existing beam in order to prevent the leg dropping column 4a from descending.

  The concrete reaction force body 7 is connected to the existing building 1 and has a certain length in the vertical direction like a reaction force wall or a reaction force column. Otherwise, it is not necessary to divide the placement area in the vertical direction and perform overstrike. The concrete reaction body 7 can be made of reinforced concrete.

  In the illustrated example, the concrete reaction body 7 has a concrete wall 7A extending in the X direction through the top of the test pile 2a and a concrete reaction wall 7B extending in the Y direction through the top of the test pile 2a. These two walls intersect and merge above the test pile 2a. This is to increase the bonding strength of the concrete reaction body 7 to the existing building 1. However, if either one of the concrete walls 7A extending in the X direction or the concrete reaction wall 7B extending in the Y direction already has sufficient strength, it will be used only in the direction without strength. A concrete reaction body 7 may be constructed.

  As shown in FIG. 1, the concrete reaction wall 7A, 7B of the present embodiment extends over a plurality of (four in the illustrated example) inter-column regions. The concrete reaction walls 7A, 7B are integrated with the column beam frames 3a, 3b by including the columns 4 ... and beams 5a, 5b within the concrete reaction wall formation range. With such a configuration, a large reaction force can be obtained.

  Of these concrete reaction walls 7A and 7B, in the vicinity of the cut-out portion of the leg-cutting column 4a, a void 10 is formed by omitting the placement of the concrete portion in contact with the foundation frame 6 in a cross shape when viewed from the vertical direction doing. This is because a jack is inserted between the test pile 2a and the concrete reaction body 7. In the illustrated example, the placement of concrete in contact with the foundation frame 6 is omitted in the area between the columns centered on the leg-cut columns 4a.

  In the example shown in the figure, the upper surface of the space 10 part away from the test pile 2a is made higher than the lower end surface of the leg cutting column 4a, but the concrete covers the leg cutting column 4a near the leg cutting column 4a. Provide. This covering portion is formed as a contact portion 12 with the jack so that the lower surface is a flat horizontal surface and faces the test pile 2a.

  In the illustrated example, the wall thickness is increased near the intersection of the two concrete reaction walls 7A and 7B, and the wall thickness is decreased far from the intersection.

The concrete reaction force body 7 is composed of a plurality of partial layers L ₁ , L ₂ ... In the figure, S is the joint surface of each partial layer.

Next, the matter which overlaps with patent document 2 among the procedures of the vertical loading test method of the existing pile is demonstrated.
First, the test pile 2a is selected from a plurality of existing piles 2 of the existing building 1.
Second, cut the edge E between the test pile 2 and the foundation frame 6 by cutting the foundation frame part 6a above the test pile 2a from above with the same shape as the plane shape of the test pile 2a by means such as core boring. At the same time, the test pile 2a is connected to the foundation frame portion 6a above the test pile.
Third, the concrete reaction body 7 is constructed so that a reaction force can be obtained in the plane of the frame of the column beam frame 2 of the existing building 1. The concrete reaction body 7 can be formed simply by placing the reinforcing bars in the frames 3a and 3b, assembling the formwork, and placing concrete using the structure of the existing building.
Fourth, a jack J is installed on the foundation frame portion 6a above the test pile 2a, and the upper end portion of the jack J and the lower end portion (contact portion 12) of the concrete reaction force body 7 are connected.
Fifth, the loading load of the test pile 2a is measured using this jack J.

  Next, a method for constructing the concrete reaction body 7, which is specific to the present application, will be described.

[First stage]
In the first stage, the placement area of the concrete reaction body 7 is divided into at least two horizontal partial layer areas L ₁ , L ₂ ... In the vertical direction, and cured from the placement date for each partial layer area. The management age, which is the number of days required to achieve a predetermined strength over a period, is determined.

The management material age of each partial layer region L ₁ , L ₂ ... Is determined from the water cement ratio or the water binder ratio used in each partial layer region according to the target value of concrete strength. When the management material age is set short, there are many factors that accelerate the concrete strength development, and when the management material age is long, there are many factors that delay the concrete strength development. Conventionally known techniques can be appropriately used for adjusting the strength expression rate. For example, as a method for increasing the strength development rate, water cement water [W / C] or water binder ratio [W / B] may be reduced, or the amount of unit cement may be increased. For example, the water cement ratio, the water binder ratio, the cement water ratio, and the water binder ratio can be increased, the amount of unit cement can be reduced, and the fly ash that is a pozzolanic material can be increased. These will be further described later.

[Second stage]
In the second stage, a target date for realizing a predetermined strength is determined in common for all the partial layer regions L ₁ , L ₂ ... And calculated backward from the target date according to the management material age of each partial layer region. Determine the placement date for each partial layer area.

That is, as shown in FIG. 5, the concrete in each of the partial layer regions L ₁ , L ₂ ... Reaches the target strength on the same day. As shown in the figure, the lower partial layer region has a faster casting date, which means that the strength development rate of the concrete increases from the lower side to the upper side.

[Stage 3]
In the third stage, the concrete is repeatedly placed on the placement date determined for each partial layer region in order from the lower partial layer regions L ₁ , L ₂ .

  That is, in the present invention, the concrete in the first partial layer region is driven and the concrete in the second partial layer region is repeatedly driven before the concrete strength reaches the target value. In contrast, conventionally, as shown in FIG. 6, after the strength of the concrete in the first partial layer region reaches the target value, the concrete is repeatedly placed in the next partial layer region.

  If the slope of the graph of each layer in FIG. 6 is about the same as the slope of the graph of the third layer in FIG. 5, the slope of the second layer in FIG. 5 is smaller than that of the second layer in FIG. The slope of the second layer of 5 is smaller than that of the second layer of FIG. “If the water cement ratio [W / C] or water binder ratio [W / B] is small, the strength of the concrete increases, and if there are many pozzolanic materials such as fly ash with a slow reaction rate, the strength increases in the long term.” Therefore, when the configuration of FIG. 5 of the present application is adopted, the amount of cement used is smaller than that of the configuration of FIG. Since the amount of cement used is small, the amount of heat of hydration generated in a large cross-sectional area can be reduced.

[Example 1]
7 to 9, with reference to the actual formulation example, the water cement ratio [W / C] and the water binder ratio [W / B = W / (C + F)] are adjusted to set the management material age. The method to perform is demonstrated.

  The contents of the test were concretely tested in the room, cylindrical specimens having a diameter of 10 cm × 20 cm were prepared, and the strength of these specimens was measured. Table 1 shows the materials used for concrete. "AE water reducing agent" in the table is an AE water reducing agent mainly composed of lignin sulfonate, oxycarboxylate and polycarboxylic acid compound, and "high performance AE water reducing agent" is a polycarboxylate compound. It is an AE water reducing agent as a main component, and all conform to JIS A 6204.

  Using the materials listed in Table 1, six types of concrete having different water cement ratios and water binder ratios were used as slumps targeted by adjusting the amount of admixture added to form six types of specimens. Table 2 shows an overview of the concrete mix.

Table 3 shows the results obtained by measuring the strengths of these six types of specimens on the 1st, 7th, 14th, 28th, and 56th days from the placement date. It can be seen that the greater the water cement ratio (or water binder ratio), the slower the development of strength. Also, among the six types of test bodies, the test body No. Regarding 1 to 5, the relationship between the number of days (age) from the placement date and the compressive strength is summarized in the graph of FIG. In the graph, the black circle line indicates the relationship when the water binder ratio W / B is 54%, the white rhombus line indicates the relationship when W / B is 49%, and the white triangle line indicates the W The relationship when / B is 45%, the white square line indicates the relationship when W / B is 42%, and the white circle line indicates the relationship when W / B is 38%. . The black thick line is a line with a compressive strength of 40 N / mm ² and is a temporary target strength. By changing W / B from 38% to 54%, the age until reaching the target strength can be changed from a little less than 10 days to a little over 50 days. In the present invention, using this phenomenon, the placement date is adjusted so that the days when the plurality of concrete layers reach the required strength are the same.

  The multiple regression equation obtained from the above experimental results is shown below. Where Fn is the compressive strength on the nth day after placement, (C + F) / W is the binder water ratio, M, which is the reciprocal of the water binder ratio [(W / (C + F) = W / B], M Is the integrated temperature.

[Formula 1]
Fn = 22.0 × {(C + F) / W} + 23.6 × Log ₁₀ (M) −73.6

  FIG. 9A shows the relationship between the age and the compressive strength when the average temperature is 10 ° C., and FIG. 9B shows the relationship between the age and the compressive strength when the average temperature is 20 ° C. Represents the result of calculation based on Formula 1 for each predetermined water binder ratio (W / B).

When the average temperature is 10 ° C., as shown in FIG. 9A, when W / B = 38%, around 12 days, when W / B = 45%, around 28 days, W / B = 54. In the case of%, the target strength (40 N / mm ² ) is reached around 56 days. When the average temperature is 20 ° C., as shown in FIG. 9B, when W / B = 38%, around 8th day, when W / B = 45%, around 19th day, W / B = 54. In the case of%, the target strength (40 N / mm ² ) is reached around the 41st day. These numerical values may be applied to the blending design method described with reference to FIG.

  In addition, since the object constructed by the present invention is a concrete reaction body, even if the specifications of the concrete such as W / B are changed for each layer, there is a problem in terms of the function of the concrete reaction body. Absent.

[Example 2]
Next, the use of the pozzolanic reaction as a means for adjusting the strength development rate of concrete will be described. The pozzolan reaction generally means that a pozzolan composed mainly of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) can react slowly with calcium hydroxide at room temperature to produce a compound having a binding force. It is. Since the pozzolanic reaction is a slower reaction than the hydration reaction of cement, the strength of concrete is extended over a long period of time by including pozzolanic in the concrete material. Including the increase in strength due to this pozzolanic reaction, if the management age of concrete is set, the strength development speed of the entire concrete can be slowed down. An example of a pozzolanic material is fly ash.

DESCRIPTION OF SYMBOLS 1 ... Existing building 2 ... Existing pile 2a ... Test pile 3a, 3b ... Column beam frame 4 ... Column 4a ... Leg-cut column 5a, 5b ... Beam 6 ... Foundation frame 6a ... Foundation frame part above test pile 7 ... Concrete reaction force Body 7A, 7B ... Concrete reaction wall
10 ... working space 12 ... contact surface E ... edge G ... gap J ... jack _{L 1, L 2, L 3} ... partial layer region _{N 1, N 2, N 3} , N 4, N 5, N 6 ... reinforcing Column outline

Claims (5)

A vertical loading test method for reusing existing piles used in an existing building when rebuilding a building,
Cutting the edge between the existing pile to be tested and the foundation frame of the existing building,
Above the existing pile, a concrete reaction body construction step for constructing a concrete reaction body having a predetermined strength with a configuration capable of obtaining a reaction force of a test load from an existing building;
A jack is installed at the upper end of the existing pile, the jack and the concrete reaction body are connected, and a test load is applied to the existing pile by the jack to measure the support performance, and the measurement step comprises:
The concrete reaction body construction step is as follows:
The concrete reaction force casting area is divided into at least two horizontal partial layer areas in the vertical direction, and each partial layer area is required to achieve a predetermined strength through a curing period from the placement date. A first sub-step for determining the management age, which is the number of days;
Set a target date that should achieve a predetermined strength common to all partial layer areas, and determine the placement date of each partial layer area by calculating backward from the target date according to the management age of each partial layer area A second sub-step;
In order from the lower partial layer area, the third sub-step is repeated to repeat placing concrete on the casting date determined for each partial layer area,
A vertical loading test method for existing piles, wherein a predetermined strength of all partial layer regions is achieved on the same target day. It is a construction method of a concrete reaction body added to the frame of an existing building in order to perform the vertical loading test method of the existing pile according to claim 1,
The concrete reaction force casting area is divided into at least two horizontal partial layer areas in the vertical direction, and each partial layer area is required to achieve a predetermined strength through a curing period from the placement date. A first stage for determining the management age, which is the number of days,
Set a target date that should achieve a predetermined strength common to all partial layer areas, and determine the placement date of each partial layer area by calculating backward from the target date according to the management age of each partial layer area The second stage,
In order from the lower partial layer area, it consists of a third stage that repeats the placement of concrete on the casting date determined for each partial layer area,
The concrete reaction force body is constructed by being connected to at least the lowest column beam structure facing the existing pile in the building frame composed of the column beam frame. A method for constructing a concrete reaction body characterized in that a gap for jack insertion is formed between a lower end surface and an existing pile. The concrete reaction body is composed of at least one concrete reaction wall that connects the columns of one column beam structure and is integrated with the beam. Divided into partial layer regions, formed by sequentially placing each partial layer region,
The method for constructing a concrete reaction body according to claim 2, wherein the management age of concrete in each partial layer region is shortened from the lower side to the upper side.   The concrete reaction body is formed by the two concrete reaction walls according to claim 3 formed by intersecting and uniting each other above an existing pile. Method.   The placement area of the concrete reaction force body is set so that the wall thickness of both concrete reaction force walls is large at a location near the existing pile, and is small at a location far from the existing pile. Construction method of concrete reaction body.