JP2007231570A - Reinforcing structure of pc wall body member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of a great deviation in the distribution of stress after construction by unevenly distributing and arranging prestressing steel on the cross-sectional surface of a PC wall body member which constitutes a PC continuous wall body as an earth retaining structure, composed of precast concrete. <P>SOLUTION: On the cross-sectional surface of the PC wall body member 1 which constitutes the PC continuous wall body as the earth retaining structure, composed of the precast concrete 2, a large number of pieces of prestressing steel 6 for imparting prestress to the PC wall body member 1 are characteristically arranged on a soil-side end surface section 4a, and a small number of pieces of prestressing steel 6 are arranged on an excavation-side end surface section 5a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure in which a PC steel material that applies prestress to a PC wall member is unevenly arranged in a cross section of the PC wall member.

  Conventionally, for example, a technique using a PC wall member 21 made of precast concrete 22 as shown in FIG. 3 and constituting a PC continuous wall 28 as a retaining structure is known. A large number of individual PC wall members 21 are connected in a watertight manner to construct a PC continuous wall 28 (see, for example, Patent Document 1).

  As shown in FIG. 3, the top of the PC continuous wall 28 is driven at substantially the same height as the ground surface 29 a on the left back soil side 29. The ground is excavated to a predetermined depth on the right side of the PC continuous wall body 28, and the right space of the PC continuous wall body 28 is the excavation surface side 30. The PC continuous wall 28 is embedded to a predetermined depth further from the excavation surface side ground surface 30a.

  The constructed PC continuous wall 28 is subjected to earth pressure and water pressure as bending loads from the back soil side 29 within a range where there is no reaction force from the excavation surface side 30. When the distribution state of earth pressure and water pressure is independently indicated by arrows, these sizes become maximum at a depth position coinciding with the excavation surface side ground surface 30a. Thus, tensile stress is generated on the soil side end surface portion 29b of the PC continuous wall body 28 (PC wall body member 21) that receives the bending load, and compressive stress is generated on the opposite excavation side end surface portion 30b.

  FIG. 4A shows a cross section of one PC wall member 21 which is a component of the PC continuous wall 28. The vertical direction in the figure is the wall thickness direction of the PC wall member 21. FIG. 4B shows a distribution state of stress generated in the PC wall member 21 in the wall thickness direction. The PC wall member 21 is formed in a square cross section, and is provided with a circular hole 23 into which a drilling drill is inserted at the center. In this cross-sectional view, the lower side of the circular hole 23 is the soil side end surface portion 29b, and the upper side is the excavation side end surface portion 30b. A horizontal line passing through the center of the circular hole 23 is a neutral axis of displacement of tension and compression.

  The same number of PC steel materials 26 are symmetrically arranged on the soil-side end surface portion 29b that receives earth pressure and water pressure across the neutral axis, and on the excavation-side end surface portion 30b on the opposite side. Accordingly, the prestress (compressive force) applied to the PC wall member 21 by the PC steel material 26 is uniformly applied in the wall thickness direction in the cross section (see the central view of FIG. 4B).

On the other hand, the tensile stress and the compressive stress due to the bending load of earth pressure and water pressure are changed from the tensile stress generated in the soil side end surface portion 29b to the compressive stress generated in the excavation side end surface portion 30b with the neutral axis as a boundary in the cross section. Switch. The combined stress of the stress due to the bending load and the prestress (compressive force) is biased and becomes only compressive stress as shown in the right figure of FIG. 4B, and the excavation side end face 30b (upper side of the figure) where the maximum compressive stress occurs. ) Will cause a large stress. For this reason, there is a problem that the design of the PC wall member 21 is restricted in order to counter this large stress.
Japanese Patent Laid-Open No. 2005-111977

  Therefore, the present invention reduces the number of PC steel materials disposed on the excavation side end surface portion in the cross section of the PC wall member, and increases the number of PC steel materials disposed on the soil side end surface portion. The warpage of the PC wall body member is directed toward the back soil side (control of the top displacement), and the PC wall body member is not biased toward the excavation side end surface portion so that no compressive stress is generated, and no large stress is generated. It is an object to reduce the cost by making it possible to reduce the total number of PC steel materials.

  In order to solve the above-described problems, in the first invention, prestress is applied to the PC wall body member in the cross section of the PC wall body member that is composed of precast concrete and constitutes the PC continuous wall body as the earth retaining structure. PC steel materials to be distributed are arranged unevenly.

  Moreover, in 2nd invention, the arrangement | positioning number of the earth side end surface part in the cross section of a PC wall body member is more than the arrangement number of an excavation side end surface part in the 1st invention in the 1st invention.

  The third invention is characterized in that, in the first invention, a predetermined number of PC steel materials are arranged on the soil side end surface portion in the cross section of the PC wall member, and are not arranged on the excavation side end surface portion.

  The fourth invention is characterized in that in the first to third inventions, the PC wall member is reinforced by using a cross-sectional structure.

  According to the first invention, if the PC steel material is unevenly arranged on the soil side end surface portion, the compressive stress at the time of prestress can be made to cancel the tensile stress due to earth pressure and water pressure, and at the same time, the uneven distribution at the time of prestress Since the compressive stress at the excavation side end surface can be reduced, it is possible to suppress the combined compressive stress with the compressive stress due to earth pressure and water pressure from being greatly biased to the excavation side end surface, and to reduce the maximum value.

  Further, the uneven distribution of PC steel materials can reduce the total number of PC steel materials and reduce the cost.

  Furthermore, if the PC steel material is unevenly distributed on the soil side end surface, the top of the PC wall member at the time of prestress can be warped to the soil side, and the design can be made in a direction to cancel the warp to the excavation side due to earth pressure and water pressure. Therefore, it becomes easy to suppress and control the displacement of the top.

  According to the second invention, a large number of PC steel materials are disposed on the soil side end surface portion, and a small number are disposed on the excavation side end surface portion, so this corresponds to the case where the uneven distribution in the first invention is made on the soil side end surface portion. The same effect is obtained.

  According to the third invention, since the PC steel material is not disposed on the excavation side end surface, the effect of the second invention can be obtained more easily.

  According to the fourth invention, the effect of any one of the structures of the first invention to the third invention is obtained. In particular, the effect of reducing the number of PC steels arranged is great.

  Next, a reinforcing structure of a PC wall member to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a case where two PC wall members 1 which are made of precast concrete 2 and constitute a PC continuous wall body as a retaining structure are connected. This PC wall body member 1 is connected to the PC wall member 1 in a state where each PC wall member 1 is self-supported by arranging the PC wall member members 1 in the ground by the Nakabori method as described in the background art section. Built. Each PC wall member 1 is formed in a prismatic shape, and a circular hole 3 for inserting an excavation drill is formed in the center of the cross section. The front side of the PC wall member 1 in FIG. 1 is the back soil side 4 that receives earth pressure and water pressure, and the back side is the excavation surface side 5.

  FIG. 2A is a square cross-sectional view of the PC wall member 1. The lower side of the cross-sectional view is the back soil side 4, and the upper side is the excavation surface side 5. Most of the PC steel materials 6 (35 in this case) arranged in the cross section are arranged concentrated on the soil side end surface portion 4a, and the periphery of the circular hole 3 and the excavation side end surface portion 5a. A small number of PC steel materials 6 are arranged in the. Prestress (compressive force) applied to the PC wall member 1 due to the uneven distribution of the PC steel material 6 is not uniform in the cross section and is biased toward the back soil side 4.

  On the other hand, FIG. 2B shows a stress distribution state in the wall thickness direction of the PC wall member 1. Due to the uneven distribution of the PC steel material 6, the neutral axis of the displacement is shifted downward from the center of the circular hole 3. Here, the stress distribution when the neutral axis is placed at the horizontal center of the circular hole 3 is shown as an image. Since the bending load due to earth pressure and water pressure is the same as in the background art, the distribution of the composite stress in the wall thickness direction is suppressed from being largely biased toward the excavation surface side 5, and the maximum value can be reduced.

  In the present invention, the PC steel material 6 may be arranged only on the back soil side 4 in accordance with the magnitude of the bending load due to earth pressure and water pressure and the strength of the PC wall member 1.

  In this way, the PC steel material 6 that applies prestress (compression force) to the PC wall member 1 is not uniformly distributed in the cross section, but is concentrated on the soil side end surface portion 4a. The warp of the PC wall member 1 can be generated on the back soil side 4 with stress (compressive force) applied, and the stress can be effectively suppressed. At the same time, the number of PC steel members 6 can be reduced as a whole, and the cost can be reduced.

  Further, if the PC steel material 6 is unevenly arranged on the soil side end surface portion 4a, the top portion of the PC wall member 1 at the time of pre-stress is warped to the back soil side 4, and the warpage to the excavation side 5 due to earth pressure and water pressure cancels each other. Therefore, it becomes easy to suppress and control the displacement of the top portion.

It is a perspective view of a PC wall member. (A) is a cross-sectional view of a PC wall member, (b) is an image diagram showing the stress distribution in the cross-section. It is a figure which shows the load conditions which the PC wall body member of an installation state receives. (A) is a cross-sectional view of the PC wall member in the background art, (b) is an image diagram showing the stress distribution in the cross-section.

Explanation of symbols

1,21 PC wall member 2,22 Precast concrete 3,23 Circular hole 4,29 Back soil side 4a, 29b Earth side end surface
5, 30 Excavation surface side 5a, 30b Excavation side end surface 6, 26 PC steel material 28 PC continuous wall body 29a Ground surface on the back soil side 30a Ground surface on the excavation surface side

Claims (4)

  A PC wall comprising a PC wall member made of precast concrete and constituting a PC continuous wall body as a earth retaining structure, wherein a PC steel material that prestresses the PC wall member is unevenly arranged. Reinforcement structure for body members.   The reinforcing structure for a PC wall member according to claim 1, wherein the number of the earth-side end surface portions of the PC steel material in the cross section of the PC wall member is larger than the number of the excavation-side end surface portions.   2. The PC wall member structure according to claim 1, wherein a predetermined number of the PC steel materials are disposed on the soil side end surface portion in the cross section of the PC wall member, and are not disposed on the excavation side end surface portion.   A method of reinforcing a PC wall member, comprising reinforcing the PC wall member using the cross-sectional structure according to any one of claims 1 to 3.

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