JP2005147735A - Measurement method for ground subsidence amount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect ground displacement by means of a relatively simple and low-cost device by reducing reactive force to subsidence and consolidation to the utmost limit to enhance the accuracy of displacement measurement by devising a displacement detection structure part when measuring a ground subsidence amount in reclamation work. <P>SOLUTION: A flexible net-like body 1, such as a wire basket deformable in compliance with the subsidence shape of ground, is laid on the ground on which reclamation material is placed in underwater or undersea reclamation work to measure the amount of ground subsidence by a pore pressure meter 2 attached to the net-like body 1. The net-like body 1 is deformed in compliance with the subsidence shape of the ground to measure sinking displacement of the reclamation material into a sea bottom ground, etc. by the pressure meter 2 integral with the net-like body 1. The pressure meter 2 is connected to a float 3 by a stainless wire 4a and a signal line 4b to transmit a measurement signal by radio from the float 3 to on-board and on-land management devices. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for measuring the amount of land subsidence in landfill work such as in the ocean and lakes.

  For example, for the measurement of land subsidence in offshore reclamation work, a saddle-type subsidence plate is conventionally used, and as shown in FIG. 2, a measuring rod (1) provided with a rod 51 provided with a subsidence plate 50 at the bottom. (Not shown) was installed on the sea, and the height of the top of the rod 51 protruding onto the sea was measured and managed to grasp the subsidence of the seabed.

  In addition, subsidence is measured by a subsidence plate of the type in which a pore water pressure gauge is installed in a protective box. FIG. 3 is an example of the measuring device, and the subsidence plate 60 measures the subsidence of the seabed ground (local board) A. The height of the upper surface of the subsidence plate 60 is measured by water pressure, and the amount of subsidence is calculated from the amount of change. A cylindrical box 61 made of a perforated steel plate is mounted on the subsidence plate 60, and a sponge is placed in this box. A pore water pressure gauge 63 wrapped with 62 is arranged, and coarse sand 64 is filled around it. A is a local board, B is a landfill, and such measuring devices are installed in many places.

Moreover, there exists patent document 1 as a prior art document relevant to this invention. The invention of Patent Document 1 is a ground deformation measurement system that measures the amount of settlement of a laying ground in landfill work as needed. A pair of optical fiber sensor pairs arranged vertically is laid in a lattice shape, and a sensor is detected at an arbitrary point in the ground. The subsidence and uplift of the ground at that position are discriminated based on the vertical strain difference in the pair, and a two-dimensional distribution of subsidence and uplift is created and displayed every predetermined time.
Japanese Patent Laid-Open No. 2003-232631

  Both the above-mentioned saddle type subsidence plate, protection box and pore water pressure gauge type subsidence plate have a plate-like bottom surface, which is the displacement detection structure, and this plate receives the reaction force against subsidence and consolidation on the entire bottom surface (plate area). There was a concern that it would remain higher than the actual subsidence depth (smaller than the actual displacement) (see FIG. 2). That is, there is a slight problem in measurement accuracy with respect to the displacement of the landfill material into the seabed ground. Further, in the case of the invention of Patent Document 1, since the optical fiber sensors are arranged in a lattice shape up and down, the cost is increased.

  In the present invention, when measuring the amount of ground subsidence in landfill construction, by devising the displacement detection structure, the reaction force against subsidence and consolidation can be minimized, and the accuracy of displacement measurement can be increased. An object of the present invention is to provide a ground subsidence measuring method that can detect ground displacement with a relatively simple and low-cost device.

  The present invention is a method for measuring the amount of subsidence of the ground where a landfill material is installed in landfill construction underwater or underwater, and is a flexible mesh that can be deformed following the subsidence shape of the ground on the ground. This is a ground subsidence measurement method characterized in that a body is laid and the ground subsidence is measured by a pore water pressure gauge provided on the net.

  A net-like body such as a wire mocco with a pore water pressure gauge attached to the lower surface or the like is laid on the upper surface of the seabed, the bottom of the seabed or the soft ground improvement work, and the landfill material is put on this. The ground sinks due to settlement and consolidation, but the mesh body can minimize the reaction force against settlement and consolidation, and deforms following the settlement of the ground, so the pore pressure gauge integrated with the mesh body (pressure change ) Can measure the displacement of the landfill material into the seabed and the like, and can more accurately measure the amount of subsidence than conventional subsidence plates.

  Also, in the above measurement method, the wiring (connecting member such as stainless steel wire and signal line) connected to the pore water pressure gauge is connected to a float on the sea or water, and the measurement signal is sent from this float to a shipboard or onshore management device. send. There is also a method of transmitting directly to a monitoring location without using a float. The wiring is covered with a flexible protective tube. It is only necessary to arrange a simple and small float on the sea or on the water, and there is no hindrance to the construction of construction work such as a clay ship or a landing ship.

  (1) A flexible net that can be deformed following the subsidence of the ground is laid on the ground for underwater or underwater landfill work, and the amount of ground subsidence is measured by the pore water pressure gauge provided on the net. Can measure the displacement of landfill material into the seabed by using a pore water pressure gauge (pressure change) integrated with the mesh body, and more accurately measure the amount of subsidence than conventional subsidence plates. Can do.

  (2) The ground displacement can be detected with high accuracy by a relatively simple and low-cost apparatus comprising a net and a pore water pressure gauge.

  Hereinafter, the present invention will be described based on the illustrated embodiments. This embodiment is an example in which the present invention is applied to the measurement of the displacement / sinkage amount due to the reclamation of the seabed ground in the offshore reclamation work. FIG. 1 shows an example of a ground subsidence measuring method and measuring apparatus according to the present invention.

  In FIG. 1, a measuring device used in the present invention mainly includes a wire net (wire mocco) 1 as a displacement detection structure (sink plate), and a pore water pressure gauge 2 disposed under the net 1, It is composed of a float 3 installed on the sea, and a wiring 4 connecting the pore water pressure gauge 2 and the float 3.

  The wire net 1 is a sheet-like net of about 2m x 2m consisting of vertical and horizontal wires 1a, and the subsidence shape of the sea floor a (upper surface of soft ground improvement work, etc.) when landfill material such as rubble S is thrown in. Can easily follow and deform.

  The wiring 4 includes a stainless steel wire 4 a as a connecting member and a signal line 4 b for transmitting a measurement value, and a distal end portion is connected to the pore water pressure gauge 2 and a proximal end portion is connected to the float 3. The signal line 4b of the float 3 is opened to the atmosphere so that a measurement signal can be transmitted wirelessly or by wire to a ship or land management device.

  The pore water pressure gauge 2 is disposed in a protective tube 5 having both ends opened, such as a flexible or rigid gas tube, and the inside of the protective tube 5 is filled with sand 6. Such a protective tube 5 is preferably fixed under the wire 1 a of the net 1.

  The stainless wire 4a and the signal line 4b are covered with a flexible inner protective tube 7 as shown in FIG. 1C, for example, and the protective tube 7 is covered with a flexible outer protective tube 8. Further, a stainless wire 9 is disposed between the protective tube 7 and the protective tube 8.

  The wire net 1 with the pore water pressure gauge 2 configured as described above is installed at a predetermined measurement location on the sea floor a. The landfill material is put on this. The bottom surface a sinks due to settlement or consolidation, but the wire net 1 is not subject to surface resistance like an iron plate, and deforms following the settlement shape of the bottom surface a, so the amount of settlement can be measured more accurately. it can.

  In the subsidence plate data installed in the sand compaction pile ground improvement part, the subsidence amount of the conventional type is 320 mm, while the subsidence amount of the wire net and pore water pressure gauge method of the present invention is 550 to 700 mm, which is accurate. You can see that it is being measured.

  In addition, although the example which applied this invention to the measurement of the land subsidence amount of a sea landfill construction was shown above, this invention is applicable not only to this but landfill construction, such as a lake, and other landfill works.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an example of a ground subsidence measuring method and measuring device according to the present invention, (a) is a perspective view showing the whole of a float and the like and a measuring device, and (b) is a part of a net and a pore water pressure gauge. The side view to show, (c) is a fragmentary sectional view which shows the middle part of wiring. It is explanatory drawing which shows the displacement of the sinking board by a conventional method. The installation state of the conventional protection box and a pore water pressure gauge type settlement board is shown, (a) is a perspective view, (b) is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wire network 1a ... Wire 2 ... Pore water pressure gauge 3 ... Float 4 ... Wiring 4a ... Stainless steel wire 4b ... Signal wire 5 ... Protective tube (pore water pressure gauge)
6 ... Sand 7 ... Inside protective tube (wiring)
8 …… Outer protective tube (wiring)
9 …… Stainless steel wire

Claims (2)

  This is a method to measure the amount of settlement of the ground where the landfill material is installed in underwater or underwater landfill construction, and a flexible net that can be deformed following the shape of the ground settlement is laid on the ground. A method for measuring the amount of ground subsidence, characterized in that the amount of ground subsidence is measured with a pore water pressure gauge provided on the net. 2. The method of measuring ground subsidence according to claim 1, wherein the wiring connected to the pore water pressure gauge is connected to a float on the sea or water and a measurement signal is transmitted from the float.

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