JPS5818488B2 - Underwater structure foundation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention supports the bottom surface of an underwater structure on the underwater ground surface with a required gap between the two, and supports the bottom surface of the underwater structure using earth mortar using soil excavated from the seabed. The purpose of this method is to inject the foundation between the bottom surface of the underwater structure and the underwater ground surface. The purpose of this invention is to provide an improved foundation construction method for constructing the foundations of underwater structures at low construction costs and with high reliability, by using excavated soil from the seabed, which would otherwise have to be discarded, as the main raw material for filling material for foundation construction. be.

In the present invention, as a filling material injected between the underwater base surface and the bottom surface of an underwater structure supported on the same plane with a gap, earth excavated soil from the seabed, which was conventionally dumped, is used as the main material. Since mortar is used, it is extremely economical.

Moreover, the earth mortar has good fluidity and does not cause material separation when placed underwater, shrinkage of the mortar in water is extremely small, and the unit volume weight is almost equal to that of seabed ground, so it has good workability and does not require secondary injection. Even if the seabed ground is soft, the injected material will not sink into the seabed ground, and according to the method of the present invention, it is possible to create a highly reliable foundation for an underwater structure.

The present invention will be described below with reference to the illustrated embodiments.

In Figures 1 and 2, A is an immersed box suspended in the water, its rear end is pressed by water pressure to the front of the existing immersed box A', and its tip is placed on the pre-excavated underwater ground B. Place it on temporary support C.

At this time, a space necessary for injecting and filling the earth mortar described below should be provided between the bottom of the immersed box A and the seabed ground B, taking into consideration the unavoidable unevenness of the foundation ground surface during construction. .

Next, as shown in FIG. 1, the seabed ground B is excavated in order to install the next immersed burial box A'', and the excavated soil 1 is carried into the earth carrier 2.

Then, the excavated soil on the carrier ship 2 is thrown into a peptizing mixer 5 by a grab 4 mounted on the work barge 3.

The solid glue mixer 5 is, for example, disclosed in Japanese Patent Application Laid-open No. 48-84.
The mixer for high viscosity substances described in Japanese Patent Application No. 47-15642 may be used.

A dispersible surfactant is further added to the peptizer mixer 5 on the work barge 3 from a surfactant storage tank 6, and seawater is injected from a submersible pump 7. The clay soil is loosened and the thus obtained muddy soil is stored in a notch tank 8 on the work barge 3.

The dispersible surfactant/active agent added to the peptizer mixer 5 may be, for example, a maleated resin prepared by adding maleic anhydride to abietic acid and saponified with short-chain amines as described in Japanese Patent Publication No. 38-21624. By adding colloidal silica and synthetic rubber emulsion to this to make a homogeneous emulsion, we aim to improve the quality and strength of earth mortar by improving the effect of loosening the lumpy clay soil. .

A submersible sand pump 9 is disposed in the notch tank 8, and the pump 9 supplies the deflocculated soil in the tank 8 to the next notch tank 10.

A mud content meter 11 is installed in the piping connecting both the tanks 8 and 10.
and a flow meter 12 are interposed, and the signals from both meters are sent to the meter 13 which has a built-in calculation circuit and control circuit.
The flow rate of seawater supplied to the Notchi tank 10 by the submersible pump 14 is adjusted by the electromagnetic valve 15 installed in the seawater supply pipe to the tank 10 in response to a signal from the Notchi tank 10. The soil concentration is made constant by the mixer 16.

The peptized soil at a certain concentration in the Notchi tank 10 is sent to the hopper 19 of the next sand pump 18 by the sand pump 17 disposed in the tank 10. An electromagnetic flowmeter 20 interposed in the piping from 17 to the hopper 19 sends a flow rate signal to a meter 21 with a built-in control circuit, which controls the feeder motor 23 attached to the cement silo 22. , a certain ratio of cement to the peptized soil to be delivered by the sand pump 17 is delivered to the hopper 19 of the sand pump 18 , and the cement-soil-water mixture is thus delivered to the pipeline mixer 24 by the sand pump 18 . Deliver.

The mixture is sufficiently mixed to become earth mortar while passing through the pipeline mixer 24, and enters the hopper 26 of the grout pump 25.
through the injection pipe 27 to the immersed box A and the seabed ground B.
It is injected into the gap between the

The injection pipe 27 is attached to a truck 28 that runs on the submerged burial box A, and by moving the truck 28, the entire gap is filled with the earth mortar D.

In FIGS. 4 and 5, 29 is a detection tube arranged in parallel with the injection tube 27, and a suction pressure measuring device 30, a pH meter 31, and an electric resistance meter 32 are attached to the detection tube 29. The injection pipe 27 is rotated while discharging earth mortar along a quarter-circular arc.

When the injection pipe 27 stops discharging the earth mortar and rotates in the opposite direction, the detection pipe 29 absorbs mud, and the instruments measure the suction pressure of the earth mortar, the pH 1, and the conductivity state of the absorbed water passing through the detection pipe. is measured and continuously recorded to detect the degree of filling of T7-7 and -E rutal.

Figure 6 shows the flow of soil excavated from the seabed into the deflocculation mixer.
When earth mortar is produced by adding a dispersive surfactant (trade name: Formix...manufactured and sold by Hamano Seni Kogyo Co., Ltd.) as described in the above-mentioned Japanese Patent Publication No. 38-21624, , which compares the unconfined compressive strength of earth mortar with respect to the water-cement ratio when earth mortar was manufactured without using the above-mentioned dispersible surfactant.

This is because even if the excavated soil is only mechanically and physically loosened with a deflocculating mixer, small aggregates remain.When cement is added to this to make earth mortar, the size and amount of the small aggregates are As shown in Figure 6 a, only an earth mortar with inferior strength can be produced due to the strong influence of the earth mortar. As shown in (b), it was found that the strength of the earth mortar was significantly increased.

Although the present invention has been described above with reference to embodiments, the present invention is, of course, not limited to such embodiments, and can be modified in various designs without departing from the spirit of the present invention. .

[Brief explanation of drawings]

1 and 2 are a side view and a front view, respectively, showing the implementation status of the underwater structure foundation construction method according to the present invention, and FIG. 3 is a side view and a front view of a work barge used in the method of the present invention. Figures 4 and 5
The figures are a front view and a plan view of the earth mortar filling status detection device, respectively, and FIG. 6 is a chart comparing the strength of earth mortar to which a dispersive surfactant is added and earth mortar to which no dispersive surfactant is added. A: Submerged box, B: Undersea ground, C:
...Temporary support, D...Earth mortar, 1
・・・－・・・Excavated soil, 3・・・・・・Work barge, 4・−
... Peptizer mixer, 6 ... Surfactant storage tank, 10 ... Notsuchi tank, 22 ...
・Cement silo, 24...pipeline mixer, 25...grout pump, 27...
- Injection pipe, 28... trolley.

Claims (1)

[Claims] 1. Support the bottom of the underwater structure on the underwater ground surface with a required gap between the two, and inject earth mortar using excavated seabed soil between the bottom of the underwater structure and the underwater ground surface. An underwater structure foundation construction method that is characterized by: