JP2886373B2 - The management method in the vibration compaction method of the saturated sand ground - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of compacting a saturated sandy ground such as a saturated loose sandy ground which is liable to liquefaction due to vibrations by vibrating the ground. ).

[0002]

2. Description of the Related Art Conventionally, in the vibration compaction method for a saturated sandy ground, a construction depth of a vibrating rod and a load current of a vibration source are measured at the time of construction, and a construction range and a load condition of the vibrating rod are managed. In addition, a standard penetration test is performed at required places after the completion of all construction, and strength management is performed by obtaining the N value of the ground.

[0003]

In the above-mentioned conventional construction management method, the management at the time of construction does not directly relate to the quality requirement (vibration compaction degree) of each construction, and the quality control of each construction is not performed. It is not done at all, and the standard penetration test performed after the completion of all construction is ex post factual, so it is not possible to respond to real-time quality requirements for each construction, and it takes a lot of labor and cost to perform the penetration test And so on.

[0004]

According to the present invention, in order to solve the above-mentioned conventional problems, an inspection pipe having a built-in pore water pressure gauge 14 (instead of the water supply / drain pipe 9) is provided in the ground around the press-fitting portion of the vibrating rod 7. The vibrating rod 7 is re-vibrated after the compaction is performed by the vibratory compaction method, and the generated excess pore water pressure is measured. Based on the measured value, the compaction degree is properly managed in real time each time construction is performed. It is intended to propose a management method in a vibration compaction method for a saturated sandy ground.

[0005]

By moving the moving vehicle 1 to the compaction position, the water supply / drain pipe 9 and the vibrating rod 7 can be moved together with the vibrating bodies 6 and 8 at their upper ends, and can be constructed immediately. The water supply / drain pipe 9 and the vibrating rod 7 can be laid down smoothly.

In soft ground to be improved, excess pore water generated by vibration of the vibrating rod 7 during compaction by vibration is discharged to the ground surface through a water supply / drain pipe 9 to prevent liquefaction around the vibrating rod 7. Then, the vibration energy of the vibration rod 7 is effectively transmitted, and the vibration compaction is performed reliably.

[0007]

1 to 5 show a vibration compaction method to be controlled by the present invention and a construction apparatus used for the method. First, the construction apparatus will be described. The construction apparatus is provided at the tip of a moving vehicle 1 such as a crawler. An elevating device 3 is attached to the leader 2 so as to be able to move up and down, and a gantry 5 is suspended from the elevating device 3 via a hanging cable 4 so as to be able to move up and down.

A vibrating rod 7 made of H-shaped steel or the like having a vibrating body 6 attached to the upper end thereof is suspended below the gantry 5. A plurality of vibrating bodies 8 are attached to the vibrating rod 7 at the upper end in series around the vibrating rod 7. The water supply / drain pipe 9 is suspended via a suspension cable 10, and the lower ends of the vibrating rod 7 and the water supply / drain pipe 9 are gripped by a shake preventing arm 11 so as not to swing when moving.

The vibrating body 8 is formed in an annular shape having a cavity in the center of which the vibrating rod 7 can be inserted, and a plurality of water supply / drainage pipes 9 are arranged on a lower surface thereof at predetermined intervals.

The water supply / drain pipe 9 is provided with a water supply / drainage hole 12 at least at the end thereof.

Water is jetted from the water supply / drain hole 12 to the periphery by pumping water, and the inside of the water is sucked by a vacuum pump 13 so that the surrounding water is sucked and discharged to the surface. A pore pressure gauge 14 is provided at a required position.

Although the pore water pressure gauge 14 is provided in the water supply / drainage pipe 9 and also serves as an inspection pipe, it may be separately provided in a dedicated inspection pipe and press-fitted simultaneously with the water supply / drainage pipe 9.

[0013] In the vibration compaction construction, first while injecting water jets from plumbing holes 12 and water in the plumbing line 9 as shown in FIG. 2, pressed simultaneously to a required depth ground by the vibration of the vibrating body 8 Then, as shown in FIG. 3, the vibrating rod 7 is pressed into the vibrating body 6 while applying vertical or shear vibration to compact the ground, and at the same time, the excess pore water pressure generated in the ground due to the vibration is reduced to the surrounding pressure. Vacuum suction is performed from the water supply / drain hole 12 of the water supply / drain pipe 9 to remove it to the surface.

As described above, when the vibration is compacted by the vibrating rod 7, the excessive pore water is generated due to the vibration. However, since the excessive pore water pressure is discharged to the surface through the water supply / drain pipe 9, the excess pore water around the vibrating rod 7 is removed. Liquefaction is prevented, vibration energy of the vibration rod 7 is effectively transmitted, and vibration compaction is reliably performed.

[0015] The above-described compaction work is carried out for the moving vehicle 1 sequentially.
The vibrating rod 7 is continuously moved in multiple points over the entire ground to be constructed while moving, and the vacuum suction of the water supply / drain pipe 9 is stopped every time the compaction work is completed at each point. Inspection vibration is performed, and the excess pore water pressure in the ground generated by this is measured by the pore water pressure gauge 14,
The degree of compaction (liquefaction strength of sand) is calculated based on the measured values.

"Comparative Experimental Example"

A water supply / drainage pipe 9 is installed on the ground around the vibrating rod 7 (press-fitted to a depth of 5 m using H-shaped steel) by using the direct power compaction method in the reclaimed land at Takakake-numa, Rokkasho-mura, Kamikita-gun, Aomori Prefecture. The vibrating rod 7 is vibrated at the initial frequency and 1 m above and below the point at a depth of 5 m.
The vibratory compaction process of raising and lowering the water to a certain extent and absorbing and removing excess pore water pressure generated by the water supply / drain pipe 9 is defined as one cycle, and the compacted ground obtained by performing this process for 4 cycles and 8 cycles respectively, and the initial state before compaction of creating three test soil with soil, experiments were conducted by installing a respective pore pressure gauge 14 and the accelerometer 15 at a point 1m and 2m from the vibrating rod 7, as shown in FIG.

First, a standard penetration test was conducted at a point 2 m away from the vibrating rod 7 in each of the above-mentioned panels, and as a result,
A change in the Nd value as shown in FIG.
It was found that the ground was compacted in the order of compaction for 4 cycles and compaction for 8 cycles.

Further, when the behavior of the excess pore water pressure Δu during the inspection vibration by the vibrating rod 7 was examined, it was found that, as shown in FIG. 8, the tighter the ground, the less the pore water pressure was generated during the inspection vibration. .

Further, the vibration acceleration amplitude (gal) in the ground
When the relationship between the excess pore water pressure ratio (△ u / σV ′) and the excess pore water pressure ratio (△ u / σV ′) was obtained, the results shown in FIG. 9 were obtained, and it was found that the more firmly the ground, the smaller the generated pore water pressure amount for the same acceleration. Here, σV 'is the effective earth covering pressure, that is, 5 m depth
Means the earth pressure excluding the water pressure at the point
V '= 0.4 kgf / cm2.

The ratio (△ u / σV '/ η) of the excess pore water pressure ratio (△ u / σV') to the ground acceleration η is expressed as
FIG. 1 is a graph showing the relationship between this value and the Nd value.
0 constant relationship as shown in, i.e. ξ value that is obtained liquefaction strength of the ground as to decrease is increased by obtaining the data in search of these relationships in a number of various fastening solid Me ground, It is possible to measure the excess pore water pressure and properly perform compaction management using the ξ value as an index. The ground vibration acceleration η at this に お け る value is managed based on the measurement result of the excess pore water pressure by omitting the measurement by the accelerometer each time by applying measured values or analysis values obtained from many experiments in advance. can do.

[0022]

As described above, according to the present invention, each time compaction work is completed at each point, an inspection vibration is performed by the vibrating rod, and the excess pore water pressure in the ground generated by this is measured by the pore water pressure gauge. Then, based on this measurement value, an index closely related to the compaction degree (liquefaction strength of sand) can be calculated, and the compaction effect on the sand ground can be calculated in real time and based on this index. It is possible to manage easily and economically without installing a management device in the factory, and it is possible to perform appropriate compaction work under such management.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a state before vibration compaction according to the present invention.

FIG. 2 is a vertical sectional side view showing a state of the vibration compaction work according to the present invention.

FIG. 3 is a longitudinal sectional side view showing a state of vibration compaction work according to the present invention.

FIG. 4 is a longitudinal sectional side view showing a state of vibration compaction work according to the present invention.

FIG. 5 is a longitudinal sectional side view showing a state of vibration compaction work according to the present invention.

FIG. 6 is a diagram showing an outline of experimental conditions according to the present invention.

FIG. 7 is a diagram showing a change in Nd value due to vibration compaction according to the present invention.

FIG. 8 is a diagram showing the behavior of excess pore water pressure during inspection vibration obtained by an experiment according to the present invention.

FIG. 9 is a diagram showing a relationship between vibration acceleration of sand and excess pore water pressure obtained by an experiment according to the present invention.

FIG. 10 shows the ξ value and N obtained by the experiment according to the present invention.
FIG. 3 is a diagram illustrating a relationship between d values.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Moving vehicle 2 Leader 3 Elevating device 4 Hanging line 5 Stand 6 Vibrating body 7 Vibrating rod 8 Vibrating body 9 Water supply / drainage pipe 10 Hanging line 11 Anti-shake arm 12 Water supply / drainage hole 13 Vacuum pump 14 Pore water pressure gauge 15 Accelerometer

Claims (1)

(57) [Claims] 1. A vibration rod having a vibrating rod mounted thereon is pressed into the ground while applying vertical or shearing vibration by vibrating the vibrating body, compacting the ground, and simultaneously reducing excess pore water pressure generated in the ground by the vibration. In the vibration compaction method of the saturated sand ground so as to be eliminated by a drain pipe penetrating into the ground around the vibrating rod, an inspection pipe with a built-in pore water pressure gauge is provided in the ground around the press-fitting part of the vibrating rod, After the compaction is performed by the vibration compaction method, the vibrating rod is re-vibrated, the generated excess pore water pressure is measured, and the compaction degree is controlled based on the measured value. Management method of vibration compaction method.