JPS5825126B2 - Switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of vibratory compaction of underwater soil, which is suitable for improving the compaction of submerged sandy ground over a wide area using a vibrating rod.

In general, ground improvement methods include building sand piles at regular intervals in soft ground, building the sand piles while vibrating and compacting them, and simply inserting a vibrating rod into the existing ground to vibrate. Methods of compaction are known.

Among the above methods, when compacting sand piles using vibrating rods, consider the quality of sand suitable for sand piles, the spacing between sand piles, the duration of vibration with vibrating rods, the degree of impact of compaction, etc. For example, depending on the condition of the ground to be improved, sand piles are placed at intervals of 2 m or less, and each sand pile is compacted with a vibrating rod for about 1 to 3 minutes, so that 10 to 20 kg/m is applied to the sand pile part. It is clear that a ground pressure strength of has been done.

In contrast, for mild ground improvement that does not require as much ground pressure strength, a method is used in which the vibrating rod is simply penetrated into the existing ground and compacted. Appropriate excitation time, excitation force, and degree of compaction effect for vibrating rods of various shapes are still not fully clear, and the compaction interval of 7 g is the same as in normal sand pile construction.
The reality is that compaction is carried out by continuing vibration for several minutes at the - point with a vibration acceleration of about 100 degrees.

The present invention has been proposed in view of the above circumstances, and involves penetrating the ground to be compacted while vibrating it with a vibrating rod having a protrusion in the shape of a hook, donut, spiral, etc. on the outer periphery. At the same time, an appropriate amount of overburden pressure was applied to the ground surface around the vibrating rod, and the vibrating rod was continuously vibrated for about 3 minutes at a vibration acceleration of 2.5 g to 3 g, and then the vibrating rod was pulled out while being vibrated. Below, the same method as described above is sequentially applied to the ground at a plurality of locations with intervals of 8 times or less the outer diameter of the overhanging part of the vibrating rod to proceed with compaction of the same ground, vibrating underwater sediment. The purpose of the compaction method is to provide an efficient and rational improved soil compaction method.

The present inventors have found that a vibrating rod having a hook-shaped, donut-shaped, or spiral-shaped protrusion on its outer periphery with a comparatively large vertical contact surface is extremely effective for vibration compaction of the ground using a vibrating rod. One thing is that as the load amount of the overload pressure increases in this method, it promotes the soil compaction effect during vibration, and on the other hand, a large amount of vibration energy is required. It is necessary to select a method in which the soil compaction action by the vibrating rod is a vibration with a vibration acceleration in the range of 2.5 to 3 g, and the effective compaction action is almost completed without being affected by changes in the vibration frequency. further vibration acceleration is unnecessary, effective compaction of the ground is substantially completed within approximately 3 minutes of vibration duration of the vibration rod, and further vibration duration is unnecessary; The method is extremely effective for mild compaction improvement of sandy ground with low silt content, and if the compaction interval by the vibrating rod is set to within 8 times the rod diameter, the compaction effect will be the same as that of the vibrating rod penetrating at 2 or 3 locations. The method of the present invention was proposed after confirming through experiments that the soil is compacted evenly throughout the area because the compaction acts redundantly between the points and further compacts the ground.

According to the method of the present invention, vibration compaction is performed by penetrating the existing ground with a vibrating rod and applying a required weight of soil loading pressure to the outer periphery of the vibrating rod, so that the accompanying work is simple and easy. In particular, there is no difficulty in compacting the submerged soil.
This method is suitable, and since the above-mentioned protruding portion is provided on the outer periphery of the vibrating rod, the vibratory compaction effect is significantly improved.

According to the method of the present invention, vibration compaction using a vibrating rod is performed with the minimum necessary vibration acceleration and vibration duration, so less power is used than in the past, and soil compaction work can be carried out efficiently in a short time. It is done.

Further, according to the method of the present invention, the compaction work using the vibrating rod is sequentially performed on the ground at multiple points at intervals of up to 8 times the outer diameter of the protruding part of the rod, thereby proceeding with compaction of the same ground. Therefore, the vibration compaction effect by the vibrating rod is 2 to 3.
Since the vibrating rod acts redundantly between the vibrating rod penetration points and is further compacted, a substantially uniform compacted ground can be obtained as a whole.

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

A vibrating rod 4 having a vibration exciter 3 on its head is suspended from a work boat (not shown) floating on the water surface above the water bottom ground 1 to be compacted via a cable 5, and the same vibration is applied to the water bottom ground 1 to be compacted. A plurality of weights 7 having a required weight are suspended from the barge 6 via cables 8 onto the underwater ground 1 around the outer periphery of the rod 4, and these weights 7 are applied as an overload pressure onto the underwater ground 1.

The outer periphery of the main body of the vibrating rod 4 is provided with a hook-shaped protrusion 9 as shown in FIG. 2, a donut-shaped protrusion 9 as shown in FIG. 3, or a spiral protrusion as shown in FIG. A projecting portion 9 or a cross-shaped projecting portion 9 as shown in FIG. 5 is provided.

In this method, as mentioned above, from the work boat to the underwater ground 1
The vibrating rod 4 suspended at a desired position is vibrated by the vibrating machine 3 to cause the vibrating rod 4 to penetrate into the underwater ground 1, and the external cylinder of the vibrating rod 4 is applied to the ground surface as described above. An appropriate amount of weight 7 corresponding to the rated output of the vibrator 3 is placed to apply soil pressure, and under this condition, the vibrator 3 applies a vibration acceleration of 2.5 g to 3 g to the vibrating rod 4. After continuing the vibration for about 3 minutes, the vibrating rod 4 is gradually lifted up while applying the same vibration.

Thereafter, the same operation is sequentially performed at each apex position of the triangle, with the interval being within 8 times the outer diameter of the overhanging portion of the vibrating rod 4, thereby performing compaction.

Note that the weight 7 serving as the upper pressure may be placed slightly wider than the predetermined penetration point of the vibrating rod (by leaving it at a slightly wider area), and may also be placed by suspending the vibrating rod 4 above the penetration point, and then moving the vibrating rod 4 It may be arranged from above the barge 6 while the barge is being penetrated into the underwater ground 1.

The weight 7 at the point where the compaction by the vibrating rod 4 has been completed is moved to the next scheduled penetration point and used.

By arranging the weight 7 in advance or in parallel with the penetrating work of the vibrating rod 4 in this way, compaction by the vibrating rod 4 can be efficiently carried out sequentially and continuously at scheduled points.

The embodiment shown in FIG. 1 shows a state in which one set of vibrating rods 4 is used, but the same operation as described above is carried out by arranging two or three similar vibrating rods 4 at regular intervals. This further improves work efficiency.

The vibration of the vibrating rod 4 in the underwater ground 1 imparted by the vibrator 3 as described above is propagated to the surrounding ground around the rod, and at the same time the weight of the weight 7 is transmitted into the surrounding ground. As a result, the pore water pressure in the ground increases and the effective stress in the sand decreases, and then the ground surface sinks and the relative density and bearing capacity of the ground increases.

Furthermore, as mentioned above, the vibration rod 4 is
The vibration acceleration in the range of 2.5 g to 3 g and the vibration duration of about 3 minutes provide just the right amount of compaction for sandy ground with relatively little silt content.

6 to 10 are graphs showing the degree of ground improvement measured from work using the above method, and FIG. 6 shows the support when the overburden pressure is changed under a constant output of the vibrator 3. The solid curve in the figure shows the increase in force, and the solid line curve in the figure shows particle size dispersion (referring to the state in which large and small soil within a certain area of the ground is dispersed,
A large or small particle size distribution means that the difference in grain size of the soil is large or small.

), and the dashed line curve shows the measurement results for sandy ground with a smaller particle dispersion.The magnitude of the overburden pressure is indicated by S on each curve. There is.

Also in the above-mentioned example of the ground, the greater the overburden pressure S, the higher the ground strength shown as penetration resistance.

It can also be seen that the penetration resistance increases in proportion to the relative density.

This relative density, that is, the degree of compaction, has a correlation with the output of the vibrator 3, so the bearing capacity (target value) expected of the improved soil
Once this has been set, the expected soil strength can be determined by appropriately selecting and adjusting the magnitude of the soil bearing pressure and the exciter output by comparing it with the old ground strength to be improved and the target value determined in advance. Supporting force can be obtained.

FIG. 7 shows the increase in the ground supporting force depending on the magnitude of the vibration acceleration g of the vibrating rod 4, and the solid line 2D in the figure indicates the
The broken line 2.6D shows the measurement results at a point 2.6 times the distance from the center of the rod's outer diameter, and the broken line 2.6D shows the measurement results at a point 2.6 times the distance from the center of the rod. Figure 8 shows the relationship between the magnitude of the vibration acceleration g and the gap ratio of the ground loaded with different overburden pressures, and the magnitude of the overburden pressure is indicated by S on each curve.

Further, the distance between straight lines A and A' shown in FIGS. 7 and 8 indicates the range of vibration acceleration g specified by the method of the present invention.

As is clear from Figure 7, the ground bearing capacity is 1.25
Figure 8 shows that the ground gap ratio increases sharply at vibration accelerations of about 1 g, and remains approximately constant at higher vibration accelerations. The decrease starts with vibrations of 1.5 g or more, and the decrease in the ground gap ratio becomes almost constant when vibrations have an acceleration of 3 g or more.

Therefore, in the method of the present invention, the vibration acceleration is 2.5.
In the range A-A' of 3 g to 3 g, the ground compaction effect can be efficiently achieved by reducing the ground gap ratio and increasing the supporting force by using the necessary minimum vibration acceleration.

Next, FIGS. 9 and 10 show the relationship between the vibration duration of the vibrating rod 4, the amount of ground surface settlement, and the pore water pressure.
Figure 9 shows the ground surface settlement around the vibrating rod 4 after 10 seconds, 60 seconds, 120 seconds, and 180 seconds of vibration duration when vibration compaction is performed at a vibration acceleration of 3 g. As shown in Fig. 10, the ground surface subsidence at a point four times the rod diameter from the vibrating rod 4 indicated by the black dot in Fig. 9, and the ground surface subsidence at a point four times the rod diameter indicated by the white dot. It shows a change in pore water pressure, and when the vibration duration exceeds 3 minutes, both the pore water pressure change and the ground surface subsidence become almost static.

Therefore, from the above, it can be seen that by continuously vibrating the vibrating rod 4 for about 3 minutes in a penetrating state according to the method of the present invention, an efficient and effective ground compaction effect can be achieved in the minimum necessary time.

As described above, according to the method of the present invention, in light compaction work of this type of ground, the compaction work can be performed economically and efficiently with the minimum necessary steps, power, and compaction time. The ground can be improved to make it stronger.

Furthermore, as shown in FIG. 9, the amount of ground surface subsidence at a point four times the rod diameter of the vibrating rod 4 is approximately 1/3 of the amount of subsidence at the point closest to the vibrating rod. If the compaction point spacing is within 8 times the rod diameter, the compaction action will overlap between the two or three vibrating rod penetration points, and the ground will be further compacted, so the compaction will be approximately even as a whole. Compacted ground can be obtained.

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 ways without departing from the spirit of the present invention.

[Brief explanation of drawings]

Fig. 1 is a front view showing the implementation status of the method of the present invention, Figs. 2 to 5 are partial perspective views showing each embodiment of the vibrating rod, and Fig. 6 is a diagram showing the relationship between the relative density of the ground and the penetration resistance. Graph showing the relationship, Figure 7 is a graph showing the relationship between the vibration acceleration of the vibrating rod and the ground bearing capacity increase rate, Figure 8 is a graph showing the relationship between the vibration acceleration of the vibrating rod and the ground gap ratio, Figure 9 is a graph showing the relationship between the distance from the vibrating rod in the ground and the amount of ground surface subsidence, and FIG. 10 is a graph showing the relationship between the vibration duration due to the vibrating rod, the pore water pressure in the ground, and the amount of ground surface subsidence. DESCRIPTION OF SYMBOLS 1... Underwater ground, 3... Vibrator, 4... Vibration rod, 7... Weight, 9... Overhanging part.

Claims (1)

[Claims] 1 A vibrating rod with a hook-shaped, donut-shaped, spiral-shaped, etc.-shaped protrusion on its outer periphery is penetrated into the ground to be compacted while vibrating, and an appropriate amount of overburden pressure is applied to the ground surface around the vibrating rod. After applying a load and continuously vibrating the vibrating rod at a vibration acceleration of 2.5 g to 3 g for about 3 minutes, the vibrating rod is pulled out while being vibrated, and the same method as above is used to adjust the outer diameter of the protruding part of the vibrating rod. Consolidate the ground by applying it to the ground at multiple locations one after another with a distance of 8 times or less, or
Alternatively, a method for vibratory compaction of underwater soil, characterized in that a plurality of the vibrating rods are connected in series at a distance within 8 times the outer diameter of the overhanging part, and the same vibration is sequentially applied to the ground at a plurality of points.