JPS6125859B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a technique for improving soft ground by constructing a large number of sand piles in the ground.

(Problems to be solved by the invention and its characteristics) The purpose of improving soft ground is to consider the weight, shape, etc. of various structures that will be built on the soft ground in the future, and to create a safe ground that is commensurate with that. but,
Actual weak ground has variations in soil properties, and this is especially noticeable in artificial ground such as reclaimed land.When constructing sand piles on such soft ground, conventionally,
Taking the case of focusing on ground strength as an example, at the design stage, an average value (not limited to the average value) is
Set the design original ground strength, determine the diameter and pitch of the sand piles so as to obtain the target improved ground strength based on this design original ground strength, and carry out the actual construction according to this design. However, because the design base ground strength, which is the basis of the design, is an average, variations in the actual ground strength are directly reflected in the actual improved ground strength, resulting in uneven ground improvement. There was a problem.

The present invention has been made in view of this point, and its characteristic configuration is as described in the claims.

That is, as is clear from its characteristic configuration, the present invention detects the soil properties of the original ground at each construction point prior to constructing each sand pile, and reflects this detection result in constructing each sand pile. By doing so, we were able to harmonize the design with reality and ensure that the improved ground was uniform.

(Specific explanation of the invention with drawings) Figure 1 is a schematic diagram showing a comparison between the conventional technology and the present invention, where a is the actual ground strength, b is the design ground strength, and c is the target ground strength. The improved soil strength, d, is the actual improved soil strength. In the conventional technology shown in (), d varies in the same way as a, whereas in the present invention shown in (), d coincides with c. This shows that the ground can be uniformly improved according to the present invention.

Figure 2 shows an example of a sand pile construction device used in the construction method of the present invention. In this figure, 1 is a hollow pipe, 2 is a hydraulic piston cylinder device, and 3 is a sand discharge/compaction member. , 4 is the outer tube, 5 is the penetrating machine, 6
7 is a fountain nozzle, 7 is a hopper, 8 is an air valve, and 9 is a compressed air supply pipe.

To construct a sand pile using this device, first, the hollow pipe 1 is penetrated into soft ground to a predetermined depth.
At this time, injecting pressurized water from the fountain nozzle 6 or operating the piston/cylinder device 2 in addition to operating the penetrator 5 facilitates penetration.

Next, sand is poured into the hollow tube 1 from the hopper 7,
Hollow tube 1 while operating sand discharge and compaction member 3
When the hollow tube 1 is continuously pulled out, sand is discharged from the lower end of the hollow tube 1 and compacted by the sand discharge/compaction member 3 to form a sand pile.

The diameter of the sand pile being constructed is calculated based on the values obtained from the sand level gauge that detects changes in the sand surface inside the hollow pipe 1 and the depth gauge that detects the bottom depth of the hollow pipe 1. Since this is well known, detailed description thereof will be omitted.

In the present invention, the soil properties of the original soil at each construction point are detected prior to the construction of each sand pile. Taking the case of detecting the strength of the original soil as an example, sand is discharged and tightened when the hollow pipe 1 is penetrated. Detecting the penetration resistance acting on the tip of the hardening member 3 from the oil pressure of the piston cylinder device 2,
Detection may be carried out based on this detected value, or detection may be carried out by providing a dedicated detection means (stress measuring gauge, load cell, etc.) at an appropriate location in the hollow tube 1.

In the present invention, the above-mentioned detection results are reflected at the time of sand pile construction, and specifically, this is done as follows.

When changing the sand pile diameter in response to variations in the detected original ground strength with respect to the design original ground strength, in places where the detected original ground strength is greater than the design original ground strength, the pile diameter should be changed to the design standard. The pile diameter is made smaller than the pile diameter, and conversely, the pile diameter is increased in places where the detected original ground strength is low. This change in the pile diameter can be done by changing the drawing speed of the hollow pipe 1. Alternatively, pressure water may be injected from the fountain nozzle 6 onto the ground around the hollow pipe 1 to temporarily weaken the surrounding ground in a limited area to facilitate expansion of the sand pile diameter.

When changing the sand pile strength in response to variations in the detected original ground strength with respect to the design original ground strength, the strength of the prepared sand pile should be made larger than the standard design sand pile strength in accordance with the above case. However, this change in the strength of the sand pile can be achieved, for example, by applying vibration to the sand discharge/compaction member 3 mentioned above and changing either or both the frequency and amplitude of this vibration. I can do it.

When changing both the type and strength of the sand pile for construction in accordance with the above two cases, this can be done by changing the stroke length of the sand discharge/compaction member 3, the number of times it moves up and down per unit time, etc.

Note that although the above description is about ground improvement using sand piles, gravel, crushed stone, slag, and other similar materials can be used instead of sand, and the present invention is also applicable when these are used.

(Effects of the Invention) As is clear from the above description, according to the present invention, it is possible to reliably transform original ground with uneven soil texture into uniform improved ground, and the quality of the improved ground is guaranteed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram comparing the conventional technology and the present invention.
FIG. 2 is a schematic diagram showing an example of an apparatus for implementing the present invention. 1...Hollow tube, 2...Piston/cylinder device, 3...Sand discharge/compaction member,...

Claims (1)

[Claims] 1. In a method of improving soft ground by constructing a large number of sand piles in soft ground, in order to obtain a uniform improved ground, the soil properties of the original soil at each construction point are detected prior to constructing each sand pile, Each sand pile is created while changing one or both of the sand pile diameter and sand pile strength in response to the difference between the detected original soil properties and the design original soil properties determined as an average at the time of design. A soft ground improvement method characterized by: