JPH10252053A - Method for measuring strength of sand pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sand pile strength measuring method whereby a high- quality sand pile that always satisfies design specifications can be constructed by detecting and evaluating in real time the strength of a sand pile at each depth during construction of the sand pile. SOLUTION: A sand-compacting diameter-increasing device which is moved up and down by a cylinder is fitted to the end of a hollow pipe for constructing a sand pile, sand is forced out from inside the hollow pipe, the diameter of the device is increased, and the sand pile is compacted. During that process, average pushing pressure when the compacting diameter-increasing device moved up and down falls, the depth of the end of the hollow pipe, the height of the surface of sand in the hollow pipe, and compressed air pressure within the hollow pipe are detected, and the relation of them with sand pile strength is compared with previous data for statistical evaluation and measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the strength of a sand pile, and more particularly to a method for evaluating and detecting the strength of a sand pile at each depth in real time while forming the sand pile.

[0002]

2. Description of the Related Art Conventionally, in the improvement work of soft ground,
Based on the results of soil surveys at multiple points in the improvement area, an average design ground strength is designed, and a ground strength target value that matches the weight and shape of the assumed upper structure is calculated for this. The diameter of the formed pile and its construction pitch are determined so as to obtain the target strength.

[0003] Also, for the strength confirmation after the soil improvement work, a standard penetration test is performed at a plurality of points in the improvement area in the same manner as before the construction, and the strength of the entire improvement area is evaluated based on the value. There was a problem that the ground strength of the entire improved area was evaluated only in terms of points.

[0004] In the prior art, a method of detecting the strength of the surrounding ground by the pressing force of a sand compaction device that moves up and down has been proposed, but this method directly detects the strength of a sand pile. Therefore, data such as air pressure inside the hollow pipe related to sand discharge and diameter expansion, height of the sand surface inside the hollow pipe, and the depth of the hollow pipe tip related to the strength of the sand pile are not included. However, there was a problem that the strength was poor in reliability.

[0005]

The present invention solves the above-mentioned problems of the conventional method, detects and evaluates the strength of a sand pile at each depth during sand pile formation in real time, and always satisfies the design specifications. The present invention proposes a method for measuring the strength of a sand pile capable of forming a high-quality sand pile.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems in order to achieve the above object, and as a result, have developed a sand tamping and expanding device provided at the tip of a hollow pipe for sand pile formation. As we arrived at the present invention by obtaining the knowledge that the strength of the sand pile can be measured in real time by acquiring and analyzing the pressing force and other related data at that time when building the sand pile by moving it up and down is there.

That is, the first invention of the present invention is equipped with a compacting and expanding device that moves up and down by a cylinder at the tip of a hollow pipe for sand pile formation, and forcibly discharges sand from inside the hollow pipe. While expanding the diameter and compacting the sand pile, the average pressing pressure at the time of descending of the compacting and expanding device which moves up and down in the process, the depth of the tip of the hollow pipe, the height of the sand surface in the hollow pipe and the compression in the hollow pipe This is a sand pile strength measurement method that detects air pressure and statistically evaluates and measures the relationship between these and the sand pile strength with past data.

In the second invention, the average pressing force (Wp) at the time of descending of the sand compacting and expanding device when the sand compacting and expanding device expands and compacts the discharged sand is described. Tip depth of hollow tube (Dep), height of sand surface in hollow tube (As
l), the air pressure in the hollow tube (Cs) and the cylinder pressing force (Wp ₀ ) at the time of calibration (at the initial stage) are detected, and the partial regression coefficients (α, β, γ, δ) and the constant term (C) are determined in the past. Statistically calculated from construction data, the following correlation formula

N = α · (Wp−Wp ₀ ) + β · Dep +
γ · Cs + δ · Asl + C

In this method, the sand pile strength (N value) during sand pile formation is detected in real time, and the sand pile is formed based on the detected strength. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a tamping and expanding device according to the present invention, FIG. 2 is a schematic explanatory view of a method of the present invention, and FIG.
FIG. 2 is a process chart showing an example of a construction flow of the method of the present invention.

In the figure, reference numeral 1 denotes a hollow pipe for forming a sand pile.
Is equipped with a sand compaction expanding device having a compaction wing 2 attached to the lower end of a rod 4 of a downward cylinder 3 for forcing sand introduced into the hollow tube 1 into soft ground. The sand is piled out and the sand is compacted to create sand piles.

At this time, the average pressing force (Wp) and depth (Dep) of the tamping wing 2 reciprocating up and down when descending, the sand level inside the hollow tube (Asl), and the air pressure (Cs) inside the hollow tube are measured. By recording and analyzing, the strength (N) of the sand pile at the depth during sand pile formation is measured (see FIG. 2).

The correlation equation for calculating the pile-building strength is calculated in the form of a multivariate analysis of the following equation (1), and the partial regression coefficient and the constant term can be obtained statistically from past construction data. N = α · (Wp−Wp ₀ ) + β · Dep + γ · Cs + δ · Asl + C ·· (1)

N: N value (standard penetration test value = sand pile strength) Wp: Cylinder pressing force (Kg / cm ² ) Wp ₀ : Pressing force during calibration (initial pressing force) (Kg / cm ² ) Dep: depth (m) Cs: air pressure in hollow tube (Kg / cm ² ) Asl: sand surface height in hollow tube (m) α, β, γ, δ: partial regression coefficient C: constant term

The partial regression coefficient (α,
β, γ, δ) and the constant term (C) can be detected and measured in real time at each depth by inputting the data obtained in each construction to the computer as parameters.

The method of the present invention is performed according to the following procedure. (1) The hollow tube 1 for sand pile formation is lifted to the sea surface 5 and the pressure of the hydraulic cylinder in the sand and the hollow tube 1 under no load without any pressure is measured. The initial value of the pressing force (Wp ₀ )
As input to the computer.

(2) A partial regression coefficient (α, β, γ, δ) and a constant term (C) of each parameter derived by statistical processing from past construction results accumulated so far are input to a computer. However, the partial regression coefficient and the constant term may be obtained by performing a test construction before the start of the construction and obtaining the values at the site. Further, the above (1) and (2) need only be input once before the start of the construction or before the start of the casting of the day.

(3) A hollow pile-forming hollow tube 1 having a vibration compacting and expanding device at the lower end thereof and an exciter mounted at the upper end thereof is suspended by a wire, and the soft ground 7 is formed while operating the exciter. It is driven to a predetermined depth at a predetermined position.

(4) Sand is charged and filled into the hollow tube 1, and while the hollow tube 1 is pulled out, the vibrating tamping device is moved up and down to forcibly remove the sand in the hollow tube 1 from the ground. Drain into.

(5) The cylinder pressing force (Wp) of the compacting and expanding device at that time, the depth (Dep) of the tip of the hollow tube 1,
The air pressure (Cs) in the hollow tube 1 and the sand surface height (Asl) in the hollow tube 1 are measured, and after calculating by a computer, the sand pile strength (N value) is displayed on a display (see FIG. 3). ).

(6) When the sand pile strength (N value) does not satisfy the specifications, an alarm sounds and informs the operator, the hollow pipe 1 is driven back, and the pile is formed again. Thus, the sand pile strength (N
Value) and continue pile building.

[0023]

The present invention is configured as described above and has the following effects. (A) The strength of the sand pile can be measured during the formation of the sand pile, and a high-quality sand pile that always satisfies the specifications can be formed.

(B) Since the strength of the sand pile at each pile and each depth can be measured, the improved ground, which could only be evaluated as a point in the conventional check boring, can be three-dimensionally evaluated.

(C) According to the method of the present invention, an automatic pile making system for automatically controlling a drawing speed of a hollow pipe and a depth of the hollow pipe by a computer judging a signal such as a discharge state of material sand and a design sand amount. Can be linked with the automatic sand supply system and the construction data automatic processing system that automatically supply the sand piles of uniform quality without depending on the skill of the operator. Since it is possible to evaluate the strength of piles, it has a high construction management ability with respect to work type and quality.

(D) Since the pile-building strength can be measured in real time and on the total number of cast sand piles, the number of check borings is reduced, and therefore the number of days spent on check boring can be reduced, thereby shortening the construction period and the cost. It leads to reduction.

(E) Since the strength of the sand pile is checked during the formation, the rate of increase in the used material can be reduced, which is economical.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a sand compaction and diameter increasing device according to the present invention.

FIG. 2 is a schematic explanatory view of construction of the present invention.

FIG. 3 is a process chart showing an example of a construction flow of a construction method according to the present invention.

[Explanation of symbols]

 1-Hollow tube 2-Compacted wing 3-Cylinder 4-Rod 5-Sea surface 6-Construction surface 7-Soft ground surface Wp-Cylinder pressing force Asl-Sand surface height in hollow tube Dep-Depth of hollow tube tip Cs-air pressure in hollow tube CPU-computer CRT-display

Claims (2)

[Claims] 1. A sand tamping and expanding device, which moves up and down by a cylinder, is provided at the tip of a hollow pipe for forming a sand pile to forcibly discharge and expand the sand from inside the hollow pipe and tighten the sand pile. The compacting is performed, and in the process, the average pushing pressure, the depth of the hollow tube tip, the sand surface height inside the hollow tube, and the compressed air pressure inside the hollow tube are detected when the tamping expanding device that moves up and down moves down.
A method for measuring the strength of a sand pile, characterized by statistically evaluating and measuring the relationship between these and the strength of a sand pile by comparing with past data. 2. A sand tamping and expanding device, which moves up and down by a cylinder, is provided at the tip of the hollow tube for sand pile formation to forcibly discharge and expand sand from inside the hollow tube and tighten the sand pile. During the hardening process, the average pressing force (Wp) when the cylinder descends, the tip depth of the hollow tube (Dep), the height of the sand surface in the hollow tube (Asl), the air pressure in the hollow tube (Cs) and the calibration (Initial) cylinder pressing force (W
p ₀ ), and a partial regression coefficient (α, β, γ, δ) and a constant term (C) are statistically obtained from past construction data.
The following correlation formula N = α · (Wp−Wp ₀ ) + β · Dep + γ · Cs + δ
A method for forming a sand pile, comprising: detecting a sand pile strength (N value) during sand pile formation in real time from Asl + C; and forming a sand pile based on the detected strength.