JP2704302B2 - Permeability test method and equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a test method and apparatus for detecting the degree of water permeability in the ground, that is, the coefficient of water permeability.

(Conventional technology) Regarding the underground permeability test, for example, when a construction method such as caisson or shield is carried out in civil engineering work, the geology of the excavation site, head, pore water pressure and the amount of spring water are detected, and various construction methods are used. It is important to set safe and reasonable construction conditions in advance in order to determine the hydraulic conductivity to be implemented.

For these, a test pipe was inserted into the ground by the auger method or piezometer method, etc., and the water level retained in the pipe was changed to a certain position, and the water level change per unit time to recover to the natural water level from there. Methods have been developed to measure the velocity and thereby determine the hydraulic conductivity.

(Problems to be Solved by the Invention) However, in the case of the conventional method described above, especially in the case of the auger method, suspended particles in the pores are classified and settled and deposited at the bottom of the measuring tube, and significantly impede water permeability. Even in the case of the piezometer method, the excavated hole wall collapses and eventually impedes water permeability as in the case of the above-mentioned auger method, and the collapse of the stratum disturbs the original stratum and obtains an accurate permeability coefficient There was a problem that it was not possible.

(Means for Solving the Problems) Therefore, the present invention solves the above-mentioned problems of the conventional technology,
Deterioration of water permeability into the measurement tube, and furthermore, prevention of collapse of the hole wall surface so that a more accurate water permeability coefficient can be obtained.Specifically, a step of boring to a depth immediately before the measurement point Inserting a casing into the boring hole, and driving the tip of the casing deeper than the bottom of the hole, loading a rod having a hollow strainer detachably attached to the tip into the casing, and inserting the rod into the casing. The present invention relates to a water permeability test method comprising: a step of excavating while rotating in a fixed direction to position a strainer at a measurement position; and a step of reversing a rod, removing the strainer from the strainer, and calculating a water permeability coefficient based on the amount of water permeated into a casing.

Further, the present invention relates to a water permeability test device in which a strainer is inserted into a casing driven into the bottom of a boring hole, and a permeability coefficient is obtained in a state where the strainer is excavated at a measurement position. Can be detachably connected to a rod with a water supply pipe protruding from it, a metal crown is attached to the opening edge of the tip, and a number of water holes are drilled in the body, and the outer peripheral surface is porous. The present invention also relates to a permeability test device surrounded by a filter.

(Operation) The strainer of the present invention has an outer diameter somewhat smaller than the inner diameter of the casing, so that a sand gap with an appropriate gap is formed between the lower end of the casing and the strainer, and as a result, the strainer accumulates when the rod is removed. Particles can be prevented from entering the strainer.

In addition, by providing a large number of water holes in the body of the strainer and surrounding the outer surface with a porous filter, it is possible to prevent the deterioration of the stratum and the clogging of the strainer due to the collapse of the hole wall surface, and the groundwater into the strainer Can smoothly flow.

(Embodiment) Hereinafter, the specific contents of the present invention will be described with reference to the embodiment shown in the drawings. 1 indicates a hollow strainer, and 8 indicates a rod attached to the strainer 1.

The strainer 1 has an outer diameter somewhat smaller than the inner diameter of the casing 12 and, as shown in detail in FIG. 2, a female along the inner peripheral surface so that the rod 8 can be connected to the proximal end (the upper end in the figure). A threaded portion 6 is provided, and a stopper groove 5 which is gradually tapered from the opening edge toward the depth of the female threaded portion 6 and has a stopper 5a is formed in one of the opening edges. At the same time, a metal crown 4 for excavation is attached to the opening edge of the tip (the lower end in the figure).

Further, the body 2 of the strainer 1 is provided with a large number of water passage holes 3 in the circumferential direction, and the body 2 is formed in a step-like shape with a small diameter, and the outer peripheral surface thereof has a porous shape. It is surrounded by a filter 7 and is configured such that the outer peripheral wall surface of the filter 7 and the outer peripheral wall surface of the strainer 1 are substantially flush.

The filter 7 used in this case may be made of any material as long as it is porous and water-permeable, such as rock wool. However, plastic sintered granules are more preferable because they have high water permeability. .

On the other hand, the rod 8 is hollow and has a male screw portion 9 corresponding to the female screw portion 6 provided on the base end side of the strainer 1 on the outer peripheral surface near the distal end, and a key 11 is integrally formed on the upper portion thereof. Is provided.

Further, a water supply pipe 10 that can be inserted into the inner peripheral side of the body 2 protrudes forward (downward in FIG. 2) from the male screw portion 9.

The above-mentioned connection between the strainer 1 and the rod 8 is achieved by inserting the water supply pipe 10 of the rod 8 into the body 2 of the strainer and rotating the rod 8 clockwise so that the female screw 6
The male screw part 9 is screwed into the inside.

However, after most of the male screw portion 9 is screwed into the female screw portion 6, the key 11 descends from the end face of the strainer 1 and enters the stopper groove 5 along the tapered surface, and further comes into contact with the stopper 5a and further. Is prevented.

Therefore, when conducting the water permeability test, as shown in FIG.
Then, the casing 12 is inserted into the boring hole 13 and the tip of the casing 12 is driven into a portion deeper than the bottom of the hole (see FIG. 1 (A)).

Next, the rod 8 having the strainer 1 detachably attached to the tip is inserted into the center of the casing 12, and the rod 8 is rotated clockwise while water is supplied from the rod 8 to the opening of the strainer 1 through the water supply pipe 10. While drilling, the bottom of the hole is self-bored by the metal crown 4 of the strainer 1 until the depth reaches the measured depth (see FIG. 1 (B)).

When the strainer 1 reaches a predetermined position, the water supply and the rotation of the rod are stopped, and after waiting for the settling of the suspended particles, the rod 8 is rotated reversely and removed from the strainer 1 to remove water from the ground in a porous manner. It is led into the strainer 1 from the body 2 through the filter 7, and based on the amount of water per unit time, The hydraulic conductivity is determined based on the known formula described above (see FIG. 1 (C)).

Further, after the end of the water permeability test, the rod 8 is inserted into the strainer 1 again to be connected, and then pulled up.

If a ball 13 made of plastic or the like is loosely fitted in the opening of the tip of the strainer 1, the ball 13 closes the opening when pumping up the water permeated in the casing 12, and a so-called boiling phenomenon occurs. Can be prevented.

(Effect of the Invention) As described above, the present invention inserts a rod having a hollow strainer detachably attached to the tip into a casing,
And by rotating it in a certain direction and excavating it to position the strainer at the measurement point,
An appropriate gap of sand is formed between the lower end of the casing and the strainer portion, thereby preventing deposited particles from entering the strainer when the rod is removed and maintaining smooth water permeability. As a result, the accuracy of the measurement can be assured.

In addition, since the outer peripheral surface of the body of the strainer is surrounded by a porous filter, there is no alteration of the stratum due to the collapse of the borehole wall surface and clogging of the water hole of the strainer, and smooth inflow of groundwater into the strainer, Accurate measurements can be made possible.

Further, since a stopper groove having a stopper is formed at a base opening edge of the strainer, which is gradually tapered from the opening edge to a depth direction of the female screw portion, and has a stopper. The part does not screw into the female screw part of the strainer more than necessary,
Therefore, after the self-boring is completed, the rod can be easily removed when the rod is removed, and the workability is remarkably good.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a water permeability test method according to one embodiment of the present invention, FIG. 2 is an enlarged longitudinal sectional view of a strainer used in a water permeability test of the present invention, and FIG. 3 is a rod for the strainer. It is a principal part enlarged perspective view of the mounting part of FIG. DESCRIPTION OF SYMBOLS 1 ... Strainer, 2 ... Body 3 ... Water passage hole 4, Metal crown 5 ... Stopper groove, 6 ... Female thread part 7 ... Filter, 8 ... Rod 9 ... Male thread part, 10 ... water pipe 11 ... key, 12 ... casing

Claims (2)

(57) [Claims] 1. A step of boring to a depth immediately before a measuring point, a step of inserting a casing into the bore hole and driving the tip of the casing deeper than the bottom of the hole, and detachably attaching a hollow strainer to the tip. Loading the rod into the casing, and digging while rotating the rod in a certain direction to position the strainer at the measurement point, and removing the rod from the strainer by reversing the rod and determining the amount of water permeated into the casing. A permeability test method comprising a step of determining a permeability coefficient. 2. A permeation test apparatus in which a strainer is inserted into a casing driven into the bottom of a boring hole, and a permeability coefficient is obtained in a state where the strainer is excavated at a measurement position. A rod with a water pipe protruding at the tip can be detachably connected, a metal crown is attached to the opening edge of the tip, and a number of water holes are drilled at the trunk, and the outer peripheral surface is porous. Permeability test device surrounded by a filter.