JP7076100B2 - How to identify the stratum - Google Patents

Description

The present invention relates to a method for discriminating a stratum constituting the ground, particularly a method for discriminating whether the stratum is a gravel / sandy system or a silt / clay system.

Conventionally, a drilling machine is used to discriminate the formation layer, and the drilling data for each predetermined depth is water feed pressure, bit rotation torque, bit load, and the number of gear teeth in the bit rotation mechanism per unit depth. , Drilling speed, drilling depth, etc. have been proposed.

Japanese Unexamined Patent Publication No. 2002-133391

The present invention provides a stratum discrimination method that contributes to simpler stratum discrimination performed by using a drilling machine.

The present invention relates to a method for discriminating a formation, in which a hole is drilled in the ground while supplying water using a drilling machine, and the value of the pressure of the water at the bottom of the hole during the drilling is 0.2 to 1. Measuring at intervals of arbitrary values within the range of 0 seconds, the amplitudes of the multiple measurements of the water pressure are relatively large and the minimum and maximum values are approximately the same, which is why the said When a plurality of measured values change uniformly as a whole, it is determined that the formation including the hole bottom is a gravel / sandy system, and the amplitude of the plurality of measured values of the water pressure is relatively small. For this reason, when a plurality of measured values of the water pressure rise in a broken line shape as a whole, it includes determining that the formation including the hole bottom is a silt-clay system.

According to the present invention, by measuring the pressure value of the water at the bottom of the hole during drilling of the ground by supplying water, the stratum including the bottom of the hole is gravel / sandy or silt / clay. It is possible to determine whether it is a system, and thereby it is possible to more easily determine the stratum.

Further, by measuring the depth of the hole bottom at the time of measuring the pressure value of the water, it is possible to know the depth at which the determined stratum exists.

Further, when the average of a plurality of measured values of the water pressure at a predetermined depth is sequentially obtained from the ground to the deepest hole bottom, and the multiple averages change with relatively small and relatively small changes. The stratum may be of a gravel / sandy system, and the stratum may be of a silt / clay system when the plurality of averages change with relatively large and relatively large changes. The predetermined depth is, for example, 5 cm.

It is a graph which shows the measured value of the water pressure and the depth of the hole bottom when the drilling speed is relatively fast. It is a graph which shows the measured value of the water pressure and the depth of the hole bottom when the drilling speed is relatively slow. It is a graph which shows the average of the measured value of the water pressure of the hole bottom at a predetermined depth when the drilling speed is relatively fast. It is a graph which shows the average of the measured value of the water pressure of the hole bottom at a predetermined depth when the drilling speed is relatively slow.

The present invention provides a discriminating method for discriminating whether the stratum constituting the ground is a gravel / sandy system or a silt / clay system.

In order to carry out this discrimination method, a drilling machine (not shown) is used to drill holes in the ground while supplying water.

As the drilling machine, for example, a rotary percussion type drilling machine used for carrying out the ground anchor method can be used. The rotary percussion type drilling machine comprises a casing having a bit at the tip thereof and water directly sent to the tip of the casing with or without a water pipe, or the casing and the water pipe. It is equipped with a water pump that sends water to the tip of the double pipe. The diameter of the casing can be arbitrarily selected.

The drilling of the ground is performed by applying a rotational force and a propulsive force to the casing directed vertically downward or diagonally downward, and digging the ground with a bit at the tip. The digging speed (drilling speed) of the ground can be arbitrarily determined. During the digging of the ground, the water pump is operated to supply water toward the bottom of the hole being dug (hole bottom). The water supply pressure and the water supply amount can be arbitrarily determined. The excavated earth and sand, together with the supplied water, rise from the bottom of the hole around the casing and are sent to the ground.

During drilling, the value of the water pressure (water pressure) at the bottom of the hole is measured at predetermined time intervals. A pressure sensor is incorporated in the water pipe or the casing for measuring the water pressure. In addition, the depth of the hole bottom is also measured when the water pressure is measured. The depth of the hole bottom is determined by detecting the digging distance (drilling distance) of the casing into the ground.

In FIGS. 1 and 2, two grounds different from each other are continuously dug down and continuously supplied with water at a high drilling speed and a slower drilling speed, respectively, and have a depth of 1,500 mm from a predetermined point. The measured value of the water pressure at the hole bottom and the measured value of the depth of the hole bottom when the hole is drilled to the depth of is shown. The measurement interval of the water pressure and the depth of the hole bottom is, for example, 0.2 seconds. The measurement interval can be any value within the range of 0.2 to 1.0 second. In the figure, the vertical axis and the horizontal axis show the water pressure (MPa) and the depth (mm), respectively.

With reference to FIG. 1, two graphs 10 and 12 are shown. These graphs 10 and 12 show the measured values of the water pressure at the depths of the plurality of hole bottoms measured every 0.2 seconds until the drilling distance reaches 1,500 mm.

Graph 10 is composed of a plurality of line segments extending in the vertical axis direction and forming columns in the horizontal axis direction. Amplitude is seen in the values of these line segments in the vertical direction, but the minimum and maximum values are almost the same (about 0.2 MPa and about 1.0 MPa). From this, it can be said that the plurality of measured values of the water pressure change uniformly as a whole. This is because the excavated earth and sand are clogged at the tip of the casing as the ground is dug down, so that the water pressure rises once (about 1.0 MPa), and immediately after that, water passes through the excavated earth and sand. It is considered that the water pressure decreased rapidly (about 0.2 MPa).

From this, it is determined that Graph 10 relates to a gravel / sandy stratum having a property of being relatively easy for water to pass through. In Graph 10, there are line segments 14, 16 and 18 having three local peak values (about 3.0 MPa). Further, the intervals between the vertical lines are not even, and are narrow at one depth and wide at another depth. It is considered that these phenomena are caused by the influence of other non-permeable stratum components, impurities, etc., which are different from the main components constituting the stratum, and can be treated as slight noise. ..

On the other hand, the graph 12 shows a line shape as a whole and rises. Unlike Graph 10, the amplitude is very small. It is considered that this is because the excavated earth and sand are temporarily clogged in the tip of the casing as the ground is dug down, but the water passes through the excavated earth and sand with the passage of time, not immediately. From this, it is determined that Graph 12 shows a silt-clay layer having a property of being relatively difficult for water to pass through.

Next, referring to FIG. 2, FIG. 2 shows two graphs 20 and 22 corresponding to the two graphs 10 and 12 of FIG. 1, respectively. The description of both graphs 10 and 12 shown in FIG. 1 also applies to both graphs 20 and 22 shown in FIG. 2, respectively, and both graphs 20 and 22 are gravel / sandy strata and silt / clayey, respectively. It is judged that it indicates the stratum of.

In FIG. 2, the minimum value and the maximum value of the water pressure in the graph 20 are 0.4 MPa and 2.0 MPa, respectively. In addition, two line segments 24 and 26 having a local peak value (about 6.0 MPa) were observed. Further, the graph 22 is bent and stretched between about 3.0 and 4.7 MPa. It is probable that the difference between the measured values of these pressures and those in Graphs 10 and 12 of FIG. 1 was caused by the decrease in the drilling speed.

The validity of the determination that the strata in the two different grounds are composed of the gravel / sandy system and the silt / clay system, respectively, is obtained by sampling the two grounds by boring survey. confirmed.

The validity of the determination of the stratum performed by the measurement of the water pressure can also be confirmed by performing the following processing on the measured value of the water pressure (see FIGS. 3 and 4). The treatment is to sequentially obtain the average of a plurality of measured values of the water pressure at a predetermined depth, for example, every 5 cm, from the ground to the deepest hole bottom (1,500 mm in the above example), that is, a thickness of 5 cm of the stratum. For each layer portion of the water pressure, the average of a plurality of measured values of the water pressure is calculated.

In FIG. 3, a plurality of averages of a plurality of measured values of the water pressure at a depth of 5 cm when the drilling speed is high and when the drilling speed is slow are represented by ○ and ●, respectively, and these transitions are represented by circles and ●, respectively. It is represented by broken lines 28 and 30. Here, the plurality of averages are all relatively low between 0 and 1.0 MPa, and the degree of change in the transition is relatively small. This indicates that each layer portion is composed of a gravel / sandy system having a property of easily allowing water to pass through, and therefore the stratum composed of a plurality of layer portions is also a gravel / sandy system.

Further, in FIG. 4, a plurality of averages of a plurality of measured values of the water pressure at a depth of 5 cm when the drilling speed is high and when the drilling speed is slow are represented by □ and ■, respectively, and their transitions. Are represented by polygonal lines 32 and 34, respectively. Here, the plurality of averages are relatively high between 0.2 and 2.0 megapascals and between 2.8 and 4.8 MPa, respectively, and change with relatively large changes and increases. There is. This suggests that each layer portion is composed of a silt-clay type having a property of being difficult for water to pass through, and therefore the stratum composed of a plurality of layer portions is also a silt-clay type.

10, 12 Graphs 14, 16, 18 Line segments that take local peak values 20, 22 Graphs 24, 26 Line segments that take local peak values 28, 30 Line segments 32, 34 Line segments 32, 34 Line segments

Claims (4)

Drilling the ground while supplying water using a drilling machine,
Measuring the value of the water pressure at the bottom of the hole during drilling at intervals of any value within the range of 0.2 to 1.0 seconds .
When the amplitudes of the plurality of measured values of the water pressure are relatively large and the minimum and maximum values are almost the same, and therefore the plurality of measured values change uniformly as a whole, the hole bottom is used. It is determined that the contained layer is a gravel / sandy system, and the amplitude of the multiple measurements of the water pressure is relatively small, so that the multiple measurements of the water pressure are generally broken lines. A method for discriminating a stratum including determining that the stratum including the bottom of the hole is a silt-clay type when it rises. The method for determining a stratum according to claim 1, which comprises measuring the depth of the bottom of the hole when measuring the value of the pressure of water. Further, to obtain a plurality of averages of a plurality of measured values of the water pressure at a predetermined depth sequentially from the ground to the deepest hole bottom.
When the plurality of averages change with relatively small and relatively small changes, the stratum is considered to be a gravel / sandy system, and the plurality of averages change with relatively large and relatively large changes. The method for discriminating a stratum according to claim 1 or 2 , wherein the stratum is a silt-clay system. The method for determining a stratum according to claim 3 , wherein the predetermined depth is 5 cm.

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