JP2016011489A - Soil investigation method and soil investigation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil investigation method that enables liquefiability of soil to be inexpensively and simply identified even on an especially small-scale building site, and a soil investigation apparatus for use in the same.SOLUTION: A static penetration amount is measured for ground as an investigation object by using Swedish sounding test equipment, and a dynamic penetration amount is measured by applying striking force to a rod of the Swedish sounding test equipment. The presence or absence of possibility of liquefaction of the ground during earthquakes is identified from a difference between static penetration resistance and dynamic penetration resistance, which is obtained by the static penetration amount and the dynamic penetration amount.

Description

  The present invention relates to a ground survey method and a ground survey device for simply identifying the possibility of liquefaction of ground during an earthquake.

  When constructing large-scale civil engineering and building structures, it is important to grasp the mechanical characteristics of the ground in the planned construction site and to implement appropriate structure design based on this. For this reason, conventionally, for example, by using a dynamic penetration test using a standard penetration test method (JIS A 1219) defined in Japanese Industrial Standards, it is necessary to know the relative values of the hardness and tightness of soil in the original position. N value is measured.

  In this test method, as seen in the following Patent Document 1, after drilling the ground to be investigated by core boring, a standard penetration test sampler is attached to the tip of the rod and lowered to the drilled boring hole bottom, The rod is hit by the free fall of the hammer on the ground, and the number of hits (N value) required to penetrate a predetermined depth from the hole bottom is obtained.

  On the other hand, the damage caused by liquefaction of the ground also occurred in ordinary detached houses in the Tohoku Earthquake in the previous earthquake. There is a growing demand for a mandatory investigation into the possibility of aging.

Japanese Patent Laid-Open No. 9-242459

  However, the conventional standard penetration test method described above requires a boring machine and a boring pump for drilling the test hole, and the rod and its supporting device are large in size and complicated in structure. Because of the high cost of surveys, it is far from realistic to use for surveys in small residential areas.

  The present invention has been made in view of the above circumstances, and in particular, a ground investigation method capable of easily identifying the possibility of ground liquefaction at a low cost even for a small-scale residential land and the like. It is an object to provide a ground survey device to be used.

  In order to solve the above-mentioned problem, the ground survey method according to the present invention described in claim 1 measures the static penetration amount using a Swedish sounding test apparatus for the ground to be surveyed, and The dynamic penetration amount was measured by applying striking force to the rod of the type sounding test equipment, and the possibility of liquefaction during the earthquake of the above ground was determined from the difference between the static penetration resistance and the dynamic penetration resistance obtained by these. It is characterized by identifying presence or absence.

  The invention according to claim 2 is the invention according to claim 1, wherein the depth direction of the ground is divided into a plurality of sections, and the static penetration amount and the dynamic penetration amount for each of the sections. By measuring the above, the depth section having the possibility of liquefaction is identified.

Furthermore, in the invention described in claim 3, in the invention described in claim 2, while calculating the half rotation speed N _SW (SWS) of the rod required for the penetration amount of 1 m from the static penetration amount, From the dynamic penetration amount, the half rotation speed N _SW (DWS) of the rod required for the penetration amount of 1 m is calculated, and the value of ΔN _SW = {N _SW (SWS) −N _SW (DWS)} is It is characterized in that the section that has become positive is determined as a depth section that has the possibility of liquefaction.

  Next, in the ground surveying device according to the present invention as set forth in claim 4, the Swedish sounding test device is detachably incorporated with a vibrator for giving an impact force in the axial direction to the rod of the Swedish sounding test device. It is characterized by.

  In the invention according to any one of claims 1 to 4, the Swedish sounding test device is a test device defined in Japanese Industrial Standard (JIS) A 1221 “Swedish Sounding Test Method”.

Conventionally, in small residential land where detached houses are built, penetration by load and rotation are carried out by the test method using Swedish sounding test equipment at the corners of the site before construction. The static penetration resistance (W _SW , N _a , N _SW ) of the ground specified in Japanese Industrial Standards (JIS) A 1221 is measured and calculated, and the hardness or softness of the ground is determined by the obtained value. It is widely performed to determine.

  Therefore, according to the ground survey method according to any one of claims 1 to 3 using the ground survey device according to claim 4, the static penetration amount measurement using the conventional Swedish sounding test method is performed. In addition, the dynamic penetration is measured by applying striking force to the rod of the Swedish sounding test equipment, and the ground can be liquefied during the earthquake from the difference between the static penetration and dynamic penetration. By identifying the presence or absence of sexuality, the possibility of ground liquefaction can be easily identified at a low cost even for a small residential land.

  At this time, as in the invention described in claim 2, by dividing the depth direction of the ground into a plurality of sections and measuring the static penetration amount and the dynamic penetration amount for each section, It is preferable to identify a depth section (soil layer section) that may be liquefied.

In general, in the soil having a high possibility of liquefaction, the dynamic penetration amount with the impact applied to the rod is larger than the static penetration amount for the same load. The penetration resistance N _SW, after stopped penetration under a load of 1000 N, the half rotational speed N _a time that has penetrated to 0.25m by rotating, is a representation in a half revolutions per penetration amount 1m .

Therefore, in the soil having a high possibility of liquefaction, the half rotation speed N _SW (DWS) obtained from the dynamic penetration amount is higher than the half rotation speed N _SW (SWS) obtained from the static penetration amount. Is smaller.

Therefore, as in the third aspect of the invention, the half rotation number N _SW (SWS) is calculated from the static penetration amount, and the half rotation number N _SW (DWS) is calculated from the dynamic penetration amount. The difference ΔN _SW = {the above N _SW (SWS) −the above N _SW (DWS)} value is determined to be a depth range where liquefaction can be easily performed by determining the interval where the value is positive. Possibility can be easily identified.

It is a front view which shows one Embodiment of the ground investigation apparatus which concerns on this invention. It is a flowchart for demonstrating one Embodiment of the ground investigation method which concerns on this invention. It is a figure which shows the result obtained by the ground investigation method of FIG. 2, (a) is a graph which shows _NSW value calculated from the static penetration amount and dynamic penetration amount in each depth division, (b) is both N It is a graph which shows the value of the difference of _SW value.

FIG. 1 shows an embodiment of a ground investigation apparatus according to the present invention. This ground investigation apparatus is schematically configured by detachably incorporating a vibrator 2 in a Swedish sounding test apparatus 1. is there.
Here, the Swedish sounding test apparatus 1 includes a rod 3, a screw point 4 attached to the tip of the rod 3, a loading clamp 5 fixed to the upper part of the rod 3, and the loading clamp 5. This is a well-known test apparatus comprising a weight 6 to be placed and a handle 7 provided at the upper end of the rod 3 for rotating the rod 3 about its axis.

  Here, a plurality of weights 6 are loaded on the loading clamp 5 in a stepwise manner according to the Swedish sounding test method so that the loads are 50N, 150N, 250N, 500N and 1000N. As the screw point 4 is penetrated into the soil, the rods 3 are successively added in accordance with the increase.

  And the said electric exciter 2 is provided in the upper end part of this rod 3 so that attachment or detachment is possible. The vibrator 2 continuously applies a striking force in the axial direction of the rod 3, and in the present embodiment, a generator 8 for operating the vibrator 2 is disposed. The vibrator 2 may be a battery-driven one instead of the generator 8, or a one driven by compressed air.

Next, based on FIG. 2 and FIG. 3, the ground investigation method according to the present invention can be liquefied with respect to the ground of a small residential land for constructing a detached house, using the ground investigation device having the above-described configuration. One embodiment applied when investigating the property will be described.
First, before building, the corners in the site are penetrated by load and rotated by the test method using Swedish sounding test equipment 1, and are defined in Japanese Industrial Standard (JIS) A 1221. Measure and calculate the static penetration resistance N _SW (SWS) of the ground.

At this time, the depth direction of the ground is divided into a plurality of sections (in this embodiment, every 0.25 m as shown in FIG. 3), and the static penetration amount is measured for each of the sections, and 1 m Measure and calculate the half rotation speed N _SW (SWS) of the rod required for the amount of penetration.

Next, the vibration generator 2 is attached to the Swedish sounding test apparatus 1, and a striking force is applied to the rod 3 from the vibration generator 2 in the vicinity of the place where the static penetration test is performed or in the center of the residential land. Then, the half penetration number N _SW (DWS) of the rod 3 required for the penetration amount of 1 m is calculated in the same manner from the obtained dynamic penetration amount.

Then, the difference ΔN _SW = {N _SW (SWS) −N _SW (DWS)} is calculated from these N _SW (SWS) and N _SW (DWS), and the section where the value becomes positive is calculated. Judged as a possible depth section.

As described above, according to the ground survey method having the above-described configuration, in addition to the static penetration test using the Swedish sounding test apparatus 1 that has been conventionally performed, the Swedish sounding test apparatus 1 includes a vibrator. A dynamic penetration test using a ground survey device equipped with 2 was carried out, and the difference between the half rotation speed N _SW (SWS) and N _SW (DWS) of the rod 3 required for the penetration amount of 1 m obtained by these Since ΔN _SW identifies the possibility of liquefaction during the earthquake of the ground, the possibility of ground liquefaction can be easily identified at low cost even for small-scale residential land. be able to.

1 Swedish Sounding Tester 2 Vibrator 3 Rod 4 Screw Point 6 Weight

Claims (4)

  In addition to measuring the static penetration of the ground to be investigated using a Swedish sounding test device, the striking force is applied to the rod of the Swedish sounding test device, and the dynamic penetration is measured. A ground survey method characterized by identifying the possibility of liquefaction during the earthquake of the ground from the difference between the obtained static penetration resistance and dynamic penetration resistance.   Dividing the depth direction of the ground into a plurality of sections, and measuring the static penetration amount and the dynamic penetration amount for each of the sections, to identify the depth section having the possibility of liquefaction. The ground investigation method according to claim 1, wherein: The rod half rotation number N _SW (SWS) required for the 1 m penetration amount is calculated from the static penetration amount, and the rod half rotation number required for the 1 m penetration amount from the dynamic penetration amount. N _SW (DWS) is calculated, and the section where the value of ΔN _SW = {the N _SW (SWS) −the N _SW (DWS)} is positive is determined as the depth section where the liquefaction may occur. The ground investigation method according to claim 2 characterized by things.   A ground surveying device characterized in that a swivel that gives a striking force in the axial direction to a rod of the Swedish sounding test device is detachably incorporated in the Swedish sounding test device.