JP6281148B2

JP6281148B2 - Permeability test apparatus and permeability test method

Info

Publication number: JP6281148B2
Application number: JP2013193946A
Authority: JP
Inventors: 田中　克彦; 克彦田中; 良一深川; 将光藤本; 伸隆平岡; 雄大黒原
Original assignee: Ritsumeikan Trust
Current assignee: Ritsumeikan Trust
Priority date: 2013-09-19
Filing date: 2013-09-19
Publication date: 2018-02-21
Anticipated expiration: 2033-09-19
Also published as: JP2015059346A

Description

本発明は、地盤の透水係数を測定するための透水試験装置及び透水試験方法に関する。 The present invention relates to a permeability test apparatus and a permeability test method for measuring the permeability coefficient of the ground.

降雨による斜面崩壊を予測する上で、その地盤の透水係数を把握しておくことは重要である。現場で地盤の透水係数を測定する方法としては、ピエゾメータ法やチューブ法等が知られている。ピエゾメータ法は、図８（ａ）に示すように、土中に埋設した測定用パイプ１０１の先端に試験区間１０２を確保するための孔壁１０３を設けて計測を行う方法であり、チューブ法は、図８（ｂ）に示すように、測定用パイプ１０１の先端を孔底として計測を行う方法である。両者は、透水係数を求める算出式が若干異なるが、いずれも測定用パイプ１０１内に水位の変化を測定するための水位計１０４を備えている。 In predicting slope failure due to rainfall, it is important to understand the hydraulic conductivity of the ground. As a method for measuring the hydraulic conductivity of the ground at the site, a piezometer method, a tube method, and the like are known. As shown in FIG. 8A, the piezometer method is a method in which measurement is performed by providing a hole wall 103 for securing the test section 102 at the tip of the measurement pipe 101 embedded in the soil. As shown in FIG. 8 (b), the measurement is performed using the tip of the measurement pipe 101 as the hole bottom. Both of them have slightly different calculation formulas for determining the water permeability coefficient, but each has a water level meter 104 for measuring a change in the water level in the measurement pipe 101.

また、透水試験方法の種類としては、非定常法や定常法と呼ばれるものがある（例えば、非特許文献１参照）。現場透水試験の一般的な方法である非定常法によるピエゾメータ法では、例えば、図９（ａ）に示すように、測定対象とする地点をボーリングして試験孔を設け、この試験孔に測定用パイプ１０１を設置し、その先端に試験区間１０２を設ける。測定用パイプ１０１内には、水位測定用のフロート式の水位計１０４が設置される。そして、測定用パイプ１０１内に水を投入して一時的に測定パイプ１０１内の水位を上昇させるか、または測定用パイプ１０１内の水を汲み上げて一時的に測定用パイプ１０１内の水位を低下させる。その後、測定用パイプ１０１内の水位が平衡状態に戻る過程における水位の経時変化を水位計１０４によって測定することにより透水係数を求める。このような非定常法による透水試験方法は、透水係数が１０^−４ｍ／ｓ程度以下の比較的透水係数が小さい場合に有効である。 In addition, as a kind of the water permeability test method, there is a method called an unsteady method or a steady method (for example, see Non-Patent Document 1). In the piezometer method based on the unsteady method, which is a general method for in-situ permeability tests, for example, as shown in FIG. 9A, a test hole is bored to provide a test hole, and the test hole is used for measurement. A pipe 101 is installed, and a test section 102 is provided at the tip thereof. In the measurement pipe 101, a float type water level gauge 104 for measuring the water level is installed. Then, water is poured into the measurement pipe 101 to temporarily raise the water level in the measurement pipe 101, or the water in the measurement pipe 101 is temporarily pumped to temporarily lower the water level in the measurement pipe 101. Let Then, the water permeability coefficient is obtained by measuring the time change of the water level in the process of returning the water level in the measurement pipe 101 to the equilibrium state by the water level meter 104. Such a non-stationary water permeability test method is effective when the water permeability coefficient is relatively small, such as about 10 ⁻⁴ m / s or less.

一方、定常法によるピエゾメータ法では、例えば、図９（ｂ）に示すように、ポンプ１０５等を用いて測定用パイプ１０１内から揚水、または測定用パイプ１０１内に注水して測定用パイプ１０１内の水位が一定になったときの揚水流量または注水流量を流量計１０６等により測定して透水係数を求める。このような定常法による透水試験方法は、透水係数が１０^−４ｍ／ｓ程度以上に大きい場合に有効である。 On the other hand, in the piezometer method by the steady method, for example, as shown in FIG. 9B, pumping water or the like is injected into the measurement pipe 101 using the pump 105 or the like, and the measurement pipe 101 is filled with water. The pumping flow rate or the water injection flow rate when the water level of the water becomes constant is measured by the flow meter 106 or the like to obtain the hydraulic conductivity. Such a permeability test method by a steady method is effective when the permeability coefficient is as large as about 10 ⁻⁴ m / s or more.

また、従来、例えば川面の水位を計測する場合に、川面の上方に超音波送受信兼用トランスデューサを設置して、そのトランスデューサから送信された超音波が川面で反射してトランスデューサに戻ってくるまでの往復の伝播時間を計測することにより川面の水位を求めることが行われている。これと同様の原理で超音波を用いて、透水係数を求める方法として、例えば、測定用パイプとマリオット水槽を併用して測定する定水位測定法が開示されている（例えば、特許文献１参照）。この特許文献１では、マリオット水槽内の水位の変化をマリオット水槽の上方に設置された超音波水位計で測定することにより透水係数を求めている。 Conventionally, for example, when measuring the water level of a river surface, an ultrasonic transmission / reception transducer is installed above the river surface, and the ultrasonic wave transmitted from the transducer is reflected on the river surface and returned to the transducer. The water level of the river surface is calculated by measuring the propagation time of the river. As a method for obtaining a hydraulic conductivity using ultrasonic waves based on the same principle as this, for example, a constant water level measurement method is disclosed in which measurement is performed using a measurement pipe and a Marriott water tank (see, for example, Patent Document 1). . In this patent document 1, the permeability coefficient is calculated | required by measuring the change of the water level in a Marriott water tank with the ultrasonic water level meter installed above the Marriott water tank.

特開２００２−３６５２０１号公報JP 2002-365201 A

地盤工学会基準部、「資料「JGS 1314:ボーリング孔を利用した透水試験方法」,「JGS 1315:揚水試験方法」,「JGS 1321:湧水圧による岩盤の透水試験方法」,「JGS 1322:定圧注水による岩盤の透水試験方法」の改正案について」、土と基礎：地盤工学会誌／地盤工学会「土と基礎」編集委員会編、ｐｐ．９５、２００２年１２月Geotechnical Society Standards Department, “JGS 1314: Permeability test method using borehole”, “JGS 1315: Pumping test method”, “JGS 1321: Permeability test method of rock mass by spring pressure”, “JGS 1322: Constant pressure “Revised Proposal of Permeability Test Method for Rock Mass by Water Injection”, Soil and Foundation: Geotechnical Society Journal / Soil and Foundation “Soil and Foundation” Editorial Committee, pp. 95, December 2002

しかしながら、非特許文献１のように、従来の測定用パイプを用いた非定常法や定常法による透水試験方法では、測定用パイプ内の水位計測にはｍｍの精度が要求され、簡便にはフロート式水位計が用いられているが、測定用パイプ内の水位を正確に測定するためには、測定用パイプが振動したり、あるいは鉛直方向から傾斜した状態で設置されたような場合でも、水位計が測定用パイプの内壁に接触しないように配慮することが重要であり、そのためには測定用パイプの内径を十分に大きくしておく必要がある。それゆえ、一般的には測定用パイプの外径は、５０ｍｍ以上の太さになっている。従って、測定用パイプを設置する際、大きな径の試験孔を掘削する必要があり、測定用パイプの設置作業に手間が掛かるため、面倒である。 However, as described in Non-Patent Document 1, in the conventional non-stationary method using a measurement pipe or the water permeability test method by the steady method, the water level measurement in the measurement pipe requires mm accuracy, and it is easy to float. In order to accurately measure the water level in the measuring pipe, the water level is measured even when the measuring pipe vibrates or is tilted from the vertical direction. It is important to make sure that the meter does not come into contact with the inner wall of the measurement pipe. To that end, the inner diameter of the measurement pipe must be sufficiently large. Therefore, in general, the outer diameter of the measurement pipe is 50 mm or more. Therefore, when installing the measurement pipe, it is necessary to excavate a test hole having a large diameter, which is troublesome because it takes time to install the measurement pipe.

また、特許文献１のように、超音波を用いて水位を計測する場合、超音波はトランスデューサの前面からある程度の広がりを持って開放空間内の前方に放射されるので、超音波伝播軸を中心とする周囲に伝播を乱さない程度の十分な広さの開放空間を必要とする。そのため、マリオット水槽は、その内壁における超音波の反射、散乱の影響が少なくなるように十分大きな内径（特許文献１ではマリオット水槽の内径が９ｃｍ）に設定される必要があるので、装置が大型化してしまう。また、測定用パイプ内の水量変化をマリオット水槽の水位変化でもってｍｍオーダーで精度良く測定するためには、マリオット水槽の内径に対して測定用パイプの内径を数倍大きくすることが望ましく、特許文献１では内径が２０ｃｍに設計されている。つまり、特許文献１のように超音波水位計を用いた場合でも、測定用パイプの内径を小さくすることは困難であり、測定用パイプを設置する際、大きな径の試験孔を掘削する必要があるため、測定用パイプの設置作業が面倒である。 Further, as in Patent Document 1, when the water level is measured using ultrasonic waves, the ultrasonic waves are radiated forward from the front surface of the transducer with a certain extent, so that the ultrasonic propagation axis is the center. An open space that is large enough not to disturb the propagation is required. Therefore, the Marriott aquarium needs to be set to a sufficiently large inner diameter (in Patent Document 1, the inner diameter of the Marriott aquarium is 9 cm) so that the influence of reflection and scattering of ultrasonic waves on the inner wall is reduced. End up. In addition, in order to accurately measure the change in the amount of water in the measurement pipe with the water level change in the Marriott aquarium in mm order, it is desirable to make the inner diameter of the measurement pipe several times larger than the inner diameter of the Marriott aquarium. In Document 1, the inner diameter is designed to be 20 cm. That is, even when an ultrasonic water level gauge is used as in Patent Document 1, it is difficult to reduce the inner diameter of the measurement pipe, and when installing the measurement pipe, it is necessary to drill a test hole having a large diameter. Therefore, the installation work of the measuring pipe is troublesome.

本発明は、上記のような課題に鑑みてなされたものであって、中空の超音波導波管内に超音波を閉じ込めて伝播させることにより、装置を小型化して、容易に設置作業を行うことができる透水試験装置及び透水試験方法を提供することを目的とする。 The present invention has been made in view of the problems as described above, and by confining and propagating ultrasonic waves in a hollow ultrasonic waveguide, the apparatus can be reduced in size and installed easily. An object of the present invention is to provide a water permeability test apparatus and a water permeability test method.

上記目的を達成するために、本発明に係る透水試験装置は、一端が密封され、他端が開口された管状の中空部材であって、地盤に掘削された試験孔に開口端側を下側にして挿入され、内部に水が貯留される超音波導波管と、前記超音波導波管の密封端側の内部に設けられ、前記開口端側に向けて超音波を送信する超音波送信素子と、前記超音波導波管の密封端側の内部に設けられ、前記超音波送信素子から送信された前記超音波が前記音波導波管内の水面で反射して戻ってくる反射波を受信する超音波受信素子と、を有する超音波検出器と、前記超音波送信素子が前記超音波を送信してから前記超音波受信素子が前記反射波を受信するまでに要する伝播時間に基づいて前記超音波導波管内の水位を経時的に計測することにより前記地盤の透水係数を求める演算手段と、を備え、前記超音波導波管は、その内径が前記超音波送信素子から送信される前記音波の波長の４倍以下であって、その外径が前記試験孔に嵌合する径を有し、さらに内部に水を注水または内部の水を汲水するための注水口を前記密封端側の側面に有することを特徴としている。
In order to achieve the above object, a water permeation test apparatus according to the present invention is a tubular hollow member that is sealed at one end and opened at the other end, and has an open end side below a test hole excavated in the ground. An ultrasonic wave guide that is inserted in the inside and stores water therein, and an ultrasonic wave transmission that is provided inside the sealed end side of the ultrasonic wave guide and that transmits the ultrasonic wave toward the open end side The ultrasonic wave transmitted from the ultrasonic wave transmitting element is reflected on the water surface in the ultrasonic wave waveguide and received by the reflected wave that is provided inside the element and the sealed end side of the ultrasonic wave waveguide. An ultrasonic detector comprising: an ultrasonic detector; and a transmission time required for the ultrasonic receiving element to receive the reflected wave after the ultrasonic transmitting element transmits the ultrasonic wave. The water permeability of the ground is measured by measuring the water level in the ultrasonic waveguide over time. Comprising calculating means for determining the number, the, the ultrasound waveguide, it der 4 times or less of the wavelength of the sound wave whose inner diameter is transmitted from the ultrasonic wave transmitting element, an outer diameter the test hole And a water inlet for pouring water inside or pumping water inside is provided on the side surface on the sealed end side .

また、本発明に係る透水試験装置は、前記超音波導波管が、現場の地盤に掘削された試験孔に挿入されるものであって、前記演算手段は、前記地盤の前記透水係数を求めた後、前記超音波受信素子が受信した前記反射波の最大振幅に基づいて前記超音波導波管の前記開口端付近の土中水分量を計測し、前記超音波送信素子が前記超音波を送信してから前記超音波受信素子が前記反射波を受信するまでに要する伝播時間に基づいて前記地盤の地下水位を計測することを特徴としている。 Further, in the water permeability test apparatus according to the present invention, the ultrasonic waveguide is inserted into a test hole excavated in the field ground, and the calculation means obtains the water permeability coefficient of the ground. After that, based on the maximum amplitude of the reflected wave received by the ultrasonic receiving element, the amount of moisture in the soil near the opening end of the ultrasonic waveguide is measured, and the ultrasonic transmitting element transmits the ultrasonic wave It is characterized in that the groundwater level of the ground is measured based on the propagation time required for the ultrasonic receiving element to receive the reflected wave after transmission.

また、本発明に係る透水試験装置は、前記超音波導波管内の水面に浮かべられる超音波反射体を備え、前記演算手段は、前記超音波送信素子が前記開口端側に向けて超音波を送信し、該超音波が前記超音波反射体で反射して戻ってくる反射波を前記超音波受信素子で受信するまでに要する伝播時間に基づいて前記超音波導波管内の水位を経時的に計測することにより前記地盤の透水係数を求めることを特徴としている。 Further, the water permeability test apparatus according to the present invention includes an ultrasonic reflector floated on a water surface in the ultrasonic waveguide, and the calculation means transmits the ultrasonic wave toward the opening end side of the ultrasonic transmission element. The water level in the ultrasonic waveguide is changed over time based on the propagation time required for transmission and reception of the reflected wave that is reflected by the ultrasonic reflector and returned by the ultrasonic receiver. It is characterized in that the permeability coefficient of the ground is obtained by measurement.

本発明に係る透水試験方法は、一端が密封され、他端が開口された管状の中空部材であって、内径が密封端側の内部に設けられる超音波送信素子から送信される超音波の波長の４倍以下であって、外径が地盤に掘削された試験孔に嵌合する径を有し、さらに内部に水を注水または内部の水を汲水するための注水口を前記密封端側の側面に有する超音波導波管を前記試験孔に開口端側を下側にして挿入した状態で内部に水を貯留し、前記超音波送信素子から前記開口端側に向けて前記超音波を送信し、前記超音波導波管の密封端側の内部に設けられた超音波受信素子により前記超音波送信素子から送信された前記超音波が前記超音波導波管内の水面で反射して戻ってくる反射波を受信し、前記超音波送信素子が前記超音波を送信してから前記超音波受信素子が前記反射波を受信するまでに要する伝播時間に基づいて前記超音波導波管内の水位を経時的に計測することにより前記地盤の透水係数を求めることを特徴としている。 The water permeability test method according to the present invention is a tubular hollow member having one end sealed and the other end opened, and the wavelength of ultrasonic waves transmitted from an ultrasonic transmission element provided inside the sealed end side. four times I der hereinafter has a diameter whose outer diameter fits into the test hole drilled in the ground, further the sealing end of the water injection port for Kap Shui water injection or the water inside the water therein water was stored inside the ultrasonic waveguide having a side surface side in a state where the opening end side to the test hole and inserted in the bottom, the said ultrasonic waves toward the ultrasonic transmitting element to said open end And the ultrasonic wave transmitted from the ultrasonic wave transmitting element is reflected by the water surface in the ultrasonic wave guide by the ultrasonic wave receiving element provided inside the sealed end of the ultrasonic wave waveguide. The reflected wave that is returned is received, and the ultrasonic transmission element transmits the ultrasonic wave, and then the ultrasonic wave is transmitted. Wave receiving element is characterized by determining the permeability coefficient of the ground by over time to measure the water level of the ultrasonic waveguide based on the propagation time required to receive the reflected wave.

また、本発明に係る透水試験方法は、前記超音波導管が、現場の地盤に掘削された試験孔に挿入されるものであって、前記地盤の透水係数を求めた後、前記超音波受信素子が受信した前記反射波の最大振幅に基づいて前記超音波導波管の前記開口端付近での土中水分量を計測し、前記超音波送信素子が前記超音波を送信してから前記超音波受信素子が前記反射波を受信するまでに要する伝播時間に基づいて前記地盤の地下水位を計測することを特徴としている。 Further, in the water permeability test method according to the present invention, the ultrasonic conduit is inserted into a test hole excavated on the ground in the field, and after obtaining the water permeability coefficient of the ground, the ultrasonic receiving element Measures the moisture content in the soil near the opening end of the ultrasonic waveguide based on the maximum amplitude of the reflected wave received by the ultrasonic wave, and transmits the ultrasonic wave after the ultrasonic transmission element transmits the ultrasonic wave. The groundwater level of the ground is measured based on the propagation time required for the receiving element to receive the reflected wave.

また、本発明に係る透水試験方法は、前記超音波導波管を前記試験孔に前記開口端側を下側にして内部に水が貯留するように挿入した後、前記超音波導波管内の水面に超音波反射体を浮かべて、前記超音波送信素子から前記開口端側に向けて前期超音波を送信し、前記超音波受信素子により前記超音波送信素子から送信された前記超音波が前記超音波反射体で反射して戻ってくる反射波を受信し、前記超音波送信素子が前記超音波を送信してから前記超音波受信素子が前記反射波を受信するまでに要する伝播時間に基づいて前記超音波導波管内の水位を経時的に計測することにより前記地盤の透水係数を求めることを特徴としている。 Further, in the water permeability test method according to the present invention, the ultrasonic waveguide is inserted into the test hole so that water is stored inside with the opening end side down, An ultrasonic reflector is floated on the water surface, the previous ultrasonic wave is transmitted from the ultrasonic transmission element toward the opening end side, and the ultrasonic wave transmitted from the ultrasonic transmission element by the ultrasonic reception element is Based on the propagation time required from the time when the ultrasonic wave is reflected by the ultrasonic reflector and the ultrasonic wave transmission element transmits the ultrasonic wave to the time when the ultrasonic wave reception element receives the reflected wave. The water permeability coefficient of the ground is obtained by measuring the water level in the ultrasonic waveguide over time.

本発明に係る透水試験装置及び透水試験方法によれば、内径が密封端側の内部に設けられた超音波送信素子から送信される超音波の波長の４倍以下である中空の超音波導波管の開口端側を下側にして地盤に掘削された試験孔に挿入し、超音波送信素子から送信された超音波が超音波導波管内の水面で反射して戻ってくる反射波を密封端側の内部に設けられた超音波受信素子で受信して、超音波導波管内の水位を計測することにより地盤の透水係数を求めている。このように、本発明に係る透水試験装置及び透水試験方法では、超音波を中空の超音波導波管内に閉じ込めて伝播させるため、超音波導波管の内径及び外径を細く設定することができ、地盤に大きな径の試験孔を掘削しなくて済むので、地盤への設置作業を容易に行うことができる。また、超音波は拡散されることなく、超音波導波管内を有効に伝播するため、超音波送信素子から送信する超音波の送信電力を抑えることができるので、消費電力を軽減し、装置を小型化することができる。 According to the water permeation test apparatus and the water permeation test method according to the present invention, the hollow ultrasonic wave guide whose inner diameter is not more than four times the wavelength of the ultrasonic wave transmitted from the ultrasonic transmission element provided inside the sealed end side. Inserted into a test hole excavated in the ground with the open end side of the pipe facing down, the reflected wave returned from the ultrasonic wave transmitted from the ultrasonic transmission element is reflected by the water surface in the ultrasonic waveguide. It receives with the ultrasonic receiving element provided inside the end side, and measures the water level in the ultrasonic waveguide to obtain the water permeability coefficient of the ground. As described above, in the water permeability test apparatus and the water permeability test method according to the present invention, since the ultrasonic waves are confined and propagated in the hollow ultrasonic wave guide, the inner diameter and the outer diameter of the ultrasonic wave guide can be set thin. In addition, since it is not necessary to excavate a test hole having a large diameter in the ground, the installation work on the ground can be easily performed. In addition, since the ultrasonic wave propagates effectively in the ultrasonic waveguide without being diffused, the transmission power of the ultrasonic wave transmitted from the ultrasonic transmission element can be suppressed. It can be downsized.

また、超音波導波管の径を細く設定することができるので、地中の深い地点まで挿入することが容易であり、且つ、超音波が拡散されることなく、有効に深い地点まで伝播されるので、深い地点における透水係数の測定にも有効である。従って、現場で場所と深さを変えて地盤の透水係数の３次元分布を計測するような場合にも適している。 In addition, since the diameter of the ultrasonic waveguide can be set thin, it is easy to insert it to a deep point in the ground, and the ultrasonic wave is effectively propagated to a deep point without being diffused. Therefore, it is also effective for measuring permeability coefficient at deep points. Therefore, it is also suitable when measuring the three-dimensional distribution of hydraulic conductivity of the ground by changing the location and depth at the site.

また、本発明に係る透水試験装置及び透水試験方法によれば、地盤の透水係数を求めた後は、超音波受信素子が受信した反射波の最大振幅に基づいて超音波導波管の開口端付近での土中水分量を計測し、超音波送信素子が超音波を送信してから超音波受信素子が反射波を受信するまでに要する伝播時間に基づいて地盤の地下水位を計測する。従って、地盤の透水係数を求めた後も、超音波導波管をそのまま試験孔に挿入した状態にしておくことで、超音波導波管を透水係数の計測だけでなく、降雨による土中の水分・水位のモニタリングにも兼用することができるので、設備費や現場の設置費等を軽減することができ、非常に効率的である。 Further, according to the water permeability test apparatus and the water permeability test method according to the present invention, after obtaining the water permeability coefficient of the ground, the open end of the ultrasonic waveguide is based on the maximum amplitude of the reflected wave received by the ultrasonic wave receiving element. The amount of moisture in the soil in the vicinity is measured, and the groundwater level of the ground is measured based on the propagation time required from when the ultrasonic transmission element transmits the ultrasonic wave until the ultrasonic reception element receives the reflected wave. Therefore, after obtaining the hydraulic conductivity of the ground, the ultrasonic waveguide can be inserted into the test hole as it is. Since it can also be used for monitoring moisture and water level, it is possible to reduce equipment costs and installation costs at the site, which is very efficient.

また、本発明に係る透水試験装置及び透水試験方法によれば、超音波導波管内の水面に超音波反射体を浮かべ、超音波送信素子から送信された超音波が、超音波反射体で反射して戻ってくる反射波を超音波受信素子で受信して、超音波導波管内の水位を計測することにより地盤の透水係数を求めるので、弱い強度の超音波でも精度良く計測を行うことができる。 Further, according to the water permeability test apparatus and the water permeability test method according to the present invention, the ultrasonic reflector is floated on the water surface in the ultrasonic waveguide, and the ultrasonic wave transmitted from the ultrasonic transmission element is reflected by the ultrasonic reflector. The reflected wave that is returned is received by the ultrasonic receiving element, and the water permeability in the ultrasonic wave guide is measured to determine the hydraulic conductivity of the ground. Therefore, even weak ultrasonic waves can be accurately measured. it can.

本発明の実施形態に係る透水試験装置の一例を示す概略模式図である。It is a schematic diagram which shows an example of the water permeability test apparatus which concerns on embodiment of this invention. 透水試験装置を構成する超音波検出器の一例を示す概略縦断面図である。It is a schematic longitudinal cross-sectional view which shows an example of the ultrasonic detector which comprises a water permeability test apparatus. 透水試験装置を構成する測定器の構成の一例を示すブロック図である。It is a block diagram which shows an example of a structure of the measuring device which comprises a water permeability test apparatus. 経過時間と水位差との関係を示す片対数グラフである。It is a semi-logarithmic graph which shows the relationship between elapsed time and a water level difference. 本発明の実施形態に係る透水試験装置の他の一例を示す概略模式図である。It is a schematic diagram which shows another example of the water-permeable test apparatus which concerns on embodiment of this invention. チューブ法により透水係数を求める際の超音波検出器の設置について説明するための概略縦断面図である。It is a schematic longitudinal cross-sectional view for demonstrating installation of the ultrasonic detector at the time of calculating | requiring a hydraulic conductivity by the tube method. 透水試験装置を構成する超音波検出器の他の一例を示す概略縦断面図である。It is a schematic longitudinal cross-sectional view which shows another example of the ultrasonic detector which comprises a water permeability test apparatus. 従来の現場透水試験方法について説明するための概略模式図であって、（ａ）はピエゾメータ法を示しており、（ｂ）はチューブ法を示している。It is a schematic diagram for demonstrating the conventional on-site water permeability test method, Comprising: (a) has shown the piezometer method, (b) has shown the tube method. 従来の透水試験方法の種類について説明するための概略模式図であって、（ａ）は非定常法を示しており、（ｂ）は定常法を示している。It is a schematic diagram for demonstrating the kind of conventional water-permeable test method, (a) has shown the unsteady method, (b) has shown the steady method.

以下、本発明に係る透水試験装置１について、図面を参照しつつ説明する。本発明に係る透水試験装置１は、地盤２の透水係数を計測するためのものであって、図１及び図２に示すように、地盤２に掘削された試験孔３に挿入される超音波検出器４と、この超音波検出器４に電気的に接続される測定器５とを備えている。 Hereinafter, a water permeability test apparatus 1 according to the present invention will be described with reference to the drawings. The water permeability test apparatus 1 according to the present invention is for measuring the water permeability coefficient of the ground 2, and as shown in FIGS. 1 and 2, an ultrasonic wave inserted into a test hole 3 excavated in the ground 2. A detector 4 and a measuring device 5 electrically connected to the ultrasonic detector 4 are provided.

超音波検出器４は、図２に示すように、試験孔３に挿入される超音波導波管６と、超音波導波管６の下側に向けて超音波Ｕを送信する超音波送信素子及び該超音波送信素子から送信された超音波Ｕが超音波導波管６内の水面で反射して戻ってくる反射波Ｒを受信する超音波受信素子が一体構成された送受信兼用素子部７１を有する超音波トランスデューサ７と、を備えている。 As shown in FIG. 2, the ultrasonic detector 4 includes an ultrasonic wave waveguide 6 inserted into the test hole 3 and an ultrasonic wave transmission that transmits the ultrasonic wave U toward the lower side of the ultrasonic wave waveguide 6. A transmission / reception combined element unit in which an element and an ultrasonic wave receiving element that receives a reflected wave R that is reflected from a water surface in the ultrasonic wave guide 6 and returned from the ultrasonic wave transmitting element 6 are integrated. And an ultrasonic transducer 7 having 71.

超音波導波管６は、両端が開口された管状の中空部材であって、その一端側には開口を塞ぐように蓋部材８が取り付けられており、他端側は開口された状態になっている。この超音波導波管６は、内径が超音波トランスデューサ７から送信される超音波Ｕの波長の４倍以下になるよう設計されている。従って、周波数４０ｋＨｚ（空気中における波長が８．５ｍｍ）の超音波Ｕを超音波トランスデューサ７から送信するような場合には、内径が３４ｍｍ以下に設計されている超音波導波管６を用いれば良く、例えば、長さが３０ｃｍ〜２ｍ程度で、内径が略１８ｍｍ、外径が２２ｍｍの真ちゅう製のパイプ等を用いることができる。これにより、超音波Ｕを超音波導波管６内に閉じ込めて、効率良く伝播させることができる。また、超音波導波管６の内周面は滑らかに形成されており、内部を伝播する超音波がぶつかった時に散乱することなく、一定方向に反射しやすくなっている。尚、超音波導波管６の材質、断面形状、及び長さ等は、本実施形態に限定されるものではなく、透水係数を計測する地盤の深さ等に応じて適宜変更可能であり、少なくとも超音波トランスデューサ７から送信される超音波Ｕが超音波導波管６内を効率良く伝播できるように、内径が超音波Ｕの波長の４倍以下になるよう設計されていれば良い。 The ultrasonic waveguide 6 is a tubular hollow member having both ends opened. A lid member 8 is attached to one end of the ultrasonic waveguide 6 so as to close the opening, and the other end is opened. ing. The ultrasonic waveguide 6 is designed so that the inner diameter thereof is not more than four times the wavelength of the ultrasonic wave U transmitted from the ultrasonic transducer 7. Accordingly, when transmitting an ultrasonic wave U having a frequency of 40 kHz (wavelength in air of 8.5 mm) from the ultrasonic transducer 7, an ultrasonic waveguide 6 having an inner diameter of 34 mm or less is used. For example, a brass pipe having a length of about 30 cm to 2 m, an inner diameter of about 18 mm, and an outer diameter of 22 mm can be used. Thereby, the ultrasonic wave U can be confined in the ultrasonic wave guide 6 and propagated efficiently. Further, the inner peripheral surface of the ultrasonic waveguide 6 is formed smoothly, and is easily reflected in a certain direction without being scattered when an ultrasonic wave propagating through the inside collides. The material, cross-sectional shape, length, and the like of the ultrasonic waveguide 6 are not limited to the present embodiment, and can be appropriately changed according to the depth of the ground for measuring the hydraulic conductivity, It is sufficient that the inner diameter is designed to be 4 times or less the wavelength of the ultrasonic wave U so that at least the ultrasonic wave U transmitted from the ultrasonic transducer 7 can efficiently propagate in the ultrasonic wave guide 6.

また、超音波導波管６では、その一端側に超音波導波管６の内部の空気を外部へ排出するための空気排出孔６１と、超音波導波管６の内部に水を注水したり、超音波導波管６の内部の水を汲み上げたりするためのポンプのホース（不図示）等を挿通させることができる注水口６２とが形成されている。空気排出孔６１は、超音波導波管６の外部から内部へ向かって上向きに傾斜するように貫通形成されており、降雨時等に超音波導波管６の外部から雨水が内部に浸入し難くい形状になっている。尚、この空気排出孔６１は、超音波導波管６の周方向に沿って複数形成されていても良く、複数形成されている場合には、いずれかの空気排出孔６１に土等が詰まったような場合でも、他の空気排出孔６１から空気を排出することができる。 Further, in the ultrasonic waveguide 6, water is injected into the inside of the ultrasonic waveguide 6 and an air discharge hole 61 for discharging the air inside the ultrasonic waveguide 6 to the outside at one end side thereof. Or a water inlet 62 through which a pump hose (not shown) or the like for pumping water inside the ultrasonic waveguide 6 can be inserted. The air discharge hole 61 is formed so as to incline upward from the outside to the inside of the ultrasonic waveguide 6, and rainwater enters the inside from the outside of the ultrasonic waveguide 6 during rain or the like. It has a difficult shape. Note that a plurality of air discharge holes 61 may be formed along the circumferential direction of the ultrasonic waveguide 6. If a plurality of air discharge holes 61 are formed, one of the air discharge holes 61 is clogged with soil or the like. Even in such a case, air can be discharged from the other air discharge holes 61.

超音波導波管６の一端側に取り付けられる蓋部材８は、例えば、円板状の真ちゅう製の部材であって、その径は超音波導波管６の外径と同程度に形成されている。この蓋部材８には、その中心部を貫通して、超音波トランスデューサ７の配線７２が挿通可能な配線引き出し孔８１が形成されるとともに、その内側面を覆うようにアルミ板９が貼り付けられている。これにより、超音波導波管６の一端は、配線引き出し孔８１の存在に拘らず、アルミ板９によって密封された状態となっている。また、アルミ板９の下方には、ダンパー材１０を介して超音波トランスデューサ７が固定されている。 The lid member 8 attached to one end of the ultrasonic waveguide 6 is, for example, a disk-shaped brass member, and the diameter thereof is approximately the same as the outer diameter of the ultrasonic waveguide 6. Yes. The lid member 8 is formed with a wiring lead-out hole 81 through which the wiring 72 of the ultrasonic transducer 7 can be inserted, and an aluminum plate 9 is attached so as to cover the inner surface thereof. ing. As a result, one end of the ultrasonic waveguide 6 is sealed by the aluminum plate 9 regardless of the presence of the wiring lead hole 81. An ultrasonic transducer 7 is fixed below the aluminum plate 9 via a damper material 10.

超音波トランスデューサ７は、圧電効果によって電気信号と機械的振動とをエネルギー変換するデバイスであって、図２に示すように、超音波導波管６の密封端側の内部に設けられており、超音波の送信及び受信を行う送受信兼用素子部７１と、この送受信兼用素子部７１から引き出された配線７２とを有している。送受信兼用素子部７１は、詳しくは図示しないが、基板上に超音波送信と超音波受信とを兼用する素子が配置されたものであって、所定の周波数の電気信号を与えると、その周波数の超音波を超音波送信素子が出力する一方、所定の周波数の超音波を超音波受信素子が受信すると、その周波数の電気信号を出力するものである。このように構成される超音波トランスデューサ７は、図２に示すように、その送受信兼用素子部７１が、蓋部材８の内側面を覆うアルミ板９に対してダンパー材１０を介して固定されている。 The ultrasonic transducer 7 is a device that converts electrical signals and mechanical vibrations by the piezoelectric effect, and is provided inside the sealed end of the ultrasonic waveguide 6 as shown in FIG. The transmitter / receiver element portion 71 that transmits and receives ultrasonic waves and a wiring 72 drawn from the transmitter / receiver element portion 71 are provided. Although not shown in detail, the transmitting / receiving element unit 71 is an element in which an element for both ultrasonic transmission and ultrasonic reception is arranged on a substrate. When an electric signal having a predetermined frequency is given, While the ultrasonic transmission element outputs ultrasonic waves, when the ultrasonic reception element receives ultrasonic waves of a predetermined frequency, an electric signal of that frequency is output. As shown in FIG. 2, the ultrasonic transducer 7 configured in this way has its transmitting / receiving element portion 71 fixed to an aluminum plate 9 covering the inner surface of the lid member 8 via a damper material 10. Yes.

ダンパー材１０は、例えば、シリコーンゴム等からなるものであって、超音波トランスデューサ７の振動が超音波導波管６に伝達されるのを防止するとともに、超音波導波管６の振動が超音波トランスデューサ７に伝達されるのを防止するものである。また、送受信兼用素子部７１から伸びる配線７２は、ダンパー材１０とアルミ板９とを挿通され、蓋部材８の配線引き出し孔８１を通して超音波導波管６の外部へと引き出されている。尚、本実施形態の超音波検出器４では、超音波導波管６への取り付けスペース等を考慮して、超音波の送信機能と受信機能の両方を備えた１個の超音波トランスデューサ７を用いた例を示しているが、これに限定されるものではなく、例えば、超音波導波管６の内部における密封端側に、超音波送信素子のみが配置された送信専用の超音波トランスデューサと、超音波受信素子のみが配置された受信専用の超音波トランスデューサとをそれぞれ別々に並べて設けるように構成しても良い。 The damper material 10 is made of, for example, silicone rubber or the like, and prevents the vibration of the ultrasonic transducer 7 from being transmitted to the ultrasonic waveguide 6, and the vibration of the ultrasonic waveguide 6 is super high. It is prevented from being transmitted to the sonic transducer 7. Further, the wiring 72 extending from the transmitting / receiving element portion 71 is inserted through the damper material 10 and the aluminum plate 9, and is drawn out of the ultrasonic waveguide 6 through the wiring drawing hole 81 of the lid member 8. In the ultrasonic detector 4 of the present embodiment, a single ultrasonic transducer 7 having both an ultrasonic transmission function and a reception function is provided in consideration of an installation space to the ultrasonic waveguide 6 and the like. Although the example used is not limited to this, for example, a transmission-dedicated ultrasonic transducer in which only the ultrasonic transmission element is disposed on the sealed end side inside the ultrasonic waveguide 6 and Alternatively, a reception-dedicated ultrasonic transducer in which only the ultrasonic receiving element is arranged may be provided separately.

測定器５は、図１に示すように、超音波検出器４に電気的に接続されるものであって、コンピュータ等により構成されており、超音波トランスデューサ７の超音波送信素子が超音波Ｕを送信してから、超音波Ｕが超音波導波管６内の水面で反射して戻ってくる反射波Ｒを超音波トランスデューサ７の超音波受信素子で受信するまでに要する伝播時間に基づいて超音波導波管６内の水位を経時的に計測することにより地盤２の透水係数を求める演算手段としての機能を有するものである。測定器５は、図３に示すように、各部の動作を制御する制御部５１に対して、超音波送信回路５２と、超音波受信回路５３と、信号処理回路５４とがシステムバス５５を介して接続されている。 As shown in FIG. 1, the measuring device 5 is electrically connected to the ultrasonic detector 4 and is configured by a computer or the like. The ultrasonic transmitting element of the ultrasonic transducer 7 is an ultrasonic U Is transmitted based on the propagation time required for the ultrasonic wave U to be received by the ultrasonic wave receiving element of the ultrasonic transducer 7 after the ultrasonic wave U is reflected by the water surface in the ultrasonic wave guide 6 and returned. It has a function as a calculation means for obtaining the water permeability coefficient of the ground 2 by measuring the water level in the ultrasonic waveguide 6 over time. As shown in FIG. 3, the measuring instrument 5 includes an ultrasonic transmission circuit 52, an ultrasonic reception circuit 53, and a signal processing circuit 54 via a system bus 55 with respect to a control unit 51 that controls the operation of each unit. Connected.

超音波送信回路５２は、超音波トランスデューサ７に対して所定の周波数の電気信号を付与するものである。一方、超音波受信回路５３は、超音波トランスデューサ７から所定の周波数の電気信号を受け取って信号処理回路５４へ出力するものである。信号処理回路５４では、超音波受信回路５３から入力された電気信号に基づいて超音波導波管６内の水位を計測し、この水位を経時的に計測した結果に基づいて地盤の透水係数を求める。 The ultrasonic transmission circuit 52 applies an electrical signal having a predetermined frequency to the ultrasonic transducer 7. On the other hand, the ultrasonic receiving circuit 53 receives an electrical signal having a predetermined frequency from the ultrasonic transducer 7 and outputs it to the signal processing circuit 54. In the signal processing circuit 54, the water level in the ultrasonic waveguide 6 is measured based on the electrical signal input from the ultrasonic receiving circuit 53, and the water permeability coefficient of the ground is calculated based on the result of measuring the water level over time. Ask.

透水試験装置１では、超音波導波管６が開口端側を下側にして地盤２に予め掘削された試験孔３に挿入された状態で、超音波導波管６の注水口６２から内部に水を投入して、一時的に超音波導波管６内の水位を上昇させる。このように超音波導波管６の内部に水が貯留された状態で、制御部５１の制御を受けて、超音波送信回路５２から超音波検出器４の超音波トランスデューサ７に対して所定の周波数の電気信号が付与され、図２に示すように、所定の周波数の超音波Ｕが超音波導波管６の開口端側に向けて送信される。この超音波Ｕは、超音波導波管６の内部を開口端側に向かって伝播し、超音波導波管６内の水面にぶつかって反射される。この水面で反射して戻ってくる反射波Ｒは、超音波導波管６の内部を密封端側に向かって伝播し、超音波トランスデューサ７の送受信兼用素子部７１によって受信される。そして、超音波トランスデューサ７では、この受信した反射波Ｒに対応する所定周波数の電気信号を配線７２を介して測定器５へ出力する。 In the water permeability test apparatus 1, the ultrasonic waveguide 6 is inserted into the test hole 3 that has been excavated in the ground 2 in advance with the opening end side down, from the water inlet 62 of the ultrasonic waveguide 6 to the inside. The water level in the ultrasonic waveguide 6 is temporarily raised by adding water to the water. In a state where water is stored inside the ultrasonic waveguide 6 as described above, a predetermined amount is transmitted from the ultrasonic transmission circuit 52 to the ultrasonic transducer 7 of the ultrasonic detector 4 under the control of the control unit 51. An electrical signal having a frequency is applied, and an ultrasonic wave U having a predetermined frequency is transmitted toward the opening end side of the ultrasonic waveguide 6 as shown in FIG. The ultrasonic wave U propagates inside the ultrasonic waveguide 6 toward the opening end side, and hits the water surface in the ultrasonic waveguide 6 and is reflected. The reflected wave R reflected back from the water surface propagates inside the ultrasonic waveguide 6 toward the sealed end and is received by the transmitting / receiving element unit 71 of the ultrasonic transducer 7. Then, the ultrasonic transducer 7 outputs an electrical signal having a predetermined frequency corresponding to the received reflected wave R to the measuring device 5 via the wiring 72.

測定器５では、超音波受信回路５３がこの電気信号を受け取って信号処理回路５４へ出力する。信号処理回路５４では、制御部５１による制御の下、入力された電気信号に基づいて、超音波導波管６内の水位を計測する。より詳細には、信号処理回路５４では、超音波トランスデューサ７の超音波送信素子が超音波Ｕを送信してから、超音波Ｕが超音波導波管６内の水面で反射して戻ってくる反射波Ｒを超音波トランスデューサ７の超音波受信素子で受信するまでに要する伝播時間に基づいて超音波導波管６内の水位を計測する。透水試験装置１では、超音波導波管６の内部への注水を止めた直後から超音波導波管６内の水位が平衡状態に戻るまでの水位の経時変化をこのように超音波の伝播時間に基づいて計測し、得られた水位の計測結果から透水係数を求める。 In the measuring instrument 5, the ultrasonic receiving circuit 53 receives this electric signal and outputs it to the signal processing circuit 54. The signal processing circuit 54 measures the water level in the ultrasonic waveguide 6 based on the input electrical signal under the control of the control unit 51. More specifically, in the signal processing circuit 54, after the ultrasonic transmission element of the ultrasonic transducer 7 transmits the ultrasonic wave U, the ultrasonic wave U is reflected by the water surface in the ultrasonic waveguide 6 and returns. The water level in the ultrasonic waveguide 6 is measured based on the propagation time required until the reflected wave R is received by the ultrasonic receiving element of the ultrasonic transducer 7. In the water permeation test apparatus 1, the time-dependent change of the water level from the time immediately after the water injection into the ultrasonic waveguide 6 is stopped to the time when the water level in the ultrasonic waveguide 6 returns to the equilibrium state is propagated in this way. Measure based on the time, and obtain the hydraulic conductivity from the measurement result of the obtained water level.

以下、本実施形態に係る透水試験装置１を用いたピエゾメータ法による透水係数を求める実施例について、図１及び図２を参照しつつ説明する。ここでは、超音波導波管６の密封端側の内部に設ける超音波トランスデューサ７として、周波数４０ｋＨｚ（空気中における波長が８．５ｍｍ）の超音波Ｕを送信する防水型で、外径が１４ｍｍの超音波トランスデューサ７を用いている。また、この超音波トランスデューサ７から送信される超音波Ｕを閉じ込めて効率良く伝播させるために、超音波導波管６として、内径が１８ｍｍ、外径が２２ｍｍの超音波導波管６を用いている。尚、この超音波導波管６は、周波数４０ｋＨｚの超音波Ｕを送信した場合に、内径を変えて水面からの反射波形を調べた実験結果において、最もノイズが少ない反射波形が得られた内径に設定したものである。 Hereinafter, the Example which calculates | requires the hydraulic conductivity by the piezometer method using the hydraulic permeability test apparatus 1 which concerns on this embodiment is described, referring FIG.1 and FIG.2. Here, the ultrasonic transducer 7 provided inside the sealed end side of the ultrasonic waveguide 6 is a waterproof type that transmits ultrasonic waves U having a frequency of 40 kHz (wavelength in air of 8.5 mm), and has an outer diameter of 14 mm. The ultrasonic transducer 7 is used. Further, in order to confine and efficiently propagate the ultrasonic wave U transmitted from the ultrasonic transducer 7, an ultrasonic waveguide 6 having an inner diameter of 18 mm and an outer diameter of 22 mm is used as the ultrasonic waveguide 6. Yes. The ultrasonic waveguide 6 has an inner diameter at which the reflected waveform with the least noise was obtained in the experimental results of examining the reflected waveform from the water surface by changing the inner diameter when transmitting an ultrasonic wave U having a frequency of 40 kHz. Is set.

このような透水試験装置１を用いて透水係数を求める際には、従来の測定用パイプを用いたピエゾメータ法と同様に、予め図２に示すように、測定対象となる地点の地盤２をボーリングして試験孔３を設けて、この試験孔３に超音波導波管６を開口端側を下側に向けて挿入する。この際、図２に示すように、超音波導波管６の先端に試験区間１１を設け、この試験区間１１が土で埋まらないように、金網（不図示）で保護する。尚、試験区間１１の長さＬは、試験区間の直径Ｄ＝２２ｍｍに対して、Ｌ／Ｄ≧４となるように、Ｌ＝１００ｍｍに設定している。 When the permeability coefficient is obtained using such a permeability test apparatus 1, as shown in FIG. 2, the ground 2 at the point to be measured is bored in advance, as in the conventional piezometer method using a measurement pipe. Then, the test hole 3 is provided, and the ultrasonic waveguide 6 is inserted into the test hole 3 with the open end side facing downward. At this time, as shown in FIG. 2, a test section 11 is provided at the tip of the ultrasonic waveguide 6, and the test section 11 is protected by a wire mesh (not shown) so as not to be buried with soil. The length L of the test section 11 is set to L = 100 mm so that L / D ≧ 4 with respect to the diameter D = 22 mm of the test section.

そして、超音波導波管６が試験孔３に挿入された状態で、超音波導波管６の注水口６２から内部に水を投入して、一時的に超音波導波管６内の水位を上昇させ、注水を止めた直後から超音波導波管６内の水位が平衡状態に戻るまでの水位の経時変化を超音波の伝播時間に基づいて計測し、この計測結果に基づいて、図４に示すような経過時間ｔ（ｓ）と水位差（ｍ）との関係を求める。図４に示す片対数グラフは、透水試験装置１を用いて超音波導波管６内の水位を経時的に計測した結果から求めた平衡水位ｈ_０（ｍ）と超音波導波管６内の水位ｈ（ｍ）との水位差ｓ＝｜ｈ_０−ｈ｜（ｍ）を縦軸の対数目盛にとり、経過時間ｔ（ｓ）を横軸の算術目盛にとったｌｏｇｓ−ｔ曲線の一例である。透水試験装置１では、この図４中の直線勾配から下記の数式（１）により透水係数ｋを算出する。本実施例では、試験区間の長さＬ＝１００ｍｍ、試験区間の孔径Ｄ＝２２ｍｍ、超音波導波管６の内径ｄ＝１８ｍｍに設定しており、下記の数式（１）にこれらの値を代入して計算した結果、透水係数ｋ＝１．５９×１０^−５ｍ／ｓが得られる。

Then, in a state where the ultrasonic waveguide 6 is inserted into the test hole 3, water is poured into the inside from the water injection port 62 of the ultrasonic waveguide 6, and the water level in the ultrasonic waveguide 6 is temporarily stored. The time-dependent change in the water level from immediately after the water injection is stopped until the water level in the ultrasonic waveguide 6 returns to the equilibrium state is measured based on the propagation time of the ultrasonic wave. The relationship between the elapsed time t (s) and the water level difference (m) as shown in FIG. The semi-logarithmic graph shown in FIG. 4 shows the equilibrium water level h ₀ (m) obtained from the result of measuring the water level in the ultrasonic waveguide 6 over time using the water permeation test apparatus 1 and the ultrasonic wave guide 6. Example of log-s curve in which water level difference s = | h ₀ −h | (m) with respect to water level h (m) is taken on a logarithmic scale on the vertical axis and elapsed time t (s) is taken on an arithmetic scale on the horizontal axis It is. In the water permeability test apparatus 1, the water permeability coefficient k is calculated from the linear gradient in FIG. In this example, the length L of the test section is set to 100 mm, the hole diameter D of the test section is set to 22 mm, and the inner diameter d of the ultrasonic waveguide 6 is set to 18 mm. These values are expressed in the following formula (1). As a result of substitution and calculation, the hydraulic conductivity k = 1.59 × 10 ⁻⁵ m / s is obtained.

尚、本実施例では、超音波導波管６内に水を注水して、一時的に水位を上昇させた後、超音波導波管６内の水位が平衡状態に戻る過程における水位の経時変化を超音波を用いて計測することにより、透水係数を求めているが、同様にして、超音波導波管６内の水を汲み上げて、一時的に水位を低下させた後、水位が平衡状態に戻る過程における水位の経時変化を超音波で計測することにより透水係数を求めることもできる。また、本実施例では、所謂非定常法を用いて透水係数を求めているが、これに限定されるものではなく、例えば、地盤の透水係数が１０^−４ｍ／ｓ以上のように大きい場合には、超音波導波管６内の水位を超音波で計測しながら、常に超音波導波管６内の水位が一定になるように水を注水して、その注水量を計測することにより透水係数を求める所謂定常法にも適用することができる。更に、地盤に揚水井を設け、その周囲に本実施形態に透水試験装置１の超音波導波管６を挿入して、揚水井で水を汲み上げて超音波導波管６内の水位の低下過程、および揚水停止後の超音波導波管６内の水位回復過程の水位の経時変化を計測することにより透水係数を求める方法にも適用することができる。 In the present embodiment, water is poured into the ultrasonic waveguide 6 to temporarily raise the water level, and then the water level changes over time in the process in which the water level in the ultrasonic waveguide 6 returns to an equilibrium state. The hydraulic conductivity is obtained by measuring the change using ultrasonic waves. Similarly, the water level is balanced after pumping up the water in the ultrasonic waveguide 6 and temporarily lowering the water level. The hydraulic conductivity can also be obtained by measuring the water level change with time in the process of returning to the state with ultrasonic waves. Further, in this embodiment, the permeability coefficient is obtained by using a so-called unsteady method, but the present invention is not limited to this. For example, the permeability coefficient of the ground is as large as 10 ⁻⁴ m / s or more. In this method, water is injected so that the water level in the ultrasonic waveguide 6 is always constant while the water level in the ultrasonic waveguide 6 is measured with ultrasonic waves, and the amount of water injected is measured. The present invention can also be applied to a so-called steady method for obtaining a water permeability coefficient. Further, a pumping well is provided on the ground, and the ultrasonic wave guide 6 of the water permeability test apparatus 1 is inserted around the pumping well, and water is pumped up by the pumping well to lower the water level in the ultrasonic wave guide 6. The present invention can also be applied to a method for obtaining a water permeability coefficient by measuring a change in the water level over time in the process and the water level recovery process in the ultrasonic waveguide 6 after stopping pumping.

また、本実施例では、周波数４０ｋＨｚの超音波Ｕを用いて計測する例を示しているが、この周波数の超音波Ｕに限定されるものではなく、地盤２の測定深さに応じて、超音波Ｕの周波数を適宜選択しても良く、本発明に係る透水試験装置１においては、超音波トランスデューサ７から送信される超音波Ｕが測定深さに応じて、２０〜１００ｋＨｚの間で設定されることが好ましい。尚、一般的に周波数が高くなると空気中を伝播する時に、超音波の減衰が大きくなるが、距離の測定分解能は向上する。従って、地盤２内の深い地点を測定する場合は低い周波数が良く、浅い定点を測定する場合は高い周波数が適している。 In the present embodiment, an example is shown in which the measurement is performed using the ultrasonic wave U having a frequency of 40 kHz. However, the measurement is not limited to the ultrasonic wave U having this frequency. The frequency of the sound wave U may be selected as appropriate. In the water permeability test apparatus 1 according to the present invention, the ultrasonic wave U transmitted from the ultrasonic transducer 7 is set between 20 and 100 kHz according to the measurement depth. It is preferable. In general, when the frequency increases, the attenuation of ultrasonic waves increases when propagating in the air, but the distance measurement resolution is improved. Therefore, a low frequency is good when measuring a deep point in the ground 2, and a high frequency is suitable when measuring a shallow fixed point.

また、本実施例では、１つの超音波検出器４を地盤に配置している例を示しているが、図５に示すように、実地盤２の測定対象となるエリアに超音波検出器４を複数配置して、それぞれの超音波検出器４を用いて計測を行うことにより透水係数の３次元分布を求めることができる。透水試験装置１ａでは、図５に示すように、それぞれの超音波検出器４を異なる位置及び異なる深さに設置している。これにより、それぞれの超音波検出器４で得られた計測結果から、位置及び深さが異なる地盤の透水係数を求めることができるので、そのエリアの透水係数の３次元分布を求めることができる。また、図５に示すように、透水試験装置１ａでは、地中の深い地点の透水係数を求める場合には、超音波導波管６の全体が地中に埋まるように挿入されることで、同じ長さの超音波検出器４を用いることができるので、超音波検出器４を埋める深さに応じて様々な長さの超音波導波管６を準備する必要がなく、超音波検出器４の共通化を図ることができ、コストを軽減することができる。また、超音波検出器４では、超音波導波管６の径を細く設定することができるので、従来のように大きな径の試験孔を掘削する必要がなく、地中の深い地点まで挿入することが容易であり、且つ、超音波が拡散されることなく、有効に深い地点まで伝播されるので、深い地点における透水係数の計測に非常に適している。尚、図５では、同じ長さの超音波検出器４を用いた場合を示しているが、これに限定されるものではなく、透水係数を求める地盤の深さに応じて、長さの異なる超音波検出器４を設置するようにしても良い。 In the present embodiment, an example is shown in which one ultrasonic detector 4 is arranged on the ground. However, as shown in FIG. 5, the ultrasonic detector 4 is located in an area to be measured on the actual ground 2. The three-dimensional distribution of the hydraulic conductivity can be obtained by arranging a plurality of and measuring using the respective ultrasonic detectors 4. In the water permeability test apparatus 1a, as shown in FIG. 5, the ultrasonic detectors 4 are installed at different positions and different depths. Thereby, since the hydraulic conductivity of the ground from which a position and depth differ can be calculated | required from the measurement result obtained by each ultrasonic detector 4, the three-dimensional distribution of the hydraulic conductivity of the area can be calculated | required. Further, as shown in FIG. 5, in the permeability test apparatus 1a, when the permeability coefficient of a deep point in the ground is obtained, the entire ultrasonic waveguide 6 is inserted so as to be buried in the ground, Since the ultrasonic detector 4 having the same length can be used, it is not necessary to prepare the ultrasonic waveguide 6 having various lengths depending on the depth of filling the ultrasonic detector 4, and the ultrasonic detector 4 can be shared, and the cost can be reduced. Further, in the ultrasonic detector 4, since the diameter of the ultrasonic waveguide 6 can be set thin, it is not necessary to dig a test hole having a large diameter as in the prior art, and it is inserted to a deep point in the ground. In addition, since the ultrasonic wave is effectively propagated to a deep point without being diffused, it is very suitable for measuring the hydraulic conductivity at a deep point. In addition, in FIG. 5, although the case where the ultrasonic detector 4 of the same length is used is shown, it is not limited to this, The length differs according to the depth of the ground for which the hydraulic conductivity is calculated. An ultrasonic detector 4 may be installed.

また、本実施例では、試験区間１１を設けた所謂ピエゾメータ法により透水係数の計測を行う例を示しているが、これに限定されるものではなく、透水試験装置１は、所謂チューブ法にも用いることができる。この場合には、図６に示すように、超音波導波管６の先端に試験区間１１を確保するための孔壁を設ける必要がないので、設置作業がピエゾメータ法よりも容易になる。 Further, in the present embodiment, an example is shown in which the permeability coefficient is measured by a so-called piezometer method provided with a test section 11, but the present invention is not limited to this, and the permeability test apparatus 1 is also a so-called tube method. Can be used. In this case, as shown in FIG. 6, it is not necessary to provide a hole wall for securing the test section 11 at the tip of the ultrasonic waveguide 6, so that the installation work becomes easier than the piezometer method.

チューブ法を用いた場合には、地盤２の透水係数を求めた後も、超音波導波管６をそのまま試験孔３に挿入した状態にしておくことで、透水試験装置１を透水係数の計測だけでなく、降雨による土中の水分・水位のモニタリングにも兼用することができる。つまり、透水試験装置１では、地盤２の透水係数を求めた後、超音波トランスデューサ７が受信した反射波Ｒの最大振幅に基づいて超音波導波管６の開口端付近での土中水分量を計測することができ、更に超音波トランスデューサ７が超音波Ｕを送信してから反射波Ｒを受信するまでに要する伝播時間に基づいて地盤２の地下水位を計測することができる。 When the tube method is used, the permeability test apparatus 1 measures the permeability coefficient by keeping the ultrasonic waveguide 6 inserted in the test hole 3 as it is after obtaining the permeability coefficient of the ground 2. Not only can it be used for monitoring moisture and water level in the soil due to rainfall. That is, in the water permeability test apparatus 1, after obtaining the water permeability coefficient of the ground 2, the moisture content in the soil near the open end of the ultrasonic waveguide 6 based on the maximum amplitude of the reflected wave R received by the ultrasonic transducer 7. Further, the groundwater level of the ground 2 can be measured based on the propagation time required for the ultrasonic transducer 7 to transmit the ultrasonic wave U and receive the reflected wave R.

この際、図３に示す信号処理回路５４は、地盤２の土中水分量を、反射波Ｒの最大振幅に基づいて検出する。より詳細に説明すると、土は土粒子部分と間隙部分とから構成されるが、土が乾燥状態の時は間隙部分の多くが空気で占められる。そのため、このような土に超音波Ｕがぶつかると、土粒子部分にぶつかった超音波Ｕは反射波Ｒとして戻ってくるが、間隙部分にぶつかった超音波Ｕは当該部分を透過するので、反射波Ｒとして戻ってこない。これにより、反射波Ｒの最大振幅は小さくなる一方、土が水分を多く含んだ状態の時は間隙部分の多くが水で占められる。そのため、このような土に超音波Ｕがぶつかると、土粒子部分にぶつかった超音波Ｕのみならず間隙部分にぶつかった超音波Ｕも反射波Ｒとして戻ってくる。これにより、反射波Ｒの最大振幅が大きくなる。従って、反射波Ｒの最大振幅を検出することによって、土中水分量を検出することができる。 At this time, the signal processing circuit 54 shown in FIG. 3 detects the amount of moisture in the soil of the ground 2 based on the maximum amplitude of the reflected wave R. More specifically, soil is composed of a soil particle portion and a gap portion. When the soil is in a dry state, most of the gap portion is occupied by air. For this reason, when the ultrasonic wave U collides with such soil, the ultrasonic wave U that collides with the soil particle part returns as a reflected wave R, but the ultrasonic wave U that collides with the gap part passes through the part, so that it is reflected. It does not return as wave R. Thereby, while the maximum amplitude of the reflected wave R becomes small, most of the gap portions are occupied by water when the soil contains a lot of moisture. Therefore, when the ultrasonic wave U hits such soil, not only the ultrasonic wave U hitting the soil particle part but also the ultrasonic wave U hitting the gap part returns as the reflected wave R. Thereby, the maximum amplitude of the reflected wave R becomes large. Therefore, the moisture content in the soil can be detected by detecting the maximum amplitude of the reflected wave R.

また、信号処理回路５４は、地盤２の地下水位を超音波Ｕの伝播時間すなわち超音波トランスデューサ７が超音波Ｕを送信してからその反射波Ｒを受信するまでの時間に基づいて検出する。より詳細に説明すると、地下水位面が土表面２１より低い位置にある間は、超音波トランスデューサ７から送信された超音波Ｕは、土表面２１によって反射される。一方、透水係数の計測後、降雨等によって再び水位が上昇し、図６に示すように、土表面２１を越えて高くなると、超音波トランスデューサ７から送信された超音波Ｕは、土表面２１ではなく超音波導波管６内の水面によって反射される。そのため、超音波導波管６内の水面が上昇するに伴って、超音波トランスデューサ７から超音波導波管６内の水面までの距離が短くなるので、超音波Ｕの伝播時間が徐々に短くなる。従って、超音波Ｕの伝播時間を検出することによって、地下水位を検出することができる。 Further, the signal processing circuit 54 detects the groundwater level of the ground 2 based on the propagation time of the ultrasonic wave U, that is, the time from when the ultrasonic transducer 7 transmits the ultrasonic wave U until the reflected wave R is received. More specifically, while the groundwater level surface is at a position lower than the soil surface 21, the ultrasonic wave U transmitted from the ultrasonic transducer 7 is reflected by the soil surface 21. On the other hand, after the water permeability coefficient is measured, the water level rises again due to rain and the like, and as shown in FIG. Without being reflected by the water surface in the ultrasonic waveguide 6. Therefore, as the water surface in the ultrasonic waveguide 6 rises, the distance from the ultrasonic transducer 7 to the water surface in the ultrasonic waveguide 6 is shortened, so that the propagation time of the ultrasonic wave U is gradually shortened. Become. Therefore, the groundwater level can be detected by detecting the propagation time of the ultrasonic wave U.

このように透水試験装置１を用いたチューブ法の場合には、例えば、土壌が飽和状態（地下水位面が土表面２１より高い位置にある状態）の時に透水係数を測定しておき、その後、非飽和状態（地下水位面が土表面２１より低い位置にある状態）における土壌の水分状態や降雨による地下水位の変化をモニタリングして、斜面崩壊予測のデータとして活用することができる。これにより、両者を測定するための設備費や現場の設置費等を低減することができる。特に、現場で多地点計測を行う場合に有効に利用することができる。 Thus, in the case of the tube method using the permeability test apparatus 1, for example, the permeability coefficient is measured when the soil is saturated (the groundwater level surface is at a position higher than the soil surface 21). It is possible to monitor the soil water state in the non-saturated state (the state where the groundwater level surface is lower than the soil surface 21) and the change in the groundwater level due to rainfall, and use it as data for slope failure prediction. Thereby, the installation cost for measuring both, the installation cost of the field, etc. can be reduced. In particular, it can be effectively used when performing multipoint measurement at the site.

図７は、超音波導波管６内の水面に超音波反射体１２を浮かべた超音波検出器４ａを示している。超音波導波管６内の水面で反射する超音波Ｕは、水面の揺らぎで若干乱れるため、反射強度が低下する。これを避けるため、超音波検出器４ａでは、図７に示すように、超音波反射体１２を超音波導波管６内の水面に浮かべ、超音波トランスデューサ７では、送信した超音波Ｕが、超音波導波管６内の水面ではなく、超音波反射体１２で反射して戻ってくる反射波Ｒを受信するよう構成されている。また、この場合には、測定器５は、超音波トランスデューサ７の超音波送信素子が超音波Ｕを送信してから、超音波Ｕが超音波反射体１２で反射して戻ってくる反射波Ｒを超音波トランスデューサ７の超音波受信素子で受信するまでに要する伝播時間に基づいて超音波導波管６内の水位を経時的に計測することにより地盤２の透水係数を求めることになる。 FIG. 7 shows the ultrasonic detector 4 a in which the ultrasonic reflector 12 is floated on the water surface in the ultrasonic waveguide 6. Since the ultrasonic wave U reflected by the water surface in the ultrasonic waveguide 6 is slightly disturbed by the fluctuation of the water surface, the reflection intensity decreases. To avoid this, in the ultrasonic detector 4a, as shown in FIG. 7, the ultrasonic reflector 12 is floated on the water surface in the ultrasonic waveguide 6, and in the ultrasonic transducer 7, the transmitted ultrasonic wave U is Instead of the water surface in the ultrasonic waveguide 6, the reflected wave R reflected by the ultrasonic reflector 12 and received back is received. In this case, the measuring instrument 5 reflects the reflected wave R that is returned from the ultrasonic wave U reflected by the ultrasonic reflector 12 after the ultrasonic wave transmitting element of the ultrasonic transducer 7 transmits the ultrasonic wave U. The water permeability coefficient of the ground 2 is obtained by measuring the water level in the ultrasonic waveguide 6 over time based on the propagation time required until the ultrasonic wave is received by the ultrasonic receiving element of the ultrasonic transducer 7.

超音波反射体１２としては、例えば、プラスティック等の水面に浮く材料でできた薄い円柱体の上面に、超音波Ｕを十分に反射する金属等が貼り付けたもの等を用いることができる。金属は空気に比べて音響インピーダンスが２桁以上大きいので、ほぼ１００％に近い反射率を示す。従って、このように超音波導波管６内の水面に超音波反射体１２を浮かべて測定する場合には、超音波トランスデューサ７から送信する超音波Ｕの強度が比較的弱い場合であっても、十分な精度で測定を行うことができる。尚、この超音波反射体１２を用いる方法により地盤２の透水係数を求めた後、降雨による土中の水分・水位のモニタリングを行う場合には、チューブ法を採用し、地盤２の透水係数の計測後に、一旦、超音波検出器４ａの密封端側を開放する。そして、例えば、先端に磁石が取り付けられた太さが超音波導波管６の内径よりも細い長尺の棒部材等を超音波導波管６内に挿入させる。これにより、超音波反射体１２は、上面が金属であるので、棒部材の先端の磁石に磁着され、棒部材を引き抜くことにより、超音波反射体１２を超音波導波管６内から取り除くことができる。その後、再び超音波導波管６の上側を密封させることで、そのまま土中の水分・水位のモニタリングを行うことができる。 As the ultrasonic reflector 12, for example, a thin cylindrical body made of a material that floats on the water surface such as a plastic, on which a metal or the like that sufficiently reflects the ultrasonic wave U is attached can be used. Since metal has an acoustic impedance that is two orders of magnitude greater than air, the reflectivity is close to 100%. Therefore, when the measurement is performed with the ultrasonic reflector 12 floating on the water surface in the ultrasonic waveguide 6 as described above, even when the intensity of the ultrasonic wave U transmitted from the ultrasonic transducer 7 is relatively weak. Measurement can be performed with sufficient accuracy. In addition, after obtaining the water permeability coefficient of the ground 2 by the method using the ultrasonic reflector 12, the tube method is employed to monitor the water permeability and water level in the soil due to rain, and the water permeability coefficient of the ground 2 is determined. After the measurement, the sealed end side of the ultrasonic detector 4a is once opened. Then, for example, a long rod member having a magnet attached to the tip and having a thickness smaller than the inner diameter of the ultrasonic waveguide 6 is inserted into the ultrasonic waveguide 6. Thereby, since the upper surface of the ultrasonic reflector 12 is metal, it is magnetically attached to the magnet at the tip of the bar member, and the ultrasonic reflector 12 is removed from the ultrasonic waveguide 6 by pulling out the bar member. be able to. Thereafter, by sealing the upper side of the ultrasonic waveguide 6 again, the moisture and water level in the soil can be monitored as they are.

以上のように、本発明に係る透水試験装置１では、細い超音波導波管６を用いることができるので、狭い孔径のボーリングで良く、掘削作業の労力を軽減することができる。そのため、現場の多地点で計測を行う場合に、特に設置が容易になる。また、揚水井の周囲に複数の超音波検出器４を配置するような多孔式による透水係数の計測にも適している。 As described above, in the water permeation test apparatus 1 according to the present invention, since the thin ultrasonic waveguide 6 can be used, it is sufficient to drill with a narrow hole diameter, and the labor of excavation work can be reduced. Therefore, installation is particularly easy when measurement is performed at multiple points on the site. Moreover, it is suitable also for the measurement of the hydraulic conductivity by the porous method which arrange | positions the some ultrasonic detector 4 around a pumping well.

また、透水試験装置１では、超音波導波管６内に超音波を閉じ込めて伝播させるため、従来の開放型のように超音波が拡散しないので、弱い超音波でも効率良く伝播できる。そのため、超音波を送信する超音波トランスデューサの消費電力が少なくて済むので、装置を簡易化することができ、現場でバッテリー駆動による計測を可能にすることができる。また、従来のフロート式水位計を用いた場合には、測定用パイプが傾けて設置されると、測定用パイプの内壁に水位計が接触してしまう虞があるため、正確な測定ができないが、透水試験装置１では、超音波導波管６内に超音波を閉じ込めて伝播させるため、超音波導波管６が多少傾斜して設置される場合でも、測定器５側で鉛直方向の距離補正を行うことで精度良く計測を行うことができる。また、従来のフロート式水位計は、測定用パイプ内の水面に置かれるので、水面が乱れやすくなるが、透水試験装置１では、非接触で計測を行うので、超音波導波管６内の水面が乱れることにより計測精度が低下することを防止することができ、水位の変化をｍｍの精度で安定的に計測することができる。 Further, in the water permeation test apparatus 1, since the ultrasonic wave is confined and propagated in the ultrasonic wave guide 6, the ultrasonic wave is not diffused unlike the conventional open type, so that even a weak ultrasonic wave can propagate efficiently. Therefore, since the power consumption of the ultrasonic transducer that transmits ultrasonic waves can be reduced, the apparatus can be simplified, and battery-driven measurement can be performed in the field. In addition, when a conventional float-type water level gauge is used, if the measuring pipe is installed with an inclination, the water level gauge may come into contact with the inner wall of the measuring pipe, so accurate measurement cannot be performed. In the water permeation test apparatus 1, since the ultrasonic wave is confined and propagated in the ultrasonic wave guide 6, the vertical distance on the measuring instrument 5 side even when the ultrasonic wave wave guide 6 is installed with a slight inclination. By performing correction, measurement can be performed with high accuracy. In addition, since the conventional float type water level meter is placed on the water surface in the measurement pipe, the water surface is likely to be disturbed. However, in the water permeation test apparatus 1, since measurement is performed in a non-contact manner, It is possible to prevent the measurement accuracy from being lowered due to the disturbance of the water surface, and it is possible to stably measure a change in the water level with an accuracy of mm.

また、透水係数が小さい時には、測定が終了するまでに長時間の計測を行うため、水位の自動計測が重要になるが、透水試験装置１では、超音波検出器４で電気的に計測するため、コンピュータやデータロガーへのデータ転送も容易であり、超音波検出器４から配線７２を介して電気信号を時刻とともに記録して測定器５へ出力するので、自動計測が可能である。 In addition, when the hydraulic conductivity is small, since the measurement is performed for a long time before the measurement is completed, automatic measurement of the water level is important. However, in the hydraulic test device 1, the ultrasonic detector 4 is used for electrical measurement. Data transfer to a computer or data logger is also easy, and since an electrical signal is recorded from the ultrasonic detector 4 via the wiring 72 together with the time and output to the measuring instrument 5, automatic measurement is possible.

尚、本発明の実施の形態は上述の形態に限るものではなく、本発明の思想の範囲を逸脱しない範囲で適宜変更することができる。 The embodiment of the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the scope of the idea of the present invention.

１、１ａ透水試験装置
２地盤
３試験孔
４、４ａ超音波検出器
５測定器（演算手段）
６超音波導波管
７超音波トランスデューサ（超音波送信素子及び超音波受信素子）
１１試験区間
１２超音波反射体
Ｕ超音波
Ｒ反射波 1, 1a Permeability test device 2 Ground 3 Test hole 4, 4a Ultrasonic detector 5 Measuring instrument (calculation means)
6 Ultrasonic Waveguide 7 Ultrasonic Transducer (Ultrasonic Transmitter and Ultrasonic Receiver)
11 Test section 12 Ultrasonic reflector U Ultrasonic R Reflected wave

Claims

An ultrasonic wave guide that is a tubular hollow member that is sealed at one end and open at the other end, and is inserted into a test hole excavated in the ground with the open end side down, and water is stored inside. An ultrasonic transmission element that is provided inside the sealed end side of the ultrasonic waveguide and that transmits ultrasonic waves toward the opening end side, and is provided inside the sealed end side of the ultrasonic waveguide. An ultrasonic receiving element that receives a reflected wave that is reflected from the ultrasonic wave transmitted from the ultrasonic transmitting element and reflected by the water surface in the ultrasonic waveguide, and an ultrasonic detector;
By measuring the water level in the ultrasonic waveguide over time based on the propagation time required from when the ultrasonic transmission element transmits the ultrasonic wave to when the ultrasonic reception element receives the reflected wave. Calculating means for determining the hydraulic conductivity of the ground,
The ultrasonic waveguide is I der 4 times or less of the ultrasonic wave of which the inner diameter is transmitted from the ultrasonic transmitting device has a diameter that its outer diameter is fitted to the test hole, Furthermore, the water permeability test apparatus is characterized by having a water injection port for injecting water into the inside or pumping in water inside the side surface on the sealed end side .

The ultrasonic waveguide is inserted into a test hole excavated in the ground of the site,
The calculating means obtains the water permeability coefficient of the ground and then determines the moisture content in the soil near the open end of the ultrasonic waveguide based on the maximum amplitude of the reflected wave received by the ultrasonic receiving element. And measuring the groundwater level of the ground based on the propagation time required from the time when the ultrasonic transmission element transmits the ultrasonic wave to the time when the ultrasonic reception element receives the reflected wave. The water permeability test apparatus according to claim 1.

An ultrasonic reflector floated on the water surface in the ultrasonic waveguide;
The arithmetic means transmits the ultrasonic wave toward the opening end side of the ultrasonic transmission element, and receives the reflected wave reflected by the ultrasonic reflector and returned by the ultrasonic reception element. The water permeability test apparatus according to claim 1 or 2, wherein a water permeability coefficient of the ground is obtained by measuring a water level in the ultrasonic waveguide with time based on a propagation time required until the time.

One end is sealed, a hollow tubular member whose other end is open, I inside diameter der 4 times the ultrasonic wavelength of transmitted from the ultrasonic transmitting element provided within the sealed end, An ultrasonic wave guide having an outer diameter that fits into a test hole excavated in the ground, and further has a water inlet on the side of the sealed end for injecting water or pumping internal water. water was stored inside the open end of the tube to the test holes in a state of being inserted in the lower side,
Transmitting the ultrasonic wave from the ultrasonic transmission element toward the opening end side;
Reflection in which the ultrasonic wave transmitted from the ultrasonic wave transmitting element is reflected by the water surface in the ultrasonic wave waveguide and returned by an ultrasonic wave receiving element provided inside the sealed end side of the ultrasonic wave waveguide Receive waves,
By measuring the water level in the ultrasonic waveguide over time based on the propagation time required from when the ultrasonic transmission element transmits the ultrasonic wave to when the ultrasonic reception element receives the reflected wave. A water permeability test method characterized by obtaining a water permeability coefficient of the ground.

The ultrasonic waveguide is inserted into a test hole excavated in the ground of the site,
After obtaining the water permeability coefficient of the ground, based on the maximum amplitude of the reflected wave received by the ultrasonic receiving element, to measure the amount of moisture in the soil near the opening end of the ultrasonic waveguide, The groundwater level of the ground is measured based on a propagation time required from when the ultrasonic transmission element transmits the ultrasonic wave to when the ultrasonic reception element receives the reflected wave. The water permeability test method described.

After inserting the ultrasonic waveguide into the test hole so that water is stored inside with the opening end side down, an ultrasonic reflector is floated on the water surface in the ultrasonic waveguide, The ultrasonic wave is transmitted from the ultrasonic wave transmitting element toward the opening end side, and the ultrasonic wave transmitted from the ultrasonic wave transmitting element by the ultrasonic wave receiving element is reflected by the ultrasonic wave reflector and returns. The reflected wave is received, and the water level in the ultrasonic waveguide is changed over time based on the propagation time required from when the ultrasonic transmission element transmits the ultrasonic wave until the ultrasonic reception element receives the reflected wave. The permeability test method according to claim 4 or 5, wherein the permeability coefficient of the ground is obtained by performing measurement.