JPH055315B2 - - Google Patents
Info
- Publication number
- JPH055315B2 JPH055315B2 JP61240212A JP24021286A JPH055315B2 JP H055315 B2 JPH055315 B2 JP H055315B2 JP 61240212 A JP61240212 A JP 61240212A JP 24021286 A JP24021286 A JP 24021286A JP H055315 B2 JPH055315 B2 JP H055315B2
- Authority
- JP
- Japan
- Prior art keywords
- sonde
- pair
- borehole
- waves
- piezoelectric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 37
- 239000007788 liquid Substances 0.000 claims description 10
- 230000008878 coupling Effects 0.000 claims description 8
- 238000010168 coupling process Methods 0.000 claims description 8
- 238000005859 coupling reaction Methods 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 7
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims 1
- 239000000523 sample Substances 0.000 claims 1
- 238000000034 method Methods 0.000 description 16
- 230000010355 oscillation Effects 0.000 description 16
- 230000010287 polarization Effects 0.000 description 5
- 230000001133 acceleration Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000000644 propagated effect Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 238000013016 damping Methods 0.000 description 2
- 230000005674 electromagnetic induction Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 210000002445 nipple Anatomy 0.000 description 2
- 230000001902 propagating effect Effects 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000005520 electrodynamics Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003100 immobilizing effect Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
Landscapes
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
- Geophysics And Detection Of Objects (AREA)
Description
本発明は、地下探査等を行うために、ボーリン
グ孔内で人工的に弾性波を発生させ、それを同じ
ボーリング孔内で電気信号として検知し測定する
地下人工弾性波の測定装置に関する。
The present invention relates to an underground artificial elastic wave measuring device that artificially generates elastic waves in a borehole and detects and measures the waves as electrical signals in the same borehole in order to conduct underground exploration and the like.
従来、水を満たしたボーリング孔内に発振器と
受振器とを、ボーリング孔軸（以下、単に孔軸と
記す）方向に互いに所定間隔だけ離して配置し、
発振器の振動を水を介してボーリング孔の周壁部
（以下、孔壁という）に伝達し、その孔壁を伝播
してきたＳ波（剪断波）またはＰ波（圧力波）を
受振記で電気信号として検知する方法として、次
ぎのように円筒形圧電式発振器を使用した屈折波
法（間接波法）と孔壁固着型受振記または漂遊型
受振記を使用した直接波法と、４極圧電式発振器
を使用した４極剪断波法が知られているが、それ
ぞれ下記のような問題があつた。
屈折波法は、第９図Ｉ，に示すように発振器
１として円筒形圧電素子を使用し、これからボー
リング孔２の孔軸Ｏと直交する全方向に、つまり
Ｐ波を放射状に発振する。このＰ波は、ボーリン
グ孔２内の水を介してその孔壁に伝達する。そし
て、ここで屈折Ｐ波と、Ｐ波がＳ波に変換された
変換Ｓ波とが発生し、両者とも孔壁に沿つて伝播
する。その伝播する屈折Ｐ波は再びボーリング孔
２内の水柱を屈折し、また変換Ｓ波はＰ波に再び
変換されて受振記３に受振される。この受振器３
は、発振器１と同じく円筒形の圧電素子で構成さ
れている。
問題点…Ｐ波はＳ波より伝播速度が速いため、
先にＰ波が受振器３に検知され、その後Ｓ波が検
知される。従つて、記録紙上では、Ｓ波がＰ波の
波形の後に重畳して表れ、両波が十分に分離して
いないため、読み取り難い。また、孔壁における
孔内水と地層の屈折Ｓ波を利用しているため、水
の伝播速度（約1500ｍ／ｓ）より遅いＳ波速度を
もつ地層の測定はできない。
直接波法は、発振器としていわゆる電磁型発振
器、また受振器として孔壁固着型受振器または漂
遊型受振器を使用する。電磁型発振器は、コイル
とその中を通る永久磁石とを有し、電磁力によつ
てボビン組立体が運動し、そのピストン運動で水
を放出することによつて、孔軸と直交する一方向
に、つまり非対称的に発振し、Ｓ波を発生する。
孔壁固着式受振器は、第１０図に示すようにその
受振器７自体を孔壁２に固定してこの孔壁２の変
位を受振器７に直接伝達し、該受振器７内におい
てその運動を電磁誘導作用によつて検知する。ま
た、第１１図に示すように漂遊式受振器８は、ボ
ーリング孔内の水中を漂遊させ、孔壁２の音圧を
孔内水を介して受振器８に作用させ、それを電磁
誘導作用によつて検知する。
問題点…Ｓ波を直接検知できるが、孔壁固着式
及び漂遊式のいずれも質点速度と比例する電圧感
度を有する動電型受振器を使用しているため、高
周波で感度が低下し、Ｓ波速度の大きい硬い地層
の測定は難しい。また、Ｓ波の検知に当たり、液
柱を伝播するチユーブウエーブの擾乱を受け易
い。
４極剪断波法は、詳細には特開昭58−210585号
公報に開示されているように発振器として、４枚
の圧電素子板をゾンデの軸線（孔軸）の回りに４
面対向配置関係にした４極型発振器を、また受振
器として発振器と同一構成の４極型受振器を使用
するもので、発振・受振方式としては屈折波法の
範疇に入る。４極型発振器は、第１２図にその概
要を図示するように、オイル４が封入されたゾン
デ５内に、例えば正の電圧を印加したときいずれ
もゾンデ５の外方へ歪む第１の圧電素子板６1と
第２の圧電素子板６2とを、ゾンテ５の一本の直
径線−（第１の発振軸）に沿つて両側に対向
配置させ、また正の電圧を印加したときいずれも
ゾンテ５の内方へ歪む第３の圧電素子板６3と第
４の圧電素子板６4とを、上記直径線−とは
直交する別の直径線−（第２の発振軸）に沿
つて両側に対向配置したものである。これら４枚
の圧電素子板６1〜６4に同時に正負の電圧を交互
に印加すると、第１及び第２の圧電素子板６1，
６2とが第１の発振軸に沿つて正のＰ波をそれぞ
れ発生したとき、第３及び第４の圧電素子板６3，
６4は第２の発振軸に沿つてそれぞれ負のＰ波を
発生する。すなわち正負の対称振動が生じる。こ
の指向性パターンは、破線で示すように、第１の
発振軸と第２の発振軸との２等分線上に４つのＳ
波最大エネルギーが生じる。
このように発振された４つのＰ波は、ゾンデ５
内のオイル４を介して孔内水に伝達され、さらに
これから孔壁に伝播して合成され、その合成Ｐ波
が地層へと屈折し４つのＰ波の共通成分のみが互
いに干渉することにより、地層に４極剪断波（４
極のＳ波）が生じる。この４極Ｓ波は孔内水に戻
り、４極型受振器内のオイルを介しその４極の圧
電素子板によつて各極ごとに検知される。４極型
受振器の４枚の圧電素子板は、４極型発振器の４
枚の圧電素子と方位を同じにしてある。
問題点…４つのＰ波を発生してそれを地層で合
成させ、その合成による干渉によつて４極Ｓ波を
生じさせ、それを各極ごとに検知して測定データ
の和をとるため、測定結果によるノイズは少なく
なるものの、データの処理が複雑になる。また、
間接波法の欠点である水のＰ波速度（約1500ｍ／
sec）より遅い地層のＳ極速度は検知できない。
本発明の目的は、従来のこのような問題点に鑑
み、特にＳ波を直接かつ簡単にしかも硬い地層で
も精度良くかつ解析容易に測定でき、またＰ波も
Ｓ波と同程度に簡単に測定できるようにすること
である。
Conventionally, an oscillator and a geophone are placed in a borehole filled with water at a predetermined distance from each other in the direction of the borehole axis (hereinafter simply referred to as the borehole axis).
The vibrations of the oscillator are transmitted to the peripheral wall of the borehole (hereinafter referred to as the "hole wall") through water, and the S waves (shear waves) or P waves (pressure waves) propagated through the hole wall are converted into electrical signals in the form of a receiver. The methods for detecting the Four-pole shear wave methods using oscillators are known, but each method has the following problems. In the refracted wave method, as shown in FIG. 9I, a cylindrical piezoelectric element is used as an oscillator 1, from which P waves are radially oscillated in all directions orthogonal to the hole axis O of the borehole 2. This P wave is transmitted to the borehole wall via the water in the borehole 2. Then, a refracted P wave and a converted S wave, which is a P wave converted into an S wave, are generated, and both propagate along the hole wall. The propagating refracted P wave refracts the water column in the borehole 2, and the converted S wave is again converted into a P wave and is received by the receiver 3. This geophone 3
Like the oscillator 1, it is composed of a cylindrical piezoelectric element. Problem: P waves have a faster propagation speed than S waves, so
First, the P wave is detected by the geophone 3, and then the S wave is detected. Therefore, on the recording paper, the S wave appears superimposed after the P wave, and the two waves are not sufficiently separated, making it difficult to read. Furthermore, since the method uses borehole water at the hole wall and refracted S-waves from the strata, it is not possible to measure strata with an S-wave velocity slower than the propagation velocity of water (approximately 1500 m/s). The direct wave method uses a so-called electromagnetic oscillator as an oscillator, and a hole wall fixed type geophone or a stray type geophone as a geophone. An electromagnetic oscillator has a coil and a permanent magnet passing through the coil, and the bobbin assembly is moved by electromagnetic force, and the piston movement releases water, thereby generating energy in one direction perpendicular to the hole axis. In other words, it oscillates asymmetrically and generates S waves.
As shown in FIG. 10, the hole wall-fixed type geophone fixes the geophone 7 itself to the hole wall 2 and directly transmits the displacement of the hole wall 2 to the geophone 7. Movement is detected by electromagnetic induction. In addition, as shown in FIG. 11, the stray type geophone 8 allows the sound pressure of the hole wall 2 to float in the water inside the borehole and act on the geophone 8 through the water in the borehole, and causes it to act on the electromagnetic induction effect. Detected by. Problem: Although it is possible to directly detect S waves, both the hole wall fixed type and the stray type use electrodynamic geophones with voltage sensitivity proportional to mass point velocity, so sensitivity decreases at high frequencies and S waves are detected directly. It is difficult to measure hard strata with high wave speeds. Furthermore, when detecting S waves, they are susceptible to disturbances from tube waves propagating through the liquid column. In the quadrupole shear wave method, as disclosed in Japanese Patent Application Laid-Open No. 58-210585, four piezoelectric element plates are used as oscillators to rotate four piezoelectric element plates around the axis of the sonde (hole axis).
It uses a quadrupole oscillator placed in a surface-to-plane relationship, and a quadrupole receiver with the same configuration as the oscillator as a receiver, and the oscillation/reception method falls under the refraction wave method. As shown schematically in FIG. 12, the 4-pole oscillator is a first piezoelectric oscillator that distorts outward when, for example, a positive voltage is applied to the sonde 5 in which oil 4 is sealed. When the element plate 6 1 and the second piezoelectric element plate 6 2 are arranged facing each other on both sides along one diameter line (first oscillation axis) of the Sonte 5, and when a positive voltage is applied, Also, the third piezoelectric element plate 63 and the fourth piezoelectric element plate 64 , which are distorted inwardly, of the sonte 5 are moved along another diameter line (second oscillation axis) perpendicular to the above-mentioned diameter line. They are placed facing each other on both sides. When positive and negative voltages are applied alternately to these four piezoelectric element plates 6 1 to 6 4 at the same time, the first and second piezoelectric element plates 6 1 ,
6 2 respectively generate positive P waves along the first oscillation axis, the third and fourth piezoelectric element plates 6 3 ,
6 4 each generate a negative P wave along the second oscillation axis. In other words, positive and negative symmetrical vibrations occur. This directivity pattern consists of four S
Wave maximum energy occurs. The four P waves oscillated in this way are transmitted to sonde 5.
The P waves are transmitted to the water in the hole through the oil 4 inside the hole, and then propagated to the hole wall where they are synthesized.The resultant P waves are refracted into the strata, and only the common components of the four P waves interfere with each other. Quadrupolar shear waves (4
polar S waves) are generated. This 4-pole S wave returns to the borehole water and is detected for each pole by the 4-pole piezoelectric element plate via the oil in the 4-pole geophone. The four piezoelectric element plates of the quadrupole geophone are the four piezoelectric element plates of the quadrupole oscillator.
The orientation is the same as that of the two piezoelectric elements. Problem: To generate four P waves, combine them in the strata, and generate quadrupole S waves by interference from the combination, detect it for each pole and calculate the sum of the measured data. Although the measurement results are less noisy, the data processing becomes more complex. Also,
P-wave velocity of water (approximately 1500m/
S-pole velocities in strata slower than sec) cannot be detected. In view of these conventional problems, it is an object of the present invention to make it possible to directly and easily measure S waves even in hard strata with high accuracy and ease of analysis, and to measure P waves as easily as S waves. The goal is to make it possible.
本発明による地下人工弾性波の測定装置は次の
からの構成を採用したことに特徴がある。
ボーリング孔内に挿入される円筒形のゾンデ
の外周壁に、少なくとも一対の対向する発振部
取付孔と、少なくとも一対の対向する受振部取
付孔とを上下に離して設けたこと。
一対の発振部取付孔の間のゾンデ内部及び一
対の受振部取付孔の間のゾンデ内部にそれぞれ
ボーリング孔内の液体を導入する導水部を設け
たこと。
一対の発振部取付孔に、ゾンデの内外の液体
に浸漬される一対の圧電振動板２５ａ，２５ｂ
を、ゾンデの軸線と平行にしかもその軸線と直
交する単軸に沿つて同方向に分極しボーリング
孔内の液体に直接Ｓ波を生じさせるように対向
させて配置したこと。
一対の受振部取付孔に、ゾンデの内外の液体
に浸漬される一対の圧電受振板１９ａ，１９ｂ
を、ゾンデの軸線と平行にしかもその軸線と直
交する単軸に沿つて同方向に分極しボーリング
孔内の液体からの直接Ｓ波を受振できるように
対向させて配置したこと。
ゾンデに、その慣性を大きくして上記一対の
圧電受振板をボーリング孔軸に対して不動する
ための重錘を設けたこと。
上記一対の圧電受振板の結合極性を切り換え
る極性切換手段を備えたこと。
The underground artificial elastic wave measuring device according to the present invention is characterized by adopting the following configuration. At least one pair of opposing oscillating part mounting holes and at least one pair of opposing vibration receiving part mounting holes are provided vertically apart from each other on the outer peripheral wall of a cylindrical sonde to be inserted into a borehole. A water guide part is provided inside the sonde between the pair of oscillating part mounting holes and inside the sonde between the pair of receiving part mounting holes, respectively, for introducing the liquid in the borehole. A pair of piezoelectric diaphragms 25a and 25b are immersed in the liquid inside and outside the sonde in the pair of oscillating unit mounting holes.
are polarized in the same direction along a single axis parallel to and orthogonal to the axis of the sonde, and are placed opposite to each other so as to generate S waves directly in the liquid in the borehole. A pair of piezoelectric vibration receiving plates 19a and 19b are immersed in the liquid inside and outside the sonde in the pair of vibration receiving unit mounting holes.
are polarized in the same direction along a single axis that is parallel to and orthogonal to the axis of the sonde, and are placed facing each other so that they can directly receive S waves from the liquid in the borehole. The sonde is provided with a weight for increasing its inertia and immobilizing the pair of piezoelectric vibration plates with respect to the borehole axis. A polarity switching means is provided for switching the coupling polarity of the pair of piezoelectric sound receiving plates.
本発明の測定装置の測定原理を第１図によつて
説明する。
一対の圧電振動板２５ａ，２５ｂに比較的低周
波のパルスを印加すると、これら一対の圧電振動
板２５ａ，２５ｂは、その分極方向が同じでしか
もボーリング孔内水中に浸漬されているため、ボ
ーリング孔軸Ｏ−Ｏと直交する発振軸X2−X2に
沿つて非対称音圧Ｐを生じ、ボーリング孔内水に
直接に単軸発振による直接Ｓ波を生じさせる。
孔内水はこの非対称音圧Ｐを直接受けて孔壁に
伝達し、直接Ｓ波が孔壁に沿つて孔軸Ｏ−Ｏ方向
に伝播する。この直接Ｓ波は、圧電振動板２５
ａ，２５ｂと同様に分極方向が同じでもしかもボ
ーリング孔内水中に浸漬されている一帯の圧電受
振板１９ａ，１９ｂに直接受振される。
この場合、その直接Ｓ波によつて孔壁が変位し
孔内水が動揺しても、ゾンデ自体は重錘によつて
慣性が大きくなつているため、孔内水によつて干
渉されることなく静止状態を保持する。このた
め、一対の圧電受振板１９ａ，１９ｂは、その大
きさに比べて直接Ｓ波の波長が十分に長いことか
ら、孔壁との相対加速度運動による非対称音圧Ｐ
のみを受ける。このとき、これら圧電受振板１９
ａ，１９ｂが電気的に並列結合してある場合に
は、その結合回路に、伝播してきた直接Ｓ波に応
じて波形の電圧が生じる。
圧電受振板１９ａ，１９ｂはこのように非対称
音圧Ｐのみを受けるため、チユーブウエーブや孔
壁と孔内水との間の屈折波に乱されることはな
い。
一対の圧電受振器１９ａ，１９ｂの極性を切り
換えて直列結合したときは、その結合回路にＰ波
に応じた波形の電圧が生ずる。
The measurement principle of the measuring device of the present invention will be explained with reference to FIG. When a relatively low-frequency pulse is applied to the pair of piezoelectric diaphragms 25a, 25b, the pair of piezoelectric diaphragms 25a, 25b have the same polarization direction and are immersed in the water in the borehole. An asymmetrical sound pressure P is generated along the oscillation axis X 2 -X 2 orthogonal to the axis OO, and a direct S wave due to uniaxial oscillation is generated directly in the borehole water. The water in the hole directly receives this asymmetric sound pressure P and transmits it to the hole wall, and the S wave directly propagates along the hole wall in the direction of the hole axis O-O. This direct S wave is transmitted to the piezoelectric diaphragm 25
Similar to a and 25b, the polarization direction is the same, but the vibration is directly received by the area of the piezoelectric vibration receiving plates 19a and 19b which are immersed in the water in the borehole. In this case, even if the borehole wall is displaced by the direct S wave and the borehole water is agitated, the sonde itself has a large inertia due to the weight, so there is no interference from the borehole water. maintain a stationary state. Therefore, since the wavelength of the direct S wave is sufficiently long compared to the size of the pair of piezoelectric sound receiving plates 19a and 19b, the asymmetric sound pressure P due to the relative acceleration movement with the hole wall
receive only At this time, these piezoelectric vibration plates 19
When a and 19b are electrically coupled in parallel, a waveform voltage is generated in the coupling circuit in response to the propagated direct S wave. Since the piezoelectric sound receiving plates 19a and 19b receive only the asymmetric sound pressure P in this way, they are not disturbed by tube waves or refracted waves between the hole wall and the water in the hole. When the polarity of the pair of piezoelectric geophones 19a and 19b is switched and they are coupled in series, a voltage having a waveform corresponding to the P wave is generated in the coupling circuit.
以下、本発明の実施例について図面を参照に詳
細に説明する。
第３図は本発明の方法の実施の態様を示し、円
筒形のゾンデ１０を、水を満たしたボーリング孔
１１中にケーブル１２によつて吊り降ろす。ゾン
デ１０には、その慣性を大きくするために上下複
数個所に鉛等による重錘１０ｂが設けられてい
る。また、ゾンデ１０は、その上端と下端に第１
の発振器１３1と第２の発振器１３2、これらの間
の中間部に第１の受振器１４1と第２の受振器１
４2とを備えている。これら発振器の制御及び受
振器が検知したデータの処理はマイクロコンピユ
ータ１５によつて行う。このマイクロコンピユー
タ１５より出力される発振器１３1・１３2へのデ
ジタル信号は、Ｄ／Ａ・Ａ／Ｄ変換器１６によつ
てＤ／Ａ変換された後、アツテネータ１６ａよつ
て減衰して送信され、また受振器１４1，１４2か
らの信号は、増幅器１６ｂで増幅されＤ／Ａ・
Ａ／Ｄ変換器１６によつてＡ／Ｄ変換されてマイ
クロコンピユータ１５へ入力され、演算される。
発振器１３1，１３2及び受振器１４1，１４2
は、それぞれゾンテ１０の外壁の一部を構成する
円筒形ケース１０ａに個別に設けられ、全体とし
て一本に連結されているが、実質的にはほぼ同じ
構造である。
今、そのうちの第１の受振器１４1について説
明すると、第４図ないし第６図に示すようにケー
ス１０ａには、その周壁の対向する部分に一対の
方形な取付孔１７が設けられ、またその上下両側
に導水部として複数個の導水孔１８が穿設されて
いる。一対の取付孔１７には、バイモルフ構造の
圧電素子（例えば、黄銅板の両面に圧電セラミツ
クスを蒸着したもの）で構成された一対の圧電受
振板１９ａ，１９ｂが、円形孔２０ａを有する金
属板２０を介して保持されている。各圧電受振板
１９ａ，１９ｂはゴム等の防水材で２１で包被さ
れ、該防水材２１を介してケース１０ａの内外両
方の水圧を受けるようになつている。
そして、両圧電受振板１９ａ，１９ｂは、その
中心を結ぶ軸線がケース１０ａの軸線（ゾンデ１
０の軸線）Ｙ−Ｙと直交する一本の受振軸X1−
X1となるようにしかも分極方向Ｓが同じになる
ように平行に対向している。ケース１０ａの上端
には電気回路等を実装するための円筒形の回路ボ
ツクス２２が接続され、この回路ボツクス２２の
上端とケース１０ａの下端には、ケーブル接続用
コネクタ２３を内蔵した上下のニツプル２４が接
続されている。
第２の受振器１４2もこれと同じ構造である。
第１及び第２の発振器１３1，１３2は、第１の
受振器１４1では圧電受振板１９ａ，１９ｂを構
成している一対のバイモルフ構造の圧電素子が、
第４〜６図において括弧付きの符号で示すよう
に、受振とは逆の発振作用を行う一対の圧電振動
板２５ａ，２５ｂを構成していることにおいて、
第１の受振器１４1と相違するが、その他につい
ては実質的に同じである。ただし、第２の発振器
１３2はゾンデ１０の下端に取り付けるため、第
１の受振器１４1における下端のニツプル２４は
なく、それに代えてケース１０ａの下端を閉じる
蓋が取り付けられている。
一対の圧電振動板２５ａ，２５ｂは、その中心
線を結ぶ軸線がゾンデ１０の軸線Ｙ−Ｙと直交す
る一本の発振軸X2−X2となつており、しかもそ
の発振軸X2−X2は一対の圧電受振板１９ａ，１
９ｂの受振軸X1−X1と同じ向きになつている。
なお、発振器１３1，１３2及び受信器１４1，
１４2相互は、音波を緩衝するため可撓性を有す
る連結パイプ１０ｃによつて連結されている。
ゾンデ１０を第３図に示すような状態にして第
１の発振器１３1または第２の発振器１３2の一対
の圧電振動板２５ａ，２５ｂに比較的低周波
（0.5KHz〜5KHz）のパルスを印加すると、これら
一対の圧電振動板２５ａ，２５ｂはその分極方向
Ｓが同じであるため、第１図に示すようにゾンデ
１０の軸線Ｙ−Ｙ（孔軸Ｏ−Ｏ）と直交する発振
軸X2−X2に沿つて非対称音圧Ｐを生じ、孔内水
に直接に単軸発振によるＳ波を生じさせる。第１
図はその指向性パターンを示し、発振軸X2−
X2と直交する方向にＳ波最大エネルギー軸があ
る。孔内水はこの非対称音圧Ｐを直接受けて孔壁
に伝達し、Ｓ波が孔壁に沿つて孔軸Ｏ−Ｏ方向に
伝播する。このＳ波は孔内水を介して第１の受振
器１４1及び第２の受振器１４2に伝達されるが、
そのＳ波によつて第２図に示すように孔壁が変位
し孔内水が動揺しても、ゾンデ１０体はその重錘
１０ｂによつて慣性が大きくなつているため、孔
内水によつて干渉されることなく静止状態を保持
する。このため、両受振器１４1，１４2の一対の
圧電受振板１９ａ，１９ｂは、その大きさに比べ
てＳ波の波長が十分に長いことから、第１図に
示すように孔壁との相対加速度運動による非対称
音圧Ｐのみを受ける。このとき、これら圧電受振
板１９ａ，１９ｂが第７図に示すごとく電気的に
並列結合してある場合には、その結合回路に、伝
播してきたＳ波に応じた波形の電圧が生じる。圧
電受振板１９ａ，１９ｂはこのように非対称音圧
Ｐのみを受けるため、チユーブウエーブや孔壁と
孔内水との間の屈折波に乱されることはない。
今、孔壁における加速度をＵ¨とすると、円筒形
に見立てたときの圧電受振板１９ａ・１９ｂに作
用する圧力Ｐは次式で表される。
Ｐ＝−（ｍ／2a）・Ｕ¨
ここで、
ｍ＝πa2・ρw
ただし、 ａは円筒半径、ρwは孔内水の密度
である。
一方、第８図に示すごとく両圧電受振板１９
ａ，１９ｂを直列結合した場合（このとき、両圧
電振動板２５ａ，２５ｂも直列結合する）には、
その結合回路にＰ波に応じた波形の電圧が生じる
もので、結合極性を切り換えることによつてＳ波
とＰ波を任意に選択して検知できる。その極性切
換を行う手段として、ゾンデ１０には外部より遠
隔操作できる極性切換回路２６が備えられてい
る。
ゾンデ１０は、２つの受振器１４1，１４2の上
下に２つの発振器１３1，１３2を備えているた
め、各受振器について２つの発振器よりの発振に
基づくＳ波またはＰの測定記録を解析することに
より、両受振器の特性の違いを除去することがで
き、減衰定数を精度良く求めることができる。
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an embodiment of the method according to the invention, in which a cylindrical sonde 10 is suspended by a cable 12 into a borehole 11 filled with water. In order to increase the inertia of the sonde 10, weights 10b made of lead or the like are provided at multiple locations on the top and bottom of the sonde 10. The sonde 10 also has first
oscillator 13 1 and second oscillator 13 2 , and intermediate between them a first geophone 14 1 and a second geophone 1
It is equipped with 4 2 . Control of these oscillators and processing of data detected by the geophone are performed by the microcomputer 15. The digital signals outputted from the microcomputer 15 to the oscillators 13 1 and 13 2 are D/A converted by the D/A/A/D converter 16, and then attenuated by the attenuator 16a before being transmitted. , and the signals from the geophones 14 1 and 14 2 are amplified by the amplifier 16b and sent to the D/A.
The signal is A/D converted by the A/D converter 16 and input to the microcomputer 15 for calculation. Oscillators 13 1 , 13 2 and geophones 14 1 , 14 2
are individually provided in the cylindrical case 10a that constitutes a part of the outer wall of the Sonte 10, and are connected as a whole, but they have substantially the same structure. Now, to explain the first vibration receiver 141 , as shown in FIGS. 4 to 6, the case 10a is provided with a pair of rectangular mounting holes 17 in opposing parts of its peripheral wall. A plurality of water guide holes 18 are provided as water guide portions on both upper and lower sides thereof. In the pair of mounting holes 17, a pair of piezoelectric vibration receiving plates 19a and 19b each made of a piezoelectric element with a bimorph structure (for example, a brass plate with piezoelectric ceramics deposited on both sides) are attached to a metal plate 20 having a circular hole 20a. is held through. Each piezoelectric sound receiving plate 19a, 19b is covered with a waterproof material 21 such as rubber, and receives water pressure from both the inside and outside of the case 10a through the waterproof material 21. The axis of both piezoelectric vibration receiving plates 19a and 19b connecting their centers is the axis of the case 10a (the sonde 1
0 axis) One receiving axis X 1 − perpendicular to Y-Y
They face each other in parallel so that X 1 and the polarization directions S are the same. A cylindrical circuit box 22 for mounting an electric circuit, etc. is connected to the upper end of the case 10a, and upper and lower nipples 24 with built-in connectors 23 for connecting cables are connected to the upper end of the circuit box 22 and the lower end of the case 10a. is connected. The second geophone 14 2 also has the same structure. In the first and second oscillators 13 1 and 13 2 , a pair of bimorph piezoelectric elements constituting piezoelectric vibration receiving plates 19 a and 19 b are used in the first vibration receiver 14 1 .
As shown by the parenthesized symbols in FIGS. 4 to 6, a pair of piezoelectric diaphragms 25a and 25b that perform an oscillation action opposite to that of receiving vibrations are configured.
Although it is different from the first geophone 14 1 , other aspects are substantially the same. However, since the second oscillator 13 2 is attached to the lower end of the sonde 10, the nipple 24 at the lower end of the first receiver 14 1 is not provided, and instead a lid is attached to close the lower end of the case 10a. The pair of piezoelectric diaphragms 25a and 25b have an oscillation axis X 2 -X 2 whose axis line connecting their center lines is orthogonal to the axis Y-Y of the sonde 10, and the oscillation axis X 2 -X 2 is a pair of piezoelectric vibration receiving plates 19a, 1
It is oriented in the same direction as the receiving axis X1 - X1 of 9b. Note that the oscillators 13 1 , 13 2 and the receivers 14 1 ,
14 2 are connected to each other by a flexible connecting pipe 10c to buffer sound waves. With the sonde 10 in the state shown in FIG. 3, a relatively low frequency (0.5KHz to 5KHz) pulse is applied to the pair of piezoelectric diaphragms 25a and 25b of the first oscillator 131 or the second oscillator 132 . Then, since these pair of piezoelectric diaphragms 25a and 25b have the same polarization direction S, the oscillation axis An asymmetrical sound pressure P is generated along -X2 , and an S wave due to uniaxial oscillation is generated directly in the borehole water. 1st
The figure shows its directivity pattern, with the oscillation axis X 2 −
The S-wave maximum energy axis lies in the direction orthogonal to X 2 . The water in the hole directly receives this asymmetric sound pressure P and transmits it to the hole wall, and the S wave propagates along the hole wall in the direction of the hole axis O-O. This S wave is transmitted to the first geophone 14 1 and the second geophone 14 2 via the borehole water,
Even if the S-wave displaces the hole wall and shakes the water in the hole, as shown in Figure 2, the 10 sondes have a large inertia due to their weights 10b, so the water in the hole moves. Therefore, it maintains a stationary state without interference. Therefore, the pair of piezoelectric sound receiving plates 19a and 19b of both sound receivers 14 1 and 14 2 are connected to the hole wall as shown in FIG. 1 because the wavelength of the S wave is sufficiently long compared to their size. It receives only the asymmetric sound pressure P due to relative acceleration motion. At this time, if the piezoelectric sound receiving plates 19a and 19b are electrically coupled in parallel as shown in FIG. 7, a voltage having a waveform corresponding to the propagated S wave is generated in the coupling circuit. Since the piezoelectric sound receiving plates 19a and 19b receive only the asymmetric sound pressure P in this way, they are not disturbed by tube waves or refracted waves between the hole wall and the water in the hole. Now, assuming that the acceleration on the hole wall is U¨, the pressure P acting on the piezoelectric vibration receiving plates 19a and 19b when they are assumed to be cylindrical is expressed by the following equation. P=-(m/2a)・U ¨ Here, m=πa 2・ρw However, a is the radius of the cylinder, and ρw is the density of water in the hole. On the other hand, as shown in FIG.
When a and 19b are coupled in series (at this time, both piezoelectric diaphragms 25a and 25b are also coupled in series),
A voltage with a waveform corresponding to the P wave is generated in the coupling circuit, and by switching the coupling polarity, it is possible to arbitrarily select and detect the S wave and the P wave. As a means for switching the polarity, the sonde 10 is equipped with a polarity switching circuit 26 that can be remotely controlled from the outside. Since the sonde 10 is equipped with two oscillators 13 1 and 13 2 above and below the two geophones 14 1 and 14 2 , measurement records of S waves or P based on the oscillations from the two oscillators can be recorded for each geophone. Through analysis, differences in characteristics between the two geophones can be removed, and the damping constant can be determined with high accuracy.
以上詳述したとおり本発明の測定装置によれば
次のような効果がある。
(1) 一対の圧電振動板を、ボーリング孔軸と直交
する単軸方向に分極方向を揃えてボーリング孔
内水中に浸漬した状態で発振させることによ
り、ボーリング孔軸と直交する方向に非対称音
圧を生じさせ、つまりボーリング孔内水に直接
に単軸発振による直接Ｓ波を生じさせ、その直
後Ｓ波を、一対の圧電振動板と同様にボーリン
グ孔軸と直交する単軸方向に分極方向を揃えて
ボーリング孔内水中に浸漬した一対の圧電受振
板で直接検知するため、Ｓ波検知に当たり、非
対称振動のみを検出できるため、Ｐ波やチユー
ブウエーブの擾乱の影響が少なく、Ｓ波を正確
に検知できる。従つて、地盤（岩盤）のＳ波速
度を正確に測定できるに加え、直接Ｓ波の振幅
比から地盤（岩盤）の減衰定数を精度よく測定
（算定）することができる。この減衰定数は耐
震設計上の重要な定数で、それが精度良く測定
できることの意義は大きい。
(2) 孔壁の変位による音圧を定位置に静止させた
圧電受振によつて検知するため、すなわちＳ波
の伝播による孔壁の横方向の音圧を、鉛直な孔
軸に対し不動にした圧電受振板によつて相対加
速度運動として検知するため、従来の直接波法
に比べて感度が良くなり、硬い地層でも精度良
く測定できる。
(3) 孔内水中に浸漬された一対の圧電受振板によ
るいわば直接単軸受振であるため、方式として
単純であり、解析が非常に簡単である。
(4) 一対の圧伝受振板の結合極性を切り換える極
性切換手段を備えているため、一対の圧電受振
板を並列結合したときは、Ｓ波の検知が行え、
また極性を切り換えて直列結合したときは、Ｐ
波を検知でき、Ｓ波検知とＰ波検知を簡単に選
択できる。
(5) 圧電受動板の特性上、高周波特性に優れてい
るため、発振周波数を変えることによつて軟弱
地層から硬岩まで広範囲に測定できる。
(6) 圧電受振板は低周波の振動に敏感なため、移
動しながら測定が可能となり、連続測定方式が
採れる。
As detailed above, the measuring device of the present invention has the following effects. (1) By oscillating a pair of piezoelectric diaphragms immersed in borehole water with the polarization direction aligned in a single axis direction perpendicular to the borehole axis, asymmetric sound pressure is generated in the direction perpendicular to the borehole axis. In other words, a direct S wave is generated directly in the borehole water by uniaxial oscillation, and immediately after that, the S wave is polarized in the uniaxial direction perpendicular to the borehole axis, similar to a pair of piezoelectric diaphragms. Since direct detection is performed using a pair of piezoelectric sound receiving plates that are aligned and immersed in water in a borehole, only asymmetrical vibrations can be detected when detecting S waves, so there is less influence from disturbances from P waves and tube waves, and S waves can be detected accurately. Can be detected. Therefore, in addition to accurately measuring the S-wave velocity of the ground (rock), it is also possible to accurately measure (calculate) the damping constant of the ground (rock) directly from the S-wave amplitude ratio. This attenuation constant is an important constant in seismic design, and it is of great significance that it can be measured accurately. (2) In order to detect the sound pressure caused by the displacement of the hole wall by using piezoelectric vibration receiver that is stationary in a fixed position, in other words, the sound pressure in the lateral direction of the hole wall due to the propagation of S waves is detected without moving with respect to the vertical hole axis. Because it detects relative acceleration motion using a piezoelectric sound plate, it has better sensitivity than the conventional direct wave method and can measure even hard strata with high accuracy. (3) Since it is a direct single-axis vibration receiving system using a pair of piezoelectric sound receiving plates immersed in the water inside the hole, the method is simple and analysis is very easy. (4) Since it is equipped with a polarity switching means for switching the coupling polarity of a pair of piezoelectric sound plates, when a pair of piezoelectric sound plates are coupled in parallel, S waves can be detected.
Also, when switching the polarity and connecting in series, P
Waves can be detected, and S wave detection and P wave detection can be easily selected. (5) Due to the characteristics of the piezoelectric passive plate, it has excellent high frequency characteristics, so by changing the oscillation frequency, it can measure a wide range of areas from soft strata to hard rocks. (6) Piezoelectric sound plates are sensitive to low-frequency vibrations, so measurements can be taken while moving, allowing continuous measurement.
第１図，，は本発明の測定装置の測定原
理を説明する説明図、第２図は孔壁の変位に対す
る受振器の関係を示す説明図、第３図は本発明の
装置の一使用例を示す説明図、第４図，第５図及
び第６図はゾンデの一部の縦断正面図、同側面図
及び横断図、第７図及び第８図は一対の圧電受振
板の電気的結合関係を示す説明図である。また、
第９図，は従来の屈折波法の説明図、第１０
図は孔壁固着型受振器による従来の直接波法の説
明図、第１１図は漂遊型受振器による従来の直接
波法の説明図、第１２図は従来の４極剪断波法の
説明図である。
１０……ゾンデ、１０ｂ……重錘、１３1・１
３2……発振器、１４1・１４2……受振器、１７
……取付孔、１８……導水孔、１９ａ・１９ｂ…
…一対の圧電受振板、２５ａ・２５ａ……一対の
圧電振動板、２６……極性切換回路。
Figures 1 and 2 are explanatory diagrams explaining the measurement principle of the measuring device of the present invention, Figure 2 is an explanatory diagram showing the relationship between the geophone and the displacement of the hole wall, and Figure 3 is an example of the use of the device of the present invention. Figures 4, 5 and 6 are longitudinal sectional front views, side views and cross-sectional views of a portion of the sonde, and Figures 7 and 8 are electrical connections between a pair of piezoelectric vibration plates. It is an explanatory diagram showing a relationship. Also,
Figure 9 is an explanatory diagram of the conventional refracted wave method;
Figure 11 is an illustration of the conventional direct wave method using a geophone fixed to the hole wall, Figure 11 is an illustration of the conventional direct wave method using a stray geophone, and Figure 12 is an illustration of the conventional 4-pole shear wave method. It is. 10...sonde, 10b...weight, 13 1.1
3 2 ... Oscillator, 14 1・14 2 ... Geophone, 17
...Mounting hole, 18...Water guide hole, 19a/19b...
...Pair of piezoelectric vibration receiving plates, 25a, 25a...Pair of piezoelectric vibration plates, 26...Polarity switching circuit.
Claims (1)
の外周壁に、少なくとも一対の対向する発振部取
付孔と、少なくとも一対の対向する受振部取付孔
とを上下に離して設けたこと、 一対の発振部取付孔の間のゾンデ内部及び一対
の受振部取付孔の間のゾンデ内部にそれぞれボー
リング孔内の流体を導入する導水部を設けたこ
と、 一対の発振部取付孔に、ゾンデの内外の液体に
浸漬される一対の圧電振動板２５ａ，２５ｂを、
ゾンデの軸線と直交する単軸に沿つて同方向に分
極しボーリング孔内の液体に直接Ｓ波を生じさせ
るように対向させて配置したこと、 一対の受振部取付孔に、ゾンデの内外の液体に
浸漬される一対の圧電受振板１９ａ，１９ｂを、
ゾンデの軸線と直交する単軸に沿つて同方向に分
極しボーリング孔内の液体からの直接Ｓ波を受振
できるように対向させて配置したこと、 ゾンデに、その慣性を大きくして上記一対の圧
電受振板をボーリング孔軸に対して不動するため
の重錘を設けたこと、 上記一対の圧電受振板の結合極性を切り換える
極性切換手段を備えたこと を特徴とする地下人工弾性波の測定装置。[Scope of Claims] 1. At least one pair of opposing oscillating part mounting holes and at least one pair of opposing vibration receiving part mounting holes are provided vertically apart from each other on the outer peripheral wall of a cylindrical sonde to be inserted into a borehole. that a water guide section for introducing the fluid in the borehole was provided inside the sonde between the pair of oscillating section mounting holes and inside the sonde between the pair of receiving section mounting holes, respectively; , a pair of piezoelectric diaphragms 25a and 25b immersed in liquid inside and outside the sonde,
The sonde is polarized in the same direction along a single axis perpendicular to the axis of the sonde, and the liquid inside and outside the sonde is placed so as to face each other so as to directly generate S waves in the liquid in the borehole. A pair of piezoelectric sound receiving plates 19a, 19b immersed in
The probes are polarized in the same direction along a single axis orthogonal to the axis of the sonde, and are placed facing each other so that they can receive direct S waves from the liquid in the borehole. An underground artificial acoustic wave measurement device, characterized in that a weight is provided to keep the piezoelectric sound plate immobile with respect to the borehole axis, and a polarity switching means is provided for switching the coupling polarity of the pair of piezoelectric sound plates. .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61240212A JPS6395379A (en) | 1986-10-11 | 1986-10-11 | Method and apparatus for measuring underground artificial elastic wave |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61240212A JPS6395379A (en) | 1986-10-11 | 1986-10-11 | Method and apparatus for measuring underground artificial elastic wave |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6395379A JPS6395379A (en) | 1988-04-26 |
| JPH055315B2 true JPH055315B2 (en) | 1993-01-22 |
Family
ID=17056119
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61240212A Granted JPS6395379A (en) | 1986-10-11 | 1986-10-11 | Method and apparatus for measuring underground artificial elastic wave |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6395379A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH067167B2 (en) * | 1988-04-18 | 1994-01-26 | 中央開発株式会社 | Sonde for measuring underground artificial elastic waves |
| JPH0616114B2 (en) * | 1988-08-19 | 1994-03-02 | サンコーコンサルタント株式会社 | Method and apparatus for measuring velocity of shear wave and compression wave in geological logging |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5923274A (en) * | 1982-07-06 | 1984-02-06 | エクソン・プロダクシヨン・リサ−チ・コムパニ− | Acoustic bipolar shear wave measuring device |
| JPS6216487B2 (en) * | 1979-08-31 | 1987-04-13 | Matsushita Electric Works Ltd |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6216487U (en) * | 1985-07-16 | 1987-01-31 |
-
1986
- 1986-10-11 JP JP61240212A patent/JPS6395379A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6216487B2 (en) * | 1979-08-31 | 1987-04-13 | Matsushita Electric Works Ltd | |
| JPS5923274A (en) * | 1982-07-06 | 1984-02-06 | エクソン・プロダクシヨン・リサ−チ・コムパニ− | Acoustic bipolar shear wave measuring device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6395379A (en) | 1988-04-26 |
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