JP3862595B2 - Measurement method of water permeability anisotropy of ground - Google Patents

Description

により鉛直方向の透水係数ｋ_ｖを求める段階と、
前記中空管をパッカーおよびその内側の土壌と共に引き抜いて、その跡に裸孔を形成し、ピエゾメーター法により前記裸孔の水平方向の透水係数を求める段階とから成ることを特徴とする。
【００１３】
請求項２に記載した発明に係る地盤の透水異方性の測定方法は、
地盤にボーリング孔を削孔し、該ボーリング孔にケーシングパイプを建込む段階と、
内壁面にパッカーを設けた中空管を前記ボーリング孔の底から直下の地盤中へ圧入し、前記パッカーを膨張させた後に、前記ケーシングパイプ内に設置した揚水ポンプで当該ボーリング孔内の地下水を揚水して水位を低下させ、その後揚水を停止して水圧の経時変化を前記中空管の上下両端部付近に設置した圧力センサで計測し、上下の圧力センサが計測した時刻ｔ_１，ｔ_２における水圧に基いて、次式
【数４】

により鉛直方向の透水係数ｋ_ｖを求める段階と、
前記中空管をパッカーおよび中空管内の土壌と共に引き抜いて、その跡に裸孔を形成し、ピエゾメーター法により前記裸孔の水平方向の透水係数を求める段階とから成ることを特徴とする。
【００１４】
請求項３記載の発明は、請求項１又は２に記載した地盤の透水異方性の測定方法において、
水平方向の透水係数を求める段階が終了した後に、裸孔の底面深度までケーシングパイプを挿入する段階と、
内壁面にパッカーを設けた中空管を前記裸孔の底から直下の地盤中へ圧入して、鉛直方向の透水係数ｋ_ｖを求める段階と、
前記中空管をパッカーおよび中空管内の土壌と共に引き抜いて、その跡に裸孔を形成し、ピエゾメーター法により前記裸孔の水平方向の透水係数を求める段階を繰り返し行うことを特徴とする。
【００１５】
【発明の実施の形態】
以下、図面を参照して請求項１〜３に記載した発明に係る地盤の透水異方性の測定方法について説明する。
図１Ａ〜Ｆは、請求項１に記載した発明の実施形態を概略的な手順で示している。
【００１６】
先ず、図１Ａは地盤にボーリング孔１０を削孔した段階を示し、続く図１Ｂは前記ボーリング孔１０にケーシングパイプ１を建込んで孔壁１０ａの保護と地下水の水平方向浸透流を遮断した段階を示す。
【００１７】
図１Ｃは、内壁面にパッカー４を設けた中空管２を前記ボーリング孔１０の底から直下の地盤中へ圧入した段階を示す。斯くして、前記中空管２によりその内側の土壌１１への水平方向浸透流が遮断され、鉛直方向透水係数の試験区間が形成される。
【００１８】
前記中空管２の外径は、前記ケーシングパイプ１の内径と略同径である。また、この中空管２の上下両端の周縁部付近には、それぞれ試験区間の上下における各地下水の水圧をそれぞれ計測する圧力センサ３，３が設けられている。
【００１９】
図１Ｄは、鉛直方向の透水試験の段階を示す。
この段階では、先ず、前記パッカー４を液圧（水圧）又はガス圧（空気圧）にて適度に膨張させ、中空管２の内壁面とその内側の土壌１１との境界部に発生しがちの「水みち」を完全に遮断する。しかる後に、所謂「定常法」に則り、前記ケーシングパイプ１内に設置した揚水ポンプ６でボーリング孔１０内の地下水を一定の揚水量Ｑで揚水し、中空管２内の土壌１１を乱すことなく試験区間の土壌１１に対して鉛直方向の浸透流を発生させる。なお、前記揚水ポンプ６によって汲み上げられる地下水の揚水量Ｑは、地上に設置された計測システム（図示せず）により観測し記録される。
【００２０】
斯くして、上記した浸透流を発生させた状態の下において、圧力センサ３，３で試験区間の上下のおける各水圧を計測し、その計測信号はケーブル（図示せず）を介して前記計測システムへ送信し、観測・記録される。
【００２１】
前記揚水量Ｑおよび上下の圧力センサ３，３が計測した試験区間の上下における各地下水の水圧に基いて、次式
【００２２】
【数５】

により鉛直方向の透水係数ｋ_ｖを求める。前記水頭差Δｈは、圧力センサ３，３が計測した試験区間、即ち中空管２の上下両端部の各水圧を基に求める。
【００２３】
因みに、上記［数１］の計算は前記計測システムにより自動的に算出される。また、中空管２の長さＬおよび中空管２内の土壌１１の透水断面積Ａの数値は、既知量として予め計測システムへデータ入力を行い設定する。
なお、上記［数１］の計算は、前記計測システムによる算出に限定されず、人の手作業によって算出しても好適に実施できる。
【００２４】
次に図１Ｅは、中空管２をパッカー４および中空管２内の土壌１１と共に引き抜いてその跡に裸孔５を形成した段階を示す。この水平方向透水係数の試験区間となる裸孔５では、水平方向の浸透流が鉛直方向の浸透流を無視できるほどに支配的になり、水平方向の透水係数ｋ_ｈの測定に適した状態となる。
【００２５】
図１Ｆは、ピエゾメーター法を用いて前記裸孔５における水平方向の透水係数ｋ_ｈを求める段階を示す。なお、このピエゾメータ法の透水試験は、地盤工学会発行の「地盤調査法」に沿って「定常法」又は「非定常法」のいずれかの方法で実施する。ここで、前記「地盤調査法」に記載されている透水係数は、水平・鉛直の両方の影響を含んだ平均的な透水係数であるが、上述したように、地盤が層構造を成していることと、裸孔５の形状の縦横比より、水平方向の透水係数が支配的になるため、ピエゾメータ法による透水係数を水平方向の透水係数（水平透水係数）としている。
【００２６】
斯くして、前記土壌１１が属する地盤層についての透水異方性の測定は終了する。
【００２７】
図２Ｇ〜Ｉは、以上に説明した請求項１記載の発明を実施した後に、更に連続して裸孔５の底から直下の土壌１２の透水異方性を測定する手順の一部を概略的に示している。
図２Ｇは、図１Ｆに示した前記裸孔５における水平方向の透水係数を求める段階が終了した直後の状態を示す。
【００２８】
図２Ｈは、前記裸孔５の底面深度までケーシングパイプ１を挿入し、裸孔５の孔壁５ａを保護すると共に前記孔壁５ａからの浸透流を遮断する段階を示す。ケーシングパイプ１を挿入する際には、図２に示すようにケーシング材１’を前記ケーシングパイプ１の上端部へ継ぎ足し、ボーリング孔１０の上部に土壌がむき出しになった裸孔部位を生じないようにする。前記ケーシング材１’には、前記裸孔５の深さＬ以上の長さのパイプが好適に使用される。
【００２９】
次に図２Ｉは、内壁面にパッカー４を設けた中空管２を前記裸孔跡の底から直下の地盤中へ圧入する段階を示す。
【００３０】
その後、前記図２Ｉの段階が終了した後に、請求項１に記載した発明の手法（定常法）または後述する請求項２に記載した発明の手法（非定常法）により鉛直方向の透水係数ｋ_ｖを求める上記図１Ｄまたは後記図３Ｄに示す段階と同様の処理が実施される。続いて、前記中空管２をパッカー４および中空管２内の土壌１２と共に引き抜き、その跡に裸孔を形成してピエゾメーター法により前記裸孔の水平方向の透水係数を求める上記図１Ｅおよび図１Ｆに示す段階と同様の処理が実施される（以上、請求項３記載の発明）。
【００３１】
斯くして、ボーリング孔１０に沿った鉛直方向に連続的な地盤の透水異方性の測定が可能となる。つまり、最初に掘削したボーリング孔の深さに限定されることなく、自由に所望深度の地盤まで連続的に透水異方性が測定可能となる。
【００３２】
次に図３Ａ〜Ｆは、請求項２に記載した発明の実施形態を概略的な手順で示している。なお、請求項１に記載した地盤の透水異方性の測定方法と共通する部分は説明を省略する。
【００３３】
図３Ａ〜Ｃは、上記請求項１記載の発明の手順を示した図１Ａ〜Ｃの段階と同様に実施されるため、上記のとおり説明は省略する。
【００３４】
図３Ｄは、鉛直方向の透水試験の段階を示す。
この段階では、先ず、前記パッカー４に液圧（水圧）又はガス圧（空気圧）で適度に膨張させ、中空管２の内壁面とその内側の土壌１４との境界部に発生しがちの「水みち」を完全に遮断する。
【００３５】
その後、所謂「非定常法」に則り、前記ボーリング孔１０内に設置した揚水ポンプ６で地下水を揚水して水位を一旦低下させ、その後、揚水を停止し、中空管２内の土壌１４を乱すことなく試験区間の土壌１４に対して鉛直方向の浸透流を発生させる。そして、しかる後にボーリング孔１０内の水圧の経時変化を前記中空管２の上下両端部付近に設置した圧力センサ３，３で計測し、その計測信号はケーブル（図示せず）を介して地上に設置した計測システム（図示せず）へ送信され、観測し記憶される。
【００３６】
その後、上下の圧力センサが計測した任意の時刻ｔ_１，ｔ_２における水圧に基いて、次式
【００３７】
【数６】

により鉛直方向の透水係数ｋ_ｖを求める。各時刻ｔ_１，ｔ_２における水頭差Δｈ_１ ，Δｈ_２は、前記時刻ｔ_１，ｔ_２に中空管２の上下端部に設けた圧力センサ３，３が計測した各水圧を基に求める。
【００３８】
因みに、前記［数２］の計算は、前記計測システムにより自動的に算出される。また、中空管２の長さＬおよび中空管２内の土壌１１の透水断面積Ａの数値は、既知量として予め計測システムへデータ入力を行い設定する。
なお、上記［数２］の計算は、前記計測システムによる算出に限定されず、人の手作業によって算出しても好適に実施できる。
【００３９】
図３Ｅおよび図３Ｆは、上記した請求項１記載の発明における図１Ｅおよび図１Ｆの段階と同様の処理が実施され、前記土壌１４が属する地盤層の透水異方性の測定は終了する。
【００４０】
また、本実施形態について、ボーリング孔１０に沿った鉛直方向に連続的な地盤の透水異方性の測定は、上記した請求項１記載の発明と同様の手法により実施できる。即ち、前記図３Ｆに示す段階の後に上記図２Ｈおよび図２Ｉに示す段階と同様の処理を実施し、その後前記図３Ｄ〜Ｆに示す段階の処理を実施して目的地盤の透水異方性を測定する。
【００４１】
以上に説明したように、請求項１〜３に記載した発明に係る透水異方性の測定方法によれば、簡単な工程作業と簡単な計算とで地盤の透水異方性を測定することができる。
また、測定施設が従来に比べ小規模で済むので、コストを大幅に低減することができる。
【００４２】
加えて、同じ孔にて一連の順序で水平方向の透水係数（ｋ_ｈ）と鉛直方向の透水係数（ｋ_ｖ）を測定し地盤の透水異方性を測定できるので、地下水対策における遮水壁の合理的な設計が可能となり、延いては遮水壁の根入れ長さの低減による原価低減と工期短縮が図れる。更に、遮水壁外側の地下水評価による周辺地下水環境負荷の低減を考慮した揚水計画も立案できる。
【００４３】
そして、最初に掘削したボーリング孔の深さに限定されることなく、自由に所望深度の地盤まで連続的に透水異方性を測定できる。
【００４４】
以上には本発明の好適な実施形態を説明したが、本発明の実施形態以外にも、本発明の要旨を逸脱することなく、当業者が通常行う種々の応用、変更による実施も可能であることを付言する。例えば、中空管を地盤に挿入する手段として、下端の縁周部にビットを装備した中空管を用いて回転による掘削貫入させても好適に実施可能である。
【００４５】
【本発明が奏する効果】
本発明に係る請求項１〜３に記載した地盤の透水異方性の測定方法によれば、簡単且つ安価に地盤の水平方向の透水係数および鉛直方向の透水係数を求め、透水異方性を調査することができる。
【００４６】
更に、最初に掘削したボーリング孔の深さに限定されることなく、自由に所望深度の地盤まで連続的に透水異方性を測定できる。
【００４７】
また、同じ孔にて一連の順序で水平方向の透水係数と鉛直方向の透水係数を測定し地盤の透水異方性を測定できるので、地下水対策における遮水壁の合理的な設計が可能となり、延いては遮水壁の根入れ長さの低減による原価低減と工期短縮が図れる。更に、遮水壁外側の地下水評価による周辺地下水環境負荷の低減を考慮した揚水計画も立案できる。
【図面の簡単な説明】
【図１】Ａ〜Ｆは、請求項１に記載した発明の概略的な手順を示す説明図である。
【図２】Ｇ〜Ｉは、ボーリング孔に沿った鉛直方向に連続的な地盤の透水異方性の測定方法の手順の一部を概略的に示す説明図である。
【図３】Ａ〜Ｆは、請求項２に記載した発明の概略的な手順を示す説明図である。
【符号の説明】
１０ ボーリング孔
１ ケーシングパイプ
４ パッカー
２ 中空管
６ 揚水ポンプ
３ 圧力センサ
５ 裸孔
１０ａ，５ａ 孔壁
１１，１２，１４ 土壌
ｋ_ｖ 鉛直透水係数（鉛直方向の透水係数）
Ｌ 中空管の長さ
Δｈ 水頭差
Ｑ 揚水量
Ａ 中空管内の土壌の透水断面積
ｔ_１，ｔ_２ 時刻
Δｈ_１ 時刻ｔ_１における水頭差
Δｈ_２ 時刻ｔ_２における水頭差[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of the method of measuring the hydraulic conductivity of the in-situ ground, and more specifically, is a single-hole permeability test, in which the horizontal and vertical hydraulic conductivity of the in-situ ground are respectively determined. The present invention relates to a method for measuring the permeability anisotropy of the ground.
[0002]
[Prior art]
In general, since natural ground has a layered structure, there are many grounds with so-called “permeability anisotropy” in which the horizontal hydraulic conductivity (k _h ) and the vertical hydraulic conductivity (k _v ) are different. .
[0003]
Conventional methods for measuring the hydraulic conductivity of the ground in situ include single-hole permeability tests such as the tube method, piezometer method, auger method and packer method, and porous methods such as the Theis method and the Jacob method. Pumping tests are being conducted.
However, in each of these measurement methods, the water permeability coefficient in the horizontal direction is dominant, and the water permeability coefficient in the vertical direction cannot be evaluated.
[0004]
In such a situation, various methods for evaluating the horizontal hydraulic conductivity and the vertical hydraulic conductivity, that is, the method of measuring “water permeability anisotropy” have been studied. For example,
(1) Japanese Patent No. 2796748 discloses an example of a single hole type water permeability test for measuring water permeability anisotropy around a single bore hole. The present invention alternately installs a plurality of packers and pressure sensors in the depth direction of the borehole, generates a fluctuating water pressure (osmotic flow) by water injection from one packer section, and sets the response water pressure propagating into the ground to the other Measured with a pressure sensor installed in the packer section, and based on the measurement results, numerical analysis was performed using a cylindrical coordinate system permeability distribution model to determine the horizontal and vertical hydraulic conductivity of the ground, and the permeability anisotropy of the ground Is a method of measuring.
[0005]
(2) Japanese Patent No. 2788954 discloses an example of a porous pumping test for measuring water permeability anisotropy in the entire area around the borehole. The invention provides a pumping well and an observation well provided with a screen part and a blind pipe part by a casing material and a filler, and further provided with a water stop device for blocking water flow between the screen parts. The groundwater is pumped up from the ground, and the fluctuation of the water pressure is generated in the ground aquifer.The water pressure fluctuation is measured with the water pressure gauges of all the screens of the observation well, and the horizontal and vertical hydraulic conductivity is obtained. This is a method for measuring water permeability anisotropy.
[0006]
[Problems to be solved by the present invention]
However, since the technique (1) employs a numerical analysis based on a complicated cylindrical coordinate system permeability distribution model to calculate the hydraulic conductivity in the horizontal and vertical directions, it must be performed by those who do not have expertise in the numerical analysis. There is a problem that it cannot be done and is not versatile. Further, there is a problem that the permeability test section of the ground is limited to the depth of the first drilled borehole.
[0007]
On the other hand, the technique (2) has a problem that the measurement facility becomes large-scale because of excavation of a plurality of boring holes and the permeability anisotropy is measured, and the labor and cost of the work increase.
[0008]
In addition, the porous pumping test as in the technique (2) requires complicated numerical analysis when evaluating the permeability anisotropy. For this reason, there is a problem that it cannot be carried out unless it is a person who has expertise in numerical analysis, and the versatility is poor.
[0009]
Furthermore, the technique of (2) does not require the problem that the test section of the permeability coefficient of the ground is limited to the depth of the bored hole first drilled or continuous permeability in the depth direction of the borehole. There's a problem.
[0010]
That is, the techniques (1) and (2) are both i) a complicated method requiring complicated numerical analysis, ii) the cost required for the water permeability test is increased, and iii) the test section is a borehole. It cannot be a general means for measuring the permeability anisotropy of the ground because of limited depth.
[0011]
The object of the present invention is to provide a method for measuring the permeability anisotropy of the ground, which solves the above-mentioned problems and can determine the hydraulic permeability coefficient in the horizontal direction and the vertical permeability coefficient of the ground easily and inexpensively. It is in.
[0012]
[Means for Solving the Problems]
As a means for solving the problems of the conventional technology described above, the method for measuring the permeability anisotropy of the ground according to the invention described in claim 1 is:
Drilling a borehole in the ground, and building a casing pipe in the borehole;
A hollow tube provided with a packer on the inner wall surface is press-fitted into the ground immediately below from the bottom of the boring hole, and after the packer is expanded, groundwater in the boring hole is drained by a pumping pump installed in the casing pipe. The water is pumped at a constant pumping amount, and the water pressure is measured by pressure sensors installed near the upper and lower ends of the hollow tube. Based on the pumping amount and the water pressure measured by the upper and lower pressure sensors,

And determining a vertical permeability k _v a,
The hollow tube is pulled out together with the packer and the soil inside thereof, and a bare hole is formed in the trace, and a horizontal water permeability coefficient of the bare hole is obtained by a piezometer method.
[0013]
The method for measuring the permeability anisotropy of the ground according to the invention described in claim 2 is:
Drilling a borehole in the ground, and building a casing pipe in the borehole;
A hollow tube provided with a packer on the inner wall surface is press-fitted into the ground immediately below from the bottom of the boring hole, and after the packer is expanded, groundwater in the boring hole is drained by a pumping pump installed in the casing pipe. The water level is lowered by pumping water, and then the pumping is stopped, and the time change of the water pressure is measured by pressure sensors installed near the upper and lower ends of the hollow tube, and the times t ₁ and t ₂ measured by the upper and lower pressure sensors are measured. Based on the water pressure in the following formula:

And determining a vertical permeability k _v a,
The hollow tube is pulled out together with the packer and the soil in the hollow tube, a bare hole is formed in the trace, and a horizontal water permeability coefficient of the bare hole is obtained by a piezometer method.
[0014]
Invention of Claim 3 is the measuring method of the water permeability anisotropy of the ground described in Claim 1 or 2,
After the step of obtaining the horizontal hydraulic conductivity is completed, inserting the casing pipe to the bottom depth of the bare hole;
A step of press-fitting a hollow tube provided with a packer on the inner wall surface into the ground immediately below from the bottom of the bare hole to obtain a vertical permeability coefficient k _v ;
The hollow tube is pulled out together with the packer and the soil in the hollow tube, a bare hole is formed in the trace, and a step of obtaining a horizontal water permeability coefficient of the bare hole by a piezometer method is repeatedly performed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method for measuring the water permeability anisotropy of the ground according to the first to third aspects of the invention will be described with reference to the drawings.
1A to F show an embodiment of the invention described in claim 1 in a schematic procedure.
[0016]
First, FIG. 1A shows a stage in which a boring hole 10 is drilled in the ground, and subsequent FIG. 1B shows a stage in which a casing pipe 1 is built in the boring hole 10 to protect the hole wall 10a and to prevent horizontal seepage flow of groundwater. Indicates.
[0017]
FIG. 1C shows a stage in which the hollow tube 2 provided with the packer 4 on the inner wall surface is press-fitted from the bottom of the boring hole 10 into the ground immediately below. Thus, the hollow tube 2 blocks the horizontal osmotic flow into the soil 11 inside the hollow tube 2 and forms a test section with a vertical hydraulic conductivity.
[0018]
The outer diameter of the hollow tube 2 is substantially the same as the inner diameter of the casing pipe 1. In addition, pressure sensors 3 and 3 for measuring the water pressures of the groundwater in the upper and lower portions of the test section are provided in the vicinity of the peripheral portions of the upper and lower ends of the hollow tube 2.
[0019]
FIG. 1D shows the stage of the vertical permeability test.
At this stage, first, the packer 4 is appropriately expanded by hydraulic pressure (water pressure) or gas pressure (air pressure), and tends to be generated at the boundary between the inner wall surface of the hollow tube 2 and the soil 11 inside thereof. Completely cut off the “water path”. Thereafter, in accordance with the so-called “steady state method”, the groundwater in the borehole 10 is pumped at a constant pumping amount Q by the pump 6 installed in the casing pipe 1 to disturb the soil 11 in the hollow tube 2. Without generating an osmotic flow in the vertical direction with respect to the soil 11 in the test section. The amount Q of groundwater pumped up by the pump 6 is observed and recorded by a measurement system (not shown) installed on the ground.
[0020]
Thus, under the state in which the osmotic flow is generated, the water pressures above and below the test section are measured by the pressure sensors 3 and 3, and the measurement signal is measured via a cable (not shown). It is transmitted to the system and observed and recorded.
[0021]
Based on the amount of pumped water Q and the water pressure of each groundwater above and below the test section measured by the upper and lower pressure sensors 3 and 3, the following equation:
[Equation 5]

Request vertical permeability k _v a. The water head difference Δh is obtained based on the test sections measured by the pressure sensors 3, 3, that is, the water pressures at the upper and lower ends of the hollow tube 2.
[0023]
Incidentally, the calculation of the above [Equation 1] is automatically calculated by the measurement system. The numerical value of the length L of the hollow tube 2 and the cross-sectional area A of the soil 11 in the hollow tube 2 is set by inputting data to the measurement system in advance as a known amount.
Note that the calculation of the above [Equation 1] is not limited to the calculation by the measurement system, and can be suitably carried out even if it is calculated manually.
[0024]
Next, FIG. 1E shows a stage in which the hollow tube 2 is pulled out together with the packer 4 and the soil 11 in the hollow tube 2 to form a bare hole 5 at the trace. In bare hole 5 becomes the horizontal permeability of the test period, the state in which the horizontal flow dominant becomes negligible in the vertical direction of flow, suitable for measuring horizontal permeability k _h Become.
[0025]
Figure 1F shows a step of determining a horizontal permeability k _h in the open hole 5 with a piezometer method. In addition, the permeability test of this piezometer method is carried out by either “steady method” or “unsteady method” in accordance with “Ground Survey Method” published by the Geotechnical Society. Here, the hydraulic conductivity described in the “Ground Survey Method” is an average hydraulic conductivity including both horizontal and vertical effects. As described above, the ground has a layered structure. Since the horizontal permeability coefficient is more dominant than the aspect ratio of the shape of the bare hole 5, the permeability coefficient by the piezometer method is set as the horizontal permeability coefficient (horizontal permeability coefficient).
[0026]
Thus, the measurement of water permeability anisotropy for the ground layer to which the soil 11 belongs is completed.
[0027]
2G to I schematically illustrate a part of the procedure for continuously measuring the permeability anisotropy of the soil 12 immediately below the bottom of the bare hole 5 after implementing the invention according to claim 1 described above. It shows.
FIG. 2G shows a state immediately after the step of obtaining the horizontal hydraulic conductivity in the bare hole 5 shown in FIG. 1F is completed.
[0028]
FIG. 2H shows a step of inserting the casing pipe 1 to the depth of the bottom surface of the bare hole 5 to protect the hole wall 5a of the bare hole 5 and to block the permeation flow from the hole wall 5a. When the casing pipe 1 is inserted, as shown in FIG. 2, the casing material 1 ′ is added to the upper end of the casing pipe 1 so as not to form a bare hole portion where soil is exposed at the upper portion of the boring hole 10. To. A pipe having a length equal to or greater than the depth L of the bare hole 5 is preferably used for the casing material 1 ′.
[0029]
Next, FIG. 2I shows a step of press-fitting the hollow tube 2 provided with the packer 4 on the inner wall surface from the bottom of the bare hole trace into the ground immediately below.
[0030]
Thereafter, after the step of FIG. 2I is completed, the vertical hydraulic conductivity k _{v is} obtained by the method of the invention described in claim 1 (steady method) or the method of the invention described in claim 2 described later (unsteady method). The same processing as that shown in FIG. 1D or FIG. 3D described later is performed. Subsequently, the hollow tube 2 is pulled out together with the packer 4 and the soil 12 in the hollow tube 2, a bare hole is formed in the trace, and the horizontal permeability coefficient of the bare hole is obtained by the piezometer method. And the process similar to the step shown to FIG. 1F is implemented (above, invention of Claim 3).
[0031]
In this way, it is possible to measure the water permeability anisotropy of the ground continuously in the vertical direction along the borehole 10. In other words, the permeability anisotropy can be continuously measured freely up to the ground at a desired depth without being limited to the depth of the first drilled borehole.
[0032]
3A to F show an embodiment of the invention described in claim 2 in a schematic procedure. In addition, description is abbreviate | omitted about the part which is common in the measuring method of the water permeability anisotropy of the ground described in Claim 1.
[0033]
3A to 3C are carried out in the same manner as the stage of FIGS. 1A to 1C showing the procedure of the invention according to the first aspect, and thus the description thereof is omitted as described above.
[0034]
FIG. 3D shows the stage of the vertical permeability test.
In this stage, first, the packer 4 is appropriately expanded by hydraulic pressure (water pressure) or gas pressure (pneumatic pressure) and is generated at the boundary between the inner wall surface of the hollow tube 2 and the soil 14 inside thereof. Completely cut off the water path.
[0035]
Thereafter, in accordance with the so-called “unsteady method”, the groundwater is pumped up by the pump 6 installed in the borehole 10 to lower the water level once, and then the pumping is stopped to remove the soil 14 in the hollow tube 2. An osmotic flow in the vertical direction is generated with respect to the soil 14 in the test section without being disturbed. After that, the time-dependent change in the water pressure in the borehole 10 is measured by pressure sensors 3 and 3 installed near the upper and lower ends of the hollow tube 2, and the measurement signal is transmitted to the ground via a cable (not shown). Is transmitted to a measurement system (not shown) installed in and observed and stored.
[0036]
After that, based on the water pressure at arbitrary times t ₁ and t ₂ measured by the upper and lower pressure sensors,
[Formula 6]

Request vertical permeability k _v a. Each time _t 1, _the water head difference in _{t 2} Delta] h _1, Delta] h ₂ obtains based on each pressure where the time _t 1, _{t 2} the pressure sensor 3, 3 provided on a lower end portion of the hollow tube 2 is measured .
[0038]
Incidentally, the calculation of [Expression 2] is automatically calculated by the measurement system. The numerical value of the length L of the hollow tube 2 and the cross-sectional area A of the soil 11 in the hollow tube 2 is set by inputting data to the measurement system in advance as a known amount.
Note that the calculation of the above [Equation 2] is not limited to the calculation by the measurement system, and can be suitably carried out even if it is calculated manually.
[0039]
In FIGS. 3E and 3F, the same processing as that in FIGS. 1E and 1F in the first aspect of the invention described above is performed, and the measurement of the hydraulic anisotropy of the ground layer to which the soil 14 belongs is completed.
[0040]
Moreover, about this embodiment, the measurement of the water permeability anisotropy of the ground continuous along the boring hole 10 in the vertical direction can be performed by the same method as that of the first aspect of the present invention. That is, after the step shown in FIG. 3F, the same processing as the step shown in FIGS. 2H and 2I is performed, and then the steps shown in FIGS. taking measurement.
[0041]
As described above, according to the method for measuring water permeability anisotropy according to the first to third aspects of the invention, it is possible to measure the water permeability anisotropy of the ground with simple process work and simple calculation. it can.
In addition, since the measurement facility is smaller than conventional ones, the cost can be greatly reduced.
[0042]
In addition, it is possible to measure the permeability anisotropy of the measured soil the permeability in the horizontal direction in the sequential order at the same hole (k _h) and vertical permeability (k _v), impervious wall in groundwater protection As a result, the cost can be reduced and the construction period can be shortened by reducing the penetration length of the impermeable wall. Furthermore, a pumping plan that takes into account the reduction of the environmental load of the surrounding groundwater can be made by evaluating the groundwater outside the impermeable wall.
[0043]
And, it is not limited to the depth of the first drilled borehole, and the permeability anisotropy can be measured continuously and freely up to the ground at a desired depth.
[0044]
The preferred embodiments of the present invention have been described above. However, other than the embodiments of the present invention, various applications and modifications usually performed by those skilled in the art are possible without departing from the spirit of the present invention. I will add that. For example, as a means for inserting the hollow tube into the ground, it is possible to suitably carry out the excavation penetration by rotation using a hollow tube equipped with a bit at the peripheral edge of the lower end.
[0045]
[Effects of the present invention]
According to the method for measuring the hydraulic permeability anisotropy of the ground according to claims 1 to 3 according to the present invention, the horizontal hydraulic permeability coefficient and the vertical hydraulic permeability coefficient of the ground are obtained easily and inexpensively, and the hydraulic permeability anisotropy is determined. Can be investigated.
[0046]
In addition, the permeability anisotropy can be measured continuously and freely up to the desired depth without being limited to the depth of the first drilled borehole.
[0047]
In addition, since the horizontal permeability coefficient and the vertical permeability coefficient can be measured in the same hole in a series of steps and the permeability anisotropy of the ground can be measured, rational design of the impermeable wall for groundwater countermeasures becomes possible. As a result, the cost can be reduced and the construction period can be shortened by reducing the length of the impermeable wall. Furthermore, a pumping plan that takes into account the reduction of the environmental load of the surrounding groundwater can be made by evaluating the groundwater outside the impermeable wall.
[Brief description of the drawings]
FIGS. 1A to 1F are explanatory views showing a schematic procedure of the invention described in claim 1; FIGS.
FIGS. 2A to 2I are explanatory views schematically showing a part of a procedure of a method for measuring the permeability anisotropy of a ground continuous along a boring hole in a vertical direction. FIGS.
FIGS. 3A to 3F are explanatory views showing a schematic procedure of the invention described in claim 2; FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Boring hole 1 Casing pipe 4 Packer 2 Hollow pipe 6 Pumping pump 3 Pressure sensor 5 Bare hole 10a, 5a Hole wall 11, 12, 14 Soil k _v Vertical permeability coefficient (Vertical permeability coefficient)
L Length of hollow tube Δh Water head difference Q Pumping amount A Water cross section of soil in hollow tube t ₁ , t ₂ Time Δh ₁ Water head difference at time t ₁ Δh ₂ Water head difference at time t ₂

Claims (3)

Drilling a borehole in the ground, and building a casing pipe in the borehole;
A hollow tube provided with a packer on the inner wall surface is press-fitted into the ground immediately below from the bottom of the boring hole, and after the packer is expanded, groundwater in the boring hole is drained by a pumping pump installed in the casing pipe. Water is pumped at a constant pumping amount, and the water pressure is measured by pressure sensors installed near the upper and lower ends of the hollow tube. Based on the pumping amount and the water pressure measured by the upper and lower pressure sensors,

And determining a vertical permeability k _v a,
The hollow pipe is pulled out together with the packer and the soil inside thereof, a bare hole is formed in the trace, and a horizontal permeability coefficient of the bare hole is obtained by a piezometer method. Of measuring water permeability anisotropy. Drilling a borehole in the ground, and building a casing pipe in the borehole;
A hollow tube provided with a packer on the inner wall surface is press-fitted into the ground immediately below from the bottom of the boring hole, and after the packer is expanded, groundwater in the boring hole is drained by a pumping pump installed in the casing pipe. The water level is lowered by pumping water, and then the pumping is stopped, and the time change of the water pressure is measured by pressure sensors installed near the upper and lower ends of the hollow tube, and the times t ₁ and t ₂ measured by the upper and lower pressure sensors are measured. Based on the water pressure at

And determining a vertical permeability k _v a,
The hollow pipe is pulled out together with the packer and the soil in the hollow pipe, a bare hole is formed in the trace, and a horizontal permeability coefficient of the bare hole is obtained by a piezometer method. Of measuring water permeability anisotropy. After the step of obtaining the horizontal hydraulic conductivity is completed, inserting the casing pipe to the bottom depth of the bare hole;
A step of press-fitting a hollow tube provided with a packer on the inner wall surface into the ground immediately below from the bottom of the bare hole to obtain a vertical permeability coefficient k _v ;
The hollow tube is pulled out together with the packer and the soil in the hollow tube, a bare hole is formed in the trace, and a step of obtaining a horizontal water permeability coefficient of the bare hole by a piezometer method is repeatedly performed. Item 3. The method for measuring the water permeability anisotropy of the ground described in Item 1 or 2.

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