JPS6236086B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for investigating grout injection conditions. Generally, it is extremely difficult to know the amount of grout to be injected into the surrounding ground, the location of the grout, etc. Therefore, in the past, it was customary to investigate the soil quality of the target ground and determine it empirically by determining how much grout was injected through the injection pipe. However, with this method, rational injection cannot be expected at all, and there are also problems in terms of reliability and economy. This invention was proposed in view of the above-mentioned conventional problems, and its characteristics are that the grouting pipe is inserted into the injection hole of the grouting pipe drilled in a predetermined ground, and the grouting pipe or the surrounding ground is A measuring line for resistivity measurement having a plurality of electrodes is installed at The purpose of this method is to detect how the resistance changes with the injection position of the grout and the time of injection, and to investigate the state of grout injection into the surrounding ground of the exploration target. Here, to explain the resistivity electric survey in advance, there are two types of measurement methods. The ground resistance method uses two electrodes (FIG. 1a), and the resistivity measurement method uses four electrodes (FIG. 1b). The former measures the ground resistance of an electrode, and is a local measurement method that is strongly influenced by the resistivity of underground structures near the electrode. In the latter case, as shown in Fig. 1b, by distinguishing between two current electrodes C ₁ and C ₂ and two potential electrodes P ₁ and P ₂ , the influence of the ground resistance of each electrode is removed. This method can measure the resistivity of a spread underground structure, but the measured resistivity is an average value of the resistivity of a spread underground structure, and it is difficult to know which part of the underground structure it corresponds to. Not clear. Therefore, this average resistivity is called "apparent resistivity." In the past, various attempts have been made to determine the change in apparent resistivity over time and to understand the grout injection status (for example,
-93299 Publication). However, this apparent resistivity is not unique to the underground structure, but is related to the electrode arrangement, electrode spacing, and relative position of the electrode arrangement and the underground structure. It is considered that the resistivity of a "homogeneous" underground structure is one that gives the same resistivity as the underground structure. Based on this background, the inventor of the present application divided the ground to be surveyed into unit volumes based on the electrode spacing for a certain set width, and calculated the volume of each unit based on the simulation using an underground structure model and the apparent resistivity measured on-site. We studied the specific resistance in volume and came up with the idea of using this to investigate the grout injection situation. Hereinafter, the present invention will be explained in detail based on the drawings. 2 and 3, an insertion hole 2 for a grout injection pipe is bored in a predetermined ground 1, and an injection pipe 3 is inserted into this insertion hole 2. On the surface and underground of the surrounding ground 1, resistivity measuring lines 4, 4' having a plurality of electrodes e are arranged horizontally or vertically. It is also possible to insert into the insertion hole 2 an injection measuring tube (FIG. 5) in which a measuring line 4' is attached to the injection tube 3 itself. The survey lines 4, 4' are arranged by drilling holes for burial as necessary. The number of survey lines and wiring positions are selected as appropriate, taking into consideration the accuracy of the survey. Next, regarding the measurement of specific resistance (apparent specific resistance) at the site, a measurement method using one specific measuring line 4 will be considered. This survey line 4 has a predetermined width b on both sides.
It has a measurement area that extends in the vertical direction, and a unit volume B is defined by dividing this measurement area vertically and horizontally based on the electrode spacing a, and the measurement area can be regarded as an aggregate of these. . In addition,
The width b in FIG. 2 corresponds to the spacing between adjacent survey lines 4, and in the example of this figure is equal to the electrode spacing a (b=a). Now, connect C ₁ , P ₁ , P ₂ , C ₂ shown in Fig. 1b to the four electrodes e on the left end of one measuring line 4, and draw current from the two current electrodes C ₁ and C ₂ . pass a current,
The potential V between two potential electrodes P ₁ and P ₂ is measured.
Here, if the spacing between the electrodes is a, then ρa=2π
The apparent resistivity aV/I is defined. Next, these four electrodes C ₁ , P ₁ , P ₂ , C ₂ are connected to 1
Shift them to the right one by one and connect them to electrode e on measuring line 4,
As mentioned above, the current between the current electrodes and the potential between the potential electrodes are measured, and the corresponding apparent resistivity ρ is calculated.
_a is obtained. Furthermore, if the electrode spacing becomes 2a,
The apparent resistivity ρ _a =2π(2a)V/I. In addition to CPPC, the electrode arrangement includes CCPP and CPCP, and the electrode spacing does not have to be equal, and the apparent resistivity ρ _a is measured for each. The apparent resistivity _ρa measured in this way is similar to the surrounding ground measurement and the underground structure model such as the resistance network model shown in Japanese Patent Application No. 44-29166 (see Japanese Patent Publication No. 56-34837). _Express the survey _line of By iteratively correcting the volume resistivity _u , the resistivity _u of each unit volume of the resistance network model will approximate the resistivity ρ _u of each unit volume of the surrounding ground. A similar resistance network model is also shown in Japanese Patent Publication No. 36-14901, and can be confirmed experimentally. Note that this simulation can also be performed by randomly changing the specific resistance _u of each unit volume, but for example,
54-89901), the apparent resistivity _{ρ a} obtained from various electrode arrangements and the resistivity _u of each unit volume are related in the form of an equation by approximation, and the resistivity can be easily obtained. Measurements can be made in the same way for the vertical line 4', and by setting the horizontal direction as the first line 4 and the vertical line as the second line 4', the specific resistance ρ _u of each unit volume can be calculated from the measurement results of both. If you do so, the measurement accuracy will improve. For example, as shown in FIG. 3, there is a certain vertical band 4Y consisting of the width between the electrodes of the first horizontal line 4, and a certain horizontal band 4' consisting of the width between the electrodes of the second vertical line 4'. Overlapping area with X
Let B ₁ be the unit volume B. The measurement target area B ₀ is considered to be a set of these unit volumes B. The apparent resistivity ρ _a of these unit volumes B is measured by the first measuring line 4 and the second measuring line 4'. Then, from the measurement results, the specific resistance ρ _u of each unit volume can be determined, and the state of chemical liquid injection in the entire measurement target area B ₀ can be grasped. By the way, the selection of the unit volume B based on the electrode spacing is arbitrary; for example, if we consider two electrodes as shown in Fig. 3, the overlapping area B ₂ is four times larger than the overlapping area B _1.
can be obtained. Therefore, we adopted a method of collecting resistivity measurement data in extremely narrow ranges such as overlap area B ₁ for important areas of exploration, and collecting data over a fairly wide range for less important locations such as overlap area B ₂ . can. In this way, it is preferable from the viewpoint of measurement sensitivity to measure the specific resistance by providing multiple survey lines and using the overlapping region of the horizontal and vertical bands 4Y and 4'X as the unit volume B. It is also sufficiently possible to detect the specific resistance of the unit volume B by setting the unit volume B only by using the above method, that is, by setting the other survey lines as virtual survey lines. In this case, individual measurement accuracy is low, but
The measurement operation is simple and convenient for obtaining large quantities of measured quantities. Furthermore, FIGS. 4 and 5 show the case where this invention is applied to the injection measuring tube disclosed in JP-A No. 51-79918.
This will be explained using figures. The grout injection tube 3 inserted into the insertion hole 2 consists of an inner tube 3a and an outer tube 3b, and a discharge port 3c is formed in the peripheral wall of the outer tube 3b, and a flexible sleeve is provided to cover the discharge port 3c. 3
d is arranged, and a plurality of injection parts are configured. In this embodiment, a resistivity measuring line 4' having a plurality of electrodes e is arranged along the injection tube 3. Now insert the inner pipe 3a and spread the grout at the outlet 3 while pushing the sleeve 3d.
Grout is injected into the surrounding ground 1 from c. As the grout is injected, the resistivity of each unit volume B of the surrounding ground changes sequentially according to the flow f of the grout. Then, inject while measuring the specific resistance, and if it is determined that the injection at that point is sufficient based on the specific resistance measurement result, the inner tube of the injection tube 3.
Pull up a and inject the upper layer in the same way.
This also changes the specific resistance of each unit volume B. FIG. 6 shows an example using another single-tube type injection pipe 3, in which a specific resistance measuring line 4' having a plurality of electrodes e is buried in the ground separately from the injection pipe 3. However, it can be grouted and probed in the same way as the injection tube described above. In this way,
The surrounding ground near injection pipe 3 will be stabilized.
By adopting such a method, the amount of grout to be injected and the location of the grout to be injected can be controlled reliably, and the ground can be stabilized economically and for the intended purpose. In particular, this invention uses the target ground as an aggregate of unit volumes, and detects changes in resistivity over time in each unit volume, so the ground condition can be accurately grasped. Further, FIGS. 7 to 11 show examples in which the inventor analyzed the injection effect of chemical liquid injection in a certain ground by measuring specific resistance over time.
The numbers in the figure are the "resistivity injection filling rate" expressed in the unit volume according to the classification in the table below.

[Table] The resistivity injection filling ratio (α _res ) was invented by this inventor and is expressed by the following formula (Soil Engineering Library 21 “Physical Exploration of Soil and Foundations” Society of Soil Engineering) (For details, see page 284 of the edition). α _res = ρ _bw - ρ _bg / ρ _bg / ρ _w - ρ _g / ρ _g ρ _bw : Unit volume resistivity before chemical injection ρ _bg : Unit volume resistivity after injection ρ _{w :} Ground water resistivity ρ _g : Specific resistance of the chemical solution From these figures, it is clear that the chemical solution is being injected into the ground sequentially as the injection progresses. Each figure from Fig. 7 to Fig. 11 shows the injection stage, and the temporal changes from the start of injection are divided into stages, and the changes in the injection status are displayed according to the above classification, and the injection is scheduled. Stop the injection when the value reaches . Regarding data display, please refer to the above category 2.
~5 is further divided into three stages for each category,
As the resistivity injection filling rate α _res increases, the numbers in each category are divided into 9 columns in each unit volume.
Changes in the injection state were indicated by writing up to 1. In general, soft ground has a higher porosity and resistivity than dense ground. When a chemical solution is injected into a certain ground, the specific resistance tends to decrease. However, it cannot be concluded that this tendency necessarily exists depending on the type of injected drug solution. However, it is clear that the specific resistance changes depending on the injection of the chemical solution. As described above, according to the present invention, the grout injection status can be accurately grasped for each unit volume, which is extremely useful for rational construction management of grout injection work.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram for explaining the resistivity measurement method, Figure 2 is a plan view of an example of grout injection situation exploration of the ground to be surveyed, Figure 3 is its cross-sectional view, and Figure 4 is a diagram for explaining the resistivity measurement method.
The figure is a sectional view of the main part near the injection tube, Figure 5 is a front view of the injection tube, Figure 6 is a schematic diagram showing exploration examples when different injection modes are used, and Figures 7 to 11 are grout injection. It is an analytical diagram of an example of a change in specific resistance over time. 1...Ground, 2...Insertion hole, 3...Injection pipe, 3
a...Inner pipe, 3b...Outer pipe, 3c...Discharge port, 3
d...Flexible sleeve, 4,4'...Resistance measuring line, e...Electrode, f...Flow of injected grout, 4'X...Horizontal band, 4Y...Vertical band, B , B ₁ , B ₂ ... Unit volume, B ₀ ... Grout injection ground.

Claims (1)

[Scope of Claims] 1. A grout injection pipe 3 is inserted into an insertion hole 2 drilled in a predetermined ground 1, and a resistivity measuring line on which a plurality of electrodes e are attached at predetermined intervals is inserted into the injection pipe 3. or in a straight line on the surrounding ground 1, and the surrounding ground 1 around the injection pipe 3 has a predetermined width b on both sides of the survey line, and has a measurement area that extends in the vertical direction. , as a collection of unit volumes B divided vertically and horizontally based on the electrode spacing, and current electrodes C ₁ and C ₂ connected to the plurality of electrodes e.
and the combination of potential electrodes P ₁ and P ₂ are sequentially moved,
From the measured potential difference, determine the resistivity of each unit volume B, inject grout from the injection pipe 3 to the surrounding ground 1 while changing the injection position sequentially, and measure the resistivity of each unit volume B by injecting grout. Grout injection status exploration characterized by repeatedly detecting how the specific resistance of each unit volume B changes according to changes in position and injection time, and exploring the grout injection status into the surrounding ground 1 of the exploration target. Method. 2. The grout injection situation investigation method according to claim 1, wherein the resistivity measurement line is a horizontal line 4 having a plurality of electrodes e provided in the surrounding ground. 3. The grout injection status investigation method according to claim 1, wherein the resistivity measurement line is a vertical line 4' having a plurality of electrodes e along the injection pipe 3. 4. The specific resistance measuring line consists of a first horizontal line 4 having a plurality of electrodes (e) provided on the surrounding ground, and a second vertical line 4' disposed orthogonally thereto. The method for investigating the grout injection situation as described in item 1.