JP2019031794A - Evaluation method of quality of stabilized soil in ground improvement method, and ground improvement device - Google Patents

Abstract

To evaluate a mixed state of stabilized soil by a mixing and stirring device in real time, and to further improve reliability of evaluation precision and evaluation result of mixed state in a depth direction.SOLUTION: Mixed state of stabilized soil is separately measured at a predetermined sampling period by a plurality of electric conductivity sensors attached to different positions in a depth direction of a mixing and stirring head (step S1). A variation coefficient is obtained as a statistical variation in the depth direction of the mixed state of the stabilized soil by statistically processing the measurement results of each electric conductivity sensor (steps S2 to S4). A propriety determination of mixed state of the stabilized soil is carried out by comparing the obtained variation coefficient with a predetermined target value (step S5). The propriety determination result is visibly displayed on a monitor together with the obtained variation coefficient and the target value (step S6).SELECTED DRAWING: Figure 6

Description

  The present invention relates to a quality evaluation method for a stabilized soil in a ground improvement method and a ground improvement device used for the quality evaluation method.

  As this type of technology, for example, one described in Patent Document 1 has been proposed.

  In the technique described in Patent Document 1, specific resistance measuring instruments are attached to a plurality of locations in the depth direction of a so-called rotary type or trencher type mixing and agitating apparatus, and the measured specific resistance values by the specific resistance measuring instrument are monitored. Thus, it is said that the mixing and stirring state of the soil cement body (mixture of ground soil and improving material or solidifying material) being built by the mixing and stirring device can be grasped in real time. In particular, the electrical resistivity in a state where the ground soil and the solidified material are homogeneously mixed and stirred is set as the reference electrical resistivity, and it is confirmed that the measured values of the above specific resistances are lower than the reference electrical resistivity. Thus, it is said that it is possible to build a homogeneous soil cement body that satisfies the standard electrical resistivity in the entire depth direction of the target ground.

JP 2017-89159 A

  However, the specific resistance measurement value of the soil cement body under construction used as an electrical parameter in the patent literature shows different values depending on the soil properties such as the water content ratio, particle size distribution, specific gravity, and physical properties of the original ground. In particular, in the case of mixing and stirring vertically with a mixing stirrer using a trencher-type mixing stirring blade, the alternating layer ground composed of raw soils having different soil properties will be mixed and stirred. The measured values of resistivity in the soil show different results with only a slight movement of the mixing and stirring device.

For example, the table shown in FIG. 13 shows the properties and conductivity results of several sample soils collected in an area of about 50 m ² (depth of about 6 m) as a daily work amount. The conductivity up to -4 showed very different values. The conductivity is the reciprocal of the specific resistance.

  Therefore, while the target ground (raw soil) shows different values with the movement of the mixing stirrer, the measured specific resistance value of the built soil cement body satisfies the standard electrical resistivity throughout the depth direction of the target ground When the mixing and stirring work is performed, there is still a possibility that the mixed stirring state (mixing condition between the ground soil and the improving material or the solidifying material) is insufficient or the quality is too high. Too much mixing and stirring is a wasteful and uneconomical work.

  In addition, when the measured resistivity value before ground improvement is significantly different, the amount of change (rate of change) in resistivity depends on the added amount of the improved material. Therefore, the measured resistivity value after adding the improved material inevitably. Are likely to be very different. FIG. 14 shows a change in conductivity when a quantitative improvement material is added to the sample soils 1 to 4 shown in FIG. In FIG. 14 as well, the above tendency appears remarkably.

  Therefore, the technique disclosed in Patent Document 1 is an evaluation that should be referred to as an absolute evaluation based on an individual comparison between a predetermined reference specific resistance and each measured specific resistance in the depth direction of the soil cement body. As described above, the measured resistivity value before the improvement material is added and the rate of change when the improvement material is added are different, so the evaluation accuracy in the depth direction and the reliability of the evaluation results are particularly significant. There is still room for improvement.

  The present invention has been made paying attention to such a problem, and is intended to further improve the evaluation accuracy of the mixed state in the depth direction and the reliability of the evaluation result while monitoring the mixed state by the mixing and stirring device in real time. It is intended to provide a method for evaluating the quality of stabilized soil and a ground improvement device in the ground improvement method.

  The present invention penetrates a mixing agitation head having a trencher type mixing agitating blade moving around in the vertical direction into the ground to a predetermined depth, and in addition to discharging a solidified material, excavating the in-situ soil by the mixing agitating blade This is a method for evaluating the mixed state of the stabilized soil in real time in the process of creating a fluidized stabilized soil for ground improvement by mixing and stirring the in situ soil and the solidified material.

  Then, the mixed state of the stabilized soil is individually measured at a predetermined sampling period by means of mixed state measuring means attached to a plurality of locations in the depth direction of the mixing agitating head, and the measurement of each mixed state measuring means is performed. Statistically processing the results to determine the statistical variation in the depth direction of the mixed state of the stable treated soil, relative to the measurement results of a plurality of different locations in the depth direction based on the calculated statistical variation, the stable The mixed state of the treated soil is evaluated.

  That is, in the present invention, as described above, the measurement results measured by the plurality of mixed state measuring means are statistically processed, and statistical variations in the depth direction of the mixed state of the stabilized soil (for example, variation coefficients and standard deviations). ), And is used as an evaluation index for the mixed state of the stabilized soil, and as a result, the measurement results of the respective mixed state measuring means are relatively compared, and this is referred to as relative comparison.

  In this case, as a desirable mode for more quantitatively evaluating the mixed state of the stable treated soil, a target value of statistical variation is determined in advance, and the statistical variation and the target value are compared and stabilized. The suitability of the mixed state of the treated soil shall be determined.

  In a more desirable mode, the statistical variation is a coefficient of variation.

  In addition, since the mixing state of the stable treated soil depends on the operator who operates the mixing and stirring head, as a desirable mode, the suitability determination result of the mixed state of the stable processing soil is given to the operator who operates the mixing and stirring head. Shall be announced.

  As a more desirable mode, when the suitability determination result of the mixed state of the stabilized soil is appropriate or inappropriate and the suitability determination result is inappropriate, the mixing agitation head is still intended to be moved forward. A warning is issued to an operator who operates the mixing and stirring head.

  Further, as a desirable mode for improving the measurement result by each mixed state measuring means, the flow value immediately after mixing and stirring of the stabilized soil is set to 115 mm or more as a table flow value.

  As a preferable ground improvement device used for the quality evaluation method of the above-mentioned stable treated soil, in addition to the above mixing agitation head and each mixing state measuring means, statistical processing is performed by inputting the measurement result of each mixing state measuring means. To obtain the statistical dispersion in the depth direction of the mixed state of the stable treated soil, and on the basis of the obtained statistical dispersion, the measurement results at different locations in the depth direction are relatively compared, and the stable treated soil is mixed. It is desirable to further include a quality control device for evaluating the state.

  More preferably, the quality control device has a function of comparing the statistical variation obtained by the statistical processing with a predetermined target value to determine the suitability of the mixed state of the stable treated soil, and the quality control thereof. In addition to the apparatus, it is further assumed that display means for displaying at least statistical variation obtained by statistical processing and a predetermined target value is further provided.

  Similarly, preferably, the display means is configured to display the result of determining whether or not the mixed state of the stable treated soil is appropriate, in addition to the statistical variation obtained by the statistical processing and the predetermined target value. .

  More preferably, the result of determining the suitability of the mixed state of the stable treated soil is appropriate or inappropriate, and the quality control device still digs and moves the mixing agitation head even though the result of suitability determination is inappropriate. In this case, a warning is issued to the operator of the mixing and stirring head.

  Similarly, as a desirable mode for more accurately measuring the mixed state of the stabilized soil, driving wheels and driven wheels are provided at both upper and lower ends of the post which is the main body of the mixing and stirring head. The mixing stirring blades are wound between the driving wheel and the driven wheel of each of the mixing stirring blades, and each mixing state measuring means has a mixing stirring blade on the tension side and a mixing stirring blade on the loose side in the plan view of the mixing stirring head. And is attached to the side surface of the post.

  According to the present invention, the mixed state of the stably treated soil being created is measured in real time by the plurality of mixed state measuring units having different mounting positions in the depth direction, and the measurement results of the plurality of mixed state measuring units are statistically processed As a result, the mixed state of the stabilized soil under construction was evaluated using this statistical variation as an evaluation index. The evaluation accuracy is improved and the reliability of the evaluation result is also improved.

Side surface explanatory drawing which shows an example of schematic structure of the ground improvement apparatus used for the quality evaluation method of the stabilized soil concerning this invention. FIG. 2 is a right side view of the mixing and stirring head 5 shown in FIG. 1. Explanatory sectional explanatory drawing along the aa line of FIG. The functional block diagram of a quality pipeline apparatus. FIG. 4 is an enlarged view of the mixed state measuring device shown in FIG. 3. The flowchart which shows an example of the process sequence in the quality control apparatus shown in FIG. Explanatory drawing which shows the example of a display on the monitor shown to FIG. FIG. 8 is an explanatory diagram illustrating a display example on the monitor illustrated in FIG. The figure which shows the relationship between the uniaxial compressive strength and electrical conductivity in a position which is different in the depth direction. Explanatory drawing which graphed the uniaxial compressive strength and electrical conductivity of FIG. Explanatory drawing which graphed the coefficient of variation of the lowest stage of FIG. Explanatory drawing which shows the principle of a bipolar conductivity (specific resistance) sensor. The figure which shows the soil property and the value of electrical conductivity of some sample soil. The graph which shows the change of the electrical conductivity at the time of adding a fixed improvement material to the sample soil 1-4 shown in FIG.

  1 and the following drawings show a more specific form for carrying out the quality evaluation method of the stabilized soil according to the present invention, and in particular, FIG. 1 is an outline of the ground improvement device used for the quality evaluation method of the stabilized soil. An example of the structure is shown. 2 is an explanatory diagram on the right side of the mixing and stirring head 5 shown in FIG. 1, and FIG. 3 is an enlarged sectional explanatory diagram along the line aa in FIG.

  The ground improvement device shown in FIG. 1 is an endless track (crawler) or crawler excavator excavating machine, which is one of general-purpose construction machines, such as a hydraulic excavator or backhoe having a crawler belt 1a as a base machine (base machine). 1 is assumed. The swing base 2 of the base machine 1 is equipped with a swinging (undulation or tilting) boom 3, and a swinging arm 4 is connected to the tip of the boom 3. The tip of the arm 4 is detachably mounted with a mixing agitation head 5 for excavation of the in-situ soil to be ground improved as an attachment and mixing agitation with the solidified material (ground improvement material or additive). ing.

  As shown in FIGS. 2 and 3 in addition to FIG. 1, the mixing and agitation head 5 has a rigid frame 6 as a base body, and this frame 6 has a wide and substantially bifurcated yoke portion 6a and a yoke portion 6a. It is comprised from the straight and substantially prismatic post 6b connected with the lower part. The bracket portion 6c at the upper end of the yoke portion 6a is detachably connected to the tip of the arm 4.

  For example, an endless drive chain 10 (endless) between a chain sprocket type drive wheel 8 driven by a hydraulic motor 7 provided at the upper part of the frame 6 and a driven wheel 9 provided at the lower part of the frame 6 is also provided. (See FIG. 3). Further, a plurality of relatively wide mixing and stirring blades 11 shown in FIG. 3 are mounted on the drive chain 10 at a substantially equal pitch so as to be substantially orthogonal to the longitudinal direction of the drive chain 10. The wings 11 are so-called trencher type and are driven around in the vertical direction together with the drive chain 10. The mixing agitating blade 11 is provided with a plurality of cutter bits 11a as excavating blades along the longitudinal direction thereof.

  Further, a discharge nozzle 12 is provided at the front end (lower end) of the frame 6, and for example, a slurry-like solidifying material in which water and powdery cement as a solidifying material are mixed in advance. Is to be pumped. Thereby, it is possible to discharge and inject the slurry-like solidified material from the discharge nozzle 12 toward the ground.

  The drive chain 10 is guided and supported in a state where a predetermined tension is applied by a plurality of guide rollers 13 provided on the frame 6. Note that the mixing and stirring head 5 having such a structure has a known structure, for example, in Japanese Patent Application Laid-Open No. 2005-307675.

  When creating a stable soil for ground improvement using the mixing stirring head 5 having such a structure, in general, while driving a plurality of mixing stirring blades 11 in the vertical direction together with the drive chain 10, As shown in FIG. 1, the entire mixing and agitation head 5 penetrates into the ground in an upright posture using, for example, the swinging force of the boom 3 or arm 4 (force in the swinging operation direction). Then, while discharging the slurry-like solidified material from the discharge nozzle 12, the improved wall body is gradually digged in the so-called traversing direction, that is, the digging direction indicated by symbol b in FIG. As a result, the in-situ soil excavated by the plurality of mixing agitating blades 11 is also mixed and agitated with the slurry-like solidified material by the plurality of mixing agitating blades 11 and is continuously stabilized on the rear side in the digging direction of the mixing agitating head 5. An improved wall made of soil will be constructed.

  In this case, the portion corresponding to the tension side and the loose side of the drive chain 10 in the mixing and agitation head 5 shown in FIG. The circumferential movement surface in the vertical direction (the circumferential movement surface facing the front side in the construction direction of the improved wall body and the circumferential movement surface facing the rear side in the construction direction) is orthogonal to the construction direction of the improved wall body. And it is determined according to the hardness and soil property of a ground whether the surrounding movement surface which faces the construction direction front side of an improved wall body is made upward or downward.

  Here, the mixed and stirred state of the stabilized soil during construction for ground improvement (the mixing state of the raw soil and the added solidified material, hereinafter simply referred to as the mixed state), particularly in the depth direction It is important to manage the mixing state as homogeneous as possible. Therefore, the post 6b of the frame 6 in the mixing and agitation head 5 is mixed at a plurality of locations having different depths in the underground penetration state, and in the examples of FIGS. Mixed state measuring devices 14A, 14B, and 14C are provided as state measuring means. These mixed state measuring instruments 14A to 14C may be installed at least at two places having different depths. However, in order to manage the mixed stirring state in the depth direction as uniform as possible. Then, it is desirable to be installed at three or more locations in the depth direction.

  In addition, the turning base 2 of the base machine 1 shown in FIG. 1 is equipped with a quality control device 15 that also serves as a construction management device, and for visual display of information necessary for quality control by the operation of the operator. A monitor 16 is installed in the cabin as a display device (display means). During the creation of the stabilized soil by the mixing and stirring head 5, the measurement outputs of the mixed state measuring devices 14A to 14C on the mixing and stirring head 5 side are taken into the quality control device 15 in real time.

  The quality management device 15 is configured with a general-purpose personal computer, and includes a control function unit 17 and an output control unit 18, for example, as shown in FIG. The control function unit 17 includes a data storage unit 19, a statistical processing unit 20, a target value setting unit 21, a comparison determination unit 22, an alarm control unit 23, and the like. The control function unit 17 is preinstalled with software necessary for various statistical processes in the statistical processing unit 20 described later, and the output control unit 18 controls display on the monitor 16. . The quality control device 15 may be of a type integrated with the monitor 16, and in that case, the quality control device 15 integrated with the monitor 16 is installed in the cabin.

  Each of the mixed state measuring instruments 14A to 14C has the same structure, and FIG. 5 shows an enlarged view of the mixed state measuring instrument 14B shown in FIG. As shown in FIG. 5, each of the mixed state measuring instruments 14 </ b> A to 14 </ b> C has conductivity sensors 25 and 26 mounted on two surfaces of a substantially flat truncated pyramid shaped pedestal 24. Two sets of electrodes 28a, 28b are embedded so as to be exposed through a holder 27 having an insulating property. Then, each of the mixed state measuring instruments 14A to 14C has the post 6b of the frame 6 in the mixed stirring head 5 so that the exposed surfaces of the electrodes 28a and 28b of the respective conductivity sensors 25 and 26 are directed in the digging direction b shown in FIG. Fixed to the side of the. Therefore, it can be understood that each of the mixed state measuring instruments 14A to 14C includes two sets of so-called two-pole conductivity sensors, and the two conductivity sensors 25 and 26 are mixed stirring heads shown in FIG. It can be selectively used according to the 5 digging directions.

  The stabilized soil under construction for ground improvement can be regarded as an electric resistor having a predetermined resistance value. In each of the conductivity sensors 25 and 26, the specific resistance between the pair of electrodes 28a and 28b is actually used. Is detected. More specifically, in the conductivity sensors 25 and 26 shown in FIG. 5, as will be described later, the path of the current sensor when the current is passed between the pair of electrodes 28a and 28b facing the stabilized soil. A resistance value is obtained by measuring a voltage (potential difference), and a specific resistance ρ (Ωm) in consideration of the length and cross-sectional area of the path through which the current flows is detected as an electrical parameter.

  In this embodiment, the measured value detected by each of the conductivity sensors 25 and 26 is not shown because the reciprocal of the specific resistance is the conductivity without using the measured value of the specific resistance as it is. By passing through the converter, it is converted into the conductivity which is the reciprocal of the specific resistance measurement value, and then taken into the quality control device 15. Note that the conversion to conductivity, which is the reciprocal of the measured specific resistance value, can be performed on the quality control device 15 side.

  Further, as shown in FIG. 3, two mixing state measuring devices 14B are attached to both sides of the post 6b of the frame 6 in the mixing and stirring head 5 so as to face each other with the post 6b therebetween, and these are selected. You may make it use it. Furthermore, if necessary, in place of the two-pole conductivity sensors 25 and 26 constituting the mixed state measuring instruments 14A to 14C, a conductivity meter in addition to a three-pole or four-pole conductivity sensor. Or it is generally marketed as a conductivity sensor (for example, an electromagnetic induction type conductivity sensor), and it is also possible to use a type that can output a measured conductivity value as it is. In the case of using a commercially available conductivity meter or conductivity sensor that can output the measured conductivity value as it is, the above converter is not necessary.

  As the mounting mode of each of the mixed state measuring devices 14A to 14B, when measuring the mixed state of the stable treated soil being created, the stable treated soil that is in the fluidized state during mixing and stirring and the conductivity sensors 25 and 26 are connected. It is required that the electrodes 28a and 28b are completely brought into close contact with each other without generating a gap. Therefore, as shown in FIG. 3, the mounting positions of the mixed state measuring instruments 14 </ b> A to 14 </ b> C are, as viewed in a plan view of the mixing and stirring head 5, the trencher-type mixing stirring blade 11 that is the tight side and the trencher type that is the loose side. It is desirable to attach to the side surface of the post 6b which is a region sandwiched between the mixing and stirring blades 11 and parallel to the digging direction of the mixing and stirring head 5.

  Further, as described above, it is possible to completely contact the stable treated soil in a fluidized state during mixing and stirring without any gap between the electrodes 28a and 28b of the conductivity sensors 25 and 26. Since it is necessary, the base 24 serving as a base of each of the mixed state measuring instruments 14A to 14C is formed in a substantially flat truncated pyramid shape so that the electrodes 28a and 28b of the conductivity sensors 25 and 26 are exposed on the inclined surfaces. It is arranged. For example, when the mixing and stirring head 5 moves in the left direction in FIG. 3, one conductivity sensor 25 is used. On the other hand, when the mixing and stirring head 5 moves in the right direction in FIG. The conductivity sensor 26 is used. In this case, both the conductivity sensors 25 and 26 can be used simultaneously as necessary.

  On the other hand, for the close contact between the conductivity sensors 25 and 26 and the stable treated soil, it is desirable to fluidize the flow value of the stable treated soil. As a reference, the flow value immediately after mixing and stirring the stable treated soil is used as the table flow value. 115 mm or more is desirable. If only the adhesion between the conductivity sensors 25 and 26 and the stabilized soil is taken into consideration, it is desirable that the table flow value is high, but the ground improvement is intended to increase the strength of the in situ soil with a solidifying material such as cement milk. In construction, it is known that the expression strength of the stabilized soil at the same addition amount and the table flow value (flow value) at the time of mixing and stirring are inversely proportional. Therefore, the table flow value of 115 mm is obtained by using the liquid limit value of the stabilized soil as a guideline for the lower limit value of the table flow value.

  As a specific example of the mounting position of each of the mixed state measuring devices 14A to 14C described above, for example, when the ground is improved to form a retaining wall having a depth of 10 m and a thickness of 1 m, a mixing stirring head 5 having a length of 11 m and a width of 1 m is provided. Let's assume the use case. In this case, the mixed state measuring instrument 14A at the upper end is attached to a position corresponding to the upper layer portion near 9.0 m (near GL-1.0 m) from the lower end portion of the mixing and stirring head 5. Moreover, the mixing state measuring instrument 14B in the middle part is attached to a position corresponding to the middle layer part near 5.0 m (near GL-5.0 m) from the lower end part of the mixing and stirring head 5. Similarly, the mixing state measuring device 14 </ b> C at the lower end is attached to a lower layer equivalent position near 1.0 m (near GL-9.0 m) from the lower end of the mixing and stirring head 5.

  As shown in FIG. 4, during the creation of the stable treated soil by the mixing and stirring head 5, the actual measurement values, which are measurement outputs of the mixed state measuring instruments 14 </ b> A to 14 </ b> C, are converted into conductivity. The quality management device 15 takes in and stores the information in real time. In this quality control device 15, conductivity data input in real time to the quality control device 15 is sampled and accumulated at a predetermined cycle, and then necessary statistical processing is performed to evaluate the quality of the mixed state of the stable treated soil. Statistical dispersion, which is an index of Then, by comparing the calculated statistical variation with the target value, the suitability determination of the mixed state is performed as the quality evaluation of the stable treated soil at that time.

Here, the digging distance of the mixing and agitation head 5 per minute when the earth retaining wall is constructed with a construction soil volume of 40 m ³ per hour will be determined below.

Digging distance = {construction volume per hour ÷ (depth of retaining wall × thickness)} ÷ (1 hour)
= {40 ÷ (10 × 1)} ÷ 60≈0.066 m / min It is preferable that the evaluation judgment frequency of the mixed state of the stably treated soil during creation is as small as possible. On the other hand, the mixing state of the stable treated soil is measured in real time while the earth retaining wall is being formed, and the mixed stirring head 5 is evaluated according to the evaluation determination while evaluating and determining the mixed state of the stable treated soil based on the result. In consideration of performing the excavation operation, the evaluation determination frequency may be performed at a frequency of about once every 1 to 5 minutes. Even if the evaluation is judged at a frequency of at least once every 5 minutes, the retaining wall is created while confirming the mixed state of the stable treated soil during mixing and stirring at a rate (frequency) of once every 33 cm. It is estimated that the quality of the retaining wall will be sufficiently secured.

  In this embodiment, the conductivity data sampling based on the measured values of the conductivity sensors 25 and 26 in the three mixed state measuring instruments 14A to 14C described above is performed every second, as shown in FIG. In addition, the quality control device 15 accumulates the sampled conductivity data every one minute and then performs statistical processing according to the procedure shown in FIG. 6 to obtain a coefficient of variation that is statistical variation. By comparing with the target value, even the suitability determination of the mixed state is performed. In addition, the sampling period of conductivity data can be set arbitrarily.

  In step S1 of FIG. 6, the measurement output of the conductivity sensors 25 and 26 is sampled every second for each of the mixed state measuring devices 14A to 14C, and conductivity data which is 60 sampling data for one minute. Is stored and stored.

  In the next step S2, for each of the mixed state measuring instruments 14A to 14C, conductivity data that is 60 sampling data for one minute is used as a population, and the average value for one minute is obtained for each of the mixed state measuring instruments 14A to 14A. Calculate every 14C.

  In step S3, the average value and the standard deviation for 1 minute of the three mixed state measuring instruments 14A to 14C as a whole are obtained by using conductivity data that is 180 pieces (60 pieces × 3) of sampling data for one minute as a population. Ask for.

  In step S4, based on the average value and the standard deviation obtained in the previous step S3, a variation coefficient (%) which is a comprehensive statistical variation as the whole of the three mixed state measuring instruments 14A to 14C is obtained. The coefficient of variation is a value obtained by dividing the standard deviation by the average value.

  Here, regarding the variation count, the target value (threshold value or setting reference value) is obtained in advance experimentally and empirically, and stored and set in the target value setting unit 21 of the quality management device 15. And

  Then, in step S5 of FIG. 6, the variation count obtained previously is compared with the target value to determine whether or not the mixed state in the stable treated soil being created is appropriate. This suitability determination is performed with suitability (OK) or suitability (NG).

  Then, in the next step S6, along with the average value of the conductivity data for each of the mixed state measuring instruments 14A to 14C previously determined, the coefficient of variation previously determined as statistical variation, and the target value, The determination result is visually displayed on the monitor 16 shown in FIGS. 1 and 4 and used for the excavation operation of the mixing and stirring head 5 by the operation of the operator.

  7A and 7B show examples of screen display on the monitor 16. FIG. 6A shows the conductivity of the conductivity sensors 25 and 26 in each of the mixed state measuring instruments 14A to 14C when the target value of the coefficient of variation, which is an evaluation index of the mixed state of the stabilized soil, is 15%, for example. When the variation coefficient actually obtained based on the data is 45%, the appropriateness determination result of the mixed state at that time is displayed as inappropriate (NO). As is clear from the figure, since the average values of the conductivity data of the conductivity sensors 25 and 26 in the three mixed state measuring instruments 14A to 14C having different depth positions vary widely, it is comprehensive from the conductivity data. It can be understood that the coefficient of variation obtained from the target deviates greatly from the target value.

  Therefore, the operator continues the mixing and stirring process at a fixed position without digging the mixing and stirring head 5 until the coefficient of variation satisfies the target value while checking the screen display on the monitor 16 of FIGS. .

  On the other hand, FIG. 7B shows the conductivity sensors 25 and 26 in the mixed state measuring instruments 14A to 14C when the target value of the coefficient of variation, which is an evaluation index of the mixed state of the stabilized soil, is 15%, for example. The variation coefficient actually obtained based on the conductivity data is 15%, and the result of determining whether the mixed state is appropriate at that time is displayed as appropriate (OK). As is clear from the figure, the variation in the average value of the conductivity data of the conductivity sensors 25 and 26 in the three mixed state measuring instruments 14A to 14C having different depth positions is smaller than that in FIG. Therefore, it is understood that the coefficient of variation obtained comprehensively from the conductivity data matches the target value.

  In this way, when the result of determining whether the coefficient of variation, which is an indicator of the mixing state of the stabilized soil under construction, is appropriate (OK), the operator moves the mixing agitation head 5 so as to traverse a predetermined amount. Will do the same.

  Here, as an additional function, an alarm device 16a such as a red light is installed near the monitor 16 shown in FIG.

  And, for example, as shown in FIG. 7A, when the operator tries to move the mixing and agitating head 5 in spite of the inappropriateness determination result of the mixed state (NG), As shown in step S7 of FIG. 6, the warning device 16a is turned on together with a warning sound to issue a warning, and the operator is encouraged to continue the mixing and stirring operation at the previous position. As shown in FIGS. 1 and 4, whether or not to issue a warning by turning on the warning device 16a together with a warning sound indicates the position information of the movable part on the base machine 1 side, for example, the turning base 2 and boom of the base machine 1. 3 and the position information of the operating lever in the cabin operated by the operator and the above-described suitability determination result are collated by the alarm control unit 23 in FIG.

  FIG. 8A shows a graph of the numerical values in the screen display of FIG. 7A. Similarly, FIG. 8B shows the screen display of FIG. 7B. It shows the graph of the numerical value at. As is clear from FIGS. 8A and 8B, it is easier to understand that the variation in conductivity tends to converge in FIG. 8B than in FIG. 8A. it can.

  Here, the numerical value itself of the average value of the conductivity data of the three mixed state measuring devices 14A to 14C in the screen display in FIGS. 7A and 7B does not have a great meaning. The reason for this is that, as the quality (mixed state) of the stabilized soil during creation, it is important that there is little difference in the depth direction and that it is homogenized, and the screens in FIGS. 7A and 7B This is because even if the average values of the conductivity data of the three mixed state measuring instruments 14A to 14C in the display do not coincide with each other, the intended purpose can be achieved if the average values are approximate to each other. Therefore, in this embodiment, as a statistical variation which is an evaluation index of the mixed state of the stable treated soil under creation, a relative comparison between the average values of the conductivity data in the three mixed state measuring instruments 14A to 14C is performed. Considered coefficient of variation.

  7A and 7B, the average value of the conductivity data of the mixed state measuring instrument 14C at the lowest layer in the depth direction is displayed with the largest value in the lower part of the mixing and stirring head 5. Since the solidification material is continuously discharged from the nozzle 12 (see FIGS. 1 and 2), the lower layer tends to promote the penetration of the solidification material, and this tendency is unavoidable in terms of construction method.

  The mixing condition (mixing condition) of the stabilized soil during mixing and stirring is generally determined by the variation in uniaxial compressive strength (depth direction) in all layers (lower layer, middle layer, upper layer) of the stabilized ground. The strength is determined by evaluation. In performing the evaluation judgment with the coefficient of variation, which is the statistical variation of the conductivity, instead of the variation of the uniaxial compressive strength, the three in-situ locations (A, B, C) Soil) and slurry solidified material are mixed and agitated, and the electrical conductivity of the stabilized soil during the mixing and agitation is compared with the uniaxial compressive strength of the specimen by core boring after predetermined curing. I conducted a survey.

The solidification material addition amount (kg / m ³ ) and the construction amount per hour (m ³ / h) at each construction location (A, B, C) are shown below.
A: Addition amount 100 kg / m ³ , construction amount 60 m ³ / h per unit time
-B: Addition amount 150 kg / m ³ , construction amount per unit time 50 m ³ / h
C: Addition amount 200 kg / m ³ , construction amount 40 m ³ / h per unit time
In this case, the table of FIG. 9 shows the measurement results of the conductivity of the stabilized soil during mixing and stirring under the above conditions and the results of the uniaxial compressive strength of the stabilized soil at a position (depth) corresponding to the depth. . In addition, the measurement result of electrical conductivity is measured by the electrical conductivity sensors 25 and 26 in the three mixed state measuring devices 14A to 14C described above.

The average values of the electrical conductivity and uniaxial compressive strength at each construction location are as follows: the electrical conductivity at construction location A is 392.4 mS / m, the uniaxial compressive strength is 355.0 kg / m ² , and the electrical conductivity at construction location B is 434. The result was 0.7 mS / m, the uniaxial compressive strength was 538.7 kg / m ² , the conductivity of the construction site C was 521.9 mS / m, and the uniaxial compressive strength was 761.9 kg / m ² .

  A graph of these measurement results is shown in FIG. Moreover, the correlation tendency that can be grasped from the comparison of the measurement results is shown below.

・ Change in amount of solidification material added: A <B <C
・ Change in construction amount per unit time: A>B> C
・ Change in average conductivity: A <B <C
・ Change in average uniaxial compressive strength: A <B <C
・ Diffusion in conductivity in the depth direction (coefficient of variation): A>B> C
・ Diffusion in uniaxial compression strength in the depth direction (coefficient of variation): A>B> C
That is, the characteristics obtained from the comparison of the measurement results are as follows.

  -The amount of solidification material added, the average conductivity, and the uniaxial compressive strength are directly proportional.

  -The construction amount per unit time, average conductivity and uniaxial compressive strength are inversely proportional.

  ・ The amount of construction per unit time and the variation of conductivity in the depth direction are directly proportional.

  ・ Diffusion in the depth direction of construction volume per unit time and uniaxial compressive strength is directly proportional.

  -The variation in the depth direction of the conductivity and the variation in the depth direction of the uniaxial compressive strength are directly proportional.

  At the bottom of the table in FIG. 9, the coefficient of variation (variation in the depth direction) obtained from the measurement results of the conductivity sensors 25 and 26 of the three mixed state measuring devices 14A to 14C is shown. FIG. 11 is a graph showing the variation coefficient. Also from this graph, the coefficient of variation of the conductivity (ec) indicating the variation in the depth direction and the uniaxial compressive strength (qu) is almost directly proportional.

  That is, as in the previous embodiment, the electrical conductivity of the stable treated soil is measured, and the degree of mixing, which is the quality of the stable treated soil during mixing and stirring, is determined by the coefficient of variation that is statistical variation. It can be understood that it is extremely effective to evaluate and judge (mixed state).

  Next, let us consider the target value of the coefficient of variation, which is statistical variation in the previous embodiment.

  Regarding the coefficient of variation, which is a statistical variation of the conductivity as described above, a target value is determined in advance, and the coefficient of variation actually obtained through statistical processing is compared with a predetermined target value to determine suitability. Then, as described above, it is possible to quantitatively and smoothly evaluate the mixed state of the stabilized soil during mixing and stirring.

  There are two methods for setting the target value: a method of determining an empirical numerical value as the target value, and a method of determining the target value by performing a test work before starting the ground improvement work. The former method is said to be satisfactory if the variation in quality in normal ground improvement work (the variation in uniaxial compression strength exemplified above) falls within the range of about 20% to 40% in terms of the coefficient of variation. It has been broken. The coefficient of variation, which is the statistical variation in the conductivity of the stabilized soil during mixing, and the coefficient of variation in the variation in the strength of the stabilized soil (the coefficient of variation in uniaxial compressive strength) are generally correlated (in direct proportion). As mentioned above. From these empirical barometers, if the target value of the coefficient of variation of the stabilized soil is 20% or less below the coefficient of variation of uniaxial compressive strength, sufficiently good quality can be obtained.

  The latter method is as follows (1) to (3).

  (1) The conductivity is measured as an electrical parameter of the stably treated soil in a fluidized state during mixing and stirring in the ground (original position) that is considered to be a representative formation in the field.

  (2) In the test construction, mixing and stirring of the slurry-like solidified material (water / solidified material ratio, added amount, etc.) determined in the preliminary test and in-situ soil is performed.

  (3) The conductivity obtained in the test construction is set as a target value (threshold value or set reference value) of the conductivity during actual mixing and stirring. In addition, it is good also considering the dispersion | variation (for example, variation coefficient) of the electrical conductivity which differs in the depth direction obtained by test construction as a target value.

  Furthermore, as a method other than the above, there is also a method in which a target value of the coefficient of variation is determined in advance according to the purpose (quality level) of the ground improvement work. For example, as a coefficient of variation of the expression strength (uniaxial compressive strength) of the stabilized soil according to the required quality level, the coefficient of variation of quality rank 1 (top-level quality) is 20% or less, and quality rank 2 (medium level) The coefficient of variation for quality may be 30% or less, and the coefficient of variation for quality rank 3 (quality that ensures the minimum required performance) may be 40% or less.

  In this case, as described above, since there is a correlation between the coefficient of variation of the expression strength (uniaxial compressive strength) of the stabilized soil and the coefficient of variation of conductivity, Thus, the target value of the coefficient of variation of conductivity is determined according to the coefficient of variation of the expression strength (uniaxial compressive strength) of the stabilized soil. However, considering that the coefficient of variation of conductivity varies sensitively depending on the soil properties of the raw soil, the target value of the coefficient of variation of conductivity is the expression strength (uniaxial compressive strength). It is desirable that the value be less than the coefficient of variation. For example, the target value of the coefficient of variation of conductivity in the case of quality rank 1 is 15% or less, the target value of the coefficient of variation of conductivity in the case of quality rank 2 is 25% or less, and the fluctuation of conductivity in the case of quality rank 3 The target value of the coefficient is 35% or less.

  As described above, according to the present embodiment, the conductivity sensor 25 of the three mixed state measuring instruments 14A to 14C provided at different positions in the depth direction as an evaluation index of the mixed state which is the quality of the stable treated soil being created. 26, the coefficient of variation of the conductivity data collected at 26 is obtained, and the suitability determination of the mixed state is performed by comparing the obtained coefficient of variation with the target value. Therefore, the accuracy and reliability of the mixed state evaluation result, which is the quality of the stable treated soil being created, and thus the suitability determination result are higher than in the past, and the occurrence of excess or deficiency in the mixed state can be suppressed. As a result, cost-effective construction can be performed.

  Here, all of the screen display items on the monitor 16 shown in FIG. 7 are not necessarily required, and at least the display of inappropriateness (NG) or appropriateness (NO), which is the determination result of appropriateness, achieves the intended purpose. In addition, the display of the suitability determination result may be a color switching display, lamp lighting / non-lighting, or a sound notification by a buzzer or an alarm.

  In the present embodiment, the bipolar conductivity sensors 25 and 26 in the mixed state measuring instruments 14A to 14C actually detect the specific resistance between the pair of electrodes 28a and 28b shown in FIG. As described above, the measured value of specific resistance is converted into the conductivity which is the reciprocal of the specific resistance and then taken into the quality control device 15.

As shown in FIG. 12, the stable treated soil that is being measured in the present embodiment can be regarded as an electric resistor of electric resistance R, and the measurement of the electric resistance is performed in the stable treated soil. A current is caused to flow between the pair of electrodes 28a and 28b facing the electrode, and the resistance (R) is obtained by measuring the voltage (potential difference) of the path through which the current flows. This resistance R varies depending on the length and cross-sectional area of the path through which the current flows. Therefore, the resistance of the object is detected as a specific resistance ρ (Ω m) when the unit dimensions are 1 m ² and 1 m in length. ing. The specific resistance ρ is converted into conductivity (mS / m) which is the reciprocal of the specific resistance ρ and used as an electrical parameter necessary for the calculation of the statistical variation.

  On the other hand, in the three mixed state measuring devices 14A to 14C in the screen display in FIGS. 7A and 7B, the numerical value of the average value of the conductivity data of the individual conductivity sensors 25 and 26 itself. Is not so significant, and as the quality (mixed state) of the stably treated soil during creation, it is particularly important that the difference in the depth direction is small and homogenized. First, it is sufficient that the average values of the conductivity data of the three mixed state measuring instruments 14A to 14C in the screen display in FIGS. Stated.

  In short, the average values of the electrical parameters of the three mixed state measuring instruments 14A to 14C in the screen display in FIGS. 7A and 7B are relatively compared, and the difference between them is as much as possible. If it is small, the intended purpose can be achieved.

  In other words, instead of the electrical parameters such as conductivity and specific resistance described above, for example, the resistance value between the pair of electrodes 28a and 28b before obtaining the specific resistance described above, or a pair under a constant current. The intended purpose can be achieved even if the voltage between the electrodes 28a and 28b or the magnitude of the current between the pair of electrodes 28a and 28b when a constant voltage is applied is used as an electrical parameter. That is, as the mixed state measuring instruments 14A to 14C in the previous embodiment, it is possible to use means for measuring other electrical parameters such as resistance, current, voltage, etc., instead of the conductivity sensors 25, 26. .

  In this embodiment, a coefficient of variation is used as a statistical variation of electrical parameters represented by conductivity. However, as other statistical variations, standard deviation, range, average difference, average absolute deviation, etc. Of course, it is also possible to use.

  Furthermore, in the present embodiment, the description has been given by taking as an example the creation of a stabilized soil in the ground improvement method, but if necessary, the present invention can mix and agitate, for example, soil contaminated with heavy metal or oil, a reducing agent, and a purifying agent. Thus, it can be applied to a method for purifying contaminated soil.

DESCRIPTION OF SYMBOLS 1 ... Base machine 5 ... Mixing stirring head 6 ... Frame 6b ... Bost 10 ... Drive chain 11 ... Mixing stirring blade 14A-14C ... Mixing state measuring device 15 ... Quality control apparatus 16 ... Monitor (display means)
16a ... Alarm device 25, 26 ... Conductivity sensor 28a, 28b ... Electrode

The present invention penetrates a mixing agitation head having a trencher type mixing agitating blade moving around in the vertical direction into the ground to a predetermined depth, and in addition to discharging a solidified material, excavating the in-situ soil by the mixing agitating blade In the process of mixing and stirring the in situ soil and solidified material, and creating a fluidized stabilized soil for ground improvement, the mixed state of the stabilized soil is measured and evaluated in real time. is there.

On top of that, with measured separately at a predetermined sampling period the mixed state of the treated soil as a specific electrical parameters by mixed state measuring means attached to the plurality of locations of different depths direction of the mixing and stirring head, its accumulating the measurement result, in parallel with the measurement, and statistical processing of the measurement results of the predetermined time that the storage of electrical parameters variations of the particular in the depth direction of the mixed state of the treated soil It is obtained as a statistical variation, and the obtained statistical variation is compared with a predetermined target value of the statistical variation to determine whether or not the mixed state of the stabilized soil is appropriate. is there.

That is, in the present invention, as described above, the measurement results measured by the plurality of mixed state measuring means are statistically processed, and statistical variations in the depth direction of the mixed state of the stabilized soil (for example, variation coefficients and standard deviations). replaced by a), Ru Tei as an evaluation indicator of the mixed state of the treated soil.

Preferred soil modifying apparatus used in the quality evaluation method of the treated soil, and the mixture stirred for head, wherein each mixed state measuring means, in addition, after accumulating the measurement results of the respective mixed state measuring means While performing statistical processing to determine the variation in the depth direction of the mixed state of the stabilized soil as the statistical variation of the specific electrical parameter, the calculated statistical variation and the predetermined statistical variation and compared with the target values, it is to further comprises a quality control device for performing the suitability judgment of mixed state of the treated soil.

More preferably, in addition to the quality control apparatus, it is assumed that further comprising a display means for displaying said target value and said statistical dispersion obtained in at least the statistical processing.

Claims (11)

After a mixing stirrer head equipped with a trencher-type mixing stirrer that moves around in the vertical direction penetrates the ground to a predetermined depth, in addition to discharging the solidified material, excavation of the original soil by the mixed stirrer and its original position A method of evaluating the mixed state of the stabilized soil in real time in the process of creating a fluidized stabilized soil for ground improvement by mixing and stirring the soil and solidified material,
The mixed state of the stable treated soil is individually measured at a predetermined sampling period by a mixed state measuring unit attached to a plurality of different positions in the depth direction of the mixing and stirring head,
Statistical processing of the measurement results of each mixed state measuring means to obtain the statistical variation in the depth direction of the mixed state of the stable treated soil,
Relative comparison of measurement results at a plurality of different locations in the depth direction based on the obtained statistical variation, and evaluating the mixed state of the stabilized soil, a method for evaluating the quality of the stabilized soil in the ground improvement method .   The ground according to claim 1, wherein a target value for the statistical variation is determined in advance, and the statistical variation is compared with the target value to determine whether the mixed state of the stable soil is appropriate. Quality evaluation method of the stabilized soil in the improved construction method.   The method for evaluating the quality of a stabilized soil in a ground improvement method according to claim 1 or 2, wherein the statistical variation is a coefficient of variation.   The result of determining the suitability of the mixed state of the stabilized soil is notified to an operator who operates the mixing and agitating head. The stabilized soil in the ground improvement method according to any one of claims 1 to 3, Quality evaluation method. The result of determining the adequacy of the mixed state of the stabilized soil is appropriate or inappropriate,
5. The operator operating the mixing and stirring head is warned even when the mixing and stirring head is to be moved forward even though the suitability determination result is unsuitable. Quality evaluation method of stabilized soil in the described ground improvement method.   The flow evaluation value immediately after mixing and stirring of the stabilized soil is a table flow value of 115 mm or more, and the quality evaluation method of the stabilized soil in the ground improvement method according to any one of claims 1 to 5 . A ground improvement device used for a quality evaluation method of the stabilized soil in the ground improvement method according to any one of claims 1 to 6,
In addition to the mixing agitation head and the mixing state measuring means,
Statistical processing is performed using the measurement results of the mixed state measuring means as inputs, and the statistical variation in the depth direction of the mixed state of the stabilized soil is obtained, while the depth direction differs based on the obtained statistical variation. A ground improvement device further comprising a quality control device for comparing the measurement results at a plurality of locations and evaluating the mixed state of the stabilized soil. The quality control device has a function of comparing the statistical variation obtained by the statistical processing with a predetermined target value to determine the suitability of the mixed state of the stable treated soil,
8. The ground improvement device according to claim 7, further comprising display means for displaying at least a statistical variation obtained by the statistical processing and a predetermined target value in addition to the quality control device.   The display means is configured to display a result of determining whether or not the mixed state of the stable treated soil is appropriate, in addition to the statistical variation obtained by the statistical processing and a predetermined target value. Item 9. The ground improvement device according to item 8. The result of determining the adequacy of the mixed state of the stabilized soil is appropriate or inappropriate,
The quality control device has a function of issuing a warning to an operator of the mixing and agitating head even when the mixing and agitating head is to be moved forward even though the suitability determination result is inappropriate. The ground improvement device according to claim 8, wherein the ground improvement device is provided. A driving wheel and a driven wheel are provided at the upper and lower ends of the post which is the main body of the mixing and stirring head, and
The mixing stirring blade is wound between the driving wheel and the driven wheel,
Each of the mixed state measuring means is a region sandwiched between the mixing stirring blade on the tight side and the mixing stirring blade on the loose side in a plan view of the mixing stirring head, and is attached to the side surface of the post The ground improvement apparatus as described in any one of Claims 7-10 characterized by the above-mentioned.

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