JP2015151687A - Method for setting construction specification and improvement body strength in high-pressure injection stirring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for setting a construction specification by which an improvement diameter and an improvement body strength in a high-pressure injection stirring method can be respectively controlled and the improvement body of a high-quality can be prepared at low cost.SOLUTION: A method includes: a "pre-confirmation" process, in which a blending test is performed to obtain "an amount of solidification material Cclm per improvement body volume" for achieving a target strength, and on the basis of the result, the minimum time value Tst (min) per step is calculated; a "test construction" process, in which a state of ground cutting using a hardener injected at high pressure from an injection pipe is monitored and a rotation speed Tr that secures a desired improvement diameter is determined; and a "specification determination" step, in which a time Tst per step is confirmed on the basis of the rotation speed Tr and a number of cutting Nc per step, and a withdrawing time v of the injection pipe is determined on the basis of the time Tst per step (or the minimum time value Tst (min)) and a step length Lst.

Description

  The present invention relates to a method for setting construction specifications for a high-pressure jet agitation method (so-called jet grout method) and an improved body strength setting method for the high-pressure jet agitation method.

  The high-pressure jet agitation method is a ground improvement method that generally mixes and agitates soil and hardener by cutting the ground by injecting a hardener and air in a horizontal direction from an injection nozzle attached to the tip of an injection pipe. Usually, the injection pipe in a state of being inserted into the ground is rotated and pulled up stepwise by several centimeters (that is, stepped up) at regular time intervals to form a substantially cylindrical large-diameter improved body. The outline of the procedure of the high-pressure jet stirring method is as follows.

<Step a>
As shown in FIG. 9 (a), the construction machine 6 is installed at the center of the construction position of the ground improvement body, and the injection pipe 7 is suspended from the construction machine by a crane and installed. And it inserts to the planned depth in the ground, rotating the injection pipe 7 by the construction machine 6 while discharging the drilling water from the tip of the injection pipe 7.

<Process b>
When the injection pipe 7 is inserted to the planned depth, the rotation speed (s / rotation) of the injection pipe and the lifting time (s / m) are set, and the injection of the hardened material is started. Thereby, since the hardened material is injected at a high pressure from the spray nozzle at the tip of the spray pipe, the raw ground is cut by the powerful energy of the hardened material jet.

<Process c>
By rotating the injection pipe 7 at the set rotation speed, the ground is cut by the injection flow of the high-pressure injected hardener, and the raw soil and the hardener are forcibly stirred and mixed. Then, when the partial creation of the improved body in the first stage is completed, the construction machine is operated to step up the injection pipe step by step to the second stage, the third stage,. For example, the step length (length per step) is set to 25 mm, and the number of steps per meter is set to 40 steps. In this way, by rotating the injection tube at a set speed in each stage, high-pressure injection of the curing material from the injection nozzle, and stepping up the injection tube stepwise according to the set pull-up time, a substantially cylindrical improvement body Can be created.

<Process d>
After creating an improved body within a predetermined improvement range, the injection pipe 7 is pulled out to the ground, and the inside of the pipe is washed with fresh water.

In the field of the high-pressure jet stirring method described above, standard construction specifications are set according to the ground conditions (soil quality and N value). This standard construction specification improves the standard effective diameter, which is the minimum guaranteed value, by setting the lifting time of the injection pipe (min / m) and the discharge amount of hardened material (m ³ / min) according to the ground conditions. It is designed to ensure body strength.

Conventionally, a blending test is not normally performed in the implementation of the high-pressure jet stirring method. The reason is as follows.
(1) The design standard values (improved diameter, design standard degree) of the jet grout method are obtained from the improved body created based on the construction specifications (injection pressure, discharge amount, lifting time, etc.) determined in advance by each method. (The design standard value is not reviewed in each construction due to differences in the target soil quality and the discharge amount of the hardened material).
(2) The amount of water and improvement material blended in the soil to be improved cannot be clearly defined (due to the amount of mud and its concentration, the improvement diameter, etc., the discharge amount is not necessarily equal to the mixing amount).

  In the improvement of the bottom plate using the high-pressure jet agitation method, the construction specifications are set so that the improved diameter is larger than the standard effective diameter for complete lapping. In producing an improved diameter other than the standard effective diameter, there is a case where the raising speed of the injection pipe is changed. However, when the improved diameter becomes too large, there is a problem in that the amount of unit hardened material (the amount of hardened material per volume of the created improved body) is reduced and the design strength cannot be secured. In addition, when creating an improved body with a complete lap arrangement, if the improved diameter becomes too large and reaches the center of the adjacent pile construction position as shown in FIG. There was a problem that a defect (state in which the ground could not be cut even when the hardened material was sprayed) occurred and the adjacent pile could not be constructed or the diameter became small.

  In general, in the high-pressure jet agitation method, the construction specification is set such that the amount of the hardener discharged relative to the improved volume is increased so that the design strength can be ensured even when the larger improved diameter is obtained. However, as a result of increasing the discharge amount in this way, a curing material more than necessary is used, which increases the material cost. There is also a problem that the construction time per piece becomes longer and the construction period of the whole construction becomes longer. Furthermore, as the amount of the hardener discharged increases, the amount of mud increases accordingly, which increases the burden on the environment and increases the burden of waste mud treatment. Therefore, as a result of enlarging the improved diameter and ensuring the necessary design strength, there are various problems such as an increase in environmental load, an increase in material costs and waste mud treatment costs, and an increase in construction costs. It was happening.

  In addition, when the target ground of the high-pressure jet agitation method is an alternating layer ground, the effective diameter was designed according to the hardest layer, so the diameter of the improved body to be created becomes uneven, and depending on the soil layer, the improved diameter may be It was growing in vain. Thus, since the site | part by which an improved diameter was built large was produced, the material cost and the waste mud processing cost increased like the above, and the problem that construction cost became expensive had arisen.

In the high-pressure jet agitation method, since the hardener discharge amount (m ³ / s) and the injection pressure (MPa) are positively correlated, if one is changed, the other changes accordingly. For example, when the discharge amount (m ³ / s) of the curing material is increased in order to set the improved body strength higher, the injection pressure (MPa) increases and affects the direction of increasing the improved diameter. At this time, since the improved volume is increased, the amount of the unit curing material is reduced depending on conditions, and the strength of the improved body may be reduced. Further, in order to change the other in a state where one of the discharge amount and the pressure is fixed, it is necessary to change the nozzle diameter. However, due to the characteristics of the high-pressure jet stirring method, the nozzle cannot be replaced during the construction. As described above, there is a problem that the specification cannot be changed substantially such that only one of the discharge amount (m ³ / s) of the curing material and the injection pressure (MPa) is changed for each depth.

  Furthermore, in recent years, high-pressure jet agitation methods have been widely adopted for liquefaction countermeasures and seismic reinforcement work, and the required accuracy such as improved diameter and required improved strength has increased more than before. There is a strong demand for a means for grasping and controlling the improved diameter and the required improved strength freely. In particular, in the ground improvement in the construction field, it is essential to grasp the improved diameter and the strength of the improved body. Moreover, since the strength and the improved diameter could not be secured, it could not be used as a foundation pile.

  Furthermore, there is a strong demand for means that can create an improved body having a desired improved diameter and improved strength even in the ground conditions that cannot be met by the standard construction specifications described above. For example, when a high-strength improved body is required, or when an improved body having a diameter other than the standard diameter is created. In this case, the specification is also set after performing the test construction, but after the construction period of about 1 to 4 weeks is provided after the construction, check boring and testing are performed, so it is very important to determine the specifications. It takes a lot of time and effort.

  Therefore, in view of the above-mentioned problems of the prior art, the object of the present invention is to control the improved diameter and improved body strength in the high-pressure jet stirring method, respectively, and to create a high-quality improved body at low cost. It is to provide a method that can set various construction specifications.

  Such an object is to monitor the ground cutting state by the hardened material jetted from the injection pipe at a high pressure, and to ensure the desired improved diameter and / or improved body strength, the rotational speed and the injection pressure of the injection pipe. This is achieved by a method for setting the construction specifications of the high-pressure jet agitation method that determines one or more of the discharge amount of the curing material.

  In this setting method, the desired improved diameter is, for example, a diameter within a range between a preset lower limit value and upper limit value.

  In the setting method, it is preferable that the monitoring is performed for each soil layer or depth, and one or more of the rotation speed, the injection pressure, and the amount of the hardened material discharged are determined for each soil layer or depth. .

  In the setting method, it is preferable that the time per step is determined based on one or two or more of the determined rotation speed of the injection tube, the injection pressure, and the amount of the hardened material discharged and the number of cuttings per step.

  Further, in the above setting method, when the construction is performed based on one or more of the determined rotational speed of the spray pipe, spray pressure, and curing material discharge amount, the amount of solidified material per volume of the improved body to be formed is a desired amount. It is preferable to determine the time per step so that

  In the above setting method, it is preferable that the raising time of the injection pipe is determined based on the time per step and the step length.

  The above-mentioned object is achieved by the improved strength setting method of the high-pressure jet agitation method, which determines the time per step by the jet pipe so that the amount of solidified material per volume of the improved product to be produced reaches a desired amount. The

  In the present invention, the ground cutting state by the hardened material jetted from the injection pipe at high pressure (for example, the ground cutting distance by the hardener jet) is monitored, and according to the situation, the rotation speed of the injection pipe, the injection pressure, the amount of the hardened material discharged By adjusting one or more of the values, an optimum value is determined. Since the “rotation speed”, “injection pressure”, and “curing material discharge amount” as variable elements affect the improved diameter and improved body strength of the improved body to be created, according to the present invention, the improved diameter and improved body strength are improved. One or both can be controlled. In addition, as a result of controlling the improved diameter in this way, it is possible to create an improved body of a complete lap without incurring the above-mentioned column-in-column construction failure even when a lap arrangement is adopted for improving the bottom plate or the like. .

  In the present invention, the design improvement diameter is set between a preset lower limit value and upper limit value. In this way, by providing a range for the allowable value of the design improvement diameter, it becomes easy to optimize the rotation speed, the injection pressure, and the hardener discharge amount of the injection pipe.

  In the present invention, the monitoring described above is performed for each soil layer or depth. Thereby, since an optimal construction specification can be set for each soil layer or depth, the construction speed is increased and the construction cost is reduced. In addition, by setting the optimum construction specifications for each soil layer or depth, the amount of mud drained throughout the construction is greatly reduced, so it is possible to reduce the environmental burden and in addition to the burden of mud disposal costs. Therefore, the construction period can be shortened and the construction cost can be reduced. Furthermore, since a homogeneous improvement body with a uniform diameter can be created even in an alternating layer ground, the amount of hardened material can be saved as compared with the conventional one, and the construction cost is reduced.

  Moreover, in this invention, the time per step by an injection tube is determined so that the amount of solidification materials per volume of the improvement body to produce | generate may reach desired amount. Thereby, the improvement body provided with required intensity | strength can be created.

It is a flowchart which shows the flow of the setting method of the construction specification of a high pressure injection stirring method. It is a figure which shows the way of thinking of the normal mixture ratio in a high pressure jet stirring method. It is a figure which shows the view of the amount of unit solidification materials in a high pressure injection stirring method. It is a figure which shows the view of the mixture ratio in the case of injecting in multiple times by a high pressure injection stirring method. It is a figure which shows the influence which a rotational speed has on the ground cutting distance (distance cut by the hardening material jet from an injection pipe). It is a schematic diagram which shows the mode at the time of measurement using a monitoring apparatus. It is a figure which shows the mode of the test construction using a monitoring apparatus. It is a graph which shows the example of an ideal measurement of a sound volume level in measurement using a monitoring device. It is process drawing which shows the mode of the ground improvement by a high pressure jet stirring method. It is a top view which shows a mode that the construction failure of the column in column arose and adjacent pile cannot be constructed.

  First, construction specifications that affect the “improved diameter” and “improved strength” in the high-pressure jet agitation method will be described.

(Construction specifications affecting the improved diameter)

  In a general high-pressure jet agitation method, for example, the injection pressure P and the curing material discharge amount Q are made constant, and the pull-up time v is changed. In addition, because of the characteristics of the high-pressure jet agitation method, it is not possible to replace the spray nozzle or change the nozzle diameter in the middle of construction, so while maintaining one of the injection pressure P and the curing material discharge amount Q during construction It is not possible to change only the other.

Usually, in the high-pressure jet agitation method, a pull-up time v is set according to soil quality, ground strength (N value), and improved diameter. Therefore, as shown below, another specification (the number of rotations Nr) is determined from the pulling time v.
(1) The time per step Tst is determined from the pull-up time v and the step length Lst (number of steps per 1 meter Nst). (Tst = v / Nst = v × Lst)
(2) The rotational speed Tr (or rotational speed Nr) is obtained from the time per step Tst, the number of times of cutting Nc and the number of nozzles Nn. (Tr = Tst × Nn / Nc)
That is, the pulling time, step length, and number of nozzles are preset values, and the rotation speed (or rotation speed) is a calculated value calculated from these set values.

  The following table shows an example in which construction specifications are set according to the above procedure.

(Example of setting construction specifications)

(Construction specifications affecting the improved strength)

The hardener contains water and a solidifying material.
The solidifying material is composed of, for example, cement or an admixture.

  In a general high-pressure jet stirring method, the improvement strength is not set for each site, but the improvement strength is set according to the ground conditions and the construction purpose. That is, an indoor blending test is not performed as in the case of a mechanical deep mixing method (DJM method, CDM method, etc.), and the amount of solidified material corresponding to the improved strength is not set. For this reason, in order to set to arbitrary intensity | strength, the solidification material quantity (blending | mixing) in a hardening material is not changed. When it is necessary to cope with special ground or have low strength, special hardeners are used, and these materials are more expensive than general materials.

(Method for setting construction specifications of the high-pressure jet stirring method in this embodiment)
Next, the setting method of the construction specification of the high-pressure jet stirring method in this embodiment will be described.
The construction specification setting method in the present embodiment includes three processes of “prior confirmation”, “test construction”, and “specification determination” as main processes, as shown in FIG.

In the “preliminary confirmation” process, a compounding test is performed to obtain the “solidifying material amount Cclm per volume of the improved body” for achieving the target strength, and based on the result, the minimum time per step Tst (min) Ask for.
In the “test construction” process, the ground cutting state by the hardened material injected from the injection pipe at a high pressure is monitored to determine the rotation speed Tr of the injection pipe so as to ensure a desired improved diameter.
In the “specification determination” process, the time Tst per step is confirmed based on the rotational speed Tr of the injection tube and the number of cuttings Nc per step, and the time Tst per step (or the minimum value Tst (min)) and the step length Based on Lst, the injection pipe pull-up time v is determined.

  Hereinafter, each process will be described.

(Pre-check process)
First, a blending test is performed <Procedure S11 in FIG. 1> to obtain "the amount of solidified material Cclm per volume of improved body" for achieving the target strength <S13>.

Subsequently, the injection amount Vjg per meter is obtained from the solidified material amount Cclm per volume of the improved body, the solidified material amount C in the cured material, and the improved body volume Vclm per meter <S15>. Calculation of the injection amount Vjg per meter is based on the following equation.
Vjg = Cclm x Vclm / (C-Cclm)
* Cclm = C × Vjg / (Vclm + Vjg)

Next, a minimum value Tst (min) per step is obtained from the injection amount Vjg per 1 m, the number of steps Nst per 1 m (step length Lst), and the cured material discharge amount Q <S17>. The calculation of the minimum value Tst (min) per step is based on the following equation.
Tst (min) = Vjg × Lst / Q = Vjg / (Q × Nst)

In addition, as shown in FIG. 2, the concept of the normal blending ratio in the high-pressure jet agitation method is as follows. decide.
On the other hand, in the case of this embodiment, as shown in FIG. 3, the amount of solidified material in the volume of the improved body is set to a predetermined ratio (a ratio satisfying the design strength) while considering the amount of mud. Determine the ratio.

(Test construction process)
According to the experiment by the applicant of the present application, it has been confirmed that the rotation speed Tr (rotational speed Nr) of the injection tube affects the ground cutting distance (cutting diameter) due to the hardening material jet from the injection nozzle.
That is, as shown in FIG. 5 (a), in the state where the injection tube 7 is not rotating, when the hardened material is injected, the cutting energy (vector in the radial direction) decreases as the distance from the injection tube 7 increases. A constant ground cutting distance is ensured. As shown in FIG. 5 (b), when the injection tube 7 is rotated while being injected, a rotational force (concentric vector) acts due to the rotation, and the apparent hardener jet, which is the resultant force, is Gradually, it becomes sideways, and cutting energy attenuates as it moves away from the injection tube 7. Therefore, the ground cutting distance in the rotating state of FIG. 5B is shorter than that in the non-rotating state of FIG.
Furthermore, when the injection tube 7 is rotated at a higher speed as shown in FIG. 5 (c), the ground cutting distance is further shortened compared to the low-speed rotation state of FIG. 5 (b).
Therefore, if the rotation speed Tr (s / rotation) of the injection pipe 7 is changed under the condition that the injection pressure P (MPa) and the hardener discharge amount Q (m ³ / s) are kept constant, the change amount Accordingly, the ground cutting distance due to the hardener jet changes, so it can be seen that the ground cutting distance (that is, the improved diameter) can be controlled by adjusting the rotation speed.

In addition, according to the experiment conducted by the applicant of the present application, when the injection pressure P (MPa) and the hardener discharge rate Q (m ³ / s) are changed, the ground cutting distance and improved body strength due to the hardener jet are affected. Has been confirmed. In addition, because of the characteristics of the high-pressure injection agitation method, it is not possible to change the injection nozzle or change the nozzle diameter in the middle of construction, so if the injection pressure P (MPa) is changed, the curing material discharge amount Q ( m ³ / s) will also change.

Then, one or more of the rotation speed Tr (s / rotation), injection pressure P (MPa), and hardener discharge rate Q (m ³ / s), which are variable elements, are used as variables and adjusted. By doing this, it can be seen that both or one of the improved diameter and improved body strength of the high-pressure jet stirring method can be controlled during construction. For example, by optimizing all of rotation speed Tr (s / rotation), injection pressure P (MPa), and curing material discharge rate Q (m ³ / s), an improved body with the same diameter and the same strength in the depth direction Can be created. In addition, by applying the above specification setting, it is possible to create an improved body having the same improved diameter in the depth direction and different strength in the depth direction, or an improved body having the same strength in the depth direction and different diameter in the depth direction. .

  However, in order to control the improved diameter and improved body strength during construction as described above, it is necessary to have a means to grasp the ground cutting state (ground cutting distance by the hardener jet) in real time from the hardener jet from the injection pipe. It becomes. Therefore, in the test construction process, the test construction is performed using the monitoring device shown in FIGS.

In the process of this test construction, initially, and drilling a vertical hole in the point of the lower and upper limit values of the design improvements diameter (point from the center of the improvements object distance r _A and the distance r _B), 6 and 7 As shown in the drawing, a lower limit measurement tube 24 and an upper limit measurement tube 34 are installed in each hole portion <S21 in FIG. 1>. The built-in measurement pipes 24 and 34 are equipped with measurement sensors 21 and 31 for grasping the ground cutting distance by the hardener jet.

  Subsequently, test construction is started <S23 in FIG. 1>, and the ground cutting state is monitored using the measurement sensors 21 and 31 for each soil layer or depth in the process <S25>. Then, as specifications for each soil layer or depth, the rotation speed Tr (rotation speed Nr), the injection pressure P, and the curing material discharge that are detected by the measurement sensor 21 on the lower limit side and not detected by the measurement sensor 31 on the upper limit value side. Set to quantity Q <S27>.

  Hereinafter, a specific configuration of the monitoring apparatus and details of a monitoring method using the same will be described.

(Monitoring device)
In the present invention, the ground cutting state by the hardened material jetted from the injection pipe at a high pressure is monitored, and the rotation speed of the injection pipe is adjusted in real time and set to an optimum value so as to ensure a desired improved diameter. Alternatively, in order to ensure a desired improved diameter and improved body strength, the rotational speed of the injection pipe, the injection pressure, and the discharge amount of the cured material are adjusted in real time, and each is set to an optimum value.
In order to monitor the ground cutting state in real time, the monitoring device 1 shown in FIGS. 6 and 7 is used.
FIG. 6 shows a state during measurement using the monitoring device 1.
FIG. 7 shows the entire test construction using the monitoring device 1.

As shown in FIG. 6 and FIG.
A lower limit measurement tube 24 (built-in tube) equipped with a measurement sensor 21;
An upper limit measurement measuring pipe 34 (built-in pipe) provided with a measuring sensor 31;
Suspension cables 22 and 32 for suspending the measurement sensors 21 and 31 in the measurement tube;
Winding devices 25 and 35 for raising and lowering the measurement sensors 21 and 31 via the suspension cable;
-It has the information processing apparatus 4 which records the data measured by the measurement sensors 21 and 31, and performs information processing etc. using the measurement data.

  The suspension cables 22 and 32 have a role of suspending the measurement sensors 21 and 31 in the measurement tubes 24 and 34. The suspension cables 22 and 32 are attached to hoisting devices 25 and 35 installed on the ground surface side so that the hoisting and feeding can be performed. By operating the hoisting devices 25 and 35 as the injection pipe 7 is lowered and raised, the measurement sensors 21 and 31 in the measurement pipe can be raised and lowered so as to follow the movement of the injection pipe 7.

The lower limit for measurement instrumentation tube 24, in the case of setting the lower limit of the design improvements diameter 2r _A, is inserted into a position at a distance r _A from improved body center of reclamation schedule. The lower limit here is the lower limit of the design improvement diameter allowed in construction.
When the upper limit value of the design improvement diameter is set to 2r _B , the upper limit measurement tube 34 is inserted at a position separated by a distance r _B from the center of the improvement body to be created. An upper limit here is an upper limit of the design improvement diameter accept | permitted in construction.

In the test construction, the rotational speed of the injection pipe 7, the injection pressure P, and the curing material discharge amount Q are determined so that the design improved diameter r _D within the range of the lower limit value 2r _A to the upper limit value 2r _B is secured. To do. Alternatively, is secured design improvements diameter r _D, and, as required improvement strength is ensured, the rotation speed of the injection tube 7, the injection pressure, to determine the cured material discharge rate. As described above with reference to FIG. 5, the improved diameter and improved body strength can be controlled by adjusting the rotation speed of the injection tube, the injection pressure, and the discharge amount of the hardener. Usually, design improvements diameter r _D is set at a lower value r _A.
The lower limit value 2r _A and the upper limit value 2r _B of the design improved diameter are not particularly limited, and can be set to arbitrary values according to the ground conditions and the like.

  The measurement sensors 21 and 31 can be composed of, for example, a rubber packer and a sound collecting microphone housed in the rubber packer. In this case, the rubber packer expands and contracts in the measurement tube by the air sealed from the ground via the air hose, and the rubber packer expands and adheres closely to the inner wall of the measurement tube. Can be fixed to.

  When the main part of the measurement sensors 21 and 31 is constituted by a sound collecting microphone, the ground cutting state by the injection pipe 7 is obtained by collecting and monitoring the cutting sound that the hardened material jet 5 from the injection nozzle hits the measurement pipes 24 and 34. Can be grasped in real time.

  In this embodiment, when any one or two or more of the rotational speed of the injection pipe 7, the injection pressure, or the hardener discharge amount is changed, the ground cutting distance by the hardener jet 5 from the injection nozzle changes accordingly. Therefore, the volume level measured by the measurement sensors 21 and 31 changes according to the rotation speed (ground cutting distance). Therefore, by monitoring the volume level of the cutting sound collected by the measurement sensor 21 of the lower limit measurement tube 24, it is possible to determine in real time whether or not an improved diameter exceeding the lower limit is ensured. By monitoring the volume level of the cutting sound collected by the measuring sensor 31 of the measuring tube 34 for measuring the upper limit value, it is possible to determine in real time whether the upper limit value or an improved diameter lower than the upper limit value is secured.

  Therefore, while monitoring the volume level measured by each of the measurement sensors 21 and 31, by adjusting any one or two or more of the rotation speed, the injection pressure, and the hardener discharge amount of the injection pipe 7, the ground condition ( Regardless of the soil quality or N value), the improved diameter can be kept between a predetermined upper limit value and lower limit value during construction.

  In the present embodiment, the sound collecting microphone is exemplified as a component of the measurement sensor. However, the measurement sensor may be configured using other detection means. For example, in addition to the sound sensor other than the sound collecting microphone described above, various detection means that can grasp the arrival of the curing material jet, such as a vibration sensor that detects the vibration level and a temperature sensor that detects the reaction heat of the curing material, are used. It is possible to configure a measurement sensor.

(Test construction using monitoring device)
Next, based on FIG.1 and FIG.7, the specific procedure of the test construction using the monitoring apparatus 1 of the said structure is demonstrated.

First, the drilling a vertical hole in the point of the lower and upper limit values of the design improvements diameter (point from the center of the improvements object distance r _A and the distance r _B). Boring can be used for drilling vertical holes. Then, the above-described lower limit value measuring tube 24 and upper limit value measuring tube 34 are installed in the vertical hole, and a sealing material is filled between each measuring tube and the vertical hole <S21 in FIG. 1>. The measuring tubes 24 and 34 built in each vertical hole can be fixed when the sealing material is solidified.

  Next, as shown in FIG. 7, the construction machine 6 is installed at the center of the formation position of the ground improvement body, and the injection pipe 7 is suspended and built in the construction machine by a crane. And drilling water is discharged from the front-end | tip of the injection pipe 7, and it inserts to the planned depth in the ground, rotating the injection pipe 7 with the construction machine 6. FIG.

  Next, the hoisting devices 25 and 35 are installed at the installation points of the lower limit value measuring tube 24 and the upper limit value measuring tube 34, and the suspension cables 22 and 32 are unwound from the hoisting devices. The measurement sensors 21 and 31 are hung on the side.

  The measurement sensors 21 and 31 connected to the suspension cables 22 and 32 are suspended and positioned to the same depth (stage) as the injection nozzle at the tip of the injection pipe 7. When the measurement sensors 21 and 31 are composed of, for example, a rubber packer and a sound collecting microphone housed in the rubber packer, the packer is inflated by enclosing air from the ground via an air hose in the packer of the sound collector. Let it fix.

  After completing the above procedure, the preparation for the test construction is completed. Then, the test construction is started by the following procedure <S23 in FIG. 1>.

  A hard material is sprayed from the spray nozzle at a high pressure through the spray pipe 7, and the ground and the hard material are rotated by rotating the spray pipe 7 at a constant speed by the construction machine 6 while cutting and collapsing the raw ground by the strong energy. A ground improvement body is created by forcibly stirring and mixing.

At this time, if the hardening material jet 5 from the injection nozzle at the tip of the injection pipe reaches the point of the measurement sensor 21 of the measurement pipe 24 for the lower limit measurement, the ground at that point is cut and collapsed. The hardening material jet 5 hits the measurement measuring tube 24, and the volume level measured by the measurement sensor 21 is increased. Therefore, it can be determined that the volume level of this time, ground cutting distance due to the curing material jet 5 is above the lower limit r _A. An ideal measurement example of the volume level measured by the measurement sensor 21 at this time is shown in FIG. According to the lower limit value line illustrated in the figure, since the value measured by the measurement sensor 21 for lower limit measurement shows a peak value at a constant period, the ground cutting distance by the hardener jet 5 is lower limit r. You can see that it exceeds _A.
On the contrary, if the hardened material jet 5 from the injection nozzle at the tip of the injection pipe does not reach the point of the measurement sensor 21 of the measurement pipe 24 for the lower limit value measurement, the ground at that point is not cut and collapsed. Since the hardening material jet 5 does not hit the value measuring measurement tube 24, the volume level measured by the measurement sensor 21 remains low. Therefore, it can be determined that the volume level of this time, ground cutting distance due to the curing material jet 5 is below the lower limit r _A.
When the ground cutting distance is below the lower limit r _A , for example, the ground cutting distance can be extended by lowering the number of revolutions of the injection pipe 7 (see the relationship of FIG. 5 (c) → (b)). ). Alternatively, the ground cutting distance can be extended by increasing the injection pressure and the amount of the hardened material discharged while maintaining the rotation speed. Therefore, by adjusting one or two or more of the rotation speed of the injection pipe 7, the injection pressure, and the amount of hardened material discharged, the ground cutting distance can be extended, and the improved diameter and / or improved strength can be optimized.

Similarly, if the hardened material jet 5 from the injection nozzle at the tip of the injection pipe does not reach the point of the measurement sensor 31 of the upper limit measurement tube 34, the ground at that point is not cut and collapsed. Since the hardening material jet 5 does not hit the value measuring measurement pipe 34, the sound volume level measured by the measurement sensor 31 remains low. Therefore, it can be determined from the volume level at this time that the improved diameter is below the upper limit value r _B. Note that an ideal measurement example of the volume level measured by the measurement sensor 31 at this time is shown in FIG. According to the upper limit line illustrated in the figure, unlike the lower limit line described above, there is no significant variation in the value measured by the upper limit measurement sensor 31, so the ground due to the hardener jet 5 It can be seen that the cutting distance is below the upper limit value r _B.
On the contrary, if the hardening material jet 5 from the injection nozzle at the tip of the injection pipe reaches the point of the measurement sensor 31 of the measurement pipe 34 for measuring the upper limit value, the ground at that point is cut and collapsed. The hardening material jet 5 hits the measurement measuring tube 34, and the volume level measured by the measurement sensor 31 increases. Therefore, it can be determined from the volume level at this time that the improved diameter exceeds the upper limit value r _B.
When the ground cutting distance exceeds the upper limit value r _B , for example, the ground cutting distance can be suppressed by increasing the number of revolutions of the injection pipe 7 (see the relationship of FIG. 5 (c) → (b)). ). Alternatively, the ground cutting distance can also be suppressed by lowering the spray pressure and the discharge amount of the curing material while maintaining the rotation speed. Therefore, by adjusting one or more of the rotation speed, the injection pressure, and the hardener discharge amount of the injection tube 7, the ground cutting distance can be suppressed, and the improved diameter and / or improved strength can be optimized.

  In this way, by monitoring the sound data obtained through the measurement sensors 21 and 31 in real time, the rotation speed of the injection pipe is set so as to have an improved diameter that falls within the range of the lower limit value and the upper limit value set in advance. It is possible to optimize one or more of the injection pressure and the curing material discharge amount. Note that sound data obtained through monitoring can be digitized and recorded in the information processing apparatus.

  And if creation of the ground improvement body in the first stage is completed through the above procedure, the construction machine 6 is operated to step up the injection pipe 5 step by step to the second, third stage,. The step length (length per step) is set to a predetermined length. And the substantially cylindrical ground improvement body can be created by performing the process similar to the above in each stage.

  Further, during this period, the sound of the hardener jet 5 hitting the measurement tubes 24 and 34 is monitored by the sound collecting microphones of the measurement sensors 21 and 31 for each soil layer or depth (that is, at each stage) <S25 in FIG. 1>. Then, by adjusting the rotation speed of the injection tube 7 based on the volume, etc., the rotation speed, the injection pressure, and the amount of the hardened material discharged are adjusted so that a desired improved diameter and improved strength are obtained for each soil layer or depth. Optimized <S27 in FIG. 1>.

(Specification decision process)
Next, based on FIG. 1, a specification determination process following the test construction process described above will be described.

In this process, first, an improved body volume Vclm per meter is determined from r _A or r _B shown in FIG. The improved body volume Vclm is calculated by the following equation (1).
Vclm = r _B ² (or r _A ² ) × π × 1 (1)

Subsequently, using the rotational speed Tr obtained in the test construction procedure S27, the time per step Tst is obtained from the number of nozzles Nn and the number of cutting times Nc <S31 in FIG. 1>. The time per step Tst is calculated by the following equation (2).
Tst = Tr × Nc / Nn (2)

Subsequently, the time per step Tst obtained in step S31 is compared with the minimum value Tst (min) of the time per step obtained in step S17.
If the time per step Tst obtained in step S31 is greater than the minimum value Tst (min) of the time per step obtained in step S17, <Yes in S33>, and use Tst as the time per step <S37>. .
On the other hand, when the time per step Tst obtained in step S31 is smaller than the minimum value Tst (min) of the time per step obtained in step S17, <No in S33>, and Tst (min) is adopted as the time per step. . At this time, the rotational speed Tr is set to the value obtained in the test construction procedure S27, and the number of times of cutting Nc is increased so that Tst (min) = Tr × Nc / Nn is satisfied <S35>.

Next, the raising time v is determined from the “time per step Tst” and the “step length Lst (number of steps Nm per meter)” determined in the above procedure <S39>. The raising time v is calculated by the following equation (3).
v = Tst / Lst = Tst × Nst (3)

Finally, the injection amount Vjg per meter is obtained from the pull-up time v.
Calculation of the injection amount Vjg per meter is based on the following equation (4).
Vjg = Q × v (4)

  This completes the specification determination process.

(Application examples)
The above-described embodiment is an example, and the present invention described in the claims includes various application examples. For example, in order to further improve the strength of the improved body, it is possible to increase the amount of solidified material per volume of the improved body by increasing the amount C of the solidified material in the cured material (see FIG. 3). Moreover, the injection of the hardened material by step-up may be repeated a plurality of times to increase the amount of solidified material per volume of the improved body. In addition, the way of thinking of the blending ratio at the time of multiple injections is as shown in FIG.

DESCRIPTION OF SYMBOLS 1 Monitoring apparatus 4 Information processing apparatus 5 Curing material jet 6 Construction machine 7 Injection pipe 21 Measurement sensor 22 Hanging cable 24 Measuring pipe for lower limit measurement (built-in pipe)
25 Winding device 31 Measuring sensor 32 Suspension cable 34 Measuring tube for upper limit measurement (built-in tube)
35 Winding device

Claims (7)

  By monitoring the ground cutting state by the hardened material jetted from the injection pipe at a high pressure, the rotation speed of the injection pipe, the injection pressure, and the discharge amount of the hardener are adjusted so as to ensure the desired improved diameter and / or improved body strength One or two or more are determined, A method for setting construction specifications of the high-pressure jet stirring method.   The method for setting construction specifications of the high-pressure jet agitation method according to claim 1, wherein the desired improved diameter is a diameter within a range between a preset lower limit value and upper limit value.   The monitoring is performed for each soil layer or depth, and one or more of the rotation speed, the injection pressure, and the hardener discharge amount of the spray pipe are determined for each soil layer or depth. The setting method of the construction specification of the high-pressure jet stirring method according to 2.   In the method of setting the construction specifications of the high-pressure jet agitation method for stepping up the injection pipe step by step, the determined rotation speed, injection pressure, one or more of the discharge amount of the hardener, and the number of cuttings per step 4. The method for setting construction specifications of the high-pressure jet agitation method according to claim 1, wherein a time per step is determined based on the time.   In the setting method of the construction specifications of the high-pressure jet agitation method for stepping up the jet pipe step by step, when construction is performed based on one or more of the determined rotational speed, jet pressure, and curing material discharge amount of the jet pipe The construction specification of the high-pressure jet agitation method according to any one of claims 1 to 3, wherein the time per step is determined so that the amount of solidified material per volume of the improved body to be produced reaches a desired amount. Setting method.   The method for setting construction specifications of the high-pressure jet agitation method according to claim 4 or 5, wherein a pull-up time of the injection pipe is determined based on the time per step and the step length.   In setting the strength of the improved body of the high-pressure jet stirring method for stepping up the spray pipe step by step, the time per step by the spray pipe is determined so that the amount of solidified material per volume of the improved body to be produced reaches the desired amount. An improved body strength setting method for the high-pressure jet agitation method.