JP6556485B2 - Ground injection method - Google Patents

Description

  The present invention relates to a ground injecting method for creating a plurality of improved bodies on non-uniformly deposited natural ground or artificial ground created by pump dredging.

  The injection form in the ground injection is, for example, “penetration injection” in which pore water is infiltrated to replace the injection material without moving the soil particles in the ground, and “split injection” in which the injection material is injected while moving the soil particles. It is divided roughly into. “Split injection” means that the injection material is injected into the part other than the improved range, and there is a possibility that an unimproved part may be generated within the improved range. . Moreover, the injection | pouring of the injection material in "osmotic injection | pouring" uses the long binder whose gel time is about 60 to 1000 minutes, and is inject | poured statically at a low pressure compared with "split injection".

  When it is necessary to set the injection speed low in the injection to the ground having a low water permeability coefficient, the injection of the intermediate binder makes the gelled product thick during the injection and makes subsequent injection impossible. When the injection pressure is increased and the injection is continued, displacement is caused by splitting. For this reason, it is necessary to use a long binder to ensure “penetration injection”.

In sand ground that contains a large amount of fine particles with a hydraulic conductivity of about 5 × 10 ⁻⁴ to 1 × 10 ⁻³ cm / sec, the injection rate for ensuring infiltration is 4.5 L / in according to Maag's theory. If the injection is performed at an injection speed exceeding this in the vicinity of the structure, the chemical solution escapes outside the predetermined range due to split injection, and the structure is displaced.

  In recent years, the effectiveness of "dynamic injection" has been confirmed as a grout injection method for cracked rock masses containing many microcracks, and the number of applications has increased. “Dynamic injection” is a method of performing injection by superimposing a pulsation pressure having a specific frequency or several kinds of frequencies on the injection pressure.

  Examples of using “dynamic injection” include Patent Documents 1 to 3. In Patent Document 1, when cement or bentonite-based injection material (grouting material) is injected into a cracked rock mass, pulsation pressure having a specific frequency selected from a frequency range of 5 to 30 Hz is superimposed on the injection pressure. In addition, a technique for improving the permeability by exciting the constituent particles of the grout material is disclosed.

  Patent Document 2 discloses that in grouting in which a grout material is injected into a cracked rock and a sandy ground which is uniform in the vertical and horizontal directions, the injection pressure includes a long wave of 0.04 to 0.08 Hz and a short wave of 1 to 6 Hz. A technique is disclosed in which pulsation pressure due to a composite wave is applied in a superimposed manner to excite the constituent particles of the grout material to improve the permeability.

  Further, in Patent Document 3, in the ground injection method, the injection speed is increased or decreased in a cycle of 7 to 15 seconds, and the maximum value and the minimum value of the injection pressure are increased every time the increase and decrease are repeated. A technique for efficiently infiltrating an injection material into a target range by suppressing the development of split injection is disclosed.

Japanese Patent No. 3096244 Japanese Patent No. 5089430 Japanese Patent No. 3757400

However, in Patent Document 1 and Patent Document 2, the peak of the pulsation pressure is ± 0 in the injection of sand ground containing a large amount of fine particles having a water permeability of about 5 × 10 ⁻⁴ to 1 × 10 ⁻³ cm / sec. There is a problem that the injected material is injected outside a predetermined range because split injection occurs due to an excessively high pressure.

  In addition, Patent Document 2 and Patent Document 3 conduct a test intended to create a single improved body on a model ground that is uniform in the vertical and horizontal directions. There is no description of permeability.

  For example, an alluvial lowland along a river, where there is a high risk of liquefaction, forms sandy and cohesive soil with sediments transported and deposited by river flooding. In the soil injection method that creates multiple improvements in three dimensions to the unevenly deposited natural ground or artificial ground created with pump dredging, etc., when injecting into the ground evenly in the vertical and horizontal directions It is not difficult to imagine that the permeability is lower than that.

  Therefore, when the injection method disclosed in Patent Document 2 and Patent Document 3 is used as a ground injection method for three-dimensionally creating a plurality of improved bodies on the ground that is uniform in the vertical and horizontal directions, As the injection progresses, the water permeability of the entire target ground decreases, the pore water pressure gradually increases, and the shear strength of the ground decreases. Further, when the injection of the injection material is continued, when the injection progress rate reaches about 70% at the maximum, split injection occurs, the injection material is injected outside the predetermined range, and there is a risk that the ground and the structure will be displaced. Get higher. The same applies to the case where an improved body is created three-dimensionally and continuously on non-uniformly deposited natural ground or artificial ground created by a pump rod.

  The present invention relates to a ground injection method in which a plurality of improved bodies are three-dimensionally formed on non-uniformly deposited natural ground or artificial ground created by pump dredging, etc., injecting intermittently by repeating injection and interruption. An object of the present invention is to provide a ground injection method that has a reliable ground improvement effect in a short period of time without giving displacement.

According to one aspect, there is a ground injection method in which a plurality of improved bodies are three-dimensionally formed in the ground by injecting an injection material into a target region of the ground, and the injection material is injected into the ground. An injection step of injecting and an interruption step of interrupting the injection of the injection material after the injection step is executed are repeatedly executed, and the injection step has a trapezoidal waveform or a triangular waveform to increase the injection rate of the injection material. The injection step is performed by changing the absolute value of the time change rate of the injection rate of the injection material until the injection rate of the injection material reaches the maximum rate, and the injection rate of the injection material is the maximum speed. The absolute value of the time change rate of the injection rate of the injection material from the state to the time when the injection of the injection material is stopped is 5.56 × 10 ⁻³ L / sec ² or less, respectively, and the injection rate of the injection material The injection material until the maximum speed is reached. The absolute value of the time change rate of the injection pressure and the absolute value of the time change rate of the injection pressure of the injection material from when the injection rate of the injection material reaches the maximum speed until the injection of the injection material is stopped. It is characterized by being set to 0.5 MPa / second or less .

In the injection step, when the injection rate of the injection material is changed in the trapezoidal waveform, the injection rate of the injection material is q _p , the time rate of change of the injection rate is a _q , and the coefficient is α (α = 0 to 0). 1), the holding time Tp when the injection speed of the injection material becomes the maximum speed,
Tp = (q _p / 3a _q ) × α
It is preferable to set to.

In the interruption step, the injection of the injection material is interrupted when the injection rate of the injection material is q _p , the rate of time change of the injection rate is a _q , and the coefficient is β (β = 1 to 6). Time Ti,
Ti = (q _p / 3a _q ) × β
It is characterized by setting to.

  Further, the injection material is sequentially injected at a plurality of different depths while reducing the depth of injection of the injection material.

  The injection material may be sequentially injected at a plurality of different depths while increasing the depth at which the injection material is injected.

  Further, the injection rate of the injection material is gradually increased or decreased based on the displacement of the structure adjacent to the target area of the ground, the displacement of the ground, the maximum velocity of the injection material, and the injection pressure of the injection material. It is characterized by performing.

  In this case, it is preferable that the maximum speed in the injection speed of the injection material is regulated based on the displacement of the structure adjacent to the target area of the ground after the injection of the injection material and the displacement of the ground.

  According to the ground injection method of the present disclosure, it is possible to obtain a reliable ground improvement effect in a short period of time without giving displacement to the ground by repeatedly injecting and interrupting injection of the injection material. .

It is a figure which shows the procedure of the ground injection | pouring method using a double pipe strainer construction method. It is a functional block of the construction system. (A) is a schematic diagram which shows the relationship between the injection | pouring speed | rate and elapsed time in an inching injection method, (b) is a schematic diagram which shows the relationship between the injection | pouring pressure in an inching injection method, and elapsed time. It is sectional drawing which shows the structure of a model ground. It is a figure which shows the position of the concrete gauge and displacement meter installed in the mortar upper surface. (A) is a graph which shows the change of the stress in case 1, (b) is a graph which shows the displacement in case 1. FIG. (A) is a graph which shows the change of the stress in case 2, (b) is a graph which shows the displacement in case 2. (A) is a graph which shows the change of the stress in case 3, (b) is a graph which shows the displacement in case 3. (A) is a graph which shows the change of the stress in case 4, (b) is a graph which shows the displacement in case 4. (A) is a graph which shows the change of the stress in case 5, (b) is a graph which shows the displacement in case 5. It is sectional drawing which shows the state of the uniting material in a model ground when the test of case 1 to case 5 is implemented. In the case of injecting an injection material using the inching injection method, when the stress value reaches the control value, it is a schematic diagram showing an example of restricting the injection speed based on the reduction rate set for each control value. . It is a table | surface which shows the maximum stress when the test of case 6 to case 7 is implemented, the maximum displacement, and an injection | pouring progress rate.

  Hereinafter, the ground injection method of the present invention will be described. Examples of the ground injection method include methods such as a double tube strainer method, a double tube double packer method, a single tube rod method, and a bundling tube multi-point injection method. In addition, since these construction methods are well-known, description is abbreviate | omitted for details. Hereinafter, the case where a double pipe strainer construction method is used as a ground injection method of this embodiment is explained. In addition, it is also possible to implement this invention using construction methods, such as a double pipe double packer construction method, a single pipe rod construction method, and a bundling capillary multi-point injection construction method.

  As shown in FIGS. 1 (a) to 1 (c), the double-pipe strainer method (single-phase type) is a rotary type with a double-pipe boring rod 10 composed of an inner pipe and an outer pipe. A drilling machine (rotary boring machine) 11 is used to drill a hole to a predetermined depth in the ground while feeding water for drilling into the boring rod 10, inject a predetermined amount of the injected material, and then pull out the boring rod 10 by a predetermined amount. . After the injection material is injected by the boring rod 10, the improvement body 13 can be three-dimensionally formed in the injection range 12 by repeating the operation of raising the boring rod 10 by a predetermined amount.

  In FIG. 1, after drilling to a predetermined depth of the ground, a predetermined amount of the injection material is injected, and the injection material is sequentially injected toward the mouth side of the injection hole while pulling out the predetermined amount of the boring rod 10. The method (step-up method) for creating the improved body 13 three-dimensionally on the ground is described. However, as a method of three-dimensionally constructing the improved body 13 on the ground, in addition to the step-up method, after injecting from the inlet side of the injection port, the injection material is sequentially applied to a predetermined depth while drilling. It is also possible to use an injection method (step-down method).

  Examples of the injection material include a water glass type solution type, a suspension type, a soil purification material, a heavy metal insolubilizing material, and a polyvalent metal salt aqueous solution type acrylic acid solution. As the injection material, for example, a long-bound material that solidifies when several tens of minutes or more have passed, for example, a middle-bound material that solidifies when several tens of minutes or more have passed, a quick-set material that solidifies within several seconds to tens of seconds, or the like Can be mentioned.

  The injection material is injected into the ground using a mixing method of one shot, 1.5 shot, or two shots described below. For example, in the case of one shot, it is a method in which a chemical solution mixed at a predetermined blending ratio is mixed in advance into a single liquid state and injected into the ground in the mixed state. When using the one-shot injection method, a long binder is used as the injection material.

  In the case of 1.5 shots, the main material and the hardening material constituting the injection material are sent to the injection pipe head through separate paths, and the main material and the hardening material are merged at the injection pipe head, so that the inside of the injection pipe Injecting while mixing. When the 1.5 shot injection method is used, a long binder or a middle binder is used as the injection material.

  In the case of two shots, the main material and the hardening material constituting the injection material are respectively sent to the injection pipe through different paths, and mixed and mixed at the discharge port of the injection pipe for injection. In the case of using the injection method by two shots, as the injection material, it is possible to use an instantaneous setting material in addition to the long binding material and the intermediate binding material.

  FIG. 2 is a functional block diagram showing an example of a construction system used when three-dimensionally building an improved body on the ground. In the construction system shown in FIG. 2, a case where a plurality of improved bodies are created is described. In FIG. 2, the configuration for controlling the rotary drilling machine 11 and the rotary drilling machine 11 is omitted.

  The construction system 20 includes a dynamic management device 21, an injection management device 22 connected to the dynamic management device 21 in a local area, and a recording PC 23.

  The dynamic management device 21 receives the measurement data from the measuring device 24 from the recording PC 23 and uses the received measurement data to limit the number of rotations of the infusion pump 25 corresponding to the measuring device 24 and determine a stop instruction. The dynamic management device 21 sequentially compares the regulation value and the measurement data, and when the measurement data exceeds the regulation value, instructs the injection management device 22 to regulate the rate of decrease between 0 and 99%. Do. The multiplication factor can be set and changed for each of the infusion pumps 25.

  The injection management device 22 acquires flow rate pressure, instantaneous flow rate, and integrated flow rate measurement data from the flow rate / pressure measurement device 26 and displays the flow rate pressure, instantaneous flow rate, and integrated flow rate measurement data on a monitor or the like. The infusion management device 22 is connected to each infusion pump 25 via an inverter 27, and transmits ON / OFF and frequency control signals to each infusion pump 25 via the inverter 27. Further, when a limit / stop instruction signal (multiplication rate) of the number of rotations of the infusion pump 25 is transmitted from the dynamic management device 21, the infusion management device 22 multiplies the set flow rate by the multiplication rate in the infusion pump 25. A frequency control signal is output to the infusion pump 25 so as to obtain a numerical value.

  The recording PC 23 acquires the measurement data from the measuring instrument 24 and displays the stress and displacement data when the injection material is injected on a monitor or the like. The recording PC 23 records the measurement data and transmits the measurement data to the movement management device 21.

  The measuring device 24 is provided in the vicinity of the injection port, and measures stress and displacement of the ground when the injection material is injected. The injection pump 25 is provided between the grout mixer and the flow rate / pressure measuring device 26, and is directed to the boring rod 10 attached to the rotary drilling machine 11 with water for drilling at the time of drilling and chemicals at the time of injection of the injection material. And send it in.

  The flow rate / pressure measuring device 26 is provided in a hose that connects the injection pump 25 and a swivel provided at the upper end of the boring rod 10 attached to the rotary drilling machine 11.

  Next, an injection method for injecting the injection material into the ground will be described. In the present embodiment, an intermittent injection (inching injection) method is employed in which after the injection material is injected, the operation of temporarily stopping the injection of the injection material is repeatedly performed. FIG. 3 shows temporal changes in the injection rate and injection pressure in the inching injection method. In addition, the case where 2 shots are employ | adopted as a mixing method of an injection material is shown.

Step 1: The ground is drilled using the rotary drilling machine 11 to which the boring rod 10 is attached.
Process 2: The main material and the hardened material are simultaneously pumped from the outer tube and the inner tube of the boring rod, respectively, and the main material and the hardened material are mixed by a grout monitor provided at the discharge port of the boring rod 10, and the tip of the boring rod 10 is mixed. The injection material is injected into the ground.
Step 3: After the injecting material has infiltrated a predetermined amount, the injecting material is temporarily stopped.
Process 4: Re-drilling the ground using the boring rod 10 attached to the rotary drilling machine 11.
When Step 2 to Step 4 are repeated and predetermined injection is completed, the injection material injection method is completed.

As shown in FIGS. 3A and 3B, when the injection material is injected into the ground, the number of revolutions of the injection pump is controlled so that the injection speed of the injection material becomes a preset peak value. . By controlling the injection pump, when the injection speed of the injection material becomes the maximum speed (peak value), the injection pressure of the injection material also becomes the maximum pressure (peak value). In FIG. 3 (a) and FIG. 3 (b), “MAX” indicates a peak value. Here, the absolute value of the time change rate ΔV ₁ (= (V _max −V ₀ ) / T ₁ ) of the injection rate from the start of the injection of the injection material until the injection rate reaches the peak value is 5.56. × 10 ^-3 L / sec ² or less, the absolute value of the time rate of change of the injection pressure _{ΔP 1 (= (P max -P} 0) / T 1) is set below 0.5 MPa / sec.

Further, as shown in FIGS. 3A and 3B, when the injection of the injection material is interrupted, the rotation speed of the injection pump is controlled so that the injection speed of the injection material becomes zero. Therefore, the injection pressure of the injection material becomes zero by controlling the number of revolutions of the injection pump so that the injection rate of the injection material becomes zero. In the process of stopping the step of injecting the injection material, the absolute value of the rate of change ΔV ₂ (= (V ₀ −V _max ) / T ₂ ) of the injection rate until the injection rate reaches 0 from the peak value is 5 .56 × 10 ⁻³ L / sec ² or less, and the absolute value of the time change rate ΔP ₂ (= (P ₀ −P _max ) / T ₂ ) of the injection pressure is set to 0.5 MPa / sec or less. .

  Hereinafter, in order to prove the permeability and displacement suppression effect of the injection material in the injection method of the present invention, a test using a model ground was conducted.

[Test 1]
As shown in FIG. 4, the model ground 29 is provided with a gravel drainage layer 31 at the bottom layer of a cylindrical mold (drum can) 30 having a diameter of 56 cm and a height of 74 cm, and the drainage layer 31 is filled with dredged sand 32. Drain pipes 33 and 34 are provided on the side surfaces. The drain pipes 33 and 34 are used for water injection at the time of saturation and for drainage at the time of injection. The cinnabar 32 has a soil particle density Gs = 2.647 g / cm ³ , a fine particle content Fc = 6.6%, and a uniformity coefficient Uc = 1.6. The cinnabar 32 was tamped to a layer thickness of 74 cm in the model ground 29 with a relative density Dr = 80%. A mortar 35 having a thickness of 5 cm is provided on the top of the cinnabar 32. The uniaxial compressive strength of the mortar 35 is set to 46.5 N / mm ² .

  As shown in FIG. 5, in order to monitor the behavior of the injection material during injection, the top surface of the mortar 35 is concrete in the 0 ° direction when the upper direction on the paper surface from the center of the injection port 36 is 0 °. Gauges C-0-1, C-0-2, C-0-3 were arranged. Concrete gauges C-0-1, C-0-2, and C-0-3 were installed at positions of 5 cm, 14 cm, and 23 cm from the center of the injection hole 36 toward the outer peripheral side.

  Further, concrete gauges C-90-1, C-90-2, and C-90-3 were arranged in a direction rotated 90 ° clockwise with respect to the 0 ° direction (hereinafter, 90 ° direction). The concrete gauges C-90-1, C-90-2, and C-90-3 were installed at positions of 5 cm, 14 cm, and 23 cm from the center of the injection hole 36 toward the outer peripheral side. Concrete gauges C-0-1, C-0-2, C-0-3, C-90-1, C-90-2, C-90-3 include, for example, surface strains of steel, concrete, and mortar. And foil gauges based on polyester resin used for short-term measurement of wood.

  Similarly, displacement meters H-0-2 and H-0-3 were installed at positions of 14 cm and 23 cm from the center of the injection hole 36 toward the outer peripheral side in the 0 ° direction described above. Further, displacement meters H-90-2 and H-90-3 were installed at positions of 14 cm and 23 cm from the center of the injection hole 36 toward the outer peripheral side in the 90 ° direction.

  Hereinafter, in addition to the static injection method and the dynamic injection method, the inching injection method shown in the present embodiment was used as the injection method for the injection material. In addition, the injection material uses a water glass type solution type binder. In cases 4 and 5, the number of revolutions of the injection pump is controlled so that the absolute value of the temporal change in the injection pressure of the injection material is 0.5 MPa / second or less.

  For all cases from case 1 to case 5, the step-down method was performed in which the injection material was injected at the positions of the 1 step, 2 step, and 3 step shown in FIG.

[Case 1]
Injection method: Static injection Injection speed: 4.5 L / min [Case 2]
Injection method: Static injection Injection speed: 9.0 L / min [Case 3]
Injection method: Dynamic injection Injection speed: Minimum speed 4.0 L / min
Maximum speed 8.0L / min
Period 7 seconds [Case 4]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.075 L / sec (4.5 L / min)
Absolute value of rate of change of injection rate with time: 5.56 × 10 ⁻³ L / sec ²
Peak retention time factor: 1
Interrupt time factor: 1
Peak speed holding time: 4.5 seconds Interruption period: 4.5 seconds [Case 5]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.075 L / sec (4.5 L / min)
Absolute value of rate of change of injection rate with time: 5.56 × 10 ⁻³ L / sec ²
Peak retention time factor: 1
Interrupt time factor: 6
Peak speed holding time: 4.5 seconds Interruption period: 27 seconds

In cases 4 and 5, the peak speed holding time Tp and the interruption time Ti are expressed by the equations (1) and (2).
Tp = (q _p / 3a _q ) × α (1)
Ti = (q _p / 3a _q ) × β (2)

Here, q _p is the maximum injection rate, a _q is the rate of change of the injection rate with time, α is the peak retention time coefficient, and β is the interruption time coefficient. The peak holding time coefficient α is set to a value between 0 and 1, and the interruption time coefficient β is set to a value of 1 to 6.

FIGS. 6 to 10 show changes in stress and changes in displacement in cases 1 to 5. FIG. In each figure, “1 STEP”, “2 STEP”, and “3 STEP” indicate the order in which the injection materials are injected. Here, the position indicated by “1 STEP” is a position having a depth of 10 cm from the upper surface of the cinnabar 32 shown in FIG. “2STEP” is a position 25 cm deep from the upper surface of the cinnabar 32 shown in FIG. Further, “3 STEP” is a position 40 cm deep from the upper surface of the cinnabar 32 shown in FIG. Note that when the stress displacement exceeds 1.5 N / mm ² , for example, it can be determined that split injection has occurred in addition to osmotic injection.

As shown in FIG. 6, in case 1, an increase in stress occurs from the first step, and a displacement occurs when the stress exceeds ² N / mm ² in the second step. In the third step, the displacement reaches a maximum of 50 mm.

  As shown in FIG. 7, in the case 2, the stress increases immediately after the start of the injection of the first-step injection material, and the displacement increases with a slight delay. After the displacement reaches 28 mm in the second step, no large displacement fluctuation is observed.

  As shown in FIG. 8, in case 3, from the first step to the first half of the second step, there is no increase in stress and no displacement, the development of split injection is suppressed, and osmotic injection is performed efficiently. I can ask. Stress increases from the middle of the second step, but no displacement occurs. The stress converges after the completion of the second step injection, but the stress significantly increases immediately after the start of the third step injection, and at the same time a displacement occurs. The timing at which the stress increases overlaps with the timing at which the injection amount reaches a progress rate of 70% of the planned amount.

As shown in FIG. 9, in the case 4, in the second step and the third step, the stress increases, but the change in the stress is less than 1.5 N / mm ² and the variation in the displacement is also less than 1 mm. .

As shown in FIG. 10, in the case 5, as in the case 4, in the second step and the third step, the stress increases but the change in stress is less than 1.5 N / mm ² , and the displacement The fluctuation is also less than 1 mm.

  That is, in the case 4 and the case 5, it can be seen that the pore water pressure in the ground is efficiently dissipated, split injection does not occur, and osmotic injection is ensured.

  In addition, FIG. 11 shows a cross-sectional view of the uniting material in each of the cases 1 to 5 described above. FIG. 11A is a cross-sectional view of the uniting material in case 1, and FIG. 11B is a cross-sectional view of the uniting material in case 2. FIG. 11C is a cross-sectional view of the uniting material in case 3, and FIG. 11D is a cross-sectional view of the uniting material in case 4. Finally, FIG. 11 (e) is a cross-sectional view of the uniting material in case 5.

  As shown in FIG. 11A, in case 1, the united body 40 is formed at the top. As shown in FIG. 11B, in the case 2, as in the case 1, the uniting material 41 is formed in the upper part. In these cases 1 and 2, the injected material escapes at the boundary between the cinnabar 32 and the mortar 35, and it can be seen that the injection pressure acts directly on the lower surface of the mortar 35.

  As shown in FIG. 11C, in the case 3, the solidified body 42 is generally formed around the injection port 36, but is located slightly above and in contact with the lower surface of the mortar 35.

  As shown in FIG. 11 (d), in case 4, the solidified body 43 is formed around the injection port 36, and it can be confirmed that good penetration injection can be secured. In addition, as shown in FIG. 11 (e), in the case 5, as in the case 4, the solidified body 44 is formed around the injection port 36, and it can be confirmed that satisfactory infiltration can be secured.

[Test 2]
In test 2, the same model ground 29 as in test 1 was used, and the test was performed while changing the injection conditions in the inching injection process. In Test 2, as shown in FIG. 12, when the primary management value and the secondary management value are reached, the number of revolutions of the injection pump is limited and the injection speed is changed. Here, the primary management value is 1 N / mm ² and the secondary management value is 2 N / mm ² . Also, the maximum injection rate is limited to 80% by reaching the primary control value, and limited to 50% by reaching the secondary control value.

[Case 6]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.15 L / sec (9.0 L / min)
Time rate of change of injection rate: 5.56 × 10 ⁻³ L / sec ²
Peak retention time coefficient α: 1
Interrupt time factor β: 1
Peak retention time: 9 seconds Interruption time: 9 seconds [Case 7]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.15 L / sec (9.0 L / min)
Time rate of change of injection rate: 5.56 × 10 ⁻³ L / sec ²
Peak retention time coefficient α: 0
Interruption time factor β: 6
Peak retention time: 0 seconds Interruption time: 54 seconds [Case 8]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.15 L / sec (9.0 L / min)
Time rate of change in injection rate: 11.12 × 10 ⁻³ L / sec ²
Peak retention time coefficient α: 1
Interrupt time factor β: 1
Peak retention time: 4.5 seconds Interruption time: 4.5 seconds [Case 9]
Injection method: intermittent injection (inching injection)
Maximum injection rate: 0.15 L / sec (9.0 L / min)
Time rate of change of injection rate: 5.56 × 10 ⁻³ L / sec ²
Peak retention time coefficient α: 2
Interruption time factor β: 0.5
Peak retention time: 18 seconds Break time: 4.5 seconds

As shown in FIG. 13, in the case 6 and the case 7, the stress value reaches 1 N / mm ² and the maximum injection rate is reduced to 80% of the initial value. However, the maximum stress and the maximum displacement were each low, and the injection progress rate of 100% was achieved without the stress value reaching ² N / mm ² . From this, it was proved that the injection method by intermittent injection can improve the predetermined range by 100% while reducing the influence on the adjacent structure in the ground injection method in which a plurality of improved bodies are three-dimensionally formed. In cases 8 and 9, the stress value reaches ² N / mm ² and the maximum injection rate is reduced to 50% of the initial value. In these cases 8 and 9, it was confirmed that both the maximum stress and the maximum displacement were very high values as compared with case 6 and case 7.

According to the results of Test 1 and Test 2, the absolute value of the time rate of change of the injection rate is 5.56 × 10 ⁻³ L / sec ² or less, the peak retention time coefficient α is 0 to 1, and the interruption time coefficient β is 1 to 6. It has been found that intermittent infusion is more effective. The effect of intermittent injection is also effective when the interruption time factor β exceeds 6, but no further improvement in the effect can be expected compared to the case where the interruption time factor β is 1 to 6. Construction efficiency decreases and economic efficiency deteriorates.

DESCRIPTION OF SYMBOLS 10 ... Boring rod, 11 ... Rotary type drilling machine, 13 ... Improvement body, 20 ... Construction system, 21 ... Dynamics management apparatus, 22 ... Injection management apparatus, 23 ... PC for recording, 24 ... Measuring instrument, 25 ... Injection pump 26 ... Flow rate / pressure measuring device, 29 ... Model ground

Claims (5)

By injecting an injection material into the target area of the ground, a ground injection method for three-dimensionally creating a plurality of improved bodies in the ground,
An injection step of injecting the injection material into the ground;
An interruption step of interrupting injection of the injection material after the injection step is performed;
Repeatedly
The injection step is performed by changing the injection speed of the injection material in a trapezoidal waveform or a triangular waveform ,
The injection step includes the absolute value of the time change rate of the injection rate of the injection material until the injection rate of the injection material reaches the maximum rate, and the injection rate from the state where the injection rate of the injection material becomes the maximum rate. The absolute value of the time change rate of the injection rate of the injection material before stopping the injection of the material is 5.56 × 10 ⁻³ L / sec ² or less, respectively, and the injection rate of the injection material is the maximum rate. The absolute value of the time change rate of the injection pressure of the injection material until it reaches and the injection pressure of the injection material until the injection of the injection material is stopped from the state where the injection speed of the injection material reaches the maximum speed. A ground pouring method characterized in that the absolute value of the time change rate is set to 0.5 MPa / second or less . In the ground injection method according to claim 1,
The injection step includes
When changing the injection rate of the injection material with the trapezoidal waveform, when the injection rate of the injection material is q _p , the rate of change of the injection rate with time is a _q , and the coefficient is α (α = 0 to 1), Holding time Tp when the injection speed of the injection material becomes the maximum speed,
Tp = (q _p / 3a _q ) × α
The ground injection method characterized by setting to . In the ground injection method according to claim 1 or 2,
The interruption step includes
When the injection rate of the injection material is q _p , the time change rate of the injection rate is a _q , and the coefficient is β (β = 1 to 6), the time Ti for interrupting the injection of the injection material,
Ti = (q _p / 3a _q ) × β
The ground injection method characterized by setting to . In the ground injection method according to any one of claims 1 to 3,
Based on the displacement of the structure adjacent to the target area of the ground, the displacement of the ground, the maximum injection speed of the injection material, and the injection pressure of the injection material, the injection speed of the injection material is gradually increased and decreased. A ground injection method characterized by that. In the ground injection method according to claim 4 ,
The maximum speed in the injection speed of the injection material is regulated based on the displacement of the structure adjacent to the target area of the ground after the injection of the injection material, the displacement of the ground. Method.