JP5602274B2 - Air mortar placing method - Google Patents

Description

  Air mortar is used for filling materials in tunnels and lightweight embankments in embankment work. The present invention relates to a construction method for placing air mortar.

  The “air mortar” in the present specification means a kneaded product before placing unless otherwise specified. Air bubbles are present in the air mortar, and after curing, a cured body having voids derived from the bubbles inside is formed. “Base mortar” is a kneaded mixture of raw material mortar for making air mortar. By mixing air bubbles into a foaming agent solution containing surfactant, base mortar is mixed. Air mortar is obtained.

  Typical applications for air mortar include filling materials for filling the gap between the pipe and tunnel when pipes such as gas pipes are buried in tunnels constructed by the shield method, propulsion method, and mountain method. . Conventionally, in such an application, it is common to install a plant at a tunnel wellhead to produce an air mortar, which is pumped and driven into the tunnel. However, when air mortar is pumped, the internal bubbles are easily crushed or material separation occurs. Therefore, in the air mortar that pumps a distance exceeding 100 m, the air content (sometimes referred to as the foaming rate or the bubble rate). ) Is usually raised to about 60% by volume. From the necessity of ensuring excellent air permeability in a filling material for a gas buried pipe, it is desired to apply an air mortar having a higher air content (for example, 65% by volume or more).

  Recently, foaming agents capable of obtaining highly stable bubbles have been developed, and it has become possible to pump air mortar having a high air content of about 70% by volume. However, since air mortar is inherently high in viscosity and is a compressible material, it is very difficult to perform long-distance pumping exceeding 1 km for air mortar having a high air content.

JP-A-9-235151 JP 2004-131932 A JP 2004-353276 A

  The present invention provides a technique capable of continuously and stably placing even an air mortar having a high air content at a distant placement site exceeding 1 km, for example, from a mortar kneaded production plant. In addition, an object of the present invention is to provide a technique that facilitates keeping the quality of the air mortar constant during the placement.

  In order to achieve the above object, the present inventors adopt a construction method in which the base mortar is pumped for a long distance to the vicinity of the placement site, and then mixed with bubbles to continuously form air mortar, which is then placed. Various attempts were made. However, it has been found that it is not easy to continuously mix the bubbles uniformly over the line extension while continuing the long-distance pumping of the base mortar. As a major factor, pressure loss (pressure loss) generated during mixing was considered.

As a result of detailed examination, it was found that this problem can be greatly reduced by the following method. That is, in the present invention,
When the base mortar pumped in the pipeline and the bubbles are mixed by a “mixer” to continuously generate air mortar, and this is supplied to the placement site by the pipeline,
At least the flow rate Q ₀ and the gauge pressure P ₀ of the air mortar flowing in the pipe line are measured, and the air content (volume%) of the air mortar supplied to the placement site is estimated using these measured values. An air mortar placing method for performing an operation of adjusting a ratio between a base mortar flow rate Qb introduced into the mixer and a bubble flow rate so that the estimated value of the air content rate is out of a set target range. Is provided.
As the mixer, in the flow of the base mortar that is being pumped, a “merging mechanism” that discharges bubbles to join the base mortar so as to add a flow force in the flow direction, and the joined fluid Those having a “stirring mechanism” for stirring and mixing can be used. As the merging mechanism, for example, a mechanism that discharges air bubbles from an inner pipe having a double pipe structure can be used, and the pressure loss in the mixer can be made zero or negative.

  As the merging mechanism of the mixer, one that adds flow force by discharging bubbles in the flow direction from the open end of a pipe arranged so that the base mortar flows around the inside of the pipe line through which the base mortar flows is suitable. It becomes a target. The stirring mechanism of the mixer has an obstacle member for shearing the fluid, and the fluid is stirred and mixed by the obstacle member using the fluid force of the fluid to which the fluid force is added by the merging mechanism. Applicable types are applicable.

In particular, as an effective technique for accurately controlling the air content of air mortar, in the above-mentioned air mortar placing method, a “foamer” that generates bubbles by mixing a foaming agent solution and air is used as the mixer. And at least three items of air mortar flow rate Q ₀ and gauge pressure P ₀ flowing in the pipe line, base mortar flow rate Qb introduced into the mixer, and further a foaming agent introduced into the foamer 4 items including the flow rate Qk of the solution are monitored, and using these measured values, the air content (volume%) of the air mortar supplied to the placement site is estimated, and the estimated value of the air content is There is provided a technique of performing automatic control in real time to adjust at least the flow rate Qa of air fed into the foamer so as to approach the target value.

According to the present invention, it is possible to continuously manufacture air mortar near the placement site using the base mortar that has been pumped over a long distance, and the following advantages are obtained.
(1) Since long-distance pumping is performed in the state of base mortar, it is possible to place at a position very far from a mortar plant, which is difficult in the past, such as several km or 10 km or more.
(2) Since the pumping distance as an air mortar can be shortened, material deterioration of the air mortar is greatly reduced. For this reason, even air mortar with an air content as high as 65% or more can be applied to the construction site of a long tunnel.
(3) It is possible to control the fluctuation of the air content of the air mortar so that the quality can be improved even when the pulsation at the beginning of the base mortar pumping or the pressure loss fluctuation during the pumping due to the temperature occurs. Stable air mortar can be placed.
(4) When the mixer specified in the present invention is used, the mixing property is improved and the quality is improved in terms of the homogeneity of the bubbles.

The figure which illustrated the typical line structure in the case of applying the construction method of this invention. The figure which illustrated typically the internal structure of the mixer which can be applied to this invention. The figure which illustrated typically the internal structure of the mixer which employ | adopted the general method for the confluence | merging mechanism.

FIG. 1 illustrates a typical line configuration when the method of the present invention is applied. The line can be roughly divided into four sections A to D.
Section A is a part where a base mortar is made and delivered at a position away from the placement site. In the base mortar plant 11, raw materials such as cement, aggregate, and water are prepared to make a kneaded base mortar, which is fed into the base mortar line 13 by the pump 12. When the placement site is in a tunnel, section A is usually provided near the tunnel wellhead.

  Section B plays the role of a pipeline that pumps the base mortar delivered from A in the section close to the placement site. The pipeline is mainly composed of the base mortar pipe line 13, but when the pipeline extension is long, for example, several hundred meters or more, an agitator 14 that stirs the base mortar in the middle and a relay pump 15 that gives a pumping force again are 1 Two or more sets are provided. If a base mortar having a composition that is particularly excellent in long-distance pumpability is used, the pipeline length of section B can be extended to several km or more or 10 km or more.

  Section C is a place where air mortar is continuously generated by mixing the base mortar that has been pumped and air bubbles in the vicinity of the placement site. A foamer 24 and a mixer 17 are provided. The foaming device 24 generates air bubbles by blowing air into the foaming agent solution. The foaming agent solution is obtained by diluting a foaming agent (a surfactant-based stock solution) with water, and is sent from the foaming agent solution tank 21 to the foaming device 24 by the addition pump 22. The compressed air produced by the air compressor 25 is appropriately depressurized by the air flow rate adjusting valve 28 and then sent to the foamer 24. Bubbles created by the foamer 24 are continuously introduced into the mixer 17 through the bubble line 29. On the other hand, the pumped base mortar is also continuously introduced into the mixer 17, and the base mortar and bubbles are mixed. The air mortar thus obtained is continuously pumped into the air mortar line 20.

  Section D is a placement location. Since the mixer 17 is installed near the placement location 50, the line length of the air mortar pipe line 20 can be reduced to approximately 100 m or less. For this reason, bubbles are not easily crushed during pumping, and high-quality air mortar is continuously supplied to the placement site.

  The placement method of the present invention is particularly characterized by “mixing” in Section C. Specifically, it is characterized by the configuration of the mixer and further by the control of the bubble content. These will be described below.

[Mixer]
The mixer 17 applied in the present invention has a “merging mechanism” that joins the base mortar and bubbles in the previous stage, and a “stirring mechanism” that stirs and mixes the fluid that has joined the latter stage.

  The merging mechanism has a structure in which bubbles are discharged so as to add a flow force in the flow direction to the flow of the base mortar being pumped. Due to the added fluid force (propulsive force), a new pressure loss due to the mixing of bubbles, that is, a pressure loss due to the difference in flow resistance between the air mortar and the base mortar, and inevitably occurs in the subsequent stirring mechanism. A significant portion of the pressure loss is offset.

  As a structure of such a merging mechanism, a structure in which bubbles are discharged from an open end of a pipe disposed so that the base mortar flows inside the pipe line through which the base mortar flows is suitable. In other words, it is not from the discharge port provided on the wall surface of the tube through which the base mortar flows, but the opening end of another tube inside the tube through which the base mortar flows is used as the discharge port, and the bubbles are in a direction substantially matching the flow of the base mortar It is desirable to blow in. By doing so, the pressure applied by blowing bubbles is efficiently transmitted to the base mortar, which greatly contributes to an increase in the fluid force as a combined fluid (base mortar not yet sufficiently mixed + bubbles). More specifically, a double tube structure can be used.

  Next, as the structure of the stirring mechanism, there is an obstacle member that shears the joined fluid in the pipe line, and the fluid is stirred and mixed by the obstacle member using the “flow force” of the joined fluid. Such a structure can be suitably employed. The obstruction member is, for example, a fin-shaped baffle plate, and a plurality of the obstruction members are installed in the flow path direction of the pipeline so that the fluid is stirred and mixed while flowing. The obstacle member itself may be rotated, but in that case, the mechanism becomes complicated. Therefore, the obstacle member is fixed, and the fluid is sheared by the obstacle member using the fluid force of the fluid (the propulsive force of the pumped base mortar + the propulsive force of the bubbles blown by the confluence mechanism). It is desirable to make the base mortar and bubbles uniform. Since the fluid force is applied by the upstream merging mechanism, it is easy to adopt a structure having a large fluid resistance, such as increasing the number of fins that are obstacle members. That is, air mortar with higher uniformity can be obtained by expanding the design freedom of the stirring mechanism.

  FIG. 2 schematically illustrates the internal structure of a mixer applicable to the present invention. The mixer 1 has a stirring mechanism 3 immediately after the merging mechanism 2. The merging mechanism 2 has a “double tube structure” in which an inner tube 4 connected from a bubble channel 29 is built in an outer tube 8 on an extension of the base mortar channel 13. A base mortar 101 introduced from a base mortar conduit 13 flows around the inner pipe 4. The inner tube 4 has an open end 5, and bubbles 102 are expelled from the open end 5 in the direction of the flow of the base mortar 101. Thereby, a fluid force is applied to the base mortar 101.

  The stirring mechanism 3 has a plurality of fin-like obstacle members 7 attached to a shaft rod 6. The shaft 6 is fixed to the tube body 9, and the obstacle member 7 itself does not move. This mixer is characterized in that a stirring mechanism is provided immediately after the merging mechanism 2. The fluid that has been joined by the joining mechanism 2 and has been given a fluid force is introduced into the stirring mechanism 3 while having a high fluid force. The fluid is agitated in the course of traveling through the tube body 9 while being sequentially sheared by a plurality of obstacle members using the fluid force, and the base mortar 101 and the bubbles 102 are mixed in a highly uniform state. In this way, the air mortar 103 is continuously made and pumped into the air mortar line 20.

FIG. 3 shows the inside of a mixer of the type having a conventional general merging mechanism used for continuously mixing base mortar and bubbles, and having a stirring mechanism similar to that shown in FIG. The structure is shown schematically. The inventors have conducted various air mortar production experiments using this type of mixer and the type of mixer shown in FIG. As a result, for example, the inner diameter of the tube body 9 of the mixer 1 is 2.5 inches, the inner diameter of the base mortar line 13 and the air mortar line 20 connected to the mixer 1 are both 2 inches, and the inner diameter of the bubble line 29 is 1 inch, base mortar is introduced from the base mortar line 13 at a flow rate of 150 L / min, and under the condition that air mortar having an air content of 65% by volume is continuously produced, When the pressure loss in the mixer 1 was examined, a pressure loss of about 3 kg / cm ² occurred in the type shown in FIG. 3 (comparative example). On the other hand, in the type shown in FIG. 2 (example of the present invention), the pressure loss was almost zero or negative.

  In this way, almost no pressure loss is caused by the combination of the “merging mechanism” that discharges bubbles so as to apply a flow force in the flow direction of the base mortar and the “stirring mechanism” that is arranged immediately after that. Air mortar can be continuously produced. Only when such a mixer is employed can high-quality air mortar be generated in the vicinity of the placement site by utilizing the fluidity of the base mortar that has been pumped over a long distance.

[Control of bubble content]
The air content of the air mortar supplied to the placement site can be controlled by adjusting the ratio between the base mortar flow rate Qb introduced into the mixer 17 and the bubble flow rate. As shown in FIG. 1, the base mortar flow rate Qb can be grasped by, for example, a flow meter 16 provided in the middle of the base mortar conduit 13. However, in order to change the base mortar flow rate Qb, it is necessary to change the outputs of the pump 12 and the relay pump 15. If such an operation is frequently performed, pulsation is likely to occur particularly in long-distance pumping. For this reason, the ratio of the base mortar flow rate Qb and the bubble flow rate is adjusted by changing the flow rate of the bubbles introduced from the bubble line 29 to the mixer 17 while maintaining the base mortar flow rate Qb in a steady state. It is easier to control. Specifically, the amount of air bubbles introduced can be changed by adjusting the amount of air sent to the foamer 24 by the air flow rate adjustment valve 28.

In order to control the air content of the air mortar within an appropriate range, it is extremely effective to measure the flow rate Q ₀ and the gauge pressure P ₀ of the air mortar flowing through the air mortar pipe line 20. These values are measured by the flow meter 18 and the pressure gauge 19 illustrated in FIG. Regarding the system actually used (configuration of sections A to D), the flow rate Q ₀ of the air mortar, the gauge pressure P ₀ , the output of the pump 12 or the relay pump 15, the valve opening degree of the air flow rate adjustment valve 28, the air By determining the correlation (map) of the air content in the mortar, the air content of the air mortar supplied to the placement site using the measured values of the flow rate Q ₀ and the gauge pressure P ₀ of the air mortar Can be estimated. Then, when the estimated value of the air content rate is out of the set target range, an operation of adjusting the ratio of the steady-state base mortar flow rate Qb and the bubble flow rate introduced into the mixer 17 so as to be within the target range is performed. Thus, the air content of the air mortar can be controlled. In this case, manual adjustment of the valve opening by the operator is possible, but automatic control for outputting an instruction value of the valve opening based on the map can also be adopted. Note that “estimating the air content in the air mortar” is not an essential requirement to calculate the air content value itself, but using the parameters corresponding to the air content to determine whether the air content is appropriate. Including judgment.

In order to control the air content of the air mortar more accurately, in addition to the air mortar flow rate Q ₀ and the gauge pressure P ₀ , the base mortar flow rate Qb actually introduced into the mixer 17 can be measured. preferable. As a result, the bubble flow rate can be adjusted in accordance with the base mortar flow rate Qb, and when the base mortar flow rate is not in a steady state, for example, when pulsation occurs at the beginning of the base mortar pumping start, Even when the pressure loss fluctuation occurs, the air content of the air mortar can be controlled.

The inventors have made various studies to perform more stable control. As a result, in addition to the three items of air mortar flow rate Q ₀ , gauge pressure P ₀ , and base mortar flow rate Qb, the foaming agent solution introduced into the foaming device 17. It has been found that it is very advantageous to measure the flow rate Qk. In other words, using the measured data of these four items, the air content in the air mortar can be directly calculated by the following equation (1), and it is not always necessary to obtain a specific correlation for each system. And extremely versatile control is possible.
Air content (Vol.%) = [{Q ₀ − (Qb + Qk)} × (1 + P ₀ )] / {Q ₀ (1 + P ₀ ) − (Qb + Qk) P ₀ } × 100 (1)
here,
Q ₀ : Flow rate of air mortar flowing through the air mortar pipe line 20 (L / min)
Qb: Base mortar flow rate (L / min) introduced into the mixer 17
Qk: Flow rate of foaming agent solution introduced into the foaming device 24 (L / min)
P ₀ : Gauge pressure (atm) of air mortar flowing through the air mortar pipe line 20

  From the above equation (1), it is possible to accurately estimate the air content in the air mortar supplied to the placement site. When the estimated value is lower than the target value, the opening degree of the air flow rate adjusting valve 28 for adjusting the flow rate of the air sent to the foamer 24 is increased. Conversely, when the estimated value is higher than the target value, the air flow rate adjustment is performed. By adding the operation of reducing the opening of the valve 28, the air content in the air mortar can be accurately controlled in real time.

Actually, it is desirable to automatically control the air flow rate adjusting valve 28 using a proportional valve. In that case, as illustrated in FIG. 1, a control panel 40 is provided in section C, and Q ₀ , Qb, Qk and P ₀ are continuously transmitted by a flow meter 18, a flow meter 16, a flow meter 23 and a pressure gauge 19, respectively. Or it measures regularly, those measured values are monitored with the control board 40, and the air content rate in an air mortar is estimated based on (1) Formula with the arithmetic unit incorporated in the control board 40. FIG. Then, the opening of the air flow rate adjustment valve 28 is adjusted in real time by automatic control so that the estimated value approaches the target value. Note that “estimating the air content in the air mortar” is not necessarily an essential requirement to calculate the value of the air content itself according to the equation (1) or the like, but using a parameter corresponding to the air content. It is also possible to perform arithmetic processing.

  In addition to adjusting the opening degree of the air flow rate adjusting valve 28, the operation of changing the flow rate Qk of the foaming agent solution sent to the foaming device 24 by adjusting the output of the addition pump 22 may be added to the automatic control. Good. In this case, for example, it is effective to monitor the air flow rate Qa by the flow meter 26 and the gauge pressure Pa by the pressure gauge 27 and reflect them in the opening degree adjustment of the air flow rate adjustment valve 28. Further, an operation of changing the base mortar flow rate Qb by connecting the control panel 40 to the pump 12, the agitator 14, and the relay pump 15 and adjusting the output thereof may be added to the automatic control. As a control method, feedback control such as PID can be used. It is also possible to appropriately combine the control for outputting the instruction value with reference to a map (matrix) obtained in advance.

[Base mortar]
As the base mortar, various known mortars excellent in long-distance pumpability can be used.
(Foaming agent)
Various foaming agents that are used in conventional air mortars can be applied. However, when producing an air mortar with a high air content of, for example, 65% by volume or more, the foam stability is excellent. It is desirable to use a type of foaming agent that includes a surfactant. For example, the foaming agent which mix | blends one or both of an amine oxide type surfactant and a fluorochemical surfactant is mentioned. Among these, a foaming agent containing an amine oxide type nonionic surfactant as a component is preferable. The foaming agent is diluted with water to form a foaming agent solution, and air is blown into this solution to form bubbles.

DESCRIPTION OF SYMBOLS 1 Mixer 2 Merge mechanism 3 Stirring mechanism 4 Inner pipe 5 Open end 6 Shaft bar 7 Obstacle member 8 Outer pipe 9 Tubing body 101 Base mortar 102 Bubble 103 Air mortar

Claims (5)

When the base mortar pumped in the pipeline and the bubbles are mixed by a “mixer” to continuously generate air mortar, and this is supplied to the placement site by the pipeline,
At least the flow rate Q ₀ and the gauge pressure P ₀ of the air mortar flowing in the pipe line are measured, and the air content (volume%) of the air mortar supplied to the placement site is estimated using these measured values. An air mortar placing method for performing an operation of adjusting a ratio between a base mortar flow rate Qb introduced into the mixer and a bubble flow rate so that the estimated value of the air content rate is out of a set target range. . A “foamer” that mixes the foaming agent solution and air to generate bubbles is disposed in the front stage of the mixer, and at least the flow rate Q ₀ and the gauge pressure P _{0 of the} air mortar flowing in the pipe line are added to the mixer. Three items of the flow rate Qb of the introduced base mortar are monitored, and using these measured values, the air content (volume%) of the air mortar supplied to the placement site is estimated, and the estimation of the air content is performed. The air mortar placing method according to claim 1, wherein automatic control for adjusting at least a flow rate Qa of air fed into the foamer is performed in real time so that the value approaches a target value. A “foamer” that mixes the foaming agent solution and air to generate bubbles is disposed in the front stage of the mixer, and at least the flow rate Q ₀ and the gauge pressure P _{0 of the} air mortar flowing in the pipe line are added to the mixer. Four items of the flow rate Qb of the base mortar to be introduced and the flow rate Qk of the foaming agent solution to be introduced into the foamer are monitored, and the air content of the air mortar supplied to the placement site using these measured values The air mortar according to claim 1, wherein automatic control is performed in real time to adjust at least the flow rate Qa of the air fed into the foamer so that the estimated value of the air content rate approaches a target value. Placing method.   As the mixer, in the flow of the base mortar that is being pumped, a “merging mechanism” that discharges bubbles to join the base mortar so as to add a flow force in the flow direction, and the joined fluid The air mortar placing method according to any one of claims 1 to 3, wherein the one having a "stirring mechanism" for stirring and mixing is used.   The stirring mechanism of the mixer has an obstacle member that shears the fluid, and stirs and mixes the fluid by the obstacle member using the flow force of the joined fluid. Air mortar placement method.

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