JP2007039951A - Method of determining strength and layer thickness of improved layer of back filling sand by chemical injection and experiment device used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of determining the strength and the layer thickness of an improved layer of a back filling sand by chemical injection which can prevent the back filling sand from being sucked by forming the improved layer suitable for a construction site. <P>SOLUTION: The back filling sand 5 to be improved is collected from the construction site, the concentration of the chemical to be injected is changed, and an improved layer sample S is manufactured under a predetermined restraint pressure. Data on a relation between the concentration of the chemical and a strength q is acquired by using the improved layer sample S. A variable hydraulic pressure P is given to the improved layer sample S until it is ruptured under predetermined conditions while changing the layer thickness h for each chemical concentration to acquire data on the relation between the layer thickness h and the number of times N or a time t at which the improved layer sample is ruptured. Based on data on both relations acquired, the strength q and the layer thickness H (=h) fulfilling the requirement requested at the construction site are selected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for determining the strength and thickness of an improved layer of backfill sand by chemical solution injection and an experimental apparatus used therefor, and more particularly, to form an improved layer suitable for a construction site to prevent backfill sand from being sucked out. The present invention relates to a method for determining the strength and thickness of an improved layer of backfill sand by injecting a chemical solution, and an experimental apparatus used therefor.

  As a construction method for preventing the back sand from sucking off the offshore structure such as caisson, there is a method for preventing the suction by injecting a chemical solution to improve (harden) the back sand. Concerning this chemical injection method, the concentration of the backside sand improved by the chemical solution, the strength at which suction does not occur, and the obtained strength can be obtained by experiments using this sample. A method of injecting a chemical solution has been proposed (see Patent Document 1).

  In this proposal, by changing the concentration of the chemical solution to be injected, only the strength of the back sand is changed, and the optimum strength at which no sucking occurs is detected. That is, the strength under a predetermined layer thickness is detected given the layer thickness of the back sand to be improved. In addition, only the result of the presence or absence of suction is verified by an experiment in which fluctuating water pressure is applied to the sample over a fixed time of 24 hours.

Therefore, in this proposal, there is a problem that only the improved back sand that prevents sucking out can be formed in a predetermined period in the improved back sand layer having a predetermined layer thickness. Therefore, it cannot be applied to the case where the layer thickness or the period during which the suction can be prevented is changed, and it lacks applicability, and an improved layer optimal for the construction site cannot be formed.
JP 2002-322639 A

  The object of the present invention is to determine the strength and thickness of the improved layer of backfill sand by injecting a chemical solution that can prevent the backfill sand from being sucked out by forming an improved layer suitable for the construction site, and an experimental apparatus used therefor Is to provide.

  In order to achieve the above object, the method for determining the strength and layer thickness of the improved back sand by injecting the chemical solution according to the present invention is to improve the back sand by injecting the chemical solution to prevent the back sand from sucking out of the structure such as caisson. A method for determining the strength and thickness of a layer, which comprises collecting a back sand to be improved from a construction site and changing the concentration of the chemical to be injected, and producing an improved layer sample under a predetermined restraining pressure, and the chemical The process of acquiring the relation data between the chemical concentration and strength using the improved layer sample with the changed concentration, and changing the layer thickness for each chemical concentration to give the variable water pressure until it breaks under predetermined conditions The process of acquiring the relationship data between the layer thickness and the number of times or time until failure, and the strength and thickness of the improved layer that satisfies the conditions required at the construction site are selected based on the acquired both relationship data Having a process The one in which the features.

  Further, the experimental device of the present invention is an experimental device used for determining the strength and thickness of the improved layer of back sand by injecting a chemical solution that prevents sucking out the back sand of a structure such as a caisson. And a flow rate measuring device connected to the fluctuating water pressure device via a water flow pipe, the fluctuating water pressure device being a sealed container for containing the improved layer sample and water produced by injecting a chemical into the back sand. A fluctuating pressure unit that loads a fluctuating pressure into the sealed container from above, and a fluctuating pressure measuring device that measures the fluctuating pressure, wherein the water circulation pipe is connected to the lower side of the sealed container, Water that permeates through the improvement layer sample due to fluctuating water pressure caused by pressure flows into and out of the flow measuring device, and has a line pressure measuring device that measures the water pressure, and the flow measuring device flows out of the water flow pipe. Measure the flow rate As well as, is characterized in that it has a pressurizable pressure unit said sealed vessel at a predetermined pressure through the water distribution pipe.

In the present invention, the backfill sand means soil to be backfilled, and includes backfill soil.

  According to the method for determining the strength and thickness of the improved back sand layer by injecting the chemical solution of the present invention, the concentration of the chemical solution to be collected and injected from the construction site is changed under a predetermined restraint pressure. By the process of manufacturing the improvement layer sample, the sample can be manufactured under the same conditions as the construction site where the improvement layer is actually formed, and the reality can be reproduced more accurately to obtain accurate data.

  Further, in the step of obtaining the relationship data between the chemical solution concentration and the strength using the improved layer sample with the changed chemical solution concentration, the correlation between the chemical solution concentration and the strength of the improved layer can be grasped. In the process of obtaining the data of the relationship between the layer thickness and the number of times or the time until failure by applying variable water pressure until the improved layer sample is broken for each chemical concentration and changing the layer thickness under the specified conditions, Thus, the correlation between the thickness and strength of the improved layer for each chemical solution concentration can be grasped by an experiment that approximates the conditions acting on the improved layer.

  Based on the acquired relationship data, an optimal combination is selected from the combinations of the strength and thickness of the improved layer that satisfies the conditions by the process of selecting the strength and thickness of the improved layer that satisfies the requirements at the construction site. Can be selected.

  Injecting a chemical solution with the strength of the improved layer selected and determined by the above process to form the improved layer with the determined layer thickness will satisfy the requirements of the construction site and prevent the back sand from being sucked out. It becomes possible.

  According to the experimental apparatus of the present invention, it is provided with a fluctuating water pressure device and a flow rate measuring device connected to the fluctuating water pressure device and a water flow pipe, and the fluctuating water pressure device is manufactured by injecting a chemical into the back sand. A sealed container for containing the improved layer sample and water, a fluctuating pressure unit for loading a fluctuating pressure from above into the sealed container, and a fluctuating pressure measuring device for measuring the fluctuating pressure, and the water distribution pipe is a sealed container The flow rate measuring device has a pipe pressure measuring device for measuring the water pressure while flowing water into and out of the flow rate measuring device by the fluctuating water pressure generated by the fluctuating pressure. The flow rate flowing in and out of the flow pipe is measured, and the pressurization unit capable of pressurizing the inside of the sealed container to a predetermined pressure via the water flow pipe has a layer thickness for each chemical solution concentration. Change the prescribed article Can be used in the step of giving the variation pressure to failure under, obtains the relationship data between the number or time to failure and the layer thickness.

  That is, it is possible to carry out a fluctuating water pressure experiment that approximates the conditions that actually act on the improvement layer at the construction site, and based on the measurement data from the fluctuating pressure measuring device, the pipe pressure measuring device, and the flow rate measuring device, It is possible to grasp the correlation between the layer thickness and strength of the improved layer.

  Hereinafter, a method for determining the strength and thickness of an improved layer of backfill sand by chemical injection according to the present invention and an experimental apparatus used therefor will be described based on the embodiments shown in the drawings.

  FIG. 9 is a cross-sectional view illustrating an example of a construction site where a chemical solution is injected into the back sand 5. In this construction site, a caisson 1 is installed on a basic rubble 2, and a backstone 3 is laid on the back of the caisson 1. The back sand 5 is refilled on the sandproof sheet 4 covering the back stone 3, and the upper surface is a paved surface 7.

  Here, when the sandproof sheet 4 is broken, a so-called sucking phenomenon occurs in which the back sand 5 is sucked out to the sea side by the wave motion of the seawater W in front of the caisson 1. Accordingly, the improved layer 6 is formed by injecting a chemical into the back sand 5 and curing it to prevent sucking. For this purpose, it is necessary to form the improved layer 6 having the optimum strength and thickness H that satisfies the requirements of the construction site. As the chemical solution, for example, permanent grout made of special silica such as activated silica or ultrafine silica, water glass-based silica sol durable grout, or the like is used.

  Therefore, the strength and the layer thickness H of the improved layer 6 are determined by the procedure shown in FIG. First, the improvement layer sample S is manufactured under a predetermined restraint pressure by changing the concentration of the chemical solution to be collected by collecting the back sand 5 to be improved from the construction site in several ways (first step). The predetermined restraining pressure is a pressure that assumes a pressure received at a position where the improvement layer 6 is formed, and is, for example, a pressure at a representative depth point D at a position where the improvement layer 6 is formed.

  After the back sand 5 is packed in a pressure-resistant container such as a mold, the chemical solution of each concentration is infiltrated, and the improved layer sample S is manufactured by curing for 28 days, for example, under this restraining pressure. Since this improved layer sample S is manufactured under pressure conditions that are close to the restraint pressure at the construction site where the improved layer 6 is actually formed, when this improved layer sample S is used in an experiment, the reality is reproduced more accurately. Good data can be acquired.

  In order to manufacture the improved layer sample S, for example, a method for manufacturing a specimen described in Japanese Patent No. 3502079 can be used. Since the improved layer sample S is used for the strength test and the fluctuating hydraulic pressure test, several or more improved layer samples S are manufactured for each chemical concentration.

  Next, using the improved layer sample S in which the chemical concentration is changed, relational data between the chemical concentration and the strength is acquired (second step). Specifically, when the uniaxial compressive strength test of the improved layer sample S is performed and the relationship between the strength q and the chemical concentration is plotted, the proportional relationship data between the strength q and the chemical concentration is obtained as illustrated in FIG. can do. This makes it possible to grasp and estimate the strength q of the improved layer 6 formed at the construction site, based on the concentration of the injected chemical solution.

  Next, a variable water pressure experiment is performed in which a variable water pressure P is applied until the modified layer sample S is broken under predetermined conditions by changing the layer thickness h for each chemical solution concentration, and the number N or time until the layer thickness h is broken. Data related to t is acquired (third step).

  This fluctuating water pressure experiment is conceptually shown in FIG. 3, and the improvement layer sample S is accommodated in a sealed container 8 having a fluctuating pressure unit connected to the upper part and a water flow pipe 12 connected to the lower part. To do. Glass beads G are laid at the bottom of the sealed container 8 in order to ensure water flowability.

  The improvement layer sample S is loaded with a predetermined pressure by the water W in the upper conduit 11 and the water W in the lower water circulation pipe 12. This predetermined pressure is a pressure corresponding to the pressure received at the position where the improvement layer 6 is formed, and is, for example, the pressure at the representative depth point D described above.

  In this state, a fluctuating pressure P for moving the water W in the upper conduit 11 up and down is applied. The fluctuating pressure P is obtained in advance as wave data of waves generated at the construction site, and based on this data, for example, is set to the same pressure amplitude and frequency as the most frequent waves as shown in FIG. The fluctuating pressure P is a value that changes due to the vertical movement caused by the most frequent wave to the pressure at the representative depth point D.

  Due to this fluctuating pressure P, the water W in the conduit 11 permeates the improved layer sample S and flows in and out of the water circulation pipe 12, and the improved layer sample S is gradually destroyed by repeated permeation of the water W, and the repetition until the destruction is repeated. The number of times N or time t is measured.

  That is, it is possible to reproduce the state approximate to the construction site where suction of the back sand 5 is generated, and to acquire accurate data on the durability of the improved layer sample S.

  As shown in FIG. 2, the fluctuation water pressure experimental device includes a fluctuation water pressure device 8, a flow rate measurement device 13, and a water flow pipe 12 that connects both devices 8 and 13. The fluctuating water pressure device 8 includes a sealed container 9 in which glass beads G are laid at the bottom, and a fluctuating pressure unit. The fluctuating pressure unit includes a conduit 11, an electropneumatic converter 20a, and a compressed air generating device 17. It is controlled by the control device 18. For example, a sealed container 9 having an outer diameter of about 100 mm and a height of about 100 mm is used. The compressed air generator 17 includes a compressor, a regulator, and the like.

  The flow rate measurement device 13 includes a micro load meter 15 installed in the sealed container 14 and connected to the measurement unit 19, a water storage tank 16 suspended from the pressure meter, and a pressure unit. The unit includes a sealed container 14, an electropneumatic converter 20 b, a pressure gauge 21 b, and a compressed air generator 17, and is controlled by a controller 18.

  One end of the water distribution pipe 12 is connected to the bottom of the sealed container 9 of the variable water pressure device 8, and the other end is disposed in the water storage tank 16 of the flow rate measurement device 13, so that the measurement unit 19 constituting the pipe water pressure measurement device is provided. It has a connected pressure gauge 21c.

  The fluctuating water pressure experiment is carried out by containing the improvement layer sample S in the airtight container 9 of the fluctuating water pressure device 8 with the wire mesh 10 sandwiched between the water W and the air A. By adjusting the inside of the sealed container 14 to a predetermined pressure with the compressed air generator 17 and the electropneumatic converter 20 a of the flow rate measuring device 13, the inside of the sealed container 9 is maintained at a predetermined pressure via the water circulation pipe 12. This predetermined pressure is an equivalent pressure received at the position where the improvement layer 6 is formed as described above, and this predetermined pressure is measured by the pressure gauge 21 b connected to the measurement unit 19.

  Then, by causing the compressed air generator 17 and the electropneumatic converter 20a to flow the air A into and out of the sealed container 9 through the conduit 11, the fluctuation in accordance with the waves generated at the construction site as described above in the water W is achieved. Water pressure P1 is applied. This fluctuating water pressure P1 is measured by the pressure gauge 21a. The method of providing the fluctuating water pressure P1 is not limited to this, and other methods may be used.

  Due to the fluctuating water pressure P1, the water W in the sealed container 9 permeates the improved layer sample S and flows into and out of the water storage tank 16 of the flow rate measuring device 13 through the water flow pipe 12, and the flow rate of the water W is a minute load. The water pressure P2 in the water distribution pipe 12 is measured by the pressure gauge 21c. The wire mesh 10 installed above and below the improvement layer sample S is for protection when the improvement layer sample S is fragile, and the installation can be omitted.

  When the flow rate measured by the flow rate measuring device 13 is shown with time, the outflow flow rate Q rapidly increases while vertically moving due to pressure fluctuation as shown in FIG. As the outflow flow rate Q on the vertical axis in FIG. 6 becomes negative (downward), it means that the water W flows from the storage tank 16 of the flow measurement device 13 into the sealed container 9 through the water flow pipe 12. Yes. That is, it shows that the improvement layer sample S is broken and the outflow flow rate Q is increased. Thus, based on the flow rate data, for example, it is determined that the improvement layer sample S has been destroyed at the point B1 at which the outflow rate Q has increased rapidly.

  Further, when the data of the fluctuation water pressure P1 measured by the pressure gauge 21a and the water pressure P2 on the lower surface of the improved layer sample S of the water flow pipe 12 measured by the pressure gauge 21c are shown with time, the vertical displacement due to the pressure fluctuation as shown in FIG. The water pressure P2 starts to increase while the water pressures P1 and P2 coincide with each other. This has shown that the improvement layer sample S destroyed and the pressure became uniform. In FIG. 7, in order to clarify the data (solid line) of the water pressure P2, the data (dotted line) of the water pressure P1 is omitted in the middle.

  Since it has been confirmed that the point B2 at which the water pressure P2 on the lower surface of the improvement layer sample S increases coincides with the point B1 at which the flow rate Q increases rapidly, for example, if the point B1 at which the outflow flow rate Q increases rapidly is not clear, the improvement is made. It can also be determined that the improved layer sample S has broken at the point B2 when the water pressure P2 on the lower surface of the layer sample S has increased rapidly. 6 and 7, the horizontal axis represents time t, but the number of times the fluctuating water pressure P1 is applied (the number of repetitions N) may be used.

  The order of performing the second step and the third step may be either, and it is preferable to perform the steps at the same time to shorten the experiment time.

  And based on the relationship data between the chemical solution concentration and strength acquired previously, and the relationship data between the layer thickness h and the number of times of destruction N or the failure time t, the strength and layer of the improved layer 6 satisfying the conditions required at the construction site. A thickness h is selected (fourth step). Specifically, when the relationship between the layer thickness h and the number of repetitions N until the destruction is plotted for each strength q (that is, the concentration of the chemical solution), the relationship data of the quadratic curve as illustrated in FIG. Can be acquired.

Multiplying the number N of repetitions until destruction by the frequency (fluctuation frequency of fluctuating water pressure) gives the time t until destruction. Therefore, if data is plotted as time t until destruction in FIG. For example, when the data is subjected to regression analysis, the following equations (1) and (2) can be obtained.
h = A + BlogN + C (logN) ² (1)
h = A + Blogt + C (logt) ² (2)
Where h: layer thickness of improved layer sample A, B, C: coefficient N: number of repetitions until failure t: repetition time until failure

  As a result, the correlation between the layer thickness h for each strength q (that is, the chemical concentration) and durability (the number of repetitions N and the time t until destruction) can be grasped, and the durability is determined by the strength q and the layer thickness h. Can be estimated. From this plot data, an optimum combination of the layer thickness H (= h) and the strength q that satisfies the requirements of the construction site is selected. For example, when there is a requirement for the durable years, a combination of the layer thickness H and the strength q that clears the repetition number N corresponding to the durable years is selected. When there are a plurality of combinations that satisfy the conditions, the combination that achieves the lowest cost by calculating the cost or the layer thickness H is selected when there is a restriction on the layer thickness H.

  After determining the combination of the layer thickness H and the strength q of the improved layer 6 by the above steps, the improved layer 6 having the determined layer thickness H is formed by injecting a chemical solution having the determined strength q. Thereby, the optimal improvement layer 6 which satisfy | filled the requirements of a construction site is formed, and it becomes possible to prevent the back sand 5 from being sucked out.

It is a flowchart which illustrates the determination method of the intensity | strength and layer thickness of the improvement layer of backfill sand by chemical | medical solution injection | pouring of this invention. It is explanatory drawing which illustrates the whole outline | summary of the fluctuation | variation water pressure experiment apparatus of this invention. It is explanatory drawing which shows notionally the method of giving a fluctuation | variation water pressure to an improvement layer sample. It is a graph which illustrates the fluctuating water pressure given to an improvement layer sample. It is a graph which shows the relationship between a chemical | medical solution concentration and uniaxial compressive strength. It is a graph which shows the time-dependent fluctuation | variation of the flow volume of the water which permeate | transmits an improvement layer sample with a fluctuation | variation water pressure. It is a graph which shows the time-dependent fluctuation | variation of the water pressure of the water which flows in and out of a water circulation pipe with a fluctuation | variation water pressure. It is a graph which shows the relationship between the layer thickness of an improvement layer sample, and durability. It is sectional drawing which shows an example of the construction site which inject | pours a chemical | medical solution into backfill sand.

Explanation of symbols

1 Caisson
2 Foundation rubble 3 Back lining stone 4 Sand protection sheet 5 Back lining sand 6 Improved layer of back lining sand 7 Pavement surface 8 Fluctuating hydraulic device
DESCRIPTION OF SYMBOLS 9 Sealed container 10 Wire net 11 Conduit 12 Water distribution pipe 13 Flow rate measuring device 14 Sealed container 15 Micro load cell 16 Water storage tank 17 Compressed air generator
18 Control Device 19 Measuring Unit 20a-20b Electropneumatic Converter 21a-21c Pressure Gauge A Air G Glass Bead S Improved Layer Sample W Water

Claims (4)

  This is a method for determining the strength and thickness of the improved layer of backfill sand by injecting chemicals to prevent the backfill sand from sucking out caisson and other structures. A step of producing an improved layer sample under a predetermined restraining pressure by changing the concentration of the chemical solution; a step of obtaining relationship data between the chemical concentration and the strength using the improved layer sample having the changed chemical solution concentration; and the improved layer sample To change the layer thickness for each chemical solution concentration, apply a variable water pressure until it breaks under a predetermined condition, and obtain the relationship data between the layer thickness and the number of times or time until destruction, and the obtained both relationship data A method for determining the strength and thickness of the improved layer of backfill sand by injecting a chemical solution, the method comprising: selecting the strength and thickness of the improved layer that satisfies the conditions required at the construction site.   In the step of acquiring the relational data between the layer thickness and the number of times or time until destruction, the flow rate of water that permeates the improved layer sample is measured by the fluctuating water pressure, and the destruction is performed based on the measured flow rate data. The method for determining the strength and thickness of the improved layer of back sand by chemical injection according to claim 1, wherein the number of times or the time until the determination is determined.   In the step of obtaining the relationship data between the layer thickness and the number of times or time until failure, the pressure of water that permeates the improved layer sample by the fluctuating water pressure is measured, and based on the measured water pressure data, The method for determining the strength and thickness of the improved layer of backfill sand by chemical solution injection according to claim 1, wherein the number of times or time until the destruction is determined.   An experimental apparatus used to determine the strength and thickness of an improved layer of backfill sand by injecting a chemical solution that prevents suction of the backfill sand of a structure such as a caisson, the variable water pressure apparatus, and the variable water pressure apparatus and water flow A flow rate measuring device connected through a pipe, and the variable hydraulic pressure device includes an improved layer sample produced by injecting a chemical solution into the back sand and a sealed container containing water, and the sealed container from above. A variable pressure unit for loading a variable pressure; and a variable pressure measuring device for measuring the variable pressure, wherein the water circulation pipe is connected to the lower side of the closed vessel, and the improved layer sample is generated by the variable water pressure generated by the variable pressure. And a water pressure measuring device for measuring the water pressure, and the flow measuring device measures the flow rate of the water flowing in and out of the water flow pipe, and Water distribution Experimental device having a pressurizable pressure unit to a predetermined pressure the closed vessel through the.

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