JP2009024493A - Earth-and-sand soil improving method, injection chemical, and construction management method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection chemical enabling injection of a large volume of chemicals in a wide area, an earth-and-sand soil improving method using the injection chemical, and a construction management method of simply confirming an improvement effect by measuring an electric specific resistance after chemical injection. <P>SOLUTION: According to the earth-and-sand soil improving method of injecting the injection chemical prepared by blending a principle material of a colloidal solution containing silica particles with a gelatinizer into an earth-and-sand soil, the injection chemical showing pH 1.5-2 is prepared by setting the silica particle concentration of the principle material, a gelatinizing time for bring about a sand gel state, and an electric specific resistance in the sand gel state. This injection chemical is injected into the earth-and-sand soil to improve the earth-and-sand soil into a soil having prescribed liquefaction strength. In improvement work, the electric specific resistance in a soil improvement area is measured to confirm an improvement effect in implementation of the construction management method in a simple manner. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an earth and sand improvement method, an infusion chemical solution, and a construction management method thereof, in particular, an earth and sand ground improvement method that enables a large amount of chemical solution to be injected over a wide range, a silica particle concentration, and a gelation that reaches a sand gel state. The present invention relates to an infusion chemical solution in which time and electrical specific resistance value are set, and a construction management method capable of simply confirming the improvement effect in the ground improvement area by injecting this infusion chemical solution and measuring the electrical specific resistance value after the chemical injection.

  The liquefaction countermeasure methods around and under structures on soft ground such as landfill sites include shear deformation control method, injection solidification method, pore water pressure dissipation method, groundwater level lowering method, etc. Among them, the injection solidification method is excellent in workability, and many construction results have been repeated due to the features such as wide application range. In addition, for improving the ground for sandy ground directly under existing structures, a chemical solution mainly composed of a colloidal solution in which ultrafine silica is dispersed has been used well. Therefore, the injection solidification method has been pointed out to be disadvantageous in that it is expensive and inferior in cost because it requires a large amount of cement, particularly expensive silica particles, which is the main material of the injected chemical solution.

This is because, in the conventional chemical injection method, uniaxial compressive strength was used for quality evaluation of ground improvement to confirm “liquefaction strength”. It is greatly influenced by the fact that it has been thought that the “liquefaction strength” can be increased by promoting the increase. That is, according to this idea, in order to obtain the required strength that requires a value of 1.9 to 9.8 N / cm ² or more, it is necessary to increase the concentration of the injected drug solution in order to increase the uniaxial compressive strength. This is because, as a result, a large amount of cement and expensive silica particles are used.

  Thus, proposals have been made to reduce the cost by reducing the amount of silica particles used. For example, in the method described in Japanese Patent Application No. 10-140973, the average diameter of the silica particles dispersed in the colloidal solution is 15 nanometers, and the concentration of the silica particles dispersed in the silica colloidal solution is 1.9 wt% to 6%. The amount of silica particles used was reduced from 10% by weight, which was the silica particle concentration of the conventional silica colloidal solution, by blending it with 0.0% by weight as a main material and preparing a curing agent. Cost reduction has been achieved.

  Similarly, the commercially available injection drug Permalock ASF (Asahi Denka Kogyo Co., Ltd., trade name) is the main material of active silica fine particle colloidal solution ASF Silica 4 (Asahi Denka Kogyo Co., Ltd., trade name). An acidic salt hardener ASF Actor M (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.) is blended, and the silica concentration is suppressed to 3.7% by weight to 7.0% by weight. By making it smaller, the amount of active silica fine particles used is further reduced than in the above example. However, both cases are equivalent in that the uniaxial compressive strength is used as a standard for quality evaluation.

  Further, in order to obtain the required strength, increasing the concentration of the injected drug solution in order to increase the uniaxial compressive strength in accordance with the conventional way of thinking causes many problems in terms of construction. That is, as the distance from the injection hole increases, the concentration of the chemical solution is affected by the groundwater, and the compressive strength decreases rapidly. Therefore, when trying to obtain the required strength by injecting a chemical solution with a constant silica concentration, it stops at the small-diameter improved body, making it impossible to create a large-diameter improved body. It must be increased. For this reason, the ground improvement work has the problem that the construction efficiency is deteriorated and the construction cost is high and the construction period is delayed, but this is not solved.

  Confirmation of the injection effect in the ground improvement work is one of the most important management items in the construction of the injection solidification method. The standard penetration test is most often used to confirm the effect of conventional ground improvement areas. The standard penetration test is often adopted because uniaxial compressive strength is used to confirm the effect of ground improvement with the recognition that the increase in liquefaction resistance is due to the increase in uniaxial compressive strength. Reflecting these recognitions in the confirmation of the effect of the improved area, the ground improvement effect is determined by adopting a standard penetration test that determines the hardness and tightness of the improved soil by changing the N value. However, since the standard penetration test is based on the premise that the strength of the ground will increase greatly due to the improvement, the difference in N value will be small in the improved area where the increase in strength in the improved soil is small. It was difficult to clearly confirm the injection effect.

  In addition to the standard penetration test, the effect of the ground improvement zone can be confirmed by methods such as indirect measurements such as hydraulic conductivity tests, simple three-component cone tests, dilatometer tests, etc. that measure the liquefaction strength in the depth direction. It has been broken.

  Then, indirect methods such as the above-mentioned hydraulic conductivity test in the in-situ test or methods for confirming “liquefaction strength” such as three-component cone test and dilatometer test, and in order to confirm “liquefaction strength” in detail With the methods such as the repeated vibration triaxial test and repeated simple shear test, the change in “liquefaction strength” is clarified even in areas that cannot be clearly identified by the standard penetration test, three-component cone test, and dilatometer test. It has been confirmed that Therefore, in the improved area as described above, the uniaxial compressive strength is adopted as the evaluation criterion, and the method of determining the ground improved area by the change of the N value and the “liquefaction strength” are directly confirmed by the above test. With the technique, no coincidence can be seen in the determination.

  Moreover, such a tendency becomes prominent when the amount of expensive silica particles is reduced to reduce the concentration of the main material of the injected chemical solution in order to reduce the cost of ground improvement work. That is, the decrease in the concentration of the main material in the injected chemical solution naturally forms an improved region in which the increase in strength in the improved soil is small, and the difference in the N value becomes even smaller.

  Based on the above situation, when the concentration of the main material of the injected chemical solution is lowered, the standard penetration test, which is judged by the change in N value, confirms the true “liquefaction strength” of the improved soil, and improves the quality of the improved area. Is difficult to determine, and other methods still have problems in terms of measurement accuracy. However, at present, in order to reduce the construction cost for ground improvement, it is an urgent task to reduce the concentration of the main material in the injected chemical solution. Under such circumstances, it is expected to propose a management method that enables simple and quick confirmation of the “liquefaction strength” of the improved soil that has been constructed, so that the quality of the ground improved can be determined concisely. .

  Furthermore, for measuring the injection range in confirming the injection effect, a method using RI, a method using elastic waves, a method using a tracer, a method using magnetism, and a method using electrical resistivity have been used. However, the RI method is difficult to handle because it uses radiation, and the elastic wave method is not applicable when the rigidity does not increase. The tracer method has a problem that the tracer is adsorbed to the soil particles and the application range is limited, and the magnetic method has a problem that it is easily affected by surrounding structures. .

  The method using electrical resistivity is a method that tries to identify the injection range from the change in soil resistance before and after injection, but the electrical resistivity does not change over time and the difference in resistance value does not become too large. Therefore, it was difficult to set the measurement time and specify the injection range, and as a result, there was a problem that the construction management of the earth and sand improvement method could not be performed accurately.

  In view of the above situation, the present invention is intended to solve the problems in the earth and sand ground improvement method, the silica particle concentration of the injected chemical solution, the gelation time to reach the sand gel state, the electrical resistivity value in the sand gel state, and the pH This ensures the true liquefaction strength, enables a large amount of chemicals to be injected over a wide area in the ground improvement area, and measures the electrical resistivity after injection to confirm the injection effect. Therefore, it is an object of the present invention to provide an earth and sand ground improvement method, an infusion chemical solution, and a construction management method thereof that can easily confirm the liquefaction strength and the range of the ground improvement region.

  The earth and sand ground improvement method according to the first and second aspects of the invention is basically an earth and sand ground improvement in which an injection chemical solution in which a colloidal solution of silica particles is a main material and a gelling agent is mixed into the main material is injected into the earth and sand ground In the construction method, set the silica particle concentration of the main material, the gelation time to reach the sand gel state, and the electrical resistivity value in the sand gel state, and inject a pH 1.5-2 injection chemical solution into the earth and sand ground to prescribe the earth and sand ground It is intended to improve the ground of liquefaction strength, and test and measure using the earth and sand of the earth and sand to improve the injected chemical solution, and confirm the gelation time to reach the sand gel state and the electrical resistivity value in the sand gel state in advance. By setting each numerical value to a predetermined value, a large-diameter improved body can be created by injecting a low-concentration chemical at low pressure and high speed. In addition, by keeping the pH of the injected drug solution in the range of 2 to 1.5, the penetration time of the injected drug solution is increased, and at the same time, the gelation time to the sand gel state that contributes to increasing the penetration amount is 10 (H) While being able to do it above, generation | occurrence | production of the gas estimated to be originated from the shell contained in the earth and sand can be prevented.

  The earth-and-soil ground improvement method according to claim 3 is the earth-and-sand ground improvement method according to claim 1 or 2, wherein the injection chemical solution is a particle concentration of 4.5 (%) with respect to the colloidal solution constituting the main material. In the following, the gelation time to reach the sand gel state is set to 10 (h) or more, and the electrical specific resistance value in the sand gel state is set to 5 (Ω · m) or less. ing.

  The injection chemical solution used in the earth and sand ground improvement method according to claims 4 and 5 is such that the concentration of silica particles or active silica particles in the colloidal solution constituting the main material is 4.5 (%) or less, and is in a sand gel state. The gelation time to reach is 10 (h) or more, and the electrical resistivity value in the sand gel state is set to 5 (Ω · m) or less, and the pH is 1.5 to 2. An improved body having a large diameter can be formed by allowing injection, and the liquefaction strength after injection can be confirmed by measuring the electrical resistivity.

  The injecting chemical solution used in the earth and sand ground improvement method according to the invention described in claim 6 contains 0.28 to active silica particles having an average particle diameter of 3 to 6 nanometers in order to blend the injecting chemical solution according to claim 5. 2. Mixing a main material dispersed in 25% by weight into a colloidal solution and a gelling agent formed by mixing 0.1 to 10.0% by weight of neutral salt and 0.1 to 5% by weight of acid salt. Thus, the concentration of the active silica particles is set to 4.5 (%) or less, the gelation time to reach the sand gel state is set to 10 (h) or more, and the electric specific resistance value in the sand gel state is 5 (Ω · m) or less. Is set.

  The construction management method of the earth and sand ground improvement method which is the invention of claim 7 specifies the relationship between the liquefaction strength and the electrical resistivity value, and at least sets the electrical resistivity value, the injection of pH 1.5-2 The chemical solution is injected into the soil in the ground improvement range, and then the electrical resistivity value in the depth direction is measured, and the ground improvement range and liquefaction strength are confirmed based on the above specific relationship. The extent and quality of the ground improvement zone can be determined by simply measuring the resistance.

  The construction management method of the earth and sand ground improvement method according to claim 8 specifies the relationship between the liquefaction strength and the electrical resistivity value, and sets the electrical resistivity value in the depth direction to the ground improvement range before the chemical solution is injected. In advance, at least set the electrical resistivity value, inject the pH 1.5-2 injection chemical solution into the soil in the ground improvement range, then measure the electrical resistivity value in the depth direction, The measured value and the above measured value are compared and collated, and the ground improvement range and liquefaction strength are confirmed based on the above-mentioned specific relations, and the ground improvement is achieved simply by measuring and comparing the electrical resistivity value before and after injection in the improved region. Can determine range and quality.

  In the construction management method of the earth and sand ground improvement method according to claim 9, the electrical resistivity value in the depth direction is measured in advance in the ground improvement range before the chemical solution is injected, and at least the electrical resistivity value is set. , Injecting the injection solution of pH 1.5-2 into the soil in the ground improvement range, then measuring the electrical resistivity value in the depth direction, and comparing the measured value with the measured value above, the ground improvement range It is possible to determine the range of the ground improvement zone simply by measuring and comparing the electrical resistivity values before and after the injection in the improvement zone.

  The earth and sand ground improvement method according to the first and second aspects of the invention is basically an earth and sand ground improvement in which an injection chemical solution in which a colloidal solution of silica particles is a main material and a gelling agent is mixed into the main material is injected into the earth and sand ground In the construction method, set the silica particle concentration of the main material, the gelation time to reach the sand gel state, and the electrical resistivity value in the sand gel state, and inject a pH 1.5-2 injection chemical solution into the earth and sand ground to prescribe the earth and sand ground It is intended to improve the ground of liquefaction strength, and test and measure using the earth and sand of the earth and sand to improve the injected chemical solution, and confirm the gelation time to reach the sand gel state and the electrical resistivity value in the sand gel state in advance. Therefore, it is possible to inject a chemical solution consisting of low-concentration silica particles at low pressure and high speed over a long period of time, thereby creating a large-diameter improved body with an increased drilling interval. Reducing the cost of the ground improvement, and provide an advantage of shortening the work period. In addition, by keeping the pH of the injected drug solution in the range of 2 to 1.5, the penetration time of the injected drug solution is increased, and at the same time, the gelation time to the sand gel state that contributes to increasing the penetration amount is 10 (H) While being able to do it above, generation | occurrence | production of the gas estimated to be originated from the shell contained in the earth and sand can be prevented.

  The earth-and-soil ground improvement method according to claim 3 is the earth-and-sand ground improvement method according to claim 1 or 2, wherein the injection chemical solution is a particle concentration of 4.5 (%) with respect to the colloidal solution constituting the main material. It is characterized by setting the electrical resistivity value in the sand gel state to 5 (Ω · m) or less by setting the gelation time to reach the sand gel state to 10 (h) or more, and reliably achieving the above function. Has the effect of doing.

  The injection chemical solution used in the earth and sand ground improvement method according to claims 4 and 5 is such that the concentration of silica particles or active silica particles in the colloidal solution constituting the main material is 4.5 (%) or less, and is in a sand gel state. The gelation time to reach is 10 (h) or more, and the electrical resistivity value in the sand gel state is set to 5 (Ω · m) or less, and the pH is set to 1.5-2. It is possible to create a large-diameter improved body by making it possible to inject it at a low cost, and to confirm the improvement effect by measuring the electrical resistivity, so that the construction and management of ground improvement can be carried out simply at low cost. I play.

  The injecting chemical solution used in the earth and sand ground improvement method according to the invention described in claim 6 contains 0.28 to active silica particles having an average particle diameter of 3 to 6 nanometers in order to blend the injecting chemical solution according to claim 5. 2. Mixing a main material dispersed in 25% by weight into a colloidal solution and a gelling agent formed by mixing 0.1 to 10.0% by weight of neutral salt and 0.1 to 5% by weight of acid salt. Thus, the concentration of the active silica particles is set to 4.5 (%) or less, the gelation time to reach the sand gel state is set to 10 (h) or more, and the electric specific resistance value in the sand gel state is 5 (Ω · m) or less. Therefore, the effect of reliably achieving the above-described effect is achieved.

  The construction management method of the earth and sand ground improvement method which is the invention of claim 7 specifies the relationship between the liquefaction strength and the electrical resistivity value, and at least sets the electrical resistivity value, the injection of pH 1.5-2 The chemical solution is injected into the soil in the ground improvement range, and then the electrical resistivity value in the depth direction is measured, and the ground improvement range and liquefaction strength are confirmed based on the above specific relationship. Since it is possible to determine the range and quality of the ground improvement area simply by measuring the resistance, the construction management of the ground improvement work can be simplified.

  The construction management method of the earth and sand ground improvement method according to claim 8 specifies the relationship between the liquefaction strength and the electrical resistivity value, and sets the electrical resistivity value in the depth direction to the ground improvement range before the chemical solution is injected. In advance, at least set the electrical resistivity value, inject the pH 1.5-2 injection chemical solution into the soil in the ground improvement range, then measure the electrical resistivity value in the depth direction, The measured value and the above measured value are compared and collated, and the ground improvement range and liquefaction strength are confirmed based on the above-mentioned specific relations, and the ground improvement is achieved simply by measuring and comparing the electrical resistivity value before and after injection in the improved region. Since the range and quality of the area can be judged, the construction management of the ground improvement work can be further simplified.

  In the construction management method of the earth and sand ground improvement method according to claim 9, the electrical resistivity value in the depth direction is measured in advance in the ground improvement range before the chemical solution is injected, and at least the electrical resistivity value is set. , Injecting the injection solution of pH 1.5-2 into the soil in the ground improvement range, then measuring the electrical resistivity value in the depth direction, and comparing the measured value with the measured value above, the ground improvement range Since the range of the ground improvement area can be determined simply by measuring and comparing the electrical resistivity values before and after the injection in the improved area, the construction management of the ground improvement work can be further simplified.

  The earth and sand ground improvement method according to the present invention is to inject an injecting chemical liquid containing a silica particle colloidal solution as a main material and a gelling agent into the main material into the earth and sand ground. It is characterized by the gelation time to reach the sand gel state, the electrical resistivity value in the sand gel state, and pH 1.5-2. In the ground improvement, the chemical solution is injected into the improvement zone at low pressure and high speed for a long time, and in the earth and sand ground into which the chemical solution is injected, a predetermined amount of silica particles are cross-linked and gelled to obtain the desired liquefaction strength. Is generated.

  The injected drug solution has a particle concentration of 4.5 (%) or less with respect to the colloidal solution constituting the main material, and the gelation time to reach the sand gel state by blending the gelling agent is 10 (h) or more. The electrical specific resistance value in the sand gel state is set to 5 (Ω · m) or less and pH 1.5 to 2 to achieve the intended purpose. As an embodiment of the injectable drug solution according to the present invention, active silica particles of 3 to 6 nanometers as a main material are dispersed in water in a range of 0.28 to 2.25% by weight. Constructs a colloidal solution with a concentration of 4.5 (%) or less, and contains 0.1 to 5.0% by weight of acidic salt and 0.1 to 10.0% by weight of neutral salt. By adding a gelling agent composed of a salt, the gelation time is adjusted to 10 (h) or more and the electrical resistivity value 5 (Ω · m) or less.

  In this embodiment, ASF silica-4 (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.) is used as the main material. It has been found that the liquefaction resistance of the improved earth and sand is substantially constant without depending on the silica particle concentration by the above setting, and the liquefaction strength satisfies the desired value as shown in the experimental results described later. By the way, the liquefaction prevention mechanism in this case is not due to consolidation like cement, but the water present between the particles of the earth and sand is replaced by the gelled substance of the chemical liquid, and this gelled substance replaces the particles of the earth and sand. It is presumed to be tied. The silica particle concentration is set to a low concentration using ultrafine particles as compared with the conventional silica particle concentration of 10% by weight. Therefore, the permeability of the chemical solution is improved, and the penetration distance is 10 even by low-pressure injection. It has been confirmed that it extends over 0.0m. As a result, the amount of silica used is reduced, and a large-diameter improved body can be created, so the ground improvement cost can be reduced.

  The gelation time to reach the sand gel state of the chemical solution is adjusted by the blending of the gelling agent. In other words, if the acid salt concentration in the gelling agent is increased, the acid salt can neutralize the alkali component in the main agent and extend the gelation time, and it can be adjusted from 10 minutes to several weeks. it can. And in order to set the gelation time to reach the sand gel state to 10 (h) or more, it is necessary to make the pH 2 or less as shown in FIG. 1, but if the pH is made 1.5 or less, it is contained in the earth and sand. Since the generation of gas presumed to be caused by the shells is sometimes caused, the pH is set in the range of 2 to 1.5. Extending the gelation time is an important adjustment because it increases the penetration distance of the drug solution and contributes to an increase in the amount of penetration. In addition, although weak acidic salts, such as a citrate and a phosphate, can also be used as an acid salt, in this Embodiment, ASF Actor M (Asahi Denka Kogyo Co., Ltd. product name) is used as an acid salt. In use, the concentration is set to 0.1 wt% to 5.0 wt%.

  In order to facilitate confirmation of the injection effect in the improved region, the injection chemical solution according to the present invention is adjusted so as to generate an electric resistivity of 5 (Ω · m) or less in the sand gel state. As described above, if the acidic salt concentration is increased in order to extend the gelation time and the pH falls within the range of 2 to 1.5, the electric conductivity in the liquid state before being injected into the earth and sand is shown in FIG. As shown, it is expected to be steep, such as 4 to 9 (mS / cm), resulting in variations due to product lots.

  Therefore, in order to set such a state to a stable value, in the present invention, adjustment is made by adding a neutral salt in addition to an acidic salt as a gelling agent. As the neutral salt, sodium chloride, potassium chloride, aluminum chloride, or the like can be used. In this embodiment, ASF Actor NS (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.) is used, and the concentration is By setting it to 0.1 wt% to 10.0 wt%, as shown in FIG. 3, the electric conductivity is set to a large value in the vicinity of 4 or 6 to 15 (mS / cm). ing.

  As described above, even if there is some variation in the desired electrical conductivity, it can be set to the desired desired electrical conductivity by controlling the amount of neutral salt added. Since the salt works to promote the gelation by destroying the diffusion double layer formed on the surface of the colloidal silica fine particles and activating the colloidal particles by collision with each other. Since the addition of salt acts on the tendency to shorten the gelation time to reach the sand gel state, it is important to set in consideration of this point in management.

  In addition, since electrical conductivity cannot be measured in the earth and sand, the gelation state and injection | pouring range of an injection chemical | medical solution are confirmed by measuring an electrical specific resistance in the sand gel state in earth and sand. The electrical specific resistance (Ω · m) is the reciprocal of the electrical conductivity (mS / cm), and has the relationship of electrical specific resistance (Ω · m) = 10 / electrical conductivity (mS / cm). Since electrical conductivity is expected to change slightly in relation to the surroundings when injected into the earth and sand, the electrical resistivity value in the sand gel state is set in the present invention. In this embodiment, 5 (Ω · m), and the electric conductivity in the liquid state is adjusted in anticipation of the change.

  As is clear from the above explanation, the earth and sand ground improvement method and the injection chemical solution according to the present invention is a method in which an injection chemical solution containing a colloidal solution of silica particles and a gelling agent is injected into the earth and sand ground. By specifying the silica particle concentration of the main material as the injection chemical and increasing the gelation time to reach the sand gel state, it is possible to inject a large amount of chemical into the ground improvement area at low pressure and high speed, and large diameter The improvement of the above and the desired liquefaction strength are generated. Furthermore, by specifying the electrical resistivity value in the sand gel state as a stable state, by measuring the electrical resistivity value after injection and using it as a viewpoint for confirming the injection effect, the liquefaction strength and the range of the ground improvement area can be reduced. It is designed to be concise.

  In the present embodiment, the colloidal solution constituting the main material has been described as being formed by dispersion of active silica fine particles. However, the present invention reaches the concentration of silica particles in the main material and the sand gel state. By specifying the gelation time and the electrical resistivity value in the sand gel state, the intended purpose is achieved. Therefore, even if the colloid solution is formed by dispersion of other silica fine particles, there is no problem. There is nothing.

  The “liquefaction strength” of the improved body produced by the present invention was confirmed by a repeated vibration triaxial test and repeated simple shear test in a room.

  As shown in Table 1, the test was conducted for case 1 having a blended silica concentration of 2.25% and case 2 having a blended silica concentration of 4.5%, and FIG. 4 shows the specimens used for each test. ing. Since the specimen for the shear test is smaller than that for the triaxial test, sampling and preparation of the specimen are relatively easy. In the test, 100 specimens are prepared to determine the liquefaction strength.

  FIG. 5 shows the results of the repeated vibration triaxial test. In the test, the number of loadings at which both amplitudes of the axial strain are 5% is plotted, and the stress ratio of 20 repetitions is set as the liquefaction strength. As shown in the figure, the liquefaction strength in the unimproved area is about 0.25, whereas in the case 1, the liquefaction strength is 0.32, and in the case 2 is 0.51. It can be seen that The repeated simple shear test and the repeated vibration triaxial test were applied to the unmodified sand. However, as the shear test and the triaxial test have similar curves, the “liquefaction strength” has almost the same value. It shows the correctness of the test value.

  FIG. 6 shows a stress-strain curve in the case of the unimproved area (a) and case 1 (b). As is clear from FIG. 6 (a), in the unimproved region where the chemical solution has not reached, the shear resistance is drastically reduced from a certain number of times due to repeated loading, and the strain amplitude rapidly increases. The destruction has occurred. On the other hand, in the improved region, the strain gradually increases as shown in FIG. 6B, but the shear resistance is maintained without increasing rapidly, and only a finite strain amplitude is generated by repeated loading. Not.

  As confirmed by the above tests, according to the present invention, the particle concentration with respect to the colloidal solution constituting the main material is 4.5 (%) or less, the gelation time to reach the sand gel state is 10 (h) or more, and the sand gel. An injectable drug solution having an electrical resistivity value of 5 (Ω · m) or less in this state has a sufficient “liquefaction strength” when it is injected into the earth and sand to form an improved body. It is clear that it will work.

  The test was also conducted in the in-situ improvement survey, but the purpose of this test is to establish a method for confirming the improvement effect at the same time as the “liquefaction strength” field test. In addition, the ground improvement method according to the present invention is carried out by adopting a test method that is considered to react sensitively to changes in strength characteristics without adopting the standard penetration test because the silica particle concentration is low. .

  FIG. 7 shows the tip cone used for each test. FIG. 7A shows a three-component cone test. By penetrating the tip cone, the penetration resistance, the peripheral friction force, and the pore water pressure can be continuously measured. FIG. 7B shows a flat blade for the dilatometer test, in which the ground is loaded in the horizontal direction by the expansion of the membrane on the side of the shattering soil.

  FIG.7 (c) is a front-end | tip cone used for an electrical specific resistance test, attaches an electrode to the part of an upper end rod, and can measure the electrical specific resistance of a ground continuously at the time of penetration. In the present invention, the test for measuring the electrical resistivity is made by preparing the injected drug solution and changing the electrical specific resistance of the ground reliably by the chemical solution injection so that the improvement effect can be easily confirmed. This is a confirmation test to ensure construction management for ground improvement.

  In the following, by showing the measurement results in each test, confirmation of the injection effect of the injectable drug solution set by the present invention, in particular, confirmation of “liquefaction strength” confirmed by laboratory tests and “improvement range” In comparison with the results of the three-component cone test and the dilatometer test, it is proved that the confirmation of the injection effect by measuring the electrical resistivity is the most efficient and accurate.

  FIG. 8 shows the result of the three-component corn test, and shows the confirmation result of the possibility that the improved region can be specified together with the confirmation of “liquefaction strength”. FIG. 8 (a) shows the result of conducting a three-component cone test for Case 1. In case 1, since the silica concentration of the main material is as low as 2.25%, the penetration resistance (qa) is slightly improved at a depth of 3 m, but the peripheral friction (fs), pore water pressure ( In ud), there is no state in which the difference can be confirmed before and after the injection. On the other hand, in case 2 where the silica concentration of the main material is 4.5%, as seen in FIG. 8B, it clearly penetrates between GL-4.0 to -7.0 m after injection. Since the resistance (qa) and the peripheral surface friction (fs) are increased and the pore water pressure (ud) is decreased, it is possible to accurately confirm the state in which the improved region is formed.

  FIG. 9 shows the result of the dilatometer test, and shows the result of confirming the possibility of specifying the improved region together with the confirmation of the “liquefaction strength” as in FIG. FIG. 9A shows the result of conducting a dilatometer test on Case 1. FIG. Also in this case, since the silica concentration of the main material is as low as 2.25%, the pressure during expansion of the membrane (p1), the soil parameter (ID), and the deformation characteristics (ED) can all be observed. Therefore, there is no difference between before and after the injection. On the other hand, in case 2, as shown in FIG. 9 (b), although the influence of the improvement effect is not seen in the soil determination result by the soil parameter (ID), the pressure (p1) at the time of membrane expansion, the deformation Both (ED), which shows the characteristics, become larger after the chemical solution is injected, and an increase in ground strength can be estimated, and at the same time, the range of the improved region can be confirmed accurately.

  FIGS. 10 to 16 show an implementation range and measurement results of the electrical resistivity test performed on Case 1, and show a confirmation state of the possibility of specifying an improved region in the horizontal direction. FIG. 10 is a plan view showing the survey area in which the present test was conducted, and the positions where the three-component cone test and the dilatometer test were conducted are also displayed for reference. The test results are in the form of an orthogonal number as shown in FIG. 1-No. The results measured at 14 positions are recorded in the depth direction. The portion indicated by the solid line in the plane shows the improved range estimated by visual inspection after excavating up to GL-3.9m, and is consistent with the improved range confirmed by the electrical resistivity. I can confirm.

  FIGS. 11 to 14 are measurement results showing the electrical resistivity values in the depth direction at the respective measurement points, and show the confirmation state of the improved region. Regarding the test results, focusing on GL-4m or deeper, before injecting the chemical solution, each measurement point similarly shows a value of electrical resistivity of 10 to 20 (Ω · m), and becomes shallower as it becomes shallower. Yes. However, it decreases to 5 (Ω · m) after the injection of the chemical solution, indicating that there is a layer showing a substantially constant value in the depth direction. This layer is the range in which the injected chemical solution penetrates, and can be clearly distinguished from the upper and lower layers that do not penetrate.

  Also, when shifting the viewpoint to the penetration state, the depth and layer thickness that penetrated mainly from the injection position appear in the target, and the penetrated layer thickness becomes smaller as it goes away from the injection center. I understand. Furthermore, when it leaves | separates from 1.5 m which is the target improvement radius of this test, it will show the electrical resistivity value in the ground before chemical | medical solution injection | pouring, and it has displayed that it has not osmose | permeated.

  15 and 16 are cross-sectional views showing the investigation range in which this test was conducted, and are measurement results showing the electrical resistivity values in the depth direction at the respective measurement points corresponding to the plan view of FIG. The confirmation status of the possibility of identifying the improvement area is shown. This result shows the improved range inferred from the measurement of electrical resistivity, and as is clear from the broken line shown in the drawing, the range of the improved area in both sections is the spherical penetration centered on the strainer. The desired penetration range (a sphere having a radius of 1.5 m) is almost the same.

  Therefore, the ground improvement using the injection chemical solution according to the present invention achieves the ground improvement by forming a predetermined improvement body even when the concentration of the colloidal solution is low by osmotic injection which is an ideal injection form. At the same time, it was confirmed that the quality and range of the improved region could be succinctly identified by measuring the electrical resistivity after injection.

  FIGS. 17 to 19 show the implementation range and measurement results of the electrical resistivity test performed on Case 2, and show the confirmation state of the possibility of specifying an improved region in the horizontal direction and the depth direction as in Case 1. The part indicated by the solid line in the plane shows the improved range estimated by visual inspection after excavating to GL-4.2m, and is consistent with the improved range confirmed by the electrical resistivity. I can confirm. However, the improved shape is No. 9 and No. No. 18 is smaller, no. Although it is larger in the direction of 8, a sandy soil layer with more fine grains than in the center is confirmed in the direction of decreasing, so that the chemical solution is directed toward the ground with good permeability. Presumed to have penetrated preferentially.

  18 and 19 are cross-sectional views showing the investigation range in which the present test was carried out. Even when the silica concentration of the colloidal solution is high, the measurement results showing the electrical resistivity value in the depth direction at each measurement point indicate the depth direction. The confirmation state of the possibility that the improvement area can be specified for is shown. The estimated improved range is in the vicinity of GL-4m where the upper end of the improved range is lower than the groundwater level GL-3m in both cross sections. According to the test excavation, it was found that a thin layer of viscous soil having a thickness of about 10 cm exists in the vicinity of GL-4m. Therefore, the difference in the permeation area appearing in the plan view is presumed that the penetration of the chemical solution was hindered by the clay. Actually, deeper than that, the ground has been improved by osmotic injection, and the infiltration range has reached 2 m from the center.

  Therefore, the ground improvement using the injection chemical solution according to the present invention achieves the ground improvement by forming a predetermined improvement body by osmotic injection which is an ideal injection form even when the concentration of the colloidal solution is high. At the same time, it was confirmed that the quality and range of the improved region could be succinctly identified by measuring the electrical resistivity after injection.

  As described above, confirmation of “liquefaction strength” by repeated vibration triaxial test and repeated simple shear test in the room, and three-component cone test, dilatometer test, and electrical resistivity test performed in the in-situ improvement body investigation Based on the field test of "liquefaction strength" and the establishment of a method for confirming the improvement effect, the earth and sand ground improvement method using the injection chemical solution according to the present invention injects a large amount of chemical solution into the ground improvement area at low pressure and high speed over a wide area. The desired liquefaction strength is generated by creating a large-diameter improved body, and the liquefaction strength in the ground improvement area and its range are simplified by measuring the electrical resistivity after injection. It became clear that it can be confirmed.

  Based on these results, the construction management method of the earth and sand ground improvement method according to the present invention specifies the relationship between the liquefaction strength and the electrical resistivity value, and at least sets the electrical resistivity value, pH 1.5-2 The injected chemical solution is injected into the soil in the ground improvement range, and then the electrical resistivity value in the depth direction is measured, and the liquefaction strength in the ground improvement range is confirmed based on the above specific relationship. Alternatively, the relationship between the liquefaction strength and the electrical resistivity value is specified, and the electrical resistivity value in the depth direction is measured in advance in the ground improvement range before the chemical solution injection, and at least the electrical resistivity value is set, Inject a pH 1.5-2 infusion solution into the soil in the ground improvement range, and then measure the electrical resistivity value in the depth direction, compare the measured value with the measured value, and Based on this, the liquefaction strength in the ground improvement range is confirmed. Below, embodiment of the construction management method by this invention is described based on a specific related figure.

FIG. 20 is a specific relation diagram with respect to the dilution ratio of “liquefaction strength ratio” (a) and “electrical resistivity value” (b) prepared in advance by a test using an injectable drug solution according to the present invention. The dilution factor used here is determined as follows.
Dilution factor = [(weight of water added by dilution) + (weight of main material)] / (weight of main material)
The construction management method according to the present invention can be confirmed that the desired improvement has been established in the ground improvement area by carrying out the following using the both related diagrams shown in FIG.
(1) With respect to the injected drug solution, the “liquefaction strength ratio” (a) and the “electrical resistivity value” are obtained in advance, and the above-described specific relation diagrams (a) and (b) are created.
(2) About injection chemical | medical solution, predetermined | prescribed "liquefaction strength ratio" is set, the silica particle density | concentration of a main material, the gelation time to reach a sand gel state, and the electrical specific resistance value in a sand gel state are set.
(3) Dilute the injected drug solution to a predetermined “dilution ratio” and inject it into the ground improvement zone.
(4) Measure the electrical resistivity in the ground improvement area.
(5) Apply the measured “electrical resistivity value” to the specific related diagram (b), specify the “dilution ratio” according to the curve, and apply the “dilution ratio” to the specific related diagram (a) to “liquefy” Find the intensity ratio.
(6) Confirm the “liquefaction strength” in the improved area from the “liquefaction strength ratio”.

  As described above, the construction management method according to the present invention obtains the “liquefaction strength ratio” and the “electrical resistivity value” relating to the injecting chemical solution in advance, and completes the creation of the specific related diagrams (a) and (b). By doing so, the subsequent management measures the work of setting the silica particle concentration of the main material of the injected drug solution, the gelation time to reach the sand gel state, and the electric specific resistance value in the sand gel state, and the electric specific resistance after injection. Construction management can be carried out simply with only the work.

  Thus, in the above management method, whether or not the desired “liquefaction strength” is established in the improved region is numerically confirmed. As is clear from the test results described above, the injectable drug solution according to the present invention is used. It has been demonstrated that the desired “liquefaction strength” can be sufficiently formed in the improved region by setting predetermined numerical values. Therefore, in addition to this, the construction management method of the earth and sand ground improvement method according to the present invention, in addition to measuring the electrical resistivity value in the depth direction before the chemical injection in the ground improvement range, set the electrical resistivity value, It is also possible to confirm the ground improvement effect by measuring the same electrical specific resistance value after injecting an injecting drug solution of pH 1.5 to 2 and comparing both measured values.

This construction management method is to confirm the ground improvement effect only by measuring the electrical resistivity value at the construction site without previously obtaining the `` liquefaction strength ratio '' and `` electrical resistivity value '' regarding the injected chemical solution, Implement as follows.
(1) The electrical resistivity value in the depth direction in the ground improvement range is measured in advance before the chemical solution is injected.
(2) After injecting the injected chemical into the soil in the ground improvement range, the electrical resistivity value in the depth direction in the ground improvement range is measured again.
(3) The measured values are compared and verified to confirm that there is a difference.

  As described above, in the construction management method according to the present invention, the electrical resistivity value set by the gelling agent in the injected drug solution is compared with the electrical resistivity value of the improved ground, and the characteristics are formulated so as to produce a large difference. Utilizing it, construction management can be performed simply by observing changes in electrical resistivity. For example, it is generally known that seawater has a low electrical resistivity value and high fresh water, and when seawater is infiltrated into the ground to be improved, the electrical resistivity value has increased due to the injection of chemicals. When the ink is soaked, the electrical resistivity value is lowered, so that the improved region can be clearly identified, and the construction management can be easily achieved. In the construction management method according to the present invention, when the electrical resistivity in the normal ground is confirmed with a rough numerical value, the preliminary measurement is also omitted and the electrical resistivity value after the chemical injection is set in advance. Construction management can be achieved simply by confirming whether or not the specific resistance value (5 (Ω · m) in the above embodiment) is reached.

  As is clear from the above description, the construction management method of the earth-and-soil improvement method according to the present invention is to inject an injecting chemical solution having at least an electrical resistivity value into the earth-and-soil ground, and then measure the electrical resistivity value in the depth direction. Then, the liquefaction strength in the ground improvement area and its range have been confirmed, and only the work of setting the electrical resistivity value in the sand gel state for the injected chemical solution and the work of measuring the electrical resistivity after injection, Construction management can be carried out in a concise manner.

  As mentioned above, although the present invention has been described in detail based on the embodiment, the earth and sand ground improvement method, the injection chemical solution, and the construction management method thereof according to the present invention are not limited to the above-described embodiment at all. The silica particles in the present invention, various aspects of the acidic salt and neutral salt in the gelling agent, as well as the blending value such as the concentration, the gelation time to reach the sand gel state to the injected drug solution, the set value of the electrical resistivity, etc. Naturally, various changes can be made without departing from the spirit of the present invention.

Correlation diagram of gelation time and pH to reach a sand gel state adjusted to specify an injectable drug solution according to the present invention Correlation diagram of electrical conductivity and pH adjusted to identify injectable drug solution according to the present invention Correlation diagram of electrical conductivity adjusted to specify injectable drug solution according to the present invention and neutral salt composition of gelling agent Specimen used for liquefaction strength test Measured value chart of number of loadings and shear stress ratio in liquefaction strength test Measured values of shear strain and shear stress in liquefaction strength test Tip cone diagram for each test method applied to in-situ testing Measured depth map of three-component cone test in the case of low-concentration silica particles Depth direction measurement value diagram of dilatometer test in case of low concentration silica particles Plan view of the improved range in the case of low-concentration silica particles subjected to in-situ testing Depth direction measurement value figure of electrical resistivity test in case of low concentration silica particles Depth direction measurement value figure of electrical resistivity test in case of low concentration silica particles Depth direction measurement value figure of electrical resistivity test in case of low concentration silica particles Depth direction measurement value figure of electrical resistivity test in case of low concentration silica particles Cross-sectional view of the improved range in the case of low-concentration silica particles subjected to in-situ testing Cross-sectional view of the improved range in the case of low-concentration silica particles subjected to in-situ testing Plan view of the improved range in the case of standard concentration silica particles subjected to in-situ testing Cross section of the improved range in the case of standard concentration silica particles subjected to in-situ testing Cross section of the improved range in the case of standard concentration silica particles subjected to in-situ testing Specific relationship chart used for construction management of ground improvement

Claims (9)

  This is a soil-and-soil improvement method that uses a colloidal solution of silica particles as the main material, and injects an injecting chemical solution containing a gelling agent into the main material into the earth and sand ground. An earth and sand ground improvement characterized by injecting a pH 1.5 to 2 infusion chemical solution that sets the electrical resistivity value in time and sand gel state into the earth and sand ground and improving the earth and sand ground to a ground with a predetermined liquefaction strength. Construction method.   The soil and soil ground improvement according to claim 1, characterized in that a test and measurement is performed using the soil and sand of the soil and soil to improve the injected chemical solution, and the gelation time to reach the sand gel state and the electrical resistivity value in the sand gel state are confirmed in advance. Construction method.   The injected drug solution has a particle concentration of 4.5 (%) or less with respect to the colloidal solution constituting the main material, a gelation time to reach a sand gel state of 10 (h) or more, and an electrical resistivity value of 5 (Ω in the sand gel state) -M) The earth-and-soil ground improvement construction method according to claim 1 or 2, characterized by being set to the following.   The silica particle concentration of the colloidal solution constituting the main material is 4.5 (%) or less, the gelation time to reach the sand gel state is 10 (h) or more, and the electrical resistivity value in the sand gel state is 5 (Ω · m) The injection chemical solution used for the earth and sand ground improvement method according to any one of claims 1 to 3, wherein the pH is set to 1.5 to 2 below.   The active silica particle concentration of the colloidal solution constituting the main material is 4.5 (%) or less, the gelation time to reach the sand gel state is 10 (h) or more, and the electrical specific resistance value in the sand gel state is 5 (Ω · m The injection chemical solution used for the earth and sand ground improvement method according to any one of claims 1 to 3, characterized in that it is set as follows.   Main material prepared by dispersing 0.28 to 2.25% by weight of active silica particles having an average particle diameter of 3 to 6 nanometers into a colloidal solution, 0.1 to 10.0% by weight of neutral salt, and 0.1 to 6. The injectable drug solution according to claim 5, comprising a gelling agent obtained by mixing 5% by weight of an acidic salt.   The relationship between the liquefaction strength and the electrical resistivity value is specified, and at least the electrical resistivity value is set, and an injection chemical solution with a pH of 1.5 to 2 is injected into the soil in the ground improvement range, and then the electrical ratio in the depth direction. A construction management method for earth and sand ground improvement method characterized by measuring a resistance value and confirming the ground improvement range and liquefaction strength based on the specific relationship.   The relationship between the liquefaction strength and the electrical resistivity value was specified, the electrical resistivity value in the depth direction was measured in advance in the ground improvement range before the chemical solution injection, and at least the electrical resistivity value was set. Inject 5 to 2 of the medicinal solution into the soil in the ground improvement range, then measure the electrical resistivity value in the depth direction, compare the measured value with the measured value, and based on the specific relationship Construction management method of earth and sand ground improvement method characterized by confirming ground improvement range and liquefaction strength.   Before injection of the chemical solution, the electrical resistivity value in the depth direction is measured in advance in the ground improvement range, and at least the electrical resistivity value is set, and an injection chemical solution of pH 1.5 to 2 is injected into the soil in the ground improvement range. Then, after measuring the electrical resistivity value in the depth direction and comparing the measured value with the measured value, the ground improvement range is confirmed, and the construction management method of the earth and sand ground improvement construction method is characterized.

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