JP2016204921A - Design method for installation range of suspension type improvement material, and ground injection method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress costs and enhance reliability of a ground injection method.SOLUTION: In the design method, a virtual form into which a suspension type improvement material penetrates is set (S10), and an advective-dispersive equation corresponding to the virtual form is established that includes an adsorption amount of the suspension type improvement material (S20). Then, a one-dimensional injection test (S50 or S110) and a uniaxial compression test (S60 or S120) are performed to obtain a distribution coefficient of a ground to be worked (S100 or S130) and a relation between a solid component mass and uniaxial compression strength (S80 or S140) based on the test result, and a delay coefficient is calculated using the distribution coefficient (S150). Then, predicted distribution of the solid component is derived by solving the advective-dispersive equation (S160), and furthermore predicted distribution of the uniaxial compression strength is derived (S170). Then, a size of an improvement body offering strength greater than a prescribed strength is derived from the predicted distribution of the uniaxial compression strength (S180). The method allows concentration and an injected amount of the suspension type improvement material used with a ground injection method to be set appropriately, thereby suppressing costs and enhancing reliability of the ground injection method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a design method for a placement range of a suspension-type improvement material that is injected into the ground to improve the ground, and a ground injection method using the design method.

  As one of the ground improvement methods for the purpose of liquefaction countermeasures, seismic reinforcement, etc., there is a ground injection method in which an improvement material is injected into the ground (for example, see Patent Document 1). Since this ground injection method can be applied to the ground where there are construction constraint conditions such as the vicinity of an existing structure and directly below or in a narrow part, it has been implemented at many sites. Also, in the ground injection method, in order to reliably improve the required range with a predetermined strength, a suspension type improving material is selected particularly when the solution type improving material cannot satisfy the predetermined strength. The amount of the improved material to be injected is obtained by multiplying the amount of soil to be injected by the porosity of the soil particles and the filling rate of the space.

Japanese Patent Laying-Open No. 2015-25293

However, the ground into which the suspension-type improving material is injected tends to decrease the uniaxial compressive strength as the distance from the injection port increases. For this reason, in order to satisfy the predetermined strength even at a position far from the injection port, a method for ensuring quality by taking a rich material and increasing the filling rate is taken, but more than necessary amount and concentration It is considered that the improved material may be injected, which contributes to an increase in cost.
This invention is made | formed in view of the said subject, The place made into the objective is to improve the reliability while suppressing the cost of a ground injection construction method.

(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

  (1) A method for designing a placement range of a suspension-type improvement material that is injected into the ground to improve the ground, wherein a virtual shape of a range in which the suspension-type improvement material penetrates the ground is set, and the soil of the ground An advection dispersion equation corresponding to the virtual shape including the amount of adsorption of the suspension-type improving material by particles as a parameter is established, and formed by a plurality of suspension-type improving materials having different concentrations and samples having different average particle sizes. From these results, we conducted a one-dimensional injection experiment using a simulated ground formed from soil sampled from a plurality of simulated grounds or construction target grounds, and a uniaxial compression test of an improved body formed in the one-dimensional injection experiment. The distribution coefficient of the construction target ground, and the relationship between the solid component mass of the suspension-type improvement material and the uniaxial compressive strength of the improved body are obtained, the delay coefficient is calculated from the distribution coefficient, and the delay coefficient and the suspension coefficient are calculated. Concentration and injection of turbidity improver Is used as a parameter to solve the advection dispersion equation to obtain a predicted distribution of the solid component of the suspension-type improvement material in the construction target ground, the predicted distribution of the solid component, and the solid component From the relationship between the mass and the uniaxial compressive strength of the improved body, a predicted distribution of the uniaxial compressive strength in the construction target ground is obtained, and based on the predicted distribution of the uniaxial compressive strength, the uniaxial compressive strength is equal to or higher than a predetermined strength. The design method of the placement range of the suspension type improvement material for obtaining the size of the improvement body of the construction target ground (Claim 1).

  The design method for the placement area of the suspension type improvement material described in this section uses the advection dispersion equation considering the amount of adsorption of the suspension type improvement material by the soil particles to determine the size and strength of the ground improvement body. It is what you want. That is, first, when the suspension-type improvement material is injected into the ground, the shape of the range in which the suspension-type improvement material penetrates into the ground is virtually set. Then, an advection dispersion equation corresponding to the set virtual shape is formed by including as a parameter the amount by which the suspended improvement material is adsorbed by the soil particles of the ground. In this case, for example, a linear adsorption isothermal relationship using a distribution coefficient is established between the concentration of the suspension-type improving material and the adsorption amount.

  Next, a one-dimensional injection experiment using a plurality of suspension-type improving materials having different concentrations and a plurality of simulated grounds formed from samples having different average particle diameters or simulated grounds formed from soil sampled from construction target grounds To implement. Whether to use the simulated ground formed from the sample or the simulated ground formed from the soil collected from the construction target ground can be appropriately selected according to the situation. In the one-dimensional injection experiment, for example, a test in which a simulated ground is formed inside an acrylic tube and the suspension-type improving material is injected into the simulated ground is performed a plurality of times while changing the concentration of the suspension-type improving material. Furthermore, a uniaxial compression test is carried out on a plurality of simulated ground improvement bodies obtained by a one-dimensional injection experiment. Then, from both experimental results, the relationship between the distribution coefficient and the mass of the solid component of the suspension-type improving material and the uniaxial compressive strength of the improved body is obtained. That is, for example, an advection dispersion equation corresponding to a model of a one-dimensional injection experiment is established, and the advection dispersion equation is calculated using a difference method or the like, thereby obtaining a distribution coefficient of the construction target ground. Also, from the solid component mass per unit volume for each position of the improved body obtained from the advection dispersion equation, the distribution of the solid component in the improved body is obtained, and in addition to the result of the uniaxial compression test, the mass of the solid component and The relationship with the uniaxial compressive strength of the improved body is obtained. Subsequently, the delay coefficient of the construction target ground is calculated from the distribution coefficient of the construction target ground and the porosity and density of the soil particles of the construction target ground.

Next, the advection dispersion equation corresponding to the set virtual shape is solved by the differential method etc. using the delay coefficient of the construction target ground, the concentration of the suspension-type improvement material to be injected and the injection amount, etc. The predicted distribution of the solid component in the construction target ground when the suspension type improvement material is injected into the ground is obtained. Furthermore, the prediction of the uniaxial compressive strength in the construction target ground is applied to the predicted distribution of the solid component in the construction target ground by applying the relationship between the mass of the solid component obtained from the experiment and the uniaxial compressive strength of the improved body. Find the distribution. And the range beyond the predetermined intensity | strength requested | required with respect to construction target ground is extracted from the prediction distribution of the uniaxial compressive strength in construction target ground, and the magnitude | size of the range is calculated | required.
The design method for the placement range of the suspension-type improving material described in this section is to obtain the size and strength of the improved body to be constructed on the construction target ground by the above procedure. For this reason, the concentration and amount of suspension-type improvement material used in the ground injection method will be set appropriately according to the average particle size of the soil particles of the construction target ground, etc., and the cost of the ground injection method will be reduced. At the same time, reliability is improved.

(2) In the above item (1), the one-dimensional injection experiment is performed using a plurality of suspension-type improving materials having different concentrations and a plurality of simulated grounds formed of samples having different average particle diameters. From the experimental results, the suspension type that obtains the relationship between the average particle size of the sample constituting the simulated ground and the distribution coefficient, and estimates the distribution coefficient of the construction target ground based on the relationship between the average particle size and the distribution coefficient A method for designing the placement range of the improved material (Claim 2).
The design method of the placement range of the suspension-type improvement material described in this section uses a plurality of suspension-type improvement materials having different concentrations and a plurality of simulated grounds formed from samples having different average particle sizes. Perform the original injection experiment. The one-dimensional injection experiment is performed a plurality of times while changing the combination of the sample forming the simulated ground and the concentration of the suspension-type improving material. And the relationship between the average particle diameter of the sample which comprises the simulated ground, and a distribution coefficient is calculated | required from the experimental result of a one-dimensional injection experiment. That is, for example, by establishing an advection dispersion equation corresponding to a model of a one-dimensional injection experiment and calculating the advection dispersion equation using a difference method or the like, the delay coefficient and the distribution coefficient for each average particle diameter of the sample can be obtained. Calculate to obtain the relationship between the average particle size of the soil particles and the distribution coefficient.

  Subsequently, based on the relationship between the average particle size of the soil particles obtained from the one-dimensional injection experiment and the distribution coefficient, the distribution coefficient of the construction target ground to be improved by actually injecting the suspension-type improvement material is obtained. That is, from the surveys conducted in advance, the average particle size of the soil particles of the construction target ground is grasped, and the relationship between the average particle size and the distribution coefficient is applied to the grasped average particle size. Estimate the distribution coefficient of the ground. At this time, when the average particle size of the soil particles varies depending on the position and depth in the construction target ground, the distribution coefficient may be estimated for each average particle size. As described above, the design method for the placement range of the suspension-type improvement material described in this section is based on the one-dimensional injection experiment using the sample to obtain the relationship between the average particle size and the distribution coefficient. Even in the case where the experiment cannot be performed with the collected soil, the distribution coefficient of the construction target ground is estimated. Furthermore, the one-dimensional injection experiment using the sample and the uniaxial compression test of the improved body formed from the sample do not need to be performed for each design of the placement range of the suspension-type improvement material, and were obtained from the experiment performed once. The relationship between the average particle diameter and the distribution coefficient and the relationship between the solid component mass and the uniaxial compressive strength are repeatedly used. Therefore, the placement range can be efficiently designed.

(3) In the above item (1), the one-dimensional injection experiment is performed using a plurality of suspension-type improving materials having different concentrations and a simulated ground formed from soil collected from the construction target ground. From the result, a method for designing the placement range of the suspension-type improving material for estimating the distribution coefficient of the construction target ground (Claim 3).
The method for designing the placement range of the suspension-type improvement material described in this section uses a plurality of suspension-type improvement materials with different concentrations and a simulated ground formed from soil collected from the construction target ground, and is one-dimensional. Perform injection experiments. At this time, a plurality of simulated grounds may be formed using soil collected from a plurality of locations by changing the position and depth in the construction target ground. In this case, the one-dimensional injection experiment is performed a plurality of times while changing the combination of the formed simulated ground and the concentration of the suspension-type improving material. Then, for example, the distribution coefficient of the construction target ground is estimated from the relationship between the solid component mass after passing through the simulated ground and the amount of drainage obtained from the experiment. Furthermore, the subsequent uniaxial compression test will be performed using an improved body of the simulated ground formed from the soil collected from the construction target ground. Therefore, the design method for the placement range of the suspension type improvement material described in this section is not only the distribution coefficient but also the delay coefficient calculated from the distribution coefficient, the relationship between the solid component mass and the uniaxial compressive strength. The calculation is performed using the parameters obtained from the experiment using the collected soil. For this reason, the difference between the design result and the construction result is reduced, and the design is performed more accurately.

(4) In the above items (1) to (3), as a virtual shape when establishing the advection dispersion equation, the suspension-type improving material penetrates from one point in the ground into a sphere centered on the one point. A method for designing a placement range of a suspension-type improving material for setting a virtual shape (Claim 4).
The design method of the placement range of the suspension type improvement material described in this section is a point in the ground as a virtual shape of the range in which the suspension type improvement material penetrates into the ground, which is set when the advection dispersion equation is established. Therefore, a virtual shape penetrating into a sphere centered on the one point is set. As a result, not only the set shape is close to the shape of the improvement body actually built in the ground, but also the advection dispersion equation when the suspension type improvement material penetrates into the sphere includes the sphere radius as a parameter. It is expressed by a relatively simple formula. For this reason, the calculation is performed efficiently while achieving both design accuracy and rationality.

(5) A method for designing a placement range of the suspension-type improving material according to (1) to (4) above, wherein the predetermined strength is 100 kPa (claim 5).
The design method of the placement range of the suspension-type improvement material described in this section generally determines a predetermined strength that the improvement body should have as a uniaxial compressive strength when determining the size of the improvement body of the construction target ground. 100 kPa required for liquefaction countermeasures. As a result, if the ground injection method is performed using the present design method, at least strength sufficient to suppress liquefaction of the ground is ensured, so that the reliability of ground improvement is further improved.

(6) In the above items (1) to (5), the suspension-type improving material comprises an ultrafine particle spherical silica-based improving material comprising spherical silicon dioxide as a main material and calcium hydroxide as a curing agent. A method for designing the placement range of the suspension-type improving material (claim 6).
The design method for the placement range of the suspension-type improving material described in this section uses an ultrafine particle spherical silica-based improving material as the suspension-type improving material to be injected into the ground. This ultrafine spherical silica-based improving material contains refined spherical silicon dioxide as a main material and calcium hydroxide as a curing agent. Further, spherical silicon dioxide has a particle size of, for example, Since it is about 1 μm, it penetrates into the ground relatively smoothly. Therefore, when the improved material is actually injected into the ground, the difference between the design result and the construction result due to the difficulty of penetration in the ground is reduced.

(7) The suspension type improvement determined based on the size of the improvement body of the construction target ground, which is obtained by the method for designing the placement range of the suspension type improvement material according to (1) to (6) above. A ground injection method for injecting the suspension-type improving material into the construction target ground according to the concentration and the injection amount of the material (Claim 7).
The ground injection method described in this section uses the design method of the placement range of the suspension-type improving material described in the above items (1) to (6). That is, by satisfying the strength and size of the improved body required for the construction target ground, the size of the improved body with a predetermined strength or higher is determined by the design method of the placement range of the suspension type improved material. Ask. And according to the density | concentration and injection | pouring amount of a suspension type improvement material set in that case, a suspension type improvement material is actually inject | poured into a construction object ground. As a result, while performing the same operation as the method for designing the placement range of the suspension-type improving material described in the above items (1) to (6), the work is efficiently performed so as to satisfy the strength required for the construction target ground. It will be advancing.

  Since this invention is the above structures, it becomes possible to suppress the cost of a ground injection construction method and to improve reliability.

It is a flowchart which shows an example of the procedure of the design method of the placement range of the suspension type improvement material which concerns on embodiment of this invention. It is an image figure which shows the virtual shape of the osmosis | permeation range of a suspension type improvement material. It is the chart which showed the physical characteristic of the sample used in the one-dimensional injection experiment. It is the table | surface which showed the experimental condition of the one-dimensional injection | pouring experiment. It is a schematic diagram of the experimental procedure of a one-dimensional injection experiment. FIG. 6 is a schematic diagram of an experimental procedure of a one-dimensional injection experiment subsequent to FIG. 5 and a uniaxial compression test. It is the graph which showed the test result of the uniaxial compression test. It is the table | surface which showed together the item of the one-dimensional injection experiment, the delay coefficient, and the distribution coefficient. It is the image figure which showed the model of the one-dimensional injection experiment. It is the graph which showed the relationship between the average particle diameter of a sample, and a distribution coefficient. It is the graph which showed the absolute value of the intercept and inclination of the approximate line of the graph of FIG. It is the graph which showed the relationship between the position of a specimen, and the solid component mass per unit volume in a specimen. It is the graph which showed the relationship between the solid component mass per unit volume in a test body, and uniaxial compressive strength. It is the graph which showed the relationship between the average particle diameter of soil particles, and the inclination of the approximate straight line shown in FIG. It is a schematic diagram of a drum can injection experiment. 5 is a chart showing experimental conditions and experimental results of a drum can injection experiment. It is a graph which shows the distribution of the solid component density | concentration of the improved body in a drum, the distribution of solid component mass, and the distribution of uniaxial compressive strength computed from the advection dispersion | distribution equation. It is the plot figure which compared the uniaxial compressive strength estimated from the advection dispersion equation, and the uniaxial compressive strength calculated | required from the drum injection | pouring experiment. It is the plot figure which compared the radius of the improved body estimated from the advection dispersion | distribution equation, and the radius of the improved body calculated | required from the drum injection experiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. Note that the same portions are denoted by the same reference numerals throughout the drawings.
FIG. 1 is a flowchart showing an example of a procedure of a method for designing a placement range of a suspension-type improving material according to an embodiment of the present invention. First, the design method of the placement range of the suspension-type improving material according to the embodiment of the present invention will be described with reference to the flowchart of FIG.
S10 (virtual shape setting of infiltration range): As shown in FIG. 2 (a), when the suspension-type improving material is injected into the ground G from the tip 20a of the injection tube 20, the suspension-type improving material becomes the ground G. Virtually set the shape of the range to penetrate. In the example of FIG. 2, a virtual shape 24 is set in which the suspension-type improving material penetrates from the position of the tip 20 a of the injection tube 20 into a sphere centered at the position of the tip 20 a.

ここで、〔数１〕〜〔数４〕は、順に、懸濁型改良材の入ってくる量、溜まる量、吸着される量、出ていく量を示している。 S20 (form of advection dispersion equation): An advection dispersion equation corresponding to the virtual shape set in S10 is established. For example, in establishing the advection dispersion equation corresponding to the spherical virtual shape 24 shown in FIG. 2A, the radius is r, the Darcy flow velocity at the point of the radius r is v _r , and the ground is shown in FIG. The porosity of the soil particles of G is n _e , the density (dry density) of the soil particles of the ground G is ρ _a , the concentration of the suspension-type improving material at the point of the radius r is C _r , and the suspended by the soil particles. Let q be the amount of turbidity improving material. The input and output of the suspension-type improving material in the Δr layer shown in FIG.

Here, [Equation 1] to [Equation 4] indicate, in order, the amount of the suspension-type improving material that enters, the amount that accumulates, the amount that is adsorbed, and the amount that exits.

ここで、土粒子の密度をρ_Ｓとして、遅延係数Ｒ_ｄを〔数７〕のように定義する。

すると、〔数７〕の関係から、移流分散方程式は、最終的に〔数６〕から〔数８〕のように書ける。

Further, assuming that the linear adsorption isothermal relationship of q = K _d C holds when K _d is a distribution coefficient, considering the balance equation of the improved material from the above [Equation 1] to [Equation 4], A relation such as [Equation 5] is established, and [Equation 5] is rearranged to become [Equation 6].

Here, the density of the soil particles is defined as ρ _S , and the delay coefficient R _d is defined as [Equation 7].

Then, from the relation of [Equation 7], the advection dispersion equation can be finally written as [Equation 6] to [Equation 8].

S30 (Selection of collected soil experiment): It is selected whether or not to perform a later-described one-dimensional injection experiment and uniaxial compression test using soil collected from the construction target ground. If it is selected to perform the experiment using the collected soil (YES), the process proceeds to S110, and if it is selected not to perform the experiment using the collected soil (NO), the process proceeds to S40.
S40 (Selection of sample experiment): It is selected whether or not a one-dimensional injection experiment and a uniaxial compression test, which will be described later, are performed using soil particles of the sample. If it is selected to perform the experiment using the sample (YES), the process proceeds to S50, and if it is selected not to perform the experiment using the sample (NO), the process proceeds to S90.

  S50 (Implementation of one-dimensional injection experiment): A one-dimensional injection experiment is performed using a plurality of suspension-type improving materials having different concentrations and a plurality of simulated grounds formed of samples having different average particle diameters. Here, as the suspension-type improving material, an ultrafine particle spherical silica-based improving material containing spherical silicon dioxide having a particle diameter of about 1 μm as a main material and calcium hydroxide as a curing agent is used, and the concentration is 400%, 800% and 1000% water silica mass ratio (W / Si) is used. Further, samples A to C having characteristics shown in the chart of FIG. 3 using quartz sand No. 6, No. 7, and No. 8 are adopted as samples forming the simulated ground. The chart of FIG. 4 shows the experimental conditions of the one-dimensional injection experiment. In this experiment, an acrylic tube having a length of 60 cm and a diameter of 5 cm was used, and a filter layer having a thickness of 5 cm was formed on the upper and lower ends of the tube with gravel having a particle size of about 5 mm, and the sample soil was sandwiched between the filter layers. Create The lower part of the acrylic tube is connected to a deaeration water tank and an improvement material tank.

  A specific procedure of the one-dimensional injection experiment will be described with reference to FIGS. First, as shown in FIG. 5 (a), after placing the lower pedestal 32 and the filter layer, the samples (samples A to C) are deposited in the acrylic tube 30 by the dry-drop method, and the sides are lightly tapped. Adjust the density. Further, as shown in FIG. 5B, after the upper pedestal 34 and the filter layer are installed, the deaerated water is passed through the deaerated water tank 36 from the lower part of the acrylic tube 30 with a water head difference of 1.7 m. And after confirming that the deaeration water has flowed out from the upper part of the acrylic tube 30, the water flow is stopped. Next, as shown in FIG. 5 (c), an improvement material having a predetermined concentration (400%, 800%, 1000% in W / Si) is injected from the improvement material tank 38 into the injection pressure (water head) It is made to permeate over 1.7m-2.0m in terms of difference. Then, as shown in FIG. 5 (d), immediately after the degassed water in the sample is replaced with the improving material in the calculation, a slightly turbid and nearly transparent improving material flows out from the upper part of the acrylic tube 30. .

Thereafter, as shown in FIG. 6A, the improvement material suspended in white is discharged from the upper part of the acrylic tube 30 by continuously flowing the improvement material. When the white suspended improvement material is discharged from the acrylic tube 30, first 100 ml is collected, then 75 ml and then 65 ml are individually collected in a container, and the penetration of the improvement material is stopped after collection. And the collected waste_water | drain is put into the evaporating dish 40 separately, and is left still for 24 hours in a ventilation type | mold constant temperature drying furnace according to the method of water content ratio measurement, The mass of the solid component which remained after evaporation is measured. Next, as shown in FIG. 6B, the injection hole portion is closed so that the improvement material does not flow out of the sample in the acrylic tube 30, and then the improvement material injection tube is removed from the acrylic tube 30. Then, curing is performed at a room temperature of 25 ° C. for a predetermined number of days (see FIG. 4).
In this step, the one-dimensional injection experiment according to the above procedure is performed a plurality of times while changing the combination of the samples A to C and the concentration of the improving material (W / Si) (in the chart of FIG. 4). See combination).

S60 (Implementation of uniaxial compression test): A uniaxial compression test is carried out for a plurality of improved bodies created by the one-dimensional injection experiment of S50. That is, when the curing in the acrylic tube 30 shown in FIG. 6 (b) reaches a predetermined number of days and the improved body of the sample is constructed, according to the sampling position from the injection hole shown in the chart of FIG. As shown in (c), the improved body 42 is cut together with the acrylic tube 30 to a height of 10 cm. Then, the improved sample 42 of the sample is taken out from the acrylic tube 30 and set in the uniaxial compression tester 44 to perform the uniaxial compression test. The results of the uniaxial compression test conducted by the present inventors for each improved sample are shown in the chart of FIG. In the results shown in FIG. 7, the uniaxial compressive strength of all the specimens (sample improvements) is 100 kPa (kN / m ² ) or more.

  S70 (derivation of relationship between average particle size and distribution coefficient): The relationship between the average particle size of soil particles and the distribution coefficient is obtained based on the result of the one-dimensional injection experiment of S50. FIG. 8 shows the specifications of a one-dimensional injection experiment conducted by the present inventors. Here, the “solid component mass per unit volume of the discharged liquid” in the chart of FIG. 8 is obtained by collecting the discharged liquid discharged from the upper part of the acrylic tube 30 as shown in FIG. After the liquid is oven dried, the mass of the remaining solid component is measured, and the measured mass is converted to the mass per unit volume. From this result, it can be seen that as the amount of discharged liquid increases, the mass of solid components in the discharged liquid gradually increases. This means that the amount by which the solid component of the improving material is adsorbed by the sand particles decreases as the penetration of the improving material continues.

そして、上記Ｓ５０で行った一次元注入実験では、改良材の注入時間が短く、アクリル管の管路が小さいことから、分散の影響は小さいと考えて、〔数９〕から分散項を外して〔数１０〕のようにする。

Here, as a model of the one-dimensional injection experiment performed in S50, a model as shown in FIG. 9 is used in which the axis in the permeation direction is the x axis and the injection hole is the origin. Assuming that the solid component adsorption of the improved material by the soil particles is always expressed by a linear adsorption isotherm, it is expressed by q = K _d C (q: the concentration of the substance adsorbed by the soil particles per unit volume) , K _d : partition coefficient, C: concentration of improved material). When the delay coefficient is R _d , the dispersion coefficient is D _x , the sample porosity is _ne , the average gap flow velocity in the x-axis direction is v _x , and the solid component concentration is C, the one-dimensional as shown in FIG. The advection dispersion equation is expressed as [Equation 9].

Then, in the one-dimensional injection experiment performed in S50, since the injection time of the improved material is short and the acrylic pipe line is small, it is considered that the influence of dispersion is small, and the dispersion term is removed from [Equation 9]. [Equation 10]

又、Δｘ＝１．０ｃｍ、Δｔ＝０．１秒とし、アクリル管の端部ｘ＝０ｃｍから注入する改良材の濃度は常に１００％で、ｘ＝６０ｃｍで排出されると考える。ここでは、流速は常に一定であると仮定し、図８の図表に示した注入継続時間と排出液量の総和とから平均的な流速を計算し、使用することとする。 In the present embodiment, it is assumed that [Equation 10] is solved using a difference method. Assuming that the acrylic tube is divided into n layers with a thickness of Δx, the calculation of the concentration C ^{k + 1} _i at time i in the k + 1 layer can be expressed as [Equation 11].

Further, it is assumed that Δx = 1.0 cm, Δt = 0.1 seconds, and the concentration of the improved material injected from the end x = 0 cm of the acrylic tube is always 100%, and is discharged at x = 60 cm. Here, it is assumed that the flow rate is always constant, and the average flow rate is calculated from the injection duration time and the total amount of the discharged liquid shown in the chart of FIG. 8 and used.

〔数１１〕を計算するためには、遅延係数Ｒ_ｄが定められている必要があることから、計測終了時の排出液（６５ｍｌ）の固形成分の濃度に対して、〔数１１〕を用いて計算した同時刻（計測終了時に相当）の濃度が最も近くなる、遅延係数Ｒ_ｄを同定する。更に、同定した遅延係数Ｒ_ｄと〔数７〕とから、分配係数Ｋ_ｄを計算する。図８の図表には、同定した遅延係数Ｒ_ｄ及び分配係数Ｋ_ｄを合わせて示している。そして、図８に示した試料の平均粒径と分配係数とから、図１０に示すような、平均粒径と分配係数との関係を導出する。なお、本実施例における平均粒径とは、５０％粒径を示している。図１０から、平均粒径と分配係数との関係は、略直線で近似でき、改良材の濃度によって傾きが異なることが分かる。 The amount of the solid component of the improving material present in the specimen is the sum of the solid component in the improving material solution existing in the gap between the soil particles and the solid component adsorbed by the soil particles. For this reason, when the substance concentration of the solid component present in the sample per unit volume is Q, Q is expressed as [Equation 12].

In order to calculate [Equation 11], since the delay coefficient _Rd needs to be determined, [Equation 11] is used for the concentration of the solid component of the discharged liquid (65 ml) at the end of the measurement. Thus, the delay coefficient _{Rd at} which the concentration at the same time (corresponding to the end of measurement) calculated is the closest is identified. Further, the distribution coefficient K _d is calculated from the identified delay coefficient R _d and [Equation 7]. The chart of FIG. 8 shows the identified delay coefficient R _d and distribution coefficient K _d together. Then, the relationship between the average particle diameter and the distribution coefficient as shown in FIG. 10 is derived from the average particle diameter and the distribution coefficient of the sample shown in FIG. In addition, the average particle diameter in a present Example has shown 50% particle diameter. FIG. 10 shows that the relationship between the average particle diameter and the distribution coefficient can be approximated by a substantially straight line, and the slope varies depending on the concentration of the improved material.

S80 (Derivation of relationship between solid component mass and uniaxial compressive strength): Based on the result of the one-dimensional injection experiment of S50 and the uniaxial compressive test of S60, the solid component mass in the sample and the uniaxial compressive strength of the sample improvement Seeking the relationship. Specifically, first, the solid component mass per unit volume in the sample is calculated using the above-described [Equation 11], [Equation 12], the delay coefficient R _d , and the distribution coefficient K _d , and FIG. As shown in Fig. 5, the relationship between the mass of the solid component per unit volume and the position of the specimen is obtained for each sample. 12A to 12C correspond to samples A to C, respectively. In all samples, the mass of the solid component present in the specimen is small when the concentration of the improving material is low, and the mass of the solid component is substantially constant up to about 45 cm from the injection hole. I understand.
Next, while obtaining the solid component mass per unit volume at the intermediate position of the specimen from FIG. 12, using the result of the uniaxial compression test shown in FIG. 7, the relationship between the solid component mass and the uniaxial compressive strength, It calculates | requires as shown in FIG. The approximate straight line shown in FIG. 13 is adjusted to pass through the origin. From FIG. 13, it can be seen that the solid component mass and the uniaxial compressive strength are generally in a proportional relationship, and that the same solid component mass tends to increase the uniaxial compressive strength as the particle size of the sample decreases.

そのため、上記の〔数１３〕に、分配係数を特定したい位置の土粒子の平均粒径と、任意の懸濁型改良材の濃度（水シリカ比）とを適用すれば、分配係数が求まることとなる。このようにして、施工対象地盤の分配係数を推定する。なお、ここでは、図１０の３本の近似直線から、分配係数を特定したい位置の土粒子の平均粒径が０．１５ｍｍである場合の、分配係数を推定する。すると、上述した近似直線の式から、平均粒径が０．１５ｍｍの場合の分配係数は、水シリカ比が４００％で０．３２２、水シリカ比が８００％で０．４６３、水シリカ比が１０００％で０．７０８となる。 S90 (Diversion of previous experimental results): When the same experiment as the experiment described in S50 and S60 has been performed before, S50 to S80 may be omitted by diverting the previous experimental results.
S100 (Estimation of distribution coefficient): Using the relationship between the average particle diameter obtained in S70 and the distribution coefficient, or the relationship between the average particle diameter obtained from the results of previous experiments and the distribution coefficient, the construction target ground Find the distribution coefficient of. Here, the relationship shown in the graph of FIG. 10 is used as the relationship between the average particle diameter and the distribution coefficient. When the approximate straight line shown in FIG. 10 is expressed by a formula where x is 50% particle size and y is a distribution coefficient, the approximate straight line having a water-silica ratio of 400% is y = 0.665-2.29x, and the water-silica ratio is An approximate line of 800% is y = 1.15-4.58x, and an approximate line of 1000% water-silica ratio is y = 1.95-8.28x. For this reason, when the intercept of these approximate straight lines and the absolute value of the inclination are shown in a graph, it is as shown in FIG. The curve in FIG. 11 is an approximate curve by an exponential function. From these approximate curve, the average particle size D ₅₀ Metropolitan Water silica ratio W / S _i and soil particles of the modifying material, approximation formula for obtaining the distribution coefficient Kd is as [Equation 13].

Therefore, the distribution coefficient can be obtained by applying the average particle diameter of the soil particles at the position where the distribution coefficient is desired to be specified and the concentration of any suspension-type improving material (water silica ratio) to the above [Equation 13]. It becomes. In this way, the distribution coefficient of the construction target ground is estimated. Here, the distribution coefficient when the average particle diameter of the soil particles at the position where the distribution coefficient is desired to be specified is 0.15 mm is estimated from the three approximate lines in FIG. Then, from the above approximate straight line equation, the distribution coefficient when the average particle size is 0.15 mm is 0.322 when the water silica ratio is 400%, 0.463 when the water silica ratio is 800%, and the water silica ratio is It becomes 0.708 at 1000%.

S110 (Implementation of one-dimensional injection experiment): A one-dimensional injection experiment is performed using a plurality of suspension-type improving materials having different concentrations and a simulated ground formed from soil collected from the construction target ground. Similar to S50, an ultrafine spherical silica-based improving material containing spherical silicon dioxide having a particle diameter of about 1 μm as a main material and calcium hydroxide as a curing agent is used as a suspension-type improving material. , Having a water silica mass ratio (W / Si) of 400%, 800%, and 1000%. In addition, a plurality of simulated grounds are formed using soil collected from different positions in the construction target ground. When the average particle diameter of the soil particles of the construction target ground does not change much in the construction target ground, only one simulated ground may be formed. In this experiment, an experiment similar to the procedure described in S50 is performed using the same instrument as the experiment instrument used in S50, and detailed description thereof is omitted.
S120 (Implementation of uniaxial compression test): A uniaxial compression test is carried out on the improved soil of the ground sample to be constructed, created by the one-dimensional injection experiment of S110. Since this test is performed in the same procedure as described in S60 above, detailed description is omitted.

S130 (distribution coefficient estimation): The distribution coefficient of the construction target ground is obtained based on the result of the one-dimensional injection experiment of S110. First, from the result of the one-dimensional injection experiment, a value corresponding to “solid component mass per unit volume of discharged liquid” shown in the chart of FIG. 8 is calculated. Furthermore, as a model of the one-dimensional injection experiment performed in S110, a model as shown in FIG. 9 is considered in which the axis in the infiltration direction is the x axis and the injection hole is the origin. Then, the equation of [Equation 11] is derived as in S70. Therefore, identification against the concentration of solid components of the effluent at the end of the measurement (65 ml), the concentration of the same time was calculated (corresponding to the time of end of measurement) is closest using [Equation 11], the delay factor R _d To do. Further, the distribution coefficient K _d is calculated from the identified delay coefficient R _d and [Equation 7]. This distribution coefficient _Kd is the estimated distribution coefficient of the construction target ground.
S140 (Derivation of relationship between solid component mass and uniaxial compressive strength): Based on the result of the one-dimensional injection experiment of S110 and the uniaxial compression test of S120, the improved body of the simulated ground formed from the soil collected from the construction target ground The relationship between the solid component mass and the uniaxial compressive strength of the improved body is obtained. Since this step is the same as the procedure described in S80 above, detailed description is omitted.

S150 (delay coefficient calculation): The delay coefficient is calculated using the estimated distribution coefficient of the construction target ground. Because the relationship between the distribution coefficient K _d and the delay factor R _d is as shown in [Equation 7], from the distribution coefficient K _d, and the density [rho _s and porosity n _e of soil particles construction target ground, The delay coefficient _Rd is calculated. For example, the density of the soil particles [rho _s and porosity _{n e} is 2.707 and 0.5, as in the example shown in S100, the distribution coefficient when the average particle size of 0.15mm are water silica When the ratio is 0.322 at 400%, the water silica ratio is 0.463 at 800%, and the water silica ratio is 0.708 at 1000%, the delay coefficients are 1.87 (400% water silica), respectively. 2.25 (water silica ratio 800%), 2.92 (water silica ratio 1000%). When the distribution coefficient is estimated in S130, the delay coefficient is identified before the distribution coefficient is estimated. Therefore, the delay coefficient identified at that time becomes the delay coefficient of the construction target ground.

S160 (Derivation of predicted distribution of solid component): [Equation 8] is solved using the calculated delay coefficient, and the predicted distribution of the solid component in the construction target ground is obtained. First, the delay coefficient _Rd is used, the injection amount and concentration of the suspension-type improving material are set, and the advection dispersion equation of [Equation 8] is solved by the difference method or the like, and the radius and solid component of the spherical improvement body are solved. The relationship with the density of the toner is obtained (for example, see FIG. 17A described later). Further, by using the obtained result and [Equation 12], the relationship between the radius of the spherical improved body and the mass of the solid component is obtained (for example, see FIG. 17B described later), so that the construction target ground The predicted distribution of the solid component of the improved body formed into a spherical shape is obtained.

  S170 (Derivation of predicted distribution of uniaxial compressive strength): Based on the relationship between the solid component mass and the uniaxial compressive strength obtained in S80 or S140, a predicted distribution of uniaxial compressive strength in the construction target ground is obtained. That is, when the solid component mass and the uniaxial compressive strength are in a relationship as shown in FIG. 13, for example, if x is the solid component mass and y is the uniaxial compressive strength, the approximate straight line of the experiment of sample A is y = 57. .568, the approximate straight line of the sample B experiment is y = 59.398, and the approximate straight line of the sample C experiment is y = 119.93. FIG. 14 shows the relationship between the slopes of these approximate lines and the 50% particle size of each sample that can be confirmed in FIG. Further, the approximate straight line shown in FIG. 14 is y = 226.37-902.48x, where x is 50% particle size and y is the slope of the approximate straight line in FIG. For this reason, when the 50% particle size of the construction target ground is 0.15 mm, the slope of the approximate curve of the relationship between the solid component mass and the uniaxial compressive strength in this case can be calculated as 90.998 (≈91). . Therefore, the relationship between the solid component mass (x) and the uniaxial compressive strength (y) when the 50% particle size of the construction target ground is 0.15 mm can be expressed by the approximate expression y = 91x. From this relationship and the predicted distribution of the solid component obtained in S160, a predicted distribution of uniaxial compressive strength in the construction target ground is obtained (for example, see FIG. 17C described later).

S180 (Derivation of size of improved body): Based on the predicted distribution of uniaxial compressive strength obtained in S170, the size of the improved body having uniaxial compressive strength equal to or higher than a predetermined strength is obtained. That is, for example, a portion having a uniaxial compressive strength of 100 kPa or more is identified from the predicted distribution of uniaxial compressive strength, and the size of the portion (spherical radius if a spherical virtual shape is set in S10 above) You can ask for.
By the steps so far, an example procedure of the design method for the placement range of the suspension-type improving material according to the embodiment of the present invention is completed.

  Next, a drum can injection experiment conducted by the present inventors in order to verify the design method of the placement range of the suspension-type improving material according to the embodiment of the present invention will be described. FIG. 15 shows a schematic diagram of a drum can injection experiment. The size of the drum can 50 used in the experiment is as shown in FIG. A crushed stone drainage layer 52 was provided in the lowermost layer of the drum can 50, and four drain pipes 54 were installed along the inner peripheral surface of the drum can 50. The drain pipe 54 is used for water injection in the saturation process, and is used for drainage when the improved material is injected. Then, the silica sand (samples A to C) with adjusted particle size is put into the drum can 50 in five layers, and each layer is compacted with a manual rammer to adjust the relative density to 60%, and the sand layer. An injection tube 56 provided with a discharge port 56a was installed in the central part. After completion of the sand packing, a mortar 58 was placed on the top 5 cm of the drum can 50 and capped. Thereafter, deaerated water was poured from below, and after the deaerated water filled the sand sample in the drum 50, the suspension-type improving material was injected from the injection tube 56. The injection rate was 1 liter per minute and a total of 42 liters of improved material was injected. And after curing for a fixed period, the improved body was dug and the dimension was measured, and then the specimen was cut out and subjected to a uniaxial compression test. The table of FIG. 16 collectively shows the experimental conditions and the experimental results. In addition, the experiment is divided into two times, the first time and the second time. In FIG. 16, the formulation is the water silica ratio (W / Si) of the improved material, and the improvement rate is the volume of the improved material formed in the experiment, and the ideal improved material when the improved material fills the gap. The value divided by the volume is shown.

  According to the design method of the placement range of the suspension-type improving material according to the embodiment of the present invention, it is assumed that the improving material penetrates into the drum can in the spherical range as shown in FIG. Solved the equation. No. of the first experiment. As a calculation result corresponding to 1 and 3 to 5, FIG. 17A shows the relationship between the radius of the improved body and the concentration of the improved material (when the concentration of the injected improved material is 100%). FIG. 17B shows the relationship with the component mass, and FIG. 17C shows the relationship between the improved body radius and the uniaxial compressive strength. The delay coefficient used in the calculation is obtained from the relationship between the average particle diameter and the distribution coefficient shown in FIG. 10, the graph of FIG. 11 obtained from the approximate straight line of FIG. 1 (see S100 in FIG. 1), and the delay coefficient identified from [Equation 7] (see S150 in FIG. 1).

  Further, FIGS. 18 and 19 show a comparison between the result obtained from the drum can injection experiment and the result estimated from the method for designing the placement range of the suspension-type improving material according to the embodiment of the present invention. FIG. 18 is a comparison result of uniaxial compressive strength, and FIG. 19 is a comparison result of the radius of the improved body. As can be seen from the figure, there are some cases where the experimental results and the estimation results are far apart, but generally good results were obtained. Although illustration is omitted, the volume of the improved body obtained from the drum can injection experiment is compared with the volume of the improved body estimated from the design method of the placement range of the suspension type improved material according to the embodiment of the present invention. As a result, the same tendency as the comparison result of the radius of the improved body shown in FIG. 19 was observed.

Now, according to the embodiment of the present invention configured as described above, the following operational effects can be obtained. That is, the design method of the placement range of the suspension-type improvement material according to the embodiment of the present invention uses the advection dispersion equation considering the amount of suspension-type improvement material adsorbed by the soil particles, and improves the ground The size and strength of the are determined. That is, first, as shown in FIG. 2, when the suspension-type improving material is injected into the ground G, a shape 24 in a range in which the suspension-type improving material penetrates into the ground G is virtually set (see FIG. 2). 1 S10). Then, an advection dispersion equation corresponding to the set virtual shape 24 is formulated including the amount of the suspension-type improving material adsorbed by the soil particles of the ground as a parameter (S20 in FIG. 1). At this time, for example, as shown in [Equation 1] to [Equation 5], a linear adsorption isothermal relationship using the distribution coefficient _Kd is established between the concentration C of the suspension-type improving material and the adsorption amount q. It stands as a thing.

Next, a one-dimensional injection experiment using a plurality of suspension-type improving materials having different concentrations and a plurality of simulated grounds formed from samples having different average particle diameters or simulated grounds formed from soil sampled from construction target grounds (S50 or S110 in FIG. 1). Whether to use the simulated ground formed from the sample or the simulated ground formed from the soil collected from the construction target ground can be appropriately selected according to the situation (S30 and S40 in FIG. 1). For example, as shown in FIGS. 5 and 6 (a) and 6 (b), the one-dimensional injection experiment is a test in which a simulated ground is formed inside the acrylic tube 30 and a suspension type improvement material is injected into the simulated ground. This is performed several times while changing the concentration of the suspension-type improving material. Further, as shown in FIG. 6C, a uniaxial compression test is performed on a plurality of simulated ground improvement bodies obtained by the one-dimensional injection experiment (S60 or S120 in FIG. 1). Then, from both experimental results, the relationship between the distribution coefficient K _d , the mass of the solid component of the suspension-type improving material, and the uniaxial compressive strength of the improved body is obtained (S80 or S140 in FIG. 1). That is, for example, by establishing an advection dispersion equation such as [Equation 10] corresponding to a model of a one-dimensional injection experiment (see FIG. 9), and calculating the advection dispersion equation using a difference method or the like, The distribution coefficient _Kd of the construction target ground is obtained. Further, from the solid component mass per unit volume at each position of the improved body obtained from the advection dispersion equation, the distribution of the solid component in the improved body as shown in FIG. 12 is obtained, and further combined with the result of the uniaxial compression test. The relationship between the mass of the solid component as shown in FIG. 13 and the uniaxial compressive strength of the improved body is obtained. Subsequently, using [Equation 7], the delay coefficient R _d of the construction target ground is calculated from the distribution coefficient K _d of the construction target ground, the porosity _ne and the density ρ _s of the soil particles of the construction target ground. (S150 in FIG. 1).

Next, the advection dispersion equation [Equation 8] corresponding to the set virtual shape is solved by the difference method or the like using the delay coefficient R _d of the construction target ground, the concentration of the suspension type improvement material to be injected, the injection amount, and the like. Thus, the predicted distribution of the solid component in the construction target ground when the suspension type improvement material is injected into the construction target ground is obtained (S160 in FIG. 1). Furthermore, the prediction of the uniaxial compressive strength in the construction target ground is applied to the predicted distribution of the solid component in the construction target ground by applying the relationship between the mass of the solid component obtained from the experiment and the uniaxial compressive strength of the improved body. A distribution is obtained (S170 in FIG. 1). Then, from the predicted distribution of the uniaxial compressive strength in the construction target ground, for example, a range of a predetermined strength or more required for the construction target ground is extracted, and the size of the range is obtained (S180 in FIG. 1). .
The design method of the placement range of the suspension-type improving material according to the embodiment of the present invention obtains the size and strength of the improved body to be constructed on the construction target ground by the above procedure. For this reason, the concentration and amount of suspension-type improvement material used in the ground injection method can be set appropriately according to the average particle size of the soil particles in the construction target ground, etc., and the cost of the ground injection method can be reduced. In addition, the reliability can be improved.

Moreover, the design method of the placement range of the suspension-type improvement material according to the embodiment of the present invention includes a plurality of suspension-type improvement materials having different concentrations and a plurality of simulated grounds formed of samples having different average particle diameters. When a one-dimensional injection experiment is carried out using, the combination of the sample forming the simulated ground and the concentration of the suspension-type improving material (see FIG. 4) is changed several times. Then, the relationship between the average particle size of the sample constituting the simulated ground and the distribution coefficient _Kd is obtained from the experimental result of the one-dimensional injection experiment (S70 in FIG. 1). That is, for example, an advection dispersion equation corresponding to a model of a one-dimensional injection experiment is established, and the advection dispersion equation is calculated using a difference method or the like, whereby the delay coefficient R _d and the distribution for each average particle diameter of the sample are calculated. The coefficient K _d is calculated (see FIG. 8), and the relationship between the average particle size of the soil particles and the distribution coefficient K _d as shown in FIG. 10 is obtained.

Then, based on the relationship between the average particle size and distribution coefficient K _d for soil particles obtained from one-dimensional injection experiments, the distribution coefficient of the construction target ground make improvements by injecting actually suspended type improver K _d Is obtained (S100 in FIG. 1). That is, for example, graphs as shown in FIGS. 10 to 11 are obtained, and an approximate expression as shown in [Equation 13] is obtained. Then, from the surveys conducted in advance, the average particle size of the soil particles of the construction target ground is grasped, and the grasped average particle size and the arbitrary concentration of the improvement material are applied to [Equation 13], so that the construction target is obtained. Estimate the distribution coefficient _{Kd of the} ground. At this time, when the average particle size of the soil particles varies depending on the position and depth in the construction target ground, the distribution coefficient K _d may be estimated for each average particle size. As described above, the design method for the placement range of the suspension-type improving material according to the embodiment of the present invention is to obtain the relationship between the average particle diameter and the distribution coefficient _Kd by a one-dimensional injection experiment using a sample. Even in the case where the experiment cannot be performed with the soil sampled from the construction target ground, the distribution coefficient K _d of the construction target ground can be estimated. Furthermore, the one-dimensional injection experiment using the sample and the uniaxial compression test of the improved body formed from the sample do not need to be performed for each design of the placement range of the suspension-type improvement material, and were obtained from the experiment performed once. The relationship between the average particle size and the distribution coefficient _Kd and the relationship between the solid component mass and the uniaxial compressive strength can be repeatedly used (S90 in FIG. 1). Therefore, it is possible to efficiently design the placement range.

Moreover, the design method of the placement range of the suspension type improvement material according to the embodiment of the present invention includes a plurality of suspension type improvement materials having different concentrations and a simulated ground formed from soil collected from the construction target ground. When a one-dimensional injection experiment is carried out, a plurality of simulated grounds may be formed using soil collected from a plurality of locations by changing the position and depth in the construction target ground. In this case, the one-dimensional injection experiment is performed a plurality of times while changing the combination of the formed simulated ground and the concentration of the suspension-type improving material. Then, for example, the distribution coefficient _Kd of the construction target ground is estimated from the relationship between the solid component mass after passing the simulated ground and the amount of drainage obtained from the experiment (S130 in FIG. 1). Furthermore, the subsequent uniaxial compression test will be performed using an improved body of the simulated ground formed from the soil collected from the construction target ground. Therefore, not only the distribution coefficient K _d, the delay coefficient R _d of calculating the distribution coefficient K _d, such relationship between the solid component mass and uniaxial compression strength, the parameters obtained from experiments with collected soil construction target ground using To calculate. For this reason, the difference between the design result and the construction result can be reduced, and the design can be performed more accurately.

Furthermore, the design method of the placement range of the suspension-type improvement material according to the embodiment of the present invention is set as a virtual shape in a range where the suspension-type improvement material penetrates into the ground, which is set when the advection dispersion equation is established. As shown in FIG. 2, a virtual shape 24 penetrating from one point in the ground G into a spherical shape having the one point as the center c may be set. Thereby, not only the set shape 24 is close to the shape of the improved body actually built in the ground G, but also the advection dispersion equation when the suspension-type improving material penetrates into the spherical shape is Thus, it can be expressed by a relatively simple expression including the radius r of the sphere as a parameter. For this reason, it is possible to perform calculation efficiently while achieving both design accuracy and rationality.
Moreover, when calculating | requiring the magnitude | size of the improvement body of a construction object ground, it is good also considering the predetermined intensity | strength which an improvement body should be provided as uniaxial compressive strength as 100 kPa generally required for the countermeasure against liquefaction. As a result, if the ground injection method is carried out using this design method, it is possible to secure at least a strength sufficient to suppress the liquefaction of the ground, so that the reliability of ground improvement can be further improved. It becomes possible.

Furthermore, in the method for designing the placement range of the suspension-type improving material according to the embodiment of the present invention, an ultrafine particle spherical silica-based improving material may be used as the suspension-type improving material to be injected into the ground. This ultrafine spherical silica-based improving material contains refined spherical silicon dioxide as a main material and calcium hydroxide as a curing agent. Further, spherical silicon dioxide has a particle size of, for example, Since it is about 1 μm, it penetrates into the ground relatively smoothly. Therefore, when the improved material is actually injected into the ground, the difference between the design result and the construction result due to the difficulty of penetration in the ground can be reduced.
In addition, the design method of the placement range of the suspension-type improvement material according to the embodiment of the present invention is not limited to the ground injection method for permanent installation such as countermeasures against liquefaction and seismic reinforcement, but for example, heaving and boarding in excavation work It can also be applied to ground injection methods for temporary use, such as anti-blurring measures and prevention of mirror breakage and face collapse during tunnel excavation.

  On the other hand, the ground injection method according to the embodiment of the present invention uses the above-described method for designing the placement range of the suspension-type improving material according to the embodiment of the present invention. That is, by satisfying the strength and size of the improved body required for the construction target ground, the size of the improved body with a predetermined strength or higher is determined by the design method of the placement range of the suspension type improved material. Ask. And according to the density | concentration and injection | pouring amount of a suspension type improvement material set in that case, a suspension type improvement material is actually inject | poured into a construction object ground. As a result, the work can be efficiently performed so as to satisfy the strength required for the construction target ground while exhibiting the same effects as the method for designing the placement range of the suspension-type improvement material according to the embodiment of the present invention described above. It is possible to proceed.

  G: Ground, 24: Virtual shape, 42: Improved body

Claims (7)

It is a design method of the placement range of suspension type improvement material that is injected into the ground to improve the ground,
Set a virtual shape in a range where the suspension-type improvement material penetrates into the ground, and include an adsorption amount of the suspension-type improvement material by soil particles of the ground as a parameter, and establish an advection dispersion equation corresponding to the virtual shape,
One-dimensional injection experiment using a plurality of suspension-type improving materials having different concentrations, a plurality of simulated grounds formed from samples having different average particle diameters, or a simulated ground formed from soil sampled from the construction target ground, and the primary The uniaxial compression test of the improved body formed in the original injection experiment was carried out. From these results, the distribution coefficient of the construction target ground, the mass of the solid component of the suspension-type improved material, and the uniaxial compressive strength of the improved body Seeking a relationship with
Calculating a delay coefficient from the distribution coefficient;
Using the delay coefficient and the concentration and injection amount of the suspension-type improving material as parameters, solving the advection dispersion equation, the predicted distribution of the solid component of the suspension-type improving material in the construction target ground Seeking
From the predicted distribution of the solid component, and the relationship between the mass of the solid component and the uniaxial compressive strength of the improved body, the predicted distribution of the uniaxial compressive strength in the construction target ground is obtained,
Based on the predicted distribution of the uniaxial compressive strength, the size of the improvement body of the construction target ground having a uniaxial compressive strength equal to or higher than a predetermined strength is obtained, and the design of the placement range of the suspension type improvement material is characterized. Method.   The one-dimensional injection experiment is performed using a plurality of suspension-type improving materials having different concentrations and a plurality of simulated grounds formed of samples having different average particle diameters, and the simulated ground is configured from the experimental results. The suspension type according to claim 1, wherein a relationship between an average particle diameter of the sample and a distribution coefficient is obtained, and a distribution coefficient of the ground to be constructed is estimated based on the relationship between the average particle diameter and the distribution coefficient. Design method for placement of improved material.   The one-dimensional injection experiment was carried out using a plurality of suspension-type improvement materials having different concentrations and a simulated ground formed from soil collected from the construction target ground. From this experimental result, the distribution coefficient of the construction target ground was calculated. The method for designing the placement range of the suspension-type improving material according to claim 1, wherein estimation is performed.   The virtual shape in which the suspension-type improving material penetrates from a single point in the ground into a sphere centered on the single point is set as a virtual shape when the advection dispersion equation is established. 4. A method for designing a placement range of the suspension-type improving material according to any one of 3 above.   The method for designing the placement range of the suspension-type improving material according to any one of claims 1 to 4, wherein the predetermined strength is 100 kPa.   6. The suspension-type improving material is an ultrafine particle spherical silica-based improving material containing spherical silicon dioxide as a main material and calcium hydroxide as a curing agent. A method for designing the placement range of the suspension-type improving material according to claim 1. The suspension type improvement material, which is determined based on the size of the improvement body of the construction target ground, which is obtained by the method for designing the placement range of the suspension type improvement material according to any one of claims 1 to 6. Injecting the suspension-type improving material into the construction target ground according to the concentration and the injection amount of the ground.

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