JP2021021309A - Determining method compounding specification of solidification material - Google Patents

Abstract

To provide a determining method for the compounding specification of a solidification material, which can determine the compounding specifications of the solidifying material, which can prevent the occurrence of a co-rotation phenomenon at high probability without significantly increasing the amount of the solidifying material used.SOLUTION: A determining method for the compounding specification of a solidification material for the soil to be improved in a deep mixing treatment method, comprises: a step of performing a vane shear test and determining a vane shear value τ for the unsolidification mixed soil in which the solidification material is mixed with the soil to be improved at a plurality of compounding levels and stirred, and determining a liquid dropping frequency N in the item of a liquid limit test: and the step of determining a target compounding specification of the solidification material based on the correlation between the vane shear value τ and the liquid dropping frequency N.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for determining a blending specification of a cement-based solidifying material slurry in a deep mixing treatment method.

In the deep mixing treatment method, while the stirring blade penetrates into the soil, a slurry-like solidifying material is mixed with the soil and stirred to form a consolidated columnar pile in the soil to support the soft ground. It is a construction method that increases the force. In the deep mixing treatment method, when the soil to be improved is highly plastic, or when the viscosity and shear strength are high, the soil adheres to the stirring blade and the stirring blade rotates together with the soil. May occur and the solidifying material may not mix well with the soil and the desired bearing capacity may not be obtained.

In order not to generate the co-rotation phenomenon, for example, Patent Document 1 discloses a deep mixing processor provided with co-rotation prevention blades. However, since the co-rotation phenomenon occurs underground, the manager on the ground cannot know whether or not the co-rotation phenomenon actually occurs during construction.

Therefore, for example, Patent Document 2 provides a count sensor that detects the relative rotation speed of the co-rotation prevention blade with respect to the rotation speed of the rotating rod, and compares the relative rotation speed of the co-rotation prevention blade with the rotation speed of the rotating rod. , A stirring / mixing device capable of detecting the occurrence of a co-rotation phenomenon during construction is disclosed.

However, even if the above-mentioned stirring / mixing device is used, the occurrence of the co-rotation phenomenon itself cannot be prevented. Therefore, from the stage of determining the compounding specifications of the solidifying material, the water solidifying material ratio W / C is set so that the properties of the mixed soil immediately after mixing the solidifying material do not cause the co-rotation phenomenon, and the mixed soil is mixed. It is conceivable to take measures to adjust the consistency.

For example, Patent Document 3 discloses that the consistency of the mixed soil immediately after mixing the solidifying material is adjusted at the stage of determining the compounding specifications. This is because in the so-called trencher method, the water solidifying material ratio W / C is adjusted on the premise that the improvement target strength is satisfied, and the consistency index Ic is preferably 0 in order to make the property that rolling compaction is not required after mixing and stirring. It is as follows.

When the consistency index Ic is 0 or less, it means that the natural water content ratio Wn is larger than the liquid limit WL, and the water content ratio of the mixed soil immediately after mixing the solidifying material exceeds the liquid limit WL. As a result, the properties of the mixed soil are fluid, no voids remain in the mixed soil even without compaction, and a solidified soil layer with few mixed spots can be created.

Japanese Unexamined Patent Publication No. 56-153013 JP-A-2000-144703 Japanese Unexamined Patent Publication No. 2003-239275

The above-mentioned Patent Document 3 describes that the mixing resistance is reduced by making the consistency index Ic smaller than 0. However, since the mixed soil exhibits remarkable fluidity in this way, the mixed soil is stirred. It is presumed that it becomes difficult to adhere to the blades and that the occurrence of the co-rotation phenomenon in the deep mixing treatment method can be eliminated.

In the deep mixing treatment method, the water solidifying material ratio W / C of the solidifying material slurry is usually set to about 0.8 to 1.2 (Revised version of the Deep Mixing Treatment Method Design and Construction Manual for Land Works). Public Works Research Center, March 2004, see page 60). However, in addition to this, if the condition that the consistency index Ic of the mixed soil immediately after mixing the solidifying material is 0 or less is added, the water content ratio Wn of the mixed soil immediately after mixing the solidifying material is made to exceed the liquidity limit WL. In particular, a large amount of water will be added to the highly plastic cohesive soil.

However, the addition of water increases the cost because it is necessary to increase the amount of the solidifying material used in order to satisfy the target strength. Further, at the construction site, since the amount of slurry injected into the ground increases, the amount of mud generated during construction increases, and it becomes necessary to dispose of the increased mud. Furthermore, since the amount of slurry injected into the ground increases, mud drainage increases during construction, the scaffolding of the construction machine tends to soften, and the stability of the construction machine may decrease.

The present invention has been made in view of such circumstances, and determines a compounding specification of a solidifying material capable of preventing the occurrence of a co-rotation phenomenon with a high probability without significantly increasing the amount of the solidifying material used. It is an object of the present invention to provide a method for determining a compounding specification of a solidifying material.

The method for determining the blending specifications of the solidifying material of the present invention is a method for determining the blending specifications of the solidifying material for the soil to be improved in the deep mixing treatment method, in which the solidifying material is mixed with the soil to be improved at a plurality of blending levels. A vane shear test is performed on the uncured mixed soil that has been stirred and the vane shear value is obtained, and the number of liquid drops in the items of the liquid limit test is obtained, and the vane shear value and the liquid property are obtained. It is characterized by including a step of determining a target compounding specification of the solidifying material based on a correlation with the number of drops.

As will be described later, the method for determining the blending specifications of the solidifying material of the present invention considers both the vane shear value and the consistency of the uncured mixed soil based on the correlation between the vane shear value and the number of liquid drops. However, determine the target compounding specifications of the solidifying material so that co-rotation does not occur. This makes it possible to determine the compounding specifications of the solidifying material at the limit where the co-rotation phenomenon does not occur, with higher accuracy than when judging only by the vane shear value. .. As a result, it is possible to suppress the addition of the solidifying material more than necessary, and it is possible to reduce the cost and the like, which is economical.

In the method for determining the compounding specifications of the solidifying material of the present invention, a representative point of a large curvature portion having a large curvature in the designated correlation curve showing the correlation between the vane shear value and the number of liquid drops is estimated and corresponds to the representative point. It is preferable that the compounding specification of the solidifying material is determined as the target compounding specification of the solidifying material.

In this case, as will be described later, it is possible to obtain with high accuracy the economical target compounding specifications of the solidifying material depending on whether or not the co-rotation phenomenon occurs.

In the method for determining the compounding specifications of the solidifying material of the present invention, for example, the plurality of compounding levels are such that the amount of the solidifying material added per unit volume of the soil to be improved is constant and the ratio of the water solidifying material is different. All you need is.

Further, in the method for determining the compounding specifications of the solidifying material of the present invention, for example, the water solidifying material ratio is constant at the plurality of compounding levels, and the amount of the solidifying material added per unit volume of the soil to be improved is different. It may be a thing. The compounding specifications are represented by the amount of the solidifying material added per unit volume of the soil to be improved and the ratio of the water solidifying material.

Further, in the method for determining the compounding specifications of the solidifying material of the present invention, the number of liquid drops corresponding to the compounding specifications of the solidifying material obtained based on the target strength of the solidified mixed soil is the number of first designated liquid drops. The step of determining N0 and the solidification obtained based on the target strength when the first designated liquid drop count N0 is the second designated liquid drop count N1 or less, which is the number of liquid drops corresponding to the representative point. When the compounding specification of the material is determined as the target compounding specification of the solidifying material and the first designated liquid drop count N0 exceeds the second designated liquid drop count N1, the solidifying material corresponding to the representative point is blended. It is preferable to include a step of determining the specifications as the target compounding specifications of the solidifying material.

In this case, it is possible to add the solidifying material so that the solidified mixed soil has the target strength and the target blending specifications of the solidifying material are less likely to cause the co-rotation phenomenon.

Further, in the method for determining the blending specifications of the solidifying material of the present invention, the vane is used in a step of performing a uniaxial compression test on the solidified mixed soil to obtain a uniaxial compression strength and in a section of a plurality of liquid drops. It is provided with a step of obtaining the section in which the decrease in the uniaxial compressive strength is the smallest with respect to the decrease in the shear value, and a step of correcting the target compounding specification of the solidifying material based on the minimum value of the number of liquid drops in the obtained section. Is preferable.

In this case, it is possible to determine the target compounding specifications of the solidifying material, which satisfies the uniaxial compressive strength of the solidified mixed soil and at the same time greatly reduces the possibility of the co-rotation phenomenon occurring.

The graph which shows the relationship between the vane shear value and the number of liquid drops in Example 1. FIG. The graph which shows the relationship between the vane shear value and the number of liquid drops in Example 2. FIG. The graph which shows the relationship between the uniaxial compression strength and the addition amount of a solidifying material in Example 3. FIG. It is a graph which shows the relationship between the vane shear value and the number of liquid drops in Example 3, and shows the case where the uniaxial compression strength qu is 500 kN / m ² . It is a graph which shows the relationship between the vane shear value and the number of liquid drops in Example 3, and shows the case where the uniaxial compression strength qu is 400 kN / m ² . The graph which shows the relationship between the vane shear value and the uniaxial compressive strength in Example 4 and the number of liquid drops.

The inventor of the present application has tested and investigated the presence or absence of the co-rotation phenomenon at a large number of construction sites using the deep mixing treatment method. This test and survey include a test to confirm the relationship between the compounding specifications of the solidifying material and the occurrence of the co-rotation phenomenon during construction, and the properties of the mixed soil in which the co-rotation phenomenon has occurred.

Initially, the inventor of the present application considered through the above-mentioned tests and investigations to adopt the vane shear value τ as a judgment index regarding the presence or absence of the co-rotation phenomenon at the time of construction of the unsolidified mixed soil immediately after the solidifying material is mixed. This is a method using a vane shear tester and using the shear strength of the mixed soil as an index. The vane shear test is a test in which a rod with cross-shaped blades (vanes) is pushed into the ground and rotated, and the shear resistance (adhesive force) along the cylindrical shear surface formed by the blades is obtained from the rotational resistance. It has many advantages such as being able to be performed on unsolidified soil during an indoor compounding test, the test results being immediately revealed immediately after the test is performed, and being considered to be highly related to the on-site co-rotation phenomenon. Because.

When the vane shear value τ exceeds 6 kN / m ² , the co-rotation phenomenon is likely to occur, and when the vane shear value τ is 5 to 6 kN / m ² , the co-rotation phenomenon may occur. I found that there was not a little.

The vane shear test for obtaining the vane shear value τ in the embodiment of the present invention is based on the Japanese Geotechnical Society standard JGS1411-2012 "Direct Shear Test", and this test is performed indoors for "stable treatment". Examples of "5.3.3. Specimen preparation equipment and curing equipment (1) Mixing equipment" based on "Preparation of specimen without soil compaction" and "Stable treatment method for preparation of specimen by compaction of soil (JGS0811-2009)" Weigh the sample soil into a stainless steel ball attached to an electric mixer that has the same function as the above, and weigh-add-mix and stir the solidifying material so that the specified amount of solidified material is mixed. On the other hand, it refers to a test carried out using a small vane shear tester used for the "in-situ vane shear test".

However, if there is a possibility that a co-rotation phenomenon may occur due to the vane shear test, in order to suppress this, a construction method in which the amount of solidifying material slurry is increased, the ratio of water solidifying material is increased, and water is discharged by pre-drilling. It is necessary to reduce the viscosity of the mixed soil immediately after mixing the solidifying material, such as by adopting the above and mixing the thickening material into the solidifying material. And these are all factors that increase the cost, which is not preferable from the economical point of view.

Furthermore, at the actual construction site, even if the vane shear value τ of the mixed soil immediately after mixing the solidifying material exceeds 6 kN / m ² , the co-rotation phenomenon may not occur, and the vane shear value τ is less than 5 kN / m ^2. Even so, the co-rotation phenomenon sometimes occurred.

Therefore, the inventor of the present application determines only the vane shear value τ regarding the mechanical properties of the mixed soil so that the presence or absence of the co-rotation phenomenon at the construction site can be more reliably estimated at the stage of determining the compounding specifications. Instead, I came up with the idea of adding consistency, which is an index related to the physical characteristics of the mixed soil immediately after mixing the solidifying material, to the judgment index.

For this purpose, a liquid drop count test is adopted to obtain the liquid drop count N in the liquid limit test items specified in JIS A 1205: 2009 "Soil liquid limit / plastic limit test method". did. This is done by putting the mixed soil immediately after mixing the solidifying material into a brass dish using a spatula so that the maximum thickness is about 1 cm, shaping it, cutting a groove along the diameter of the brass dish, and using this as a drop tester. The number of drops in which the mixed soil at the bottom of the grooved portion of the brass dish merges by 1.5 cm is calculated as the number of liquid drops N by lifting and dropping the brass dish twice per second. This liquid drop frequency test was performed together with the vane shear test, and an index for determining the presence or absence of the co-rotation phenomenon was found based on the correlation between the vane shear value τ and the liquid drop frequency N.

In the present invention, the liquid limit test is not limited to the above. For example, the Japanese Geotechnical Society standard JGS 0142-2009 "Soil liquid limit test method using fall cone" is applied mutatis mutandis, and the intrusion amount of fall cone is associated with the value corresponding to the number of liquid fall N of mixed soil. You may use it. In addition, a test similar to the liquid limit test specified in JIS and JGS may be used to obtain the above-mentioned number of liquid drops N or a similar test.

Hereinafter, examples of this new determination index will be described.

In Example 1, as the soil to be improved, a cohesive soil having a wet density ρt of 1.65 g / cm ³ and a water content Wn of 62.7% was used. As the solidifying material, cement-based solidifying material Geoset 200 (manufactured by Taiheiyo Cement Co., Ltd.) is used as a slurry, and the water solidifying material ratio W / C is 0.8, 0.9, 1.0, 1.2, 1.5. , 2.0, 2.5, and the amount of solidifying material added was 320 kg / m ³ . A vane shear test and a liquid drop frequency test were performed on the mixed sample soil having a water solidifying material ratio of W / C for these seven types. The results are shown in Table 1.

In FIG. 1, a plot showing each of a plurality of experimental results is shown, with the vane shear value τ on the vertical axis and the number of liquid drops N on the horizontal axis. The numbers next to each plot represent the water solidified material ratio W / C. In FIG. 1, a designated correlation curve defined as an approximate curve based on a plurality of plots representing a plurality of experimental results is shown by a solid line in the N-τ plane. N is a positive integer, but when N is regarded as a continuous variable, the designated correlation curve has a domain defined as a concave function, and is defined as a quadratic differentiable curve by N in the domain. Is preferable. The concave function f (x) has an inequality f ((1-α) x1 + αx2) ≧ (1-α) f (x1) + αf (x2) for any x = x1 and x = x2 (≠ x1) in its domain. ) (0 ≤ α ≤ 1) means a function that holds the relationship.

The designated correlation curve is defined as, for example, a polynomial approximation curve of degree 2 or higher based on the plurality of plots, an exponential approximation curve, a logarithmic approximation curve and a power approximation curve, and an arbitrary combination (weighted sum) thereof. For example, the weighted sum of the polynomial approximation curve f1 and the exponential approximation curve f2 is expressed as γf1 + (1-γ) f2 using the weighting coefficient γ (0 <γ <1). Part or all of the designated correlation curve may be defined by an interpolated curve such as a Bezier curve or a B-spline curve, with each of the plurality of plots as a control point.

From the graph of FIG. 1, the number of liquid drops N corresponding to the vane shear value τ of 6 kN / m ² is about 33, and the number of liquid drops N corresponding to the vane shear value τ of 5 kN / m ² is 28. The vane shear value τ corresponding to 25 times, which is about 25 times and the water content ratio Wn of the mixed soil immediately after mixing the solidifying material is the liquid limit WL (Wn = WL), is 4. It was found to be about ² kN / m ² .

From this, if limited to the purpose of preventing the occurrence of the co-rotation phenomenon, considering that the number of liquid drops N corresponding to the vane shear value τ of 6 kN / m ² is about 33 times, at least immediately after mixing the solidifying material. The number of liquid drops N of the mixed soil is 25 times, which corresponds to the liquid limit (or the water solidifying material ratio W / C is 1.2 to 1.5 (about 1.3), which corresponds to the liquid limit). It is considered unnecessary to do so.

Then, the inventor of the present application noted that in the designated correlation curve in the graph of FIG. 1, there is a large curvature portion Q having a larger curvature than the portion close to the straight line on both sides.

The large curvature portion Q having a large curvature means a portion in which a portion having a large curvature as compared with other portions is continuous by a certain length or more. A representative point (hereinafter referred to as a sharp turning point) P exists in the large curvature portion Q. The sharp curve point P may be, for example, an intermediate point of the length of the large curvature portion Q or an intersection of tangents at both ends of the large curvature portion Q of the curve located on both outer sides of the large curvature portion Q. Further, the point where the designated correlation curve shows the maximum curvature may be defined as the sharp turning point P. When the designated correlation curve is defined by the dependent variable (function) τ = f (N) whose principal variable is the continuous variable N (N is actually a positive integer as described above), then N = a. The curvature κ is expressed by the relational expression (01).

κ = (d ² f / dN ² ) | _{N = a} / {1+ (df / dN) ² | _{N = a} } ^3/2 ‥ (01).

Returning to FIG. 1, the sharp turning point P exists at a position where the second designated liquid drop count N1 is around 35 times, and the value of the second designated liquid fall count N1 is a vane shear value τ of 6 kN / m. It is a value slightly larger than 33 times, which corresponds to the number of liquid drops N corresponding to ² . This is because, as described above, if the vane shear value τ is 6 kN / m ² or more, the co-rotation phenomenon is likely to occur. Therefore, by paying attention to the sharp turning point P, the presence or absence of the co-rotation phenomenon occurs. The inventor of the present application inferred that it could be a judgment index for estimating.

Therefore, the water-solidifying material ratio W / C corresponding to the sharp turning point P and the liquid drop number N corresponding to 35 times is set, and the liquid drop number N corresponding to the liquid drop number N is 35 times and the liquid fall number N is 30 times. With reference to (water solidified material ratio W / C is 1.2) and 37 times (water solidified material ratio W / C is 1.0), proportional distribution was performed and calculated as the following formula. The water-solidifying material ratio W / C thus obtained corresponds to the target compounding specification of the solidifying material of the present invention.

W / C = 1.0 + (1.2-1.0) × (37-35) / (37-30) = 1.1 ... (02).

Rounding of the calculated values of W / C (water solidified material ratio), number of liquid drops and solidified material addition amount is usually the design standard strength (q _ul ) when setting the indoor target strength (q _ul ) in the indoor compounding test. _Since the surcharge for ( _uck ) (for example, q _ul = (3-4) q _uck ) is taken into consideration, it is rounded off.

Then, when the water solidifying material ratio W / C was set to 1.1, the co-rotation phenomenon did not occur. From this, it is better to use the sharp curve point P in the designated correlation curve showing the relationship between the vane shear value τ and the number of liquid drops N as a judgment index for the presence or absence of the co-rotation phenomenon, so that the vane shear value τ is 6 kN / m. It is economically preferable to the case where the number of liquid drops N, which is an index corresponding to ² , is 33 times.

Although the basis for clearly showing the relationship between the sharp turning point P and the presence or absence of the co-rotation phenomenon is not clear, the sharp turning point P is the presence or absence of soil adhering to the stirring blade or the like, or the adhesive force is large. It is inferred that this is an index that indicates the boundary of increase and decrease. In addition, when tests were conducted on various soils to be improved, it was found that such a sharp turning point P generally exists regardless of whether or not it clearly appears.

Then, in the same manner as in the above-described embodiment, when test construction and site confirmation were performed on various soils to be improved, the sharp turning point P is very effective as an index indicating the presence or absence of the co-rotation phenomenon. It turned out. That is, if the compounding specifications of the solidifying material are determined using the sharp bending point P as an index, the water solidifying material ratio W / C that does not cause the co-rotation phenomenon is obtained as compared with the case where only the vane shear value τ is used as an index. It has become possible to estimate with higher accuracy.

If safety is taken with respect to the compounding specifications of the solidifying material corresponding to the sharp bending point P, it is possible to suppress the occurrence of the co-rotation phenomenon with a higher probability. For example, the compounding specifications of the solidifying material may be determined based on the number of liquid drops N, which is obtained by reducing a predetermined number, for example, 1 to 3, from the second designated number of liquid drops N1 corresponding to the sharp bending point P. Conceivable.

For example, in Example 2, the soil to be improved was humus soil, the wet density ρt was 1.276 g / cm ³ , and the water content Wn was 154.1%. As the solidifying material, cement-based solidifying material Geoset 225 (manufactured by Taiheiyo Cement Co., Ltd.) is used as a slurry, the water solidifying material ratio W / C is 1.0, and the addition amounts are 100 kg / m ³ and 200 kg / m. ^{At 3} , 300 kg / m ³ , a liquid drop frequency test and a vane shear test were performed at these blending levels. The graph of FIG. 2 shows the test results with the vane shear value τ on the vertical axis and the number of liquid drops N on the horizontal axis. The black circles represent the results of each experiment, and the numbers next to them represent the amount added. The results are shown in Table 2.

In the graph of FIG. 2, there is no clear sharp turning point P as seen in the graph of FIG. 1, but if the point where the curvature is considered to be the maximum is considered as the sharp turning point P, it corresponds to this sharp turning point P. The number of second designated liquid drops N1 is about 38 times. The second designated number of liquid drops N1 is smaller than about 55 times, which is the number of liquid drops N corresponding to the vane shear value τ of 6.0 kN / m ² , but the number of liquid drops corresponding to the liquid limit WL. Greater than 25 times, which is NL.

In this case, according to the above-mentioned standard that the vane shear value τ is 6 kN / m ² , the co-rotation can be prevented by the addition amount of the solidifying material corresponding to the liquid drop frequency N of 55 times or less. However, when the number of liquid drops N is 55, the properties of the sample soil are far from the liquid limit and are not in a fluid state, so it is considered that there is a high possibility that co-rotation will occur. In order to eliminate the possibility of co-rotation, it is necessary to increase the amount of water or solidifying material until the vane shear value τ corresponding to 25 liquid drops N is about 4.2 kN / m ^2. Conceivable.

Then, the amount of the solidifying material added corresponding to the second designated liquid drop number N1 is 38 times, and the liquid drop number N close to the top and bottom of 38 times is 18 times (addition amount is 300 kg /). With reference to m ³ ) and 39 times (addition amount is 200 kg / m ³ ), proportional distribution was performed, and the formula was calculated as follows. The amount of addition thus obtained corresponds to the target compounding specification of the solidifying material of the present invention.

Addition amount = 200+ (300-200) × (39-38) / (39-18) = 205 ... (03).

Then, when the amount of the solidifying material added was set to 205 kg / m ³ , the co-rotation phenomenon did not occur. As described above, according to the present invention, it is possible to obtain an appropriate compounding specification of the solidifying material by performing a vane shear test and a liquid drop frequency test at at least three compounding levels.

If the sharp turning point P is not clear as shown in the curve of FIG. 2, a co-rotation phenomenon will occur with a high probability if a little greater safety is seen with respect to the compounding specifications of the solidifying material corresponding to the sharp turning point P. Can be suppressed. In actual construction, it is important to meet the strength target of the improved soil. Therefore, a method of determining the compounding specifications of the solidifying material so that the co-rotation phenomenon does not occur while satisfying such a strength target will be described below by taking Example 3 as an example.

In Example 3, the soil to be improved was cohesive soil, the wet density ρt was 1.488 g / cm ³ , and the water content Wn was 84.7%. Indoor target uniaxial compressive strength qu modified soil was 400 kN / m ² and 500 kN / m ^2. As the solidifying material, cement-based solidifying material Geoset 200 (manufactured by Taiheiyo Cement Co., Ltd.) was used as a slurry.

The water solidification material ratio W / C is set to 1.0, and the addition amounts are 100 kg / m ³ , 130 kg / m ³ , 160 kg / m ³ , 190 kg / m ^3, and first, a normal test is performed at these compounding levels. The uniaxial compression test of the improved soil was carried out according to the above. The results are shown in Table 3.

In the graph of FIG. 3, the vertical axis represents the uniaxial compressive strength, and the horizontal axis represents the amount of the solidifying material added, respectively. From this graph, the amount of the solidifying material added when the indoor target uniaxial compressive strength qu of the improved soil is 400 kN / m ² is 123 kg / m ³ , and the solidifying material when the uniaxial compressive strength qua is 500 kN / m ^2. It can be seen that the addition amount of is 137 kg / m ³ .

Next, a liquid drop frequency test and a vane shear test were performed at the compounding level of the solidifying material. The results are shown in Table 4.

Similar to FIGS. 1 and 2, the graph of FIG. 4 was created. From this graph, it can be seen that the number of second designated liquid drops N1 corresponding to the sharp turning point P is about 35 times.

When the uniaxial compressive strength qu is 500 kN / m ² , the amount of the solidifying material added corresponds to 137 kg / m ^3, and the number of first designated liquid drops N0 is the amount of addition close to the top and bottom of 137 kg / m ³ . Is 130 kg / m ³ (the number of liquid drops N is 36 times) and the amount added is 160 kg / m ³ (the number of liquid drops N is 23 times), and is proportionally distributed and calculated by the following formula. It was.

N0 = 23+ (160-137) × (36-23) / (160-130) = 33 (04).

From this, 33 times, which is the first designated liquid drop number N0 corresponding to the uniaxial compression strength qu of 500 kN / m ² , is smaller than 35 times of the second designated liquid drop number N1 corresponding to the sharp turning point P. By setting the compounding specification of the solidifying material to 137 kg / m ³ which is an addition amount corresponding to a uniaxial compressive strength qu of 500 kN / m ² , it is possible to eliminate the occurrence of the co-rotation phenomenon with a very high probability. The amount of addition thus obtained corresponds to the target compounding specification of the solidifying material of the present invention.

On the other hand, referring to FIG. 5, when the uniaxial compressive strength qu is 400 kN / m ² , the addition amount of the solidifying material is 123 kg / m ^3, and the addition amount of the first designated liquid drop frequency N0 corresponds to 123 kg / m ^3. Proportionate distribution with reference to the addition amount of 100 kg / m ³ (the number of liquid drops N is 67 times) and the addition amount of 130 kg / m ³ (the number of liquid drops N is 36 times) that are close to the top and bottom of m ^3. Then, it was calculated as the following formula.

N0 = 36+ (130-123) × (67-36) / (130-100) = 43 ... (05).

From this, 43 times, which is the first designated liquid drop number N0 corresponding to the uniaxial compression strength qu of 400 kN / m ² , is larger than 35 times, which is the second designated liquid drop number N1 corresponding to the sharp turning point P. Therefore, if the compounding specification of the solidifying material corresponding to the first designated liquid drop frequency N0, that is, the addition amount is 123 kg / m ³ , the probability that the co-rotation phenomenon occurs is high. Therefore, it is necessary to change the amount of the solidifying material added so as to correspond to the second designated liquid drop frequency N1 corresponding to the sharp bending point P. If N at the sharp turning point P where the designated correlation curve shows the maximum curvature (N when regarded as a continuous variable as described above) is smaller than N0 and is not an integer, the liquid property with the decimal point truncated. The amount of the solidifying material added may be determined so as to correspond to the number of drops. For example, when N at the sharp turning point P is "34.9" smaller than N0 (= 43), the amount of the solidifying material added is determined so as to correspond to the number of liquid drops "34" with the decimal point truncated. May be done.

This addition amount may be obtained in the same manner as in Example 2. Specifically, the amount of the solidifying material added corresponding to the second designated number of liquid drops N1 is 35, and the number of liquid drops N close to the top and bottom of 35 times is 23 (addition amount). Was calculated as the following formula by proportional distribution with reference to 160 kg / m ³ ) and 36 times (addition amount was 130 kg / m ³ ).

Addition amount = 130+ (160-130) × (36-35) / (36-23) = 132 ... (06).

From this, by setting the addition amount of the solidifying material to 132 kg / m ³ , the uniaxial compressive strength qu is 400 kN / m ² or more, and the occurrence of the co-rotation phenomenon can be eliminated with a very high probability. The amount of addition thus obtained corresponds to the target compounding specification of the solidifying material of the present invention.

Furthermore, the inventor also examined the relationship between the vane shear value τ and the number of liquid drops N and the uniaxial compressive strength qu.

For example, in Example 4, the soil to be improved was cohesive soil, the wet density ρt was 1.65 g / cm ³ , and the water content Wn was 62.7%. As the solidifying material, cement-based solidifying material Geoset 200 (manufactured by Taiheiyo Cement Co., Ltd.) is used as a slurry, and the water solidifying material ratio W / C is 0.8, 0.9, 1.0, 1.2, 1.5. , 2.0, 2.5, and the amount of solidifying material added was 320 kg / m ^3, and a liquid drop frequency test, a vane shear test, and a uniaxial compression test at a material age of 28 days were performed at these blending levels. It was.

In the graph of FIG. 6, the vertical axis represents the vane shear value τ and the 28-day-old uniaxial compression strength qu, and the horizontal axis represents the number of liquid drops N, respectively. The relationship between the vane shear value τ and the number of liquid drops N is shown by a solid line, and the relationship between the uniaxial compressive strength qu and the number of liquid drops N is shown by a dotted line. The results are shown in Table 5.

From the graph of FIG. 6, it can be seen that both the vane shear value τ and the uniaxial compression strength qu decrease as the number of liquid drops N decreases. However, the reduction rate of the vane shear value τ and the reduction rate of the uniaxial compression strength qu are different in the section where the number of liquid drops N is N. Especially in the section A, the decrease rate of the uniaxial compressive strength qu is smaller than the decrease rate of the vane shear value τ. From this, it is considered that the section A is a section related to the number of liquid drops N such that the uniaxial compressive strength is maintained to some extent, although the possibility that the co-rotation phenomenon occurs is greatly reduced.

Therefore, when such a section A exists, the target compounding specification of the solidifying material obtained in the above-described embodiment is corrected in consideration of the compounding specification at the liquid drop frequency N, which is the lower limit of the section A. Is preferable.

As a specific method for correcting the target compounding specifications of the solidifying material, for example, the minimum number of liquid drops N _min in the section A is obtained, and the amount of the solidifying material added in the work is such that the number of liquid drops N is (N _min + α). The value corresponds to the number of times. It is necessary to confirm that the added amount after correction is an addition amount that satisfies the indoor target uniaxial compression strength. For example, the range of α in the implementation work is about 1 to 3.

A specific method for obtaining the amount of the solidifying material added will be described with reference to FIG. In Example 4 of FIG. 6, the amount of the solidifying material added is constant at 320 kg / m ³ . From FIG. 6, N _min is 30 times, and if α is 3, (N _min + α) is 33 times. From this, from the water solidifying material ratio W / C when the number of liquid drops N is close to 33 times and the number of liquid drops N is 30 and 37 times, the modified water solidification corresponding to the number of liquid drops N is 33 times. The material ratio W / C _mod can be obtained as follows.

W / C _mod = 1.0 + (1.2-1.0) x (37-33) / (37-30) = 1.1 ... (07).

Although the embodiments of the present invention have been described above based on the examples, the present invention is not limited to the above-described embodiments.

For example, in the above-described embodiment, as shown in FIGS. 1, 2, 4, and 5, a sharp turning point in a graph in which the vertical axis is the vane shear value τ and the horizontal axis is the number of liquid drops N, respectively. The method of determining the compounding specifications of the solidifying material using P as an index has been described. However, the method for determining the compounding specifications of the solidifying material is not limited to this.

Specifically, for example, an inflection point P in a designated correlation curve in which the logarithmic value or exponentiation value of the vane shear value τ is taken on one axis and the logarithmic value or exponentiation value of the number of liquid drops N is taken on the other axis. Alternatively, the inflection point may be used as an index. Further, a value indicating the relationship between the vane shear value τ and the number of liquid drops N, for example, τ / N or logN / τ, is taken on one axis, and a value indicating the compounding level of the solidifying material is taken on the other axis, for example, water. The sharp bending point P or the inflection point in the graph in which the solidifying material ratio W / C or the blending amount is taken may be used as an index.

Further, the method for determining the curve and the sharp turning point P in these graphs may be limited to any known technique. However, for example, in the case of a graph in which the vane shear value τ is on the vertical axis and the number of liquid drops N is on the horizontal axis, the number of liquid drops N is as shown in FIGS. 1, 2, 4 and 5. In a small region, for example, 25 times or less, it is a substantially straight line having a positive inclination within a certain range or a curve (concave curve) that bulges slightly upward, and a region in which the number of liquid drops N is large, for example, 40 times or less. Then, a curve having a positive inclination in a certain range but having a smaller inclination than the inclination in the above-mentioned liquid fall frequency N becomes a substantially straight line or a curve bulging slightly upward, and between these regions. There is a high possibility that the large curvature portion Q and thus the sharp curve point P exists. Therefore, it is preferable to determine the curve and the sharp turning point P on the premise of such a matter.

Further, when such a curve and a sharp bending point P cannot be obtained, it is preferable to improve the accuracy by performing an experiment by adding a blending level of a solidifying material.

In the present invention, a vane shear test and a liquid drop frequency test are performed on the unsolidified mixed soil immediately after the solidifying material is added. Here, the unsolidified mixed soil immediately after adding the solidifying material means a mixed soil within a few minutes, for example, about 1 to 3 minutes after the solidifying material is added and stirring is completed. In the liquid drop frequency test, the mixed soil that has not been solidified on the brass sample can be shaped into the predetermined shape specified in JIS A1205: 2009 "Soil liquid limit / plastic limit test method", and for the vane shear test. It is necessary to maintain the properties of the sample soil in a stainless steel ball from weighing to smoothing. However, this time differs depending on the solidifying material, the type of soil to be improved, and the like.

When the W / C, the amount of the solidifying material added, and the like are corrected and calculated, they may be numerically processed in two cases. (Case 1) is a case related to design performance items such as whether or not the numerical value related to the numerical processing satisfies the target strength (uniaxial compressive strength, etc.). (Case 2) is a case where the numerical values related to the numerical processing are not directly related to the design performance items such as workability (whether or not they rotate together), on-site construction efficiency, and workability.

In (Case 1), in principle, if a fraction is found, the fraction is rounded (for example, W / C is rounded down and the addition amount is rounded up) so as to be on the safe side from an engineering point of view. The reason is that if the obtained numerical value is rounded down, the numerical value may not be sufficient to satisfy the target strength. For example, when computationally amount of 137.12kg / m ^3, if 137kg / m ³ and truncated, so that the computationally less than the amount that satisfies the target intensity by 0.12 kg / m ³ .. Therefore, in this case, the calculated value is rounded up to 138 kg / m ³ as the construction specification.

In (Case 2), in principle, rounding is performed when a fraction is found. The reason is that in the case of numerical values related to workability, even if the fraction is rounded down, the rounded down part does not directly contribute to the design performance, and if it is about the fraction, it is often more appropriate to prioritize economic efficiency. This is because it is considered.

Of course, the above principle should not be applied mechanically, and it is appropriate to determine whether the numerical processing is related to design performance as in (Case 1) or workability as in (Case 2). Judging, it is considered that each decision should be made while considering the safety side if it corresponds to (Case 1) and considering the economic efficiency if it corresponds to (Case 2).

The example shown in FIG. 1 is an example in which the W / C changes when the addition amount is constant (320 kg / m ³ ). In this case, since the direction in which the W / C increases is the direction in which the intensity development decreases, the fraction may be rounded down and W / C = 1.0 may be determined according to the above (case 1) concept (case 1). (See formula (02)).

The example shown in FIG. 2 is a case where the W / C is constant and the amount of the solidifying material added is changed, and rounding down the fraction of the amount of the solidifying material added may not satisfy the target strength. Therefore, according to the idea of the above (case 1), the fraction may be rounded up and the solidifying material addition amount may be determined to be 205 kg / m ³ (see calculation formula (03)).
The example shown in FIG. 4 is the case where the W / C is constant and the amount of the solidifying material added is changed as in the example shown in FIG. 2, but the number of liquid drops is rather designed. It is a numerical value that is not directly related to performance items, and may be rounded off to N0 = 33 according to the concept of (Case 2) above (see formula (05)).

Since the example shown in FIG. 5 is the case where the W / C is constant and the amount of the solidifying material added is changed as in the example shown in FIG. 4, the number of liquid drops is rather designed. It is a numerical value that is not directly related to the performance item, and may be rounded off to N0 = 43 according to the concept of (Case 2) above (see formula (06)). In the example shown in FIG. 5, the processing is related to the fraction of the addition amount, but the target strength corresponds to the sharp turning point P for the purpose of preventing co-rotation on the premise that the addition of only 123 kg / m ³ is already satisfactory. Since this is a fractional process in the calculation for determining the amount to be added, the amount of the solidifying material added may be determined to be 132 kg / m ³ by rounding off the fractions according to the concept of (Case 2) above (see formula (07)).

The example shown in FIG. 6 is an example in which the W / C changes when the addition amount is constant (320 kg / m ³ ), as in the example shown in FIG. 1, and the direction in which the W / C increases is Since the expression intensity tends to decrease, the fraction may be rounded down and W / C = 1.1 may be determined according to the concept of (Case 1) above (see formula (08)).

The method for determining the compounding specifications of the solidifying material of the present invention is a method for determining the compounding specifications of the solidifying material for the soil to be improved in the deep mixing treatment method, in which the solidifying material is mixed with the soil to be improved at a plurality of compounding levels. A vane shear test is performed on the uncured mixed soil that has been stirred and the vane shear value is obtained, and the number of liquid drops in the items of the liquid limit test is obtained, and the vane shear value and the liquid property are obtained. The step of determining the target compounding specification of the solidifying material based on the correlation with the number of drops is provided , and the step of determining the vane shear value and the number of liquid drops are taken on the vertical and horizontal axes. It is characterized in that it is a step of determining the compounding specification of the solidifying material corresponding to the sharp curve point in the designated correlation curve defined at the time of plotting as the target compounding specification of the solidifying material .

Further, in the method for determining the compounding specifications of the solidifying material of the present invention, the number of liquid drops corresponding to the compounding specifications of the solidifying material obtained based on the target strength of the solidified mixed soil is the number of first designated liquid drops. The step of determining N0 and the case where the first designated liquid drop count N0 is the second designated liquid drop count N1 or less, which is the number of liquid drops corresponding to the sharp turning point , the above is obtained based on the target strength. When the compounding specification of the solidifying material is determined as the target compounding specification of the solidifying material and the first designated liquid drop count N0 exceeds the second designated liquid drop count N1, the solidifying material corresponding to the sharp bending point. It is preferable to include a step of determining the compounding specification of the above as the target compounding specification of the solidifying material.

Claims (6)

It is a method of determining the compounding specifications of the solidifying material for the soil to be improved in the deep mixing treatment method.
A vane shear test is performed on the unsolidified mixed soil in which the solidifying material is mixed with the soil to be improved at a plurality of compounding levels and stirred to obtain the vane shear value, and the liquid in the liquid limit test item. The process of determining the number of sex drops and
A method for determining a solidifying material compounding specification, which comprises a step of determining a target compounding specification of the solidifying material based on a correlation between the vane shear value and the number of liquid drops. A representative point of a large curvature portion having a large curvature in a designated correlation curve showing a correlation between the vane shear value and the number of liquid drops is estimated, and the compounding specifications of the solidifying material corresponding to the representative point are set to the solidifying material. The method for determining a compounding specification of a solidifying material according to claim 1, wherein the compounding specification is determined as a target compounding specification. The plurality of compounding levels according to claim 1 or 2, wherein the amount of the solidifying material added per unit volume of the soil to be improved is constant, and the ratio of the water solidifying material is different. Method for determining the compounding specifications of the solidifying material. The plurality of blending levels according to claim 1 or 2, wherein the ratio of the water solidifying material is constant, and the amount of the solidifying material added per unit volume of the soil to be improved is different. Method for determining the compounding specifications of the solidifying material. A step of determining the first designated liquid drop number N0, which is the number of liquid drops corresponding to the compounding specifications of the solidifying material obtained based on the target strength of the solidified mixed soil, and
When the first designated liquid drop count N0 is the number of liquid drops corresponding to the representative point N1 or less, the compounding specifications of the solidifying material obtained based on the target strength are solidified. When the target compounding specification of the material is determined and the first designated liquid drop count N0 exceeds the second designated liquid drop count N1, the compounding specification of the solidifying material corresponding to the representative point is the target of the solidifying material. The method for determining a compounding specification of a solidifying material according to any one of claims 1 to 4, further comprising a step of determining the compounding specification. A step of performing a uniaxial compression test on the solidified mixed soil to obtain a uniaxial compressive strength, and
A step of obtaining a section in which the reduction rate of the uniaxial compressive strength is the smallest with respect to the reduction rate of the vane shear value in a plurality of sections of the liquid drop times.
The solidifying material according to any one of claims 1 to 5, further comprising a step of correcting a target compounding specification of the solidifying material based on the minimum value of the number of liquid drops in the obtained section. Formulation specification determination method.