JP2012246659A - Ground improvement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground improvement method which enables improving construction efficiency while securing construction quality.SOLUTION: In an inventive ground improvement method, a rod 3 equipped with an agitation blade 2 is penetrated into the ground to a predetermined depth being rotated without a ground improvement material injected, and the rod is pulled out being rotated while the ground improvement material is injected from the rod and the ground is agitated/mixed by the agitation blade 2. An adjustment blade cutting frequency is obtained by reckoning a blade cutting frequency of the agitation blade in inserting the rod without injecting the ground improvement material into a blade cutting frequency of the agitation blade in pulling out the rod while injecting the ground improvement material. The adjustment blade cutting frequency is set on the basis of a target variation coefficient of soil improvement body intensity from a relationship between a preset variation coefficient of soil improvement body intensity and the adjustment blade cutting frequency, and ground improvement is performed with the set adjustment blade cutting frequency as a construction management item.

Description

  The present invention relates to a ground improvement method for improving a soft ground and creating a solid body such as a block shape, a wall shape, a lattice shape, a pile shape, or a layered shape and an improved ground in the ground.

  As is well known, solidifying materials such as lime and cement are prepared in a slurry state, and these slurries are stirred and mixed with the soil in the ground, so that the hydration reaction of the solidifying material slurry and the hydration by this hydration reaction are performed. The soil is improved by chemically solidifying the soil using an ion exchange action between the product and clay mineral, or a chemical consolidation reaction mainly composed of a pozzolanic reaction, and creating an improved pile in the ground. There is a ground improvement method for producing a solidified body (see, for example, Patent Document 1).

  In such a ground improvement method, a ground improvement device (processing machine) 1 and a construction management system based on a pile driving machine as shown in FIG. 6 are used. The processing machine 1 vertically supports a screw rod 3 having a stirring blade 2 at the tip by a base machine 4 and rotates the screw rod 3 by a driving device 5 to penetrate to the deepest part in the range to be improved. Pulling out the screw rod 3 while injecting cement slurry as a ground improvement material into the ground from the discharge port provided at the tip of the rod 3 and stirring and mixing the injected cement slurry and earth and sand with the stirring blade 2 It is configured to form an improved pile.

  Moreover, the construction management system in the case of forming an improved pile by the processing machine 1 includes a slurry flow meter 6, a shaft tachometer 7 of the screw rod 3, a current detector 8 of the drive device 5, a depth meter 9 of the screw rod 3, and An elevation speed meter 10 is provided, and detection values from these sensors are input to the management device 11 so as to monitor the amount of cement slurry injected, the number of rotations of the screw rod 3, the depth of penetration, the penetration speed, and the withdrawal speed as management items. It is configured. Reference numeral 12 denotes an operation monitor installed in the base machine 4, and 13 denotes a data storage personal computer.

  And in order to improve the ground using such a processing machine 1, the screw rod 3 provided with the stirring blade 2 is rotated into the ground and penetrated to a predetermined depth without injecting the ground improvement material, By rotating the screw rod 3 and injecting the ground improvement material from the tip of the screw rod 3 while stirring the ground with the stirring blade 2 and pulling out the screw rod 3, the soil is solidified in a columnar shape in the ground. There is known a ground improvement method for building improved piles. In such a ground improvement method, the number of blade cuts at the time of extraction per unit depth (1 m) in the ground of the stirring blade 2 (at the time of ground improvement material injection) is a construction management item.

  The number of times of blade cutting affects the degree of agitation and mixing of the ground improvement material and the ground. If the number of blade cutting is increased, the construction speed is reduced, but the ground improvement material and the ground are mixed well. If the ground improvement material and the ground are mixed well, the generated ground improvement body will exhibit good strength as a whole, so that the on-site strength needs only a small additional to the design strength. This “in-situ strength” is a premium at a predetermined rate with respect to the design strength in consideration of variations in strength in actual construction.

  Conversely, if the number of blade cuts is reduced, the construction speed increases. However, since there is a possibility that some strength may not be generated due to insufficient mixing of the ground improvement material and the ground, in such a case, the on-site strength needs to be greatly increased with respect to the design strength. The coefficient of variation is related to this premium, and the coefficient of variation and the number of blade cuts have a predetermined relationship.

Incidentally, the relational expression between the design strength of the ground improvement body, the field strength and the coefficient of variation is as follows.
Qf = Qd / (1−α · Vc / 100) (1)
Qf: site uniaxial compressive strength (site strength), Qd: design uniaxial compressive strength (design strength), Vc: coefficient of variation (%), α: coefficient (α = 1.3 when defect occurrence rate is 10%) )

According to the above equation (1), for example, when the design strength Qd = 1000 kN / m ² , if the variation coefficient Vc = 30%, the field strength Qf = 1640 kN / m ² and the variation coefficient Vc = 15%, The field strength Qf = 1240 kN / m ² .

  In order to increase the on-site strength Qf, it is necessary to increase the amount of ground improvement material (cement slurry) made of water and cement into the ground. Since the weight ratio of water and cement in the ground improvement material is almost the same, this also increases the amount of cement mixed in. That is, the magnitude of the coefficient of variation Vc affects the construction cost.

  Conventionally, the relationship between the number of blade cuts after the ground improvement material was injected and the coefficient of variation was obtained, and in construction management, the number of blade cuts related to construction efficiency and the coefficient of variation related to construction costs were taken into account. The blade cutting frequency corresponding to the coefficient of variation is calculated, and construction management is performed so that the blade cutting frequency is the same as the blade cutting frequency at the site.

  The relationship between the above coefficient of variation and the number of blade cuttings. The conventional ground improvement method, in which the ground improvement material is injected into the ground while rotating the screw rod during penetration of the screw rod, and the ground improvement material and the ground are stirred and mixed. In FIG. 7, the number of blade cuts is set based on the relationship diagram (one logarithmic graph) as shown in FIG. Here, the number of blade cuts is the number of blade cuts when the ground improvement material is poured into the ground and the ground improvement material and the ground are stirred and mixed.

  On the other hand, the target variation in the ground improvement method that does not inject the ground improvement material at the time of screw rod penetration, injects the ground improvement material while pulling out the screw rod at the time of screw rod withdrawal, and stirs and mixes the ground improvement material and the ground. This relationship diagram was also used when setting the number of blade cuts at the time of pulling out the screw rod to inject the ground improvement material from the coefficient.

Japanese Patent No. 3583307

  However, in the ground improvement method using the stirring blades, as described above, if the number of blade cutting is increased, the ground improvement material and the ground will be mixed well, but the construction speed will be slowed down. Then, although construction speed became quick, there existed a problem that there exists a possibility that desired intensity | strength may not express in a ground improvement body.

  Then, this invention is made | formed in view of the said situation, and it aims at providing the ground improvement construction method which can improve construction efficiency, ensuring construction quality.

In order to solve the above-mentioned problems, the applicant paid attention to the number of times of blade cutting greatly related to the construction efficiency. Specifically, the present invention has been achieved by evaluating the number of blade cuttings when the screw rod penetrates to a predetermined depth without injecting the ground improvement material.
Specifically, in the invention described in claim 1, the rod provided with the stirring blades is penetrated to a predetermined depth while rotating into the ground without injecting the ground improvement material, and the rod is rotated to rotate the rod. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting material from the rod, the number of blade cutting of the stirring blade during penetration of the rod without injecting the ground improvement material, The number of adjustment blade cutting is calculated by adding to the number of blade cutting of the agitating blade at the time of pulling out the rod for injecting the ground improvement material, and the number of adjustment blade cutting is a predetermined ground improvement body strength variation coefficient and the number of adjustment blade cutting. From the relationship, it is set based on a target ground improvement body strength variation coefficient, and the ground improvement is performed using the set number of adjustment blade cuttings as a construction management item.

According to the ground improvement construction method according to claim 1, by improving the ground based on the number of adjustment blade cutting, it is possible to reduce the number of blade cutting at the time of pulling out the rod for injecting the ground improvement material. However, it is possible to improve the construction efficiency by reducing the number of blade cutting.
Moreover, by comprising in this way, in the construction management system which manages the condition of ground improvement, construction management can be performed directly using the adjustment blade cutting frequency. For example, as a construction management system for ground improvement, the number of blade cuts at the time of rod penetration and the number of blade cuts at the time of rod withdrawal can be calculated and displayed for each improvement depth, and the adjustment blade cut number is set as a construction management item And can be managed.

  Further, the invention described in claim 2 penetrates to a predetermined depth while rotating a rod provided with stirring blades into the ground and without injecting a ground improvement material, and rotates the rod to obtain the ground improvement material. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting from the rod, the number of blade cutting of the stirring blade at the time of penetration of the rod without injecting the ground improvement material is the ground improvement Including the number of blades of the agitating blade at the time of pulling out the rod for injecting the material as the number of blades for adjustment blade cutting. Set based on the target ground improvement body strength variation coefficient, blade cutting at the time of rod pull-out by subtracting the blade cutting frequency at the time of rod penetration from the set adjustment blade cutting frequency It is characterized by performing a ground improvement the number as construction management items.

According to the ground improvement method according to claim 2, since the ground improvement based on the number of adjustment blade cutting, the number of blade cutting at the time of pulling out the rod for injecting the ground improvement material may be smaller than conventional, However, it is possible to improve the construction efficiency by reducing the number of blade cutting.
In addition, with this construction, the construction management system that manages the status of ground improvement can calculate and display the number of adjustment blade cuts simply by calculating the number of blade cuts during rod insertion and rod withdrawal. However, if the blade cutting frequency when penetrating the rod can be made substantially constant for each improved depth, construction management can be performed based on the blade cutting frequency when the rod is pulled out.

  Further, the invention described in claim 3 penetrates to a predetermined depth while rotating a rod provided with stirring blades into the ground and without injecting a ground improvement material, and rotates the rod to obtain the ground improvement material. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting from the rod, the number of blade cutting of the stirring blade at the time of penetration of the rod without injecting the ground improvement material is the ground improvement Including the number of blade cutting of the agitating blade at the time of pulling out the rod for injecting the material into the adjustment blade cutting frequency, the target ground improvement body strength variation coefficient is the preset number of adjustment blade cutting and ground improvement body strength variation coefficient From the relationship, set based on a predetermined number of adjustment blade cutting, set the injection amount of the ground improvement material into the ground from the set ground improvement body strength variation coefficient, The injection volume is characterized by injecting in said ground.

  According to the ground improvement method according to claim 3, by improving the ground based on the number of adjustment blade cutting, it is possible to reduce the cost by reducing the injection amount of the ground improvement material even if the construction efficiency remains the same. .

  The invention described in claim 4 is characterized in that water is injected from the rod when the rod penetrates into the ground.

  According to the ground improvement method according to claim 4, the ground can be softened by pouring water into the ground, the penetration and rotation of the rod becomes smoother, and the unraveling effect by prior blade cutting before discharging the ground improvement material Can be increased.

  Further, the invention described in claim 5 is characterized in that the amount of water injection is an amount approximate to the amount of water obtained from the liquid limit of the ground to be improved.

  According to the ground improvement method according to claim 5, by making the amount injected into the ground appropriate, it is possible to prevent the amount of water injection to the ground from being excessively increased and the strength of the ground improvement body from being lowered. it can. That is, the penetration / rotation of the rod becomes smoother, the unraveling effect by cutting blades before discharging the ground improvement material can be enhanced, and the strength of the ground improvement body can be reliably ensured.

  According to the ground improvement method of the present invention, by improving the ground based on the number of adjustment blade cuttings, the number of blade cuttings at the time of pulling out the rod for injecting the ground improvement material may be reduced compared to the conventional blades. Construction efficiency can be improved by reducing the number of cuts. Alternatively, the construction efficiency can be kept as before, and the injection amount of the ground improvement material can be reduced to reduce the cost.

It is a figure which shows the outline | summary of the construction management system used for the ground improvement construction method of embodiment of this invention. It is a graph (1) which shows the relationship between the frequency | count of blade cutting and the coefficient of variation in the ground improvement construction method of this embodiment. It is a graph (1) which shows the relationship between the frequency | count of blade cutting and the coefficient of variation in the ground improvement construction method of this embodiment. It is a figure which shows an example of the management data in the construction management system of this embodiment. It is a figure which shows the other example of the management data in the same system. It is a figure which shows the outline | summary of the processing machine and construction management system in the conventional deep mixing processing method. It is a graph which shows the relationship between the frequency | count of blade cutting in a conventional ground improvement construction method, and a coefficient of variation.

  Hereinafter, specific embodiments of the ground improvement method of the present invention will be described with reference to the drawings. The ground improvement method of the present embodiment is a soil removal type deep-mixing processing method by the improvement machine 1 shown in FIG. That is, in the improvement machine 1 of FIG. 6, while rotating the screw rod 3 provided with the stirring blade 2 into the ground, and without injecting cement slurry (ground improvement material slurry) composed of water and cement to a predetermined improvement depth. Then, the screw rod 3 is rotated to improve the bottoming of the deepest portion, and the screw rod 3 is rotated to rotate the slurry discharge port at the tip of the screw rod 3 (in FIG. 6, the slurry discharge port is illustrated). 6, the slurry discharge port is provided in the vicinity of the lower end position of the screw rod 3 and the uppermost stirring blade 2 among the plural stages of the stirring blades 2. When the bottoming is improved, the slurry at the lower end of the screw rod is provided. The ground improvement material slurry is injected from the discharge port. The ground improvement material slurry is injected when the screw rod 3 is pulled out. In the ground improvement method in which the ground improvement material slurry is pulled out while the ground is stirred and mixed with the stirring blades 2 while the ground improvement material slurry is being injected from the nearby slurry discharge port. By doing so, it is a method of reducing the ground displacement accompanying the ground improvement material slurry injection. The construction management system used in the present embodiment is based on the conventional construction management system shown in FIG. 6 and is an improved machine by adding “soil removal amount” with a different calculation method to the management items. By monitoring the amount of soil discharged by No. 1 and maintaining it appropriately, it is configured to prevent displacement of the original ground (swelling and adverse effects on the surrounding ground). Furthermore, in the construction management system of this embodiment, in order to quantitatively grasp the stirring and mixing state of the cement slurry and earth and sand and properly manage it, the “blade cutting frequency” is added to the blade rod frequency when the screw rod is inserted. It is added as a management item.

  That is, the construction management system used in the present embodiment sets “material”, “formulation”, “mixing (number of blade cuttings)” as management items for quality control, as shown in FIG. “Positioning position”, “placement depth” and “bottom” are set as management items in the finished shape management, and “amount of soil removal” is set as a management item in the ground displacement management. Among these management items, “material”, “composition”, “placement position”, “placement depth”, and “bottom” are common to the conventional construction management system shown in FIG. “Mixing (number of blade cuttings)” and “soil removal amount” are management items added in the present embodiment with different contents.

  Among the management items common to the past, “material” is used to manage the state of cement slurry as a ground improvement material (cement amount and water amount), and “mixing” is the slurry injection amount (discharge) detected by the slurry flow meter 6. Volume) and the lifting / lowering speed of the screw rod 3 detected by the lifting / lowering speed meter 10 to manage whether or not the injection amount per unit depth is appropriate, the “placement position” is an improved pile by surveying by transit etc. The “placement depth” is the one that detects the position of the screw rod 3 by the depth meter 9 and manages it, and the “bottom” is the operation of the driving device 5 that is detected by the ammeter 8. Whether or not the tip of the screw rod 3 has reached the deepest part of the improvement target range is managed based on the state and the penetration speed detected by the elevating speed meter 10.

  Among the management items added in the present embodiment, the “soil removal amount” is calculated by calculating the estimated soil removal amount based on the rotational speed of the screw rod 3 detected by the shaft tachometer 7, the screw shape and the soil removal coefficient. , It is managed so as to be equivalent to the slurry injection amount.

In the present embodiment, the estimated amount of soil removal is performed as follows. The estimated soil removal amount V is a function of the screw cross-sectional area S, the screw pitch P, and the shaft rotation speed N, and is expressed as follows, with the proportionality constant being the soil removal coefficient K.
V = K · S · P · N (2)
V: Estimated amount of soil removed (m ³ )
K: soil removal coefficient S: screw cross-sectional area (m ² )
P: Screw pitch (m)
N: Shaft rotation speed (times)
In the above equation (2), the screw cross-sectional area S and screw pitch P are inherent constants of the improved machine 1, and once the value of the soil removal coefficient K is determined, the shaft rotational speed N from penetration to withdrawal is measured. It is possible to calculate the estimated soil discharge amount V only by doing.

Here, the inventors of the present application think that there is a correlation between the soil removal coefficient K and the ground improvement material mixing rate x, and based on a large number of construction results (data number n = 99), The correlation between the soil removal coefficient K and the ground improvement material mixing rate x was examined. As a result, the following equation (correlation coefficient r = 0.81) was obtained.
K = 0.5116x + 0.0066 (3)
x: Ground improvement material mixing rate The above equation (3) is an equation when the ground is cohesive soil, and a similar correlation equation can be obtained in advance for each soil condition of the ground.

Further, the ground improvement material mixing rate x is a volume ratio of the injection amount of the ground improvement material slurry to the improved ground, and is determined by how much the strength of the improved ground is made. The addition amount (kg) of the ground improvement material added to the unit improvement ground (1 m ³ ) is determined in advance. For example, the addition amount per 1 m ^{3 of the} improvement ground is about 100 kg. The ground improvement material is injected as a ground improvement material slurry (cement slurry) in which water is added to cement. The addition ratio W / C of water (W) to cement (C) is also taken into account in consideration of workability. Set it. In general, W / C is set to about 100%. In this case, the ground improvement material slurry corresponding to the added amount of 100 kg is about 133 liters (the specific gravity of the cement is 3). When 133 liter of ground improvement material slurry is injected and mixed in 1 m ^{3 of the} improved ground, the ground improvement material mixing rate x = 0.133 (13.3%). Thus, the ground improvement material mixing rate x is determined in advance. Then, x = 0.133 is substituted into the above equation (3) to calculate the soil removal coefficient K = 0.755.

  As described above, the soil removal coefficient K obtained in advance from the above equation (3) is calculated and set based on the ground improvement material mixing rate x. Alternatively, the soil removal coefficient K corresponding to the ground improvement material mixing rate x is set from a straight line chart of the above equation (3) in the orthogonal coordinates of the ground improvement material mixing rate x and the soil removal coefficient K. Then, if the set soil removal coefficient K, the screw cross-sectional area S, and the screw pitch P are input to the management device 11, the shaft rotational speed N detected by the shaft tachometer 7 is only input to the management device 11. The estimated soil discharge amount V is calculated and calculated by the above equation (2). It is preferable that the output of the shaft rotational speed N from the shaft tachometer 7 is automatically input to the management device 11. If it does in that way, after pulling out the screw rod 3 by K, S, and P inputted in advance, the estimated soil discharge amount V is immediately calculated and calculated. And in the construction management system of this embodiment, every time one improved pile is constructed, the estimated amount of soil removal V is calculated, and the construction is compared with the amount of slurry injected detected by the slurry flow meter 6. The quality is judged. Note that, if the shaft rotational speed N is adjusted, the estimated soil removal amount V can be increased or decreased. Therefore, if necessary, the estimated soil removal amount V can be controlled momentarily.

  Next, the “number of blade cuts” that is a management item added in the present embodiment will be described. The blade cutting frequency is a value indicating the number of blade cutting performed by each stirring blade 2 when the screw rod 3 is pulled out by the unit length. That is, the blade cutting frequency T (times / m) = (screw rod rotation speed n [times / min] × stirring blade number M [sheets]) / (screw rod lifting speed v [m / min]). Since the total number M of stirring blades in this equation is a constant specific to the improved machine, the blade cutting frequency T is obtained from the rotation speed n detected by the shaft tachometer 7 and the drawing speed v detected by the speedometer 9. Can do.

  In the actual construction, the ground improvement material is discharged as a slurry while the screw rod 3 is pulled out, and the blade cutting frequency T (times / m) when the ground improvement material and the ground are stirred and mixed, and the improved body A collected therefrom. Table 1 shows the relationship with the variation coefficient Vc (%) of the intensity of ~ D. Moreover, what plotted these results on the conventional relationship graph (FIG. 7) is the triangular points A1 to D1 in FIG.

  The magnitude of the variation coefficient Vc based on the blade cutting frequency T after discharging the ground improvement material at the triangular points A1 to D1 is smaller than the magnitude of the variation coefficient Vc obtained from the conventional relationship graph. In other words, the number of blade cutting when the screw rod penetrates before discharging the ground improvement material contributes to the coefficient of variation, in other words, stirring the ground without discharging the ground improvement material and unraveling the ground improvement material after that It can be inferred that it has a positive effect on the ground stirring effect after discharging.

  Therefore, the number of blade cuts when the screw rod penetrates before the ground improvement material is discharged / injected is added to the number of blade cuts when the screw rod is pulled out after the ground improvement material is discharged / injected. Table 2 shows the relationship between the total blade cutting frequency and the coefficient of variation. This is plotted on the conventional relationship graph (FIG. 7) as circle points A2 to D2 in FIG.

  As shown in FIG. 3, the round points A2 to D2 are closer to the conventional relationship graph than the triangular points A1 to D1. In other words, it can be determined that the total number of blade cuts may be evaluated.

The following equation represents the vicinity of the verification range at the four round points A2 to D2 in FIG.
Vc = −7.45ln (T) +64.221 r = 0.9345 (4)
Vc: coefficient of variation (%), T: total number of blade cuts, r: correlation coefficient, ln (T): natural logarithm

  In the present embodiment, the target variation coefficient Vc is substituted into the above equation (4) to calculate and set the total blade cutting number T, and the construction management is performed with this total blade cutting number T. For example, as a construction management system for ground improvement, if the number of blade cuts when the screw rod is inserted and the number of blade cuts when the screw rod is pulled out can be calculated and displayed for each improvement depth, the total blade cut count T can be managed. It can be set and managed as an item. Note that the above equation (4) may be a chart of orthogonal coordinates, and in that case, the target variation coefficient Vc may be applied to this chart to set the total blade cutting count T corresponding thereto.

  On the other hand, since the preferred penetration speed of the screw rod and the preferred rotation speed of the screw rod in the state where the ground improvement material is not discharged due to the type and hardness of the ground are known from experience, the blade cutting at the time of penetration of the screw rod is known. The number of times is considered to be almost fixed.

  And as the construction management system for ground improvement, if the blade cutting time is not calculated and displayed only by calculating the blade cutting frequency when the screw rod is inserted and withdrawing, the total blade cutting frequency T It is also possible to subtract, that is, subtract, the blade cutting frequency when the screw rod is inserted from the blade rod and perform construction management based on the blade cutting frequency when the screw rod is pulled out. Construction can be managed by either method.

  For example, when the variation coefficient Vc of the ground improvement body strength is set to 15%, according to the above equation (4), the total number of blade cutting is 740 times. When the number of blade cuts when the screw rod is inserted is 300 times, the number of blade cuts when the screw rod is pulled out is 440 times. The number of times of blade cutting at the time of pulling out the screw rod has been close to 1000 times in the conventional case, but the number is reduced significantly compared to that. As a result, the screw rod drawing speed can be increased as compared with the conventional case, and the construction efficiency is improved.

  In actual ground improvement, the total number of blade cuts displayed in the construction management system or the number of blade cuts when the screw rod is pulled out is calculated based on the target ground improvement body strength coefficient of variation. And adjust the screw rod rotation speed and screw rod extraction speed so that they do not deviate from the predetermined control value of the total blade cutting frequency or the blade cutting frequency when pulling out the screw rod. The ground will be improved through construction management. In addition, the relationship between the ground improvement body strength variation coefficient and the total number of blade cuttings is not limited to the above formula, and may change depending on the future construction data.

  In addition, the number of blade cutting of the stirring blade when the screw rod penetrates without the ground improvement material being added to the number of blade cutting of the stirring blade when the screw rod is injected with the ground improvement material added is added to the total blade cutting frequency. In addition to the case of adding 100% of the number of times of blade cutting when penetrating the screw rod as in the above embodiment, a part of the number of times of blade cutting when penetrating the screw rod (for example, about 70% to 80%) Depending on the difference in soil conditions, it can be considered that a predetermined upper limit is added to the addition of the number of blade cuttings when the screw rod penetrates. In the calculation of the number of blade cutting when the screw rod penetrates in this embodiment, it is added by multiplying by a predetermined coefficient, added with a predetermined value as the upper limit, or the stirring blade at the time of rod penetration without injecting the ground improvement material In consideration of the ground unraveling effect due to the blade cutting, it includes multiplying the number of blade cutting of the stirring blade when pulling out the rod for injecting the ground improvement material by a predetermined coefficient, and does not mean only simple addition . In that sense, the total blade cutting frequency in the present embodiment includes adjusting and counting the blade cutting frequency of the stirring blade when the screw rod is inserted, and can be said to be the adjusting blade cutting frequency. In the above embodiment, where the number of blade cuts at the time of penetration is subtracted from the total number of blade cuts, the number of blade cuts at the time of penetration is adjusted in the above embodiment. Is the number of blade cuts during penetration after adjustment.

  Each of the above management items is input to the management device (computer) 11 for evaluation, that is, whether the construction is good or bad, and based on the judgment, correction construction is performed as necessary. Construction data is stored in the personal computer 13 and appropriate management data, for example, a “construction result table” as shown in FIG. 4 and a “pile placing daily report” as shown in FIG. 5 are printed out as necessary. In the “construction result table” in FIG. 4, the target variation coefficient Vc and the total blade cutting count as the management value are not displayed, but the management value is calculated by separate calculation using equation (4) or the like. Is calculated and set, and this management value is input to the construction management device. Alternatively, the regression formula for each ground of the coefficient of variation Vc and the total blade cutting frequency T is programmed in advance, and the total blade cutting as a management value is entered by inputting the target coefficient of variation Vc and the ground type into the construction management device. The number of times T may be calculated and set.

  As another aspect, when the number of blade cuts at the time of pulling out the screw rod is set to the same number as the conventional method, the coefficient of variation Vc can be set smaller than the conventional method. The fact that the variation coefficient Vc can be set small can set the field strength of the ground improvement body smaller than the conventional one. That is, the injection amount of the ground improvement material can be made smaller than before. If comprised in this way, although construction efficiency is not different from the past, about construction cost, it can reduce more than before.

  For example, the blade cutting frequency after the ground improvement material injection at the time of screw rod drawing is 500 times / m. In the conventional technical idea, the ground improvement body strength variation coefficient at this time is 20% from FIG. On the other hand, in this embodiment, since the number of blade cuts when the screw rod penetrates without injecting the ground improvement material can be counted, if the number of blade cuts during the screw rod penetration is 300, the total number of blade cuts is 800 times. . Substituting this into the above equation (4) results in a coefficient of variation Vc = 14.3%.

When the design strength is 1000 kN / m ² , the conventional field strength setting is 1350 kN / m ² , but the field strength setting in this embodiment is 1230 kN / m ² . Since the on-site strength has a relationship of 0.5 to 0.8 with respect to the indoor blending strength, if this is 0.5, the on-site blending strength is 2700 kN / m ^{2 with} respect to the on-site strength of 1350 kN / m ² , For on-site strength of 1230 kN / m ² , the indoor blending strength is 2460 kN / m ² .

The relationship between the amount of cement (ground improvement material) added and the indoor blending strength is set through an indoor strength test, but for an indoor blending strength of 2700 kN / m ² , it is about 165 kg / m ³ and the indoor blending strength. For 2460 kN / m ² , it is about 150 kg / m ³ . For water-cement ratio of soil improvement material slurry (cement slurry) is often to 100%, if this is 100%, relative to the amount 165 kg / ^{m 3,} soil improvement material slurry injection volume 165L / ^{m 3} Thus, for the addition amount of 150 kg / m ³ , the ground improvement material slurry injection amount is 150 l / m ³ .

In construction, calculate the target ground improvement body strength variation coefficient from the above formula (relational formula of ground improvement body strength variation coefficient and total blade cutting frequency) based on the predetermined total blade cutting count (adjustment blade cutting count). From the set ground improvement body strength variation coefficient, the ground improvement material slurry injection amount is calculated and set as described above. Then, the ground improvement material slurry injection amount is controlled and controlled so that the actual ground improvement material slurry injection amount falls within a predetermined range with respect to the ground improvement material slurry amount (150 l / m ³ ) set above. To improve the ground. According to this embodiment, the ground improvement material slurry can be reduced as compared with the conventional case, and the construction cost can be reduced.

  As described above, according to the present embodiment, it is possible to increase the construction efficiency by reducing the number of blade cutting times compared to the prior art. As another method, it is possible to reduce the cost by reducing the amount of ground improvement material slurry injection while maintaining the conventional construction efficiency. Which method should be adopted may be determined in consideration of priorities in the actual site. Of course, it is possible to adjust the balance well so as to obtain a moderate cost reduction effect while reducing the number of blade cuttings moderately and decreasing the ground improvement material slurry injection amount moderately and improving the construction efficiency moderately. is there.

  In this embodiment, water may be discharged and injected from the ground improvement material slurry discharge port (at the lower end position of the screw rod 3 in FIG. 6) at the tip of the screw rod when the screw rod penetrates. If constituted in this way, it is surmised that the ground becomes soft due to the addition of water to the ground, the screw rods penetrate and rotate more smoothly, and the effect of unraveling by prior blade cutting before the ground improvement material slurry discharge is increased. . In that case, it is conceivable that the assumed regression line of the coefficient of variation and the total number of blade cuttings is located further lower than that according to the above equation in the graph shown in FIG.

  However, too much water at the time of penetration of the screw rod is expected to affect the strength of the ground improvement body, so at most, the amount of water calculated from the liquid limit of the target ground to be improved at most. It can be said that an amount close to the amount of water obtained from the liquid limit is preferable. In addition to this particularly effective for the ground above the groundwater level, the addition of water at the time of penetration of the screw rod is a conventional ground improvement method in which the ground improvement material and the ground are stirred and mixed by a stirring blade other than this embodiment. Is also applicable.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention. That is, the specific structure and configuration described in the embodiment are merely examples, and can be changed as appropriate.
For example, the construction management method based on the total blade cutting frequency (adjustment blade cutting frequency) in the present embodiment can be applied even if it is not a soil removal type deep mixing treatment method that discharges soil equivalent to the amount of ground improvement material injection.

  DESCRIPTION OF SYMBOLS 1 ... Improved machine 2 ... Stirring blade 3 ... Screw rod (rod) 6 ... Slurry flow meter 7 ... Shaft tachometer 8 ... Current detector 9 ... Depth meter 10 ... Speedometer 11 ... Management device

In order to solve the above-mentioned problems, the applicant paid attention to the number of times of blade cutting greatly related to the construction efficiency. Specifically, the present invention has been achieved by evaluating the number of blade cuttings when the screw rod penetrates to a predetermined depth without injecting the ground improvement material.
Specifically, in the invention described in claim 1, the rod provided with the stirring blades is penetrated to a predetermined depth while rotating into the ground without injecting the ground improvement material, and the rod is rotated to rotate the rod. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting material from the rod, the number of blade cutting of the stirring blade during penetration of the rod without injecting the ground improvement material, The number of adjustment blade cutting is calculated by adding to the number of blade cutting of the agitating blade at the time of pulling out the rod for injecting the ground improvement material, and the number of adjustment blade cutting is a predetermined ground improvement body strength variation coefficient and the number of adjustment blade cutting. from the relationship, then set based on the soil improvement material strength variation coefficient of the target, by performing a soil improving adjusting blade cutting number of times said set as construction management item, the ground breaks Compared to the case where only the number of blade cutting of the stirring blade at the time of pulling out the rod for injecting material is set as a construction management item, blade cutting of the stirring blade at the time of pulling out the rod for injecting the ground improvement material when ensuring the same quality The number of times can be reduced .

Further, the invention described in claim 2 penetrates to a predetermined depth while rotating a rod provided with stirring blades into the ground and without injecting a ground improvement material, and rotates the rod to obtain the ground improvement material. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting from the rod, the number of blade cutting of the stirring blade at the time of penetration of the rod without injecting the ground improvement material is the ground improvement Including the number of blades of the agitating blade at the time of pulling out the rod for injecting the material as the number of blades for adjustment blade cutting. Set based on the target ground improvement body strength variation coefficient, blade cutting at the time of rod pull-out by subtracting the blade cutting frequency at the time of rod penetration from the set adjustment blade cutting frequency By performing ground improvement the number as construction management items, compared to only blade cutting the number of the stirring blade when the rod is drawn to inject the soil improvement material when the construction management item, the when to ensure the quality The present invention is characterized in that the number of blade cutting of the stirring blade at the time of pulling out the rod for injecting the ground improvement material can be reduced .

Further, the invention described in claim 3 penetrates to a predetermined depth while rotating a rod provided with stirring blades into the ground and without injecting a ground improvement material, and rotates the rod to obtain the ground improvement material. In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting from the rod, the number of blade cutting of the stirring blade at the time of penetration of the rod without injecting the ground improvement material is the ground improvement Including the number of blade cutting of the agitating blade at the time of pulling out the rod for injecting the material into the adjustment blade cutting frequency, the target ground improvement body strength variation coefficient is the preset number of adjustment blade cutting and ground improvement body strength variation coefficient From the relationship, set based on a predetermined number of adjustment blade cutting, set the injection amount of the ground improvement material into the ground from the set ground improvement body strength variation coefficient, By injecting an injection quantity in said ground, the injection amount of the soil improvement material only from the blade cutting the number of the stirring blade when the rod is drawn to inject the soil improvement material seeking the soil improvement material strength coefficient of variation Compared with the case where it sets, when the same quality is ensured, the injection amount of the ground improvement material can be reduced .

Claims (5)

While rotating the rod with stirring blades into the ground and without injecting the ground improvement material, it penetrates to a predetermined depth,
In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting the ground improvement material from the rod by rotating the rod,
The number of blade cutting of the stirring blade at the time of penetrating the rod without injecting the ground improvement material, the number of blade cutting of the stirring blade at the time of pulling out the rod to inject the ground improvement material, and the number of blade cutting adjustment,
The number of adjustment blade cutting is set based on the ground improvement body strength variation coefficient as a target from the relationship between the preset ground improvement body strength variation coefficient and the number of adjustment blade cutting,
A ground improvement method for performing ground improvement using the set number of adjustment blade cuttings as a construction management item. While rotating the rod with stirring blades into the ground and without injecting the ground improvement material, it penetrates to a predetermined depth,
In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting the ground improvement material from the rod by rotating the rod,
The number of blade cutting of the stirring blade at the time of penetrating the rod without injecting the ground improvement material, the number of blade cutting of the stirring blade at the time of pulling out the rod to inject the ground improvement material, and the number of blade cutting adjustment,
The number of adjustment blade cutting is set based on the ground improvement body strength variation coefficient as a target from the relationship between the preset ground improvement body strength variation coefficient and the number of adjustment blade cutting,
A ground improvement method for performing ground improvement with the number of blade cuts at the time of pulling out the rod obtained by subtracting the number of blade cuts at the time of rod penetration from the set number of adjustment blade cuts. While rotating the rod with stirring blades into the ground and without injecting the ground improvement material, it penetrates to a predetermined depth,
In the ground improvement method of pulling out the rod while stirring and mixing the ground with the stirring blade while injecting the ground improvement material from the rod by rotating the rod,
The number of blade cutting of the stirring blade at the time of penetrating the rod without injecting the ground improvement material, the number of blade cutting of the stirring blade at the time of pulling out the rod to inject the ground improvement material, and the number of blade cutting adjustment,
The target ground improvement body strength variation coefficient is set based on a predetermined number of adjustment blade cutting times, from the relationship between the preset adjustment blade cutting frequency and the ground improvement body strength variation coefficient,
A ground improvement construction method characterized by setting an injection amount of the ground improvement material into the ground from the set ground improvement body strength variation coefficient and injecting the injection amount into the ground.   The ground improvement construction method according to any one of claims 1 to 3, wherein water is injected from the rod when the rod penetrates into the ground.   5. The ground improvement method according to claim 4, wherein the amount of water injection is an amount approximate to the amount of water obtained from the liquid limit of the ground to be improved.

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