JP6529786B2 - Ground improvement method - Google Patents

Description

  According to the present invention, after the ground to be improved, such as soft ground, is bored while injecting drilling water, a ground improvement material such as a solidified material slurry is injected into the ground, and the solidified material slurry and the soft ground are mixed. It relates to the ground improvement method of forming an improved column.

  In the ground improvement method in which the ground improvement material such as solidified material slurry is mixed and stirred in the ground, deformation in the ground is transmitted to the surrounding ground unless the original ground is excavated in an amount corresponding to the volume of the mixed solidified material slurry. Not a small amount of displacement in the surrounding ground.

  In general, the ground improvement method using a single-tube high-pressure jet agitation ground improvement device does not produce sludge during construction compared to other double-tube, triple-tube high-pressure jet agitation methods. However, displacement of surrounding ground is likely to occur.

  The following ground improvement method is available as a method that achieves both the economics of the single-tube high-pressure jet stirring method and the reduction of displacement to the surrounding ground. The radius of the soil push-up disk is the same size as the radius of the stirring blade provided on the shaft of the injection rod, or 10 cm or less, preferably 5 cm smaller than the radius of the stirring blade, and the projected plane shape is the center plus the center Stirring device equipped with a soil push-up disc in which the angle of a spiral-shaped soil push-up disc is formed to be 10 to 20 ° in a sector-like shape with an angle of about 10 °, or in approximately 1 round circumference. When drilling soft ground, drilling is performed by re-drilling and re-raising several times and by injecting drilling water at low pressure, the diameter of the disturbance portion formed by the stirring blade and the soil lifting When the soft ground and the area outside the diameter included in the diameter of the disc are cut off by the cylindrical mud film, when the soft soil included in the diameter of the soil lifting disc is pushed upward Single-tube high-pressure injection stirring that reduces soil shear resistance and enables reliable discharge Construction method (for example, refer to patent documents 1 and 2).

Unexamined-Japanese-Patent No. 2005-120819 (patent 4740571) JP, 2010-138691, A (patent No. 4964123)

However, in the single-tube high-pressure jet agitation method, the soil to be improved is particularly soft clay with a high water content ratio, highly sensitive viscous soil with a natural water content ratio exceeding the liquid limit, and a small amount of fine particles. In the case of sandy soil, mud film is difficult to form even if it is re-stirred, and a large amount of soil to be excavated falls down to the periphery without being placed on the soil lifting plate, making it difficult to be discharged to the ground. (Total displacement volume (量 V: m ³ ) ÷ total injection slurry volume (Σ q: kl) × 100%) may be small, and displacement may occur in the surrounding ground.

  In view of the above circumstances, the present invention provides a soil to be improved, in particular a soft clay with a high water content ratio, a highly sensitive viscous soil with a natural water content ratio exceeding the liquid limit, and a sandy soil with a small amount of fine particles. Even if the total injected slurry amount (total solidified material slurry injected amount) and the total discharge amount almost match, so that the discharge rate is almost 100%, to reduce the occurrence of ground displacement With the goal.

According to the present invention, the ground for improvement is drilled to a predetermined depth by a stirring device provided with a digging blade at the tip of the injection rod, a stirring blade provided above the drilling blade, and a soil push-up plate near the upper side of the stirring blade. Water is injected while drilling to form a drilling hole, a drilling step to form a drilling hole, and after the injection rod is pulled out to the ground, a re-drilling step of inserting into the drilling hole and returning to the bottom part, rotating the injection rod While making it pull out, the solidifying material slurry is injected at high pressure into the ground, and the energy of the solidifying material slurry cuts and mixes the outside of the agitating blade, and approaches the upper part of the solidifying material slurry injection port of the injection rod The mixed soil mixed with the solidifying material slurry is absorbed in the space while pushing up the disturbed soil in the vicinity of the injection nozzle by the soil lifting plate provided to form a void below the soil lifting plate, while absorbing the mixed soil mixed with the solidified slurry. Columnar in the ground And Construction process of reclamation improved body, the ground improvement method provided with, at the time of drilling water injection auxiliary drilling process during the drilling process or reclamation process, the balance between the discharge amount of soil and the injection amount of slurry is lost In this case, a grout can be used to titrate and mix a high concentration thickener liquid to the above-mentioned drilling water, and when the drilling water is fed with a high pressure pump, the flow rate from the high concentration thickener liquid tank can be finely adjusted. A high concentration thickener solution is added to the drilling water by a titration and mixing method in which the high concentration thickener solution is fed into a common pipe by a pump and merged with the drilling water at an arbitrary flow rate upstream of the high pressure pump. By mixing so that the target concentration of the viscosity agent is achieved, the drilling water is made to be a viscous drilling water having a thickening action, and the total discharge volume per one improved body is made to almost coincide with the total injected slurry volume. It is a ground improvement method characterized by this.

  Further, according to the present invention, the concentration of the thickener in the viscosity drilling water having the thickening action is set by conducting test construction to set the concentration of thickener at which the earth drainage rate in the ground to be improved is about 100%. It is an improvement method.

According to the present invention, the ground for improvement is drilled to a predetermined depth by a stirring device provided with a digging blade at the tip of the injection rod, a stirring blade provided above the drilling blade, and a soil push-up plate near the upper side of the stirring blade. Water is injected while drilling to form a drilling hole, a drilling step to form a drilling hole, and after the injection rod is pulled out to the ground, a re-drilling step of inserting into the drilling hole and returning to the bottom part, rotating the injection rod While making it pull out, the solidifying material slurry is injected at high pressure into the ground, and the energy of the solidifying material slurry cuts and mixes the outside of the agitating blade, and approaches the upper part of the solidifying material slurry injection port of the injection rod The mixed soil mixed with the solidifying material slurry is absorbed in the space while pushing up the disturbed soil in the vicinity of the injection nozzle by the soil lifting plate provided to form a void below the soil lifting plate, while absorbing the mixed soil mixed with the solidified slurry. Columnar in the ground In the ground improvement method including the formation step of forming an improved body, a high concentration thickener liquid is titrated in the hole formation water at the time of the hole formation water injection in the auxiliary hole formation step in the hole formation step or the formation step. By mixing, the drilling water is made to be a viscous drilling water having a thickening action, and from the beginning of construction, the viscous drilling water having a thickening action as a drilling water is used as a reference viscosity drilling water In the auxiliary drilling step in the formation step, in order to change the thickener concentration of the reference viscosity drilling water according to the discharge condition, a high concentration thickener liquid is added to the reference viscosity drilling water Using the drilling water having a concentration higher than that of the standard viscosity drilling water by titration and mixing, the total discharge volume per one improved body substantially matches the total injected slurry volume. It is a ground improvement method characterized by this.

  Moreover, this invention is a ground improvement construction method which carries out test construction and sets the thickener concentration which the earth removal rate in the improvement object ground becomes about 100%, as for the thickener concentration of the said standard viscosity drilling water .

In the present invention , a drilling blade is provided at the tip of the injection rod, a stirring blade is provided above the cutting blade, and a soil push-up plate is provided near the upper portion of the stirring blade. Drilling a hole while forming a hole, forming a hole, drawing the injection rod to the ground, inserting it into the hole and re-drilling a bottom part, rotating the injection rod While pulling out the solidifying material slurry at high pressure into the ground while cutting and mixing the outside of the stirring blade with the energy of the solidifying material slurry, close to the upper part of the solidifying material slurry injection port of the injection rod Disturbing soil in the vicinity of the jet nozzle is pushed upward by the provided soil push-up plate to form a void below the soil push-up plate, and the mixed soil mixed with the solidifying material slurry is absorbed in the space, In a cylindrical shape In the ground improvement method including the formation step of forming a good body, a high concentration thickener liquid is titrated to the drilling water at the time of the drilling water injection of the auxiliary drilling step in the drilling step or the formation step. By mixing, the drilling water is made into viscous drilling water having a thickening action, and in the auxiliary drilling process during the formation process, when the amount of soil removal is smaller than the injection amount of the solidified material slurry, Step of stopping injection of solidified material slurry and withdrawing the injection rod, and titrating and mixing high concentration thickener liquid with drilling water or reference viscosity drilling water, thickening of drilling water or reference viscosity drilling water Changing the agent concentration and re-drilling while injecting, and returning the tip end of the injection rod to the stopped position.

  The present invention relates to a high concentration thickener for the drilling water when the balance between the amount of earth removal and the amount of injected slurry is broken at the time of spraying the drilling water in the auxiliary drilling step in the drilling step or the formation step. By titrating and mixing the solution, the thickener concentration of the drilling water is changed timely, and the total drainage volume and the total injected slurry volume (total injected volume of the solidifying material slurry) per modified body is almost equal. As the soil removal rate can be kept almost 100%, the occurrence of displacement of the ground to be improved can be reduced.

  Here, "to make the total amount of soil discharge and the total amount of the injected slurry almost coincide" is not only the case of perfect agreement, but if it is within the range of the allowable ground displacement amount, allow some difference between the two. It also means that "removal rate is almost 100%" means that it will allow not only 100% for the earth removal rate, but also more than 100% difference within the allowable ground displacement range. .

  When ground improvement is to be carried out, the allowable ground displacement after completion of construction is set, but within the range corresponding to this allowable ground displacement, a slight deviation between the total amount of soil removal and the total amount of injected slurry, discharge Some deviation from 100% of the rate is acceptable. As an example of the allowable ground displacement amount, a horizontal displacement amount of ± 10 mm, and as an example of the earth removal rate, 90% can be mentioned. Therefore, in the actual construction, these expressions mean that "almost agree" means "match within the allowable displacement" and "about 100%" means "within the allowable displacement". is there.

  Moreover, since an expensive thickener can be used without waste according to the earth removal situation, construction efficiency is good and economical construction can be performed.

It is a figure which shows 1st Example of this invention, and is a partial cross-section front view which shows the state at the time of drilling, and base-material arrangement | positioning. It is a partial cross section front view which shows the state at the time of improvement body creation, and substrate arrangement. The vertical axis represents the total injected slurry amount q q (kl), the displacement amount δ δ (cm), and the total soil amount Σ V (vertical axis). m ³ ), the horizontal axis shows time (H). The vertical axis represents the total injected slurry amount q q (kl), the displacement amount δ δ (cm), and the total soil removal amount V V (m). ³ ), the horizontal axis shows time (H). It is a figure which shows the relationship between the earth removal rate (%) and the density | concentration (%) of viscous drilling water. The vertical axis represents the total injected slurry amount q q (kl), the displacement amount δ δ (cm), and the total soil removal amount V (M ³ ), horizontal axis is time (H). The figure shows the relationship between the amount of soil removal, the amount of solidified material slurry injected, and the amount of displacement when securing the soil removal rate of 100% by re-drilling after construction interruption due to soil failure, and the vertical axis is the total injection The amount of slurry q q (kl), the amount of displacement δ δ (cm), the total amount of earth removal 排 V (m ³ ), the horizontal axis represents time (H).

  The inventor of the present invention considered that the reason why the earth removal rate (total earth removal amount ÷ V ÷ total injection slurry amount qq) is small is due to the soil characteristics of the ground to be improved. Furthermore, in the case of a viscous soil layer in which the soil characteristics do not exceed the liquid limit, a sand layer having a good particle size or containing a fine particle to some extent, etc., the soil removal rate is good. This is because, after the drilling rod is bored while spouting the drilling water from the pouring rod, and when the solidified material slurry is spouted out from the bored hole, the soil in the bored hole is hard to slide off the soil lifting plate. ,it is conceivable that.

  On the other hand, in the case of a viscous soil layer whose soil characteristics exceed the liquid limit, a loose sand layer having a poor particle size or a small amount of fine particles, or an alternate layer of clay and sand, the soil removal rate is not good. It is considered that this is because the target soil to be earthed is in a liquefaction state, and the earth in the drilling becomes easy to slide off from the soil lifting board during the earth drainage.

  Therefore, when drilling the ground to be improved with a low soil removal rate, a thickener is added to the normal drilling water, that is, the drilling water normally used (fresh water, river water, seawater, etc.), If we use viscosity drilling water, which has a thickening effect, it is easy to fix the fluid soil and maintain the shape as a lump, and it is possible to prevent the drainage from sliding off the soil lifting plate, and it is also optimal. We investigated how to determine the amount of thickener added and how to maintain the appropriate thickener concentration in the viscosity drilling water at all times to changes in soil characteristics.

  As a result, based on the soil column diagram of the ground to be improved, etc., the case where the improvement target ground is a sticky soil layer exceeding the liquid limit, a loose sand layer with poor grain size or small fines, or alternating layers of clay and sand, etc. If the soil quality is expected to have a tendency that the rate of soil erosion will decrease, test construction should be carried out on the ground to be improved beforehand, and the rate of soil erosion will be approximately 100%. Set the thickener concentration of the viscous drilling water so that the soil rate can be secured. And in the construction work, while the construction is usually performed using drilling water, the soil removal rate is observed, and if it is judged that the soil removal can not secure approximately 100%, the drilling water to be used is used. The high concentration thickener solution is titrated and mixed, and it is adjusted to the viscosity drilling water which can secure about 100% of the soil removal rate set by the test construction, and construction is performed.

  Here, in the "high concentration thickener liquid", an appropriate amount of thickener is mixed with the drilling water to be actually used, or the thickener concentration of the drilling water having a small thickener concentration is increased. For this purpose, it refers to a high concentration aqueous thickener solution in which a thickening agent such as CMC is dissolved at a concentration several to ten times higher than that usually used.

Further, where the "titration mixing", at the time of water the drilling water at high pressure pump 29, high-concentration thickener solution by Grau preparative pump 28g that can finely adjust the flow rate of the high concentration thickener tank 28 Is sent to the common pipe 30 and merged with the drilling water at an arbitrary flow rate upstream of the high-pressure pump 29, so that viscous drilling water with a target thickener concentration can be obtained timely Refers to the method of addition. And the drilling water which mixed the high concentration thickener liquid with the drilling water or the viscous drilling water (it is small concentration) by the said titration mixing is called viscosity drilling water.

  In the test construction, the construction is usually carried out with viscosity drilling water having different thickener concentrations of about 2 to 4 levels, and the minimum thickener concentration capable of securing a discharge rate of almost 100% is determined. Figures 4a and 4b explain the concept of this test construction.

  And when the drainage rate is observed while performing construction using normal drilling water, and it is judged that the soil can not secure approximately 100%, the test is carried out by performing titration mixing on the drilling water. While performing construction using viscous drilling water of concentration set in the construction (hereinafter, may be referred to as “reference viscous drilling water”), the above-mentioned according to the discharge situation in the auxiliary drilling process of the construction process Viscosity drilling water (hereinafter referred to as "high concentration viscosity drilling water") which is obtained by titrating and mixing a high concentration thickener liquid having a higher thickener concentration than the standard viscosity drilling water to the standard viscosity drilling water Since the total amount of soil discharge and the total amount of injected slurry can be made substantially the same (by the same degree) by adopting the above, the soil removal rate can be improved, and the occurrence of displacement of the ground to be improved can be prevented. The present invention has been made based on the above findings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 6, but first, the ground improvement device will be outlined.

  The single-tube type injection rod 2 is vertically supported by the support 4 of the rotary vertical movement mechanism 1. A digging blade (earth auger) 3 is provided at the tip of the injection rod 2, and a stirring blade 5 and a spiral soil pushing disc 6 are sequentially provided at an interval above the tip. Although the injection | spray nozzle 10 is provided in the front-end | tip of the said stirring blade 5, this injection | spray nozzle 10 functions as a drilling water injection hole and a solidification agent slurry injection hole. The soil push-up disc 6 is formed to have a smaller radius of 10 cm or less, preferably 5 cm, than the stirring blade 5.

  A swivel 8 is provided at the rear end of the injection rod 2, and the swivel 8 is connected to a high pressure pump 29 via a solidified material slurry pressure feed hose 9.

Next, the flow path system of the drilling water will be described. The high pressure pump 29 is connected to the system of the high concentration thickener liquid tank 28 and the system of the drilling water tank 25 via the common pipe 30 to which the flow meter 27 b is attached. Strains of the high-concentration thickener solution tank 28, the high concentration thickener solution solenoid valve 28v from the tank 28, Grau split pump 28 g, supply a high concentration thickener solution to the shared pipe 30 through a flow meter 28b. A high concentration viscous drilling water with a thickener concentration greater than that of the viscous drilling water is produced by titrating and mixing a high concentration thickener liquid with the viscous drilling water. Control of the flow rate of the high concentration thickener liquid (minimum flow rate of about 0.5 l / min) required for the titration and mixing is performed via a grout pump 28 g and a flow meter 28 b.

  The system of the drilling water tank 25 is connected to the common pipe 30 through the solenoid valve 25v. The drilling water in the tank 25 is usually drilling water (fresh water, river water, sea water or the like), and its flow rate is controlled by a flow meter 27 b. The high concentration thickener liquid of the high concentration thickener liquid tank 28 and the drilling water of the group of the drilling water tank 25 merge upstream of the high pressure pump 29 of the common pipe 30, and the target thickener It is sent to the pumping hose 9 as viscous drilling water having a concentration.

  As a thickener to be added to the pore-forming water, a thickener such as a methylcellulose-based material such as CMC or a water-soluble polymer-based material such as guar gum is mainly used, but it is not limited thereto. As the high concentration thickener liquid, for example, a thickener solution having a thickener concentration of about 3.0% to 10.0% is used. The titration volume of the high concentration thickener liquid can be adjusted arbitrarily by operating the valve 28v through the flow meter 28b through the flowmeter 28b of the grout pump, so that it is possible to easily carry out titration mixing to the target thickener concentration. it can.

  The system of the solidifying material slurry includes the slurry plant 27. The slurry plant 27 kneads the cement-based solidifying material and the kneading water at a constant ratio and temporarily holds it in the agitator. The electromagnetic valve 27V, shared It is connected to a high pressure pump 29 via a pipe 30 and a flow meter 27b.

  The ground improvement method using the ground improvement device includes a drilling process, a re-drilling process, and a formation process.

  The drilling process is performed by a stirring device provided with a digging blade 3 at the tip of the injection rod 2, provided with a stirring blade 5 above the drilling blade 3, and provided with a spiral soil push-up plate 6 in the vicinity above the stirring blade 5. This is a step of forming a drilling hole 13 by drilling while injecting drilling water from the injection nozzle 10 (drilling water injection port) to the planned depth of the ground to be improved.

  The re-drilling step is a step in which the injection rod 2 in the drilling hole 13 is withdrawn to the ground, and then inserted into the drilling hole 13 to return it to the bottom.

  Furthermore, in the formation step, while the injection rod 2 is rotated and pulled out, the solidifying material slurry (land improvement material) 14 is injected at high pressure from the injection nozzle 10 (solidifying material slurry injection port) into the ground. The soil push-up plate 6 provided in the vicinity of the upper part of the injection nozzle 10 of the injection rod 2 while cutting and mixing the outside of the stirring blade 5 with the energy of the slurry 14 To the upper part of the soil push-up plate 6 to absorb the mixed soil mixed with the solidifying material slurry 14 in the space 7 and build up the columnar improved body 15 in the ground It is a process.

  In the present invention, normal drilling water (fresh water, river water, sea water etc.) is used as the drilling water, but when it is judged that 100% of the soil removal rate can not be secured, titration of the high concentration thickener solution is performed. Use standard viscosity drilling water that has a thickening effect by mixing. And the thickener concentration of this standard viscosity drilling water is determined based on test construction as mentioned above.

First, a production method by titration and mixing of viscous drilling water having a target concentration will be described.
For convenience of explanation, the drilling water is pure water, the thickener concentration of the high concentration thickener liquid is 5.0%, and the thickener concentration of the viscosity drilling water (after titration and mixing) is 0. The case of increasing to 3% and 0.5% will be described as an example.

The concentration and flow rate of each drilling water are indicated by the symbols in the table below.

  Assuming that the flow rate q (l / min) of drilling water (viscous drilling water) at the target thickener concentration is 30 l / min, the total flow is 30 l / min, so x + y = 30, included in the liquid volume Since ax + by = 30 M according to the relationship of the thickener amount to be obtained, a = 0% when the thickener concentration of the drilling water (viscous drilling water) of the target thickener concentration is 0.3% , B = 5.0%, M = 0.3%, q = 30 l / min, and x = 28.2 l / min, y = 1.8 l / min.

  When the thickener concentration of the drilling water (viscous drilling water) of the target thickener concentration is 0.5%, a = 0%, b = 5.0%, M = 0.5%, q = 30 l / min, so x = 27.0 l / min, y = 3.0 l / min.

  Taking into account the controllable range of the grout pump 28g which can finely adjust this calculation result, the flow rate x of the standard viscosity drilling water and the flow rate y of the high concentration thickener liquid are merged to obtain the target thickener concentration Send as viscous drilling water.

  In this construction, when producing viscosity drilling water of a target thickener concentration, open the electromagnetic valve 28v of the high concentration thickener liquid tank 28, and flow the high concentration thickener liquid with the flow meter 28b. While controlling the flow rate of the drilling water flowing in the common pipe 30 with the flow meter 27b, while controlling the flow rate of the drilling water flowing in the common pipe 30, the total flow rate is for the flow meter 28b (for high concentration thickener liquid) Monitor and control as a sum of drilling water) and join them.

  Next, the earth measurement measurement management at the construction time will be described.

  During the drilling process and the formation process, the amount of soil discharge is detected by the amount of soil discharge detection means. For example, a wedge-shaped instrument is used as the amount of soil discharge detection means. This wedge-shaped instrument comprises a rectangular bottom plate having an inlet hole, a vertical wall surrounding the four sides of the bottom plate, and a scale provided on the vertical wall to measure the height from the bottom plate (not shown). .

  This wedge-shaped instrument is disposed on the ground to be improved in accordance with the inlet hole and measures the amount of soil discharge by measuring the amount (bulk) of soil excavated from the inlet hole with the scale. The earth removal rate is a value (ΣV / Σq) obtained by dividing the total earth removal amount VV measured by the earth removal detection means by the total injected slurry amount (total injection amount of the solidifying material slurry) qq. If this value is 100%, the displacement applied to the surrounding ground can be reduced to almost zero.

  The amount of earth drainage discharged from the drilling hole and the injection amount of the solidifying material slurry are compared, and the relationship between the two (earth drainage rate) is compared and examined. The relationship between the two is shown in FIG. 3 as a conceptual diagram.

  The total injected slurry amount q q (kl) is the product of the solidified material slurry injection amount q, the injection time t, and the improvement length per one, for example, the solidified material slurry injection amount q = 100 l / min, the injection time t = 4 When the improvement length is 10 m, the total injected slurry q q = 4000 l = 4.0 kl, and it increases with the elapse of the injection time t (H), and the time t1 (= 4 minutes / m × 10 m = 40 minutes) elapses The total amount of the solidified material slurry (designed slurry total amount: kl) M planned for the above becomes M, but the injection amount of the solidified material slurry at this time changes linearly as shown by the solid line Lq.

  On the other hand, when the earth removal rate can be ideally secured, the total earth removal amount VV shifts substantially along the solid line Lq as indicated by the dashed line Lv, and the total earth removal amount at time t1 ΣV becomes M and almost agrees with the total injection slurry amount Σq, and the soil removal rate (total earth removal amount / total injection slurry amount) becomes almost 100%. In this way, the displacement amount δ when the earth removal rate can be secured 100% by following an appropriate earth removal process becomes almost 0 and changes along the horizontal axis (time axis), as indicated by the dashed line Lδ.

  The thickener concentration of the viscous drilling water is determined by testing and constructing the ground to be improved (target ground), but in order to obtain the optimum thickener concentration, the test construction is performed multiple times at least three times. It is preferable to

If the relationship between the total injected slurry amount (q (kl) and the total soil removal amount, V (m ³ ) of the test constructions A, B and C in three times is plotted on the horizontal axis at time t (H), as shown in FIG. become.

  In the test construction A, as indicated by the broken line LvA, the total soil removal amount VV is about 72% of the total injected slurry amount qq (designed slurry total amount M) at time t3 when the construction process is completed, which is considerably smaller than 100%. Therefore, there is a possibility that the soil to be discharged from the hole is slipped from the soil lifting plate

  In the test construction B, as indicated by a chain line LvB, the total earth removal amount VV is about 98% of the total injection slurry amount qq at time t3 when the construction process is completed.

  As shown by the solid line LvC, in the test construction C, the total soil removal amount VV is about 103% of the total injection slurry amount qq at time t3 at the end of the construction process and slightly exceeds the total injection slurry amount VV The concentration of the agent may be too high and it is uneconomical.

  Ideally, it is desirable that the solid line Lq of the total injected slurry amount q q coincide with the dashed line V of the total earth removal amount V V. The thickener concentration is the highest in the case of the total injected slurry amount Σ q 総 total earth removal amount V V It is preferable to set small drilling water as reference thickening drilling water with a standard thickening action. Therefore, as the viscosity drilling water concentration, as shown in FIG. 4b, the viscosity drilling water concentration (%) at the time of 3 types of test construction is corresponding to the horizontal axis, and the vertical axis corresponds to The soil removal rate (%) to be taken is taken and three points are connected by a curve, and the concentration S of the thickener corresponding to the soil removal rate 100% is taken as the thickener concentration of the viscous drilling water used in the work.

  Next, the main construction will be described.

  After setting the thickener concentration of the viscous drilling water on the basis of the results of the above test and construction, the normal drilling (implementation process, re-drilling process and formation process) is carried out using normal drilling water.

  In the construction process, the ideal relationship (Σ q 理想 V V) between the injection amount of the solidified material slurry and the amount of the soil removal in the construction process may deviate from each other.

  For example, as shown in FIG. 5, after the injection time tn has elapsed after the dashed line V indicating the total earth removal amount, a large difference occurs between the total earth removal amount 後 V and the total injection slurry amount qq, indicating the total injection slurry amount The solid line Lq and the dashed-dotted line Lv indicating the total discharge amount may begin to deviate, and the balance between the injected slurry amount and the discharge amount may be lost.

In such a case, if construction continues as it is, it is considered that the broken line Lv indicating the change in the amount V of earth removal and the broken line Lδ indicating the displacement change like the dashed line after time tn1 in FIG. It is judged that "displacement will occur largely", and construction is interrupted _.

  Then, the injection of the solidifying material slurry from the injection rod 2 is stopped, the injection rod 2 in the drilled hole is withdrawn to the ground, and the cause of the imbalance between the earth removal amount V and the injection slurry amount q is investigated.

  As a result of the investigation, if there is no cause in the drilling water, for example, the soil adheres to the soil push-up plate 6 of the injection rod 2 and becomes a large lump, and if this causes the drilling hole to be blocked. After removing the cause by removing the lump of the soil, etc., the tip of the injection rod 2 is returned again to the stop position (depth at time tn1), and then the construction process is resumed.

  On the other hand, when there is a cause in the drilling water, for example, when it is considered that the soil is not placed on the soil lifting plate, the opening degree of the electromagnetic valve 28v of the high concentration thickener tank 28 is adjusted. The viscosity of the thickener is increased to make viscous drilling water, this viscous drilling water is sent to the pumping hose 9, and while the injection rod 2 is sprayed, the drilling hole is re-drilled. , The tip of the injection rod 2 is returned to the stop position (depth at time tn1). The drilling process at this time is called "auxiliary drilling process".

  And after stopping injection of viscous drilling water, it switches to injection of a solidification material slurry, and restarts a creation process. That is, the solidifying material slurry is jetted from the injection rod 2 and pulled up to the ground while being rotated, thereby forming a cylindrical improved body 15.

  At this time, as shown in FIG. 6, after the reopening time tp, it is confirmed that the dashed-dotted line Lv indicating the earth removal amount has come along the solid line Lq indicating the injection amount of the solidifying material slurry, and finally the time The total earth removal amount VV and the total injection slurry amount qq at tm are almost equal (ΣV Σ q q), and the earth removal rate can be secured to almost 100%.

  For this reason, the dashed-dotted line Lδ indicating the amount of displacement started to increase at the generation interruption time tn1, but decreased after the generation resumption time tp, and finally the displacement amount δδ at the time tm could be suppressed to almost zero. . Therefore, the displacement of the ground to be improved can be prevented by constructing in this way.

A second embodiment of the present invention will be described, but the difference with the first embodiment is the method of determining the viscous drilling water (omission of the test construction, simplification).
(1) Omission of test construction When uniformity of the whole improvement object ground is high from soil column figure and soil quality test results and the optimum concentration of thickener can be predicted empirically (for example, in the case of adjacent work area of the construction etc. ) May set the optimum concentration of the above-mentioned empirical thickener as the concentration of viscous drilling water.

(2) Simplification of the test construction Instead of performing the test construction three times, the test construction may be performed only once to determine the viscosity drilling water of the optimum concentration.

  When viscous drilling water is determined according to the above (1) and (2), when the balance between the total earth removal amount and the total injected slurry amount is broken in the main construction, the above-described procedure according to the first embodiment is used. Continue construction using viscous drilling water.

  In the first embodiment, the case where the thickener concentration of the viscous drilling water is changed in the auxiliary drilling step in the forming step is described, but also in the drilling step, the ground surface of the drilling water in the drilling is It is also possible to predict the discharge condition in the construction process by observing the outflow condition to the ground, the fine particle mixing condition of the soil in the disturbed area, and the flow condition, so it is expected that the discharge will be small. In some cases, the thickener concentration of the drilling water may be changed in the same manner as in the above-mentioned formation process.

  In the first embodiment, the case where normal drilling water is used at the beginning of the construction was described, but from the beginning of the construction, viscous drilling water having a thickening action (reference viscosity drilling water) is used as the drilling water. It is good. In this case, in the auxiliary drilling step in the construction step, in order to change the thickener concentration of the reference viscosity drilling water according to the soil removal condition, a high concentration thickener is added to the reference viscosity drilling water The solution is titrated and mixed to make viscous drilling water (high concentration viscous drilling water) having a concentration higher than that of the above standard viscous drilling water, and by using the high concentration viscous drilling water The total discharge volume per improved body can be made to substantially match the total injected slurry volume.

2 Single-tube type injection rod 3 Drilling blade (earth auger)
5 Stirring blade 6 Spiral soil lifting disk 7 Air gap 10 Injection nozzle 11 Soft ground 14 Solidifying material slurry 15 Improved body 16 Disturbing portion 17 Soil removal

Claims (5)

A drilling blade is provided at the tip of the injection rod, a stirring blade is provided above the cutting blade, and a soil push-up plate is provided near the top of the stirring blade to inject water for drilling to the planned depth. While drilling, the drilling process of drilling a hole and forming the drilling hole, the injection rod is withdrawn to the ground, and then inserted into the drilling hole and re-boring process of returning the bottom part, and the injection rod is rotated and pulled out The soil is provided close to the upper portion of the solidifying material slurry injection port of the injection rod while high pressure injection of the solidifying material slurry into the ground and cutting and mixing the outside of the stirring blade with the energy of the solidifying material slurry The uplifting board pushes up disturbed soil in the vicinity of the jet nozzle upward to form a space under the soil uplifting board, and the mixed soil mixed with the solidifying material slurry is absorbed into the space, and a circle is formed in the ground Build a columnar improvement And Construction step of, in ground improvement method provided with,
When the balance between the amount of excavated soil and the amount of injected slurry is broken at the time of spraying water in the auxiliary drilling process during the drilling process or the formation process, a high concentration thickener solution is titrated and mixed with the drilling water. To be
The high concentration thickener liquid can be sent into the common pipe by the grout pump which can finely adjust the flow rate from the high concentration thickener liquid tank when water is supplied by the high pressure pump, and the upstream side of the high pressure pump Has a thickening effect on the drilling water by mixing high concentration thickener liquid in the drilling water so as to reach the target concentration of the thickener in the titration mixing method of combining with the drilling water at any flow rate A ground improvement method characterized by using a viscous drilling water and making the total amount of soil removal per one improved body substantially equal to the total amount of injected slurry.   The thickener concentration of the viscous drilling water having the thickening action is set by conducting test construction so that the soil removal rate on the ground to be improved is about 100%. Ground improvement method described in 1. A drilling blade is provided at the tip of the injection rod, a stirring blade is provided above the cutting blade, and a soil push-up plate is provided near the top of the stirring blade to inject water for drilling to the planned depth. While drilling, the drilling process of drilling a hole and forming the drilling hole, the injection rod is withdrawn to the ground, and then inserted into the drilling hole and re-boring process of returning the bottom part, and the injection rod is rotated and pulled out The soil is provided close to the upper portion of the solidifying material slurry injection port of the injection rod while high pressure injection of the solidifying material slurry into the ground and cutting and mixing the outside of the stirring blade with the energy of the solidifying material slurry The uplifting board pushes up disturbed soil in the vicinity of the jet nozzle upward to form a space under the soil uplifting board, and the mixed soil mixed with the solidifying material slurry is absorbed into the space, and a circle is formed in the ground Build a columnar improvement And Construction step of, in ground improvement method provided with,
At the time of drilling water injection in the auxiliary drilling process during the drilling process or the formation process, the viscous drilling with a thickening action by thickening the drilling water by titrating and mixing the high concentration thickener liquid with the drilling water To be water,
From the beginning of construction, viscous drilling water having a thickening action as drilling water is used as reference viscous drilling water, and in the auxiliary drilling process in the construction step, the reference viscous drilling water according to the soil removal condition. In order to change the thickener concentration of the above, by mixing the high concentration thickener liquid with the above-mentioned standard viscosity drilling water by titration, it is possible to use a drilling water having a concentration higher than that of the above-mentioned standard viscosity drilling water The ground improvement method characterized by making the total amount of earth removal per one improvement body almost correspond to the total amount of the injected slurry.   4. The ground according to claim 3, wherein the thickener concentration of the reference viscosity drilling water is set by conducting test construction so that the soil removal rate in the ground to be improved is about 100%. Improvement method. A drilling blade is provided at the tip of the injection rod, a stirring blade is provided above the cutting blade, and a soil push-up plate is provided near the top of the stirring blade to inject water for drilling to the planned depth. While drilling, the drilling process of drilling a hole and forming the drilling hole, the injection rod is withdrawn to the ground, and then inserted into the drilling hole and re-boring process of returning the bottom part, and the injection rod is rotated and pulled out The soil is provided close to the upper portion of the solidifying material slurry injection port of the injection rod while high pressure injection of the solidifying material slurry into the ground and cutting and mixing the outside of the stirring blade with the energy of the solidifying material slurry The uplifting board pushes up disturbed soil in the vicinity of the jet nozzle upward to form a space under the soil uplifting board, and the mixed soil mixed with the solidifying material slurry is absorbed into the space, and a circle is formed in the ground Build a columnar improvement And Construction step of, in ground improvement method provided with,
At the time of drilling water injection in the auxiliary drilling process during the drilling process or the formation process, the viscous drilling with a thickening action by thickening the drilling water by titrating and mixing the high concentration thickener liquid with the drilling water To be water,
In the auxiliary drilling process during the formation process, when the amount of soil removal is smaller than the injection amount of the solidified material slurry, the injection of the solidified material slurry is stopped to draw out the injection rod, drilling water or reference viscosity drilling water The high concentration thickener liquid is titrated and mixed, and the thickener concentration of the drilling water or the reference viscosity drilling water is changed and re-drilling while injecting, and the tip of the injection rod is returned to the stopped position. Ground improvement method characterized by having a process.

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