JP4252069B2 - Ground strengthening method - Google Patents

Description

  The present invention relates to a ground strengthening method, in particular, it is created by valley filling embankment that fills the original ground of the valley, and is applied to ground strengthening of residential land, factory construction land, or land used for roads, etc. Landslide disasters during heavy rainfall can be prevented.

  In recent years, embankment embankment is generally performed to fill land on the valley ground to secure land such as residential land, factory construction site, or road. The embankment created by the valley filling embankment is different in nature from the ground and the embankment, and the ground is much harder than the embankment, making it difficult for groundwater to pass through. It is predicted that

  For this reason, the shear strength of the boundary surface between the original ground and the embankment is small, and when an external force is applied due to an earthquake or the like, the entire embankment tends to landslide at the interface with the original ground.

  In particular, after heavy rain, a large amount of rainwater that has penetrated into the embankment is expected to flow from the upstream to the downstream as groundwater on the original soil surface, so that the embankment is saturated. This may cause osmotic pressure, increase in embankment weight, decrease in ground strength, etc., and may develop into a large-scale landslide disaster near the boundary surface.

  Conventionally, as a method for preventing such a landslide disaster, for example, a method illustrated in FIGS. 12A and 12B has been performed. In the method illustrated in FIG. 12A, a retaining wall 21 is constructed in a stepped shape in the upstream direction on the downstream side of the embankment floor 20, and an anchor or drain hole 22 is constructed in each embankment floor 20 from each retaining wall 21. In the method illustrated in FIG. 12B, a water collecting well 23 is provided in the embankment floor 20, and a horizontal boring hole 24 for collecting water is cut into the embankment ground 20 from the water collecting well 23. It is a method of making holes.

Patent 2509005

  Although these methods could strengthen the ground of the embankment itself, it was insufficient to prevent the landslide disaster of the entire embankment that occurred near the boundary between the original ground and the embankment. In addition, there are known a consolidation method for improving a part of the ground by injecting a solidifying material into the embankment and a drainage method for drilling a drain hole.

  However, the consolidation method has the effect of storing groundwater due to the imperviousness of the ground, and workability on unstable slopes and work within a living area such as a house on the slope is a normal living environment. This is not preferable because it interferes with this. In addition, the method of drilling the drainage hole causes the same problem during the work for providing the drainage hole.

  In addition, each method is insufficient as a ground countermeasure at the boundary between the original ground and the embankment, which is particularly problematic, and cannot prevent landslide of the entire embankment along the original ground surface. Met.

  The present invention has been made to solve the above problems, and in particular, provides a ground strengthening method capable of preventing the landslide of the entire embankment that occurs near the boundary surface between the original ground and the embankment. Objective.

  The ground strengthening method according to claim 1 is characterized in that a plurality of bore holes are provided in the boundary surface between the original ground and the embankment in the embankment near the boundary between the original ground and the embankment formed on the original ground. A ground improvement portion that is continuous in the inclination direction of the boundary surface and is drilled in a plurality of rows in a direction orthogonal to the inclination direction of the boundary surface, and a solidifying material is injected into the boring hole to continue in the inclination direction of the boundary surface. It is characterized by forming.

  The present invention is a ground strengthening method for embankment that is particularly likely to cause landslide due to the difference in ground properties, and an embankment that is formed by embankment on the original ground that forms a slope, The embankment is stabilized by forming, in a plurality of rows, a plurality of ground improvement portions that are continuous in the inclination direction of the original ground at the boundary portion.

  In this case, the ground improvement portion may be formed continuously in the inclination direction of the original ground, or may be formed by a predetermined length at predetermined intervals, and further formed only on the upstream side and the downstream side. May be. In addition, the diameter and interval of the ground improvement parts, and the solidification material can be appropriately determined according to the ground properties of the original ground and the embankment.

  The ground strengthening method according to claim 2 is a ground strengthening method of a valley fill land that has been created by embankment in a valley, and a plurality of ground strengthening methods in the vicinity of the boundary surface between the original ground and the valley fill land Are drilled in a plurality of rows in a direction perpendicular to the direction of inclination of the boundary surface, and solidified material is injected into the borehole. Thus, a ground improvement portion that is continuous in the inclination direction of the boundary surface is formed.

  In the present invention, the ground created by the so-called valley filling embankment is particularly prone to landslides in the whole embankment because groundwater often flows at the boundary between the original ground and the embankment. Therefore, a ground improvement portion is formed in the boundary portion to prevent landslide in the boundary portion.

  The ground reinforcing method according to claim 3 is the ground reinforcing method according to claim 1 or 2, wherein the boring hole is drilled by induction bending boring.

  The inductive bending boring used here is equipped with a device that senses position information on the boring head, receives this position information on the ground, operates the boring head based on the display on the boring work panel, Or it is an apparatus which can operate the directionality of a boring with a gyro.

  By using inductive bending boring for boring, the boring hole can be drilled very efficiently along the vicinity of the boundary surface between the original ground and the embankment. This is because the number of bores and the bore length for the drainage area of the slope can be reduced, and the drainage effect can be ensured.

  The ground reinforcement method according to claim 4 is the ground reinforcement method according to any one of claims 1 to 3, wherein the ground improvement portion is formed over a certain range on the downstream side and / or upstream side of the original ground. It is characterized by.

  The present invention enables rational and economical ground strengthening by eliminating wasteful use of solidification material by forming ground improvement sections limited to a certain range on the upstream and downstream sides according to the ground conditions. It is a thing.

  The ground strengthening method according to claim 5 is the ground strengthening method according to claim 4, wherein the upstream ground improvement portion is formed in a borehole formed by bending or straight boring in the embankment ground upstream of the boundary surface. It is characterized in that it is formed by injecting a caking material into the material or by a stirring and mixing method or a high pressure injection method. The ground stabilization method according to claim 4.

  In addition to the solidified material injection method using curved boring, solidified material injection method using vertical boring or oblique boring, or agitation mixing instead of the injection method. A construction method or a high-pressure injection injection method may be used. In addition, if upstream workability is good, it is sufficient to solidify outside the living area, and if it is solidified upstream, even if it is not consolidated in line, there is no worry of storage, and the surface There is an effect that permeation of water downstream can be blocked by its water tightness.

  The ground reinforcement method according to claim 6 is the ground reinforcement method according to any one of claims 1 to 5, wherein the ground improvement portion between the ground improvement portion and the ground improvement adjacent to the direction orthogonal to the inclination direction of the boundary surface is provided. In the embankment near the boundary surface between the ground and the embankment, drainage holes are formed in the inclination direction of the interface.

  In particular, the present invention is a very effective method for preventing landslide disasters during heavy rains. In general, during and after heavy rains, the embankment is in a saturated state and is prone to landslide destruction. By draining to the ground, it is possible to prevent large-scale landslide disasters by avoiding saturation of the embankment.

  The drain hole can be easily formed by inserting a perforated pipe provided with a number of drain holes in a pipe such as a PVC pipe, a steel pipe or a corrugated pipe. Further, the drain hole may be drilled in a state meandering in an S shape, for example, in the inclination direction of the ground.

  The ground strengthening method according to claim 7 is the ground reinforcing method according to claim 6, wherein the drain holes are formed between the ground improvement portions.

  The ground reinforcement method according to claim 8 is the ground reinforcement method according to claims 1 to 7, wherein a retaining wall is constructed on the downstream side portion of the embankment. In this case, the retaining wall can be constructed by an RC structure, a masonry structure in which stones, concrete blocks, or the like are stacked, or a reinforced soil retaining wall.

  The ground strengthening method according to claim 9 is the ground reinforcing method according to any one of claims 1 to 7, wherein an anchor is constructed on the embankment and the tip of the anchor is fixed on the original ground. It is. In this case, for example, a reinforcing bar anchor (nailing anchor) or the like can be used in addition to a normal ground anchor or an anchor using prestress.

  According to this construction method, the strength of the embankment is directly reinforced by forming a kind of synthetic reinforced earth block by placing many rod-shaped reinforcements, mainly reinforcing bars, steel pipes, shaped steel, strips, etc. in the embankment. be able to.

  In particular, the present invention can stabilize the ground by preventing the landslide of the embankment in advance by forming a ground improvement part at the boundary between the original ground and the embankment and strengthening the boundary of the embankment. it can. Moreover, the stabilization of the embankment can be further enhanced by forming a drainage hole in the boundary portion together with the ground improvement part to forcibly drain the groundwater.

  In addition, the drainage hole is drilled at the boundary between the original ground and the embankment by using induction bending boring, so that the borehole is drilled from outside the living area on the slope, and the drainage hole is formed. By injecting the solidifying material into the borehole, construction can be performed without invading the living area, and drainage can be performed easily and effectively with a small number of bores and an extended bore.

  FIGS. 1A and 1B show a built-up residential land created by embankment on an inclined ground surface. A embankment ground 2 is created on the original ground 1. In addition, a plurality of ground improvement portions 3 are formed in a plurality of rows along the inclination direction of the original ground 1 at the boundary portion A between the original ground 1 and the embankment ground 2.

  The ground improvement unit 3 is continuous in the inclination direction of the original ground 1 along the boundary surface between the original ground 1 and the embankment 2 and is arranged in a plurality of rows at predetermined intervals in a direction orthogonal to the inclination direction (gradient direction). Is formed.

  The ground improvement part 3 drills a borehole in the boundary part A of the embankment ground 2 from the downstream side of the original ground 1 to the upstream side, and injects a solidified material into the borehole to provide a certain range of ground around the borehole. It is formed by solidifying over.

  As described above, the ground improvement portion 3 having strength and water tightness is continuously arranged along the slope of the original ground 1, and as a result, a drainage zone is formed between them, and a consolidation effect and a drainage effect are obtained at the same time. Since the part 3 stores groundwater and does not hinder drainage, stability of the slope ground at the boundary portion A can be improved.

  2 (a) and 2 (b) show the downstream side of the boundary portion A between the original ground 1 and the embankment 2 and the above ground improvement portion 3 is in a certain range (length) in the inclination direction of the original ground 1. 3 (a) and 3 (b) show the ground improvement described above on both the downstream side and the upstream side of the boundary portion A between the original ground 1 and the embankment 2. An example in which the part 3 is formed over a certain range in the inclination direction of the original ground 1 is shown.

  Note that the upstream ground improvement section 3 is formed by solidifying a part of the upstream ground by an arbitrary method, so that only the ground sliding force of the area acts, so the downstream consolidated area As a result, the safety factor against sliding can be increased.

  In this case, as a method of forming the ground improvement portion 3 by solidifying a part of the ground on the upstream side, straight boring such as vertical boring and oblique boring is performed without using a solidified material injection method using curved boring. You may utilize the method of inject | pouring a solidification material using, a stirring mixing construction method, a high-pressure injection injection construction method, etc.

  In addition, if upstream workability is good, it is sufficient to solidify outside the living area, and if it is solidified upstream, even if it is not consolidated in line, there is no worry of storage, and the surface There is an effect that permeation of water downstream can be blocked by its water tightness.

  Further, in FIGS. 4A and 4B, a plurality of the ground improvement portions 3 described above are formed at the boundary portion A between the original ground 1 and the embankment 2, and between the various ground improvement portions 3 and 3. An example in which the drain holes 4 are continuously formed in the inclination direction of the original ground 1 is shown.

  The drain hole 4 is continuously formed in the inclination direction of the original ground 1 at the boundary portion A between the original ground 1 and the embankment ground 2 similarly to the ground improvement portion 3.

  5 (a) and 5 (b), the above ground improvement part 3 is formed over a certain range in the inclination direction of the original ground 1 on the downstream side portion of the boundary portion A between the original ground 1 and the embankment 2; In addition, an example in which the drainage holes 4 described above are continuously formed in the inclination direction of the original ground 1 between the various ground improvement portions 3 and 3 is shown.

  The drain hole 4 is formed by drilling a boring hole in the boundary portion A of the embankment 2 from the downstream side of the original ground 1 to the upstream side, and inserting a perforated pipe into the boring hole. In addition, as the perforated pipe, a steel pipe, a vinyl chloride pipe, a corrugated pipe or the like in which a large number of drain holes are formed is used.

  As described above, the boundary portion A is reinforced by forming a plurality of ground improvement portions 3 in a plurality of rows in the inclination direction of the original ground 1 at the boundary portion A between the original ground 1 and the embankment 2. A can prevent the entire embankment 2 from landslide.

  In addition, by forming a drainage hole 4 between the ground improvement parts 3 and 3 and forcibly draining the groundwater at the boundary portion A, the groundwater level is lowered and the saturation of the embankment 2 is avoided. In addition, the stabilization of the ground at the boundary portion A can be enhanced, and in particular, landslide disasters during and after heavy rain can be prevented.

  In addition, the drainage holes at the boundary between the original ground and the embankment are continuously formed in the inclination direction of the original ground along the vicinity of the boundary between the original ground and the embankment. This method is extremely effective as a preventive measure, and in general during and immediately after heavy rain, the embankment is in a saturated state and is prone to landslide destruction, but the embankment is saturated by forcibly draining groundwater. By avoiding this, large-scale landslide disasters can be prevented.

  The drain hole can be easily formed by inserting a perforated pipe provided with a number of drain holes in a pipe such as a PVC pipe, a steel pipe or a corrugated pipe. Further, the drain hole may be drilled in a state meandering in an S shape, for example, in the inclination direction of the ground.

Next, the construction procedure of the ground reinforcement method of the present invention will be described.
First, as shown in FIGS. 7A and 7B, the boring hole 5 is drilled by boring the boundary portion A between the original ground 1 and the embankment 2. In this case, the induction-type curved boring is used for boring, and the boring hole 5 is continuous from the downstream side of the original ground 1 to the upstream side in the embankment 2 along the boundary surface between the original ground 1 and the embankment 2. Then drill holes.

  Specifically, a drilling rod 6b having a drill head 6a for embankment excavation and a tapered blade 6b for changing the excavation direction as shown in the figure is inserted into the casing 7, and the drill head 6a is inserted into the embankment 2 While rotating, push in the upstream direction to perform boring.

  At that time, it is possible to stop the rotation of the boring rod 6 and change the direction of the boring by changing the direction of the tapered blade 6b. When the boring hole 5 reaches the upstream side, only the casing 7 is left and the boring rod 6 is pulled out.

  Next, as shown in FIG. 8A, the casing (the casing is omitted in FIG. 8A) is pulled out while the injection tube 8 is inserted into the casing of the bore hole 5. The injection tube 8 is composed of, for example, an outer tube 9 and an inner tube 10 inserted into the outer tube 9 as shown in the figure, and a distal support valve 9a made of a rubber sleeve or the like is provided at the tip of the outer tube 9. Discharge ports 9b are formed at predetermined intervals in the longitudinal direction and the circumferential direction of the outer tube 9, and expansion packers 11 and 11 are attached to both sides of each discharge port 9b.

  The expansion packers 11 and 11 are expanded by a fluid (air or liquid) or a solidified liquid fed from the ground via the injection pipe 12a, and strongly press the hole wall of the boring hole 5, thereby causing the outer tube 9 to be bored into the boring hole. 5 and a sealed space 13 is formed between the boring hole 5 and the outer tube 9. The sealed space 13 in this case is formed by the hole wall of the boring hole 5, the outer tube 9, and the left and right expansion packers 11 and 11.

  On the other hand, expansion packers 14 and 14 are attached to the distal end portion of the inner tube 10 at predetermined intervals. The expansion packers 14 and 14 are expanded by a fluid or a solidified liquid sent from the ground via the injection pipe 12b in the same manner as the expansion packers 11 and 11, and strongly press the inner wall of the outer tube 9 to thereby press the inner tube 10. While being fixed in the outer tube 9, a sealed space 15 is formed between the outer tube 9 and the inner tube 10. In this case, the sealed space 15 is formed by the outer tube 9, the inner tube 10, and the left and right expansion packers 14 and 14.

  In such a configuration, in order to inject the solidified material into the embankment board 2 around the borehole 5 by the injection pipe 8, first, the outer pipe 9 of the injection pipe 8 is inserted into the borehole 5. Then, each expansion packer 11, 11 of the outer tube 9 is inflated by injecting a fluid or a consolidated liquid into the expansion packer 11, thereby fixing the outer tube 9 in the borehole 5, and A sealed space 13 is formed between the borehole 5.

  Next, the inner tube 10 is inserted into the outer tube 9, and each expansion packer 14, 14 is inflated by injecting air or liquid into the expansion packer 14. And a sealed space 15 is formed between the outer tube 9 and the inner tube 10.

  Next, the solidified material is fed into the sealed space 15 through the injection pipe 12c at a high pressure. The solidified material fed into the sealed space 15 is pushed into the sealed space 13 through the discharge port 9b of the outer tube 9 and injected into the embankment 2 around the sealed space 13.

  The outer tube 9 and the inner tube 10 can be freely moved again by removing the air or liquid injected into the expansion packers 11 and 14 and contracting the expansion packers 11 and 14 respectively.

  In this case, since the solidified material is injected into the ground around the sealed space 13, the ground improvement portion formed by the injection of the solidified material at one location is formed in a spherical shape, but the injection pipe 8 is connected upstream of the original ground 1. The ground improvement part 3 can be continuously formed from the upstream side of the original ground 1 to the downstream side by repeatedly injecting the solidified material while gradually pulling it from the side toward the downstream side.

  In the example of FIG. 8A, the solidified material is simultaneously injected into the plurality of sealed spaces 13 by one injection tube 12c. However, the plurality of injection tubes 12c are provided in the inner tube 10. It is also possible to insert the solidified material into each sealed space 13 through each injection tube 12c at the same time. Furthermore, it is possible to simultaneously inject the solidified material into the plurality of boring holes 5 using a plurality of injection tubes 8. By constructing in this way, the ground improvement part 3 can be formed very efficiently.

  When injecting solidified material such as mortar into the expansion packer 11 instead of injecting air or liquid, the outer tube 9 is not collected and is buried in the boundary portion A between the original ground 1 and the embankment 2 and embankment. It can be used as a reinforcing material for the ground 2.

  Although not shown in the above, the ground may be consolidated by pulling out the boring rod while injecting the injecting liquid from one or a plurality of flow paths in the boring rod of the bent boring, or directly from the outer tube. An injection solution may be injected, or the ground may be consolidated by pulling out the outer tube while injecting from the outer tube.

  The drain hole 4 can be formed by cutting a boring hole 5 and then inserting a perforated pipe (not shown) into the boring hole 5.

  FIG.8 (b) shows the other method of inject | pouring a solidified material into the embankment board 2 around the boring hole 5, and in this case the injection pipe 8 is as the outer pipe | tube 9 demonstrated in FIG. After using the one without the expansion packer 11 and inserting the outer tube 9 into the borehole 5, the gap filler 16 is filled between the borehole 5 and the outer tube 9.

  Then, the solidified material is fed into the sealed space 15 through the injection pipe 12c. The solidified material fed into the sealed space 15 breaks through the gap filler 16 from the discharge port 9b of the outer tube 9 and is injected into the embankment board 2 around the discharge port 9b.

  Also in this method, by repeatedly injecting the solidified material while gradually pulling out the injection pipe 8 from the upstream side of the original ground 1 to the downstream side, the ground improvement unit 3 can move from the upstream side of the original ground 1 toward the downstream side. It can be formed continuously.

  Alternatively, the gap filling material 16 may be filled in the boring hole 5 first, and then the outer tube 9 may be inserted into the boring hole 5. For example, low-strength cement bentonite can be used for the gap filler 16.

  Similarly to the case shown in FIG. 8A, the solidified material may be simultaneously injected into the plurality of sealed spaces 15 by one injection tube 12 c, or the plurality of injection tubes 12 c are inserted into the inner tube 10. It is also possible to insert the solidified material into each sealed space 15 through each injection tube 12c at the same time.

  Further, a three-dimensional multi-point injection method can be used by using a plurality of injection pipes 8 and simultaneously injecting a solidified material into the plurality of boring holes 5.

  The three-dimensional multi-point injection method is a patented invention (Patent No. 3724644) owned by the present applicant. Briefly speaking, a plurality of injection pipes having discharge ports are formed into a plurality of injection pipes in the ground. It is a ground injection method that is buried at a point and multiple ground injection materials are simultaneously injected from the outlets of each injection pipe through these injection pipes. A multi-injection injection device having a large number of unit pumps to be controlled is used, and the large number of unit pumps are connected to a plurality of injection pipes through a conduit. It is characterized by the fact that multiple injections are made through injection points in the ground.

  The present construction method also includes a storage tank for storing the ground improvement material, a multi-continuous injection apparatus connected to the storage tank, and a plurality of injection pipes having discharge ports. It is equipped with a number of unit pumps that are operated by independent drive sources and controlled by a centralized management device. The injection pipe is embedded in a plurality of injection points on the ground, and each is connected to each unit pump through a conduit. Further, the multiple unit pumps are independent and each include a rotational speed transmission controlled by a centralized control device, and the conduit includes a flow pressure detector.

  Then, a flow rate and / or pressure data signal from the flow rate pressure detector is transmitted to a central control device, and the ground improvement material in the storage tank is operated at any injection speed, injection pressure and injection amount by the operation of each unit pump. Thus, it can be pumped to each injection tube, and multiple points can be simultaneously injected into the ground from a plurality of discharge ports.

Next, the examination result of the ground reinforcement method of this invention is demonstrated.
Embankment height 5.0 m
Embankment length 200.0 m
Embankment width 50.0 m
Embankment inclination angle 10.0 degrees Unit volume weight of embankment γt = 17KN / m ³
Model ground Fig. 9 (a), (b)

  9 (a) and 9 (b), the embankment portion α attempts to slide down along the vicinity of the boundary surface with the original ground β due to an external force acting due to an earthquake or the like. This is referred to as a force (hereinafter referred to as “sliding shear force”) W · sin θ that causes the slip to act on the sliding surface. On the other hand, a force (hereinafter referred to as “shear resistance force”) τ · L that acts to prevent this acts on the sliding surface. It is assumed that the sliding shear force W · sin θ and the shear resistance force τ · L are in a balanced state (limit state). That is, the ground strengthening method of the present invention was examined on the assumption that the safety factor Fs = 1.0.

In FIG. 9A, assuming that the sliding shear force W · sin θ and the shear resistance force τ · L are balanced,
Fs = τ · L / W · sinθ = 1.0 (Fs safety factor) ...... Formula 1
The shear resistance τ of the embankment lower boundary surface is obtained from Equation 1.

τ · L / W · sin θ = 1.0
τ · L = τ · 203KN / m
= 203 · τKN / m
W · sin θ = 200.0 m × 5.0 m × 17 KN / m ³ × sin 10 °
= 17000 x 0.17365
= 17000 x 0.174
= 2.958 KN / m
From Fs = 1.0 τ · L / W · sin θ = 203 · τ / 2.958
= 1.0
Therefore, shear resistance τ = 2.958 / 203
= 14.6KN / m ²
It becomes.

  As mentioned above, the current state where sliding shear force and shear resistance force are balanced with safety factor Fs = 1.0 is strengthened by chemical solution (solidification material) injection to increase the safety factor and stabilize the ground. And

  For the chemical injection, induction bending boring is used, and the three-dimensional multi-point injection method is adopted in the injection method shown in FIG. 8 (b), and the solution type permanent grout (active silica colloid “Perma Lock” reinforced soil engineering ( Registered trademark), or suspension-type permanent grout (registered trademark of ultrafine composite silica “hybrid silica” reinforced soil engineering Co., Ltd.) can also be used.

  In the following examination, a permanent grout [a high-strength active silica colloid “Permalock High”, which can obtain a permanent improvement effect, was used for the injection material in consideration of the purpose of improvement (see Table 1).

Table 2 shows the shear resistance τ ₁ of the improved ground by the three-dimensional multi-point injection method. In the case of ground improvement by a three-dimensional multi-point injection method using curved boring, the ground was strengthened for a total of 100 m, 50 m downstream and 50 m upstream, considering the accuracy and performance of curved boring.

  In addition, from the performance of the three-dimensional multipoint injection method, the improved body from one nozzle was examined as a spherical improved body having a diameter of 2.0 m, and the improvement range was examined.

Consider a case where the safety factor Fs is improved to 1.5.
Calculate the improved area ratio μ.
From the formula of Fs = τ · L / W · sin θ = 1.5 [μ × τ ₁ + (1−μ) × τ] × 203 / 2.951 = 1.5
μ = 2.958 × 1.5−14.6 × 203 / 203τ ₁ −2.964
= 1.473 / 203τ ₁ -2.964 Equation 2
When μ is calculated by substituting τ ₁ of the improved ground into Equation 2, the result is as shown in Table 3, resulting in Fs = 1.75 to 1.8.

  From the above, the improved area ratio of ground reinforcement by the chemical solution injection method (three-dimensional multi-point injection method) was set as shown in Table 4. And the improvement range in a model ground was examined from the examination result, and it became as follows (refer to Drawing 10 (a) and (b) for the improvement range). Table 5 shows the improvement rate, the improvement area, and the number of injection holes when the safety factor Fs is 1.5.

Model ground area S = 50.0 × 203.0 = 10.150.0 m ²
Necessary improvement area S ₁ = S × μ
The number of holes in the injection hole (ground improvement part) was calculated with a length of 50.0 m per hole and an improved width of 2.0 m according to the characteristics of this construction method.
Improved area per hole Sg = 2.0 × 50.0 = 100.0 m ²

  Next, a description will be given of the results of examinations in which the ground strengthening method by drainage hole construction is used in combination with the ground strengthening method by injecting the solidifying material.

Here, assuming that the shear resistance τ = 14.6 KN / m ^{2 at the} lower boundary of the embankment is improved by 70% due to the construction effect of the drain hole, the construction result area of the drain hole is 3 m wide × 50 m long (+ α ) / 1 drainage hole × 8 = 1200 m ² , multiplying this by 14.6 × 0.7 increases the shear resistance by 12264 KN and increases by 245 KN per unit width.

  Therefore, Fs = 245 KN / 2958 KN / m = 0.08. In addition, the installation interval of the drainage holes was set as shown in FIGS. 11A and 11B in consideration of the combined effect with the solidification material injection hole (ground improvement part).

Next, consider the time of an earthquake.
Fs = τ · L / W · sinθ + Kh · W · cosθ
Kh is the design horizontal seismic intensity The model ground has a relatively shallow embankment thickness of 5.0 m, so the design horizontal seismic intensity Kh was set to 0.16.
When Fs = 1.5 Fs = τ · L / W · sin θ + Kh · W · cos θ
= [Μ × τ ₁ + (1−μ) × τ] × 203 / W · sin θ
+ Kh · W · cosθ
= [0.05 × 250.0 + (1−0.05) × 14.5]
× 203 / 2.951 × 0.16 × 17.000 × cos10
= 5.33 / 5.630
= 0.95.

  If Fs = 0.08 of the increase due to drainage is added to this, Fs = 1.03. Although the above calculation is based on a simple design, it is sufficient to know the improvement effect.

  In addition, the improvement effect by drainage is the effect by increasing the effective stress between the soil particles due to the lowering of the groundwater level, and thereby the shear resistance of the embankment interface is improved by 70%, but basically There should be no problem. Moreover, naturally the effect of preventing liquefaction can be expected.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to stabilize the creation site such as a residential land or a factory construction site by a valley filling embankment created by embankment on a valley ground.

FIG. 2 shows a built-up residential land that is built by embankment on an original ground of an inclined land and a ground improvement portion is formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. Fig. 2 shows a built-up residential land that is formed by embankment on an original ground of an inclined land and has a ground improvement portion and a drain hole formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. FIG. 2 shows a built-up residential land that is built by embankment on an original ground of an inclined land and a ground improvement portion is formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. Fig. 2 shows a built-up residential land that is formed by embankment on an original ground of an inclined land and has a ground improvement portion and a drain hole formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. FIG. 2 shows a built-up residential land that is built by embankment on an original ground of an inclined land and a ground improvement portion is formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. Fig. 2 shows a built-up residential land that is formed by embankment on an original ground of an inclined land and has a ground improvement portion and a drain hole formed at a boundary portion, (a) is a longitudinal sectional view, and (b) is a partial plan view. (A), (b) is sectional drawing of the boundary part of the original ground and embankment which shows the motion of a boring rod. (A), (b) is a longitudinal cross-sectional view of the injection tube front-end | tip part which shows the injection method of a solidification material. A model ground is shown, (a) is a longitudinal cross-sectional view, (b) is a partial plan view. The model ground after ground reinforcement is shown, (a) is a longitudinal cross-sectional view, (b) is a partial plan view. The model ground after ground reinforcement is shown, (a) is a longitudinal cross-sectional view, (b) is a partial plan view. (A), (b) is a longitudinal cross-sectional view which shows an example of the conventional ground reinforcement method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Original ground 2 Embankment 3 Ground improvement part 4 Drain hole 5 Boring hole 6 Boring rod 6a Drill head 6b Tapered blade 7 Casing 8 Injection pipe 9 Outer pipe 9a Check valve 9b Discharge port 10 Inner pipe 11 Expansion packer 12a Injection pipe 12b Injection pipe 12c Injection pipe 13 Sealed space 14 Expansion packer 15 Sealed space

Claims (8)

In the embankment near the boundary surface between the original ground and the embankment created on the original ground , a plurality of boring holes are continued in the inclination direction of the interface between the original ground and the embankment , and the boundary A ground strengthening method comprising drilling holes in a plurality of rows in a direction perpendicular to the surface tilt direction, and injecting solidified material into the bore holes to form a ground improvement portion continuous in the tilt direction of the boundary surface. . A method for strengthening the ground of a valley-filled land created by embankment in a valley, wherein a plurality of boring holes are formed in the bank-ground near the boundary between the original ground and the valley-filled land. Are drilled in a plurality of rows in a direction perpendicular to the tilt direction of the boundary surface, and solidified material is injected into the borehole to continue in the tilt direction of the boundary surface. A ground strengthening method characterized by forming a ground improvement part.   The ground strengthening method according to claim 1 or 2, wherein the boring hole is drilled by induction bending boring. The ground reinforcement method according to any one of claims 1 to 3, wherein the ground improvement part is formed on the downstream side and / or the upstream side of the original ground. The ground improvement part on the upstream side is formed by injecting the consolidated material into the borehole drilled by curved boring or straight boring in the embankment upstream of the boundary surface , or by the stirring and mixing method or the high pressure injection method The ground stabilization method of Claim 4 characterized by the above-mentioned. Form drainage holes in the slope direction of the boundary surface in the embankment near the boundary surface between the ground and embankment between the ground improvement part and the ground improvement adjacent to the direction perpendicular to the tilt direction of the boundary surface. The ground reinforcement method according to any one of claims 1 to 5, wherein:   The ground reinforcing method according to any one of claims 1 to 6, wherein a retaining wall is constructed on the downstream side of the embankment.   The ground reinforcement method according to any one of claims 1 to 7, wherein an anchor is constructed on the embankment and the tip of the anchor is fixed on the original ground.

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