Shallow roadbed reaming grouting and small-aperture splitting grouting structure enhanced layout

Abstract

The utility model discloses a shallow roadbed reaming grouting and small-aperture splitting grouting structure enhanced layout, which is characterized in that a plurality of drill holes are divided into a plurality of rows and are arranged in a quincunx shape, the drill holes are drilled into an old pavement layer and an old road base layer, the drill holes are filled with soil in the roadbed layer for reaming, and small-aperture grouting holes are drilled in the middle positions of adjacent reaming holes; and splitting grouting is carried out. And compared with direct splitting grouting for reaming, the technology control difficulty is lowered, the construction efficiency is improved, a thick pile structure closely combined with the soil body can still be formed, new powerful support is formed for an old pavement structure, and the bending-tensile life of a base layer is remarkably prolonged.

Description

Technical Field

[0001] This utility model relates to the field of road engineering technology, specifically to a reinforced layout for shallow subgrade enlarged hole grouting combined with small-diameter splitting grouting. Background Technology

[0002] With socio-economic development and planning adjustments, a contradiction often arises between the thin pavement structure of early-built highways and the drastically increased traffic load on upgraded roads. Due to the high cost, long construction period, and significant traffic disruption associated with open-cut reinforcement, trenchless reinforcement solutions are becoming the general trend.

[0003] During the large-scale development of infrastructure in my country, soil grouting technology and soft soil replacement reinforcement have become very mature. Grouting reinforcement techniques such as steel pipe and sleeve valve pipe have been developed, as well as soil replacement techniques such as jet grouting piles and powder jet grouting piles. In terms of materials, cement (including micro-expansion), fly ash-cement, and geopolymers have been developed, solving the foundation bearing capacity problem of bridges and buildings, but none of these are suitable for treating shallow soil.

[0004] In addition, grouting reinforcement technology is also commonly used for the repair of damaged pavement structures. When dealing with cracked base courses and voids at the bottom of the base course, materials such as cement slurry are injected under pressure to re-harden the broken base course and fill the voids between the subgrade and the base course caused by long-term traffic subsidence. This effectively restores the bearing capacity of the pavement, but it cannot further enhance the bearing capacity of the pavement structure.

[0005] Due to reconstruction, expansion, or traffic planning adjustments, some roads that previously carried little or no traffic on their shoulders now face significantly increased traffic volumes after renovation. Adopting trenchless reinforcement techniques for these roads presents unprecedented challenges. Currently, there is a lack of structures capable of providing trenchless reinforcement holes in shallow subgrades to improve the flexural life of the base course. Utility Model Content

[0006] To address the shortcomings of existing technologies, this utility model provides a reinforced layout for shallow subgrade grouting with enlarged boreholes and small-diameter splitting grouting. In this technical solution, the borehole layout, combined with the corresponding grouting method, can significantly improve the bending service life of the subgrade.

[0007] A shallow subgrade reinforcement layout combining borehole enlargement grouting and small-diameter splitting grouting involves multiple rows of boreholes arranged in a quincunx pattern. The boreholes are driven into the existing pavement layer and subgrade. Enlargement is then performed within the boreholes in the fill subgrade. Small-diameter grouting holes are drilled between adjacent enlarged boreholes. During grouting, the enlarged boreholes are first grouted under no-pressure or low-pressure conditions. After the grout has initially solidified, splitting grouting is immediately performed along the small-diameter grouting holes, ultimately forming a coarse pile support structure tightly bonded to the soil beneath the pavement structure.

[0008] Preferably, the diameter of the drilled hole is 110-200mm, and the diameter of the enlarged hole is 250-500mm.

[0009] Preferably, the distance between the centers of adjacent boreholes in a row of boreholes is 100-150cm.

[0010] Preferably, the distance between the centers of adjacent drill holes is 35-130cm.

[0011] Preferably, the diameter of the small-diameter grouting hole is 60-80 mm.

[0012] The beneficial effects of this utility model are reflected in the following: By using a specific hole layout, setting the distance between holes, the diameter of the holes, and the diameter of the enlarged holes, and in conjunction with a specific grouting method, the bending life of the base layer can be significantly improved, meeting the requirements for bending life, while also meeting the construction requirements for construction space and reducing construction costs. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0014] Figure 1 This is a schematic diagram of the borehole distribution in this utility model;

[0015] Figure 2 This is a side cross-sectional view of drilling and reaming in this utility model.

[0016] In the attached diagram, 4 represents the grouting hole. Detailed Implementation

[0017] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this utility model pertains.

[0019] Example 1

[0020] like Figures 1-2As shown, this embodiment provides a shallow subgrade enlargement grouting and small-diameter splitting grouting structure reinforcement layout. Several boreholes are divided into multiple rows, and several boreholes are arranged in a quincunx pattern. The boreholes are driven into the old road surface layer and the old road base layer. The boreholes are enlarged from the inside of the boreholes in the fill road base layer. Small-diameter grouting holes 4 are drilled in the middle of adjacent enlarged boreholes.

[0021] During grouting, the enlarged hole is first grouted without pressure or at low pressure. After the grout has initially solidified, it is immediately split grouting along the small-diameter grouting hole, eventually forming a coarse pile support structure that is tightly bonded to the soil in the lower part of the pavement structure.

[0022] In this embodiment, the diameter of the drilled hole is 110-200mm, and the diameter of the enlarged hole is 250-500mm.

[0023] In this embodiment, the diameter of the drilled hole is 170mm, and the diameter of the enlarged hole is 300mm.

[0024] In this embodiment, the distance between the centers of adjacent boreholes in a row of boreholes is 100-150cm.

[0025] In this embodiment, the distance between the centers of adjacent drill holes is 35-130cm.

[0026] In this embodiment, the diameter of the small-diameter grouting hole 4 is 60-80mm.

[0027] In this embodiment, by using a specific hole layout, setting the distance between holes, the diameter of the holes, and the diameter of the enlarged holes, and combining this with a specific grouting method, the flexural life of the base layer can be significantly improved, meeting the flexural life requirements, while also meeting the construction space requirements and reducing construction costs.

[0028] Specifically as follows:

[0029] The method of grouting by enlarging the borehole without pressure or with low pressure, combined with fracturing grouting through small-diameter injection holes, is adopted.

[0030] Several boreholes are divided into multiple rows, and some boreholes are arranged in a quincunx pattern.

[0031] (1) At the middle position of the adjacent enlarged hole, drill a small diameter grouting hole 4 (Ф60-80mm). The depth of the grouting hole 4 is slightly deeper than the depth of the enlarged hole. Use a drill bit of the corresponding size to drill to the design depth in one go.

[0032] (2) Insert a large-diameter grouting pipe into the enlarged hole and inject cement grout (water-cement ratio 40-60%) into the enlarged hole until it is full;

[0033] (3) After the cement grout injected into the enlarged hole has completed its initial setting, pressure grouting is performed on the grouting hole. A small-diameter grouting pipe (Ф60-70mm) is inserted and the pipe is locked under pressure. Grouting is started (water-cement ratio 40-60%), and the pressure is maintained at 0.6-1.2MPa for 2-4 minutes. If the pressure continues to be higher than 1MPa, pressure grouting is terminated.

[0034] 1. Bending fatigue life calculated based on traffic volume

[0035] 1.1 Paving over old roads

[0036] Located in Guangdong Province, this project is a highway, with a starting point at K3534+000 and an ending point at K3594+896. The design service life is 15.0 years. Based on traffic volume OD survey analysis, the daily traffic volume of large passenger vehicles and freight vehicles at the cross-section is 4224 vehicles / day (30% of which are 2-axle, 6-wheel small trucks), with an annual traffic growth rate of 2.8%. The directional coefficient is taken as 55.0%, and the lane coefficient as 78.0%. Based on historical traffic data, this designed highway is classified as TTC4, and the vehicle type distribution coefficients are shown in Table 1.1-1.

[0037] Table 1.1-1 Vehicle Type Distribution Coefficient

[0038] Vehicle type Category 2 3 categories 4 categories 5 categories 6 categories 7 categories 8 categories 9 categories 10 categories 11 categories Vehicle type distribution coefficient (%) 28.9 43.9 5.5 0.0 9.4 2.0 4.6 3.4 2.3 0.1

[0039] Based on the survey and analysis of vehicle load conditions and historical data on adjacent highways in the road network, the proportions of non-full load and full load for various vehicle types were obtained, as shown in Table 1.1-2.

[0040] Table 1.1-2 Percentage of Vehicles Not Fully Loaded and Fully Loaded (%)

[0041] Vehicle type Category 2 3 categories 4 categories 5 categories 6 categories 7 categories 8 categories 9 categories 10 categories 11 categories Percentage of vehicles not fully loaded (%) 85.0 90.0 65.0 75.0 55.0 70.0 45.0 60.0 55.0 65.0 Percentage of vehicles fully loaded (%) 15.0 10.0 35.0 24.0 45.0 30.0 55.0 40.0 45.0 35.0

[0042] The design parameters for this pavement design are permanent deformation of the asphalt mixture layer and fatigue cracking of the inorganic binder layer. The equivalent design axle load conversion factors for unloaded and fully loaded vehicles under different design parameters are shown in Table 1.1-3.

[0043] Table 1.1-3 Conversion Factors for Equivalent Design Axle Load of Unloaded and Fully Loaded Vehicles

[0044]

[0045] The cumulative number of equivalent design axle loads corresponding to the permanent deformation of the asphalt mixture layer, calculated according to the formula, is 19,702,681, and the cumulative number of equivalent design axle loads corresponding to the fatigue cracking of the inorganic binder layer is 1,366,239,791. The cumulative traffic volume of large passenger vehicles and freight vehicles in the design lanes within the design service life of this highway is 12,122,825, classifying it as heavy traffic.

[0046] 1.2 Widening the newly constructed road surface

[0047] Highway grade: Expressway

[0048] Target reliability index: 1.65

[0049] Average daily traffic volume (vehicles / day) for both large passenger and freight vehicles in the initial year: 6467

[0050] Road surface design service life (years): 15

[0051] Period from opening to first rut repair (years): 8

[0052] Average annual growth rate of traffic volume: 2.82%

[0053] Directional coefficient: 0.55

[0054] Lane coefficient: 0.8

[0055] The proportion of integrated trucks: 68%

[0056] Semi-trailer trucks account for 22% of the total.

[0057] Average daily traffic volume (vehicles / day) for large passenger vehicles and freight vehicles in the initial design lane: 2845

[0058] The cumulative traffic volume of large passenger vehicles and freight vehicles in the design lanes within the design service life is 1.906074E+07, and the road surface design traffic load level is extra heavy traffic load level.

[0059] When verifying fatigue cracking of the asphalt mixture layer, the cumulative number of equivalent design axle loads applied to the design lane within the design service life is 4.370466E+07.

[0060] When verifying fatigue cracking of the inorganic binder stabilized layer, the cumulative number of equivalent design axle loads applied to the design lane within the design service life is 3.27842E+09.

[0061] When verifying the permanent deformation of the asphalt mixture layer, the cumulative number of equivalent design axle loads applied to the design lane within the period from the opening of the road to the first rut repair is 2.103807E+07.

[0062] When verifying the vertical compressive strain on the top surface of the roadbed, the cumulative number of equivalent design axle loads applied to the design lane within the design service life is 7.680584E+07.

[0063] 2. Bending tensile fatigue life of various structures and grouting methods

[0064] Table 2.1 shows the calculated flexural tensile stress at the bottom of the inorganic binder layer when the shoulder is retained at 1.25 meters and 1.75 meters, respectively, under load on the wheel track of the third lane. Because the retained shoulder is located far from the wheel track, the flexural tensile stress at the bottom of the inorganic binder layer is significantly lower than that under the new road surface when the shoulder is retained at 1.25 meters, while the flexural tensile life at the bottom of the layer with a 1.75-meter retention is equivalent to the flexural tensile life under the left wheel of the old road surface.

[0065] Table 2.1 Fatigue cracking calculation of inorganic binder layer under load in the third lane wheel track zone

[0066]

[0067] To investigate the impact of various grouting schemes on pavement life, the most unfavorable loading method was adopted (this loading method does not exist when the original 1.25m shoulder is retained) to compare the fatigue cracking life of the inorganic binder layer under different reinforcement schemes. The calculation results are shown in Table 2.2. As shown in the table, the scheme with 300mm enlarged holes and 40cm row spacing recorded the lowest flexural tensile stress at the base course and the highest flexural fatigue life. After adjusting the spacing to 80cm, the flexural fatigue life decreased significantly.

[0068] Table 2.2 Calculation results of fatigue crack life of inorganic binder layer

[0069]

[0070] To further compare the impact of grouting schemes on the bottom bending tensile stress of the road shoulder base at the most unfavorable location under actual loading conditions, calculations were performed for a shoulder retaining 225cm, with four rows of holes, three rows on the right side spaced 40cm apart, and the leftmost row spaced 65cm apart. The calculation results are shown in the table below. As can be seen from the table, enlarging the hole spacing provides a more significant reinforcement effect than reducing the spacing.

[0071] The 2.25-meter overlap is located directly below the double wheels on the third lane's wheel track. Without reinforcement, the flexural stress at the bottom of the layer would be very high, resulting in a flexural life less than half of the design life. Among all reinforcement options, the 300mm enlarged hole has the greatest effect on reducing flexural stress, even though its spacing is much larger than other options. It still achieves the required displacement life. The 70mm small-diameter, small-spacing reinforcement option has little impact on flexural stress, with a flexural life only two-thirds of the design life. While the 200mm enlarged hole option, with a smaller spacing than the 300mm option, still has a shorter flexural life than the 70mm hole option, it is significantly longer than the 70mm hole option.

[0072] 2.25m inorganic binder layer bottom tensile stress

[0073]

[0074] In the actual project implementation, to eliminate the weak edges of the base layer, a 200cm overlap was adopted. Based on the preliminary calculations and the results of the test road at Huizhou West Service Area, and considering the overall cost, according to... Figure 1 The hole layout method is calculated for the scheme of expanding the hole by 300mm. As shown in the FWD back calculation results, the soil modulus increases by 100-200% after grouting. Therefore, three soil moduli of 60MPa, 120MPa and 180MPa are set for calculation.

[0075] As shown in the table below, the unreinforced pavement cannot meet the design flexural life requirements of the base course, while all three 300mm solutions meet the design flexural life requirements. Increasing the subgrade modulus increases the flexural life by 12-25%. The grouting reinforcement solution shown in the figure is recommended.

[0076] Retain 2m of wheel track in the third lane with applied inorganic binder layer and tensile stress at the bottom.

[0077]

[0078] 3. Scheme Design

[0079] (1) In terms of the retained width, the 1.25-meter width is far away from the wheel track of the third lane, and the bending tensile stress is very small, and the service life exceeds the level of the new road. The 1.75-meter width is close to the wheel track at the edge, and the bending tensile stress increases significantly. The bending tensile stress is close to that of the new road, but the service life is reduced, approaching the level of the old road with the whole structure.

[0080] (2) The 2.25-meter-wide edge is directly below the wheel track, resulting in a significant increase in flexural stress and a large difference in lifespan between the old and new roads. Without intervention, the flexural fatigue life requirement will not be met. Comparatively, the 300mm enlarged hole grouting method shows the most significant reduction in flexural stress, followed by the 200mm enlarged hole method. The 70mm unenlarged hole method shows very little difference in flexural stress compared to the un-grouted method. Neither the 200mm nor the 70mm enlarged hole methods can achieve the designed fatigue flexural life, with the 70mm method falling far short.

[0081] (3) The bottom consolidation is quite important, affecting the service life by about 20-30%. Bottom layered grouting and high-pressure grouting are very necessary.

[0082] (4) 2.0 meters retained, the bending tensile stress is significantly affected by the change of soil modulus. If, as the FWD back calculation results show, the life increases by 12-25% when the soil modulus increases by 1-2 times.

[0083] suggestion:

[0084] (1) It is very safe to retain a 1.25-meter earthen shoulder; a simple grouting treatment can seal the interface.

[0085] (2) The wider the retention is and the closer it is to the third lane wheel track, the greater the impact on the life of the base layer.

[0086] (3) When a width of more than 2 meters is retained, the flexural life requirement of the base layer cannot be met without reinforcement. Using dense piles with a small diameter of about 70 mm will only slightly improve the flexural life of the base layer and still cannot meet the flexural life requirement. When 170 mm holes are drilled, enlarged to 300 mm, and arranged in three rows with a row spacing (distance between the center of adjacent rows of holes) of 40-50 cm and a longitudinal spacing (distance between the center of adjacent holes in the same row) of 1.1 meters, the flexural life of the base layer is significantly improved and can meet the flexural life requirement.

[0087] (4) Due to cost and construction space constraints, it is difficult to implement denser 300mm hole expansion. Further improving the service life of the road shoulder base is also quite difficult.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

Claims

1. A shallow subgrade reinforced by enlarged-hole grouting combined with small-diameter splitting grouting, characterized in that, Several boreholes are divided into multiple rows, and several boreholes are arranged in a quincunx pattern. The boreholes are driven into the old road surface layer and the old road base layer. The boreholes are enlarged from the inside of the boreholes in the fill road base layer. Small-diameter grouting holes are drilled in the middle of adjacent enlarged holes (4).

2. The shallow subgrade enlarged-hole grouting and small-diameter splitting grouting structure reinforcement layout according to claim 1, characterized in that, The diameter of the drilled hole is 110-200mm, and the diameter of the enlarged hole is 250-500mm.

3. The shallow subgrade enlarged-hole grouting and small-diameter splitting grouting structure reinforcement layout according to claim 1, characterized in that, The distance between the centers of adjacent boreholes in a row is 100-150cm.

4. The shallow subgrade enlarged-hole grouting and small-diameter splitting grouting structure reinforcement layout according to claim 1, characterized in that, The distance between the centers of adjacent drill holes is 35-130cm.

5. The shallow subgrade enlarged-hole grouting and small-diameter splitting grouting structure reinforcement layout according to claim 1, characterized in that, The diameter of the small-diameter grouting hole (4) is 60-80mm.

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