Cement stabilized macadam base splicing method and splicing structure

Abstract

The application discloses a cement stabilized macadam base splicing method and a splicing structure, and belongs to the technical field of road paving. The splicing method is characterized in that a joint connecting rod is arranged at intervals of 50-100 cm along the longitudinal direction of a road, and the method comprises the following steps: S1, drilling a hole of a certain depth in the old road base layer along the transverse direction of the road; S2, filling the hole with semi-rigid connecting rod mixture and tamping; and S3, reserving and filling semi-rigid connecting rod mixture with the same mixing ratio as the hole on the top of the lower bearing layer outside the old road base layer and compacting. Compared with the prior art, the pavement splicing method can effectively connect the old road base layer and the splicing base layer, increase the shear resistance and tensile resistance of the base splicing joint, and reduce the cracking risk of the base splicing joint.

Description

Technical Field

[0001] This invention relates to the field of road engineering, specifically to a method and structure for splicing cement-stabilized crushed stone base courses. Background Technology

[0002] With the rapid development of the social economy, the number of vehicles in my country has increased rapidly. Many of the high-grade highways built in the early stages of the country require expansion and reconstruction to meet the growing traffic demands, as the projected traffic volume cannot meet the needs of the expanding traffic flow. One problem encountered during the expansion and reconstruction process is the connection between the original road base and the widened base. In recent years, most reconstruction and expansion projects have adopted the method of creating steps in the old road base, and then connecting the steps to the widened base by spreading cement slurry. However, due to different excavation methods and varying surface roughness, the bonding strength between the old and new bases is relatively weak when relying solely on a thin layer of cement slurry at the joint. Cracking often occurs at the joint due to insufficient adhesion. Furthermore, the joint is often a weak point in the construction process, further weakening the bonding strength. Summary of the Invention

[0003] The technical objective of this invention is to address the shortcomings of the prior art by providing a method for splicing cement-stabilized crushed stone base layers, which can prevent cracking at the joints caused by insufficient bonding at the splicing joints.

[0004] A further technical objective of this invention is to provide a cement-stabilized crushed stone base splicing structure.

[0005] The technical objective of this invention is achieved as follows: a method for splicing cement-stabilized crushed stone base courses, characterized by setting a joint connecting rod every dmm along the longitudinal direction of the road, where d = 500-1000, comprising:

[0006] S1. Drill holes of a certain depth along the transverse direction of the roadbed in the old roadbed;

[0007] S2. Fill the hole with the semi-rigid connecting rod mixture and tamp it down;

[0008] S3. A semi-rigid connecting rod mixture with the same mix ratio as the filling hole is reserved on the top of the subgrade outside the old road base and compacted. The semi-rigid connecting rod mixture inside the hole and the semi-rigid connecting rod mixture outside the hole are cured together to form a joint connecting rod.

[0009] Preferably, in step S3, the splicing and compaction of the base layer is completed within the initial setting time of the cement in the semi-rigid connecting rod mixture, so that the semi-rigid connecting rod mixture inside the hole, the semi-rigid connecting rod mixture outside the hole, and the splicing base layer are cured and formed simultaneously.

[0010] As a preferred option, geotextile can be covered on the pre-reserved semi-rigid connecting rod mixture, and water can be sprinkled to keep it moist. The geotextile can then be removed when the splicing base layer is laid.

[0011] As a preferred option, after reserving the semi-rigid connecting rod mixture outside the hole, the reserved mixture is covered with geotextile and moistened with water; when laying the splicing base course mixture, the covering geotextile is removed and the splicing base course mixture and the reserved connecting rod mixture are rolled simultaneously.

[0012] or,

[0013] Leave semi-rigid connecting rod mixture outside the hole and perform preliminary compaction with a compaction density of 50%-80%. Cover the preliminary compacted mixture with geotextile and sprinkle water to keep it moist. When laying the splicing base course mixture, remove the geotextile covering and compact the splicing base course mixture and the preliminary compacted connecting rod mixture simultaneously.

[0014] Preferably, the length (along the longitudinal direction of the road) and height of the outer part of the joint connecting rod hole are both greater than the diameter of the hole. Its length can be 100-200mm along the longitudinal direction of the road with the hole axis as the center, and is particularly preferred to be 120-180mm; its height can be 45-100mm, and is particularly preferred to be 45-65mm; its width along the transverse direction of the road is 100-200mm, and is particularly preferred to be 150-200mm.

[0015] As a preferred option, the joint connecting rods are arranged in layers, with the number of joint connecting rod layers being the same as the number of base layer layers.

[0016] Preferably, the joint connecting rod is set at the bottom of the base layer. When the road base layer consists of an upper base layer, a lower base layer and a subbase layer, the three joint connecting rods are respectively set at the bottom of the upper base layer, the bottom of the lower base layer and the bottom of the subbase layer.

[0017] Preferably, the longitudinal spacing between the axial positions of the upper and lower joint connecting rods along the road is 0.25d-0.45d, and more preferably 0.3d-0.4d.

[0018] Preferably, in step S1, the hole is a horizontal hole with an inclination angle controlled within ±5°, a hole depth of 150mm-250mm, particularly preferably 200-250mm, and a diameter of 25-40mm, particularly preferably 35-40mm.

[0019] Preferably, the semi-rigid connecting rod mixture is cement-stabilized fine-grained soil.

[0020] Preferably, the cement content in the semi-rigid connecting rod mixture is 3.5%-5.5% by mass percentage, and particularly preferably 4.5%-5.5%.

[0021] As a preferred option, the 7-day unconfined compressive strength of the semi-rigid connecting rod mixture is not less than 5 MPa.

[0022] Preferably, the semi-rigid connecting rod mixture has a sieve pass rate of 100% or less for a 9.5mm sieve, 80%-95% for a 4.75mm sieve, 35%-55% for a 2.36mm sieve, and 10%-15% for a 0.075mm sieve.

[0023] Preferably, before filling the semi-rigid connecting rod mixture into the hole in step S2, a small amount of water can be sprayed into the hole to fully wet the inner wall of the hole.

[0024] In the above method of the present invention, the joint connecting rod mixture can form an integral whole with the new and old subgrade materials, resulting in a cement-stabilized crushed stone base splicing structure in which the joint parts of the new and old base layers can be effectively connected.

[0025] Compared with the prior art, the cement-stabilized crushed stone base splicing method and splicing structure of the present invention have the following outstanding advantages:

[0026] (I) The present invention adopts a joint connecting rod method. The outer part of the joint connecting rod is formed and cured simultaneously with the splicing base mixture to form an integral whole. The other end of the joint connecting rod extends into the interior of the old road base and measures are taken to connect it with the old road base mixture to form a strong joint tensile force, so that the new and old road base mixtures at the joint position are effectively connected, avoiding cracking at the joint position due to insufficient connection at the joint position.

[0027] (ii) The joint connecting rod is made of cement-stabilized fine-grained soil, which is the same cement-stabilized inorganic binder as the base cement-stabilized crushed stone mixture. Furthermore, the amount of drying shrinkage deformation and thermal shrinkage deformation are basically the same, and they have the same strength, so that the splicing position can remain stable for a long time. Attached Figure Description

[0028] Appendix Figure 1 This is a schematic diagram of the cement-stabilized crushed stone base layer splicing structure of the present invention (without the spliced ​​base layer laid);

[0029] Appendix Figure 2 This is a cross-sectional view of the cement-stabilized crushed stone base splicing structure of the present invention (without the splicing base laid);

[0030] Appendix Figure 3 This is a cross-sectional view of the cement-stabilized crushed stone base splicing structure of the present invention. Detailed Implementation

[0031] The following detailed description of the cement-stabilized crushed stone base splicing method and splicing structure of the present invention, with reference to the accompanying drawings and specific embodiments, is provided.

[0032] Example 1:

[0033] As shown in the attached diagram, the cement-stabilized crushed stone base course splicing structure consists of the old road subbase 1, the old road lower base course 2, the old road upper base course 3, the joint connecting rod 4, the splicing subbase 5, the splicing lower base course 6, and the splicing upper base course 7.

[0034] The specific assembly steps are as follows:

[0035] S1. Steps with a width of 200mm are made along the edges of the old road subbase 1, old road lower base 2, and old road upper base 3. Horizontal holes with a diameter of 40mm (angle controlled ±2°) are drilled transversely along the road, with a hole depth of 250mm. The axial spacing between holes in the same layer is d = 500mm, and the longitudinal spacing between the axial positions of the upper and lower layer holes along the road is 160mm.

[0036] S2. Perform subbase assembly work.

[0037] S2.1 About two hours before paving the splicing subbase 5, spray water into the holes of the old road subbase 1 to fully wet the inner wall of the holes, fill the holes with semi-rigid connecting rod mixture 41, and use impact equipment to compact the mixture in the holes. The compaction degree reached more than 99% after testing.

[0038] S2.2 A portion of semi-rigid connecting rod mixture 42 is reserved outside the hole. The reserved mixture is covered with geotextile and moistened with water. When the paver lays the mixture for the spliced ​​subbase 5, the geotextile covering is removed, and the newly laid mixture is compacted simultaneously with the reserved connecting rod mixture. Finally, geotextile is covered on the surface of the structural layer and cured with water for 7 days. The semi-rigid connecting rod mixture inside and outside the hole together form the joint connecting rod 4, which forms a stable connection with the old subbase 1 and the spliced ​​subbase 5. The portion of the joint connecting rod 4 outside the hole is 140mm long and 60mm high along the longitudinal direction of the road with the hole axis as the center, and 150mm wide along the transverse direction of the road.

[0039] S3. Perform the lower layer splicing operation using the method described in S2;

[0040] S4. Perform the sub-base splicing operation using the method described in S2.

[0041] The semi-rigid connecting rod mixture has a cement content of 5.5% by mass, a 7-day unconfined compressive strength of 8.3 MPa, and a 100% pass rate through a 9.5 mm sieve, an 86.3% pass rate through a 4.75 mm sieve, a 42.7% pass rate through a 2.36 mm sieve, and an 11.5% pass rate through a 0.075 mm sieve.

[0042] After 28 days of conditioning, the deflection values ​​at the joints were compared and tested. The deflection value of the joints with tie rods was about 42% smaller than that of the joints without tie rods.

[0043] Example 2:

[0044] The splicing structure of the cement-stabilized crushed stone base course is the same as in Example 1.

[0045] The specific assembly steps are as follows:

[0046] S1. Steps with a width of 200mm are made along the edges of the old road subbase 1, old road lower base 2, and old road upper base 3. Horizontal holes with a diameter of 40mm (angle controlled ±2°) are drilled transversely along the road, with a hole depth of 250mm. The axial spacing between holes in the same layer is d = 500mm, and the longitudinal spacing between the axial positions of the upper and lower layer holes along the road is 160mm.

[0047] S2. Perform subbase assembly work.

[0048] S2.1 About two hours before paving the splicing subbase 5, spray water into the holes of the old road subbase 1 to fully wet the inner wall of the holes, fill the holes with semi-rigid connecting rod mixture 41, and use impact equipment to compact the mixture in the holes. The compaction degree reached more than 99% after testing.

[0049] Step S2.2: Reserve a portion of the semi-rigid connecting rod mixture 42 outside the hole and perform preliminary compaction with a preliminary compaction density of 60%; cover the preliminary compacted mixture with geotextile and sprinkle water to keep it moist; when the paver lays the mixture of the spliced ​​subbase 5, remove the covering geotextile and compact the newly laid mixture and the preliminary compacted connecting rod mixture simultaneously; finally, cover the surface of the structural layer with geotextile and sprinkle water for 7 days. The semi-rigid connecting rod mixture inside and outside the hole together form the joint connecting rod 4 and form a stable connection with the old road subbase 1 and the spliced ​​subbase 5.

[0050] S3. Perform the lower layer splicing operation using the method described in S2;

[0051] S4. Perform the sub-base splicing operation using the method described in S2.

[0052] The semi-rigid connecting rod mixture is the same as in Example 1.

[0053] After 28 days of curing, the deflection values ​​at the joint locations were compared and tested. The joints with tie rods had a deflection value that was about 42% smaller than those with only stepped overlaps and no tie rods.

Claims

1. A method for splicing cement-stabilized crushed stone base courses, characterized in that, A joint connecting rod is installed every d mm along the longitudinal direction of the road, where d = 500-1000. include: S1. Drill holes of a certain depth along the transverse direction of the roadbed in the old roadbed; S2. Fill the hole with the semi-rigid connecting rod mixture and tamp it down; S3. A semi-rigid connecting rod mixture with the same mix ratio as the filling hole is pre-reserved and compacted at the top of the subgrade outside the old road base. After curing, the semi-rigid connecting rod mixture inside and outside the hole together form a joint connecting rod. The length and height of the portion of the joint connecting rod outside the hole are both greater than the hole diameter. The semi-rigid connecting rod mixture is made of cement-stabilized fine-grained soil. By mass percentage, the cement content in the semi-rigid connecting rod mixture is 3.5%-5.5%. The mixture has a 9.5mm sieve pass rate of less than or equal to 100%, a 4.75mm sieve pass rate of 80%-95%, a 2.36mm sieve pass rate of 35%-55%, and a 0.075mm sieve pass rate of 10%-15%.

2. The method for splicing cement-stabilized crushed stone base course according to claim 1, characterized in that, In step S3, the splicing and compaction of the base layer is completed within the initial setting time of the cement in the semi-rigid connecting rod mixture, so that the semi-rigid connecting rod mixture inside the hole, the semi-rigid connecting rod mixture outside the hole, and the splicing base layer are cured and formed simultaneously.

3. The method for splicing cement-stabilized crushed stone base course according to claim 1 or 2, characterized in that: After reserving the semi-rigid connecting rod mixture outside the hole, cover the reserved mixture with geotextile and sprinkle water to keep it moist; when laying the splicing base mixture, remove the covering geotextile and compact the splicing base mixture and the reserved connecting rod mixture simultaneously. or, Leave semi-rigid connecting rod mixture outside the hole and perform preliminary compaction with a compaction density of 50%-80%. Cover the preliminary compacted mixture with geotextile and sprinkle water to keep it moist. When laying the splicing base course mixture, remove the geotextile covering and compact the splicing base course mixture and the preliminary compacted connecting rod mixture simultaneously.

4. The method for splicing cement-stabilized crushed stone base course according to claim 3, characterized in that: The outer part of the joint connecting rod hole is 100-200mm wide along the road.

5. The method for splicing cement-stabilized crushed stone base course according to claim 4, characterized in that: The joint connecting rods are set in layers, and the number of joint connecting rod layers is the same as the number of base layer layers.

6. The method for splicing cement-stabilized crushed stone base course according to claim 5, characterized in that, The joint connecting rod is set at the bottom of the base layer, and the axial position of the upper joint connecting rod and the lower joint connecting rod is 0.25d-0.45d along the longitudinal direction of the road.

7. The method for splicing cement-stabilized crushed stone base course according to claim 6, characterized in that, In step S1, the hole depth is 150mm-250mm and the diameter is 25-40mm.

8. The method for splicing cement-stabilized crushed stone base course according to claim 3, characterized in that: The unconfined compressive strength of the semi-rigid connecting rod mixture after 7 days is not less than 5 MPa.

9. The method for splicing cement-stabilized crushed stone base course according to claim 3, characterized in that: Before filling the semi-rigid connecting rod mixture into the hole in step S2, spray a small amount of water into the hole to fully wet the inner wall of the hole.

10. The cement-stabilized crushed stone base splicing structure obtained by the method of any one of claims 1-9.

Images