CN117926654A - Composite treatment construction method for soft soil interlayer foundation of mountain highway high-fill roadbed valley - Google Patents

Abstract

The invention discloses a composite treatment construction method of a soft soil interlayer foundation of a mountain highway high fill roadbed valley, which comprises the following steps: preparing construction, rechecking a site, replacing, filling, planting soil, dynamic compaction, draining, finishing and checking acceptance. In the construction process, the cultivated soil is replaced and filled into hard block stones, so that the replacement layer becomes a water seepage layer, and the drainage speed of the roadbed substrate is accelerated by matching with the water isolation belt and the blind ditches; and the first crushed stone soil layer and the clay layer are subjected to composite reinforcement treatment through dynamic compaction construction, gaps and moisture stored in soft soil particles and among the particles are discharged, and the compactness, C value and phi value of the soil layer are improved; meanwhile, the hard block stones are densely embedded into the first gravel soil layer or even the clay soil layer through dynamic compaction, so that the first gravel soil layer and the clay soil layer are densely reinforced, the gravel soil, the clay soil and the hard block stones form a solid embedded mixture of the block stones and the soil body, the operation waste of replacing and filling the first gravel soil layer and the clay soil layer is avoided, and the substrate bearing capacity is effectively improved.

Description

Composite treatment construction method for soft soil interlayer foundation of mountain highway high-fill roadbed valley

Technical Field

The invention belongs to the technical field of soft soil foundation construction, and particularly relates to a composite treatment construction method for a soft soil interlayer foundation of a mountain highway high-fill roadbed valley.

Background

The valley soft soil interlayer foundation refers to the situation that one layer of soft soil is clamped between two harder or more stable soil layers in a geological section in valley regions, and the property of the valley soft soil interlayer foundation has an important influence on the safety and stability of engineering. Generally, in soft soil in valley areas, due to factors such as higher humidity, higher water content, loose granular structure and the like, the strength and stability of the whole soft soil interlayer foundation are poor; the larger porosity and the higher water content of the soft soil enable the soft soil interlayer foundation to generate larger compression deformation after load is applied, so that the risk of surface subsidence is higher; when the soft soil layer of the valley contains excessive water and is acted by shearing force, the pore water pressure of the soft soil can be rapidly increased, the soft soil loses the shearing strength and shows liquid-like behavior, so that the risk of foundation settlement and damage is increased; in addition, due to the low topography of valley areas, the drainage of the soft soil interlayer foundation is difficult, and poor drainage conditions can lead to the increase of pore water pressure of the soft soil layer, so that the stability of the foundation is further affected. In the process of treating and constructing a soft soil interlayer foundation in roadbed engineering, a shallow layer replacement method is generally adopted, the soft soil interlayer is removed by digging and replacing the soft soil interlayer with high-strength fillers such as gravel, broken stone and the like, and then proper compaction and reinforcement are carried out to improve the bearing capacity and stability of the whole foundation.

The Chinese patent with the document number of CN102644264B discloses a method for reinforcing a soft soil foundation by adopting soft foundation light ramming, which comprises the following steps: firstly, paving a water permeable layer of 20-30 cm on the surface of a natural foundation, solidifying foundation soil at a certain depth by means of preset ramming energy and ramming times, arranging drainage ditches at intervals of 10-20 m in the longitudinal and transverse directions, and arranging a water collecting well at the intersection point of the drainage ditches so as to drain accumulated water in time. After the natural foundation treatment reaches the requirement, filling the earthwork to a preset design elevation, paving a 20-30 cm permeable layer on the surface of the filled soil, compacting the filled soil layer by preset tamping energy and tamping times, and further solidifying the soft foundation soil lying below the filled soil layer.

The Chinese patent with the document number of CN102644264B adopts that a permeable layer is respectively arranged on the surfaces of a natural soft soil foundation and a filling layer, and the shallow soil layer is reinforced by the existence of double permeable layers. However, the shallow layer replacement method is only suitable for soft soil interlayer foundations with the depth less than 3.0m on the surface layer, and for soft soil on the surface layer, the soft soil lower layer is a hard layer such as silt or crushed stone soil layer, a composite stratum of the hard layer such as silt or crushed stone soil layer in sequence, the stratum thickness is uneven, the local interlayer is formed, the silt soft soil layer is less than 3m away from the foundation surface layer, and the silt and crushed stone soil layer with better loading capacity is also unsuitable for replacement; moreover, if the thickness or depth of the soft soil single layer is more than 3m, the bearing capacity and deformation performance of the whole soft soil layer are difficult to be completely improved by simple shallow layer replacement. In addition, for the V-shaped valley formed by the river erosion molding in the mountain area, the surface soft soil distribution is also in the V-shaped distribution characteristics of thick middle and thin two sides, no clear construction process is adopted for the valley foundation treatment of the soft soil interlayer foundation in the existing specifications, and meanwhile, the dredging replacement treatment is adopted in the range of the embedded depth of the soft soil interlayer, so that the construction cost is higher.

Disclosure of Invention

Aiming at the defects or improvement demands of the prior art, the invention provides a composite treatment construction method for a soft soil interlayer foundation of a mountain highway high fill roadbed valley, which comprises the steps of replacing cultivated soil with hard block stones to enable a replacement layer to be a water seepage layer, and accelerating the drainage speed of the fill roadbed foundation by matching a water isolation belt and blind ditches; and the first crushed stone soil layer and the clay layer are subjected to composite reinforcement treatment through dynamic compaction construction, gaps and moisture stored in soft soil particles and among the particles are discharged, and the compactness, C value and phi value of the soil layer are improved; meanwhile, the hard block stones are densely embedded into the first gravel soil layer or even the clay soil layer through dynamic compaction, so that the first gravel soil layer and the clay soil layer are densely reinforced, the gravel soil, the clay soil and the hard block stones form a solid embedded mixture of the block stones and the soil body, the operation waste of replacing and filling the first gravel soil layer and the clay soil layer is avoided, and the substrate bearing capacity is effectively improved.

In order to achieve the above purpose, the invention provides a construction method for composite treatment of soft soil interlayer foundations of mountain highway high fill roadbed valley, which comprises the following steps:

S1: purchasing and preparing construction materials and equipment, measuring and paying off a foundation filling section where a filled roadbed is positioned, and scattering white lime lines;

S2: measuring and paying off, re-measuring the sections of the foundation at intervals in the transverse direction, detecting the positions of the left and right lines, the middle line and the road embankment slope feet of each section, and making relevant records;

S3: removing the cultivated soil of all foundation replacement layers in the paying-off range, and stacking to a designated position;

S4: constructing a decompression drainage ditch at the upstream and downstream of the displacement layer, simultaneously filling hard stone blocks in the displacement layer, adopting a bulldozer and a loader for primary leveling, adopting a road roller for secondary rolling leveling, and then carrying out dynamic compaction test on the displacement layer to confirm a dynamic compaction scheme; the full breadth of the replacement layer is subjected to dynamic compaction and reinforcement, and the next procedure is carried out after the bearing capacity is detected to be qualified;

s5: on the basis of the decompression drainage ditch on the upstream of the displacement layer, a water-blocking belt is applied, and a drainage ditch is applied to the middle part of the water-blocking belt; meanwhile, blind ditches are formed on the surface of the hard stone layer at the upstream of the water-blocking belt, the downstream of the replacement layer and the step S4;

S6: and after completing blind ditch construction and checking to be qualified, starting roadbed filling construction on the basis of the replacement layer.

Further, the step S4 includes the steps of:

S401: constructing a decompression drainage ditch at the upstream and downstream of the replacement layer, simultaneously filling a layer of hard block stone in the replacement layer, adopting a bulldozer and a loader for primary leveling, adopting a road roller for secondary rolling leveling, and providing an operation site for a transportation vehicle and a dynamic compactor;

S402: determining the area of a dynamic compaction test section on a displacement layer after rolling and leveling, measuring the positions of all dynamic compaction points in the area range of the test section, dividing the test section into a first dynamic compaction point and a second dynamic compaction point in a quincuncial arrangement, and measuring the height H of the displacement layer after leveling;

s403: checking and accepting the weight of the rammer of the dynamic compactor, allowing access after meeting the requirements, and checking and accepting the equipment of the dynamic compactor;

S404: after the dynamic compaction machine is accepted, carrying out dynamic compaction construction on a test section, sequentially carrying out dynamic compaction operation on a second dynamic compaction point after sequentially carrying out dynamic compaction on a first dynamic compaction point, and carrying out next dynamic compaction point construction after the last two times of hammering elevation difference of a single dynamic compaction point is smaller than 4 cm;

s405: after the dynamic compaction of the test section is completed, filling up the compaction pit by using a bulldozer, rolling and leveling by using a heavy road roller, and detecting the bearing capacity of the substrate in the test section area; simultaneously measuring the foundation bearing capacity of each stratum of the dynamic compaction point at the same section position before and after dynamic compaction, comparing the thickness change of each stratum according to the earlier measurement data, and performing test detection within the range of 2-4m to confirm that the dynamic compaction point meets the standard requirement;

S406: after the test section is tested, the dynamic compaction construction is completed on the substrate within the range of all the replacement layers according to the test compaction scheme, meanwhile, the seepage water in the decompression drainage ditch is discharged through the pumping equipment, and the dynamic compaction area is qualified after the bearing capacity detection and then enters the next working procedure.

Further, the filling thickness of the hard block stone is less than or equal to 1m, and the final height is less than the elevation of the replacement layer 5.

Further, the strength of the hard lump stone is more than or equal to 30MPa, and the grain size range is 30 cm-100 cm.

Further, the distance between the dynamic compaction points is 3-3.5 m.

Furthermore, the design tonnage of the rammer of the dynamic compactor is more than or equal to 20t, the single-impact ramming energy of the dynamic compaction construction is more than or equal to 4000 kN.m, and the reinforcement depth is 7-8 m.

Further, the step S5 includes the steps of:

s501: paving impermeable geotextile on the basis of a decompression drainage ditch on the upstream of a replacement layer, filling clay, rolling by a road roller, tamping by a dynamic compactor to form a compact water isolation belt, and excavating and shaping the drainage ditch in the middle of the water isolation belt;

s502: measuring the position and length of a paying-off blind ditch on the surface of the hard stone layer in the step S4 at the upstream of the water-stop belt and the downstream of the replacement layer while constructing the water-stop belt;

s503: longitudinal blind ditches are arranged on the upstream of the water-blocking belt and the downstream of the replacement layer, and a plurality of first transverse blind ditches connected with the longitudinal blind ditches on the downstream of the replacement layer and a second transverse blind ditches communicated with the first transverse blind ditches are arranged on the surface of the hard stone layer in the step S4; and extending the longitudinal blind drain downstream of the displacement layer to the valley origin trench.

Further, the blind ditch comprises a culvert pipe fixedly arranged at the bottom, a reverse filtering geotextile fixedly arranged at the outer layer, and a blind ditch filling layer mainly composed of coarse-grained materials such as crushed gravel and the like.

Further, the spacing distance of the first transverse blind ditches is more than or equal to 9m, and the gradient is more than or equal to 2%; the spacing distance of the second transverse blind ditches is more than or equal to 9m.

Further, one end of the first transverse blind ditch penetrates through the water isolation belt to be communicated with the longitudinal blind ditch at the upstream of the water isolation belt, and the elevation of the first transverse blind ditch is lower than that of the drainage ditch.

In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:

1. According to the construction method, the cultivated soil is replaced and filled into the hard block stone, so that the replacement layer becomes a water seepage layer, and the water isolation belt and the blind ditch are matched, so that the drainage speed of the filled roadbed base is accelerated, the ponding in the range of the filled roadbed base is reduced, the infiltration and erosion of the groundwater to the foundation soil layer are reduced, and the stability and the strength of the filled roadbed are maintained.

2. According to the construction method, on the basis of replacing and filling hard block stones in the replacement layer, the first crushed stone soil layer and the clay layer are subjected to composite reinforcement treatment through dynamic compaction, the crushed stone soil and the clay are compacted through dynamic compaction stress, gaps of soft soil particles are reduced, moisture in the gaps stored in the soft soil particles and among the soft soil particles is discharged, the compactness of the soil layer, the C value and the phi value are improved, and the bearing capacity of the substrate is improved.

3. According to the construction method, the hard block stones are densely embedded into the first gravel soil layer or even the clay layer through dynamic compaction, so that the first gravel soil layer and the clay layer are densely reinforced, the gravel soil, the clay and the hard block stones form a solid embedded mixture of the block stones and the soil body, the waste of the operation of removing and replacing the first gravel soil layer and the clay layer is avoided, the cost is reduced, and the bearing capacity of the substrate is effectively improved.

4. According to the construction method, the cultivated soil removed by the replacement layer can be used for constructing the water-blocking belt after being classified, so that the recovery and the reutilization of resources are realized, the waste of the cultivated soil and the excessive exploitation of natural resources are reduced, and the environment is protected.

5. According to the construction method, the vertical blind ditches and the horizontal blind ditches arranged on the roadbed substrate are used for draining groundwater, the water collecting area of the blind ditches is increased, the drainage performance of the roadbed substrate is improved, meanwhile, the original ditches in valley areas are fully utilized for draining groundwater out of the roadbed, the saturation of the substrate soil is reduced, the strength and the stability of the soil are improved, the settlement, the sinking and the deformation of the roadbed are prevented, the bearing capacity of the roadbed foundation is improved, the stability of the roadbed with high filling is ensured, and the service life of the roadbed is prolonged.

Drawings

FIG. 1 is a geological histogram of a construction site according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the construction steps of a soft soil interlayer foundation according to an embodiment of the present invention;

FIG. 3 is a schematic structural view of a soft soil interlayer foundation according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a dynamic compaction construction process according to an embodiment of the present invention;

FIG. 5 is a schematic view of a construction structure of an extrusion drainage ditch according to an embodiment of the invention;

FIG. 6 is a schematic diagram of dynamic compaction point arrangement in dynamic compaction construction according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a dynamic compaction construction step according to an embodiment of the present invention;

FIG. 8 is a blind ditch floor plan view of an embodiment of the present invention;

FIG. 9 is a cross-sectional view of A-A after construction of a soft soil interlayer foundation according to an embodiment of the present invention;

FIG. 10 is a cross-sectional view of the soft soil sandwich foundation according to the embodiment of the present invention at B-B;

FIG. 11 is a schematic diagram of a cross-sectional structure of a blind ditch according to an embodiment of the present invention;

FIG. 12 is a schematic view of a construction step of a water blocking belt and blind ditches according to an embodiment of the present invention.

Like reference numerals denote like technical features throughout the drawings, in particular:

1-fully weathered schist, 2-first crushed stone soil layer, 3-clay layer, 4-second crushed stone soil layer, 5-replacement layer, 6-filled roadbed, 7-water isolation belt, 8-drainage ditch, 9-blind ditch, 901-culvert pipe, 902-longitudinal blind ditch, 903-first transverse blind ditch, 904-second transverse blind ditch, 905-reverse filtering geotextile, 906-blind ditch filling layer, 10-dense mixed layer, 11-dynamic compaction point, 111-first dynamic compaction point, 112-second dynamic compaction point and 12-decompression drainage ditch.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

As shown in fig. 1 to 12, the embodiment of the invention provides a composite treatment construction method for a soft soil interlayer foundation of a mountain highway high fill subgrade valley, which comprises the following steps:

S1, preparation of construction: purchasing and preparing construction materials and equipment, measuring and paying off a foundation filling section where a filled roadbed is positioned, and scattering white lime lines;

s2, site rechecking: measuring and paying off, re-measuring the sections of the foundation at intervals in the transverse direction, detecting the positions of the left and right lines, the middle line and the road embankment slope feet of each section, and making relevant records;

S3, replacing, filling and planting soil: removing the cultivated soil of all the foundation replacement layers 5 in the paying-off range, and stacking to a designated position;

S4, dynamic compaction construction: constructing a decompression drainage ditch 12 at the upstream and downstream of the replacement layer 5, simultaneously filling hard stones in the replacement layer 5, adopting a bulldozer and a loader for primary leveling, adopting a road roller for secondary rolling leveling, and then carrying out dynamic compaction test on the replacement layer 5 to confirm a dynamic compaction scheme; the full breadth of the replacement layer 5 is subjected to dynamic compaction and reinforcement, and the next procedure is carried out after the bearing capacity is detected to be qualified;

S5, drainage construction: on the basis of the decompression drainage ditch 12 at the upstream of the displacement layer 5, a water-blocking belt 7 is applied, and a drainage ditch 8 is applied to the middle part of the water-blocking belt; meanwhile, blind ditches 9 are formed on the surface of the hard stone layer at the upstream of the water-blocking belt 7 and the downstream of the replacement layer 5 in the step S4;

S6, finishing acceptance: after completing the blind ditch construction and checking to be qualified, the roadbed filling construction is started on the basis of the replacement layer 5.

As shown in fig. 1, the existing stratum of the construction section is surface layer cultivated soil, broken stone soil, clay, broken stone soil, full weathered strong weathering and weak weathered schist from top to bottom in sequence; according to the construction method, the cultivated soil is replaced and filled into the hard block stone, so that the replacement layer is a water seepage layer, and the water isolation belt and the blind ditch are matched, so that the drainage speed of the filled roadbed base is accelerated, the ponding in the range of the filled roadbed base is reduced, the infiltration and erosion of the groundwater to the foundation soil layer are reduced, and the stability and the strength of the filled roadbed are maintained; on the basis of replacing and filling hard block stones in the replacement layer, carrying out composite reinforcement treatment on the first crushed stone soil layer and the clay layer through dynamic compaction construction, compacting and compacting the crushed stone soil and the clay through dynamic compaction stress, reducing gaps of soft soil particles, discharging moisture in the gaps stored in the soft soil particles and among the soft soil particles, and improving soil compactness, C value and phi value; meanwhile, the hard block stones are densely embedded into the first gravel soil layer or even the clay layer through dynamic compaction, so that the first gravel soil layer and the clay layer are densely reinforced, the gravel soil, the clay and the hard block stones form a solid embedded mixture of the block stones and the soil body, the operation waste of digging, replacing and filling the first gravel soil layer and the clay layer is avoided, the cost is reduced, and the bearing capacity of the substrate is effectively improved.

Specifically, as shown in fig. 1 and 2, the step S1 is a construction preparation stage, provides a necessary scheme and construction equipment for subsequent safe and efficient construction, and includes: (1) Carrying out detailed geological investigation on the valley areas of the construction mountain areas, and knowing the geological condition, soil layer property, interlayer position and thickness information of the soft soil interlayer foundation through methods such as drilling, sampling and laboratory testing; (2) On the basis of geological investigation, carrying out engineering design of soft soil interlayer foundation treatment, wherein the engineering design comprises proper treatment measures, construction methods and material selection, and factors such as engineering requirements, geological conditions, environmental influence and economy are considered; (3) According to engineering design, a detailed construction scheme is compiled, wherein the scheme comprises construction steps, construction sequence, equipment and material requirements, construction time plan and the like so as to ensure the high efficiency and safety of construction; (4) Determining required materials according to a construction scheme, and fully purchasing and preparing the materials including filler materials, reinforcing materials, geosynthetic materials and grouting materials; (5) Preparing required construction equipment and tools including an excavator, a drilling machine, a compacting machine and necessary safety equipment and protective measures according to construction schemes and engineering requirements; (6) The constructors are ensured to have necessary skills and knowledge, and are properly trained, meanwhile, construction teams are organized, and responsibilities and cooperation relations of all posts are defined, so that the construction is ensured to be carried out smoothly; (7) And (3) making a safety plan, including safety measures, risk assessment, emergency plans and the like during construction, and simultaneously, setting a proper monitoring system to monitor geological changes, soil displacement and the like during the construction process and timely discover and treat possible problems.

Specifically, as shown in fig. 1 and 2, the step S2 includes: acquiring related design files, specifications and requirements, and determining a range and a target of foundation section detection according to earlier survey planning; before observation and measurement, cleaning sundries, soil and accumulated water on the surface of the foundation; using measuring instruments such as a measuring ruler, a level meter and a theodolite, and observing instruments such as a telescope and a laser range finder to observe and measure the section of the foundation so as to determine parameters such as the geometric shape, the size and the horizontal perpendicularity of the foundation; adopting light power sounding to detect a plurality of sections to detect the bearing capacity of the foundation, and detecting the positions of left and right lines, a central line and the slope feet of the embankment at each section; after the foundation bearing capacity detection is finished, verifying whether stratum geology is consistent with the earlier survey by a digging and probing mode at a dynamic probing position, and sampling to a laboratory for relevant detection, wherein the data comprise uniformity, compactness, water content, liquid limit, plastic limit, compactness and the like of each layer of soil layer are included so as to confirm the stratum and depth which need to be replaced; recording the results of the foundation section test, including observation and measurement data, quality inspection results, structural assessment, and recording possible problems and improvements.

As shown in fig. 1 to 12, a soft foundation treatment scheme of the valley soft soil interlayer is determined according to the earlier survey result of the step S1 and the foundation rechecking result of the step S2, namely, the foundation of the section of roadbed is treated by adopting a composite reinforcement technology of soil replacement and tillage and soil planting and dynamic compaction.

Specifically, as shown in fig. 3 to 6, the step S3 includes: using an excavator, a bulldozer and a forklift to remove the ploughing and planting soil of the replacement layer 5 in the paying-off range; meanwhile, classifying the removed cultivated soil according to the property, water content, impurity content and the like of the soil so as to facilitate subsequent treatment and utilization; transporting the removed cultivated soil to a designated stacking position; in the stacking process, the leveling and uniform distribution of the soil are ensured, and compaction equipment such as a road roller is used for properly compacting the soil, so that the compactness and stability of the stacked soil are improved, and the safety risk is reduced; after the soil tillage and soil planting are removed and stacked, construction equipment which is used for removing sundries, wastes and remained in a clear area is used for facilitating the follow-up construction.

Specifically, as shown in fig. 4 to 7, the step S4 of performing composite reinforcement treatment on the first gravel layer 2 and the clay layer 3 by dynamic compaction construction includes the following steps:

S401: a decompression drainage ditch 12 is arranged at the upstream and downstream of the displacement layer 5, a layer of hard stone is filled in the displacement layer 5, a bulldozer and a loader are adopted for primary leveling, and a road roller is adopted for secondary rolling leveling, so that an operation site is provided for a transportation vehicle and a dynamic compactor;

S402: the area of a dynamic compaction test section is determined on the displacement layer 5 after rolling and leveling, the positions of all dynamic compaction points 11 are measured and lofted in the area range of the test section, the positions are divided into a first dynamic compaction point 111 and a second dynamic compaction point 112 in a quincuncial arrangement, and the height H of the displacement layer 5 after leveling is measured;

s403: checking and accepting the weight of the rammer of the dynamic compactor, allowing access after meeting the requirements, and checking and accepting the equipment of the dynamic compactor;

S404: after the dynamic compaction machine is accepted, carrying out dynamic compaction construction on a test section, sequentially carrying out dynamic compaction operation on a second dynamic compaction point 112 after sequentially carrying out dynamic compaction on a first dynamic compaction point 111, and carrying out next construction on a dynamic compaction point 11 after the last two hammering elevation differences of a single dynamic compaction point 11 are smaller than 4 cm;

S405: after the dynamic compaction of the test section is completed, filling up the compaction pit by using a bulldozer, rolling and leveling by using a heavy road roller, and detecting the bearing capacity of the substrate in the test section area; simultaneously measuring the foundation bearing capacity of each stratum at the same section position before and after dynamic compaction of the dynamic compaction point 11, comparing the thickness change of each stratum according to the earlier measurement data, and performing test detection within the range of 2-4m to confirm that the dynamic compaction point meets the standard requirement;

s406: after the test section is tested, the dynamic compaction construction is completed on the substrate within the range of all the replacement layers 5 according to the test compaction scheme, meanwhile, the seepage water in the decompression drainage ditch 12 is discharged through the water pumping equipment, and the dynamic compaction area is qualified after the bearing capacity detection and then enters the next working procedure.

Preferably, the filling thickness of the hard block stone is less than or equal to 1m, and the final height is less than the elevation of the replacement layer 5.

Preferably, the strength of the hard lump stone is more than or equal to 30MPa, and the grain size range is 30 cm-100 cm.

Preferably, the single-impact ramming energy of the dynamic compaction construction is more than or equal to 4000 kN.m, the reinforcement depth is 7-8 m, and the processing requirement of the roadbed base in the depth range of 2-4 m is met.

Preferably, the distance between the dynamic compaction points 11 is 3-3.5 m.

Preferably, the design tonnage of the rammer of the dynamic compactor is more than or equal to 20t.

Preferably, the whole test section and the whole replacement layer 5 mainly detect the bearing capacity of the substrate in a flat plate static load test mode, and the bearing capacity is more than or equal to 220KPa.

Preferably, the foundation bearing capacity measuring method comprises a heavy duty sounding method.

Specifically, as shown in fig. 3 and 8 to 12, the step S5 is to block the groundwater and shallow ground water from flowing into the subgrade substrate by applying the water blocking tape 7, and the blind drain 9 is to further reduce the water content of the subgrade 6 to ensure the safety of the subgrade, and it comprises the following steps:

S501: paving impermeable geotextile on the basis of a decompression drainage ditch 12 at the upstream of a displacement layer 5, filling clay, compacting by a road roller, compacting by a dynamic compactor to form a compact water-isolating belt 7, and excavating and shaping a drainage ditch 8 at the middle part of the water-isolating belt 7;

S502: the construction of the water-blocking belt 7 is carried out, and the positions and the lengths of the blind ditches 9 are measured and paid out on the surface of the hard stone layer at the upstream of the water-blocking belt 7 and the downstream of the replacement layer 5 in the step S4;

S503: longitudinal blind ditches 902 are formed on the upstream of the water-blocking belt 7 and the downstream of the replacement layer 5, and a plurality of first transverse blind ditches 903 connected with the longitudinal blind ditches 902 on the downstream of the replacement layer 5 and a second transverse blind ditches 904 communicated with the first transverse blind ditches 903 are formed on the surface of the hard stone layer in the step S4; and extends the longitudinal blind drain 902 downstream of the displacement layer 5 to the valley origin trench.

Preferably, the drainage ditch 8 is communicated with a slope drainage system of the filling roadbed 6 which is constructed later.

Preferably, the blind ditch 9 includes culvert 901, reverse filtering geotechnical cloth 905 and blind ditch filling layer 906 mainly composed of coarse grain materials such as crushed gravel and the like, and further includes longitudinal blind ditch 902, first transverse blind ditch 903 and second transverse blind ditch 904, and the underground water is discharged through the matching of the longitudinal blind ditch and the transverse blind ditch, so that the water collecting area of the blind ditch is increased, the drainage performance of the roadbed substrate is improved, meanwhile, the underground water is discharged out of the roadbed by fully utilizing the valley original ditch, the saturation of the substrate soil is reduced, the strength and the stability of the soil are improved, the settlement, the subsidence and the deformation of the roadbed are prevented, the bearing capacity of the roadbed foundation is improved, the stability of the roadbed with high filling is ensured, and the service life of the roadbed is prolonged.

Preferably, the culvert 901 is mainly a plastic drainage culvert made of thermoplastic synthetic resin, and has the characteristics of high surface opening ratio, good water collection, good drainage and strong compression resistance, so that the effect of discharging groundwater on the subgrade 6 filled by the blind ditches 9 is further enhanced, and the service life is prolonged.

Preferably, the spacing distance of the first transverse blind ditch 903 is more than or equal to 9m, and the gradient is more than or equal to 2%; the spacing distance of the second transverse blind ditches 904 is more than or equal to 9m.

Preferably, one end of one of the first lateral blind ditches 903 passes through the water-blocking tape 7 to communicate with the longitudinal blind ditches 902 upstream of the water-blocking tape 7, and has a lower elevation than the drainage ditches 8.

Preferably, the clay used in the step S501 includes the cultivated soil after being replaced and filled in the replacement layer 5, so as to realize recycling and reutilization of resources, reduce waste of the cultivated soil and over-mining of natural resources, and protect environment.

Specifically, as shown in fig. 3, the step S6 includes: checking the roadbed filling construction scheme after checking and accepting the completed foundation; when the filling roadbed 6 is filled, hard rock or water seepage soil is fully filled in the following parts, and the filling materials above the height H of the replacement layer 5 can meet the requirements; when filling, firstly filling hard stone soil with the grain diameter larger than 50cm, carrying out quality detection according to the requirement of a stone filling roadbed after rolling, and carrying out filling quality requirement detection according to the filling compaction degree 93% of the roadbed filling embankment by taking 90% of the rolling degree of the original ground as an acceptance standard, so as to ensure that the bearing capacity of the foundation is not lower than that of the stone breaking soil.

It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.

In this patent, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; it will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. The composite treatment construction method for the soft soil interlayer foundation of the mountain highway high-fill roadbed valley is characterized by comprising the following steps:

S1: purchasing and preparing construction materials and equipment, measuring and paying off a foundation filling section where a filled roadbed is positioned, and scattering white lime lines;

S2: measuring and paying off, re-measuring the sections of the foundation at intervals in the transverse direction, detecting the positions of the left and right lines, the middle line and the road embankment slope feet of each section, and making relevant records;

s3: removing the cultivated soil of all the foundation replacement layers (5) in the paying-off range, and stacking to a designated position;

S4: constructing a decompression drainage ditch (12) at the upstream and downstream of the replacement layer (5), simultaneously filling hard stones in the replacement layer (5), adopting a bulldozer and a loader for primary leveling, adopting a road roller for secondary rolling leveling, and then carrying out dynamic compaction test on the replacement layer (5), and confirming a dynamic compaction scheme; the dynamic compaction reinforcement is completed on the whole breadth of the replacement layer (5), and the next procedure is carried out after the bearing capacity is detected to be qualified;

S5: on the basis of a decompression drainage ditch (12) at the upstream of the displacement layer (5), a water-blocking belt (7) is applied, and a drainage ditch (8) is applied to the middle part of the water-blocking belt; meanwhile, blind ditches (9) are formed on the upstream of the water-blocking belt (7), the downstream of the replacement layer (5) and the surface of the hard stone layer in the step S4;

S6: after completing the blind ditch construction and checking to be qualified, the roadbed filling construction is started on the basis of the replacement layer (5).

2. The construction method according to claim 1, wherein the step S4 includes the steps of:

S401: a decompression drainage ditch (12) is arranged at the upstream and downstream of the replacement layer (5), a layer of hard stone block is filled in the replacement layer (5), a bulldozer and a loader are adopted for primary leveling, a road roller is adopted for secondary rolling leveling, and an operation site is provided for a transportation vehicle and a dynamic compactor;

S402: determining the area of a dynamic compaction test section on a displacement layer (5) subjected to rolling and leveling, measuring the positions of all dynamic compaction points (11) in the area range of the test section, dividing the positions into a first dynamic compaction point (111) and a second dynamic compaction point (112) in a quincuncial arrangement, and measuring the height H of the displacement layer (5) subjected to leveling;

s403: checking and accepting the weight of the rammer of the dynamic compactor, allowing access after meeting the requirements, and checking and accepting the equipment of the dynamic compactor;

S404: after the dynamic compaction machine is accepted, performing dynamic compaction construction on a test section, sequentially performing dynamic compaction operation on a second dynamic compaction point (112) after sequentially performing dynamic compaction on a first dynamic compaction point (111), and performing next dynamic compaction point (11) construction after the last two times of hammering elevation difference of a single dynamic compaction point (11) is smaller than 4 cm;

S405: after the dynamic compaction of the test section is completed, filling up the compaction pit by using a bulldozer, rolling and leveling by using a heavy road roller, and detecting the bearing capacity of the substrate in the test section area; simultaneously measuring the foundation bearing capacity of each stratum layer at the same section position before and after dynamic compaction of the dynamic compaction point (11), comparing the thickness change of each stratum layer according to the earlier-stage measurement data, and performing test detection within the range of 2-4m to confirm that the dynamic compaction point meets the standard requirements;

S406: after the test section is tested, according to the test ramming scheme, the foundation in the range of all the replacement layers (5) is subjected to dynamic ramming construction, meanwhile, seepage water in the decompression drainage ditch (12) is discharged through the pumping equipment, and the dynamic ramming area is subjected to bearing capacity detection and then enters the next working procedure.

3. The construction method according to claim 2, wherein the hard block stone is filled to a thickness of 1m or less and a final height of less than the level of the displacement layer 5.

4. The construction method according to claim 2, wherein the strength of the hard lump stone is not less than 30MPa, and the grain size is in the range of 30cm to 100cm.

5. The construction method according to claim 2, wherein the distance between the dynamic compaction points (11) is 3-3.5 m.

6. The construction method according to claim 2, wherein the design tonnage of the rammer of the dynamic compactor is more than or equal to 20t, the single impact energy of the dynamic compaction construction is more than or equal to 4000 kN.m, and the reinforcement depth is 7-8 m.

7. The construction method according to any one of claims 1 to 6, wherein the step S5 includes the steps of:

s501: paving impermeable geotextile on the basis of a decompression drainage ditch (12) at the upstream of a replacement layer (5), filling clay, compacting by a road roller, compacting by a dynamic compactor to form a compact water-isolating belt (7), and excavating and shaping a drainage ditch (8) at the middle part of the water-isolating belt (7);

S502: the construction of the water-blocking belt (7) is carried out, and the positions and the lengths of the paying-off blind ditches (9) are measured on the upstream of the water-blocking belt (7), the downstream of the replacement layer (5) and the surface of the hard stone layer in the step S4;

S503: longitudinal blind ditches (902) are formed on the upstream of the water-blocking belt (7) and the downstream of the replacement layer (5), a plurality of first transverse blind ditches (903) connected with the longitudinal blind ditches (902) on the downstream of the replacement layer (5) and a second transverse blind ditches (904) communicated with the first transverse blind ditches (903) are formed on the surface of the hard stone layer in the step S4; and extending the longitudinal blind drain (902) downstream of the displacement layer (5) to the valley origin trench.

8. The construction method according to claim 7, wherein the blind drain (9) comprises a culvert pipe (901) fixedly arranged at the bottom, a reverse-filtering geotextile (905) fixedly arranged at the outer layer, and a blind drain filling layer (906) mainly composed of coarse-grained material such as crushed gravel or the like.

9. The construction method according to claim 7, wherein the first lateral blind ditch (903) is spaced by a distance of not less than 9m and has a gradient of not less than 2%; the spacing distance of the second transverse blind ditches (904) is more than or equal to 9m.

10. The construction method according to claim 7, characterized in that one end of one of the first lateral blind ditches (903) is connected to the longitudinal blind ditches (902) upstream of the water-blocking strip (7) through the water-blocking strip (7), and its elevation is lower than that of the drainage ditches (8).