CN-122013618-A - Multistage reinforcement construction method for granite high-fill roadbed

CN122013618ACN 122013618 ACN122013618 ACN 122013618ACN-122013618-A

Abstract

The invention discloses a multistage reinforcement construction method for a granite high-fill roadbed, and belongs to the technical field of roadbed construction in road engineering. The method aims to solve the problems that the combination of granite stratum and roadbed filler interface is weak, drainage in a high-filling body is not smooth, the stability of the construction process is difficult to control and the like. The method comprises the steps of roughening the surface of a granite foundation, paving a cement bentonite slurry transition layer to strengthen interface bonding, paving a first layer of filler, arranging a vertical drainage system, performing layered filling and reinforcement, wherein each layer comprises paving a geogrid, anchoring by using a portal anchor rod, covering a water-permeable crushed stone layer, performing circulation until the design elevation, and meanwhile, arranging monitoring points on the central line of a roadbed and the slope feet, and dynamically adjusting construction parameters according to horizontal displacement data, such as pausing filling, adding a reinforcement layer or adjusting compaction technology. The method is mainly used for building the high-fill roadbed on the granite stratum, and can effectively improve the overall stability and construction safety controllability of the roadbed.

Inventors

ZHONG QIUYANG
ZHANG JIMING
MA BO
Zhong Zhenbo
MAO YUNHUA

Assignees

中国建筑第二工程局有限公司
中建二局(四川)建设发展有限公司
中建二局重庆建设发展有限公司
中建二局重庆实业有限公司

Dates

Publication Date: 20260512
Application Date: 20251202

Claims (10)

1. The multistage reinforcement construction method for the granite high-fill roadbed is characterized by comprising the following steps of: s1, foundation treatment, namely cleaning and roughening the surface of a granite stratum, wherein the roughening depth is 8-15 mm, and a rough joint surface is formed; s2, constructing a transition layer, namely paving a cement-bentonite slurry transition layer on the rock surface after roughening, and uniformly spreading a layer of machine-made sand with the grain diameter of 5-10 mm before slurry initial setting to form an enhanced bonding interface; S3, setting a first layer filling and drainage system, namely setting a vertical drainage system after paving and compacting a first layer filling layer, wherein the filling layer is gravelly soil with the thickness of 0.3-0.5 m, rolling for 6-8 times at the speed of 2-4 km/h by using a vibratory roller, and the compactness reaches 95-97%, and arranging plastic drainage belts of a multi-strip filter membrane according to square grids, and inserting the plastic drainage belts to penetrate the filling layer in depth and contact with a granite stratum; S4, performing layered filling and reinforcement, namely performing reinforcement layer paving, water-permeable gravel layer paving, filler layer paving and compaction on a first filler layer, repeating the steps until the design elevation is reached, wherein the reinforcement layer comprises a geogrid and a portal anchor rod, the tensile strength of the geogrid is 80kN/m to 120kN/m, the geogrid is tensioned and fixed during paving, the lap joint width is 0.4m to 0.5m, the portal anchor rod is immediately used for anchoring after paving, the arrangement interval of the portal anchor rod is 1.5m to 2.0m, two supporting legs of the portal anchor rod are driven into the filler layer, steel backing plates are arranged on a transverse rod to tightly press the geogrid on the surface of the filler layer, after each reinforcement layer is paved and anchored, a water-permeable gravel layer with the thickness of 0.2m to 0.3m is paved on the reinforcement layer, and other filler layers above the first filler layer have the same specification and construction method as the first filler layer; And S5, monitoring and feedback control, namely arranging deep horizontal displacement monitoring points at the center line of the roadbed and the slope feet at two sides, measuring the monitoring frequency after filling the filler with the thickness of 2.0m every time, and starting feedback control measures when the monitoring data show that the horizontal displacement increment exceeds 20mm or the accumulated horizontal displacement exceeds 60mm in the single-layer filling period of any monitoring point, wherein the feedback control measures comprise pausing filling, adding a layer of reinforced geogrid in a displacement area, reducing the thickness of the filler of the subsequent three layers to 0.2m to 0.3m, and simultaneously increasing the compaction pass number to 10 times to 12 times.
2. The method for multistage reinforcement construction of granite high-fill subgrade according to claim 1, characterized in that a layer of needled non-woven geotextile is further laid on the surface of said water-permeable crushed stone layer as a reverse filtering layer, said needled non-woven geotextile having a mass per unit area of 300g/m 2 to 400g/m 2 and a vertical permeability coefficient of not less than 1.0X10 -2 cm/s, and an elongation allowance of 5% to 8% being maintained in the cross section direction of the subgrade when laid.
3. The method for multistage reinforcement of granite high-fill subgrade according to claim 2, wherein after said needled nonwoven geotextile is laid, a coarse sand protection layer having a thickness of 50mm to 80mm is laid first and compacted by static pressure, and then an upper filler layer is laid.
4. The multistage reinforcement construction method for the granite high-fill subgrade according to claim 1, wherein the gravelly soil filler is continuously graded, the maximum grain size is not more than 50mm, the non-uniformity coefficient C u is not less than 5, the curvature coefficient C e is between 1 and 3, and the water content of the gravelly soil filler is regulated and controlled before paving so as to be in the range of-1% to +2% of the optimal water content.
5. The method for multistage reinforcement of granite high-fill subgrade according to claim 3, wherein the two leg surfaces of said portal anchor have threads or concave-convex lines and are coated with cement slurry before installation to enhance the grip and anchoring effect between the anchor and filler.
6. The multistage reinforcement construction method for the granite high-fill subgrade of claim 1, wherein a sand gravel reverse filtering bag is arranged at the contact position of the top of the vertical drainage system and the water-permeable gravel layer, and is formed by filling stone with the particle size of 5-15 mm in geotextile packages, and the diameter of the sand gravel reverse filtering bag is 300-400 mm.
7. The method for multistage reinforcement of granite high-fill subgrade according to claim 6, wherein during compaction operation, when the ambient temperature is higher than 30 ℃ or the wind speed is higher than 3m/s, the surface of the compacted filler is subjected to water mist maintenance, and the spraying amount is controlled to be 0.5L/m 2 -1.0L/m 2 so as to maintain the water content of the surface layer of the filler and ensure uniform and stable compaction.
8. The multistage reinforcement construction method of the granite ground high-fill subgrade according to claim 1, which is characterized in that for a locally existing strong weathered granite groove or crack area, the foundation is cleaned first, then C15-C20 lean concrete is adopted for backfilling until the foundation is flush with surrounding rock surfaces, and then the whole roughening treatment is carried out, wherein the maximum grain size of aggregate of the lean concrete is not more than 25mm; the crushed stone soil filler is doped with 0.3-0.5% of polypropylene reticular fiber, the fiber length is 12-19 mm, and the fiber is uniformly added when the filler is mixed, so that the shrinkage crack of the filler is inhibited, and the integrity of the filler is improved.
9. The multistage reinforcement construction method of the granite high-fill subgrade of claim 1, wherein sedimentation monitoring points are synchronously distributed in the monitoring process of the step S4, and a real-time safety coefficient evaluation model of the overall stability of the subgrade is established by combining the filling height, the slope geometric parameters and the filler physical mechanical parameters of the subgrade based on the data acquired by the deep horizontal displacement monitoring points and the sedimentation monitoring points so as to simplify the Bishop method; Setting a two-stage early warning threshold value, namely, when F s is less than or equal to 1.30 and is less than or equal to 1.50, sending out primary early warning, starting a primary performance compensation measure, namely, temporarily improving the tensile strength of the geogrid by 20% -30% on the basis of the original design in a reinforcement layer paved next time, when F s is less than or equal to 1.30 and is less than or equal to 1.20, sending out advanced early warning, starting a secondary performance compensation measure, namely, synchronously piling up sand bags at the slope toe of a corresponding area of the roadbed on the basis of implementing the primary performance compensation measure, and applying a temporary back pressure load of 20 kPa% -35 kPa; And carrying out inversion analysis on the parameters of the packing cohesion c and the internal friction angle phi in the evaluation model by utilizing the displacement and sedimentation data acquired in the time period, and carrying out fine adjustment on the model parameters according to inversion results for subsequent more accurate prediction.
10. The method for multistage reinforcement construction of granite land high-fill roadbed according to claim 9, wherein the process of fine tuning model parameters by inversion analysis and inversion results comprises: In a 24-hour encryption monitoring period after the primary or secondary performance compensation measures are completed, acquiring a horizontal displacement increment sequence { delta d i } and a sedimentation increment sequence { delta s i } of each monitoring point in the period, and simultaneously recording the newly-added filling thickness delta H in the period; Constructing an inverse analysis objective function taking a filler cohesion c and an internal friction angle phi as optimization variables by taking the horizontal displacement increment sequence and the sedimentation increment sequence as system responses, wherein the objective function is the sum of squares of residuals of a calculated value and a monitored value, namely ： Minimize: Σ[ (Δd i,cal - Δd i,mea ) 2 + (Δs i,cal - Δs i,mea ) 2 ],(d i,cal , Δs i,cal ) is the calculated value, (delta d i,mea , Δs i,mea ) is the monitored value, and the calculated value (delta d i,cal , Δs i,cal ) is obtained by substituting a candidate (c, phi) parameter set into a displacement prediction model expanded by the simplified Bishop method for iterative calculation; and (3) solving the objective function by adopting a Monte Carlo-steepest descent mixing algorithm to obtain a group of optimal (c, phi) parameters which enable the calculated response to be closest to the actual monitoring response, and updating the original filler mechanical parameters in the evaluation model by using the optimal parameters (c, phi) obtained by inversion.

Description

Multistage reinforcement construction method for granite high-fill roadbed Technical Field The invention relates to the technical field of civil engineering roadbed construction. More particularly, the invention relates to a multistage reinforcement construction method for a granite ground high-filling roadbed. Background In the construction of high-fill foundations on granite formations, several technical difficulties are often faced. The granite surface is generally compact and smooth, and has obvious differences in physical and mechanical properties with the roadbed filling material filled on the upper part. The difference causes weaker interface bonding performance of the two, and relative slippage is easy to generate on the contact surface, so that the two are potential weak links, and the overall stability of the roadbed is affected. Conventional cleaning methods or simple leveling processes often have difficulty effectively improving the bonding problem between such rigid and flexible materials. The high fill subgrade itself is heavily loaded and can create significant additional stresses during construction and use. This not only places demands on the load carrying capacity of the underlying foundation, but also places higher standards on compaction and drainage of the foundation packing itself. Conventional layered filling and compaction methods sometimes have difficulty ensuring uniformity of the internal compactness of the high-fill body, and if the internal pore water pressure cannot be timely dissipated, foundation consolidation can be delayed, and uneven settlement can be caused. In addition, the traditional construction quality control mainly depends on the post-compaction degree detection, and lacks of real-time grasp of the internal stress and deformation state of the roadbed in the filling process. For reinforcement of the filling body, a mode of paving reinforced materials such as geogrids is often adopted. However, under higher fill loads and possible lateral deformation, the interfacial friction of the reinforcement material and filler may be insufficient, resulting in the reinforcement being pulled out or failing to fully exert its tensile strength, thereby impairing the reinforcing effect. Meanwhile, dynamic changes in the construction process, such as fluctuation of filler properties, gradual increase of loads and the like, enable the safety state of the roadbed to be in continuous change. The traditional monitoring mode based on the design of fixed parameters and the staged acceptance is difficult to capture the gradual change process of stability in time and send out early warning before critical state, and often remedial measures are taken when obvious deformation signs appear, and the difficulty and cost of adjustment are both increased. Disclosure of Invention It is an object of the present invention to solve at least the above problems and to provide at least the advantages to be described later. To achieve these objects and other advantages and in accordance with the purpose of the invention, there is provided a method for multi-stage reinforcement construction of a granite land high-fill subgrade, comprising the steps of: s1, foundation treatment, namely cleaning and roughening the surface of a granite stratum, wherein the roughening depth is 8-15 mm, and a rough joint surface is formed; s2, constructing a transition layer, namely paving a cement-bentonite slurry transition layer on the rock surface after roughening, and uniformly spreading a layer of machine-made sand with the grain diameter of 5-10 mm before slurry initial setting to form an enhanced bonding interface; S3, setting a first layer filling and drainage system, namely setting a vertical drainage system after paving and compacting a first layer filling layer, wherein the filling layer is gravelly soil with the thickness of 0.3-0.5 m, rolling for 6-8 times at the speed of 2-4 km/h by using a vibratory roller, and the compactness reaches 95-97%, and arranging plastic drainage belts of a multi-strip filter membrane according to square grids, and inserting the plastic drainage belts to penetrate the filling layer in depth and contact with a granite stratum; S4, performing layered filling and reinforcement, namely performing reinforcement layer paving, water-permeable gravel layer paving, filler layer paving and compaction on a first filler layer, repeating the steps until the design elevation, wherein the reinforcement layer comprises a geogrid and a portal anchor rod, the tensile strength of the geogrid is 80kN/m to 120kN/m, the geogrid is tensioned and fixed during paving, the lap joint width is 0.4m to 0.5m, the portal anchor rod is immediately used for anchoring after paving, the arrangement interval of the portal anchor rod is 1.5m to 2.0m, two supporting legs of the portal anchor rod are driven into the filler layer, steel backing plates are arranged on a transverse rod to tightly press the geogrid on the surfa