Design method for reinforcing highway subgrade in goaf under irregular complex geological conditions

Abstract

The invention provides a goaf highway subgrade reinforcement design method under irregular complex geological conditions, which belongs to the technical field of building construction, and comprises the following steps: drilling system design, grouting system design and grouting construction process design. Meanwhile, in the grouting hole construction process, the drilling speed, the grout leakage condition, the drill dropping condition and the like in the drilling process are recorded in detail, scheme optimization is conducted once according to the construction condition after each sequence of grouting hole construction is completed, the workload is recalculated, the treatment scheme is optimized, and construction is monitored through a monitoring intelligent grouting system in the whole process; accurate control and remote management of the grouting process are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of construction engineering, and more particularly to a design method for reinforcing the roadbed of a highway in a goaf under irregular and complex geological conditions. Background Art

[0002] The design of the foundation reinforcement of the roadbed in the goaf is an important link to ensure the long-term stability and safe operation of the highway in the goaf. The main design methods include the following: grouting method, full-fill pressure grouting method, dry (mortar) masonry support method, excavation and backfilling method, roadway reinforcement method, dynamic compaction method, horizontal directional multi-branch drilling grouting reinforcement technology, etc. Among them, the full-fill pressure grouting method is suitable for the reinforcement of larger goafs. By grouting to reinforce the surrounding rock mass, the foundation stability can be improved. However, when encountering a goaf with irregular and complex geological conditions, the conventional design and treatment methods cannot meet the design requirements. Summary of the Invention

[0003] The purpose of the present invention is to provide a design method for reinforcing the roadbed of a highway in a goaf under irregular and complex geological conditions, so as to solve the problem that the conventional design and treatment methods cannot meet the design requirements when encountering a goaf with irregular and complex geological conditions in the prior art as mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A design method for reinforcing the roadbed of a highway in a goaf under irregular and complex geological conditions, comprising the following steps:

[0006] S100. Drilling system design: The drilling is carried out in a form of interval and sequence, and is divided into two stages: The first-stage drilling is in the range from the ground to 6 m below the complete bedrock; the second-stage drilling is from 6 m below the complete bedrock to 2 m below the floor of the goaf; and the installation of steel casing is carried out after the completion of the first-stage drilling.

[0007] S200. Grouting system design: The grouting system includes a material yard, a primary mixer, a secondary mixer, a water supply system, a grouting pump, a pressure gauge, a grouting pipeline and a sand feeding funnel; it also includes grouting hole design, grouting volume design, and slurry mix ratio design.

[0008] The grouting hole design: The designed depth of the grouting hole is from the ground surface to several meters below the floor of the goaf, and the plane is arranged with curtain grouting holes and ordinary grouting holes respectively.

[0009] The grouting volume design: The total grouting volume Q 总 is calculated according to the following formula:

[0010]

[0011] In the formula: S - the treatment area of the goaf, unit m2 ; M - average mined thickness of the ore layer, unit: m; ΔV - remaining void ratio of the mined - out area, %; K - recovery rate, %; A - slurry loss coefficient; η - filling rate, %; c - slurry stone formation rate, %; a - dip angle of the rock stratum, unit: °

[0012] The design of the grouting liquid: The grouting liquid includes ordinary grouting liquid and curtain grouting liquid. The ordinary grouting liquid is cement powder and coal ash slurry; the curtain grouting liquid is made by adding a quick - setting agent to the ordinary grouting slurry.

[0013] S300. Design of the grouting construction technology

[0014] (1) Fixing points: Loft all the hole positions and do a good job in marking the on - site hole positions, and record the original ground elevation of the specific on - site hole positions.

[0015] (2) Drilling holes and installing casing pipes: The drilling sequence is carried out in the way of first the edge, then the center, and first deep and then shallow; after drilling, install the steel casing pipe in the hole.

[0016] (3) Installing the grouting pipe and casting the orifice pipe: The orifice pipe consists of a flange plate and a grouting pipe. Before installing the grouting pipe, weld one end of the grouting pipe to the flange plate, and leave a movable grouting pipe joint at the other end. When installing, lower the flange - plate end into the variable - diameter part of the grouting hole, then use a small amount of crushed stone and fine sand to block the gap between the flange plate and the hole wall, and then cement the grouting pipe and the steel casing pipe together with cement slurry; the next grouting operation can be carried out only after the poured cement slurry has fully solidified.

[0017] (4) Grouting: First, carry out the grouting construction of the curtain holes. After the curtain hole grouting is completed, then carry out the construction of the ordinary grouting holes. The curtain hole grouting is constructed by the intermittent grouting method; the grouting hole grouting is constructed by the one - time full - hole grouting method.

[0018] (5) Terminating grouting: After the full - hole grouting is completed, pull out the grout - stopping facilities, pour thick cement slurry into the hole from the orifice. After the slurry reaches the orifice, seal the hole to end.

[0019] Furthermore, in the grouting hole design in step S100, the ordinary grouting holes are arranged in a plum - blossom pattern along the highway center line and on both sides; the curtain grouting holes are arranged in a row along the edge of the mined - out area treatment.

[0020] Furthermore, in step S100, the deviation between the drilled hole and the designed hole position is controlled within 0.5 m.

[0021] Furthermore, in step S100, after the drilling is completed, carry out hole flushing to ensure that the sediment at the bottom of the hole does not block the effective grouting area.

[0022] Furthermore, in step S100, after the installation of each steel casing pipe, the top surface is 0.2 m higher than the ground elevation, and the bottom is 6 m from the ground to the complete bedrock.

[0023] Further, in step S200, the water-solid ratio of the ordinary grouting liquid is 1:1.0 to 1:1.3, cement accounts for 30% of the solid phase, and fly ash accounts for 70% of the solid phase; the curtain grouting liquid is made by adding 2% of a quick-setting agent to the ordinary grouting liquid.

[0024] Further, during the grouting process in step S300, when adjacent holes are connected by slurry, if the grouted hole is in a condition suitable for grouting, the two holes are grouted simultaneously; if it is not in a suitable condition for grouting, the slurry connection hole is blocked. After the grouting of the grouting hole is completed, the slurry connection hole is reamed and flushed, and then grouting is carried out.

[0025] In summary, the beneficial effects of the present invention are as follows:

[0026] 1. When designing the drilling system of the present invention, an interval and sequential form is adopted, and drilling is carried out in two stages. After the drilling in the first stage is completed, the installation of steel casing can form a protection wall to effectively prevent the collapse of the hole wall, and solve problems such as slurry leakage, inclination, and sticking of the drill during the drilling process, ensuring the smooth progress of the drilling in the second stage;

[0027] 2. When designing the grouting system of the present invention, the grouting volume is calculated according to a formula. The formula takes into account S - the treatment area of the goaf; M - the average mined thickness of the ore layer; ΔV - the remaining void ratio of the goaf; K - the recovery rate; A - the slurry loss coefficient; η - the filling rate; c - the stone formation rate of the slurry; a - the influence of the rock stratum dip angle on the total grouting volume Q total, and accurately calculates its quantity.

[0028] 3. When designing the grouting construction process of the present invention, the technological process of fixed-point, hole formation and casing lowering, grouting pipe lowering, casting of the orifice pipe, grouting, and termination of grouting is adopted. At the same time, during the construction of the grouting hole, the drilling speed, slurry leakage situation, drill dropping situation, etc. during the drilling process are recorded in detail. After the construction of each sequence of grouting holes is completed, the plan is optimized according to the construction situation, the workload is recalculated and the treatment plan is optimized, and the construction is monitored by using a monitoring intelligent grouting system throughout the process, realizing the precise control and remote management of the grouting process.

[0029] 4. The design of the drilling system is the basis of the grouting system. The diameter, depth, and layout of the drilling holes will all affect the grouting process. The drilling system is designed in such a way that the first-stage drilling is in the range from the ground to 6 m below the complete bedrock; the second-stage drilling is from 6 m below the complete bedrock to 2 m below the goaf floor; and the steel casing is installed after the first-stage drilling is completed, ensuring the slurry distribution and penetration effect during grouting. The grouting construction process design is the actual construction process design based on the above two systems. The combined design of the above grouting system and drilling system, plus the control of the construction process in the actual engineering application, enables the reinforcement of the highway subgrade in the goaf with irregular and complex geological conditions to meet the design requirements. Brief Description of the Drawings

[0030] Figure 1 is a flowchart of the design and disposal method of the present invention. Detailed Embodiments

[0031] The following describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments given here are only for illustrating and explaining the present invention and should not be used to limit the present invention.

[0032] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may have other embodiments and variations, and therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0033] The highway subgrade foundation of the present invention is built in a mined-out area with irregular and complex geological conditions. After detailed investigation, it is determined that there are houses, factories and other buildings, small undulating low mountains and reverse slope rivers (usually no surface water runoff, but there is surface runoff during extremely heavy rainstorms and it lasts for a period of time) on the surface of the area. According to the above geological conditions, the treatment method is designed to adopt the full filling pressure grouting method.

[0034] As Figure 1 shown, the design method for strengthening the highway subgrade in a mined-out area under irregular and complex geological conditions includes the following steps:

[0035] S100. Drilling system design: The drilling is in the form of interval sequencing and is divided into two stages: The first-stage drilling is in the range from the ground to 6 m below the complete bedrock; the second-stage drilling is from 6 m below the complete bedrock to 2 m below the floor of the mined-out area; and steel casing installation is carried out after the first-stage drilling is completed; the hole deviation per 100 m should be less than 2°.

[0036] Arrange 3 - 5% of the drill holes for full coring to guide the drilling and grouting construction. For the full coring holes, the core recovery rate in the caving zone of the mined-out area should not be less than 30%, and the core recovery rate in other areas should not be less than 60%.

[0037] S200. Grouting system design: The grouting system includes a material yard, a primary mixer, a secondary mixer, a water supply system, a grouting pump, a pressure gauge, a grouting pipeline and a sand feeding funnel; it also includes grouting hole design, grouting volume design, and slurry mix ratio design;

[0038] The grouting hole design: The designed depth of the grouting hole is from the ground to several meters below the floor of the mined-out area. The grouting of the hole mouth pipe uses a 50 mm steel pipe. When aggregate needs to be put in, the pipe diameter should not be less than 89 mm, and the length of the grouting pipe is the depth from the ground to 6.0 m below the complete bedrock.

[0039] The plane is arranged with curtain grouting holes and ordinary grouting holes respectively;

[0040] The design of the grouting volume: The total grouting volume Q 总 is calculated according to the following formula:

[0041]

[0042] In the formula: S - the treatment area of the goaf, unit m 2 ; M - the average mined thickness of the ore seam, unit m; ΔV - the remaining void ratio of the goaf %; K - the recovery rate %; A - the slurry loss coefficient; η - the filling rate %; c - the stone formation rate of the slurry %; a - the dip angle of the rock stratum, unit °;

[0043] The design of the grouting liquid: The grouting liquid includes ordinary grouting liquid and curtain grouting liquid. The ordinary grouting liquid is cement powder and coal ash slurry; the curtain grouting liquid is made by adding a quick-setting agent to the ordinary grouting slurry;

[0044] S300. Design of the grouting construction process

[0045] (1) Fixing points: Use GPS to lay out the positions of all holes and do a good job in marking the hole positions on site. Record the original ground elevation of the specific hole positions on site. The principle error of the actual drilling position should not exceed 0.5 m;

[0046] (2) Hole formation and casing installation: The drilling sequence is carried out in the way of first the edge, then the center, and first deep and then shallow; after drilling is completed, install the steel casing in the hole;

[0047] (3) Installing the grouting pipe and casting the hole mouth pipe: The hole mouth pipe consists of a flange and a grouting pipe. Before installing the grouting pipe, weld one end of the grouting pipe to the flange and leave a movable grouting pipe joint at the other end. When installing, lower the flange end into the variable diameter part of the grouting hole, and then use a small amount of crushed stone and fine sand to seal the gap between the flange and the hole wall. Then use 1:2 cement slurry (add 2% of the cement weight of the quick-setting agent to the cement slurry) to bond the grouting pipe and the steel casing together to achieve the functions of rapid consolidation and slurry stoppage; the pouring height of the cement slurry is not less than 6 m, and the next grouting process can be carried out only after the poured cement slurry has fully solidified;

[0048] (4) Grouting: First carry out the grouting construction of the curtain holes. After the grouting of the curtain holes is completed, then carry out the construction of the ordinary grouting holes. The grouting of the curtain holes is constructed by the intermittent grouting method; the grouting of the ordinary grouting holes is constructed by the one-time grouting method for the whole hole.

[0049] (5) Terminating grouting: After the whole hole grouting is completed, pull out the slurry stoppage facilities, pour thick cement slurry into the hole from the hole mouth, and seal the hole after the slurry reaches the hole mouth.

[0050] During construction, in the grouting hole design described in step S100, the ordinary grouting holes are arranged in a plum blossom pattern along the center line and both sides of the road; the curtain grouting holes are arranged in a row along the edge of the goaf treatment area.

[0051] During construction, in step S100, the deviation between the drilled hole and the designed hole position is controlled within 0.5 m.

[0052] During construction, in step S100, after the drilling is completed, hole flushing is carried out to ensure that the sediment at the bottom of the hole does not block the effective grouting area.

[0053] During construction, in step S100, after the installation of each steel casing, the top surface is 0.2 m higher than the ground elevation, and the bottom is 6 m from the ground to the complete bedrock.

[0054] During construction, in step S200, the water-solid ratio of the ordinary grouting liquid is 1:1.0 - 1:1.3, cement accounts for 30% of the solid phase, and fly ash accounts for 70% of the solid phase; the curtain grouting liquid is made by adding 2% of the accelerating agent to the ordinary grouting liquid, so that the curtain grouting liquid injected into the goaf can solidify as soon as possible to form a curtain and prevent the loss of the curtain grouting liquid.

[0055] During construction, in the grouting process of step S300, when adjacent holes are grouted in series, if the grouted hole is in a condition suitable for grouting, the two holes are grouted simultaneously; if it is not in a suitable condition for grouting, the series-grouted hole is blocked. After the grouting of the grouting hole is completed, the series-grouted hole is reamed and flushed, and then grouted.

[0056] During construction, before the grouting construction, 3% - 5% of the total number of designed grouting holes are selected at each goaf treatment site for on-site grouting tests, and the test contents include the slurry ratio, hole-forming process, grouting equipment, grouting construction process, etc.

[0057] After the completion of the test section, the construction process and grouting parameters of the grouting treatment are adjusted according to the test results. The grouting holes are first constructed along the holes at the edge of the deep goaf in the dip direction, and the construction process from deep to shallow is adopted, and it should be carried out in a sequential and interval manner, and is designed in a way of three-sequence skip drilling. During the construction of the grouting holes, the drilling speed, slurry leakage situation, drill dropping situation, etc. during the drilling process are recorded in detail. After the construction of each sequence of grouting holes is completed, the plan is optimized according to the construction situation, the workload is recalculated, the treatment plan is optimized, and the construction is monitored by the intelligent grouting monitoring system throughout the process.

[0058] It should be understood that the above embodiments are one or more embodiments of the present invention. Based on the present invention, there are many other embodiments and their deformations; when ordinary technicians in this industry do not make pioneering innovations, the deformations and modifications made through the present invention all fall within the protection scope of the present invention.

Claims

1. A design method for reinforcing the highway subgrade in a mined - out area under irregular and complex geological conditions, characterized in that, It includes the following steps: S100. Drilling system design: The drilling is carried out in a form of interval sequencing and is divided into two stages: The first-stage drilling is in the range from the ground to 6 m below the complete bedrock; the second-stage drilling is from 6 m below the complete bedrock to 2 m below the floor of the goaf. And the installation of steel casing is carried out after the completion of the first-stage drilling. S200. Grouting system design: The grouting system includes a material yard, a primary mixer, a secondary mixer, a water supply system, a grouting pump, a pressure gauge, grouting pipes and a sand-feeding funnel; it also includes grouting hole design, grouting volume design and slurry mix ratio design. The grouting hole design: The designed depth of the grouting hole is several meters from the ground surface to below the floor of the goaf, and the plane is arranged with curtain grouting holes and ordinary grouting holes respectively. The design of the grouting volume: The total grouting volume Q 总 is calculated according to the following formula: Where: S - the treated area of the goaf, unit m 2 ; M - the average mined thickness of the ore seam, unit m; ΔV - residual void ratio of the goaf %, K - recovery rate %, A - slurry loss coefficient η - filling rate %, c - slurry stone formation rate %, a - dip angle of the rock stratum, unit ° The grouting liquid design: The grouting liquid includes ordinary grouting liquid and curtain grouting liquid. The ordinary grouting liquid is a mixture of cement powder and coal ash slurry; the curtain grouting liquid is made by adding a quick-setting agent to the ordinary grouting slurry. S300. Grouting construction process design (1) Fixing points: Loft all hole positions and do a good job in marking the on-site hole positions, and record the original ground elevation of the specific hole positions on-site. (2) Hole forming and casing installation: The drilling sequence is carried out in the way of first the edge, then the center, and first deep and then shallow; after the drilling is completed, install the steel casing in the hole. (3) Installing the grouting pipe and casting the hole mouth pipe: The hole mouth pipe consists of a flange and a grouting pipe. Before installing the grouting pipe, weld one end of the grouting pipe to the flange and leave a movable grouting pipe joint at the other end. During installation, lower the flange end into the variable diameter part of the grouting hole, then use a small amount of crushed stone and fine sand to block the gap between the flange and the hole wall, and then cement the grouting pipe and the steel casing together with cement slurry; the next grouting process can be carried out only after the poured cement slurry has fully solidified. (4) Grouting: First carry out the curtain hole grouting construction, and then carry out the ordinary grouting hole construction after the curtain hole grouting is completed. The curtain hole grouting is constructed by the intermittent grouting method; the grouting hole grouting is constructed by the full-hole one-time grouting method. (5) Terminating grouting: After the full-hole grouting is completed, pull out the grout stopping facilities, pour thick cement slurry into the hole from the hole mouth, and seal the hole after the slurry reaches the hole mouth.

2. The method for designing the reinforcement of the goaf highway subgrade under irregular and complex geological conditions according to claim 1, characterized in that: In the grouting hole design described in step S100, the ordinary grouting holes are arranged in a plum blossom shape along the highway center line and on both sides; the curtain grouting holes are arranged in a row along the treatment edge of the goaf.

3. The design method for reinforcing the highway subgrade in a mined - out area under irregular and complex geological conditions according to claim 2, characterized in that: In step S100, the deviation between the drilling hole and the designed hole position is controlled within 0.5 m.

4. The design method for reinforcing a goaf highway subgrade under irregular and complex geological conditions according to claim 3, characterized in that: In step S100, after the drilling is completed, carry out hole flushing to ensure that the bottom sediment of the hole does not block the effective grouting area.

5. The goaf highway subgrade reinforcement design method under irregular and complex geological conditions according to claim 4, characterized in that: In step S100, after the installation of each steel casing, the top surface is 0.2 m higher than the ground elevation, and the bottom is from the ground to 6 m below the complete bedrock.

6. The goaf highway subgrade reinforcement design method under irregular and complex geological conditions according to claim 1, characterized in that: In step S200, the water-solid ratio of the ordinary grouting liquid is 1:1.0 - 1:1.3, the cement accounts for 30% of the solid phase, and the fly ash accounts for 70% of the solid phase; the curtain grouting liquid is made by adding 2% of the quick-setting agent to the ordinary grouting liquid.

7. The design method for reinforcing the highway subgrade in a mined - out area under irregular and complex geological conditions according to claim 1, characterized in that: During the grouting process in step S300, when slurry leakage occurs between adjacent holes, if the grouting conditions are met for the hole receiving the leaked slurry, grouting is carried out for both holes simultaneously; if the grouting conditions are not met, the hole receiving the leaked slurry is blocked. After the grouting of the grouting hole is completed, the hole receiving the leaked slurry is reamed and flushed, and then grouting is carried out.

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