CN114808923B - Cave grouting construction treatment method - Google Patents

Abstract

The invention discloses a cave grouting construction treatment method, which adopts different modes for grouting according to different cave sizes and types. Specifically, cement slurry is injected into the first cave through the corresponding grouting holes; when cement slurry is injected, the grouting pressure is increased step by step from a preset first initial pressure until reaching a preset first grouting final pressure, and grouting is performed for multiple times; injecting cement mortar into the second cave through the corresponding grouting holes; when cement mortar is injected, the grouting pressure is increased step by step from a preset second initial pressure until reaching a preset second grouting final pressure; the second initial pressure is greater than the first initial pressure, and the second grouting final pressure is greater than the first grouting final pressure. And after grouting of the grouting holes reaches a preset condition, finishing grouting of the grouting holes. Grouting treatment is carried out on the cave, so that the foundation is effectively reinforced. Different modes are adopted for grouting aiming at cavities with different sizes and types, and the grouting effect is good.

Description

Cave grouting construction treatment method

Technical Field

The invention relates to the field of buildings, in particular to a cave grouting construction treatment method.

Background

In China, the most prominent problem of karst causing harm to various engineering constructions including high-speed railways is that karst collapse or uneven subsidence is generated under the action of underground water, and diseases of karst roadbeds can be divided into two main types: one is the deformation problem and the other is the water damage problem. Especially, the design service life of the large-sized railway station house is 100 years, the foundation design standard is high, and the sedimentation requirement is strict. Therefore, the foundation of the karst development area needs to be reinforced.

Disclosure of Invention

Aiming at the technical problems, the embodiment of the invention provides a cave grouting construction treatment method which aims at reinforcing a foundation.

An embodiment provides a cave grouting construction processing method, which comprises the following steps:

surveying the foundation area to obtain the position, the size, the number and the type of the caves below the foundation area; dividing the cavities into a first cavity and a second cavity according to the size and the type of the cavities;

drilling a grouting hole communicated with the first cavity and a grouting hole communicated with the second cavity by a drilling machine;

injecting cement paste into the first cave through the corresponding grouting holes; when cement slurry is injected, the grouting pressure is increased step by step from a preset first initial pressure until reaching a preset first grouting final pressure, and grouting is performed for multiple times;

injecting cement mortar into the second cave through the corresponding grouting holes; when cement mortar is injected, the grouting pressure is increased step by step from a preset second initial pressure until reaching a preset second grouting final pressure; the second initial pressure is greater than the first initial pressure, and the second grouting final pressure is greater than the first grouting final pressure;

and after grouting of the grouting holes reaches a preset condition, finishing grouting of the grouting holes.

In the method provided by an embodiment, the first grouting final pressure is one of 1.0-1.2MPa, and the grouting pressure is changed within a range of 0.4-1.2 MPa during grouting cement slurry; the final pressure of the second grouting is one of 7.0-8.0MPa, and the variation range of the grouting pressure is 4.0-10.0MPa during the grouting of the cement mortar.

In the method provided in one embodiment, the dividing the cavity into a first cavity and a second cavity according to the size and type of the cavity includes:

determining the full-filled cavity as a first cavity; and/or the number of the groups of groups,

determining a half-filled or unfilled cavity with a cavity diameter of 2.0-4.0 meters as a first cavity; and/or the number of the groups of groups,

determining a beaded cavity with the hole diameter more than or equal to 4.0 meters as a first cavity; and/or the number of the groups of groups,

and determining the half-filled or unfilled cavity with the cavity diameter more than or equal to 4.0 meters as a second cavity.

In the method provided by an embodiment, the cement slurry is prepared from: 42.5 grade Portland cement and water, 1:1, the mass ratio is prepared; the cement mortar adopts plain cement mortar with the mark between M10 and M20.

In the method provided in one embodiment, the drilling machine drills a grouting hole communicated with a first cavity and a grouting hole communicated with a second cavity, and the method comprises the following steps:

calibrating positions of corresponding drilling holes of the first cave and the second cave according to preset design requirements;

moving the drilling machine to a calibrated drilling position, and adjusting the angle of the drilling machine to enable the drilling machine to be vertical after the drilling machine is in place;

the pore-forming adopts a geological drilling method of full-pore coring, the pore diameter of the pore is not less than 110mm, and the pore diameter of the final pore is not less than 91mm; filling a drilling record in the drilling process, recording whether the hole turns over water and leaks water in the drilling process, dividing soil layers, and orderly placing cores according to the sequence of return times.

In the method provided in an embodiment, further comprising:

after the drilling is finished, a conduit is put into the drilling to the bottom of the drilling, water is introduced, and the drilling is washed outwards from the bottom of the drilling through water flow until clear water is returned for 5-10 min; wherein the flushing pressure is 80% of the grouting pressure.

In the method provided in one embodiment, the preset condition includes at least one of the following three types:

the grouting orifice pressure is basically maintained at 1.0MPa, and the pressure is stabilized for 10min;

the grouting point is 3-5m outside the grouting range;

the single-hole grouting amount is 1.5-2.0 times of the average grouting amount, and the grouting amount is reduced.

In the method provided in an embodiment, further comprising:

selecting a plurality of grouting holes, and performing a water pressing test on the selected grouting holes before grouting and after grouting to obtain the water absorption capacity of unit length; compared with the water absorption capacity of unit length before grouting, if the water absorption capacity of unit length after grouting is reduced by 95-99%, the grouting effect is obvious.

In the method provided in an embodiment, further comprising:

drilling holes in the estimated grouting diffusion range after grouting is completed to verify the grouting diffusion range, and measuring by a standard penetration method in a cave, wherein the standard penetration value reaches 10 hits to be qualified.

In the method provided in one embodiment, the method includes:

when the grouting is performed from the lower part to the upper part, if the grouting pressure is not changed or is changed from large to small, the grouting pressure does not reach the preset pressure after the grouting is performed for a preset time period, and the amplitude of the grouting quantity exceeding the preset grouting quantity exceeds a preset threshold value, and judging that the cave is an open cave;

detecting the boundary of the open cave again, and after determining the boundary, injecting a waterproof curtain by adopting double liquid slurries at the periphery of the boundary, wherein the waterproof curtain adopts intermittent grouting for 1-4 times in a batch-to-batch grouting mode for 6-10 hours.

According to the cave grouting construction treatment method provided by the embodiment of the invention, grouting is performed in different modes according to different cave sizes and types. Specifically, cement slurry is injected into the first cave through the corresponding grouting holes; when cement slurry is injected, the grouting pressure is increased step by step from a preset first initial pressure until reaching a preset first grouting final pressure, and grouting is performed for multiple times; injecting cement mortar into the second cave through the corresponding grouting holes; when cement mortar is injected, the grouting pressure is increased step by step from a preset second initial pressure until reaching a preset second grouting final pressure; the second initial pressure is greater than the first initial pressure, and the second grouting final pressure is greater than the first grouting final pressure. And after grouting of the grouting holes reaches a preset condition, finishing grouting of the grouting holes. Grouting treatment is carried out on the cave, so that the foundation is effectively reinforced. Different modes are adopted for grouting aiming at cavities with different sizes and types, and the grouting effect is good.

Drawings

FIG. 1 is a flow chart of an embodiment of a method for processing a cavity grouting construction provided by the invention;

FIG. 2 is a detailed flow diagram of the method for processing the grouting construction of the cave according to the invention;

FIG. 3 is a specific flow chart of step 2;

FIG. 4 is a schematic illustration of the effect of karst grouting profile.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.

The cave grouting construction treatment method provided by the invention is suitable for projects such as railways, highways, house buildings and the like in which foundation reinforcement treatment is required in karst development areas; the method is suitable for projects with large underground water fluctuation and strict settlement control after foundation construction. The method mainly comprises the steps of drilling and grouting a karst foundation to fill cavities (such as soil cavities, karst cavities and corrosion cracks); and (3) sealing the soil and stone interface to form a waterproof curtain, and blocking the connection between upper-layer stagnant water and karst water to prevent the collapse of the foundation. The details are set forth below with respect to some examples.

As shown in fig. 1 and 2, the method (construction process) for processing the grouting construction of the cave provided by the invention comprises the following steps:

step 1, a construction preparation step, which comprises the following steps: collecting and investigating specific positions of underground facilities and underground pipelines to related departments before construction; the electromechanical equipment is fixed in place, the electric part is provided with a net cover, and the electric box wires are hung; surveying the foundation area to obtain the position, the size, the number and the type of the caves below the foundation area; the cavities are divided into a first cavity and a second cavity by the size and type of cavity. Wherein the cavity comprises at least one of a soil cavity, a karst cave, a karst ditch, a fluid bowl, and an erosion slit, the embodiment is described by taking the karst cave as an example.

Drilling holes at a plurality of points in the foundation area to obtain punching data. After drilling, according to the rock, soil layer and the like taken out from the drilling, whether various information such as soil holes, karst holes, grooves, cracks, stratum distribution and the like exists at the drilling position can be found. And the boundary of the cave range is determined by drilling, the boundary is marked, the cave range is circled, and the position, the size, the number and the type of the cave below the foundation area are obtained by combining the data of drilling and soil taking.

And analyzing the plane and vertical distribution characteristics of the karst (soil) cave, the solution groove, the solution crack and the like according to the investigation result, and determining the karst treatment method according to the size of the cave body, the characteristics of the karst cave filler and the hydrogeological conditions. For large-scale hole bodies and medium-scale hole bodies, the method of cement mortar filling is mainly adopted for treatment. For a karst ditch, a karst cave-in area and a foundation uniformity mutation area affected by karst, a consolidation or reinforcement mode is mainly adopted to build a uniform foundation, so that accidents such as 'planting', 'collapse', 'dumping' and the like are prevented from occurring in construction equipment; for small-sized hole bodies and joint and corrosion cracks which possibly generate surges, grouting treatment is mainly carried out by adopting a single-liquid slurry sleeve valve pipe. When the foundation pit is in water burst and water burst during construction, the foundation pit is segmented for system reinforcement.

According to the karst development conditions disclosed by the detailed investigation drilling and the advanced drilling, and by combining engineering structure characteristics, a more suitable karst foundation treatment method is comprehensively analyzed and selected. For example, the cavity division may be performed substantially as follows:

(1) The fully filled cavity is defined as a first cavity.

(2) A half-filled or unfilled cavity having a hole diameter between 2.0 and 4.0 meters is defined as a first cavity.

(3) The beaded cavity with the hole diameter more than or equal to 4.0 meters is determined as a first cavity.

For the first cave, sleeve valve pipe grouting can be adopted for follow-up, and single-liquid cement slurry is adopted as grouting materials.

(4) And determining the half-filled or unfilled cavity with the cavity diameter more than or equal to 4.0 meters as a second cavity. For the second cavity, a filling method, namely drilling holes as feeding holes to be filled with cement mortar, is adopted in the follow-up, and the filling material is low-grade cement mortar (M10-M20).

Step 2, a drilling step, which comprises the following steps: the drilling machine drills a grouting hole communicated with the first cavity and a grouting hole communicated with the second cavity. The method comprises the procedures of lofting hole sites, installing a drilling machine, perforating, casing consolidation, drilling, final hole/pressurized water experiment, quality inspection and the like. Specifically, as shown in fig. 3, the method comprises the following steps:

step 21, hole site lofting: and calibrating the positions of the corresponding drilling holes of the first cave and the second cave according to preset design requirements. The drilling in the step 1 is used for exploring a cave, and the drilling in the step 2 is used for drilling grouting holes. The construction site is measured to check the horizontal elevation of the site, the hole site lofting adopts a method of measuring specific hole sites by controlling piles, and the deviation of the hole site lofting is ensured to be less than 50cm, namely, the deviation of the positions of corresponding drilling holes of the first cave and the second cave is ensured to be less than 50cm.

And 22, after the grouting hole site is calibrated, the drilling machine is moved to the calibrated drilling position, and after the drilling machine is positioned, the angle of the drilling machine is adjusted by using tools such as an inclined ruler, a horizontal ruler and the like, so that the drilling machine is vertical, is firmly installed and is stably positioned.

And 23, after the drilling machine is installed, the center of the vertical shaft, the center of the orifice pipe and the center of the hole site are consistent, and the azimuth and the design are consistent. The drilling uses long and thick diameters, and the thick diameter of the substitution guide is suitable for deep holes. The drilling machine needs to be firmly installed, and is stable and fixed in positioning. Wherein, the drill rod is started after the verticality deviation of the drill rod is not more than 1%, the hole position deviation is not more than 0.5m, and the hole forming quality is ensured. The fixed pipeline should be installed nearby for various devices, and is not suitable for overlong so as to prevent pressure and flow consumption.

The hole is formed by adopting a geological drilling method of full-hole coring, the hole diameter of the hole is not less than 110mm (namely, the hole diameter is more than or equal to 110 mm), and the hole diameter of the final hole is not less than 91mm (namely, the hole diameter of the final hole is more than or equal to 91 mm). When earth is covered on the earth surface, in order to prevent the orifice from collapsing or shrinking, an orifice pipe can be arranged downwards or a following pipe can be adopted for drilling. Filling a drilling record in the drilling process, recording whether the hole turns over water and leaks water in the drilling process, dividing a soil layer, orderly placing the cores according to the sequence of the cores, and simultaneously taking care of protecting the cores until grouting is completed.

And monitoring the hole inclination, and when the hole inclination exceeds a preset specified requirement, comprehensively analyzing by combining grouting data and quality inspection conditions of the part, for example, taking remedial measures such as plugging the hole, re-drilling and the like when determining the exact influence on grouting quality. The hole position deviation should not exceed 50cm.

When the drilled hole falls down and blocks, a cavity crack and a lost stratum are difficult to drill, the reason for part finding is determined, grouting treatment can be performed first, drilling can be performed later, and a grouting hole forming mode from top to bottom can be adopted.

And after the hole is formed, grouting is waited, the hole opening is plugged and capped, and the hole opening is properly protected.

And 24, after the drilling is finished, a grouting pipe is downwards placed in the drilling to the bottom of the hole, a grouting machine is connected, clean water is pumped to clean the hole, and the hole is washed outwards from the bottom of the hole through water flow until the clean water is returned for 5-10 min. The pipe diameter of the grouting pipe can be selected from 50mm to 130mm, grouting is performed by adopting the pipe diameter in the pipe diameter range based on design requirements and actual conditions, grouting effect can be controlled under the condition of effectively controlling grouting pressure and slurry proportion, and the pipe is convenient to purchase. The thickness of the hole bottom sediment is obtained by measuring the difference between the measured value of the rope and the recorded depth of the drilled hole, and if the thickness of the hole bottom sediment exceeds 20cm, the hole bottom sediment is continuously washed by clean water until the thickness of the hole bottom sediment does not exceed 20cm; the flushing pressure was 80% of the final grouting pressure. And after the flushing is finished, grouting can be performed.

And 2, drilling to obtain grouting holes of all cavities such as karst cave. Before grouting, a water pressing test is carried out, and technological parameters such as material proportion, grouting pressure and the like are adjusted. Grouting is still needed after the drilling detection of the pressurized water test is completed. Specifically, a plurality of grouting holes are selected, and a water pressing test is carried out on the selected grouting holes before grouting, so that the water absorption capacity of unit length is obtained. The water absorption per unit length refers to the water absorption per unit time (L/min) of a test section per unit length (1 m) under a pressure of 0.01MPa (or 1m water column).

Step 3, grouting step, including: and (3) inserting a grouting pipe into the grouting hole, and timely plugging the orifice (a gap between the grouting hole and the grouting pipe) and a nearby ground crack to prevent grouting. If these operations have been completed in step 24, the grouting is performed directly. And (3) injecting cement slurry into the first cave through the grouting pipes in the corresponding grouting holes, wherein the grouting flow rate can be controlled to be 30-75L/min. Cement mortar is injected into the second cave through the grouting pipes in the corresponding grouting holes, and the grouting flow rate can be determined according to the actual condition of the site, so that pipe blockage in the grouting process is avoided.

The grouting sequence in karst areas directly affects the grouting compactness of karst (earth) holes and karst cracks and the slurry loss of grouting, and the grouting sequence is preferably as follows:

1) The construction sequence of the hole treatment should follow: detecting boundary-grouting filling-grouting effect detection.

2) The sequential separate injection should be followed, that is, the mode of adopting different grouting sequences according to the different sizes of karst cave is followed, and the small cave is sequentially injected from outside to inside: namely, a plurality of grouting holes are drilled in the small holes, grouting is performed through the grouting holes close to the boundary, and grouting is performed through the grouting holes close to the center of the hole; big holes are big inside first, big outside first, small first, and big bottom then, big top then: namely, the grouting pipe is inserted into the bottom of a large karst cave (the large karst cave and the small karst cave are relative concepts), and grouting slurry is filled from the bottom of the karst cave gradually upwards to fill the large karst cave; grouting pressure is small and then large. If the grouting amount is large when the periphery Kong Zhudi is grouted once, grouting can be performed in a jump-by-jump mode when the pressure does not meet the design requirement, and then grouting is performed on the holes which are not grouted for the first time.

Because the unit grouting amount is closely related to grouting hole distance, grouting pressure, slurry concentration and karst development degree, in the embodiment, on-site grouting test is carried out before grouting construction, a grouting process is reasonably selected, related parameters such as grouting pressure, slurry proportion and unit grouting amount are reasonably determined, and grouting stopping conditions and the like are determined. The following is a detailed description.

Specifically, 42.5-grade ordinary Portland cement is adopted, and the mass ratio of cement to water is 1:1, preparing cement paste. The cement mortar adopts plain cement mortar with the reference number between M10 and M20. The grouting slurry is fully and uniformly stirred by a stirrer and then is slowly stirred continuously in the grouting process, and the stirring time is less than the initial setting time of the slurry. The slurry should be filtered through a screen before being pumped. The experimenter is responsible for monitoring the mixing of the slurry on site and carrying out sampling detection so as to ensure the mixing quality of the slurry. The vat and grouting lines must not be exposed to sunlight to prevent the slurry from setting. In other words, sunshade is carried out on the pulp containing barrel and the grouting pipeline.

The invention adopts cement paste and cement mortar, the cement paste is mainly cement and sand, and the source is wide. Under the condition of high flow rate of groundwater or high water content of soil or high strength requirement of concretes, a proper amount of additive can be mixed into cement so as to achieve the effects of quick setting, high strength, freezing resistance, corrosion resistance, no precipitation of slurry and the like.

When cement slurry is injected, the grouting pressure is increased step by step from a preset first initial pressure until reaching a preset first grouting final pressure, and grouting is performed for multiple times. In other words, the grouting pressure is carried out according to the principles of initial small pressure and final large pressure, namely the pressure is gradually increased at proper grading intervals, and the grouting is gradually increased for a plurality of times by the first relatively small pressure. The grouting control pressure is generally 0.4-1.2 MPa, namely the variation range of the grouting pressure is 0.4-1.2 MPa during the period of grouting cement paste; grouting for 3-4 times. The final pressure of the first grouting is generally controlled to be 1.0-1.2MPa. Therefore, the invention adopts graded pressurization according to different geological conditions, can adjust the pressure suitable for grouting of the hole, and ensures the grouting effect and safety.

When cement mortar is injected, the grouting pressure is gradually increased from a preset second initial pressure until reaching a preset second grouting final pressure. In other words, the grouting pressure is carried out according to the principles of initial small pressure and final large pressure, namely the pressure is gradually increased at proper grading intervals, and the grouting is gradually increased for a plurality of times by the first relatively small pressure. The grouting pressure is generally controlled to be 4.0-10.0MPa, namely, the grouting pressure is changed to be 4.0-10.0MPa during the period of injecting cement mortar. The final pressure of the second grouting is generally controlled between 7.0 and 8.0MPa. It can be seen that the second initial pressure is significantly greater than the first initial pressure and the second grouting end pressure is significantly greater than the first grouting end pressure. And the pressure suitable for grouting of the hole can be adjusted by adopting graded pressurization, so that the grouting effect and safety are ensured.

During grouting construction, an automatic flow and pressure recording meter is adopted, and flow and pressure data are tidied and analyzed in time. The flow and pressure are controlled as much as possible in the grouting process, so that the slurry is prevented from losing. When the grouting pump is started or closed, the chemical grouting pump must be started or closed firstly so as to avoid blocking the pipeline.

The whole grouting process is used for recording, arranging and analyzing technical data and basic data. The grouting process strengthens ground observation records (horizontal displacement, positions of grouting points, ground subsidence and the like). The grouting process takes care of environmental protection and timely cleans slurry pollutants. After finishing the field level, temporary drainage facilities are usually finished around the grouting field level. In the karst grouting construction area, ground observation is enhanced, ground deformation monitoring is carried out every day during construction, the measured ground deformation is measured, the measurement accuracy is not more than 1mm, detailed records are made, grouting pressure is controlled according to observation data, and stability of a cut slope or safety of nearby structures is not affected.

And step 4, judging whether grouting of the grouting holes reaches a preset condition, and if so, ending grouting of the grouting holes. The preset conditions may include at least one of the following three:

the grouting orifice pressure is basically maintained at 1.0MPa, and the pressure is stabilized for 10min;

the grouting point is 3-5m outside the grouting range;

the single-hole grouting amount is 1.5-2.0 times of the average grouting amount, the grouting amount is obviously reduced, and if a field technician observes obvious changes before and after the grouting amount, a conclusion that grouting of the grouting hole needs to be finished is obtained.

If grouting of the grouting holes does not reach the preset condition, grouting is performed again by cleaning the holes. Specifically, grouting is continuously performed for a preset time, if the period of time does not reach the ending standard, hole cleaning and grouting are performed again, and the preset time can be set according to the needs, for example, half an hour.

In karst grouting construction, aiming at the condition that grouting holes cannot reach grouting end conditions all the time, the following measures are adopted by analyzing the formed reasons:

(1) The large karst cave is encountered in the pore-forming process to collapse the pore:

1) If the hole collapse is not serious after a large karst cave is encountered in construction, backfilling the mixture of the sheet stone and the clay blocks.

2) If the whole hole collapses, after the collapse is stabilized, clay is used for backfilling the hole to the ground surface, and karst cave pretreatment is carried out after compaction, wherein the treatment method is the same as that of the karst cave. And after the karst cave pretreatment is finished, re-making holes, namely restarting the cave grouting construction treatment on the cave.

(2) When the soil hole is dissolved and grouting is carried out, the slurry is seriously run:

when grouting is performed from the lower part to the upper part of the cave, if grouting pressure is not changed or is changed from large to small, grouting is performed for a preset time period, the pressure does not reach the preset pressure (for example, grouting is not performed for a period of time), the grouting amount exceeds the preset grouting amount by a magnitude exceeding a preset threshold value (the grouting amount is far greater than the estimated calculated amount), and the cave is judged to be an open cave. And detecting the boundary of the open cave again, and after determining the boundary, injecting a waterproof curtain by adopting double liquid slurries at the periphery of the boundary, wherein the waterproof curtain adopts intermittent and fractional grouting, and the intermittent time is 6-10 hours, and the grouting is carried out for 1-4 times. The double-liquid slurry can be formed by mixing cement slurry and water glass slurry, and the mass ratio of the cement slurry to the water glass slurry is 1:0.5 to 1: 1. And after the waterproof curtain is constructed, hole jumping grouting is performed from outside to inside.

(3) In the field implementation process, if large-area collapse occurs due to a large karst cave, or if the large karst cave exists or the large-area collapse is expected to occur before implementation, the construction unit should be quickly connected with related departments, and the corresponding countermeasures are adopted on the field for remedying.

And carrying out a pressurized water test on the grouting holes selected before after grouting to obtain the water absorption capacity of unit length. Compared with the water absorption capacity of unit length before grouting, if the water absorption capacity of unit length after grouting is reduced by 95-99 percent (the water absorption capacity of unit length before and after grouting is greatly different), the grouting effect is obvious; otherwise, the grouting effect is not obvious, and if the grouting effect is not obvious, hole washing grouting is performed again. And adopting a pressurized water test to check grouting effect, and evaluating grouting effect according to quality check results and construction process data.

Drilling holes in the estimated grouting diffusion range after grouting is completed to verify the grouting diffusion range, and measuring by a standard penetration method in a cave, wherein the standard penetration value reaches 10 hits to be qualified.

Therefore, the invention adopts karst grouting to carry out foundation reinforcement treatment. The risk of collapse of pile foundations during construction can be effectively reduced after karst grouting treatment; the risk of rapid development of the soil hole under the action of groundwater is prevented, and the risk of later operation is reduced; the damage of the sudden and gushed water to the surrounding construction and structure of the foundation pit when the foundation pit is excavated by the unaddressed cave and karst channel is prevented, the capability of the sandy soil foundation for resisting the karst local collapse is improved, and the safety of the station structure is improved.

According to the construction process provided by the invention, the karst foundation is subjected to drilling grouting to fill soil holes, karst holes and corrosion cracks; and (3) sealing the soil and stone interface to form a waterproof curtain, and blocking the connection between upper-layer stagnant water and karst water to prevent the collapse of the foundation.

When grouting, cement slurry or mortar enters the karst cave under the pressure condition, so that the slurry is uniformly diffused in the karst cave, the filler of the karst cave is glued into a whole, risks of ground subsidence, collapse and the like are reduced, and construction safety is ensured; meanwhile, the bearing capacity of the foundation is improved, the safety of the station structure is improved, and the later operation safety is ensured.

The karst grouting is applied to projects such as railways, highways, house buildings and the like which are suitable for the karst development area and need to be subjected to foundation reinforcement treatment; the application effect on the geological conditions such as close communication of surface water and underground water, poor foundation stability and the like is obvious.

Compared with other geological treatment methods, the construction process of the invention has the advantages of simpler process, smaller operation difficulty, faster construction and flexible required operation equipment. The method comprises the following steps:

(1) The construction method carries out grouting treatment on the found karst cave, and for grouting cement paste, a background can be connected with a plurality of grouting pipes, a plurality of grouting holes are used for grouting simultaneously, the construction efficiency is high, and the labor cost is saved.

(2) The method has the advantages that the karst cave grouting construction is carried out before pile foundation construction, the karst cave is filled densely, risks of ground subsidence, subsidence and the like are reduced, and construction safety is ensured; meanwhile, the bearing capacity of the foundation is improved, the safety of the station structure is improved, the operation safety of the railway station is ensured, and good social benefits are formed.

From the field practice, the construction method is flexible and mobile, the construction machinery is simple, a large number of machines can be simultaneously carried out, the construction method has great advantages under the conditions of a certain period of time and a certain number of mechanical equipment, the model of the machine in construction is single, and the construction quality is easy to be ensured. Through field practice, the grouting effect can completely meet the requirement, has better effect on foundation reinforcement and post-construction settlement control, and has better social benefit, economic benefit and popularization value.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. The cave grouting construction treatment method is characterized by comprising the following steps of:

surveying the foundation area to obtain the position, the size, the number and the type of the caves below the foundation area; dividing the cavities into a first cavity and a second cavity according to the size and the type of the cavities; wherein the dividing the cavity into a first cavity and a second cavity according to the size and type of the cavity comprises: determining the full-filled cavity as a first cavity; and/or determining a half-filled or unfilled cavity with a cavity diameter between 2.0 and 4.0 meters as a first cavity; and/or, determining a beaded cavity with the hole diameter more than or equal to 4.0 meters as a first cavity; and/or determining a half-filled or unfilled cavity with a cavity diameter of more than or equal to 4.0 meters as a second cavity;

drilling a grouting hole communicated with the first cavity and a grouting hole communicated with the second cavity by a drilling machine;

injecting cement paste into the first cave through the corresponding grouting holes; when cement slurry is injected, the grouting pressure is increased step by step from a preset first initial pressure until reaching a preset first grouting final pressure, and grouting is performed for multiple times;

injecting cement mortar into the second cave through the corresponding grouting holes; when cement mortar is injected, the grouting pressure is increased step by step from a preset second initial pressure until reaching a preset second grouting final pressure; the second initial pressure is greater than the first initial pressure, and the second grouting final pressure is greater than the first grouting final pressure;

and after grouting of the grouting holes reaches a preset condition, finishing grouting of the grouting holes.

2. The method of claim 1, wherein the first grouting end pressure is one of 1.0 to 1.2MPa, and the grouting pressure varies in a range of 0.4 to 1.2MPa during grouting of cement slurry; the final pressure of the second grouting is one of 7.0-8.0MPa, and the variation range of the grouting pressure is 4.0-10.0MPa during the grouting of the cement mortar.

3. The method of claim 1, wherein the cement slurry is prepared from: 42.5 grade Portland cement and water, 1:1, the mass ratio is prepared; the cement mortar adopts plain cement mortar with the mark between M10 and M20.

4. The method of claim 1, wherein the drilling a grouting hole in communication with a first cavity and a grouting hole in communication with a second cavity, comprises:

calibrating positions of corresponding drilling holes of the first cave and the second cave according to preset design requirements;

moving the drilling machine to a calibrated drilling position, and adjusting the angle of the drilling machine to enable the drilling machine to be vertical after the drilling machine is in place;

the pore-forming adopts a geological drilling method of full-pore coring, the pore diameter of the pore is not less than 110mm, and the pore diameter of the final pore is not less than 91mm; filling a drilling record in the drilling process, recording whether the hole turns over water and leaks water in the drilling process, dividing soil layers, and orderly placing cores according to the sequence of return times.

5. The method as recited in claim 4, further comprising:

after the drilling is finished, a conduit is put into the drilling to the bottom of the drilling, water is introduced, and the drilling is washed outwards from the bottom of the drilling through water flow until clear water is returned for 5-10 min; wherein the flushing pressure is 80% of the grouting pressure.

6. The method of claim 1, wherein the preset conditions include at least one of the following three:

the grouting orifice pressure is basically maintained at 1.0MPa, and the pressure is stabilized for 10min;

the grouting point is 3-5m outside the grouting range;

the single-hole grouting amount is 1.5-2.0 times of the average grouting amount, and the grouting amount is reduced.

7. The method as recited in claim 1, further comprising:

selecting a plurality of grouting holes, and performing a water pressing test on the selected grouting holes before grouting and after grouting to obtain the water absorption capacity of unit length; compared with the water absorption capacity of unit length before grouting, if the water absorption capacity of unit length after grouting is reduced by 95-99%, the grouting effect is obvious.

8. The method as recited in claim 1, further comprising:

drilling holes in the estimated grouting diffusion range after grouting is completed to verify the grouting diffusion range, and measuring by a standard penetration method in a cave, wherein the standard penetration value reaches 10 hits to be qualified.

9. The method according to claim 1, characterized in that it comprises:

when the grouting is performed from the lower part to the upper part, if the grouting pressure is not changed or is changed from large to small, the grouting pressure does not reach the preset pressure after the grouting is performed for a preset time period, and the amplitude of the grouting quantity exceeding the preset grouting quantity exceeds a preset threshold value, and judging that the cave is an open cave;

detecting the boundary of the open cave again, and after determining the boundary, injecting a waterproof curtain by adopting double liquid slurries at the periphery of the boundary, wherein the waterproof curtain adopts intermittent grouting for 1-4 times in a batch-to-batch grouting mode for 6-10 hours.