A method for karst foundation treatment, protection and grouting reinforcement

Abstract

The present invention relates to a method for treating and protecting a karst foundation by grouting reinforcement, including: dividing the area to be treated into at least one reinforcement block; S2, setting grouting holes in each reinforcement block, detecting the correlation of karst cavities, and dividing the grouting holes into grouting holes with obvious connection of karst cavities and grouting holes with non-obvious connection of karst cavities; S3, first grouting the key reinforcement area, and then grouting the peripheral reinforcement area; during the grouting process, first grout the grouting holes with obvious connection of karst cavities, and adopt the bag-type grout stopper closed grouting method for grouting, and then grout the grouting holes with non-obvious connection of karst cavities, and adopt the in-hole drainage and slurry circulation grouting method for grouting. The present invention respectively adopts targeted grouting reinforcement according to the connectivity of karst cavities, overcomes the deficiency that the current grouting for buildings on soluble gypsum rock formations does not subdivide the existing karst differences, can effectively drain the stagnant water in the rock layer, and has a better grouting reinforcement effect.

Description

Technical Field

[0001] The present invention relates to the technical field of karst ground collapse treatment, in particular to a grouting reinforcement method for karst foundation treatment and protection, belonging to the technical field of urban building maintenance. Background Art

[0002] Karst ground collapse is a common geological environment problem during the development of underground space in urban concealed karst areas. Due to the gradual dissolution of soluble gypsum rock under the karst ground affected by flowing water for a long time, dissolution holes will be formed in the soluble gypsum rock formation. When the dissolution holes reach a certain scale, the upper rock layer will partially lose the bottom support, showing local depression or fragmentation, that is, shallow fragmentation and subsidence, and fine cracks will be left at different vertical depths, that is, non-connected cracks are also formed in the non-gypsum rock layer. Furthermore, it will cause the softening and local voiding of the soil at the bottom of the shallow foundation, and finally lead to uneven settlement of the buildings above the stratum.

[0003] When the soluble gypsum rock formation subsides, it is necessary to timely treat and protect the building foundation on the formation. At present, the treatment and protection of karst foundations mainly adopt grouting methods for reinforcement. The principle of grouting reinforcement is to make the slurry continuously diffuse in the karst fissures through drilling and grouting. As the grouting holes are gradually densified, the karst fissures are continuously filled until the building settlement is stable. Since the existing grouting methods carry out grouting reinforcement through strong pressure penetration and have no treatment measures for the stagnant water in the rock layer, the stagnant water in the dissolution holes or fissures will cause the slurry in the holes to be unable to be fully filled. For example, when treating dissolution holes with strong connectivity, although the grouting volume is large, it is difficult to build pressure, resulting in poor grouting effect; when treating isolated fissures, the grouting volume is small but it is easy to build pressure, and it is difficult to discharge the fissure water. In both of the above situations, the grouting effect is poor, and it is impossible to effectively achieve rapid settlement stopping of the building, and it may further dissolve the gypsum rock. For sulfate rock, there are obvious differences in the dissolution rate and dissolution amount between mirabilite and gypsum under the same conditions. The mirabilite-bearing rock layer is more likely and faster to form dissolution holes, and the connectivity is stronger. Therefore, the existing grouting methods cannot achieve the purpose of treatment and protection for karst foundations. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that the existing grouting methods for karst foundations do not consider the different connectivity of different dissolution holes, resulting in poor grouting effect and inability to effectively achieve the treatment and protection of the foundation. The present invention provides a grouting reinforcement method for karst foundation treatment and protection. The grouting method of the present invention for soluble gypsum rock formation can effectively improve the grouting efficiency and quality, and achieve rapid treatment and protection of the building foundation.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] A grouting reinforcement method for karst foundation treatment and protection, comprising the following steps:

[0007] S1. Divide the area to be treated into at least one reinforcement block according to the basic type and the building settlement condition. The reinforcement block includes a key reinforcement area and a peripheral reinforcement area.

[0008] S2. Set grouting holes in each reinforcement block, and detect the correlation of the dissolution holes between each grouting hole and its adjacent grouting holes. According to the detection results, divide the grouting holes into grouting holes with obvious connection of dissolution holes and grouting holes with non - obvious connection of dissolution holes.

[0009] S3. First, grout the key reinforcement area, and then grout the peripheral reinforcement area. During the grouting process of the key reinforcement area or the peripheral reinforcement area, first grout the grouting holes with obvious connection of dissolution holes, and then grout the grouting holes with non - obvious connection of dissolution holes. For the grouting holes with obvious connection of dissolution holes, adopt the grouting method of sealing with a capsule - type grout stopper. For the grouting holes with non - obvious connection of dissolution holes, adopt the grouting method of draining water in the hole and circulating the grout.

[0010] The method for preventing settlement of the soluble gypsum - rock formation structure of the present invention first divides the area to be treated into different reinforcement blocks, namely the key reinforcement area and the peripheral reinforcement area. First, set grouting holes in each reinforcement block. Since there are large differences in the dissolution amount and dissolution rate of the soluble gypsum - rock formation when encountering water, the soluble gypsum - rock formation is relatively easy to dissolve, and after being carried away by water, it forms holes with strong connectivity. By judging the correlation of the dissolution holes in each grouting hole, and adopting different grouting processes according to different dissolution degrees in different grouting sections, first grout the key reinforcement area, and then grout the peripheral reinforcement area. During the grouting process of the key reinforcement area or the peripheral reinforcement area, first grout the grouting holes with obvious connection of dissolution holes, and then grout the grouting holes with non - obvious connection of dissolution holes. For the grouting holes with obvious connection of dissolution holes, adopt the grouting method of sealing with a capsule - type grout stopper for full - diffusion perfusion; for the grouting holes with non - obvious connection of dissolution holes, adopt the grouting method of draining water in the hole and circulating the grout. Before grouting the grouting holes, the stagnant water in the holes is discharged from the grouting holes by the pressurized grout, so that the grout fills the grouting holes and the surrounding fissures. The present invention takes targeted grouting and settlement prevention according to the connectivity of the dissolution holes, overcoming the deficiency that there is no detailed classification for the existing grouting of buildings on the soluble gypsum - rock formation for the existing dissolution differences.

[0011] As a preferred solution of the present invention, the karst foundation is located in the soluble gypsum - rock formation. More specifically, the soluble gypsum - rock formation is a mirabilite - gypsum formation.

[0012] As a preferred solution of the present invention, the reinforcement block includes a key reinforcement area and a peripheral reinforcement area. The buildings with serious settlement are located in the key reinforcement area. There is at least one building with serious settlement in each key reinforcement area. The peripheral reinforcement area is the area obtained by removing the key reinforcement area from the area to be treated. The areas without buildings and / or the buildings with minor settlement are located in the peripheral reinforcement area.

[0013] As a preferred embodiment of the present invention, the method for determining the correlation between the corrosion cavities at different depths in each grouting hole is as follows: when underground confined water gushes out of the grouting hole, it is determined that the correlation between the grouting hole and the adjacent grouting hole is that the corrosion cavities are significantly connected; when there is no obvious groundwater gushing in the grouting hole, the pigment method, the salt injection method, the temperature and resistivity method are used to determine that the correlation between the grouting hole and the adjacent grouting hole is that the corrosion cavities are significantly connected or the corrosion cavities are not significantly connected.

[0014] After the buildings in the soluble gypsum rock formation are affected by the long-term erosion of the flowing water in the underground layer, the gypsum rock layer of the building foundation gradually corrodes. In addition to containing gypsum (CaSO 4 ·2H 2 O) and anhydrite (CaSO 4 ), mirabilite (Na 2 SO 4 ) or glauberite (Na 2 SO 4 ·CaSO 4 ) are locally associated. Both mirabilite and gypsum will be eroded as the groundwater flows. When the corrosion cavities reach a certain scale, the upper rock layer loses local bottom support, showing local depression or fragmentation, and leaving fine cracks at different vertical depths, which further causes the softening and local voiding of the soil at the bottom of the shallow foundation, resulting in uneven settlement of the building. Therefore, it is necessary to use the tracer method to detect the connectivity of the grouting holes in the soluble gypsum rock formation of the building foundation, determine the connectivity of the grouting holes at each position, and directly using the conventional grouting reinforcement method cannot achieve the effect of stopping settlement.

[0015] As a preferred embodiment of the present invention, in the grouting design of the key reinforcement area, for the grouting holes with significantly connected corrosion cavities, the hole spacing of the grouting holes is 8 - 15 m, the grouting holes are arranged in a plum blossom shape, and the depth of the grouting holes is the depth of the confined water level; for the grouting holes with non-significantly connected corrosion cavities, the grouting holes are closed, the hole spacing of the grouting holes is 6 - 8 m, and the depth of the grouting holes exceeds the depth of the formation with obvious corrosion cavities and fissures.

[0016] As a preferred embodiment of the present invention, in the grouting design of the peripheral reinforcement area, for the grouting holes with significantly connected corrosion cavities, the hole spacing of the grouting holes is 8 - 15 m, the grouting holes are arranged in a plum blossom shape, and the depth of the grouting holes is the depth of the confined water level; for the grouting holes with non-significantly connected corrosion cavities, the grouting holes are closed, the hole spacing of the grouting holes is 6 - 8 m, and the depth of the grouting holes exceeds the depth of the formation with obvious corrosion cavities and fissures.

[0017] As a preferred embodiment of the present invention, in S2, when the dissolution holes are significantly connected to the grouting holes, the first grouting material is used for grouting reinforcement. The first grouting material is made of a material with high resistance to sulfate corrosion, and is a mixture of sulfate-resistant portland cement and a setting accelerator. The water-cement ratio of the sulfate-resistant portland cement is 1:0.8 - 1.5, and the content of tricalcium aluminate in the sulfate-resistant portland cement does not exceed 3%. According to the connectivity of the dissolution holes in the grouting holes, for different degrees of dissolution and connectivity, the dosage of the setting accelerator is determined. The dosage of the setting accelerator is 0.8 - 1.5‰ of the dry weight of the sulfate-resistant portland cement, and the initial setting time of the first grouting material is 15 - 30 min. Since C3A and its hydration products are most vulnerable to sulfate attack, for grouting materials that require high resistance to sulfate corrosion, sulfate-resistant portland cement with a low C3A content is selected as the main material. By optimizing the hydration products and pore structure, the resistance to sulfate attack is improved.

[0018] Further, the setting accelerator is polyacrylamide or sodium silicate.

[0019] Further, the initial setting time of the first grouting material is 20 min, the setting accelerator used is polyacrylamide, and the dosage of the setting accelerator is 1‰ of the dry weight of the sulfate-resistant portland cement. The dosage of the setting accelerator can not only ensure the setting time of the first grouting material but also ensure the diffusion performance.

[0020] As a preferred embodiment of the present invention, when the dissolution holes are not significantly connected to the grouting holes, the second grouting material is used for grouting reinforcement. The second grouting material is made of a material with high resistance to sulfate corrosion, and is a mixture of sulfate-resistant portland cement and an admixture. The water-cement ratio of the sulfate-resistant portland cement is 1:0.8 - 1.5, and the permeability coefficient of the second grouting material is 5.0×10 -5 ~1.0×10 -3 cm / s, the fluidity of the second grouting material is 40 - 50 mm, the bleeding rate of the second grouting material is not more than 3%, and the initial setting time of the second grouting material is 1.5 h - 3 h. Excessive bleeding rate will cause the slurry to stratify and affect the grouting effect. For non-significantly connected grouting holes, during the grouting process, the second grouting material adopts a non-setting accelerator formula and adds an admixture that can meet both the penetration performance and the bleeding rate to prevent the slurry from having a short setting time and premature setting, which may prevent the filling of isolated holes or cracks, and ensure the filling effect of non-significantly connected grouting holes with dissolution holes.

[0021] As a preferred embodiment of the present invention, the admixture includes a water reducer, a retarder, and a water retention agent. During use, the dosages of different admixtures are adjusted according to the performance requirements of the second grouting material to reasonably control the fluidity and setting time of the slurry.

[0022] As a preferred embodiment of the present invention, in S3, the grouting reinforcement is carried out by using a bladder-type grout plug for grouting sealing, and the specific steps are as follows:

[0023] An anti-water plate is arranged on the upper surface of the grouting hole, an orifice tube is inserted into the grouting hole, and the space between the grouting hole and the orifice tube is filled with an orifice sealing material;

[0024] The grout inlet pipe and the bladder-type grout plug are connected in sequence, and the bladder-type grout plug is set at the end of the section to be grouted in the grouting hole; the bladder-type grout plug is composed of a perforated steel pipe and an expanding rubber plug, and the perforated steel pipe is provided with slurry overflow holes; the grout inlet pipe and the bladder-type grout plug are placed into the grouting hole;

[0025] The grouting equipment is started, and the slurry of the first grouting material is injected into the bladder-type grout plug through the grout inlet pipe. After the bladder-type grout plug expands, it is tightly pressed against the inner wall of the grouting hole to form an in-hole grout sealing system;

[0026] Continue grouting. After the grouting pressure reaches the end standard pressure, stop grouting, relieve the pressure of the bladder-type grout plug, rotate the grout inlet pipe, and then pull out the grout inlet pipe and the bladder-type grout plug.

[0027] As a preferred embodiment of the present invention, during the grouting process, a relatively large grouting pressure is selected, which can be 1 - 3 MPa.

[0028] As a preferred embodiment of the present invention, in S3, the grouting reinforcement is carried out by using an in-hole drainage and slurry circulation grouting method, and the specific steps are as follows:

[0029] An anti-water plate is arranged on the upper surface of the grouting hole, an orifice tube is inserted into the grouting hole, and the space between the grouting hole and the orifice tube is filled with an orifice sealing material; a return liquid pipe is arranged at the upper end of the orifice tube, the return liquid pipe is communicated with the orifice tube, and a return slurry valve is arranged on the return liquid pipe to control the opening and closing of the end of the return liquid pipe far from the orifice tube;

[0030] The grout inlet pipe is placed into the orifice tube, and the return slurry valve is opened to connect the return liquid pipe; the grouting equipment is started, and the slurry of the second grouting material is grouted into the grouting hole through the grout inlet pipe, and the grouting pressure and speed are controlled; the slurry diffuses in the grouting hole to fill the corrosion cavities, and the return slurry valve is closed after sufficient filling;

[0031] Continue grouting. After the grouting pressure reaches the end standard pressure, stop grouting, rotate the grout inlet pipe, and then pull out the grout inlet pipe.

[0032] In the above technical solution, a return liquid pipe is arranged at the upper end of the orifice tube. Before grouting, the stagnant water in the hole is drained as much as possible through the return slurry valve. The pressurized slurry first discharges the excess stagnant water in the hole through the return slurry valve out of the site, so that the slurry fully fills the grouting hole and the surrounding fissures to form a consolidated body, improving the density and bearing capacity of the formation.

[0033] As a preferred embodiment of the present invention, during the grouting process, the grouting pressure is controlled not to exceed 1 MPa.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. The grouting method for karst foundation treatment and protection of the present invention first divides the area to be treated into different reinforcement blocks, namely the key reinforcement area and the peripheral reinforcement area. Grouting holes are set in each reinforcement block. Since there are significant differences in the dissolution amount and dissolution rate of soluble gypsum rock formations when encountering water, the soluble gypsum rock formations are relatively easy to dissolve, and after being carried away by water, relatively well-connected holes are formed. By judging the relevance of the dissolution holes in each grouting hole, different grouting processes are adopted according to the different dissolution degrees in different grouting sections. First, grouting is carried out in the key reinforcement area, and then in the peripheral reinforcement area. During the grouting process in the key reinforcement area or the peripheral reinforcement area, grouting is first carried out for the grouting holes with significantly connected dissolution holes, and then for the grouting holes with non-significantly connected dissolution holes. For the grouting holes with significantly connected dissolution holes, the bag-type grout stopper closed grouting method is adopted for full diffusion grouting; for the grouting holes with non-significantly connected dissolution holes, the in-hole drainage and slurry circulation grouting method is adopted. Before grouting the grouting hole, the stagnant water in the hole is first discharged from the grouting hole by pressurized slurry, so that the slurry fills the grouting hole and the surrounding fissures. The present invention respectively adopts targeted grouting reinforcement according to the connectivity of the dissolution holes, overcoming the deficiency that the existing grouting for buildings on soluble gypsum rock formations does not subdivide the existing dissolution differences.

[0036] 2. The method of the present invention overcomes the problem that the existing single treatment method of orifice sealing and in-hole circulation, strong pressure penetration grouting reinforcement may further dissolve the gypsum rock. By using the present invention, the stagnant water in the rock layer can be effectively discharged, enabling the slurry in the hole to be fully filled, and the grouting reinforcement effect is better, achieving the purpose of treatment and protection.

[0037] 3. For the grouting of significantly connected dissolution holes, the first grouting material with a quick-setting formula is used, which can not only ensure the quick-setting time but also ensure the diffusion performance, preventing waste caused by the infinite loss of the dissolution channel; for the grouting of non-significantly connected dissolution holes, the second grouting material without a quick-setting formula is used, with a permeability coefficient of 5.0×10 -5 ~1.0×10 -3 cm / s, a fluidity of 40 - 50 mm, a bleeding rate of not more than 3%, and an initial setting time of 1.5 h - 3 h, which can not only meet the penetration performance but also meet the bleeding rate requirements, and fully fill the isolated holes or fissures.

[0038] 4. The existing grouting reinforcement for karst foundations only considers treatment and does not consider that the closure of the original hydraulic channels may cause the migration of groundwater runoff channels, resulting in the generation of new corrosion in the slightly corroded areas of the strata and the formation of new corrosion-connected areas, which will lead to secondary settlement of the building in the later stage and the inability to achieve the reinforcement of the foundation. The grouting reinforcement method of the present invention grouts the corrosion holes in the slightly corroded areas that are not significantly connected to the grouting holes, uses the second grouting material to form a corrosion-blocking effect, and the present invention takes preventive measures in advance to avoid secondary settlement of the building in the later stage.

[0039] Figure 1 It is a schematic diagram for analyzing the settlement principle of buildings in the concealed karst area;

[0040] Figure 2 It is a schematic diagram of grouting holes in the key reinforcement area and the peripheral reinforcement area;

[0041] Figure 3 It is a schematic diagram of the structure for closing the grouting pipeline with a capsule-type grout plug;

[0042] Figure 4 It is a schematic diagram of the structure of the in-hole circulating grouting pipeline;

[0043] Description of the markings in the figure:

[0044] In Figure 1 : L1 - non-plaster rock layer, L2 - plaster rock layer (including mirabilite and gypsum layer), (A) - strongly connected holes, (B) - non-connected fractures;

[0045] Figure 2 And Figure 3 : 1 - water-resistant slab, 2 - hole pipe, 3 - grouting hole, 4 - grout inlet pipe, 5 - pressure gauge, 6 - grout inlet valve, 7 - hole sealing material, 8 - capsule-type grout plug, 9 - liquid return pipe, 10 - grout return valve, 11 - grout return pressure gauge. Specific embodiments

[0046] The present invention will be further described in detail below in combination with test examples and specific embodiments. However, this should not be understood as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0047] Unless otherwise specified, in the description of specific embodiments of the present invention, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / installation is commonly used. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0048] In addition, in the terms, the expressions such as "first", "second", "third", etc. are only used to distinguish the descriptions of the same or similar components, and should not be construed as emphasizing or implying the relative importance of specific components.

[0049] In addition, in the description of embodiments of the present invention, "several", "multiple", "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., and even can be a situation of more than 9.

[0050] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, where the terms "set", "installed", "connected", "linked", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. Such a connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0051] Embodiment 1

[0052] As Figure 1 shown, the building and the podium are located in the concealed karst area. Below the building is the non-gypsum layer L1, and below the non-gypsum layer L1 is the gypsum layer. In addition to containing gypsum (CaSO 4 ·2H 2 O) and anhydrite (CaSO 4 ), the gypsum stratum is locally associated with mirabilite (Na 2 SO 4 ) or glauberite (Na 2 SO 4 ·CaSO 4) is the stratum structure of mirabilite - gypsum layer. After being eroded by flowing water for a long time, the gypsum layer of the building foundation gradually corrodes. Due to the large differences in the corrosion amount and corrosion rate of mirabilite and gypsum when encountering water, the mirabilite layer is more easily corroded and forms corrosion holes (A) with strong connectivity after being carried away by flowing water. When the corrosion holes formed by deep corrosion reach a certain scale, the upper rock layer loses local bottom support, showing local depression or fragmentation, that is, shallow - layer fragmentation and subsidence, and leaving fine cracks at different vertical depths, that is, non - gypsum layers also form non - connected cracks (B). Furthermore, it causes the softening and local voiding of the soil at the bottom of the shallow foundation, ultimately leading to uneven settlement of the building above the stratum.

[0053] For Figure 1 Regarding the settlement problem of the building above the mirabilite - gypsum stratum structure shown, the grouting reinforcement method is used for treatment, so a grouting reinforcement method for treatment and protection is proposed. The specific steps are as follows:

[0054] S1. Divide the area to be treated into at least one reinforcement block according to the foundation type and the building settlement situation. The reinforcement block includes a key reinforcement area and a peripheral reinforcement area;

[0055] Before treatment, determine the area to be treated according to the building settlement situation, historical geological exploration data and the building settlement situation. The settlement situation includes the settlement area, settlement value, settlement ratio, etc. The reinforcement block includes a key reinforcement area and a peripheral reinforcement area. Buildings with severe settlement are located in the key reinforcement area. There is at least one building with severe settlement in each key reinforcement area. The peripheral reinforcement area is the area excluding the key reinforcement area in the area to be treated. Areas without buildings and / or buildings with minor settlement are located in the peripheral reinforcement area. For example, Figure 2 in the figure, there are two key reinforcement areas, and the rest are peripheral reinforcement areas. Judging whether a building has severe settlement or minor settlement is based on the existing technology in this field, such as specifications or standards.

[0056] S2. Set grouting holes in each reinforcement block, and detect the correlation of corrosion holes between each grouting hole and adjacent grouting holes. According to the detection results, divide the grouting holes into grouting holes with obvious connection of corrosion holes and grouting holes with non - obvious connection of corrosion holes;

[0057] Set different reinforcement blocks and conduct investigation and detection on each reinforcement block for subsequent grouting. Specifically: Set grouting holes in each reinforcement block, and detect the correlation between corrosion cavities at different depths in the grouting holes. The method for determining the correlation of corrosion cavities between each grouting hole and adjacent grouting holes is as follows: When underground confined water gushes out of the grouting hole, judge the correlation between the grouting hole and the adjacent grouting hole as obvious connection of corrosion cavities through the water gushing volume and the water gushing head pressure. The water gushing volume is judged according to experience; When there is no obvious groundwater gushing in the grouting hole, use methods such as the pigment method, the salt injection method, the temperature and resistivity method, etc. to judge the correlation between the grouting hole and the adjacent grouting hole as obvious connection of corrosion cavities or non - obvious connection of corrosion cavities. When conducting tracer tests using the pigment method and the salt injection method, monitor the change of tracer concentration in the water sample to judge the correlation between the grouting hole and the adjacent grouting hole as obvious connection of corrosion cavities or non - obvious connection of corrosion cavities. Then, according to the test results, judge whether the corrosion cavities in the grouting hole are obviously connected or not. For different corrosion degrees of different grouting holes, adopt different grouting processes.

[0058] S3. First, grout the key reinforcement area, and then grout the peripheral reinforcement area; During the grouting process in the key reinforcement area or the peripheral reinforcement area, first grout the grouting holes with obviously connected corrosion cavities, and then grout the grouting holes with non - obviously connected corrosion cavities. For the grouting holes with obviously connected corrosion cavities, adopt the bag - type grout stopper closed grouting method for grouting. For the grouting holes with non - obviously connected corrosion cavities, adopt the in - hole drainage and slurry circulation grouting method for grouting.

[0059] Determine the correlation of corrosion cavities of each grouting hole according to S2; Adopt different grouting methods: For the grouting holes with obviously connected corrosion cavities, adopt the bag - type grout stopper closed grouting method for grouting, which is filling - type grouting; For the grouting holes with non - obviously connected corrosion cavities, adopt the in - hole drainage and slurry circulation grouting method for grouting, which is corrosion - blocking type grouting, as Figure 2 shown. First, conduct filling - type grouting on the already corroded and penetrated area to block the formed hydraulic channel; Then conduct corrosion - blocking type grouting: Conduct corrosion - blocking type grouting around the building and around the settlement area to prevent other areas from being corroded after the migration of the hydraulic channel.

[0060] When designing the grouting in the key reinforcement area, for the grouting holes significantly connected by karst cavities, the hole spacing of the grouting holes is 8 - 15 m, the grouting holes are arranged in a plum blossom pattern, and the depth of the grouting holes is the depth of the confined water level; for the grouting holes not significantly connected by karst cavities, the grouting holes are closed, the hole spacing of the grouting holes is 6 - 8 m, and the depth of the grouting holes exceeds the depth of the strata with obvious karst cavities and fissures. It should be noted that the bottom of the grouting holes exceeds the depth of the strata with obvious karst cavities and fissures. Whether there are obvious karst cavities and fissures in this strata can be determined by the method of the correlation between karst cavities at different depths in each grouting hole as described above, or the depth of the grouting holes can be obtained according to the historical geological exploration data of the area to be treated. When designing the grouting in the peripheral reinforcement area, for the grouting holes significantly connected by karst cavities, the hole spacing of the grouting holes is 8 - 15 m, the grouting holes are arranged in a plum blossom pattern, and the depth of the grouting holes is the depth of the confined water level; for the grouting holes not significantly connected by karst cavities, the grouting holes are closed, the hole spacing of the grouting holes is 6 - 8 m, and the depth of the grouting holes exceeds the depth of the strata with obvious karst cavities and fissures. The grouting holes in the key reinforcement area and the peripheral reinforcement area can be set the same or different, which is not limited here.

[0061] For the grouting holes significantly connected by karst cavities, the bag - type grout - stopping plug grouting method is adopted for grouting. The principle of the bag - type grout - stopping plug grouting is based on the double - layer structure of the grout - stopping plug. The grout passes through the overflow holes on the grout - stopping plug to support the sealing rubber sleeve and enter the expansion rubber plug. The expansion rubber plug expands until the expansion diameter is larger than the inner diameter of the hole, thus sealing the hole wall and forming an in - hole grout - stopping system. Through high pressure, the grouting material penetrates from multiple holes of the grout - stopping plug into the grouting holes and karst cavities to achieve the grouting reinforcement effect. According to different grout - stopping methods and types of grouting pipes, the grout - stopping plugs are divided into mechanical, water - bag and air - bag type grout - stopping plugs. In this embodiment, the water - bag type grout - stopping plug is adopted. Specifically, as Figure 3 shown, the specific steps are as follows:

[0062] Set a water - resistant plate 1 on the upper surface of the grouting hole 3, insert a hole - mouth pipe 2 into the grouting hole 3, and fill the space between the grouting hole 3 and the hole - mouth pipe 2 with hole - mouth sealing material 7;

[0063] Connect the grout inlet pipe 4 and the bag - type grout - stopping plug 8 in sequence. The bag - type grout - stopping plug 8 is set at the end of the section to be grouted in the grouting hole 3. The bag - type grout - stopping plug 8 is composed of a perforated steel pipe and an expansion rubber plug. The perforated steel pipe is provided with overflow holes. A pressure gauge 5 and a grout inlet valve 6 are arranged on the grout inlet pipe 4. Put the grout inlet pipe 4 and the bag - type grout - stopping plug 8 into the grouting hole 3;

[0064] Start the grouting equipment, inject the grout of the first grouting material into the bag - type grout - stopping plug 8 through the grout inlet pipe 4. After the bag - type grout - stopping plug 8 expands, it squeezes tightly against the inner wall of the grouting hole to form an in - hole grout - stopping system;

[0065] Continue grouting. After the grouting pressure reaches the end standard pressure, stop grouting, relieve the pressure of the bladder-type grout plug 8, rotate the grout inlet pipe 4, and then pull out the grout inlet pipe 4 and the bladder-type grout plug 8.

[0066] For the grouting holes with significantly connected corrosion cavities, use the first grouting material for grouting reinforcement. The first grouting material uses a high sulfate-resistant corrosion material. The first grouting material is a mixture of sulfate-resistant portland cement and a setting accelerator. The water-cement ratio of the sulfate-resistant portland cement is 1:0.8 - 1.5. The content of tricalcium aluminate in the sulfate-resistant portland cement does not exceed 3%. According to the connectivity of the corrosion cavities in the grouting holes, determine the addition amount of the setting accelerator for different corrosion degrees and connectivity conditions. The addition amount of the setting accelerator is 0.8 - 1.5‰ of the dry weight of the sulfate-resistant portland cement. The initial setting time of the first grouting material is 15 - 30 min. The setting accelerator is polyacrylamide or sodium silicate. Preferably, the initial setting time of the first grouting material is 20 min, which can not only ensure the setting time but also ensure the diffusion performance. The used setting accelerator is polyacrylamide, and the addition amount of the setting accelerator is 1‰ of the dry weight of the sulfate-resistant portland cement.

[0067] During the grouting process, select a relatively large grouting pressure, which can be 1 - 3 MPa, specifically about 2 MPa.

[0068] For the grouting holes with non-significantly connected corrosion cavities, adopt the method of hole drainage and slurry circulation grouting for grouting reinforcement, as Figure 4 shown. The specific steps are as follows:

[0069] Set a water-resistant plate 1 on the upper surface of the grouting hole 3, insert an orifice pipe 2 into the grouting hole 3, and fill the space between the grouting hole 3 and the orifice pipe 2 with an orifice sealing material 7; a return liquid pipe 9 is provided at the upper end of the orifice pipe 2, the return liquid pipe 9 is connected to the orifice pipe 2, and a return slurry valve 10 and a return liquid pressure gauge 11 are provided on the return liquid pipe 9. The return slurry valve 10 is used to control the opening and closing of the end of the return liquid pipe 9 far from the orifice pipe 2;

[0070] Put the grout inlet pipe 4 into the orifice pipe 2, and a pressure gauge 5 and a grout inlet valve 6 are provided on the grout inlet pipe 4; open the grout inlet valve 6 and open the return slurry valve 10 to connect the return liquid pipe 9; start the grouting equipment, inject the slurry of the second grouting material into the grouting hole through the grout inlet pipe 4, and control the grouting pressure and speed; the slurry diffuses in the grouting hole, fills the corrosion cavities, and close the return slurry valve 10 after sufficient filling;

[0071] Continue grouting. After the grouting pressure reaches the end standard pressure, stop grouting, rotate the grout inlet pipe 4, and then pull out the grout inlet pipe 4.

[0072] For grouting holes with non-obvious connection of dissolution holes, the second grouting material is used for grouting reinforcement. The second grouting material is a mixture of sulfate-resistant silicate cement and admixtures. The water-cement ratio of sulfate-resistant silicate cement is 1:0.8-1.5, and the permeability coefficient of the second grouting material is 5.0×10 -5 ~1.0×10 -3 cm / s, the fluidity of the second grouting material is 40-50mm, the water seepage rate of the second grouting material is not more than 3%, the initial setting time of the second grouting material is 1.5h~3h, and the admixtures include water reducer, retarder, and water retainer. During use, the amount of different admixtures is adjusted according to the performance requirements of the second grouting material. The amount of water reducer added is 0.1%~0.5% of the dry weight of anti-sulfate silicate cement, the amount of retarder added is 0.08%~0.10% of the dry weight of anti-sulfate silicate cement, and the amount of water retainer added is 0.05%~0.2% of the dry weight of anti-sulfate silicate cement. During the grouting process of non-connected grouting holes, the grouting material adopts a slurry with a quick-setting formula, which can meet both the permeability and the water seepage rate requirements of the admixture. During the grouting process, the grouting pressure is controlled not to exceed 1MPa.

[0073] At present, the grouting reinforcement method for building settlement has no subdivision for the dissolution difference (connectivity difference) of mirabilite-gypsum strata. It mainly adopts a single treatment method of orifice closure, in-hole circulation, and segmented grouting. Grouting reinforcement is carried out by strong pressure penetration. There is no treatment measure for stagnant water in the rock stratum. Stagnant water in the pores or cracks will cause the slurry in the pores to be unable to be fully filled, which may further dissolve the gypsum rock, resulting in secondary settlement of the building in the later stage. Therefore, the scheme of the present invention is compared with the prior art, and the dissolution amount and dissolution rate of mirabilite and gypsum in water are greatly different. The mirabilite layer is easier to dissolve, and after being carried away by passive water, holes with strong connectivity are formed. The dissolution pore structures with different connectivity are distinguished. By treating different dissolution degrees of different grouting sections, different treatment process methods and grouting material formulas are adopted. The dissolution holes are obviously connected to the grouting holes, and the capsule stop plug is used to close the grouting method, and the perfusion is fully diffused. The dissolution holes are not obviously connected to the grouting holes. The hole drainage and slurry circulation grouting method are used to ensure the grouting effect under different degrees of dissolution. When grouting the highly connected erosion holes, it is avoided that the slurry has no rapid setting, and a large amount of waste is caused by the loss of the erosion channel; at the same time, when grouting the non-connected erosion holes, a formula without accelerator is adopted, the slurry will not set prematurely, and the isolated holes or cracks are fully filled, so as to achieve a high-efficiency grouting effect to prevent settlement. The present invention takes protective measures in advance to avoid secondary settlement of the building in the later stage.

[0074] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to the conventional technical manuals in the art. At the same time, for the places where the above terms appear, they can make appropriate understandings or adjustments referentially. Without creative efforts, the implementation situations of the same or similar technical solutions can be derived.

[0075] The above embodiments only describe the basic principles, main features, and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and the description in the invention content part of the specification are only the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of the present invention, there are various changes and improvements to the innovative solutions of the present invention, and these changes and improvements all fall within the scope of protection required by the present invention.

Claims

1. A grouting reinforcement method for karst foundation treatment and protection, characterized in that: The following steps are involved: S1. Divide the area to be treated into at least one reinforcement block according to the foundation type and building settlement. The reinforcement block includes a key reinforcement area and a peripheral reinforcement area. Each key reinforcement area has at least one building with severe settlement, and areas without buildings and / or buildings with slight settlement are located in the peripheral reinforcement area. S2. Grouting holes are set in each reinforcement block, and the correlation between each grouting hole and the dissolution holes between adjacent grouting holes is detected. According to the detection results, the grouting holes are divided into grouting holes with obvious dissolution holes and grouting holes with no obvious dissolution holes; S3, first grouting the key reinforcement area, and then grouting the peripheral reinforcement area; during the grouting process of the key reinforcement area or the peripheral reinforcement area, grouting is first performed for the grouting holes that are obviously connected to the grouting holes, and then grouting is performed for the grouting holes that are not obviously connected to the grouting holes; for the grouting holes that are obviously connected to the grouting holes, the grouting is performed by the closed grouting method of the capsule grouting plug, and the grouting pipe and the capsule grouting plug are connected during the grouting, and the capsule grouting plug is set at the end of the section to be grouted in the grouting hole; the capsule grouting plug It is composed of a steel tube and an expansion rubber plug. The steel tube is provided with overflow holes. The spacing between the grouting holes is 8-15m. The grouting holes are arranged in a plum blossom shape. The depth of the grouting holes is the depth of the confined water level. For the grouting holes with non-obvious connection to the dissolution holes, the grouting holes are closed. The spacing between the grouting holes is 6-8m. The depth of the grouting holes exceeds the depth of the formation with obvious dissolution holes and cracks. For the grouting holes with non-obvious connection to the dissolution holes, the hole drainage and slurry circulation grouting method are used for grouting. For the dissolution holes that are obviously connected to the grouting holes, the first grouting material is used for grouting reinforcement, the first grouting material is a mixture of sulfate-resistant silicate cement and an accelerator, the water-cement ratio of the sulfate-resistant silicate cement is 1:0.8-1.5, the content of tricalcium aluminate in the sulfate-resistant silicate cement does not exceed 3%, the amount of the accelerator added is 0.8-1.5‰ of the dry weight of the sulfate-resistant silicate cement, and the initial setting time of the first grouting material is 15-30min; for the dissolution holes that are not obviously connected to the grouting holes, the second grouting material is used for grouting reinforcement, the second grouting material is a mixture of sulfate-resistant silicate cement and an admixture, the water-cement ratio of the sulfate-resistant silicate cement is 1:0.8-1.5, and the permeability coefficient of the second grouting material is 5.0×10 -5 ~1.0×10 -3 cm / s, the fluidity of the second grouting material is 40-50mm, the water seepage rate of the second grouting material is not more than 3%, and the initial setting time of the second grouting material is 1.5h~3h.

2. A grouting reinforcement method for karst foundation treatment and protection according to claim 1, characterized in that: The karst foundation is located in the soluble gypsum stratum, which is the mirabilite-gypsum stratum.

3. A grouting reinforcement method for karst foundation treatment and protection according to claim 1, characterized in that: When underground pressurized water gushes out of the grouting holes, the correlation between the grouting holes and the adjacent grouting holes is judged as obvious connection between the dissolution holes; when there is no obvious groundwater gushing out of the grouting holes, the pigment method, salt method, temperature and resistivity method are used to judge the correlation between the grouting holes and the adjacent grouting holes as obvious connection between the dissolution holes or insignificant connection between the dissolution holes.

4. A grouting reinforcement method for karst foundation treatment and protection according to any one of claims 1 to 3, characterized in that: In S3, the sac-type grout plug closed grouting method is adopted for grouting reinforcement. The specific steps are as follows: A waterproof plate is arranged on the upper surface of the grouting hole, an orifice pipe is inserted into the grouting hole, and an orifice sealing material is used to fill the space between the grouting hole and the orifice pipe; Connect the slurry inlet pipe and the bladder-type slurry stopper in sequence, and place the slurry inlet pipe and the bladder-type slurry stopper into the grouting hole; The grouting equipment is turned on, and the slurry of the first grouting material is injected into the sac-type grouting plug through the grouting inlet pipe. After the sac-type grouting plug expands, it is pressed and tightly attached to the inner wall of the grouting hole to form an in-hole grouting system; Continue grouting. When the grouting pressure reaches the end standard pressure, stop grouting, release the pressure of the bladder-type grouting plug, rotate the grouting pipe, and then pull out the grouting pipe and the bladder-type grouting plug.

5. A grouting reinforcement method for karst foundation treatment and protection according to claim 4, characterized in that: During the grouting process, the grouting pressure is selected to be a larger grouting pressure of 1-3MPa.

6. A grouting reinforcement method for karst foundation treatment and protection according to any one of claims 1 to 3, characterized in that: In S3, the hole drainage and slurry circulation grouting method is adopted for grouting reinforcement. The specific steps are as follows: A water-resistant plate is arranged on the upper surface of the grouting hole, an orifice pipe is inserted into the grouting hole, and an orifice sealing material is used to fill the space between the grouting hole and the orifice pipe; a return liquid pipe is arranged at the upper end of the orifice pipe, the return liquid pipe is connected with the orifice pipe, and a return slurry valve is arranged on the return liquid pipe to control the opening and closing of the end of the return liquid pipe away from the orifice pipe; Place the slurry inlet pipe into the orifice pipe, open the slurry return valve to connect the return pipe; start the grouting equipment, pass the slurry of the second grouting material into the grouting hole through the slurry inlet pipe, and control the grouting pressure and speed; the slurry diffuses in the grouting hole to fill the dissolved holes, and close the slurry return valve after the holes are fully filled; Continue grouting. When the grouting pressure reaches the end standard pressure, stop grouting, rotate the slurry inlet pipe, and then pull out the slurry inlet pipe.

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