Construction method for filling prefabricated pipe gallery bottom gap by combined grouting

Abstract

The application discloses a prefabricated pipe gallery bottom gap combined grouting filling construction method and relates to the prefabricated pipe gallery construction technical field. The method comprises the following steps: measuring the bottom gap between the segment bottom surface and the base layer and determining the height distribution of the bottom gap; arranging the grouting pipe with the lower end extending into the gap in the circumferential direction of the segment bottom surface; firstly filling the self-leveling grouting material to 50%-60% of the height of the gap to form a flow leveling layer; and after the initial setting, filling the micro-expansion grouting material to fill the remaining space to form an interface dense body. The application solves the problem that the single grouting material is difficult to consider the flow filling and the volume stability, and has the advantages of filling and compacting, uniformly supporting, inhibiting secondary emptying and water seepage.

Description

Technical Field

[0001] This invention relates to the field of precast pipe gallery construction technology, and in particular to a method for combined grouting and filling construction of the bottom voids of a precast pipe gallery. Background Technology

[0002] As underground corridors for the centralized laying of municipal pipelines, the construction scale of integrated utility tunnels continues to expand. To improve construction quality and efficiency, utility tunnel projects are gradually shifting from on-site monolithic casting to factory prefabrication and on-site assembly. Prefabricated utility tunnel segments are mass-produced in factories according to standard cross-sections and modules. After curing to the design strength, they are transported to the site and hoisted into place section by section using lifting equipment. The bottom surface of the segments is directly supported on the cast-in-place subbase or leveled base layer. After the segments are assembled, the joints and the areas between the segment bottom surface and the base layer are waterproofed and filled to form a complete tunnel structure. Due to the combined effects of factors such as the flatness of the prefabricated segment bottom surface, the elevation deviation of the subbase top surface, the adjustment of the segment installation posture, and hoisting and positioning errors, a thin, unevenly distributed bottom gap often remains between the segment bottom surface and the base layer. If this gap is not properly treated, it will become a hidden danger affecting the overall load-bearing performance of the utility tunnel.

[0003] In current engineering practice, the treatment of the bottom gaps in precast pipe galleries mainly follows two conventional methods. One method involves laying a cement mortar bedding layer on the top surface of the foundation before the segments are hoisted into place, relying on the weight of the segments to compact and spread the bedding material, forming the bottom support. The other method involves injecting a single type of cement grout or cement mortar into the bottom gaps through pre-drilled holes on the top surface of the segments or from both sides of the segments until grout emerges from the pre-drilled outlet holes, at which point the grouting is considered complete. To ensure that the grout can fully diffuse within the thin layer of gaps only tens of millimeters thick, it is usually necessary to increase the amount of water used in the grout to improve its fluidity, or to continuously pump it at high pressure, forcing the grout to move forward along the gap channels.

[0004] The aforementioned conventional practices present several technical contradictions. The grouting layer, limited by the segment's own weight and compaction level, struggles to achieve consistent compaction when there are local height differences or slopes on the top surface of the subbase. The resulting voids after segment placement cannot be compensated for. Single-material grouting faces an inherent conflict between fluidity and volume stability: increasing water usage or pump pressure allows the grout to diffuse over long distances within thin voids, but the hardening process is accompanied by significant plastic and drying shrinkage. Within narrow voids, the grout shrinks and detaches from the segment's bottom surface, creating secondary voids and leaving seepage channels. Conversely, using a low-fluidity, thick grout hinders diffusion over long distances and within thin voids, resulting in insufficient grout at the corners and far ends. Meanwhile, the one-time full-filling method lacks quantitative control over the height distribution of the voids, and the end of the grouting is judged only by the phenomenon of grout overflow. The grout is prone to disorderly flow along the undulating channels of the voids, forming air pockets or interlayers in some areas. The high grouting pressure may also lift the segments, disturbing the already assembled gallery structure. The problem of inadequate and uneven bottom support has been a long-standing issue, directly weakening the uniform load transfer capacity of the bottom of the utility tunnel structure. Summary of the Invention

[0005] The main objective of this invention is to propose a combined grouting filling method for the bottom voids of precast pipe gallery, which aims to fill the voids at the bottom of the precast pipe gallery segments densely and uniformly, eliminate secondary voids and seepage channels after grouting, and improve the overall support performance of the bottom of the precast pipe gallery.

[0006] To achieve the above objectives, the present invention proposes a precast pipe gallery bottom void combination grouting filling construction method, applicable to precast pipe gallery segments with reserved grouting interfaces on the bottom surface. After the precast pipe gallery segment is installed in place, a bottom void is formed between its bottom surface and the base layer. The precast pipe gallery bottom void combination grouting filling construction method includes: The bottom gap is measured to determine its maximum height, average height, and distribution range along the longitudinal direction of the pipe gallery; Based on the height distribution of the bottom gap, grouting pipes are arranged circumferentially at intervals on the bottom surface of the precast pipe gallery segment. The upper end of the grouting pipe is connected to the reserved grouting interface, and the lower end of the grouting pipe extends into the bottom gap. Grouting material is injected into the bottom void in stages through the grouting pipe. First, self-leveling grouting material is used for the first stage of grouting. The grouting height of the first stage is 50% to 60% of the height of the bottom void, forming a fluid leveling layer. After the grout injected in the first stage has initially set, a second stage of injection is carried out with micro-expansion grout to fill the remaining space of the bottom void and form a dense interface. After the second stage of grouting is completed, pressure is maintained, the grouting interface is sealed, and drainage blind ditches or drain holes are set.

[0007] In one embodiment, the step of measuring the bottom gap includes: A row of measuring points is arranged every 500mm to 1000mm along the longitudinal direction of the prefabricated pipe gallery segment, with at least 3 measuring points arranged in each row. The height of the bottom gap is measured at the measuring points using a feeler gauge. Record the measured values ​​of the gap height at each measuring point and plot the gap height distribution curve along the longitudinal direction of the pipe gallery; The maximum height, the average height, and the distribution range of the bottom gap are determined based on the gap height distribution curve.

[0008] In one embodiment, the precast pipe gallery bottom void grouting filling construction method further includes: The grouting height of the first stage is determined based on the ratio of the maximum height to the average height; when the ratio of the maximum height to the average height is larger, the proportion of the grouting height of the first stage to the bottom void height is smaller, so as to reserve volume compensation space for the micro-expansion grouting material of the second stage. The amount of micro-expansion grout to be injected is determined based on the volume of the bottom void and the injection height of the first stage injection.

[0009] In one embodiment, the step of arranging grouting pipes at circumferential intervals on the bottom surface of the precast pipe gallery segment according to the height distribution of the bottom void includes: One grouting pipe is arranged every 1.0m to 2.0m along the perimeter of the bottom surface of the precast pipe gallery segment, and one grouting pipe is arranged every 1.5m to 2.5m in the middle of the bottom surface of the precast pipe gallery segment. The grouting pipe is a steel pipe or a rigid plastic pipe. The upper end of the grouting pipe is connected to the reserved grouting interface through a threaded joint or a quick joint. The lower end of the grouting pipe is a beveled cut or a perforated pipe and is 30mm to 50mm away from the top surface of the base layer. The bottom surface of the precast pipe gallery segment is provided with a guide channel or guide slope, and the direction of the guide channel or guide slope is towards the position of the grouting pipe; the depth of the guide channel is 10mm to 20mm, the width is 30mm to 50mm, and the slope of the guide slope is 1% to 2%.

[0010] In one embodiment, a valve and a pressure gauge are installed at the upper end of the grouting pipe, the valve and pressure gauge being used to control the injection flow rate and injection pressure of the grouting material.

[0011] In one embodiment, the step of first-stage grouting with self-leveling grout includes: Starting from the lowest point of the bottom void, select the grouting pipe located at the lowest point as the starting grouting pipe, and pump the self-leveling grouting material with an injection pressure of 0.2MPa~0.4MPa; Observe whether there is grout overflow from adjacent grouting pipes. When grout overflows from adjacent grouting pipes, stop grouting through the starting grouting pipe and record the volume of grout that has been injected to form a fluid leveling layer.

[0012] In one embodiment, the self-leveling grout is a cement-based self-leveling grout with a slump spread of 600mm to 700mm, a 3-day compressive strength of not less than 30MPa, and a 28-day compressive strength of not less than 60MPa.

[0013] In one embodiment, the step of performing a second stage of grouting with micro-expansion grout includes: After the self-leveling grout injected in the first stage has initially set for 4 to 8 hours and its surface has lost its flowability, the micro-expansion grout is injected sequentially from one end of the bottom void to the other through each of the grouting pipes at an injection pressure of 0.3 MPa to 0.5 MPa. During the grouting process, the elevation of the observation points preset on the top surface of the precast pipe gallery segment is checked to monitor the jacking amount of the precast pipe gallery segment. If the jacking amount exceeds 2mm, the injection pressure is reduced or the grouting is suspended.

[0014] In one embodiment, the micro-expansion grout is sulfoaluminate micro-expansion grout or UEA micro-expansion grout, with an expansion rate of 0.1% to 0.3%, a flowability of 250 mm to 300 mm, and an expansion stabilization period of not less than 14 days; After the second stage of grouting is completed, the pressure of the grouting material in the grouting pipe is maintained at 0.1MPa~0.2MPa, and the pressure holding time is 30min~60min, so that the micro-expansion grouting material can fully fill the micro gaps in the bottom void under pressure. After the pressure holding period ends, close the valves of each of the grouting pipes. After the micro-expansion grouting material has set, cut off the ends of the grouting pipes that extend out of the bottom surface of the precast pipe gallery segment, and seal the grouting interface with a sealing material of the same material as the precast pipe gallery segment.

[0015] In one embodiment, prior to the staged injection of grout, the method further includes: The top surface of the base layer within the bottom void is cleaned and moistened to remove laitance, gravel, and accumulated water, so that the moisture content of the top surface of the base layer reaches a saturated surface-dry state. A layer of interface treatment agent is applied to the top surface of the substrate. The interface treatment agent is either a cement-based interface treatment agent or an epoxy resin interface agent, and the application rate of the interface treatment agent is 0.3 kg / m².2 ~0.5kg / m 2 .

[0016] The technical solution of this invention first measures and determines the maximum height, average height and distribution range of the bottom voids, and then arranges the grouting pipes accordingly and performs grouting in two stages. First, self-leveling grout is injected to 50% to 60% of the void height to form a fluid leveling layer. After it initially sets, micro-expansion grout is used to fill the remaining space to form a dense interface. The two functions of fluid leveling and volume compensation compaction are decomposed into two sequential grouting stages, which solves the problem that single grout injection cannot simultaneously take into account fluid filling and volume stability. It has the advantages of dense filling, uniform support, and suppression of secondary voids and water seepage. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of an embodiment of the prefabricated pipe gallery bottom void combination grouting construction method provided by the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] To solve the above-mentioned technical problems, the present invention proposes a construction method for combined grouting filling of the bottom gap of a precast pipe gallery, which is applied to a precast pipe gallery segment with a reserved grouting interface on the bottom surface. After the precast pipe gallery segment is installed in place, a bottom gap is formed between its bottom surface and the base layer.

[0024] Please see Figure 1 In one embodiment of the present invention, the method for grouting and filling the gaps at the bottom of the precast pipe gallery includes: S10, Measure the bottom gap to determine the maximum height, average height and distribution range of the bottom gap along the longitudinal direction of the pipe gallery; S20, according to the height distribution of the bottom gap, grouting pipes are arranged circumferentially on the bottom surface of the precast pipe gallery segment, the upper end of the grouting pipe is connected to the reserved grouting interface, and the lower end of the grouting pipe extends into the bottom gap; S30, clean and moisten the top surface of the base layer in the bottom gap, and apply an interface treatment agent to the top surface of the base layer; S40, self-leveling grout is first injected into the bottom void through the grouting pipe in the first stage. The injection height of the first stage is 50% to 60% of the height of the bottom void, forming a fluid leveling layer. S50, after the grout injected in the first stage has initially set, the second stage of injection is carried out with micro-expansion grout to fill the remaining space of the bottom void and form a dense interface. S60, after the second stage of grouting is completed, maintain pressure, seal the grouting interface and set up drainage blind trenches or drain holes.

[0025] For ease of understanding, the following explains some key terms in this embodiment: Bottom voids refer to the thin, unevenly distributed void areas between the bottom surface of a prefabricated pipe gallery segment and the top surface of the base layer, formed by factors such as the flatness of the bottom surface, the elevation deviation of the subbase, and the installation posture.

[0026] The fluid leveling layer refers to the grout layer formed by the self-leveling grout injected in the first stage, which flattens itself in the bottom voids due to its own fluidity. Its function is to establish a continuous flow and support interface before the second stage of grouting.

[0027] The interface dense body refers to the dense filling body formed after the micro-expansion grout injected in the second stage fills the remaining space of the bottom void and undergoes constrained micro-expansion. Its expansion deformation is constrained by the segment's self-weight and the hardened fluid leveling layer, which is transformed into a compaction effect on the contact interface.

[0028] Initial setting refers to the state in which the grout changes from a flowable state to a state where it loses its plasticity and begins to build structural strength but has not yet reached final setting. This invention uses initial setting as the process transition node between the first stage of grouting and the second stage of grouting.

[0029] The saturated surface dry state refers to the state in which the surface water of the base layer is removed but the internal pores remain water-saturated. This state avoids both the dilution of the slurry by surface water and the absorption of moisture from the slurry by the dry base layer, which would affect the fluidity of the slurry and the interfacial adhesion.

[0030] This embodiment provides a construction method for combined grouting to fill the voids at the bottom of a precast pipe gallery.

[0031] First, the method includes measuring the bottom void to determine the maximum height, average height, and distribution range of the bottom void along the longitudinal direction of the utility tunnel.

[0032] Specifically, construction workers can select several cross-sections along the longitudinal direction of the pipe gallery at the gap between the bottom surface of the segment and the base layer, and use a feeler gauge to measure and record the gap height point by point, thereby obtaining the variation of the gap height along the longitudinal direction. As an alternative approach, the gap height can be measured only at the two ends of the segment and at the significantly deeper parts of the gap, and the distribution range of the gap height can be estimated by combining the elevation difference between the bottom surface of the segment and the top surface of the base layer.

[0033] Furthermore, based on the height distribution of the bottom voids, grouting pipes are arranged at intervals around the bottom surface of the precast pipe gallery segment, with the upper end of each grouting pipe connected to the reserved grouting interface and the lower end extending into the bottom void. For example, a ring of grouting pipes can be evenly arranged around the bottom surface of the segment, with additional grouting pipes arranged in the center of the bottom surface. Alternatively, based on the void height distribution curve, the number of grouting pipes can be increased in sections with thicker voids and decreased in sections with thinner voids or where the bottom surface is in contact with the base layer.

[0034] Subsequently, grout is injected into the bottom void in stages through the grouting pipe. The first stage of grouting is performed with self-leveling grout, and the grouting height of the first stage is 50% to 60% of the height of the bottom void, forming a fluid leveling layer.

[0035] Specifically, a high-flowability self-leveling grout can be prepared by a mixing plant and pumped into the grouting pipe at a low pressure from the lower part of the void. The grout will flatten itself under its own weight, fill the lower part of the void and adhere to the bottom surface of the segment. The grouting will stop after reaching the preset height.

[0036] Based on this, after the grout injected in the first stage has initially set, a second stage of injection is carried out with micro-expansion grout to fill the remaining space in the bottom voids and form a dense interfacial substance. For example, depending on the ambient temperature and the setting of the grout, initial setting can be determined 4 to 8 hours after injection, and then the second stage of injection can begin.

[0037] As another approach, an observation port can be left after the first stage of grouting is completed, and the loss of flowability of the grout surface can be used as the criterion for starting the second stage of grouting.

[0038] This construction method first measures and determines the height distribution of the bottom voids, then arranges the grouting pipes accordingly and performs grouting in two stages. This decomposes the functions of flow leveling and volume compensation compaction into sequential grouting stages, avoiding secondary voids and incomplete filling caused by a single full-filling of grout. Simultaneously, this method reserves 50%–60% of the grouting height for volume compensation in the second stage, using initial setting as the stage transition node, transforming the expansion deformation of the micro-expansion grout into a compacting effect on the interface. Furthermore, through orderly grouting starting from a low point and advancing from one end to the other, along with controlled jacking, the method achieves dense and uniform molding of the filler, preventing segment misalignment and reducing construction risks associated with bottom voids in the precast pipe gallery.

[0039] In an embodiment of the present invention, the step of measuring the bottom gap includes: S11. A row of measuring points is arranged every 500mm to 1000mm along the longitudinal direction of the prefabricated pipe gallery segment, with at least 3 measuring points arranged in each row. The height of the bottom gap is measured at the measuring points using a feeler gauge. S12, record the measured values ​​of the gap height at each measuring point and draw the gap height distribution curve along the longitudinal direction of the pipe gallery; S13, determine the maximum height, the average height, and the distribution range of the bottom gap based on the gap height distribution curve.

[0040] Specifically, a feeler gauge is a measuring tool made of multiple thin steel sheets of varying thicknesses stacked together. During measurement, the feeler gauge is inserted into the bottom gap along the edge of the segment's bottom surface until it simultaneously contacts both the bottom surface of the segment and the top surface of the base layer. The thickness read by the feeler gauge at this point is the gap height at that measuring point. Arranging a row of measuring points every 500mm to 1000mm along the longitudinal direction of the pipe gallery can capture the longitudinal variations in gap height. If the spacing is less than 500mm, the measuring points are too dense, resulting in excessive measurement workload; if the spacing is greater than 1000mm, local abrupt changes in gap height may be missed.

[0041] Meanwhile, at least three measuring points are arranged in each row to simultaneously reflect the height differences between the left and right sides and the middle of the bottom surface of the segment at the same longitudinal station number, avoiding the use of single-point measurements to represent the void status of the entire cross-section. By recording the measurements of each measuring point sequentially according to the longitudinal station number and connecting them, the void height distribution curve along the longitudinal direction of the pipe gallery can be obtained, thereby determining the maximum height, average height, and distribution range of the void.

[0042] It should be noted that when a local area on the bottom surface of a segment is too tightly fitted to the top surface of the base layer, and a feeler gauge cannot be inserted, the gap height at that measuring point can be recorded as zero and included in the average calculation of the gap height; in this case, the fitted area does not need to be filled, and the measurement result truly reflects the distribution range of the gap.

[0043] In addition, measurement work can also be carried out by inserting a wedge gauge through the grouting interface reserved on the bottom surface of the segment, as an equivalent substitute for feeler gauge measurement.

[0044] In an embodiment of the present invention, the step of measuring the bottom gap further includes: S14, determine the grouting height of the first stage of grouting based on the ratio of the maximum height to the average height; when the ratio of the maximum height to the average height is larger, the proportion of the grouting height of the first stage of grouting to the bottom void height is smaller, so as to reserve volume compensation space for the micro-expansion grouting material of the second stage of grouting. S15, and determine the amount of micro-expansion grout to be injected based on the volume of the bottom void and the injection height of the first stage injection.

[0045] Specifically, the ratio of the maximum height to the average height characterizes the severity of the void height fluctuations. A larger ratio indicates more severe void height fluctuations, requiring more volume compensation space for the micro-expansion grout injected in the second stage, and correspondingly reducing the proportion of the first stage injection height to the bottom void height. Conversely, a ratio closer to 1 indicates a more uniform void height, allowing for a more appropriate increase in the first stage injection height. Based on this, the injection volume of the micro-expansion grout is determined according to the volume of the bottom voids and the injection height of the first stage, ensuring that the amount of both grouts matches the actual void shape.

[0046] Through the above technical solution, this application first establishes a quantitative distribution model of the bottom voids before grouting, and uses three parameters—maximum height, average height, and distribution range—to characterize the fluctuation characteristics of the voids. It also quantitatively links the grouting height, grout dosage, and void morphology, so that subsequent grouting parameters are determined based on measured distribution. This eliminates the blindness of the conventional practice of judging the grouting endpoint solely based on the grout overflow phenomenon, and provides a basis for the quantitative design of combined grouting.

[0047] In an embodiment of the present invention, the step of arranging grouting pipes at circumferential intervals on the bottom surface of the precast pipe gallery segment according to the height distribution of the bottom void includes: S21, a grouting pipe is arranged at intervals of 1.0m to 2.0m along the periphery of the bottom surface of the precast pipe gallery segment, and a grouting pipe is arranged at intervals of 1.5m to 2.5m in the middle of the bottom surface of the precast pipe gallery segment; S22, the grouting pipe is a steel pipe or a rigid plastic pipe, the upper end of the grouting pipe is connected to the reserved grouting interface through a threaded joint or a quick joint, and the lower end of the grouting pipe is a beveled cut or a perforated pipe, and is 30mm to 50mm away from the top surface of the base layer; S23, wherein the bottom surface of the precast pipe gallery segment is provided with a guide groove or guide slope, and the direction of the guide groove or guide slope is towards the position of the grouting pipe.

[0048] Specifically, the differentiated spacing between the periphery and center of the grouting pipe is adapted to the diffusion radius of the grout within the thin voids: the periphery voids are thinner and the flow channels are narrower, resulting in greater grout diffusion resistance and a smaller diffusion radius, hence the closer spacing; the center voids are relatively thicker and the diffusion conditions are better, so the spacing can be appropriately widened. The grouting pipes are made of steel or rigid plastic, which can maintain the pipe's rigidity under injection pressure without being crushed or pushed out.

[0049] Meanwhile, the lower end of the grouting pipe is 30mm to 50mm away from the top surface of the base layer. This avoids the pipe opening directly pressing against the top surface of the base layer and being blocked, while also ensuring that the grout flows out of the pipe opening and preferentially enters the lower part of the voids, filling the voids from bottom to top. The oblique cut or perforated pipe increases the equivalent opening area of ​​the grout outlet and directs the grout to flow out in a directional manner along the cut, reducing the grout discharge resistance and facilitating the flow and diffusion of the grout within the voids.

[0050] Based on this, the guide channel or guide slope can be integrally formed on the bottom surface of the segment during segment prefabrication, with its direction pointing towards the position of the grouting pipe, providing a continuous low-resistance channel for the directional flow of grout; the depth of the guide channel is 10mm to 20mm and the width is 30mm to 50mm, and the slope of the guide slope is 1% to 2%, so that the grout flows along the preset direction to the vicinity of the grouting pipe under its own weight and pressure, avoiding the grout from stagnating in local depressions on the bottom surface of the segment.

[0051] It should be noted that the prefabricated pipe gallery segments referred to in this invention include various prefabricated components such as straight segments, curved segments, and special joint segments of integrated pipe galleries. The grouting interfaces reserved on the bottom surface can be pre-embedded during the segment prefabrication process, or they can be formed by drilling holes on-site according to the bottom gap distribution after the segment is installed in place.

[0052] In an embodiment of the present invention, the step of arranging grouting pipes at circumferential intervals on the bottom surface of the precast pipe gallery segment according to the height distribution of the bottom void further includes: S24, A valve and a pressure gauge are installed at the upper end of the grouting pipe. The valve and pressure gauge are used to control the injection flow rate and injection pressure of the grouting material.

[0053] Specifically, valves and pressure gauges are installed at the upper end of the grouting pipes, allowing each pipe to open and close independently and reflect the pressure inside, thus enabling independent control of the injection flow rate and pressure of each pipe. During grouting, the flow rate can be adjusted by the valve opening, and the position of the grout front and the flow resistance can be determined by the pressure gauge reading, providing a controllable process interface for subsequent phased and regional orderly grouting.

[0054] Through the above technical solution, this application implements differentiated pipe layout at the periphery and center of the bottom surface according to the height distribution of the voids. The pipe opening is suspended at a distance of 30mm to 50mm from the top surface of the base layer and is combined with oblique cuts or perforated pipes to allow the grout to be stably injected from the bottom of the voids and evenly diffused. The guide channel or guide slope, in conjunction with valves and pressure gauges, makes the flow direction of the grout, the injection flow rate, and the injection pressure controllable, providing an injection channel system that matches the void morphology for staged combined grouting.

[0055] In an embodiment of the present invention, before the staged injection of grouting material, the precast pipe gallery bottom void combination grouting filling construction method further includes: S31, clean and moisten the top surface of the base layer in the bottom void to remove laitance, gravel and water, so that the moisture content of the top surface of the base layer reaches a saturated surface-dry state. S32, apply a layer of interface treatment agent to the top surface of the base layer. The interface treatment agent is a cement-based interface treatment agent or an epoxy resin interface agent, and the application rate of the interface treatment agent is 0.3 kg / m². 2 ~0.5kg / m 2 .

[0056] Specifically, cleaning can be carried out using a combination of wire brush cleaning and sweeping to remove residual laitance, gravel, and standing water from the top surface of the base layer. Wetting treatment aims to achieve a slightly damp but not waterlogged surface, ensuring the base layer is saturated and surface-dry. This saturated surface-dry state prevents standing water from diluting the grout and reducing its hardened strength, and also prevents the dry base layer from rapidly absorbing moisture from the grout, which would weaken the grout's fluidity within the thin pores.

[0057] Simultaneously, the interface treatment agent forms a continuous bonding transition layer on the top surface of the substrate, ensuring a reliable interfacial bond between the subsequently injected grout and the substrate, and reducing the substrate's absorption rate of grout moisture, thereby improving the bonding quality between the grout and the substrate. The application rate should be controlled at 0.3 kg / m². 2 ~0.5kg / m 2 If the amount of grout applied is too small, it will be difficult to form a continuous and complete transition layer. If the amount of grout applied is too large, the interface agent will accumulate at the bottom of the gaps, which may hinder the direct contact between the grout and the base layer.

[0058] It should be noted that cleaning and wetting can be performed before or after the measurement steps; if performed before measurement, care should be taken to ensure that the cleaning work does not change the original height of the voids to guarantee that the measurement results are consistent with the state during grouting. For areas with groundwater seepage, temporary drainage measures can be set up first to lower the water head before wetting and interface treatment are implemented.

[0059] Through the above technical solution, this application completes the cleaning, wetting and interface treatment of the top surface of the base layer before grouting, which creates interface conditions for the full diffusion of the fluid leveling layer in the thin layer voids and reliable bonding with the base layer, reducing the hidden dangers of grout segregation and interface debonding.

[0060] In an embodiment of the present invention, the step of first-stage grouting with self-leveling grout includes: S41, Starting from the lowest position of the bottom void, select the grouting pipe located at the lowest position as the starting grouting pipe, and pump the self-leveling grouting material with an injection pressure of 0.2MPa~0.4MPa; S42, observe whether there is grout overflow from adjacent grouting pipes. When grout overflows from adjacent grouting pipes, stop grouting through the starting grouting pipe and record the volume of grout that has been injected to form a fluid leveling layer.

[0061] Specifically, grouting begins at the lowest point of the bottom voids, ensuring the grout continuously ascends along the void's upward path. The grout's weight and pump pressure work in the same direction, causing air within the voids to be systematically expelled through adjacent grouting pipes by the grout vane, preventing cavitation at higher points. Pumping at a relatively low pressure of 0.2MPa to 0.4MPa is sufficient to overcome the flow resistance of the thin void layer without causing segmental lifting.

[0062] Simultaneously, overflow from adjacent grouting pipes indicates that the grout front has advanced to that pipe's position, meaning the grout within the grouting range controlled by the initial grouting pipe is already filled. At this point, shifting the grouting position prevents localized over-grouting and disorderly grout flow. The recorded grouting volume and void distribution curves corroborate each other, used to verify the actual forming state of the flow leveling layer, ensuring that the first stage of grouting stops after reaching 50%–60% of the bottom void height, reserving space for volume compensation in the second stage.

[0063] It should be noted that when the thickness of the bottom void is too small and the grout advance is slow, the pumping pressure can be appropriately increased, but should not exceed 0.4MPa, so as to avoid the segment being lifted. When there is no grout overflow from the adjacent grouting pipe for a long time, the grouting should be suspended and the grout should be observed to see if it overflows and flows out along the edge of the void.

[0064] In an embodiment of the present invention, the self-leveling grout is a cement-based self-leveling grout with a slump spread of 600 mm to 700 mm, a 3-day compressive strength of not less than 30 MPa, and a 28-day compressive strength of not less than 60 MPa.

[0065] Specifically, when the slump spread is between 600 mm and 700 mm, the grout can self-level within the thin voids and adhere to the bottom surface of the segment under its own weight, without relying on long-distance pushing by a high-pressure pump. When the slump spread is less than 600 mm, the grout's self-leveling ability is insufficient, and it is prone to stagnation at undulating voids. When it is greater than 700 mm, the grout is prone to segregation and bleeding, and shrinkage increases after hardening. The 3-day compressive strength is not less than 30 MPa, and the 28-day compressive strength is not less than 60 MPa, ensuring that the fluid leveling layer forms a reliable load-bearing and force-transfer interface in a short time, and providing a stable working surface for the second stage of grouting.

[0066] Based on this, if the measured expansion of the mixing plant is lower than the lower limit, the amount of mixing water or admixture can be adjusted on-site to restore the slurry to a self-leveling state before grouting.

[0067] Through the above technical solution, this application utilizes the flow characteristics of self-leveling grout to complete the leveling and filling of the lower 50% to 60% height range of the void. The flow leveling layer extensively adheres to the bottom surface of the segment, eliminating the undulating dead corners at the bottom of the void. At the same time, it reserves a compensation space of 40% to 50% of the void height for the second-stage micro-expansion grout, enabling volume compensation and compaction to be carried out under constrained conditions, which is a process condition that conventional one-time full grouting does not have.

[0068] In an embodiment of the present invention, the step of performing a second stage of grouting with micro-expansion grout includes: S51, after the self-leveling grout injected in the first stage has initially set for 4h to 8h and its surface has lost its flowability, the micro-expansion grout is injected sequentially from one end of the bottom void to the other through each of the grouting pipes, with an injection pressure of 0.3 MPa to 0.5 MPa. S52. During the grouting process, the elevation of the observation points preset on the top surface of the precast pipe gallery segment is checked to monitor the jacking amount of the precast pipe gallery segment. If the jacking amount exceeds 2mm, the injection pressure is reduced or the grouting is suspended.

[0069] Specifically, the initial setting is used as the stage transition node: after the initial setting of the first stage slurry, it loses its fluidity and forms a skeleton. When the second stage slurry is pushed on it, it will not mix the two again. The two stages of slurry form a composite filler with distinct layers and complementary functions. The fluid leveling layer after initial setting also provides a smooth flow interface for the second stage grouting. The resistance of the slurry spreading along this interface is significantly less than the resistance of spreading along the top surface of the rough base layer.

[0070] At the same time, the grout is injected sequentially from one end to the other, so that the second-stage grout always fills the remaining space in a way that advances along the entire cross section, continuously pushing the residual air to the end grouting pipe for discharge, thus avoiding the formation of closed air cavities due to multiple simultaneous injections in the middle of the gap.

[0071] Based on this, the expansion deformation of the micro-expansion grout during the hardening process is constrained by the self-weight of the segment and the hardened fluid leveling layer. The expansion potential energy is converted into a pressing effect on the bottom surface of the segment and the interface of the leveling layer, which compensates for the plastic shrinkage and drying shrinkage of the grout in the first stage, seals the micro gaps at the interface, and makes the filler and the bottom surface of the segment form a dense interface, thereby eliminating secondary voids and seepage channels.

[0072] It should be noted that the jacking amount verification is carried out by setting up observation points on the top surface of the segment and using leveling measurement. The segment attitude change can be monitored in real time without the need to deploy electrified monitoring elements. If the jacking amount exceeds 2mm, it indicates that the lifting effect of expansion and pressure on the segment has exceeded the allowable range. At this time, reducing the injection pressure or paving can prevent the segment from being lifted and misaligned while maintaining the interface compactness.

[0073] Through the above technical solution, this application uses initial setting as the process transition node, so that the two stages of fluid leveling and volume compensation compaction are connected and the layers are distinct; the micro-expansion grout undergoes restricted expansion under the dual constraints of the segment's self-weight and the leveling layer, transforming the expansion deformation into a pressing effect on the interface, which not only compensates for the shrinkage of the grout in the first stage, but also seals the micro gaps at the interface, forming a dense, continuous interface solid in the bottom voids that is in close contact with the bottom surface of the segment, fundamentally eliminating the conditions for secondary voids and seepage channels after grouting.

[0074] In an embodiment of the present invention, the micro-expansion grout is a sulfoaluminate micro-expansion grout or a UEA micro-expansion grout, with an expansion rate of 0.1% to 0.3%, a flowability of 250 mm to 300 mm, and an expansion stabilization period of not less than 14 days.

[0075] Specifically, when the expansion rate is below 0.1%, volume compensation is insufficient, and the slurry may still detach from the bottom surface of the segment after hardening; when it is above 0.3%, the interfacial stress generated by the restricted expansion is too large, which may lift the segment. When the fluidity is in the range of 250mm to 300mm, the slurry maintains the necessary pumpability and has sufficient consistency to maintain its shape after grouting. The expansion stabilization period is no less than 14 days to ensure that the expansion compensation effect continues to play during the slurry hardening and shrinkage period, avoiding the recurrence of voids due to the time misalignment of shrinkage and expansion effects.

[0076] In an embodiment of the present invention, after the second stage of grouting is completed, the precast pipe gallery bottom void combination grouting filling construction method further includes: S61, maintain the grouting material pressure in the grouting pipe at 0.1MPa~0.2MPa, and hold the pressure for 30min~60min, so that the micro-expansion grouting material can fully fill the micro gaps in the bottom void under pressure; S62, after the pressure holding is completed, close the valves of each of the grouting pipes. After the micro-expansion grouting material has finally set, cut off the end of the grouting pipe that extends out of the bottom surface of the precast pipe gallery segment, and seal the grouting interface with a sealing material of the same material as the precast pipe gallery segment. S63, a drainage ditch or drain hole is provided around the junction of the bottom surface of the precast pipe gallery segment and the base layer. The drainage ditch is filled with graded crushed stone or blind pipe to drain groundwater that may seep into the bottom void.

[0077] Specifically, during the pressure holding stage, the slurry pressure maintained in the pipeline is used to continuously press the still fluid micro-expansion slurry into the fine gaps within the voids, so that it can complete the final filling of the corners under pressure. If the pressure holding time is insufficient, the slurry will flow back and the filled gaps may reopen. If the pressure holding time is too long, the slurry will lose its fluidity and cannot be pressed into the gaps.

[0078] Simultaneously, the end of the grouting pipe is cut off and the joint is sealed to restore the bottom surface of the segment to flatness and block the seepage path at the joint. Drainage blind ditches or drainage holes provide directional discharge channels for groundwater that may seep in along the perimeter of the segment, preventing groundwater from stagnating around the fill and causing uplift or erosion.

[0079] It should be noted that drainage blind ditches can be continuously installed along the perimeter of the junction between the bottom surface of the segment and the base layer, or they can be installed only at both ends of the segment on the side facing the direction of groundwater infiltration; drainage holes can be pre-formed in the lower part of the side wall of the segment, and the outside of the hole opening is protected by a gravel filter layer.

[0080] In addition, after the grout reaches more than 75% of the design strength, the precast pipe gallery segment can be subjected to loading simulation with a loading amount of 1.2 to 1.5 times the design load to test the bearing capacity after the bottom void is filled with grout. If there is no abnormal deformation of the bottom void filler and no significant change in the segment posture during the loading process, it indicates that the combined grout filler has formed a cooperative force-bearing system with the segment.

[0081] Through the above technical solution, this application uses pressure to allow the micro-expansion grout to complete the final filling of the micro gaps under pressure, restores the flatness of the bottom surface of the segment by cutting off the pipe end and sealing the interface and blocks the seepage path, and provides a directional discharge channel for groundwater that may seep in through drainage blind ditches or drainage holes. This forms a complete finishing process of "internal compaction, interface closure and external drainage", which ensures the stability and durability of the combined grouting filler under long-term operating conditions.

[0082] The following example will provide a more detailed explanation of the above technical solution: In a certain city's underground integrated utility tunnel project, the prefabricated tunnel segments were 3.0m long and 3.5m wide. There were longitudinally undulating gaps between the bottom surface of the segments and the top surface of the foundation layer. The engineering team faced the challenge of insufficient bottom support and easy leakage after grouting. To solve these problems, the construction team adopted this method.

[0083] First, a row of measuring points with 5 measuring points is arranged every 800 mm along the longitudinal direction of the segment. The gap height of each measuring point is measured using a feeler gauge. The gap height distribution curve along the longitudinal direction of the pipe gallery is recorded and plotted. The maximum height is determined to be 22 mm, the average height is 13 mm, and the distribution range is about 21 m along the longitudinal direction. The ratio of the maximum height to the average height is 1.69. Based on this, the grouting height of the first stage is determined to be 55% of the bottom gap height.

[0084] Secondly, clean and moisten the top surface of the base layer until it is saturated and dry, and apply 0.4 kg / m² of cement-based interface treatment agent; grouting pipes are arranged every 1.5 m around the perimeter of the bottom surface and every 2.0 m in the middle of the bottom surface. The lower end of the grouting pipe is 40 mm away from the top surface of the base layer, with a beveled pipe opening, and a valve and pressure gauge are installed at the upper end.

[0085] Next, the first stage of grouting was carried out using cement-based self-leveling grout with a slump expansion of 650 mm. The grout was pumped from the lowest point of the voids at a pressure of 0.3 MPa. After grout overflowed from adjacent grouting pipes, the grouting position was changed, and the grouting was stopped when the grouting height reached 55% of the void height, forming a fluid leveling layer. Eight hours after grouting, the surface of the leveling layer lost its flowable state, reaching initial setting.

[0086] Then, the second stage of grouting was carried out using UEA micro-expansion grout with an expansion rate of 0.2% and a flowability of 280 mm. The grout was injected sequentially from one end of the void to the other at a pressure of 0.4 MPa. During the grouting process, the leveling elevation of the observation points on the top surface of the segment was checked, and the jacking amount never exceeded 1.5 mm. After grouting, the pressure was maintained at 0.15 MPa for 40 minutes, then the valve was closed. After the grout had fully set, the end of the grouting pipe was cut off, and the interface was sealed with the same material. A drainage ditch filled with graded crushed stone was set around the segment. After the grout reached 75% of its design strength, a loading simulation was conducted at 1.3 times the design load. No abnormal deformation of the filling body and no significant change in the segment's posture were observed, indicating that the bottom void had formed a dense and uniform load-bearing filling body.

[0087] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for grouting and filling the bottom void of a precast pipe gallery, applied to precast pipe gallery segments with reserved grouting interfaces on the bottom surface, wherein a bottom void is formed between the bottom surface of the precast pipe gallery segment and the base layer after the segment is installed in place, characterized in that, The construction method for combined grouting and filling the voids at the bottom of the precast pipe gallery includes: The bottom gap is measured to determine its maximum height, average height, and distribution range along the longitudinal direction of the pipe gallery; Based on the height distribution of the bottom gap, grouting pipes are arranged circumferentially at intervals on the bottom surface of the precast pipe gallery segment. The upper end of the grouting pipe is connected to the reserved grouting interface, and the lower end of the grouting pipe extends into the bottom gap. Grouting material is injected into the bottom void in stages through the grouting pipe. First, self-leveling grouting material is used for the first stage of grouting. The grouting height of the first stage is 50% to 60% of the height of the bottom void, forming a fluid leveling layer. After the grout injected in the first stage has initially set, a second stage of injection is carried out with micro-expansion grout to fill the remaining space of the bottom void and form a dense interface. After the second stage of grouting is completed, pressure is maintained, the grouting interface is sealed, and drainage blind ditches or drain holes are set.

2. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 1, characterized in that, The step of measuring the bottom gap includes: A row of measuring points is arranged every 500mm to 1000mm along the longitudinal direction of the prefabricated pipe gallery segment, with at least 3 measuring points arranged in each row. The height of the bottom gap is measured at the measuring points using a feeler gauge. Record the measured values ​​of the gap height at each measuring point and plot the gap height distribution curve along the longitudinal direction of the pipe gallery; The maximum height, the average height, and the distribution range of the bottom gap are determined based on the gap height distribution curve.

3. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 2, characterized in that, The precast pipe gallery bottom void grouting filling construction method also includes: The grouting height of the first stage is determined based on the ratio of the maximum height to the average height; when the ratio of the maximum height to the average height is larger, the proportion of the grouting height of the first stage to the bottom void height is smaller, so as to reserve volume compensation space for the micro-expansion grouting material of the second stage. The amount of micro-expansion grout to be injected is determined based on the volume of the bottom void and the injection height of the first stage injection.

4. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 1, characterized in that, The step of arranging grouting pipes at circumferential intervals on the bottom surface of the precast pipe gallery segment according to the height distribution of the bottom void includes: One grouting pipe is arranged every 1.0m to 2.0m along the perimeter of the bottom surface of the precast pipe gallery segment, and one grouting pipe is arranged every 1.5m to 2.5m in the middle of the bottom surface of the precast pipe gallery segment. The grouting pipe is a steel pipe or a rigid plastic pipe. The upper end of the grouting pipe is connected to the reserved grouting interface through a threaded joint or a quick joint. The lower end of the grouting pipe is a beveled cut or a perforated pipe and is 30mm to 50mm away from the top surface of the base layer. The bottom surface of the precast pipe gallery segment is provided with a guide channel or guide slope, and the direction of the guide channel or guide slope is towards the position of the grouting pipe; the depth of the guide channel is 10mm to 20mm, the width is 30mm to 50mm, and the slope of the guide slope is 1% to 2%.

5. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 4, characterized in that, A valve and a pressure gauge are installed at the upper end of the grouting pipe. The valve and pressure gauge are used to control the injection flow rate and injection pressure of the grouting material.

6. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 4, characterized in that, The first stage of grouting using self-leveling grout includes: Starting from the lowest point of the bottom void, select the grouting pipe located at the lowest point as the starting grouting pipe, and pump the self-leveling grouting material with an injection pressure of 0.2MPa~0.4MPa; Observe whether there is grout overflow from adjacent grouting pipes. When grout overflows from adjacent grouting pipes, stop grouting through the starting grouting pipe and record the volume of grout that has been injected to form a fluid leveling layer.

7. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 6, characterized in that, The self-leveling grout is a cement-based self-leveling grout with a slump spread of 600mm to 700mm, a 3-day compressive strength of not less than 30MPa, and a 28-day compressive strength of not less than 60MPa.

8. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 1, characterized in that, The step of performing a second-stage injection with micro-expansion grout includes: After the self-leveling grout injected in the first stage has initially set for 4 to 8 hours and its surface has lost its flowability, the micro-expansion grout is injected sequentially from one end of the bottom void to the other through each of the grouting pipes at an injection pressure of 0.3 MPa to 0.5 MPa. During the grouting process, the elevation of the observation points preset on the top surface of the precast pipe gallery segment is checked to monitor the jacking amount of the precast pipe gallery segment. If the jacking amount exceeds 2mm, the injection pressure is reduced or the grouting is suspended.

9. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 8, characterized in that, The micro-expansion grout is sulfoaluminate micro-expansion grout or UEA micro-expansion grout, with an expansion rate of 0.1% to 0.3%, a flowability of 250 mm to 300 mm, and an expansion stabilization period of not less than 14 days; After the second stage of grouting is completed, the pressure of the grouting material in the grouting pipe is maintained at 0.1MPa~0.2MPa, and the pressure holding time is 30min~60min, so that the micro-expansion grouting material can fully fill the micro gaps in the bottom void under pressure. After the pressure holding period ends, close the valves of each of the grouting pipes. After the micro-expansion grouting material has set, cut off the ends of the grouting pipes that extend out of the bottom surface of the precast pipe gallery segment, and seal the grouting interface with a sealing material of the same material as the precast pipe gallery segment.

10. The precast pipe gallery bottom void combination grouting filling construction method as described in claim 1, characterized in that, Prior to the staged injection of grouting material, the method further includes: The top surface of the base layer within the bottom void is cleaned and moistened to remove laitance, gravel, and accumulated water, so that the moisture content of the top surface of the base layer reaches a saturated surface-dry state. A layer of interface treatment agent is applied to the top surface of the substrate. The interface treatment agent is either a cement-based interface treatment agent or an epoxy resin interface agent, and the application rate of the interface treatment agent is 0.3 kg / m². 2 ~0.5kg / m 2 .

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