A kind of simulation mud skin and sludge coupling generated cast-in-place pile cementing body forming device
By designing a molding device for the cementitious body of cast-in-place piles that simulates the coupling of mud skin and sediment, the formation process of mud skin and sediment is realistically reproduced, solving the problem of laboratory sample preparation distortion in existing technologies and realizing non-destructive sampling and accurate acquisition of mechanical data.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUQIAN COLLEGE
- Filing Date
- 2026-03-18
- Publication Date
- 2026-07-10
AI Technical Summary
Existing technologies cannot accurately reproduce the formation process of mud cake and sediment, and ignore the differences in groundwater and soil pressure boundaries, resulting in physical distortion of laboratory-prepared specimens and making it impossible to accurately assess the contact failure mechanism of pile foundations.
A molding device for cemented concrete in cast-in-place piles is designed to simulate the coupling of mud skin and sediment. The device uses components such as a reaction frame, a top loading system, a simulated outer cylinder, a transition sealing component, a cementing tank, and a support seat. The device simulates the seepage process of mud slurry under high pressure to achieve the real generation of mud skin and sediment. A split-type sidewall simulation component is used for non-destructive sampling.
It achieves the actual generation of mud skin and sediment, eliminates stress boundary effects, provides non-destructive sampling of the original cemented surface, obtains real mechanical data, and provides reliable support for pile foundation bearing capacity assessment.
Smart Images
Figure CN122361027A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pile foundation engineering and geotechnical physical model testing technology, and in particular to a molding device for simulating the coupling of mud cake and sediment to form a cemented body for cast-in-place piles. Background Technology
[0002] Drilled piles (including rock-socketed piles and friction piles) are a type of deep foundation with strong adaptability and high bearing capacity, and are widely used in high-rise buildings, cross-sea bridges, and various large-scale civil engineering projects. Currently, there is a broad consensus on two major negative effects of mud wall protection technology: first, the "sludge" deposited at the bottom of the borehole significantly reduces the bearing capacity of the pile tip; second, the "mud cake" formed by the mud adhering to the borehole wall surface greatly weakens the lateral frictional resistance at the pile-rock (soil) interface.
[0003] In the actual underwater cast-in-place pile construction process, the interval between the completion of secondary hole cleaning and the start of the first concrete pouring is often several hours due to factors such as the hoisting of the reinforcing cage and on-site scheduling. During this "construction time lag," the multi-field coupling mechanism at the bottom of deep and long pile holes under different geological conditions is fundamentally different: For rock-socketed piles, the surrounding rock of the hole wall is an impermeable boundary, and the mud cake on the sidewall is mainly caused by the static water sedimentation of suspended mud particles, while the bottom of the hole inevitably contains sediment formed by gravity sedimentation; while for friction piles in soil layers, under the high pressure difference of the deep mud column, the mud water will not only undergo strong "radial filtration" to the sidewall soil, causing the formation of a dense mud cake on the hole wall surface, but the soil at the pile tip will also undergo "vertical filtration" seepage, and the sediment at the bottom of the hole is caused by a combination of factors such as hole collapse, incomplete hole cleaning, gravity sedimentation, and seepage consolidation. Subsequently, during the high-pressure fluid concrete pouring stage, the enormous self-weight stress and mud pressure forced the concrete to undergo complex physical compression, water replacement and chemical bonding with the mud cake on the side wall and the loose sediment at the bottom of the hole, ultimately forming special "concrete-mud cake-surrounding rock (or soil)" and "concrete-sediment" multiphase interface cemented bodies on the pile side and pile end, respectively.
[0004] Existing technologies and laboratory tests have the following significant gaps and core deficiencies in simulating and preparing samples for the aforementioned complex working conditions:
[0005] 1. The differences in the formation mechanisms of "mud cake" and "sediment" between rock-socketed piles and friction piles have been severed. Current indoor pile foundation model tests often use a one-size-fits-all equivalent simulation, ignoring the mechanical essence of sedimentation-dominated (rock-socketed piles) and pressure differential seepage-dominated (friction piles). In particular, for friction piles, the radial filtration of mud water and the vertical consolidation at the bottom occur simultaneously. Existing simple atmospheric pressure devices cannot apply the mud column pressure of a real deep-water environment, nor can they simulate the high-pressure seepage filtration process of mud into the soil. This results in the sediment and mud cake prepared in the laboratory having extremely high porosity and appearing as loose flocculation, leading to serious "physical distortion".
[0006] 2. Neglecting the differences in groundwater and soil pressure boundaries and stratum seepage characteristics. The bearing stratum stiffness and permeability vary significantly among different pile types; rock-socketed piles belong to rigid, impermeable water-tight boundaries, while friction piles belong to elasto-plastic, bidirectional permeable boundaries where pore water pressure dissipates. Existing test devices generally use a uniform, closed rigid base plate and sidewalls (or simply pad the base plate with elastic elements such as rubber to replace the soil), making it impossible to fill with reconstituted in-situ soil, let alone connect an external servo system to apply real groundwater and soil pressure. This simplified rigid dead water boundary cuts off the mechanical path of "seepage, consolidation, and embedding" of mud cake and sediment into real pores under soil working conditions, failing to reveal the essential differences in cementation formation under different hydrogeological conditions.
[0007] 3. Existing conventional devices are prone to fluid crossflow and stress transmission distortion when simulating this complex working condition. Due to the lack of an isolation and sealing configuration for high-pressure fluid-structure interaction, when traditional devices introduce high-pressure mud columns for simulation, they often cannot effectively physically isolate the "internal mud pressure" from the "external soil confining pressure / pore water pressure". The high-pressure mud is prone to overflow and short-circuit to the top surface of the soil and the permeable boundary, causing the hydrodynamic boundary of radial seepage skin formation to completely fail. At the same time, the simulated liquid column and the self-weight pressure of the concrete applied at the top are easily distributed by the surrounding non-pile hole areas (such as external seals or the top surface of the surrounding soil), and cannot follow Pascal's law to equally and accurately concentrate and transfer the vertical stress to the bottom sediment and bearing layer, resulting in a serious distortion of the force coupling mechanism at the bottom.
[0008] 4. Lack of in-situ pressure-holding molding and "non-destructive sampling" methods for multiphase interface cementitious materials. After high-pressure concrete pouring and molding, the in-situ cemented "concrete-mud cake-surrounding rock (or soil)" interface is extremely fragile. Existing molding devices are mostly non-removable monolithic cylindrical structures, and after the specimen is molded, it can only be "forced out" by mechanical external force. This generates huge frictional shear forces, which directly damage or even completely peel off the fragile mud cake interface.
[0009] 5. Breakthroughs are urgently needed in indoor testing of the physical and mechanical properties of the multi-interface between the pile side and pile tip. Due to the lack of specialized sample preparation instruments that can distinguish the differences between the soil and rock boundaries and extract the original cemented surface for independent mechanical testing without damage, it is currently difficult to remove semi-cylindrical specimens to conduct large-scale direct shear tests on the "concrete-mud cake-surrounding rock (or soil) cemented body" in the in-situ cemented state. It is also difficult to conduct systematic compression, seepage, and other mechanical tests on the "concrete-sludge cemented body" at the bottom. As a result, key mechanical indicators lack clear data support, making it impossible to accurately assess the actual contact failure mechanism of the pile foundation.
[0010] In summary, there is an urgent need to develop a physical simulation test device that can realistically reproduce the entire process of deep mud skin and sediment coupling under pressure, consider complex groundwater and soil pressure and bidirectional seepage boundaries, and achieve in-situ pressure-holding molding and non-destructive sampling of multi-interface cemented bodies through series segmentation and split structure, so as to carry out subsequent direct shear, compression and seepage tests. Summary of the Invention
[0011] To solve the above-mentioned technical problems, the present invention provides a molding device for cast-in-place pile cementitious bodies that simulates the coupling of mud skin and sediment. It can simulate rock-socketed piles and friction piles, and realistically reproduce the corresponding molding process. The generated mud skin, sediment, and concrete-mud skin-surrounding rock (or soil) and concrete-sediment cementitious bodies are closer to the real state of deep strata and construction conditions.
[0012] The technical solution adopted by this invention to solve its technical problem is: a molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment, including a reaction frame, a top loading system, a simulated outer cylinder, a transition sealing assembly, a cementing tank, and a support seat; the transition sealing assembly includes a transition flange and an annular sealing cover plate located below the transition flange; the top side of the transition flange is connected to the bottom end of the simulated outer cylinder, and the bottom side is connected to the top end of the cementing tank; the bottom side of the cementing tank is connected to the support seat, and the outer edge of the annular sealing cover plate seals the inner wall of the cementing tank; the inner diameter of the simulated outer cylinder, the center hole of the transition flange, and the center hole of the annular sealing cover plate are set to be of equal diameter; a split-type sidewall simulation assembly is installed in the cementing tank, the split-type sidewall simulation assembly being composed of two semi-cylindrical blocks. The device is assembled from two parts and has an internal experimental cavity corresponding to the central hole of the annular sealing cover for filling with experimental media. A water-resistant flexible membrane is also installed inside the bonding tank, dividing the bonding tank into two cavities. A confining pressure cavity is formed between the water-resistant flexible membrane and the bonding tank, used to fill the confining pressure medium, and is connected to an external confining pressure loading system. A filling cavity is formed between the water-resistant flexible membrane and the split-side wall simulation component, used to fill the functional medium. The bottom surface of the annular sealing cover forms the top surface of the confining pressure cavity and the filling cavity, and is sealed to the top edge of the split-side wall simulation component. The top loading system is fixed below the reaction frame top beam, and a sealing pressure cap is fixed to the lower end of the top loading system. The sealing frame cap seals with the inner wall of the simulation outer cylinder and can move vertically in cooperation with it.
[0013] Furthermore, the outer wall of the simulated outer cylinder is provided with several circumferential reinforcing members at intervals along the axial direction; the simulated outer cylinder is also provided with several supporting members for supporting the simulated outer cylinder to stand upright.
[0014] Furthermore, the sidewall simulation component with split sidewalls is equipped with load-bearing collection and drainage pipes on its sidewalls and bottom; the bonding tank has corresponding drainage ports; the load-bearing collection and drainage pipes are fixed to the bonding tank and connected to the drainage ports; the load-bearing collection and drainage pipes are also provided with filter holes that communicate with the experimental chamber and the filling chamber.
[0015] Furthermore, when the simulated friction pile cement body is formed, the experimental cavity is filled with a reshaped simulated soil layer as the experimental medium; a simulated pile hole with the same diameter as the inner diameter of the simulated outer cylinder is opened on the top side of the simulated soil layer, and the simulated pile hole is processed to form a smooth hole wall; the filling cavity is filled with water-collecting and permeable filter material as the functional medium.
[0016] Furthermore, when the simulated rock-socketed pile cement body is formed, the experimental cavity is filled with simulated rock layers as the experimental medium; the simulated rock layers are pre-formed or naturally cut, and the top side of the simulated rock layers has simulated pile holes with the same diameter as the inner diameter of the simulated outer cylinder, and the simulated pile holes are processed to form rough hole walls; the filling cavity is filled with high-rigidity filling blocks as the functional medium.
[0017] Furthermore, the side wall of the simulated outer cylinder is provided with an inlet and an overflow outlet near the top and outside the travel of the sealing pressure cover; the molding device also includes a grouting conduit; the grouting conduit extends from the inlet into the simulated pile hole.
[0018] Furthermore, the molding device also includes a monitoring component; the monitoring component is assembled with a sealing pressure cover through a high-pressure resistant dynamic sealing structure and is used to extend into the simulated outer cylinder for monitoring.
[0019] Furthermore, a pressure sensor is also installed near the bottom of the simulated outer cylinder.
[0020] Advantages of the present invention: The molding device for cast-in-place pile cementitious body generated by simulating the coupling of mud cake and sediment of the present invention has the following advantages:
[0021] 1. This invention solves the problem of physical distortion and separation of formation mechanism in the atmospheric pressure simulation of "mud cake-sediment": Existing simple models usually isolate mud cake and sediment under atmospheric pressure, resulting in the prepared specimens being loose and flocculated with extremely high porosity; This invention breaks through the single pressurization mode and pioneers the "fluid-solid coupling" design based on the deep high-pressure environment; Especially when simulating friction piles, it truly restores the two-way seepage process of "lateral wall radial filtration and skin formation" and "pile end vertical filtration and consolidation" of high-pressure mud into the reshaped simulated soil layer under pressure difference, as well as the dynamic settling process of suspended particles, so that the generated mud cake and sediment are infinitely close to the real state of deep strata in terms of density, porosity and physical and mechanical strength;
[0022] 2. Unique deep cavity structure completely eliminates stress boundary effects and realistically reproduces the constraints of different strata: This device abandons the traditional erroneous approach of using rubber pads for "geometric equivalence" and achieves for the first time a high-order physical simulation of "one machine, two working conditions"; when simulating friction piles filled with simulated soil layers, the experimental cavity provides the soil with a sufficient compression range to meet the large deformation under load, completely eliminating the bottom rigid reflection and stress boundary effects caused by conventional thin-layer pads, and realistically reproducing the seepage consolidation and elastic-plastic large deformation characteristics of semi-infinite space soft foundations; when simulating rock-socketed piles, by replacing the simulated rock layers in the experimental cavity, it can perfectly simulate the rigid watertight and impermeable constraints of dense bedrock;
[0023] 3. Completely solves the pain point of "non-destructive sampling" of multiphase interface cemented bodies: The interface of in-situ cemented "concrete-mud cake-rock (soil) body" is extremely fragile. Traditional whole cylindrical devices rely on external force to "forcefully push out" and will completely destroy the interface structure. This invention innovatively adopts a mechanical structure of "upper and lower series segmented + lower split independent molding chamber". After the in-situ pressure molding and curing period is over, only the simulated outer cylinder and flange that serve as the pressure transition section need to be removed. The lower cementing tank can be disassembled as an independent module. After removing the external hydraulic pressure and removing the water-proof flexible membrane, the split side wall simulated component can be laterally translated and separated. The complete original cemented surface can be taken out without friction and shear damage. This provides the most perfect original specimen preparation scheme for subsequent large-scale interface contact surface direct shear, compression and seepage mechanics tests.
[0024] 4. Revealed the high-pressure mutual feeding bonding and embedding mechanism of the "pile side-pile end" dual interface: This device can simulate the replacement and infiltration process of high-density mud cake and compacted sediment by high-pressure fluid concrete under tens or even nearly 100 meters of liquid column; at the same time, the unique mud overflow discharge port with control valve at the top perfectly replicates the "equal volume replacement" process of internal mud being squeezed out upward during tremie grouting; combined with the rough pore wall of the prefabricated simulated rock layer, this device can realistically drive fluid concrete to deeply infiltrate, split, compact and physically interlock into the extremely dense side wall mud cake, bottom sediment and pores under high pressure, thereby obtaining specimens with real transition layer structure and shear / compressive strength, providing absolutely reliable data support for evaluating the real bearing capacity of pile foundations;
[0025] 5. Pioneering high-pressure isolation and anti-crossflow structure with dual-loop sealing, ensuring ultimate safety and quantifiable parameters: Addressing the significant internal pressure, leakage, and stress dispersion risks encountered during deep pile simulation, this invention features a highly original sealing design: First, the combination of a variable-diameter transition flange and annular sealing cover firmly seals the top surface of the surrounding medium, precisely confining the vertical pressure within the simulated pile hole. This physically isolates the high-pressure mud from the potential for "short-circuit crossflow" to the surrounding sidewalls, preventing hydraulic boundary failure. Second, the ingenious use of high-pressure fluid within the annular confining cavity to "radially inwardly embrace" the water-resistant flexible membrane achieves absolute high-pressure water-resistant sealing of the split sidewall joints. Simultaneously, the integrated dynamic sealing probe and pressure sensor can capture real-time displacement and end resistance changes during the cementation and consolidation process, providing a high-precision data stream for revealing the pile foundation's stress mechanism. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of a molding device for a cast-in-place pile cementitious body generated by the coupling of mud skin and sediment, as shown in Examples 1 and 2.
[0027] Figure 2 This is a vertical cross-sectional schematic diagram of the internal structure of the cementing tank of a molding device for a cast-in-place pile cementitious body generated by the coupling of mud skin and sediment, as shown in Examples 1 and 2.
[0028] Figure 3 This is a schematic diagram of the internal structure of the cementing groove in the simulated rock-socketed pile cementing body forming process, viewed vertically in Example 1.
[0029] Figure 4 This is a schematic diagram of the internal structure of the cementing groove in the simulated friction pile cementing body forming in Example 2, viewed vertically.
[0030] Figure 5 This is a schematic diagram of the internal structure of the bonding groove in the simulated friction pile bonding body forming in Example 2, viewed from a cross-section.
[0031] Among them, 1-reaction frame, 2-top loading system, 3-sealed pressure cover, 4-feed inlet, 5-overflow outlet, 6-monitoring component, 7-simulated outer cylinder, 8-circumferential reinforcement, 9-support component, 10-pressure sensor, 11-transition flange, 12-bonding tank, 13-drain outlet, 14-support seat, 15-confining pressure loading system, 16-annular sealing cover plate, 17-simulated pile hole, 18-experimental chamber, 19-split sidewall simulation component, 20-filling chamber, 21-waterproof flexible membrane, 22-confining pressure chamber, 23-bearing type collection and drainage pipe, 24-simulated rock strata, 25-rough hole wall, 26-high rigidity filling block, 27-simulated soil layer, 28-smooth hole wall, 29-water collection and permeable filter material. Detailed Implementation
[0032] To enhance understanding of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. These embodiments are only used to explain the invention and do not limit the scope of protection of the invention.
[0033] Example 1
[0034] Please refer to Figures 1 to 5 As shown, this embodiment provides a molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud skin and sediment, including a reaction frame 1, a top loading system 2, a simulated outer cylinder 7, a transition sealing assembly, a cementing groove 12, and a support seat 14; the transition sealing assembly includes a transition flange 11 and an annular sealing cover plate 16 located below the transition flange 11; the top side of the transition flange 11 is connected to the bottom end of the simulated outer cylinder 7, and the bottom side is connected to the top end of the cementing groove 12; the bottom side of the cementing groove 12 is connected to the support seat 14, and the outer edge of the annular sealing cover plate 16 seals the inner wall of the cementing groove 12; the inner diameter of the simulated outer cylinder 7, the center hole of the transition flange 11, and the center hole of the annular sealing cover plate 16 are set to be of equal diameter; a split-type sidewall simulation assembly 19 is installed in the cementing groove 12, and the split-type sidewall simulation assembly 19 is formed by piecing together two semi-cylindrical blocks. The internal structure includes an experimental cavity 18 corresponding to the central hole of the annular sealing cover 16, used for filling experimental media. A water-resistant flexible membrane 21 is also installed within the bonding tank 12, dividing it into two cavities. A confining pressure cavity 22 is formed between the water-resistant flexible membrane 21 and the bonding tank 12, used for filling confining pressure media, and connected to the external confining pressure loading system 15. A filling cavity 20 is formed between the water-resistant flexible membrane 21 and the split-sidewall simulation component 19, used for filling functional media. The bottom surface of the annular sealing cover 16 forms the top surface of the confining pressure cavity 22 and the filling cavity 20, and is sealed to the top edge of the split-sidewall simulation component 19. The top loading system 2 is fixed below the top beam of the reaction frame 1, and a sealing pressure cover 3 is fixed to the lower end of the top loading system 2. The sealing frame cover 3 seals against the inner wall of the simulated outer cylinder 7 and can move vertically. Specifically, the simulated outer cylinder 7 adopts a segmented structure or has its inner wall coated with a release agent for easy demolding.
[0035] In this embodiment, the outer wall of the simulated outer cylinder 7 is provided with a plurality of circumferential reinforcing members 8 at axial intervals; the simulated outer cylinder 7 is also provided with a plurality of supporting members 9 for supporting the simulated outer cylinder 7 to stand upright. Specifically, the circumferential reinforcing members 8 are annular steel ribs or high-strength clamps welded or bolted to the outer wall of the simulated outer cylinder 7; the supporting members 9 are triangular support legs or base flanges provided on the middle and lower parts of the outer side of the simulated outer cylinder 7.
[0036] In this embodiment, the sidewall simulation component 19 is equipped with a load-bearing liquid collection and drainage pipe 23 on its sidewall and bottom; the bonding tank 12 is provided with a corresponding drainage port 13; the load-bearing liquid collection and drainage pipe 23 is fixed to the bonding tank 12 and connected to the drainage port 13; the load-bearing liquid collection and drainage pipe 23 is also provided with filter holes that are connected to the experimental chamber 18 and the filling chamber 20.
[0037] In this embodiment, during the molding of the simulated rock-socketed pile cement body, the experimental cavity 18 is filled with a simulated rock layer 24 as the experimental medium. The simulated rock layer 24 is pre-formed or naturally cut, and a simulated pile hole 17 with the same diameter as the inner diameter of the simulated outer cylinder 7 is opened on the top side of the simulated rock layer 24. The simulated pile hole 17 is processed to form a rough hole wall 25. The filling cavity 20 is filled with a high-rigidity filling block 26 as the functional medium. Together, they form an absolutely rigid impermeable water tightness test boundary.
[0038] In this embodiment, the side wall of the simulated outer cylinder 7 is provided with a feed inlet 4 and an overflow outlet 5 near the top and outside the travel of the sealing pressure cover 3; the molding device also includes a grouting conduit; the grouting conduit extends from the feed inlet 4 into the simulated pile hole 17.
[0039] In this embodiment, the molding device further includes a monitoring component 6; the monitoring component 6 is assembled with the sealing pressure cover 3 through a high-pressure resistant dynamic sealing structure and is used to extend into the simulated outer cylinder 7 for monitoring.
[0040] In this embodiment, a pressure sensor 10 is also provided near the bottom of the simulated outer cylinder 7.
[0041] This embodiment also provides the operation steps for in-situ forming of simulated rock-socketed piles:
[0042] 1. Assembly and preparation (construction of rigid watertight boundary):
[0043] First, a prefabricated high-strength geopolymer or natural rock block is used as a simulated rock layer 24. Its inner side is processed into a simulated rough hole wall 25, which is placed in a split sidewall simulation component 19 and assembled together to form a through simulated pile hole 17 in the center. A water-proof flexible membrane 21 is wrapped around its perimeter, and high-rigidity filler blocks 26 are filled to simulate the absolute rigidity constraint of dense bedrock. The whole assembly is placed in a cementing tank 12, and the support seat 14 is connected to the bottom of the cementing tank 12. Then, an annular sealing cover plate 16 and a transition flange 11 with a changing diameter are sequentially covered on the top of the cementing tank 12 to ensure that the annular sealing cover plate firmly presses down and seals the outer confining cavity 22 and the top surface of the water-proof flexible membrane 21. Only the central hole of the annular sealing cover plate is left to connect with the simulated outer cylinder 7 with the same diameter. Finally, each flange assembly is locked, and the outer cylinder is fixed by the circumferential reinforcement 8 and the support 9, and the top sealing pressure cover 3 is installed. Since it is a water-tight condition, each drain port 13 needs to be closed.
[0044] 2. Mud injection and initial sediment generation (simulating the initial generation environment and measuring thickness):
[0045] The confining pressure loading system 15 is activated to inject high-pressure fluid into the confining pressure chamber 22, which uniformly squeezes the water-resistant flexible membrane 21, so that the splicing seam of the split sidewall simulation component 19 achieves microscopic water-tight sealing; the feed port 4 is opened to fill the simulated outer cylinder 7 and the simulated pile hole 17 below with the prepared drilling mud; the feed port is closed, and the first stage steady-state pressure (simulating the hydrostatic pressure of tens of meters of liquid column in a deep water pile hole) is applied through the top loading system 2.
[0046] Maintain the hydrostatic pressure and let it stand. The particles in the mud will settle naturally under gravity, simulating the initial sediment formation environment before hole cleaning. At this time, the monitoring component 6 (such as a graduated high-pressure probe) is lowered through the sealed pressure cover to scan and record the thickness and formation pattern of the initial sediment in real time.
[0047] 3. Simulation of positive circulation hole cleaning and construction time delay (simulating secondary hole cleaning and final sediment generation):
[0048] The grouting pipe is passed through the inlet 4 to the bottom of the simulated pile hole 17. Fresh mud is continuously pumped into the bottom of the hole under high pressure using the positive circulation mud cleaning method. The high concentration of suspended solids and initial sediment in the hole are carried by the liquid flow returning from bottom to top and finally discharged from the overflow port 5 at the top. This truly replicates the secondary hole cleaning operation of "bottom grouting and top discharge" on site.
[0049] After the hole cleaning is completed, the grouting pipe is withdrawn, the relevant valves are closed, and the set first-stage hydrostatic pressure is maintained to force the hole to stand for a period of time. This standing period is used to realistically simulate the unavoidable time interval between "the completion of the steel cage hoisting and the first concrete pouring" (i.e., construction time lag). During this standing period, the residual suspended particles in the mud will undergo secondary settling towards the rigid constraint boundary at the bottom under the action of gravity and hydrostatic pressure, producing the final bottom sediment. At this time, the monitoring component 6 is used again to scan and record the dynamic thickness change of the final sediment generated during this time lag stage.
[0050] 4. Concrete pouring and secondary pressurization (secondary loading):
[0051] The process of grouting and replacement using a duct method is simulated. A grouting duct is installed at the bottom, and fluid concrete is pumped in through a high-pressure pump. The high-density fluid concrete fills the simulated pile hole 17 from bottom to top, while the original wall-protecting slurry is squeezed upward through the transition flange 11 with a variable diameter, and finally discharged through the overflow port 5, realizing a true equal volume replacement between the slurry and the concrete. After the replacement is completed, the overflow port 5 is closed, and a second stage of high pressure (simulating the overpressure generated by the self-weight of tens of meters of fluid concrete) is applied through the top loading system 2.
[0052] 5. In-situ pressure maintenance and sampling:
[0053] Under high pressure, the fluidized concrete compacts the sediment at the bottom of the hole and laterally interlocks and penetrates into the rough hole wall 25 of the simulated rough rock layer 24; the bottom pressure is measured in real time by the pressure sensor 10; the pressure is maintained until the cementitious material initially sets and the curing period is over.
[0054] During demolding, remove the top loading system 2, the simulated outer cylinder 7 and the transition flange (11); release the confining pressure, disassemble the outer shell of the bonding tank 12 and remove the flexible membrane 21). Finally, move the split sidewall simulation component 19 laterally along the splicing seam to separate it, so that the internal "concrete-sludge" and "concrete-rock wall" semi-cylindrical bonding samples can be obtained without frictional shear damage.
[0055] 6. Subsequent experiments:
[0056] After removing the non-destructive sample, it can be directly sent into a large direct shear apparatus or triaxial apparatus to carry out mechanical testing of the "concrete-rock" multiphase interface considering in-situ roughness and sediment coupling embedding effect.
[0057] Example 2
[0058] Please refer to the following: Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, the difference between this embodiment and Embodiment 1 is that: when the simulated friction pile cement body is formed, the experimental cavity 18 is filled with a reshaped simulated soil layer 27 as the experimental medium; a simulated pile hole 17 with the same diameter as the inner diameter of the simulated outer cylinder 7 is opened on the top side of the simulated soil layer 27, and the simulated pile hole 17 is processed to form a smooth hole wall 28; the filling cavity 20 is filled with a water-collecting and permeable filter material 29 as the functional medium. Specifically, the drain port 13 is connected to the pore water pressure servo control system on the outside; under the pressure difference drive of the high-pressure mud in the simulated pile hole 17, the mud water is allowed to undergo "radial filtration loss" on the side wall and "vertical seepage consolidation" at the bottom, so as to generate a squeezed mud cake in situ on the inner wall of the simulated pile hole 17, and can apply and maintain the set in-situ groundwater pore water pressure in the reverse direction.
[0059] This embodiment also provides the operation steps for in-situ forming of simulated friction pile conditions:
[0060] 1. Assembly and preparation (constructing a deep boundary layer with large deformation and high permeability):
[0061] The filling operation is similar to the steps in Example 1, except that the experimental medium is replaced by: using remolded in-situ soil as the simulated soil layer 27, and scraping the inner side to form a flat hole wall 28 that simulates a homogeneous soil layer; laying a water-collecting and permeable filter material 29 between the soil and the waterproof flexible membrane 21, and pre-embedding a load-bearing drainage pipe 23 here to achieve lateral liquid collection; other assembly steps are the same as those in Example 1.
[0062] 2. Slurry injection and initial filtration and skin formation (simulating the initial formation environment of sediment and mud skin):
[0063] High-pressure fluid is injected into the confining pressure chamber 22 through the confining pressure loading system 15, which uniformly squeezes the water-proof flexible membrane 21, so that the split side wall simulation component 19 is pressurized and tightened; at the same time, the pore water pressure servo system is activated, and the set in-situ groundwater pore water pressure is applied and maintained in the opposite direction through the side drain port 13 and the bottom drain port.
[0064] Mud is injected and a first-stage hydrostatic pressure is applied through the top loading system 2. Under the pressure difference, the water in the mud undergoes strong radial filtration through the soil pore wall and is discharged through the bearing-type collection and drainage pipe 23. The suspended particles are intercepted and squeezed to form the initial mud cake. At the same time, the water undergoes vertical seepage consolidation in the deep cavity at the bottom to form the initial sediment. The thickness of the initial sediment is measured using the monitoring component 6.
[0065] 3. Positive circulation cleaning and pressurized filter loss forming, secondary sediment generation (simulating secondary cleaning and construction time delay):
[0066] First, a "secondary cleaning" of the hole is carried out by using the positive circulation mud cleaning method (i.e., new mud is injected at the bottom and slurry is discharged from the top discharge port) through the grouting pipe that is lowered to the bottom to remove suspended matter and initial sediment in the hole; then the grouting pipe is withdrawn, the hydrostatic pressure of the liquid column is maintained and it is forced to stand still for a period of time to simulate the construction time delay before the steel cage is lowered to the first concrete pouring.
[0067] During the settling period, driven by the pressure difference between hydrostatic pressure and external groundwater pressure, the mud moisture continues to undergo strong radial filtration, forming the final dense mud cake in situ on the borehole wall; at the same time, the residual suspended particles undergo secondary vertical seepage into the bottom deep cavity 18, perfectly simulating the pressurized consolidation of the soft foundation under the seepage action during the settling period and the secondary settlement process of the final sediment; the final sediment thickness is recorded again using monitoring component 6.
[0068] 4. Concrete pouring replacement and secondary pressurization:
[0069] Perform the same operation as in the embodiment: high-pressure pumping of the fluidized concrete at the bottom and "equal volume replacement" grouting of the mud at the top; then apply a second stage of high pressure to drive the high-pressure fluidized concrete to penetrate and wed into the dense mud cake on the side wall, the soil pores and the compacted sediment to a deep depth.
[0070] 5. In-situ pressure curing and demolding sampling:
[0071] After pressure curing, the split-side wall simulation component 19 was horizontally and non-destructively peeled off using the demolding method described in Example 1. Because of the non-destructive horizontal translational separation, the originally fragile "mud skin-soil" transition interface, which was extremely susceptible to shear damage, was perfectly preserved.
[0072] 6. Subsequent mechanical tests:
[0073] The extracted original "concrete-mud cake-soil layer" friction pile composite cemented samples can be used for subsequent quantitative evaluation of the large deformation shear, compression and permeation consolidation characteristics of multiphase interfaces.
[0074] The above embodiments should not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent conversion fall within the protection scope of the present invention.
Claims
1. A device for forming a cementitious body for cast-in-place piles, simulating the coupling of mud cake and sediment, characterized in that, The system includes a reaction frame (1), a top loading system (2), a simulated outer cylinder (7), a transition sealing assembly, a bonding groove (12), and a support seat (14). The transition sealing assembly includes a transition flange (11) and an annular sealing cover plate (16) located below the transition flange (11). The top side of the transition flange (11) is connected to the bottom end of the simulated outer cylinder (7), and the bottom side is connected to the top end of the bonding groove (12). The bottom side of the bonding groove (12) is connected to the support seat (14), and the outer edge of the annular sealing cover plate (16) seals the inner wall of the bonding groove (12). The inner diameter of the simulated outer cylinder (7), the center hole of the transition flange (11), and the center hole of the annular sealing cover plate (16) are set to be the same. A split-type sidewall simulation assembly (19) is installed in the bonding groove (12). The split-type sidewall simulation assembly (19) is composed of two semi-cylindrical blocks joined together, and has a center hole that matches the center hole of the annular sealing cover plate (16). The corresponding experimental chamber (18) is used to fill the experimental medium; a water-proof flexible membrane (21) is also provided in the cementing tank (12) to divide the cementing tank (12) into two chambers; a confining pressure chamber (22) is formed between the water-proof flexible membrane (21) and the cementing tank (12) to fill the confining pressure medium and to communicate with the external confining pressure loading system (15); a filling chamber (20) is formed between the water-proof flexible membrane (21) and the split side wall simulation component (19) to fill the functional medium; the bottom surface of the annular sealing cover plate (16) forms the top surface of the confining pressure chamber (22) and the filling chamber (20) and is sealed with the top edge of the split side wall simulation component (19); the top loading system (2) is fixed under the top beam of the reaction frame (1), and a sealing pressure cover (3) is fixed at the lower end of the top loading system (2); the sealing frame cover (3) is sealed with the inner wall of the simulation outer cylinder (7) and can move vertically.
2. The molding device for a cast-in-place pile cementitious body generated by simulating the coupling of mud cake and sediment as described in claim 1, characterized in that, The outer wall of the simulated outer cylinder (7) is provided with several circumferential reinforcing members (8) at intervals along the axial direction; the simulated outer cylinder (7) is also provided with several supporting members (9) for supporting the simulated outer cylinder (7) to stand upright.
3. The molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment as described in claim 2, characterized in that, The split-type sidewall simulation component (19) is equipped with a load-bearing collection and drainage pipe (23) on its sidewall and bottom; the bonding tank (12) is provided with a corresponding drainage port (13); the load-bearing collection and drainage pipe (23) is fixed to the bonding tank (12) and connected to the drainage port (13); the load-bearing collection and drainage pipe (23) is also provided with a filter hole that is connected to the experimental chamber (18) and the filling chamber (20).
4. The molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment as described in claim 3, characterized in that, When the simulated friction pile cement body is formed, the experimental cavity (18) is filled with a reshaped simulated soil layer (27) as the experimental medium; the top side of the simulated soil layer (27) is provided with a simulated pile hole (17) with the same diameter as the inner diameter of the simulated outer cylinder (7), and the simulated pile hole (17) is processed to form a flat hole wall (28); the filling cavity (20) is filled with a water-collecting and permeable filter material (29) as the functional medium.
5. The molding device for a cast-in-place pile cementitious body generated by simulating the coupling of mud cake and sediment as described in claim 1, characterized in that, When the simulated rock-socketed pile cement body is formed, the experimental cavity (18) is filled with simulated rock layer (24) as the experimental medium; the simulated rock layer (24) is pre-formed or naturally cut and formed, and the top side of the simulated rock layer (24) is provided with a simulated pile hole (17) with the same diameter as the inner diameter of the simulated outer cylinder (7), and the simulated pile hole (17) is processed to form a rough hole wall (25); the filling cavity (20) is filled with a high-rigidity filling block (26) as the functional medium.
6. The molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment as described in claim 4 or 5, characterized in that, The simulated outer cylinder (7) has an inlet (4) and an overflow (5) located near the top and outside the travel of the sealing pressure cover (3); the molding device also includes a grouting conduit; the grouting conduit extends from the inlet (4) into the simulated pile hole (17).
7. The molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment as described in claim 1, characterized in that, The molding device also includes a monitoring component (6); the monitoring component (6) is assembled with the sealing pressure cover (3) through a high-pressure resistant dynamic sealing structure and is used to extend into the simulated outer cylinder (7) for monitoring.
8. The molding device for a cast-in-place pile cementitious body formed by simulating the coupling of mud cake and sediment as described in claim 1, characterized in that, The simulated outer cylinder (7) is also equipped with a pressure sensor (10) near the bottom.