Test device and method for simulating process of foundation pit dewatering excavation under dynamic hydrological conditions

Abstract

The present application relates to geotechnical engineering physical model test technical field, especially to the test device and method for simulating the process of foundation pit dewatering and excavation under dynamic hydrological conditions, the device initiatively constructs the integrated test system of "three cavity isolation-bilateral boundary coordination-multiple process linkage", through the collaborative operation of modular model box system, high-precision hydraulic boundary control system, pit dewatering and excavation simulation system, multi-dimensional information synchronous acquisition system and central integrated control and data processing platform, the multi-field coupling process of dewatering and excavation construction of the foundation pit near water under the dynamic water level environment such as tide, reservoir water fluctuation is accurately reproduced, the present application solves the problem that the prior art cannot simulate the dynamic seepage and construction mechanics coupling effect, and provides a key test means for revealing the instability mechanism of the foundation pit near water and optimizing the design and construction scheme.

Description

Technical Field

[0001] This invention relates to the field of physical model testing technology in geotechnical engineering, and in particular to a test apparatus and method for simulating the dewatering and excavation process of foundation pits under dynamic hydrological conditions. Background Technology

[0002] With the expansion of urban space into waterfront areas, a large number of projects have emerged, such as deep foundation pits in coastal new areas, working shafts for cross-river tunnels, and slope support for reservoir drawdown zones. These projects face a common core scientific problem and technical challenge: the strong coupling between the periodically changing dynamic external water level and construction activities such as dewatering and earthwork excavation inside the foundation pit leads to the formation and evolution of complex unsteady seepage fields inside and outside the pit, which in turn significantly affects the stress on the support structure, the stability of the pit bottom against sudden inrush, and the deformation of the surrounding environment. Its mechanism is far more complex than that of foundation pits under static water level conditions.

[0003] Currently, research on this problem mainly relies on numerical simulation and physical model tests. While numerical simulation is less expensive, its reliability heavily depends on constitutive models and parameters that can accurately describe unsaturated-saturated seepage in soil, soil-structure contact, and dynamic boundary conditions. However, the applicability of these models and parameters under dynamic cyclic loading has not been fully verified. Traditional physical model testing equipment has significant limitations: 1) Distortion in boundary simulation: Simple periodic injection and drainage are often used to simulate water level changes, which makes it difficult to accurately control the amplitude, frequency, waveform and phase of the fluctuations, and cannot truly reproduce natural fluctuations such as tides; the permeable boundary used to separate areas often uses fixed perforated plates, whose permeability characteristics do not match the test soil, resulting in distortion of the seepage path; 2) Insufficient process coupling: The device has a single function, focusing on one aspect of seepage or stability, and lacks the ability to perform high-precision linkage control of multiple physical processes such as "external dynamic hydraulic loading", "active dewatering in the pit", "layered soil excavation" and "support structure action" in a time series. 3) Fragmented monitoring information: Monitoring methods are mostly limited to a small number of point sensors, lacking synchronous, full-field, and visualized observation of seepage field (spatial water head distribution), stress field (soil pressure distribution), and displacement field (especially internal deformation). The data dimensions are incomplete, making it difficult to support in-depth analysis of multi-field coupling mechanisms. 4) Model similarity and boundary effect issues: The simplified design of model dewatering wells and impermeable boundaries often ignores the similarity of the filtration process; the constraint effect of friction on soil deformation by the sidewall of the model box cannot be ignored.

[0004] Therefore, developing a comprehensive experimental system and standardized experimental methods capable of high-fidelity simulation of dynamic hydraulic boundaries, precise temporal coupling of multiple construction processes, integrated multi-dimensional synchronous monitoring of the entire cross-section, and effective control of model similarity and boundary effects has become an urgent need for the development of geotechnical engineering testing technology. This is of great significance for revealing the disaster mechanism of water-bearing foundation pit engineering and developing design theories. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a test device and method for simulating the dewatering and excavation process of foundation pits under dynamic hydrological conditions that is scientifically designed, functionally integrated, precisely controlled, and comprehensively monitored.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an experimental device for simulating the excavation process of foundation pit dewatering under dynamic hydrological conditions, characterized in that it comprises: Modular model box system; it is a rigid box without a cover, and the interior is divided into three independent but hydraulically connected chambers by two detachable and installable multi-functional water-proof plates: constant water pressure chamber, main test chamber and dynamic water level chamber; A high-precision hydraulic boundary control system includes a constant pressure subsystem connected to the constant pressure chamber to maintain hydrostatic pressure conditions, and a dynamic water level simulation subsystem connected to the dynamic water level chamber. The dynamic water level simulation subsystem includes a closed-loop control loop consisting of a waveform generator, a servo driver, a wave generator, and a water level feedback sensor, which can be programmed to generate and stably output dynamic water level changes with preset amplitude, frequency, waveform, and phase. The pit dewatering and excavation simulation system is set inside the main test chamber and includes at least one modular dewatering well, a micro-precision pumping unit connected to the dewatering well, a metering unit for real-time monitoring of the water level and flow rate in the well, and a set of non-disturbance excavation device for layered and refined removal of soil. A multi-dimensional information synchronous acquisition system includes a multi-physics field sensor array deployed on the soil matrix and support structure inside the main test chamber, a water level pressure measuring pipe system arranged in a matrix on the back plate of the box, and an image and video recording unit facing the main test chamber. The sensor array includes at least a pore water pressure sensor, an earth pressure sensor, and a displacement sensor. The central integrated control and data processing platform is connected to the high-precision hydraulic boundary control system, the pit dewatering and excavation simulation system, and the multi-dimensional information synchronous acquisition system. The platform is equipped with a test process editing module, an equipment driving and synchronous triggering module, and a multi-channel high-speed data acquisition and storage module, which are used to execute preset multi-process coupled test sequences and realize synchronous acquisition and preliminary processing of monitoring data.

[0007] Furthermore, the multifunctional water-resistant plate is a perforated steel plate, and the diameter, spacing and distribution pattern of the permeable holes are designed according to the Darcy flow similarity criterion, so that the overall permeability of the plate can be continuously or in stages within the range of 30%-60%; the two sides of the multifunctional water-resistant plate are tightly covered with at least one layer of geotextile filter cloth.

[0008] Furthermore, one side wall of the main test chamber of the modular model box system is a full-length high-strength transparent observation window with a precision coordinate grid etched on its inner surface; the opposite side wall is an integrated monitoring backplate, which is prefabricated with a matrix of sealed pressure measuring tube quick interfaces and a modular multi-channel sensor wire sealing kit.

[0009] Furthermore, the modular dewatering well includes a well pipe, a filter section, and a wellhead device; the filter section is a pipe section with a series of filter holes on its sidewall, and its outer periphery is wrapped with a customized geotextile filter layer that matches the particle size distribution of the test soil; the wellhead device is equipped with a quick connection interface for the pumping unit and monitoring instruments.

[0010] Furthermore, the wave generator of the dynamic water level simulation subsystem is a variable frequency peristaltic pump or a low-disturbance axial flow pump that can rotate in both directions. By changing the pump's speed and direction control program, the water can be transported in both directions with precision, thereby generating target fluctuations in the dynamic water level chamber.

[0011] Furthermore, the image and video recording unit of the multi-dimensional information synchronous acquisition system includes a high-definition high-speed camera facing the transparent observation window, and a miniature waterproof endoscope camera that can be inserted into a pre-set observation channel in the soil.

[0012] Furthermore, the central integrated control and data processing platform also integrates a real-time data visualization dashboard, which can simultaneously display dynamic water level curves, pit precipitation curves, time-series curves of key measuring point sensor data, and real-time video footage during the experiment.

[0013] An operating method for operating a test apparatus that simulates the dewatering and excavation process of a foundation pit under dynamic hydrological conditions includes the following steps: S1: Test system configuration and initialization: Install multi-functional water-proof plates with corresponding permeability according to the test plan, install the model support system in the main test chamber, deploy and fix sensors, and complete the system sealing test and zero-point calibration of all instruments; S2: Layered soil preparation and integrated sensor installation: Using the sand rain method or layered compaction method, the test soil is filled in layers in the main test chamber. After each layer is filled, its density and uniformity are checked. Before filling to the preset height, various internal sensors are installed according to the design spatial coordinates. S3: Soil saturation and initial seepage field establishment: The soil is fully saturated from bottom to top through the water injection system. Then, the water levels in the constant water pressure chamber and the dynamic water level chamber are adjusted to the same initial design elevation, and the soil is allowed to stand for a sufficient time to complete the primary consolidation, forming a stable initial seepage field and stress field. S4: Multi-process Coupled Test Execution and Synchronous Monitoring: A comprehensive test process including dynamic water level parameters, excavation layer parameters, dewatering control parameters, and the duration of each stage is set on the central control platform; the process is started, and the system executes automatically and synchronously: periodic water level fluctuations are applied to the dynamic water level chamber, while in the main test chamber, the operation is carried out in a cycle of "dewatering the current soil layer to the target depth → static monitoring of seepage field redistribution → fine excavation of the soil layer → static monitoring of soil and structural response" until the final depth is reached; throughout this process, all sensor data, pressure gauge data, equipment operating status data, and image and video data are collected and stored synchronously. S5: Multi-source monitoring data fusion and mechanism analysis: After the experiment, digital image correlation technology was used to process the observation window video to obtain the full-field displacement and strain field of the soil surface; the video analysis results, sensor time-series data, and water level data were synchronized in time and mapped spatially to carry out multi-physics coupling analysis, revealing the system response law under the dynamic water level-precipitation-excavation coupling effect. Furthermore, in step S4, the "dewatering in the pit" is controlled using a constant flow rate mode or a constant drawdown mode; the "refined excavation" uses a micro vacuum suction device to remove a specified volume of soil with minimal disturbance, and the removed soil sample is weighed and recorded to verify the accuracy of the excavation volume.

[0014] Furthermore, the method also includes a comparative test mode: by shutting down the dynamic water level simulation subsystem and repeating step S4, a comparative test under static water level conditions is conducted, thereby quantitatively separating and evaluating the impact of dynamic water level fluctuation factors on the response of the foundation pit system.

[0015] By adopting the aforementioned technical solution, the beneficial effects of the present invention are: 1. Realism and adjustability of boundary simulation: The use of an adjustable permeability baffle plate designed based on the seepage similarity principle ensures the matching of the model boundary with the prototype seepage characteristics; the dynamic water level simulation system with high-precision closed-loop control can reproduce various hydrological conditions from simple harmonic waves to irregular waves, which greatly improves the realism of the boundary simulation.

[0016] 2. Automation and precision of multi-process coupling: The central control platform can arrange dynamic water level fluctuations, stratified dewatering, stratified excavation, static observation and other processes into complex time series programs and execute them automatically, realizing precise time-series coupling of multiple processes that is difficult to achieve manually, and the test repeatability is good.

[0017] 3. Three-dimensional and synchronized monitoring system: Combining the internal sensor network (point type), backplane pressure tube array (line / surface type) and surface machine vision measurement (full field type), a multi-dimensional monitoring system combining "point-line-surface-volume" is formed, and all data are collected based on a unified time scale, providing a complete data chain for multi-field coupled analysis.

[0018] 4. Standardization and similarity of model components: The modular design of the dewatering well emphasizes the functional similarity between the filter layer and the prototype, reducing the distortion of the model well; the low-friction inner wall treatment and reinforcing rib design effectively suppress the boundary constraint effect and improve the reliability of the test results.

[0019] 5. Systematic and extensible methodology: A standardized methodology has been developed, encompassing model preparation, saturated consolidation, coupled experiments, and data fusion analysis. This methodology can be used not only for mechanistic studies but also for verifying numerical models, inverting soil parameters, and testing the effectiveness of new support or dewatering techniques, making it widely applicable. Attached Figure Description

[0020] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a three-dimensional schematic diagram of the overall structure of the experimental device of the present invention; Figure 2 This is a top view of the overall structure of the experimental device of the present invention; Figure 3 for Figure 1 Top view I-I sectional view of the modular model box system in the device shown (showing the three-chamber layout); Figure 4 This is an exploded structural diagram of a multifunctional water-resistant panel assembly. Figure 5 Detailed longitudinal profile of a modular dewatering well; Figure 6 The image shows a front view and a magnified partial view of the integrated monitoring backplane. Figure 7 This is a block diagram of the dynamic water level simulation subsystem in a high-precision hydraulic boundary control system. Figure 8 This is a flowchart illustrating the overall steps of the experimental method of the present invention; Explanation of reference numerals in the attached drawings: 100-Modular model box system, 110-Constant water pressure chamber, 120-Main test chamber, 121-Transparent observation window, 122-Coordinate grid, 130-Dynamic water level chamber, 140-Multifunctional water-tight plate, 141-Permeable hole array, 142-Geotextile filter mesh, 151-Piercing pipe quick interface, 160-Structural reinforcing rib; 200-High-precision hydraulic boundary control system, 223-Wave generator (pump), 300-In-pit dewatering and excavation simulation system, 310-Modular dewatering well, 311-Well pipe, 312-Filter section, 313-Customized filter layer, 314-Wellhead device, 400-Multidimensional information synchronous acquisition system, 413-Wire displacement meter, 414-Laser displacement sensor, 420-Water level piezometer system. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] Please see Figures 1-8 The experimental apparatus in this embodiment mainly includes the following subsystems: 1. Modular model box system 100 This system forms the foundation of the entire device. The enclosure dimensions are 240 cm (length) × 70 cm (width) × 100 cm (height), welded from steel plates with a thickness of ≥8 mm to ensure rigidity. The interior is divided into three chambers by two multi-functional baffles 140. (See Multi-functional Baffle 140). Figure 3 The key innovative component is the partition plate, made of 8 mm thick Q235 steel plate. Based on similarity theory calculations, 5 mm diameter circular holes are drilled into it in a quincunx pattern. By changing the plate with different pore densities or using movable plates with adjustable opening areas, the overall permeability can be adjusted between 30% and 60% (e.g., 46% for medium sand). A 400-mesh stainless steel filter screen (inner side) and a 100-mesh nylon filter cloth (outer side) are glued to both sides of the plate with waterproof adhesive, forming a gradient filtration system that allows water to flow freely while effectively intercepting soil particles. Sealing rubber strips are embedded around the partition plate, which is bolted to the pre-set grooves on the side wall of the housing to ensure a tight seal and facilitate disassembly and cleaning.

[0023] The front of the main test chamber 120 features a 20 mm thick tempered acrylic transparent observation window 121, with a 10 mm × 10 mm coordinate grid 122 laser-etched on the inner surface for deformation observation and positioning. The rear panel is an integrated monitoring backplate with a modular, partitioned design. The upper part contains a 10 × 4 matrix arrangement of quick-connect interfaces 151 for pressure gauges (such as pagoda connectors with self-sealing valves), while the lower part contains multiple sensor wire sealing kits (each kit containing multiple waterproof glands), achieving standardized wiring and reliable sealing. The outer perimeter of the chamber is welded with structural reinforcing ribs 160 made of channel steel, and the inner wall is coated with PTFE to reduce friction.

[0024] 2. High-precision hydraulic boundary control system 200 The constant pressure water pressure subsystem consists of a high-level constant pressure water tank, a precision float valve, and an overflow pipe, which is connected to the constant pressure water chamber 110 to maintain water level fluctuations of less than ±1 mm.

[0025] The dynamic water level simulation subsystem is another core component. Its hardware includes: a waveform generator and controller (such as an industrial PLC or advanced microcontroller with integrated PID control algorithms), capable of programmably setting sine, triangular, square, or custom waveforms; a servo driver receiving control signals; a wave generator 223 using a high-flow-rate programmable peristaltic pump (such as a WT600-2J), whose flexible pump head connects to the inlet and outlet pipes of the dynamic water level chamber 130, precisely controlling the pump's speed and direction to "push and pull" the water; and a water level feedback sensor employing a high-precision laser rangefinder or an immersion pressure sensor to monitor the water level in the dynamic water level chamber 130 in real time and feed the signal back to the controller, forming a closed-loop control to ensure that the output water level matches the set waveform height, with amplitude control accuracy reaching ±0.5 mm.

[0026] 3. In-pit dewatering and excavation simulation system 300 like Figure 4 As shown, the modular dewatering well 310 uses a transparent PVC pipe with an outer diameter of 20 mm as the well casing 311. The lower 200 mm section is a filter section 312, with densely packed small holes drilled into the pipe wall. It is wrapped with two custom-designed filter layers 313: the inner layer is a needle-punched non-woven geotextile with a pore size of approximately 0.1 mm, and the outer layer is a nylon mesh with a pore size of approximately 0.5 mm. The two layers are sewn together with fine thread to ensure water permeability and sand control. The wellhead device 314 has a threaded interface for easy connection to the pumping pipe and a miniature water level gauge.

[0027] The miniature precision pumping unit uses a miniature variable speed peristaltic pump (such as the Kamoer KDS), whose flow rate can be precisely adjusted in the range of 0-1500 mL / min by the controller, and is equipped with an electronic balance to weigh the pumped water volume in real time to verify the flow rate.

[0028] The non-disturbing excavation device is a miniature vacuum suction system, including a miniature vacuum pump, a dust collection container, and a graduated suction nozzle. It can quantitatively and precisely remove soil from a designated area and depth with minimal disturbance to the surrounding soil.

[0029] 4. Multi-dimensional information synchronous acquisition system 400 A multi-physics sensor array includes pore water pressure sensors (such as miniature piezometers with a range of 0-50 kPa and an accuracy of 0.1% FS) and earth pressure sensors (such as miniature earth pressure cells with a range of 0-100 kPa), which are embedded in the soil and before and after the retaining piles according to a predetermined profile. Displacement sensors include a wire displacement meter 413 at the top of the retaining pile and a laser displacement sensor 414 on the soil surface.

[0030] Water level piezometer system 420: It consists of 32 transparent plastic tubes with an inner diameter of 3 mm. They are inserted into the soil at different depths through the quick interface 151 of the piezometer plate and connected to the scale plate outside the box for manual observation of water head.

[0031] Image and video recording unit: includes an industrial high-speed camera (e.g., 60 megapixels, 100 fps) facing the observation window to record the entire process; an optional 8 mm diameter waterproof endoscope can be inserted into a pre-set transparent conduit at specific stages of the experiment to observe changes in the microstructure of the soil.

[0032] 5. Centralized integrated control and data processing platform The platform is built using industrial control computers and LabVIEW or custom-developed host computer software. The software interface includes: an experimental process editing area (graphical programming, allowing setting parameters and durations for each stage), an equipment control panel, a real-time data display area (curves and numbers), and a video monitoring window. The platform communicates with each subsystem via RS-485, USB, and Ethernet, using a high-precision hardware clock as a reference to synchronously trigger all actions and collect all data, storing it as a data file with a unified timestamp.

[0033] The implementation process of the experimental method: Reference Figure 7 The flowchart illustrates the "Dewatering Excavation of Sandy Soil Foundation Pit under Tidal Action" test conducted using the aforementioned device. The specific steps are as follows: S1: Test system configuration and initialization.

[0034] Install a multi-functional water-resistant panel 140 with a permeability of 46%. Install acrylic panels (70×50×1cm, length×width×thickness) as support structures at both ends of the main test chamber 120. Install sensor probes at planned locations behind the wall, in front of the wall, and at the bottom of the pit, with wires led out through sensor wire sealing kits. Perform initial calibration on all sensors. Check the sealing of the model box and all pipelines.

[0035] S2: Soil layer preparation and sensor integrated installation.

[0036] The "sand rain method" was used to fill standard sand (medium sand). d 50 =0.35 mm). By controlling the drop height and moving speed, the density of each layer (5 cm thick) is made uniform. After each layer is filled, the compaction degree of each layer of soil is tested with a micro penetrator to ensure consistency. According to the foundation pit monitoring design plan, pore water pressure sensors and earth pressure sensors are buried in the soil as shown in the figure, ensuring that their sensing surfaces are correctly oriented and in close contact with the soil. When the filling reaches 10 cm from the design surface, displacement monitors are placed on the soil surface and the wire displacement gauges at the top of the support piles.

[0037] S3: Soil saturation and initial seepage field establishment.

[0038] Close all drain valves. Through the inlet valves of the constant pressure water system and the dynamic water level simulation subsystem, slowly inject water from the bottom of the tank into both chambers. Utilize capillary action and seepage to fully saturate the soil from bottom to top, preventing air bubbles from accumulating. After the water level in the pressure gauge stabilizes, adjust the water level on both sides to 5 cm below the soil surface (initial water level). Allow it to stand for 72 hours, monitoring the pore water pressure and displacement sensor readings during this period. Initial consolidation is considered complete when these readings stabilize and there is no significant settlement on the soil surface.

[0039] S4: Multi-process coupled test execution and synchronous monitoring.

[0040] Programming on the central platform: Dynamic water level parameters: set as a sine wave with an amplitude of 15 cm and a period of 12 hours (simulating a semi-diurnal tide).

[0041] Excavation parameters: Excavation is carried out in 4 layers, with each layer having a depth of 10 cm, for a total depth of 40 cm.

[0042] Dewatering parameters: Before each layer is excavated, the dewatering well pump is started and operated in constant flow mode until the water level in the observation well in the pit drops to 15 cm below the bottom surface of the excavation layer (safe over-depth), then dewatering is stopped.

[0043] Settling time: Let it stand after rainfall. T 1 = 30 minutes, let stand after excavation T 2 = 60 minutes.

[0044] Data acquisition: All sensor data are acquired at a frequency of 1 Hz throughout the process, and the camera captures images at 1 frame per second.

[0045] After clicking "Start," the system runs automatically: First, the wave pump starts working, and the water level in the dynamic water level chamber begins to fluctuate periodically at 130. Next, the first cycle begins: the platform triggers the water pump, pumping water to the target drawdown depth and then stopping, followed by a 30-minute settling period. After the settling period, the operator (or a robotic arm that can be integrated in the future) uses a non-disturbance excavation device to precisely remove the first 10 cm thick layer of soil, followed by a 60-minute settling period after excavation. All monitoring continues during the settling period. After the first cycle, the second cycle automatically begins, and so on, until the fourth layer of excavation and settling is complete. Throughout the entire process, the dynamic water level fluctuations continue uninterrupted by the excavation and dewatering cycle, realistically simulating the continuous tidal conditions during construction.

[0046] S5: Multi-source monitoring data fusion and mechanism analysis.

[0047] After the experiment, all data were exported. First, the video captured by the high-speed camera was processed using Digital Image Correlation (DIC) software (such as GOMCorrelate). Based on the coordinate grid on the observation window, the horizontal and vertical displacement cloud maps and strain field evolution animations of the soil on the side of the foundation pit throughout the entire experiment were calculated. Subsequently, the displacement time histories of specific points, time histories of all pore water pressure sensors, time histories of water head of each row of piezometers, earth pressure and displacement time histories of the support structure, and time histories of dynamic water level and water level in the pit obtained from DIC were aligned and integrated with a unified time axis. By comparing the spatial distribution and rate of change of various field quantities at key moments such as high tide, low tide, instantaneous precipitation, and instantaneous excavation, the following core scientific questions can be quantitatively analyzed: how the tidal phase affects the seepage direction and hydraulic gradient outside the pit; how dynamic seepage modulates the water and soil pressure on the support structure; and the stress release and dynamic seepage superposition effect caused by precipitation and excavation.

[0048] Furthermore, as an extension of this method, a comparative experiment can be conducted: under identical soil, support, and excavation parameters, only the dynamic water level fluctuation is turned off (maintaining the static water level), and step S4 is repeated. By comparing all monitoring results from the dynamic and static sets of experiments, the contribution of the single factor of "dynamic water level fluctuation" to various responses of the foundation pit system (such as maximum lateral displacement, settlement range outside the pit, maximum bending moment of the support, etc.) can be clearly identified and quantified, providing a direct basis for risk assessment.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions, characterized in that: include: Modular model box system; it is a rigid box without a cover, and the interior is divided into three independent but hydraulically connected chambers by two detachable and installable multi-functional water-proof plates: constant water pressure chamber, main test chamber and dynamic water level chamber; A high-precision hydraulic boundary control system includes a constant pressure subsystem connected to the constant pressure chamber to maintain hydrostatic pressure conditions, and a dynamic water level simulation subsystem connected to the dynamic water level chamber. The dynamic water level simulation subsystem includes a closed-loop control loop consisting of a waveform generator, a servo driver, a wave generator, and a water level feedback sensor, which can be programmed to generate and stably output dynamic water level changes with preset amplitude, frequency, waveform, and phase. In-pit dewatering and excavation simulation system; It is set inside the main test chamber and includes at least one modular dewatering well, a micro precision pumping unit connected to the dewatering well, a metering unit for real-time monitoring of the water level and flow rate in the well, and a set of non-disturbing excavation device for layered and refined removal of soil. A multi-dimensional information synchronous acquisition system includes a multi-physics field sensor array deployed on the soil matrix and support structure inside the main test chamber, a water level pressure measuring pipe system arranged in a matrix on the back plate of the box, and an image and video recording unit facing the main test chamber. The sensor array includes at least a pore water pressure sensor, an earth pressure sensor, and a displacement sensor. Centralized integrated control and data processing platform; It is communicatively connected to the high-precision hydraulic boundary control system, the pit dewatering and excavation simulation system, and the multi-dimensional information synchronous acquisition system. The platform is equipped with a test process editing module, an equipment driving and synchronous triggering module, and a multi-channel high-speed data acquisition and storage module, which are used to execute preset multi-process coupled test sequences and realize synchronous acquisition and preliminary processing of monitoring data.

2. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 1, characterized in that: The multifunctional water-proof plate is a perforated steel plate. The diameter, spacing and distribution pattern of the permeable holes on it are designed according to the Darcy flow similarity criterion, so that the overall water permeability of the plate can be continuously or in stages within the range of 30%-60%. The multifunctional waterproofing board has at least one layer of geotextile filter mesh tightly attached to both sides.

3. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 1, characterized in that: One side wall of the main test chamber of the modular model box system is a full-face high-strength transparent observation window, the inner surface of which is etched with a precision coordinate grid. The opposite sidewall is an integrated monitoring backplane, which is pre-fabricated with a matrix of sealed pressure gauge quick-connect interfaces and modular multi-channel sensor lead sealing kits.

4. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 1, characterized in that: The modular dewatering well includes a well pipe, a filter section, and a wellhead device; the filter section is a pipe section with a series of filter holes on its sidewall, and its outer periphery is wrapped with a customized geotextile filter layer that matches the particle size distribution of the test soil; the wellhead device is equipped with a quick connection interface to the pumping unit and monitoring instruments.

5. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 1, characterized in that: The wave generator of the dynamic water level simulation subsystem is a variable frequency peristaltic pump or a low-disturbance axial flow pump that can rotate in both directions. By changing the pump's speed and direction control program, the system achieves bidirectional and precise water delivery, thereby generating target fluctuations within the dynamic water level chamber.

6. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 1, characterized in that: The image and video recording unit of the multi-dimensional information synchronous acquisition system includes a high-definition high-speed camera facing a transparent observation window, and a miniature waterproof endoscope camera that can be inserted into a pre-set observation channel in the soil.

7. The experimental apparatus for simulating the dewatering and excavation process of a foundation pit under dynamic hydrological conditions as described in claim 6, characterized in that: The central integrated control and data processing platform also integrates a real-time data visualization dashboard, which can simultaneously display dynamic water level curves, pit precipitation curves, time-series curves of sensor data at key measuring points, and real-time video footage during the experiment.

8. An operating method for operating the experimental apparatus as described in claim 7, which simulates the dewatering and excavation process of a foundation pit under dynamic hydrological conditions, characterized in that: Includes the following steps: S1: Test system configuration and initialization: Install multi-functional water-proof plates with corresponding permeability according to the test plan, install the model support system in the main test chamber, deploy and fix sensors, and complete the system sealing test and zero-point calibration of all instruments; S2: Layered soil preparation and integrated sensor installation: Using the sand rain method or layered compaction method, the test soil is filled in layers in the main test chamber. After each layer is filled, its density and uniformity are checked. Before filling to the preset height, various internal sensors are installed according to the design spatial coordinates. S3: Soil saturation and initial seepage field establishment: The soil is fully saturated from bottom to top through the water injection system. Then, the water levels in the constant water pressure chamber and the dynamic water level chamber are adjusted to the same initial design elevation, and the soil is allowed to stand for a sufficient time to complete the primary consolidation, forming a stable initial seepage field and stress field. S4: Multi-process Coupled Test Execution and Synchronous Monitoring: A comprehensive test process including dynamic water level parameters, excavation layer parameters, dewatering control parameters, and the duration of each stage is set on the central control platform; the process is started, and the system executes automatically and synchronously: periodic water level fluctuations are applied to the dynamic water level chamber, while in the main test chamber, the operation is carried out in a cycle of "dewatering the current soil layer to the target depth → static monitoring of seepage field redistribution → fine excavation of the soil layer → static monitoring of soil and structural response" until the final depth is reached; throughout this process, all sensor data, pressure gauge data, equipment operating status data, and image and video data are collected and stored synchronously. S5: Multi-source monitoring data fusion and mechanism analysis: After the experiment, digital image correlation technology was used to process the video of the observation window to obtain the displacement and strain field of the soil surface. The video analysis results, sensor time series data and water level data were synchronized in time and mapped in space to carry out multi-physics field coupling analysis and reveal the system response law under the dynamic water level-precipitation-excavation coupling effect.

9. The operating method according to claim 8, characterized in that: In step S4, the dewatering in the pit is controlled using a constant flow rate mode or a constant drawdown mode; the fine excavation of the soil uses a micro vacuum suction device to remove a specified volume of soil with minimal disturbance, and the removed soil sample is weighed and recorded to verify the accuracy of the excavation volume.

10. An operating method according to claim 9, characterized in that: The method also includes a comparative test mode: by shutting down the dynamic water level simulation subsystem and repeating step S4, a comparative test under static water level conditions is conducted to quantitatively separate and evaluate the impact of dynamic water level fluctuation factors on the response of the foundation pit system.

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