I.Project Background and Objectives

To systematically study the comprehensive impact mechanisms of different rainfall intensities(0-300 mm/h)on various scenarios,including crop growth inhibition,river embankment and slope erosion,debris flow triggering and evolution,and urban drainage infrastructure(such as pipe network blockage,road flooding,and urban waterlogging),a high-precision,multi-scenario compatible large-scale artificial rainfall simulation laboratory will be constructed.This laboratory needs to achieve the following core functions:

Precise rainfall simulation:Rainfall intensity is continuously adjustable from 0-300 mm/h(accuracy±5%),and the raindrop size and distribution uniformity are close to natural rainfall.It supports the simulation of short-term heavy rainfall(such as more than 100 mm/h for 1 hour)and long-term cumulative rainfall(such as 30 mm/h for 24 hours).

Multi-scenario coupling test:Supports independent or combined deployment of different objects such as crop planting areas,river embankment slope protection models,debris flow simulated slopes,and urban drainage pipe network miniature systems(including pavement–pipeline–manhole components);

Dynamic Hazard Monitoring:Real-time acquisition of data on rainfall parameters(intensity,raindrop characteristics),surface and structural responses(soil moisture content,displacement,stress),and disaster evolution processes(scour depth,debris flow velocity,road surface water depth,and drainage network flow rate).

Safety and scalability:It has the ability to protect the equipment under extreme rainfall conditions and supports flexible expansion for future addition of test modules(such as freeze-thaw cycle coupled rainfall).

II.Overall Laboratory Design

(I)Site and Layout

Laboratory Size:The recommended building area is≥1000㎡(length×width×height=50m×20m×8m)to meet the layout requirements of large-scale integrated models(such as a 10m long urban road section,a 5m×3m embankment slope protection,and a 15m long debris flow slope);

Functional Zoning:

Core Rainfall Zone(40m×20m):A simulated rainfall system is installed on the roof,and the ground is a pressure-bearing experimental platform(bearing capacity≥5t/m²),divided into 4 independent sub-zones(farmland zone,embankment zone,debris flow zone,and urban drainage zone).Each zone can be separated or linked by movable partitions;

Model preparation area(10m×20m):for the preparation and construction of materials for crop planting,dam slope protection/debris flow slope/drainage network models(including soil/gravel storage,mixing equipment,and micro-pipeline prefabrication platform).

Observation and Control Area(10m×20m):Equipped with data acquisition terminals,a high-speed camera system,and a remote control console,supporting real-time adjustment of experimental parameters and recording of disaster processes;

Auxiliary Area(20m×20m):Includes a water supply system,a circulating water tank,a power control room,a sample processing room,and equipment maintenance space.

Environmental control:The indoor temperature is maintained at 15-30℃through the air conditioning system(to adapt to crop growth and material performance stability)and the relative humidity is≤80%(to reduce the interference of water evaporation);the ground is inclined at 3°(to drain the surrounding area),and a waterproof steel plate(thickness≥8mm)is laid.The drainage ditch is connected to a circulating water tank(rainwater recycling rate≥80%).

III.Core System Design

(I)Artificial Rainfall Simulation System

1.System Composition

The system adopts a"cantilevered sprinkler array+intelligent zone control"scheme,covering the core rainfall area(40m×20m).Multiple sets of sprinklers are independently controlled to achieve uniformity across the entire area and simulate high-intensity local rainfall.

Nozzle type:Select a combination of"refracting+rotating"nozzles(such as the NT series from Spraying Systems,USA,or domestic high-precision bionic nozzles).By adjusting the nozzle orifice diameter(0.5-1.2mm),water pressure(0.1-1.5MPa),and pitch angle(0-90°),simulate the raindrop size(0.5-5mm),final velocity(1-9m/s),and uniformity of distribution of natural rainfall.

Layout:The sprinklers are arranged in a matrix(2-3m spacing,5-7m height from the ground),divided into 8 independent control zones(5m×5m per zone).Each zone is equipped with an independent water supply branch pipe and an electric regulating valve,supporting high-intensity rainfall in a single zone(e.g.,local 100mm/h)and coordinated rainfall across the entire area(e.g.,50mm/h across the entire area).

Water supply pipeline:main pipeline(DN150)+branch pipeline(DN100/DN50),made of corrosion-resistant UPVC or stainless steel,equipped with pressure sensor(accuracy±0.5%FS),flow regulating valve(accuracy±1%)and flow meter(range 0-50m³/h,accuracy±1%).

2.Rainfall Intensity and Uniformity Control

Adjustment Range:0-300mm/h(continuously adjustable),Range Accuracy:10mm/h(0-100mm/h),5mm/h(100-200mm/h),1mm/h(200-300mm/h);

Uniformity assurance:The sprinkler layout is optimized through CFD simulation(ensuring that the overall rainfall deviation is≤±5%),and the sprinkler parameters of each zone are dynamically adjusted by combining the feedback data from real-time rain gauges(grid-arranged with a spacing of 3m×3m,a total of 16 gauges)(such as fine-tuning the sprinkler angle in the edge zone to compensate for edge effects).

Special modes:Support"Rainstorm Center Simulation"(local 3m×3m area reaches 300mm/h,gradually decreasing to 50mm/h in the surrounding area)and"Gradient Rainfall Simulation"(e.g.,gradually decreasing from 10mm/h at one end of the test area to 200mm/h at the other end to study the impact of runoff direction).

3.Raindrop Characteristics Simulation

Particle Size Distribution:By changing the nozzle orifice diameter(light rain:0.5-1mm;moderate rain:1-2mm;heavy rain:2-5mm)or superimposing nozzles with different orifice diameters,the raindrop spectrum characteristics of natural rainfall are matched(e.g.,light rain is dominated by small particles,while heavy rain contains large particle impacts).

Final velocity matching:By adjusting the nozzle height and water pressure,the final velocity of raindrops is made close to the natural value(final velocity of light rain is 1-3 m/s,and final velocity of heavy rain is 4-9 m/s),which enhances the realism of the simulation of soil erosion and structural impact.

(II)Multi-Scenario Coupled Experiment Module

1.Crop Simulation Module

Planting Area Design:Movable planting troughs(1m×0.5m×0.3m,PVC material,20 sets in total),filled with experimental soil(clay/sandy loam,prepared according to actual farmland soil),planted with typical crops(such as wheat,corn seedlings or highly similar simulated vegetation),supporting comparative experiments with different vegetation coverage(0-100%);

Environmental adaptation:The top is equipped with an adjustable shade net(simulating sunny and cloudy weather),and the bottom is laid with drip irrigation pipes(to maintain the basic moisture of the root system and avoid interference from non-rainfall factors).Light simulation lamps(adjustable light cycle)are optional.

2.River Embankment Slope Protection Simulation Module

Model Structure:Customizable concrete/geotextile slope protection model(3m×2m×1.5m,slope adjustable from 15°to 75°),internally equipped with earth pressure gauges(range 0-500kPa),pore water pressure gauges(range 0-100kPa),displacement sensors(accuracy±0.1mm),and strain gauges(to monitor slope stress);

Material Compatibility:Supports real embankment materials(such as gravel,clay mixture)or similar materials(mixed according to parameters such as shear strength and permeability coefficient),with a water collection trough at the slope toe(to collect eroded sediment and measure erosion).

3.Debris Flow Simulation Module

Slope Structure:An adjustable slope(20°-50°)of soil and rock mixture(15m×3m×2m),filled with crushed stone(5-20cm particle size),clay,and water(simulating saturation).A water storage tank is set at the top of the slope(simulating rainfall infiltration saturation).

Triggering device:simulates mudslides triggered by earthquakes/heavy rainfall by suddenly opening the bottom gate(simulating landslide initiation)or by vibration table excitation(frequency 0-50Hz,amplitude adjustable);

Flow monitoring:High-speed cameras(frame rate≥1000fps)and laser rangefinders are installed at the toe of the slope(to monitor the velocity of the debris flow front),and flow velocity meters(ultrasonic/electromagnetic)and accumulation volume measurement cameras(infrared night vision)are deployed in the channel to record the evolution of the debris flow.

4.Urban Drainage Pipeline Facilities Simulation Module

Miniature Pipeline System:A miniature model of the urban road-drainage pipeline network(10m×5m×1m)is built at a scale of 1:10 or 1:5,including:

Road Layer:Permeable/impermeable asphalt concrete simulated road surface(thickness 5-10cm),with different slopes(1%-5%)to simulate the cross slope of real roads;

Pipeline structure:Drainage pipes made of PVC/HDPE material(diameter 100-300mm,scaled according to actual proportions),connected to inspection wells(simulating blockage and overflow),and storm drains(collecting road runoff);

Ancillary facilities:curb stones,storm drain grates(simulating debris interception),and a groundwater level simulation layer(controlling groundwater infiltration);

Monitoring Focus:Road surface water depth(real-time measurement using laser level sensors),drainage network flow rate(electromagnetic flowmeters with±0.5%accuracy),internal pipe flow velocity(ultrasonic Doppler velocity meters),and manhole overflow conditions(recorded by high-definition cameras).

(III)Dynamic Monitoring and Data Acquisition System

1.Rainfall Parameter Monitoring

Rain gauge grid:An 8×8 grid(64 grids in total)is arranged in the experimental area.Each rain gauge has a measurement range of 0-500 mm/h and an accuracy of±2%,providing real-time feedback on rainfall intensity at each point.

Raindrop spectrometer:Two units(one covering farmland and one covering urban areas)are used to measure raindrop diameter distribution(0.2-8 mm),terminal velocity,and concentration,verifying the simulation effect of raindrop characteristics.

2.Monitoring of Test Subject Response

Soil/Structure Parameters:

Crop Area:Leaf surface moisture content(infrared sensor),root soil moisture content(TDR time domain reflectometer,accuracy±2%),plant tilt angle(tilt meter);

Embankment slope protection zone:Earth pressure(range 0-1000kPa),pore water pressure(range 0-200kPa),displacement(accuracy±0.01mm),crack width(laser rangefinder);

Debris flow zone:Slope acceleration(seismograph),sliding displacement(GNSS displacement meter),debris flow density(gamma-ray densitometer);

Urban drainage area:Road surface water depth(0-30cm,accuracy±1mm),pipe network flow rate(0-50L/s,accuracy±0.5%),internal pipe pressure(0-200kPa),manhole level(ultrasonic level gauge);

Disaster process recording:

High-speed cameras(4-6 units,covering key areas such as farmland erosion,slope collapse,debris flow evolution,and road surface water accumulation,resolution≥1920×1080,frame rate 100-1000fps);

3D laser scanner(scans slope/farmland/pipeline morphology before and after each test,with an accuracy of±1mm);

Video monitoring(full coverage,recording the entire test process).

3.Data Management Platform

Utilizing an industrial-grade PLC(such as Siemens S7-1500)+industrial computer,the platform integrates all sensor signals and transmits them to the server via Modbus/TCP protocol.

It displays real-time rainfall intensity curves and dynamic graphs of monitoring parameters(such as changes in road surface water over time and slope displacement trends).It supports historical data backtracking,multi-parameter correlation analysis(such as the relationship between rainfall intensity and pipeline overflow time),and AI-assisted threshold prediction(such as the probability of urban flooding under a certain rainfall intensity).

(IV)Auxiliary Systems

Water Supply System:

Water Source:Municipal tap water combined with a recirculating water tank(capacity:80 m³),equipped with multi-stage filters(removing impurities≥1μm),an ultraviolet disinfection unit,and a water softening system to prevent scaling and nozzle clogging.

Water Pumps:Variable-frequency centrifugal pumps(flow rate≥30 m³/h,head≥100 m),with automatic flow adjustment based on rainfall intensity;standby pumps(flow rate≥20 m³/h)to ensure continuous operation.

Make-up Water Control:Tank water levels are maintained by level sensors,while drainage channels are connected to the recirculating water tank for filtered reuse.

Power Supply System:Dual power supply configuration(municipal power+UPS uninterruptible power supply,capacity≥150 kVA).Critical equipment(e.g.,PLCs,sensors,and high-speed cameras)is equipped with backup batteries providing≥3 hours of operation.

Safety Protection:Protective fencing(1.5 m in height)is installed around the test area.During extreme rainfall conditions,the system automatically cuts off power and activates drainage pumps(flow rate≥80 m³/h).The control console is equipped with an emergency stop button,remote emergency braking,and audible and visual alarm functions.

IV.Technical Parameters

V.Implementation Plan and Budget(Example)

(I)Implementation Cycle

Design Phase(1.5 months):Requirements refinement,multi-scenario layout optimization,and drawing refinement;

Equipment Procurement(2.5 months):Customized production of sprinkler heads,sensors,water pumps,miniature pipe network materials,etc.;

Installation and Commissioning(3 months):Pipeline laying,system integration,and parameter calibration(including rainfall uniformity verification);

Acceptance Testing(1 month):Full-range strength verification and multi-scenario coupling tests(e.g.,heavy rain+urban flooding+embankment erosion).

(II)Budget Estimate(Reference)

VI.Innovation and Application Value

Technological Advancement:Domestically leading achievement of continuous adjustable rainfall across the entire range of 0-300mm/h+multi-scenario(agriculture/water conservancy/urban construction)coupled testing,with raindrop characteristics and uniformity reaching the international level;

Integrated disaster research:For the first time,it integrates the simulation of the entire chain of"natural rainfall-surface erosion-engineering structure failure-urban flooding",providing a scientific basis for comprehensive disaster prevention and mitigation under extreme climate conditions;

Engineering application value:It directly supports the optimization of dam design standards,the assessment of urban drainage network capacity,the selection of flood-resistant crop varieties,and the formulation of debris flow early warning thresholds,thus contributing to the construction of"resilient cities"and"smart agriculture".

Prepared by:Hebei Tianqixingzi Inspection Equipment Co.,Ltd.-Tianjian Technology Research Institute

(Note:The module configuration ratio and parameter details can be adjusted according to the specific application focus(such as focusing on urban flooding or dam protection).)