Technical methods of collapse investigation and evaluation

The investigation and evaluation of collapse geological disasters involves many technical methods, including remote sensing image interpretation, engineering geological mapping, geophysical exploration, drilling, mountain engineering, indoor and field tests, model tests and simulation tests, dynamic monitoring and so on.

Interpretation of (1) remote sensing images

1. Basic requirements

1) Remote sensing image interpretation should be completed in the data collection stage, and the engineering geological interpretation map should be compiled to serve the field reconnaissance and design compilation.

2) Aerial photographs of 1: 50000 ~ 1: 67000 are used for regional interpretation, and large-scale aerial photographs (1:10000 ~1:1000) are used for the collapsed part. When conditions permit, multi-temporal color infrared, infrared, color, black and white, side-looking radar and other aerial photos should be used for comprehensive interpretation.

3) Generally, visual interpretation is adopted, and aerial photos are optically and digitally processed as much as possible to highlight effective information and improve the level and effect of interpretation.

4) Establish intuitive explanatory signs (shape, size, shadow, gray level, tone, pattern, etc.). ) and indirect interpretation signs (water system, vegetation, soil, natural landscape and human landscape, etc. ) different aerial photos; Conduct indoor interpretation, compile and interpret geological maps and photo mosaic maps, plan investigation work and key problems to be solved.

5) Conduct interpretation verification, establish accurate interpretation marks, establish and improve interpretation cards and verification cards, and accumulate detailed and accurate geological data.

6) The submitted results are as follows: ① Graphic translation of disaster geology; 2 interpret the card; ③ verification card; ④ Collection of typical photos; ⑤ Interpret the report; ⑥ Other explanatory maps required for investigation.

2. Interpret the content

1) to divide geomorphic units and establish geomorphic morphology, genetic types, micro-geomorphic morphology and development characteristics; Determine the relationship between topography and geological structure, stratum lithology and engineering geological conditions; Determine the geomorphic unit produced by the collapse body, and analyze and judge the relationship between collapse and geomorphology.

2) Explain the stratigraphic and lithologic characteristics of the collapsed body.

3) Interpret the relationship between collapse and structure. Determine the distribution and scale of main structural features (folds and faults) and their relationship with the formation of collapse.

4) Explain the role and influence of surface water and groundwater on the formation of collapse and the stability of its deposits. Determine large springs, spring groups and groundwater overflow zones, determine the distribution of karst phenomena such as depressions, funnels, sinkholes, etc., delineate the distribution range of surface water bodies, and understand the development characteristics of water systems.

5) Explain the boundary of the collapsed body, infer its thickness and volume, and judge its formation mechanism and type. According to the landform, vegetation and color infrared image characteristics of the subsidence area, the formation time and stability of the subsidence are analyzed preliminarily.

6) Infer the volume, scope, orientation and displacement distance of the future collapse of dangerous rock mass, delineate the disaster area, analyze the derivative disasters and preliminarily evaluate the disaster situation.

(2) Engineering Geological Surveying and Mapping

1. Basic requirements

Determination of 1) scale: the comprehensive regional engineering geological map is1:25000 ~1:50000; The environmental geological mapping of collapse disaster is1:10000 ~1:kloc-0/000, and the mapping in the feasibility study stage is 1: 2000 ~ 1: 500.

2) Surveying and mapping scope: geological survey of peripheral environment, based on finding out the geological environment and collapse development law related to the formation of collapse body in a small area; The surveying and mapping range of the collapsed body should be 1.5 ~ 3 times of its initial length and width, and should include the range that may cause harm and derivative disasters.

3) The topographic map used must be the same as or larger than the surveying and mapping scale that meets the accuracy requirements.

4) The minimum size of the measured geological body is generally 2mm on the corresponding map. It is particularly important that it can be unfolded if it is less than 2mm, but the actual data must be indicated. The error between geological points and geological boundaries on the map should not exceed 2mm.

5) Before surveying and mapping, the stratum profile should be measured, the stratum lithology histogram should be established, and the surveying and mapping unit should be determined.

6) Surveying and mapping adopts the combination of crossing and recourse. Important boundaries should be pursued. Covered areas should be exposed manually.

7) The layout of observation points should be clear in purpose, reasonable in density, and have enough points to control the collapse boundary, geological structure and cracks. The types of observation points are divided into: lithologic points, geomorphological points, geological structural points, fracture statistics points, hydrogeological points, external dynamic geological phenomena points, fracture investigation points, wall collapse investigation points, collapse deformation points, disaster investigation statistics points, human engineering activities investigation points, sampling points, testing points, long-term observation points, monitoring points and so on.

8) Measurement requirements of observation points: When the surveying and mapping scale is less than 1∶5000, visual inspection and compass intersection method are used for positioning, and the elevation can be estimated according to topographic map and barometer. When the surveying and mapping scale is 1∶5000, it must be measured by instruments. Important observation points, exploration points and monitoring points, regardless of scale, must be measured by instruments.

9) Field record requirements: ① Record observation points with special cards, and the classification system number is consistent with the position number; (2) Records must be consistent with the site sketch; ③ The description should be comprehensive and focused; ④ Describe and record the route between points.

10) to collect representative geotechnical samples and water samples for identification and laboratory tests.

1 1) In the process of surveying and mapping, we should always proofread the original data, analyze it in time, compile various analysis charts in time, sort out and summarize the data in time, find and solve problems in time, and guide the next step.

12) After the surveying and mapping work is finished and the original data are sorted out, organize the field acceptance. On the basis of comprehensive and systematic data sorting and preliminary analysis, the following original results should be put forward: ① actual material map; ② Sketch of field geology; ③ Measured stratum histogram; ④ Measured stratum profile; (5) Observation point record card; 6. Records and sketches of mountain projects; All landowners long-term observation records and monitoring records; (8) List of geotechnical and water sample test results; Pet-name ruby album; Attending the text summary; ? Information based on data.

2. Surveying and mapping content

1) engineering geological mapping of rock mass: find out the geological age, genetic type, lithology and contact relationship of rock mass.

2) Soil engineering geological mapping: find out the grain size composition, mineral composition, compactness or consistency, porosity, soil structure, genetic type and geological age of soil.

3) Geomorphology and slope structure investigation: ① Microgeomorphology investigation, including watershed, ridge, slope, valley shoulder, slope toe, cliff, valley, river valley, floodplain, terrace, denuded surface, karst micromorphology, collapse landform and artificial landform. Investigate and describe the morphological characteristics (area, length, width, elevation, height difference, depth, slope, physical characteristics and their changes) of each geomorphic unit, the combination characteristics, transition relationship and relative age of micro-geomorphology; (2) Focus on investigating the geomorphic units produced by the collapse body, focusing on investigating the valley landforms and slope landforms, and finding out the structural types and slope characteristics of the slope; ③ Analyze the relationship between karst landform, flowing water landform and collapse; ④ Investigate the relationship between artificial landforms (stope, reservoir dam, road, artificial slope, etc.). ) and collapsed.

4) Geological structure investigation: find out the structural outline and characteristics of the investigation area, and investigate the position, occurrence, scale, mechanical properties of folds, faults and joints and their relationship with collapse.

5) Neotectonic movement and earthquake investigation: mainly collecting data.

6) Hydrogeological investigation: investigate the position, scope and dynamic relationship between surface water and groundwater, the recharge, diameter and discharge conditions of groundwater, the position, outflow characteristics and dynamic changes of groundwater outcrop, etc. On this basis, the influence of surface water and groundwater on collapse is comprehensively analyzed.

7) Investigation of human activities: Investigate the present situation and planning of human engineering activities, adverse geological phenomena or geological disasters induced by human activities.

8) Investigation of subsidence area: ① Find out the geological structure of subsidence area, including stratum lithology, landform, geological structure, geotechnical structure type, slope fabric type and its control and influence on the formation of subsidence. Geotechnical structures should focus on recording weak interlayers, faults, folds, cracks, cracks, karst, goaf, goaf, lateral boundary and bottom boundary; (2) Find out the hydrogeological characteristics of the subsidence area, including the infiltration and runoff of surface water, the quantity, quality and erosivity of groundwater in the subsidence body; ③ Migration and accumulation of early collapse; (4) Possible migration and accumulation under future collapse and disaster conditions; ⑤ Possible disaster types (such as debris flow, landslide, surge, etc.). ), the scale, scope and pre-assessment of this collapse disaster.

9) Investigation of environmental geological bodies: Investigate the stability of foreign bodies in subsidence areas, and provide basis for the selection of bearing stratum for prevention and control projects.

10) investigation of disaster-prone factors: investigate the intensity and period of disaster-prone factors (such as rainfall, surface water erosion, groundwater activity, artificial blasting, underground mining, channel leakage, etc.). ) is related to the formation of collapse.

(3) Geophysical exploration

Geophysical prospecting technical requirements shall be implemented according to the current professional standards, and the main geophysical profiles shall be consistent with the engineering geological profiles.

(4) Drilling

1. Basic requirements

1) Drilling design (including drilling purpose, type, depth, structure and drilling technology) shall be prepared.

2) The drilling depth should pass through the bottom boundary of the collapse body. Enter the stable rock (soil) for 3m (soil) to 5m (rock mass).

3) The aperture should meet the requirements of coring and testing.

4) Simple hydrogeological observation should be carried out.

5) After drilling, the hole should be sealed as required and the core should be kept.

2. Drilling geological records

This is the most basic first-hand achievement data, which should be recorded in time at the scene; Attention should be paid to the distribution of remaining cores and the calculation of core recovery rate; A unified table should be used for borehole geological logging.

1) core description: hard rock stratum, which should describe the name, color, composition, structure, joints and cracks, weathering and crushing degree, core length and integrity, etc. The gravel layer shall describe its name, color, lithology, composition, size, shape, filler content and cementation; For sandy soil layer, its name, color, composition, particle size, dry and wet state, inclusion, etc. It should be explained; Clayey soil should describe its name, color, composition, structural characteristics, plasticity, consistency, etc.

2) Description of joints and cracks: determine the types, causes, continuity, opening, fillings and crushing rate of joints and cracks; Fault description: fault nature, width (depth) of fracture zone, scratches, structural rocks, core integrity, water leakage, water inrush, etc.

Attention should be paid to the description of karst, fracture, slip zone and weak interlayer, geological records, hydrogeological observation records, drilling anomaly records and sampling records.

3. Drilling results

After the hole is finally formed, the drilling results should be sorted out and submitted in time, including drilling design, drilling histogram, core sketch, core photo, simple hydrogeological observation record, sample table, drilling report, etc.

The scale of borehole histogram is generally 1: 100 to 1: 200, whichever can clearly represent the main geological phenomena. The contents, styles and labels of drawings shall conform to the corresponding specifications.

4. Main problems solved by drilling methods

1) Find out the lithology, geological structure, geotechnical structure, weathering zone, karst, boundary conditions, morphological characteristics and scale of the collapsed body.

2) Find out the hydrogeological conditions in the subsidence area and take groundwater samples.

3) Detect the depth, development characteristics, filling conditions, water filling conditions and connectivity of concealed cracks and surface cracks.

4) Take indoor test samples of geotechnical physics and mechanics, and carry out hydrogeological field tests (water pressing, pumping, water injection, diffusion test, etc.). ) and long-term observation, determine the hydrogeological parameters, and verify the position and characteristics of the landslide zone.

5) Carry out geophysical comprehensive logging and cross-well logging to expand the detection range.

6) Long-term monitoring of collapse deformation and deformation monitoring during construction.

(5) Mountain engineering

1. Problems solved by mountain engineering

1) exploration pit: the depth is less than 3m. Used for stripping floating soil, exposing bedrock, understanding rocks and weathering, or for load test and permeability test.

2) Trench: the depth is generally less than 3m. It is used for stripping floating soil and revealing bedrock, and is mostly arranged perpendicular to the strike of rock stratum. It is used to track the boundaries of structural lines, faults and landslides, and to understand the thickness and lithology of residues.

3) Shallow wells and shafts: the depth of shallow wells is less than 15m, and the depth of shafts is greater than 15m. It is used to explore the division of weathered rock mass, the structure of rock and soil mass, weak interlayer, cracks and caves. And carry out in-situ testing and deformation monitoring.

4) Flat-inclined adit: The general section is 1.8m×2m, which is suitable for sections with large dip angle and slope. It is used to detect formation lithology, rock mass structure, faults, cracks and caves. It is also used for sampling, field in-situ testing and field monitoring.

5) Roadway and stone gate: the nearly horizontal roadway connected with the shaft has no direct ground exit and is not commonly used.

2. Mountain engineering geological work

(1) Geological Directory

1) reveals the name, color, lithology, structure, structure, bedding characteristics, thickness, contact relationship, geological age, genetic type and occurrence of rock and soil. The weak interlayer should be enlarged and drawn, and its ductility and stability should be paid attention to.

2) The weathering characteristics of rocks and the division of weathering unloading zones, as well as the relationship between weathering and cracks.

3) Faults: occurrence, scale, fault distance, fault shape and distribution characteristics, fault width, tectonic rocks, lithology on both sides, fault properties, etc.

4) Cracks and fissures: describe the cracks and joints with good permeability one by one, and record their properties, wall characteristics, causes, crack opening and closing, filling, connectivity, mutual cutting relationship, dislocation deformation and water leakage.

5) Landslide zone and gravity deformation zone are the focus of the description, and they are enlarged. It is necessary to describe its thickness, lithology, material composition, structural rock, occurrence and water content.

6) Hydrogeological phenomena: Pay attention to dripping point, water gushing point, water seepage point, connected test water outlet point and temporary water outlet point. Pay attention to its location, water quantity, the relationship with cracks, fissures, karst and old caves, and the relationship between water quantity and rainfall.

7) Record the positions, functions, horizons, lithology and related geological conditions of various testing points, geophysical prospecting points, long-term viewpoints, sampling points, photographing points and monitoring points.

(2) Relevant regulations of geological sketch.

1) The scale is generally1:20 ~1:100.

2) Sketch the ditch to draw the wall and bottom display. If the geological phenomena of the two walls are different, draw a sketch of the two walls. The length of the trough bottom can be projected horizontally, the trough wall can be drawn according to the actual length and slope, and the parallel expansion method of the wall bottom can also be adopted.

3) Schematic diagram of shallow wells and shafts. A presentation diagram generally consists of two adjacent walls, which are unfolded in parallel, indicating the orientation of the walls. The circular well display is divided into 90 equal parts and two adjacent walls are drawn in parallel. Inclined shaft display should show its inclination.

4) Draw the ceiling and two walls with the adit schematic diagram. The extended format is based on the ceiling of the cave and two walls raised from the top. When the direction of the hole changes, it is necessary to indicate the turning direction, and the top of the hole is drawn continuously. When the two walls turn, the protruding side is triangular, tearing the fork. The calculation of hole depth is mainly based on the center line of hole top. The slope of the ceiling is generally expressed by the height difference curve.

5) Cataloging during excavation: record the cracks, slip zone, water outlet, water volume, roof and floor deformation and other phenomena encountered during excavation in time. Generally draw a sketch of the working face every 5 meters. Sketching, photographing, video recording, sampling and embedding monitoring instruments should be carried out in time for the unstable surrounding rock and the areas that must be supported.

(3) Sampling and in-situ testing

According to the relevant regulations and design requirements, the geological sketch and specimen sketch are carried out in the in-situ test adit section as required.

(4) Video recording

Conditional processing of heavy mountain engineering video. The orientation and main geological contents should be recorded during video recording.

3. Achievements submitted by mountain engineering

Geological sketches, construction records of important sections, photo albums, videos, sample sheets, various point records, exploration summary of heavy mountain projects, etc.

(6) Testing

The purpose is to find out the collapse geological body and its occurrence environment, and provide necessary geotechnical physical and mechanical parameters and hydrogeological parameters for stability evaluation, model test, simulation test and prevention engineering design.

1. Arrangement principle of testing work

1) The identification of geotechnical composition and the testing of basic physical properties and hydraulic properties should take lithologic layers or engineering geological groups and sections as basic units, and each unit should take 3 ~ 5 groups.

2) The focus of the test should be on the landslide zone. The mechanical properties of the landslide zone are uneven, so the main weak surface (the weakest surface) should be tested emphatically. It is necessary to control the landslide zone on the surface. The number of mechanical indicators participating in statistics should not be less than 6.

3) The experimental work should be closely combined with other work, and other means should be fully utilized for sampling and testing. For example, standard penetration test, pressuremeter test, deep sampling and hydrogeological test can make full use of drilling; Surface sampling and in-situ testing can make full use of mountain engineering.

4) The layout of test work should be combined indoor and on-site. On-site testing is expensive and limited, so it is not appropriate to invest too much. Reasonable arrangements should be made according to the work stage and actual needs.

5) For the rock and soil in the bearing stratum of the preliminary selected prevention and control project, the test items can be selected according to the type, load, stress mode and possible deformation form of the prevention and control project. Such as evaluating the anti-sliding stability of bearing stratum, tensile stability of rock mass, bearing capacity of foundation, anti-sliding property, etc.

2. Test contents and methods

The object, content and method of the test depend on the working stage and its accuracy requirements.

1) Preliminary exploration stage: For the collapsed and dangerous rock mass, the test should be able to evaluate its deformation and failure characteristics and stability calculation. For related environmental rock mass (surrounding rock mass, geological mass affected by collapse and displacement, supporting rock mass of prevention and control project, other disaster rock mass that may endanger the collapse body, etc.). ), the test mainly focuses on qualitative evaluation to meet its stability and environmental geological problems. This stage is mainly based on data collection and laboratory testing.

2) Pre-feasibility stage: test, analyze and calculate the stability of the collapsed dangerous rock mass. Brief tests such as stability evaluation should be carried out on related environmental rock masses. Simple tests required for qualitative or semi-quantitative analysis and evaluation of bearing rock mass. Methods Field test was the main method, and corresponding indoor test was carried out at the same time.

3) Feasibility study stage: The collapse body should be tested in detail to provide the required parameters for deformation analysis, stability calculation, model test and simulation test. In order to meet the needs of qualitative evaluation of stability and qualitative study of environmental geological problems, a brief test was carried out on related environmental rock masses. Some tests are carried out on the bearing rock mass, which provide the required parameters for stability calculation and prevention engineering scheme design. The test methods are mainly field test and corresponding indoor test.

3. Selection of test items

The necessary test items should be selected according to the analysis of the collapse instability mechanism and the mechanical mechanism of deformation and failure.

1) The test items of landslide are: ① geotechnical composition, physical properties and hydraulic properties; ② elastic wave velocity; ③ Weak plane shear strength; ④ Hydrogeological test.

2) Dumping and collapse test items include: ① geotechnical composition, physical properties and hydraulic properties; ② elastic wave velocity; ③ the tensile strength of the weak surface at the bottom; ④ Friction strength of rock surface between rock blocks; ⑤ Tensile strength of rock mass.

3) The collapse test items include: ① the composition and physical properties of rock and soil; ② Tensile strength.

4) The swelling and collapse test items include: ① rock composition, physical properties and hydraulic properties; ② elastic wave velocity; ③ Unconfined compressive strength of weak layer at the bottom.

5) The test items of staggered collapse include: ① rock composition, physical properties and hydraulic properties; ② elastic wave velocity; ③ Shear strength of rock and soil at the bottom.

4. Selection of test methods and test conditions

Appropriate test methods and conditions should be selected according to the characteristics and occurrence environment of collapsed rock and soil.

1) The indoor permeability test is suitable for sandy soil and cohesive soil. Field test should be considered for mixed soil and macadam soil.

2) Indoor compression test is applicable to silt and cohesive soil, and field test should be selected for other soil types.

3) Indoor direct shear test is applicable to cohesive soil and sandy soil (gravels and stones larger than 2mm should be selected from the sample). The field test should be considered for breccia-like sliding zone soil or mixed graded clastic sliding zone soil.

4) When there are many particles with particle size larger than 10mm in the soil sample, it is not suitable to do indoor triaxial shear test. It is appropriate to choose field test.

5) Sandy soil, cohesive soil and loess should be tested by static cone penetration test.

6) For the foundation soil selected for shallow-buried prevention and control project, compression test of bearing plate can be adopted; For deep foundation soil (5 ~ 15m), spiral plate load test or pressuremeter test should be adopted.

7) Borehole water pressure test cannot be used for soil collapse; When there is a certain water level and water quantity in the collapse body, water lifting test or appropriate pumping test can be carried out; When there is no water or slight water in the collapse body, the controlled borehole water injection test or surface infiltration test can be adopted when the stability conditions permit.

8) It is extremely difficult to carry out field test in rock mass, so the selection should be based on elastic wave observation and indoor test.

9) Weathered rock mass and weak rock and soil can be used for pressuremeter test before drilling.

10) The dangerous rock mass without weak connectivity surface shall be subjected to on-site direct shear test; In-situ direct shear test should be carried out for dangerous rock mass sliding along a weak surface.

1 1) Reservoir-type rockfall-dangerous rock mass, when the rock mass cracks develop, it is considered that the high water level of the reservoir has submerged some dangerous rock mass, and pumping test or drilling water pressure test can be carried out. Before water pressure test, it is necessary to demonstrate whether it affects the stability of dangerous rock mass.

12) It is very dangerous and harmful to carry out water filling test and connectivity test for water injection into cracks of fractured rock and soil quickly by hand, and it can't be carried out under any circumstances.

5. Analysis and application of test results

The unit undertaking the test shall submit a comprehensive test report on the collapsed geological body, including: ① the determination and basis of the test object, test scheme and test items; ② Test requirements and relevant specifications; ③ Test technology and process (test overview, specimen preparation, specimen quantity and characteristics, test instruments, test procedures and results arrangement); ④ Test results and comprehensive analysis; ⑤ Suggested values of test results.

The test results can only be used as a reference for stability calculation and prevention engineering design. The values of calculation parameters and design parameters should be determined on the basis of back analysis and other analysis, combined with test results, model tests, simulation tests and expert experience.

(7) Dynamic monitoring

1. The purpose and task of dynamic monitoring

1) The purpose of dynamic monitoring is: ① to evaluate the activity and stability of geological disasters; (2) Monitoring the distribution, scale, displacement mode, direction and speed of landslide deformation blocks, providing services for analyzing landslide deformation characteristics and deformation mechanism, and providing important basis for prevention and control engineering design; (3) Provide early warning and forecast for the safety of exploration and construction, feed back the collapse disturbance caused by the construction of heavy mountain projects in time, control the exploration and construction site and intensity, and provide reference for the design of prevention and control projects; ④ To lay a good foundation for the long-term monitoring of the station in the future.

2) Tasks of dynamic monitoring: ① Find out the main blocks, main parts, main failure modes, main deformation directions and deformation rates of the collapsed body; (2) Further understand the physical characteristics of landslide, analyze its deformation law, development trend and formation mechanism, analyze and evaluate the stability of landslide, and demonstrate the design of prevention and control project; ③ Monitor the disaster-causing factors related to collapse (such as rainfall, surface water, groundwater and human activities). ) and its strength, and its influence on collapse stability is analyzed and evaluated.

2. Contents and methods of dynamic monitoring

(1) absolute displacement monitoring

1) monitoring content: carry out three-dimensional coordinate monitoring on the measuring point of the collapsed body, and obtain the three-dimensional deformation and displacement amount, displacement mode and displacement rate of the measuring point.

2) Monitoring methods: geodetic survey, GPS survey, close-range photogrammetry, laser holography and laser speckle method.

(2) Relative displacement monitoring

1) Monitoring content: Relative displacement monitoring is a commonly used deformation monitoring method, which is used to measure relative displacement changes (opening, closing, sinking, lifting and dislocation, etc. ) between the points of the key deformation parts of the landslide. It is mainly used to monitor the roof and floor of cracks, landslide zones and mined-out areas, and is the main content of collapse monitoring.

2) Monitoring method: simple monitoring method (stake or buried stake, steel rule direct measurement, etc. ), mechanical monitoring method (using mechanical instruments to monitor the displacement or settlement of cracks, sliding zones and roof and floor) and electrical monitoring method (commonly used inductive frequency modulation displacement meter monitoring).

(3) Tilt monitoring

Ground inclination monitoring: the monitoring content is the change of slope direction and slope angle of landslide ground. Monitoring instruments include disc inclinometer, rod inclinometer and T inclinometer.

Deep inclination monitoring: use borehole inclinometer to measure the inclination deformation of borehole in landslide body, and get the horizontal displacement of each hole section.

(4) Acoustic emission monitoring

1) monitoring content: detect the acoustic emission signals generated when the rock mass breaks, so as to judge the deformation and stability of the rock mass and make predictions.

2) Monitoring method: Imported or domestic acoustic emission instruments and detectors are used for monitoring.

(5) In-situ stress observation

1) observation content: measure the change of in-situ stress in landslide, distinguish tensile zone, pressure zone and pressure change, and infer rock mass deformation.

2) Monitoring method: commonly used instruments such as WL-60 stress gauge and YJ-73 triaxial piezomagnetic stress gauge are monitored.

(6) Groundwater monitoring

1) monitoring content: long-term monitoring of water level, water quantity, water temperature and water quality of groundwater outcrops in the survey area. Grasp the variation law of groundwater in the area, analyze the relationship between groundwater and surface water and atmospheric precipitation, and analyze the correlation between groundwater dynamic characteristics and collapse deformation, so as to provide hydrogeological data for stability evaluation and prevention engineering design.

2) Monitoring method: Using monitoring bed, automatic water level recorder, pore water pressure gauge, borehole osmometer, flowmeter, water temperature gauge, flow measuring weir and sampling, groundwater outcrops such as springs, wells, pits, boreholes, flat holes and vertical shafts are monitored.

3) Scope of application: When the deformation and damage of the collapse are related to groundwater, and groundwater exists in the collapse in rainy season or when the surface water level rises, it should be monitored.

(7) Surface water monitoring

1) monitoring content: monitoring the water level, velocity and discharge of ditches, streams and rivers related to collapse, and analyzing the relationship between them and groundwater and rainfall.

2) Monitoring method: Water level gauge, automatic water level recorder and flow weir are used for monitoring.

(8) Conventional meteorological monitoring

1) monitoring contents and instruments: the conventional meteorological monitoring instruments (thermometer, rain gauge, evaporator, etc.) are used to carry out meteorological monitoring mainly based on rainfall. ).

2) Scope of application: Generally, it needs meteorological monitoring and groundwater monitoring.

(9) Earthquake monitoring

1) monitoring content: seismic force is one of the special loads acting on the collapsed body and plays an important role in the stability of the collapsed body. Seismographs and other instruments should be used to monitor the intensity, occurrence time, epicenter location and focal depth of earthquakes in this area and its surrounding areas, analyze the earthquake intensity in this area, and evaluate the influence of earthquake action on the stability of collapsed bodies.

2) Scope of application: It is applicable to all collapse investigation and evaluation. According to the present situation of earthquake monitoring in China, it is not appropriate to set up stations for monitoring, but to collect seismic data.

(10) personnel activity monitoring

The relationship between the scope, strength, speed and collapse deformation of the projects that have an impact on the collapse in the investigation area should be monitored.