Soil and stone grade grading method based on surface wave apparent velocity

Abstract

The invention discloses a surface wave apparent velocity-based soil and stone grade grading method, which comprises the following steps of: acquiring the seismic surface wave velocity of an area to be surveyed, analyzing the acquired seismic surface wave velocity data, and combining the corresponding relationship between the surface wave velocity value and the soil and stone grade to obtain the corresponding soil and stone grade. According to the method, an ultra-shallow seismic surface wave exploration technology is adopted, the compactness and the wave velocity of a rock-soil body have linear correlation, soil and stone grades are divided through the seismic surface wave velocity, data collected on site are processed and then imported into a digital exploration platform of a company, the purpose of digital exploration of line geology is achieved, and a foundation is laid for designing required engineering geological data. The purpose of improving quality and efficiency of line geological exploration is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of storage and transportation pipeline construction, and particularly relates to a soil and rock grade classification method based on surface wave apparent velocity. BACKGROUND

[0002] In recent years, oil and gas pipeline construction has reached a historical peak, pipeline construction scale is getting larger and larger, pipeline construction length is getting longer and longer, the topography units along the pipeline are more and more, the engineering geological problems and geological conditions encountered are more and more complex, and the requirements for pipeline route geotechnical engineering investigation are higher and higher. Due to various reasons, in recent years, during the pipeline route construction, the construction party often feedbacks that the soil and rock grade provided by the pipeline route geological investigation is inaccurate, and there is a large deviation from the actual excavation, which leads to the change of excavation mode, causes the loss of construction cost and construction period, and causes the complaints and claims of the construction party. Therefore, how to accurately divide the soil and rock grade of the pipeline along the route and provide reliable route geological investigation results is one of the main problems that pipeline investigation units should solve, and has important practical significance.

[0003] At present, the common pipeline route geological soil and rock classification methods in China mainly include manual spoon drilling, manual exploration well and core drilling, and the like. The site labor intensity is large, the operation efficiency is low, the investigation cost is high, the informatization level is low, the manual exploration well still has the risk of hole collapse, and there is a large gap with pipeline digital investigation. According to statistics, the operation efficiency analysis of common route exploration points is shown in Table 1.

[0004] Table 1 Operation efficiency analysis of common route exploration points

[0005]

[0006] From the above table, it can be seen that the current route geological investigation means is single, still stays in the traditional investigation means, the horizontal means is low, the site operation labor intensity is large, the efficiency is relatively low, and there is a lack of information digital means. Therefore, seeking a method capable of effectively improving the investigation efficiency, reducing the labor intensity and saving the investigation cost becomes a technical problem to be solved by the technical personnel in the field.

[0007] Therefore, the prior art still needs to be improved. SUMMARY

[0008] To solve the above technical problems, the present application provides a soil and rock grade classification method based on surface wave apparent velocity, so as to solve the problems of low route geological investigation efficiency and high cost in the prior art.

[0009] To solve the above technical problems, some embodiments of the present application disclose a soil and rock grade grading method based on surface wave apparent velocity, collecting seismic surface wave velocity of a region to be surveyed, analyzing the collected seismic surface wave velocity data, and obtaining corresponding soil and rock grades in combination with the corresponding relationship between surface wave velocity values and soil and rock grades.

[0010] In some embodiments, the collecting of the seismic surface wave velocity of the region to be surveyed comprises:

[0011] The shallow seismic refraction wave method is adopted to collect surface wave data at endpoints on both sides of a seismic arrangement and at a predetermined offset distance from a line exploration point as the center, so as to obtain seismic surface wave data at each coordinate.

[0012] In some embodiments, the seismic surface wave data at each coordinate is transient surface wave data.

[0013] In some embodiments, the analysis of the collected seismic surface wave velocity data is based on the linear correlation between the density of a rock-soil body and the seismic surface wave velocity.

[0014] In some embodiments, the analysis of the collected seismic surface wave velocity data comprises: frequency dispersion curve extraction and cross-spectrum analysis of the collected seismic surface wave data, and providing layer thickness and layer surface wave apparent velocity values for a line exploration point.

[0015] In some embodiments, the corresponding relationship between the surface wave velocity values and the soil and rock grades comprises:

[0016] The corresponding relationship between the surface wave apparent velocity values and the soil and rock grades is established according to the properties of the rock-soil body, and the soil and rock grades are classified.

[0017] In some embodiments, the properties of the rock-soil body comprise rock-soil body density, rock natural uniaxial compressive strength, and SPT (Standard Penetration Test) number.

[0018] In some embodiments, the analysis of the collected seismic surface wave velocity data comprises:

[0019] The obtained seismic surface wave velocity data is subjected to digital filtering processing and parameter rearrangement to obtain effective seismic surface wave data;

[0020] The effective seismic surface wave data is subjected to frequency dispersion curve extraction;

[0021] Model inversion and model iteration are performed based on the frequency dispersion curve;

[0022] Surface wave apparent velocity result maps of each exploration point are obtained based on the model inversion and model iteration.

[0023] In some embodiments, the surface wave apparent velocity result maps comprise offset distance, layer bottom depth, and surface wave apparent velocity values.

[0024] In some embodiments, the correspondence between the surface wave velocity value and the soil-rock grade comprises:

[0025] the surface wave apparent velocity is not greater than 150 m / s, and the soil-rock grade is grade one;

[0026] the surface wave apparent velocity is greater than 150 m / s and not greater than 250 m / s, and the soil-rock grade is grade two;

[0027] the surface wave apparent velocity is greater than 250 m / s and not greater than 350 m / s, and the soil-rock grade is grade three;

[0028] the surface wave apparent velocity is greater than 350 m / s and not greater than 450 m / s, and the soil-rock grade is grade four;

[0029] the surface wave apparent velocity is greater than 450 m / s and not greater than 550 m / s, and the soil-rock grade is grade five;

[0030] the surface wave apparent velocity is greater than 550 m / s and not greater than 900 m / s, and the soil-rock grade is grade six;

[0031] the surface wave apparent velocity is greater than 900 m / s and not greater than 1200 m / s, and the soil-rock grade is grade seven;

[0032] the surface wave apparent velocity is greater than 1200 m / s and not greater than 1500 m / s, and the soil-rock grade is grade eight;

[0033] the surface wave apparent velocity is greater than 1500 m / s and not greater than 2000 m / s, and the soil-rock grade is grade nine;

[0034] the surface wave apparent velocity is greater than 2000 m / s and not greater than 2500 m / s, and the soil-rock grade is grade ten;

[0035] the surface wave apparent velocity is greater than 2500 m / s, and the soil-rock grade is more than grade ten.

[0036] By adopting the technical scheme, the present application has at least the following beneficial effects:

[0037] The soil-rock grading method based on the surface wave apparent velocity provided by the present application adopts the super-shallow seismic surface wave survey technology, utilizes the linear correlation between the compactness of the rock-soil body and the wave speed, divides the soil-rock grade through the seismic surface wave speed, and imports the data collected on site after processing into the digitalized survey platform of the company, so as to realize the digitalized survey target of the line geology, provide the engineering geological data required by the design, and realize the quality improvement and efficiency increase of the line geological survey. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0039] Figure 1 A portable line geological exploration instrument structure principle block diagram of a soil and rock grade grading method based on surface wave apparent velocity disclosed by some embodiments of the present application;

[0040] Figure 2 A surface wave data processing flowchart of a soil and rock grade grading method based on surface wave apparent velocity disclosed by some embodiments of the present application;

[0041] Figure 3 A surface wave apparent velocity achievement map of test point 1 (ZK5 hole) of a soil and rock grade grading method based on surface wave apparent velocity disclosed by some embodiments of the present application;

[0042] Figure 4 A core photo of test point 1 (ZK5) of a soil and rock grade grading method based on surface wave apparent velocity disclosed by some embodiments of the present application. DETAILED DESCRIPTION

[0043] The embodiments of the present application will be further described in detail below with reference to the drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, and the present application can be implemented in many different forms, and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0044] The present application provides these embodiments in order to make the present application thorough and complete, and fully express the scope of the present application to those skilled in the art. It should be noted that: unless otherwise specified, the relative arrangement of components and steps, the composition of materials, numerical expressions and values set forth in these embodiments should be interpreted as merely exemplary, and not as a limitation.

[0045] It should be noted that, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is greater than or equal to two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like are merely for the purpose of facilitating the description of the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0046] In addition, the "first", "second" and similar words used in the present disclosure do not represent any order, quantity or importance, but are only used to distinguish different parts. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error. "Include" or "contain" and similar words mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements.

[0047] It should also be noted that in the description of the present disclosure, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances. When it is described that a specific device is located between the first device and the second device, there can be or can not be an intermediate device between the specific device and the first device or the second device.

[0048] All terms used in the present disclosure have the same meaning as understood by those skilled in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted to have meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or excessively formalized sense, unless specifically defined here.

[0049] Techniques, methods and equipment known to those skilled in the relevant art can not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the specification.

[0050] Some embodiments of the present application disclose a soil and rock grade grading method based on surface wave apparent velocity, which adopts ultra-shallow layer seismic surface wave prospecting technology to establish the corresponding relationship between surface wave velocity value and soil and rock grade (excavatability), infer and divide the soil and rock grade, solve the stratification and soil and rock grade classification problems in pipeline route geological survey, and at the same time realize pipeline along the line soil resistivity test, underground water level detection and seismic liquefaction discrimination, realize pipeline route geological survey digitization, save manpower and material resources, and improve pipeline route survey efficiency.

[0051] Research shows that the elastic wave velocity of rock-soil mass has a good corresponding relationship with the high and low of the soil and rock excavation grade of rock-soil mass. The larger the elastic wave velocity of rock-soil mass, the higher the soil and rock excavation grade. Conversely, the smaller the elastic wave velocity, the lower the excavation grade. Therefore, according to the size of the elastic wave velocity of rock-soil mass, the soil and rock grade is divided, which has the characteristics of high efficiency and accuracy.

[0052] Some embodiments of the present application disclose a soil and rock grade grading method based on surface wave apparent velocity, and specific schemes are as follows:

[0053] Step one, adopt the digital light portable line geological exploration instrument as shown in the figure to collect transient multi-channel surface wave, the observation mode adopts the encounter pursuit mode of shallow seismic refraction wave method, the surface wave data is collected at the endpoints on both sides of the seismic arrangement and the 2.5m offset distance, at least 4 seismic surface wave data are collected at each place, the midpoint in the arrangement corresponds to the line exploration point, and the coordinates of the point are recorded. Figure 1

[0054] Step two, adopt the data processing software to perform frequency dispersion curve extraction, cross spectrum analysis and the like on the surface wave data, and provide the layering thickness h and the layering surface wave apparent velocity value Vs for the exploration point by using the surface wave dispersion characteristics.

[0055] Step three, establish the corresponding relationship between the surface wave apparent velocity value and the soil and rock grade (excavatability) according to the rock mass density, the rock natural uniaxial compressive strength, the standard penetration (dynamic sounding) number of blows and the like, and perform the layering soil and rock grade classification.

[0056] Compared with the current method of adopting the soil name, the firmness coefficient, the density, the rock natural uniaxial compressive strength, the excavation method and the like, the soil and rock grade grading method based on the surface wave apparent velocity has the characteristics of in-situ testing, non-excavation, no need for indoor testing and the like, can realize the rapid division of the soil and rock grade on site, saves the drilling, coring and indoor testing costs, can improve the on-site operation efficiency, and has important engineering significance.

[0057] The transient surface wave method adopted in the present application fully utilizes the collected surface wave method urban exploration results, combines the oil and gas pipeline line geological survey characteristics, and adopts the digital light portable line geological exploration instrument suitable for pipeline line geological survey. Figure 1 The principle block diagram of the complete instrument is as shown in the figure, the block is a 16-channel geophone array and cable, a host computer and an upper computer (IPad) constitute a surface wave exploration instrument, the geophone channel spacing is 0.5m, the source excitation point is away from the first geophone, that is, the offset distance is adjustable, the peak value triggering mode of the geophone at the source is adopted to realize the collection synchronization; during the field surface wave exploration, the surface wave is excited at different offset distances on both sides of the arrangement by artificial, and the 16-channel geophone is triggered by the geophone at the source to synchronously collect the underground surface wave signal.

[0058] In order to analyze the collected seismic surface wave velocity data, the surface wave post-processing software is adopted, and the data processing flow is as shown in the figure. Figure 2 The C# language can be used to realize the reading, display, preprocessing, frequency dispersion curve extraction, model inversion, profile mapping and the like of the standard format seismic data (for example,.sgy / .sg2).

[0059] ​According to the rock-soil compactness, the rock natural uniaxial compressive strength, the standard penetration (dynamic sounding) number, etc., the application establishes the corresponding relationship between the surface wave apparent velocity value and the soil-rock grade (excavatability), and performs layered soil-rock grade classification, and the details are shown in Table 3.

[0060] Table 3 Soil-rock grade and classification of rock-soil surface wave apparent velocity

[0061]

[0062]

[0063] Example 1

[0064] Taking the rock-soil engineering investigation of a certain distribution cleaning station as an example, the comparative analysis of the exploration benefits of the domestic conventional soil-rock grading method (drilling method) and the transient surface wave method is shown in Table 2:

[0065] Table 2 Comparison table of surface wave method and core drilling method

[0066]

[0067] Compared with the conventional pipeline route geological investigation means, the transient surface wave method used in the embodiment saves about 10 hours of field operation time, about 1 hour of indoor processing time, and about 3000 yuan of single-point investigation cost. For long oil and gas pipeline route geological investigation business, according to the latest pipeline DEC standard, a route exploration point is arranged every 200-300 m, and about 15,000 yuan is saved per kilometer. It can be seen that the soil-rock grade classification method based on the surface wave apparent velocity disclosed in the application has high practical value and broad application prospect in the field of long oil and gas pipeline route geological investigation. The application can fill the gap in the conventional engineering geophysical investigation means for soil-rock grade classification in the long oil and gas pipeline route geological investigation, accumulate new methods and experience for investigation technology, save route exploration cost, improve engineering investigation efficiency, greatly shorten the investigation period, and meet the needs of the company for quality improvement and efficiency increase.

[0068] Example 2

[0069] The digital light portable route geological exploration instrument is used to arrange 3 exploration points in a project, and the stratum resolution ability and soil-rock classification accuracy of the instrument are verified by comparing with the drilling data and laboratory results.

[0070] According to the collected rock-soil engineering investigation report of a certain distribution cleaning station, representative ZK1, ZK5 and ZK6 holes are selected for surface wave layered resolution comparison. For each borehole, 4 surface wave data are collected at offset distances of -10 m, -7.5 m, 0 m and 2.5 m, respectively, and the test result analysis is shown in Table 4. Figure 3 The test point 1 (ZK5 hole) apparent shear wave velocity values at each offset distance are shown in Table 4.

[0071] Table 4 Test point 1 (ZK5 hole) each offset apparent S-wave velocity value

[0072]

[0073] From Figure 3 the seismic surface wave apparent velocity result map and the apparent S-wave velocity value of each offset in Table 4, the soil-rock interface of each seismic surface wave point is as follows:

[0074] 1) Offset = -10.0 m: soil-rock interface 5.2 m, strong weathered diorite surface wave apparent velocity 617.3 m / s, effective exploration depth 20.83 m;

[0075] 2) Offset = -7.5 m: soil-rock interface 5.1 m, strong weathered diorite surface wave apparent velocity 667.8 m / s, effective exploration depth 19.42 m;

[0076] 3) Offset = 0 m: soil-rock interface 5.3 m, strong weathered diorite surface wave apparent velocity 777.6 m / s, effective exploration depth 22.76 m;

[0077] 4) Offset = 2.5 m: soil-rock interface 5.4 m, strong weathered diorite surface wave apparent velocity 675.5 m / s, effective exploration depth 18.36 m.

[0078] According to the geotechnical engineering investigation report of the distribution cleaning station, the strata exposed by the ZK5 hole drilling are as follows:

[0079] The first layer of pebbles (Q4al+pl): brownish yellow, saturated, slightly dense to dense, content about 60%, general particle size 10-60 mm, maximum particle size 100 mm, parent rock composition mainly diorite, strong weathering, general roundness, mostly rounded and sub-angular, the rest filled with sandy soil, soil unevenly distributed. This layer is distributed in the whole field area, and the exposed layer thickness in the ZK5 hole is 5.60 m, the soil-rock grade is III grade, and the soil is three types.

[0080] The second layer of strong weathered diorite (K): grayish brown, locally grayish white, equigranular structure, blocky structure, mainly composed of hornblende and feldspar, core in the form of fragments and columns, general block diameter 20-80 mm, maximum block diameter 110 mm, general column length 5-15 cm, maximum column length 20 cm, RQD value about 10%-20%, hammer easily broken. This layer is exposed in the ZK5 hole with a thickness of 5.20, and the soil-rock grade is VI grade, and the rock is weak.

[0081] The third layer of moderately weathered diorite (K): grayish brown, locally grayish white, equigranular structure, massive structure, mainly composed of hornblende and feldspar, the core is in the form of fragments and columns, the diameter of the fragments is generally 20-80 mm, the maximum diameter is 110 mm, the length of the columns is generally 5-8 cm, the maximum length is 15 cm, the RQD value is about 20%-35%, and the hammer is not easy to break. The layer is distributed in the whole field area, and is not penetrated. The maximum layer thickness is 24.50 m, the soil and stone grade is grade IX, and the hard stone is generally used.

[0082] According to table 2, the soil and stone grade classification of the test results is shown in table 5, and the compactness of the gravel layer revealed by the drilling and the dynamic exploration number of the pipe conveying station geotechnical engineering investigation report are used. The weathering degree and natural uniaxial strength of granodiorite are classified according to "oil and gas field and pipeline geotechnical engineering investigation standard" (GB / T 50568-2019) 4.2.20 table 4.2.20 soil and stone grade and classification. The classification results are shown in table 6.

[0083] Table 5: soil and stone grade classification table of test point 1 (ZK5 hole) surface wave apparent velocity (offset = 2.5m)

[0084]

[0085] Table 6: dynamic exploration and uniaxial soil and stone grade classification table of test point 1 (ZK5 hole)

[0086]

[0087]

[0088] Figure 4 For the core photos obtained by using the existing technology of test point 1 (ZK5), from the comparison of the surface wave apparent velocity value of test point 1 (ZK5) and the stratum revealed by drilling, the conclusions are as follows:

[0089] 1) the soil and stone interface layering according to the surface wave apparent velocity is accurate and reliable

[0090] The arrangement of offset distance offset = 2.5m is arranged at the point of ZK5, the surface wave of the base rock surface is 5.4m, and the base rock surface revealed by drilling is 5.6m, the difference between them is 0.2m, and the depth error rate is 3.5%.

[0091] 2) the surface wave apparent velocity classification of gravel soil is more accurate

[0092] According to the surface wave apparent velocity, the 1 layer of pebbles revealed by drilling can be subdivided into slightly dense, medium dense and dense three layers according to the surface wave apparent velocity. For soil and rock grades, it is respectively Ⅱ, Ⅲ and Ⅳ grade, and the coincidence degree with the dynamic exploration data is very good. In the geotechnical investigation report, the pebble layer is only divided into 1 layer, and the density degree is described as slightly dense-dense, which spans 3 density degrees. The surface wave apparent velocity classification is more accurate.

[0093] So far, the embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein according to the above description.

[0094] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or some technical features can be replaced equivalently without departing from the scope and spirit of the present disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way.

Claims

1. A soil and rock grading method based on surface wave apparent velocity, characterized in that: Collect the seismic surface wave velocity of the area to be surveyed, analyze the collected seismic surface wave velocity data, and obtain the corresponding soil and rock grade based on the correspondence between the surface wave velocity value and the soil and rock grade.

2. The soil and rock grading method based on surface wave apparent velocity according to claim 1 is characterized in that: The acquisition of seismic surface wave velocity in the area to be surveyed includes: The shallow seismic refraction wave method is used. With the line exploration point as the center, surface wave data are collected at the endpoints on both sides of the seismic arrangement and at the predetermined offset distance to obtain the seismic surface wave data at each coordinate.

3. The soil and rock grading method based on surface wave apparent velocity according to claim 2 is characterized in that: The seismic surface wave data at each coordinate is transient surface wave data.

4. The soil and rock grading method based on surface wave apparent velocity according to claim 1, characterized in that: The analysis of the collected seismic surface wave velocity data is based on the characteristic that the density of the rock and soil mass and the seismic surface wave velocity have a linear correlation.

5. The soil and rock grading method based on surface wave apparent velocity according to claim 1 is characterized in that: The analysis of the collected seismic surface wave velocity data includes: extracting dispersion curves and performing cross-spectral analysis on the collected seismic surface wave data, and providing layer thickness and layer apparent surface wave velocity values ​​for line exploration points.

6. The soil and rock grading method based on surface wave apparent velocity according to claim 1 is characterized in that: Combined with the corresponding relationship between surface wave velocity value and soil and rock grade: According to the properties of rock and soil, the corresponding relationship between surface wave apparent velocity value and soil and rock grade is established, and the soil and rock grade classification is carried out in layers.

7. The soil and rock grading method based on surface wave apparent velocity according to claim 6 is characterized in that: The properties of the rock and soil mass include rock and soil mass density, rock natural uniaxial compressive strength and penetration number.

8. The soil and rock grading method based on surface wave apparent velocity according to claim 1 is characterized in that: Analysis of the collected seismic surface wave velocity data includes: Perform digital filtering and parameter rearrangement on the acquired seismic surface wave velocity data to obtain effective seismic surface wave data; Extracting dispersion curves from the effective seismic surface wave data; Performing model inversion and model iteration based on the dispersion curve; Based on the model inversion and model iteration, a surface wave apparent velocity result map of each exploration point is obtained.

9. The soil and rock grading method based on surface wave apparent velocity according to claim 1, characterized in that: The surface wave apparent velocity result map includes offset distance, layer bottom depth and surface wave apparent velocity value.

10. The soil and rock grading method based on surface wave apparent velocity according to claim 1, characterized in that: The corresponding relationship between surface wave velocity value and soil and rock grade includes: The apparent velocity of surface waves is no more than 150m / s, and the soil and rock grade is level one; The apparent surface wave velocity is greater than 150m / s and not greater than 250m / s, and the soil and rock grade is level 2; The apparent surface wave velocity is greater than 250m / s and not greater than 350m / s, and the soil and rock grade is Grade III; The apparent surface wave velocity is greater than 350m / s and not greater than 450m / s, and the soil and rock grade is Grade IV; The apparent surface wave velocity is greater than 450m / s and not greater than 550m / s, and the soil and rock grade is level five; The apparent surface wave velocity is greater than 550m / s and not greater than 900m / s, and the soil and rock grade is level 6; The apparent surface wave velocity is greater than 900m / s and not greater than 1200m / s, and the soil and rock grade is level seven; The apparent surface wave velocity is greater than 1200m / s and not greater than 1500m / s, and the soil and rock grade is level eight; The apparent surface wave velocity is greater than 1500m / s and not greater than 2000m / s, and the soil and rock grade is grade nine; The apparent surface wave velocity is greater than 2000m / s and not greater than 2500m / s, and the soil and rock grade is level ten; The apparent surface wave velocity is greater than 2500m / s, and the soil and rock grade is above level ten.

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