Method for analyzing variation of deep filling soil dynamic compaction reinforcement depth and surface wave velocity

Abstract

The application provides a method for analyzing variation rules of deep filling soil dynamic compaction reinforcement depth and surface wave velocity. The method is as follows: selecting at least four test areas in deep filling soil site, carrying out dynamic compaction construction with different energy levels, the dynamic compaction energy levels include low, medium, high and super high energy levels, and respectively carrying out heavy dynamic penetration test and multi-channel transient surface wave test before and after dynamic compaction of each area; determining the first reinforcement depth H1 and the second reinforcement depth H2 through the dynamic penetration blow count growth rate; and counting the dynamic penetration blow counts and corresponding surface wave velocities before and after dynamic compaction of the same position in different test areas, establishing the relationship curve between the surface wave velocity of the filling soil and the dynamic penetration blow count, and determining the judgment standard of the filling soil density in the site. The application provides reliable theoretical basis and technical guidance for obtaining key mechanical indexes of deep filling soil and reasonably determining the dynamic compaction reinforcement depth, lays a solid foundation for design and construction of similar projects, and has wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of foundation treatment technology in geotechnical engineering, and specifically relates to a method for analyzing the reinforcement depth and surface wave velocity variation law of different energy levels of dynamic compaction treatment for deep fill. The scope of application is the dynamic compaction treatment of deep fill sites, and can be expanded to the dynamic compaction treatment of soft soil, silt, sandy soil and other sites. Background Art

[0002] With the expansion of mountainous cities, land use conflicts are becoming increasingly prominent. The number of projects using the "opening mountains and filling valleys" method is increasing, resulting in deep fill foundations. Many of these deep fills are not treated in a planned and organized manner during the initial backfilling process, but are simply piled or dumped randomly. These deep, soft rock fills constantly create very difficult geotechnical engineering problems during construction, making them difficult and costly to resolve. Therefore, sites with similar deep fills urgently need to resolve these geotechnical engineering issues.

[0003] Dynamic compaction is economical, effective, and widely applicable. It involves repeatedly lifting a rammer to a certain height and then allowing it to fall freely. The kinetic energy is converted into significant impact energy within the soil, vibrating and compacting it, increasing the bearing capacity of the foundation and reducing soil compressibility. It also enhances soil uniformity and reduces differential settlement. While existing specifications, regulations, and various engineering manuals address the objectives, methods, and requirements for surveying and testing deep fill using dynamic compaction, these standards are limited in purpose, lack key mechanical property indicators, and employ a single approach. The depth and accuracy of fill evaluation and analysis are insufficient, hindering the ability to effectively guide subsequent fill foundation treatment design and construction. First, various terms have emerged regarding the "reinforcement depth" of deep fill using dynamic compaction, including "effective reinforcement depth," "influence depth," "reinforcement range," "effective reinforcement range," or "reinforced soil layer thickness." Due to differing definitions of depth among domestic and international experts and scholars, these concepts are often mixed. Furthermore, there are some discrepancies in the calculation of depths defined differently, making it difficult to provide reliable dynamic compaction parameters for engineering projects. Secondly, the methods for surveying and testing fill before and after dynamic compaction are not perfect, and there are relatively few studies that combine dynamic in-situ testing with surface wave geophysical testing to provide corroborative evidence. Therefore, it is necessary to provide a method to accurately analyze and determine the relationship between the reinforcement depth and surface wave velocity changes in deep fill after dynamic compaction treatment of different energy levels. Summary of the Invention

[0004] In order to solve the problem of inaccurate parameters of dynamic compaction reinforcement depth in existing engineering fields, a method for accurately analyzing the dynamic compaction reinforcement depth of deep fill at different energy levels is provided. This method can provide a reliable theoretical basis and technical guidance for obtaining the mechanical indicators of deep fill and reasonably determining the dynamic compaction reinforcement depth.

[0005] In order to achieve the above technical purposes, the present application provides a method for analyzing the variation law of deep filling soil dynamic compaction reinforcement depth and surface wave velocity, and the specific steps of the method are as follows:

[0006] S1: In the deep filling soil site, at least four test areas with a filling thickness greater than the estimated value or empirical value of the reinforcement depth are selected, a set of heavy dynamic penetration tests and a set of multi-channel transient surface wave tests are respectively carried out in each test area, and the heavy dynamic penetration and multi-channel transient surface wave test point positions are consistent;

[0007] S2: Different energy levels of dynamic compaction are carried out for the at least four test areas in the S1 step, and the dynamic compaction energy levels include low energy level, medium energy level, high energy level and super high energy level; after the dynamic compaction construction is completed, the site is left for 5-10 days, the site is leveled, and a 15-20t road roller is used for vibration rolling for 6-8 times;

[0008] S3: In the S2 step, a set of heavy dynamic penetration tests and a set of multi-channel transient surface wave tests are again carried out for each test area, and the test process and test point positions are consistent with those before the dynamic compaction in the S step;

[0009] S4: The dynamic penetration variation curves of the filling soil before and after the dynamic compaction in the at least four test areas in the S1 step are drawn, the dynamic penetration blow count growth rate of the heavy dynamic penetration test at different depths before and after the dynamic compaction in each test area is calculated, and the first reinforcement depth H1 and the second reinforcement depth H2 of each test area are determined according to the size of the dynamic penetration blow count growth rate δ; the specific process is as follows:

[0010] (1) First, the dynamic penetration blow count growth rate δ of each test area before and after the dynamic compaction at different depths is calculated according to formula ①:

[0011]

[0012] In the above formula: δ is the growth rate of the dynamic penetration blow count before and after the dynamic compaction (%);

[0013] ΔN is the growth amount of the dynamic penetration blow count before and after the dynamic compaction (blows);

[0014] N 63.5前 is the dynamic penetration blow count before the dynamic compaction (blows);

[0015] N 63.5后 is the dynamic penetration blow count after the dynamic compaction (blows);

[0016] (2) The dynamic penetration number growth rate δ before and after dynamic compaction at different depths in the heavy dynamic penetration test in each test area is divided, and the first reinforcement depth H1 and the second reinforcement depth H2 of the test area are determined; the maximum depth within the range of the dynamic penetration number growth rate δ ≥ 50% is the first reinforcement depth H1 of the test area, that is, the actual reinforcement treatment depth under the dynamic compaction energy level corresponding to the test area in engineering application; the maximum depth within the range of the dynamic penetration number growth rate 10% ≤ δ < 50% is the second reinforcement depth H2 of the test area, that is, the maximum impact depth under the dynamic compaction energy level corresponding to the test area in engineering application;

[0017] S5: Draw the surface wave velocity change curves of the fill before and after dynamic compaction in at least four test areas in step S1, and count the surface wave velocity change curves of the fill in the range of 0 to the first reinforcement depth H1 before and after dynamic compaction, and ... 1～ The average value of the surface wave velocity within the second reinforcement depth H2, and the calculation of the surface wave velocity growth rate before and after dynamic compaction;

[0018] S6: Count the number of dynamic impacts and the corresponding surface wave velocity before and after dynamic compaction at the same position of at least four test areas in step S1, calculate the average value every 2m of vertical depth, establish a relationship curve between the surface wave velocity and the number of dynamic impacts of the fill, obtain the relationship formula between the surface wave velocity and the number of dynamic impacts by fitting, and derive the judgment standard of the fill density in the site.

[0019] A better technical solution of the present invention: the fill thickness of the representative area selected in S1 is at least 10m greater than the estimated value or empirical value of the reinforcement depth; the heavy-duty dynamic probing test adopts a continuous dynamic probing test with a vertical spacing of 0.1m to obtain the number of dynamic probing hits corresponding to different fill depths; the multi-channel transient surface wave test obtains the surface wave velocities corresponding to different fill depths at intervals of 0.5m.

[0020] A further technical solution of the present invention: the classification criteria for the dynamic compaction energy level E in the step S2 are as follows: low energy level: E≤4000kN·m; medium energy level: 4000kN·m<E≤6000kN·m, high energy level: 6000kN·m<E≤8000kN·m, ultra-high energy level: E>8000kN·m.

[0021] A further technical solution of the present invention is that the first reinforcement depth H1 in step S4 is the maximum depth among the depths corresponding to the dynamic probing change curve within the range of the dynamic probing hit number growth rate δ ≥ 50%. Within this depth range, the physical and mechanical indicators of the fill change significantly, achieving the established goals, and can be used as the actual reinforcement depth in engineering applications;

[0022] The second reinforcement depth H2 is the maximum depth among the depths corresponding to the dynamic probing change curve within the range of 10%≤δ<50%. In this depth range, the growth rate of the soil dynamic probing number is limited, and the physical and mechanical indicators of the fill change. It is the maximum impact depth of dynamic compaction and can be used as a reinforcement depth for engineering safety reserve or further utilization;

[0023] The values ​​of the dynamic detection number growth rate range of 0≤δ<10% are within the error range and can be ignored.

[0024] A further technical solution of the present invention is as follows: the specific calculation process of the wave velocity growth rate before and after the dynamic compaction in step S5 is as follows:

[0025] (1) Calculate the surface wave velocity results every 0.5m in the vertical direction within the range of 0 to the first reinforcement depth H1 before dynamic compaction and calculate the average value Count the surface wave velocity results every 0.5m in the vertical direction within the first reinforcement depth range H1 to the second reinforcement depth H2 before dynamic compaction, and calculate the average value

[0026] (2) Calculate the surface wave velocity results every 0.5m in the vertical direction within the range of 0 to the first reinforcement depth H1 after dynamic compaction, and calculate the average value Calculate the surface wave velocity results every 0.5m in the vertical direction within the first reinforcement depth range H1 to the second reinforcement depth H2 after dynamic compaction, and calculate the average value

[0027] (3) According to formula ② and formula ③, the growth rate Δ1 of the surface wave velocity in the range of 0 to the first reinforcement depth H1 before and after dynamic compaction, and the growth rate Δ2 of the surface wave velocity in the range of the first reinforcement depth H1 to the second reinforcement depth H2 are calculated respectively:

[0028]

[0029]

[0030] A further technical solution of the present invention is as follows: In step S6, a curve of the relationship between the surface wave velocity of the fill and the number of dynamic soundings is established, and a specific process of fitting the relationship between the surface wave velocity and the number of dynamic soundings is as follows:

[0031] (1) The dynamic compaction depth of each dynamic compaction point in each test area was segmented, and the segmentation rule was carried out according to the vertical interval of 2m. The middle depth h of each depth segment of the dynamic compaction depth range of each dynamic compaction point in each test area was calculated, where h = n + (n + 2) / 2, where n = 0, 2, 4, 6 ... n + 2;

[0032] (2) Count the number of dynamic probing strikes before dynamic compaction in each depth segment in step (1), and calculate the average value of the number of dynamic probing strikes before dynamic compaction in the corresponding depth segment. The statistical interval of data within each depth range is 0.1m;

[0033] (3) Statistical step (1) The front wave velocity of each depth segment before the dynamic compaction, and calculate the average front wave velocity of the corresponding depth segment The statistical interval of data within each depth range is 0.5m;

[0034] (4) The average number of dynamic strikes before dynamic compaction in each depth section calculated in step (2) is As the number of dynamic probing shots corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the range of the dynamic compaction depth of each dynamic compaction point and the average value of the dynamic probing shots corresponding to the depth segment are plotted. The curve; the average wave velocity before the dynamic compaction of each depth section calculated in step (3) As the front wave velocity of the dynamic compaction front corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the dynamic compaction depth range of each dynamic compaction point and the average front wave velocity of the corresponding depth segment are plotted. curve;

[0035] (5) According to the same rules and methods as in step (2), the average number of dynamic strikes after dynamic compaction in each depth section is calculated. And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the dynamic compaction depth of each dynamic compaction point and the average value of the dynamic detection number after dynamic compaction of the corresponding depth segment. curve;

[0036] (6) According to the same rules and methods as in step (3), calculate the average wave velocity after the strong compaction at each depth section. And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth segment. curve;

[0037] (7) Based on the statistical data in the above steps, a curve is drawn showing the relationship between the average value of the number of dynamic strikes before and after dynamic compaction and the intermediate depth h, and a curve is drawn showing the relationship between the average value of the wave velocity before and after dynamic compaction and the intermediate depth h;

[0038] (8) Draw the same point at the same intermediate depth h in different test areas and The relationship curve of the surface wave velocity and the number of dynamic soundings is fitted to establish the logarithmic relationship between the surface wave velocity and the number of dynamic soundings, as shown in formula ④.

[0039] V R= aln(N 63.5 )+ b

[0040] V = a ln(N R — surface wave velocity (m / s)

[0041] N 63.5 — number of blows of dynamic sounding

[0042] a, b — fitting coefficients

[0043] (5) calculating the number of blows N of the heavy dynamic sounding by the formula (4) 63.5 surface wave velocity V at the number of blows of 5, 10, 20 R value, determining the judgment standard of the compactness of the fill in the site.

[0044] The beneficial effects of the present application: the present application adopts the technical means of combining and verifying the dynamic sounding in-situ test and the surface wave geophysical test, carries out the dynamic compaction test in four energy level ranges (low energy level, medium energy level, high energy level, super high energy level), proposes the concepts of the first reinforcement depth and the second reinforcement depth of dynamic compaction, proposes the method for accurately determining the first reinforcement depth and the second reinforcement depth of dynamic compaction by using the heavy dynamic sounding test, can provide important standards for the dynamic compaction evaluation of related projects at home and abroad. The variation law of the surface wave velocity of the deep fill treated by dynamic compaction is accurately analyzed, the empirical formula between the number of blows of dynamic sounding and the surface wave velocity of deep fill is proposed, which provides engineering basis for the fine division of layers and the determination of key mechanical indexes of similar deep fill foundations in the future. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is the dynamic sounding variation curve of the fill before and after dynamic compaction with a ramming energy of 3000 kN.m in the embodiment;

[0046] Figure 2 is the dynamic sounding variation curve of the fill before and after dynamic compaction with a ramming energy of 6000 kN.m in the embodiment;

[0047] Figure 3 is the dynamic sounding variation curve of the fill before and after dynamic compaction with a ramming energy of 8000 kN.m in the embodiment;

[0048] Figure 4 is the dynamic sounding variation curve of the fill before and after dynamic compaction with a ramming energy of 12000 kN.m in the embodiment;

[0049] Figure 5 is the dynamic sounding variation curve of the fill before and after dynamic compaction with a ramming energy of 15000 kN.m in the embodiment;

[0050] Figure 6 is the relationship curve between the dynamic sounding and the intermediate depth h of the fill before and after dynamic compaction with a ramming energy of 3000 kN.m in the embodiment; and the intermediate depth h of the fill before and after dynamic compaction with a ramming energy of 3000 kN.m in the embodiment;

[0051] Figure 7 The ramming energy in the embodiment is 6000kN·m before and after the strong ramming of the backfill The relationship curve with the intermediate depth h;

[0052] Figure 8 The tamping energy in the embodiment is 8000kN·m before and after the strong tamping of the backfill The relationship curve with the intermediate depth h;

[0053] Figure 9 In the embodiment, the ramming energy is 12000kN·m before and after the strong ramming of the backfill The relationship curve with the change of the intermediate depth h;

[0054] Figure 10 The ramming energy in the embodiment is 15000kN·m before and after the strong ramming of the backfill The relationship curve with the intermediate depth h;

[0055] Figure 11 The ramming energy in the embodiment is 3000kN·m before and after the strong ramming of the backfill The relationship curve with the intermediate depth h;

[0056] Figure 12 The ramming energy in the embodiment is 6000kN·m before and after the strong ramming of the backfill The relationship curve with the intermediate depth h;

[0057] Figure 13 The tamping energy in the embodiment is 8000kN·m before and after the strong tamping of the backfill The relationship curve with the change of the intermediate depth h;

[0058] Figure 14 In the embodiment, the ramming energy is 12000kN·m before and after the strong ramming of the backfill The relationship curve with the change of the intermediate depth h;

[0059] Figure 15 The ramming energy in the embodiment is 15000kN·m before and after the strong ramming of the backfill The relationship curve with the change of the intermediate depth h;

[0060] Figure 16 The fill in the embodiment and The change relationship curve. DETAILED DESCRIPTION

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figures 1 to 16The drawings are simplified and are used only for the purpose of clarity and conciseness in illustrating the embodiments of the present application. The technical solutions shown in the drawings are specific schemes of the embodiments of the present application, and are not intended to limit the scope of the claimed present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0062] The classification criteria of the dynamic compaction energy level E in the present application are as follows: low energy level: E≤4000kN·m; medium energy level: 4000kN·m<E≤6000kN·m, high energy level: 6000kN·m<E≤8000kN·m, and super-high energy level: E>8000kN·m.

[0063] The embodiment provides a method for analyzing the variation law of deep filling soil dynamic compaction reinforcement depth and surface wave velocity, and the specific steps are as follows:

[0064] S1. In the deep filling soil site, five representative areas with filling thickness far greater than the estimated value or empirical value of the reinforcement depth are selected, and a set of heavy dynamic penetration tests and a set of multi-channel transient surface wave tests are respectively performed in each test area; the cone dynamic penetration test is to use a 63.5kg hammer to hit the penetration rod for 10cm under the hammering energy of a 76cm drop distance, and the dynamic penetration number is corrected for the rod length; the dynamic penetration test adopts continuous dynamic penetration test with a vertical spacing of 0.1m, and the dynamic penetration numbers corresponding to the filling depths of 0.1m, 0.2m, 0.3m, 0.4m, 0.5m, 0.6m…… are obtained, and the variation curve of the dynamic penetration number and the depth of the filling soil is drawn. The multi-channel transient surface wave test is to use the dispersion characteristics of Rayleigh wave in the medium, use Rayleigh surface wave of various frequency components excited by artificial source, and find the relationship between the wave velocity and the frequency. The shear wave propagation velocity at different depths of the stratum is obtained through interpretation, and then the uniformity of the reinforced soil body is evaluated; the surface wave test adopts a single-end excitation method, arranges 12 detectors, the detector frequency is 4Hz, the inter-channel distance is 1m, the offset distance is 5m, the sampling point number is 2048 points, the sampling interval is 250us, and the surface wave velocities corresponding to the filling depths of 0.5m, 1m, 1.5m, 2.0m, 2.5m, 3.0m…… are obtained through the test.

[0065] S2. Five dynamic compaction constructions with different energy levels are respectively performed in the above five test areas, the dynamic compaction energy levels are 3000kN·m, 6000kN·m, 8000kN·m, 12000kN·m and 15000kN·m respectively, after the dynamic compaction construction is completed, the site is left for 7 days, the site is leveled, and a 15-20t road roller is used for vibration rolling for 6-8 times; the dynamic compaction partition is specifically shown in Table 1.

[0066] Table 1 Dynamic compaction test zones

[0067]

[0068] S3. After step S2 is completed, conduct a set of heavy-duty dynamic penetration tests and a set of multi-channel transient surface wave tests for each test area. The test process and test point locations remain consistent with the pre-compaction test process and test point locations in step S.

[0069] S4. Draw the dynamic exploration change curves of the fill before and after dynamic compaction in the five test areas, such as Figures 1 to 5 As shown; calculate the growth rate of dynamic penetration number before and after dynamic compaction at different depths in each test area in the heavy dynamic penetration test, and determine the first reinforcement depth H1 and the second reinforcement depth H2 of each test area based on the growth rate δ of dynamic penetration number; the specific process is as follows:

[0070] (1) First, calculate the growth rate δ of the dynamic penetration number before and after dynamic compaction at different depths in each test area using formula ①:

[0071]

[0072] In the above formula: δ—is the growth rate of the number of dynamic probes before and after dynamic compaction (%);

[0073] ΔN—is the increase in the number of dynamic probe strikes before and after dynamic compaction (strikes);

[0074] N 63.5前 —Number of probing blows before dynamic compaction (blows);

[0075] N 63.5后 —Number of dynamic probing blows after dynamic compaction (blows);

[0076] (2) The dynamic penetration test of each test area is divided into the growth rate δ of the dynamic penetration test before and after the dynamic compaction at different depths, and the first reinforcement depth H1 and the second reinforcement depth H2 of the test area are determined; the maximum depth within the range of the dynamic penetration test growth rate δ≥50% is the first reinforcement depth H1 of the test area, that is, the actual reinforcement depth under the dynamic compaction energy level of the test area in the engineering application; the first reinforcement depth H1 is the maximum depth among the depths corresponding to the dynamic penetration change curve within the range of the dynamic penetration test growth rate δ≥50%. When δ≥50%, the dynamic penetration test of the soil increases significantly. The denser the soil, the reinforcement depth at this time is the first reinforcement depth H1, which is the actual reinforcement depth used in the engineering. The physical and mechanical indicators of the fill change significantly within this depth range, achieving the established goals; the dynamic penetration test of the soil increases significantly. The maximum depth of the blow growth rate in the range of 10%≤δ<50% is the second reinforcement depth H2 of the test area, that is, the maximum influence depth under the dynamic compaction energy level corresponding to the test area in engineering applications; the second reinforcement depth H2 dynamic probe blow growth rate is in the range of 10%≤δ<50%, which is the maximum depth among the depths corresponding to the dynamic probe change curve. When 10%≤δ<50%, although the soil dynamic probe blow number increases, the growth rate is limited. At this time, the reinforcement depth is the second reinforcement depth H2, which is the maximum influence depth of dynamic compaction. The physical and mechanical indicators of the fill change within this depth range, which can be used as a reinforcement treatment depth for engineering safety reserves or further utilization; when 0≤δ<10%, the soil dynamic probe blow number increases very little. Considering the deviation of the experimental testing means, the changes in this part of the physical and mechanical indicators are negligible.

[0077] Through the above calculation process, the first reinforcement depth and second reinforcement depth of each dynamic compaction energy level are determined as shown in Table 2:

[0078] Table 2 The first reinforcement depth and the second reinforcement depth of dynamic compaction at different energy levels

[0079]

[0080] S5. Draw the surface wave velocity change curves of the fill before and after dynamic compaction in the five test areas in step S1, and count the surface wave velocity changes in the range of 0 to the first reinforcement depth H1 and the first reinforcement depth H2 before and after dynamic compaction. 1～ The average value of the surface wave velocity within the second reinforcement depth H2 is calculated, and the surface wave velocity growth rate before and after dynamic compaction is calculated; the specific calculation process is as follows:

[0081] (1) Calculate the surface wave velocity results every 0.5m in the vertical direction within the range of 0 to the first reinforcement depth H1 before dynamic compaction and calculate the average value Count the surface wave velocity results of each 0.5m vertically within the range of the first reinforcement depth H1 to the second reinforcement depth H2 before dynamic compaction, and calculate the average value

[0082] (2) Statistics of the Rayleigh wave velocity results in the vertical direction every 0.5m in the range of 0~first reinforcement depth H1 after dynamic compaction, and calculation of the average value Statistics of the Rayleigh wave velocity results in the vertical direction every 0.5m in the range of first reinforcement depth H1~second reinforcement depth H2 after dynamic compaction, and calculation of the average value

[0083] (3) According to formula ② and formula ③, the growth rate Δ1 of Rayleigh wave velocity in the range of 0~first reinforcement depth H1 before and after dynamic compaction, and the growth rate Δ2 of Rayleigh wave velocity in the range of first reinforcement depth H1~second reinforcement depth H2 are calculated respectively:

[0084]

[0085]

[0086] According to the above calculation method, the Rayleigh wave velocity growth rate before and after dynamic compaction is shown in Table 3.

[0087] Table 3 Rayleigh wave velocity growth rate in the range of first reinforcement depth and second reinforcement depth under different energy levels of dynamic compaction

[0088]

[0089] S6. Statistics of the dynamic sounding blow counts and corresponding Rayleigh wave velocities before and after dynamic compaction in the same position in the five test areas in step S1, calculation of the average value every 2m in the vertical direction, establishment of the relationship curve between the Rayleigh wave velocity of the fill and the dynamic sounding blow counts, fitting to obtain the relationship formula between the Rayleigh wave velocity and the dynamic sounding blow counts, and obtaining the judgment standard of the fill density in the site; the specific process is as follows:

[0090] (1) The dynamic compaction depth of each dynamic compaction point in each test area is segmented, the segmentation rule is 2m in the vertical direction, such as 0~2m, 2~4m, 4~6m……, and the middle depth h of each depth segment in the dynamic compaction depth range of each dynamic compaction point in each test area is counted, h=n+(n+2) / 2, wherein n=0, 2, 4, 6……n+2; such as 0~2m (the middle depth h is 1m), 2~4m (the middle depth h is 3m), 4~6m (the middle depth h is 3m), 6~8m (the middle depth h is 7m)……, the corresponding middle depths are counted.

[0091] (2) Statistics of the dynamic sounding blow counts before dynamic compaction in each depth segment in step (1), and calculation of the average value of the dynamic sounding blow counts before dynamic compaction in the corresponding depth segment The statistical interval of data within each depth section is 0.1m; for example, in the depth section of 2-4m, the statistical data are 2.1m, 2.2m, 2.3m, 2.4m, 2.5m, 2.6m...3.8m, 3.9m, 4.0m, and the average value of the dynamic sounding number before dynamic compaction in the depth section of 2-4m is calculated; the average value of the dynamic sounding number before dynamic compaction in each depth section of 0-2m, 2-4m, 4-6m... is calculated in sequence;

[0092] (3) Statistical step (1) The front wave velocity of each depth segment before the dynamic compaction, and calculate the average front wave velocity of the corresponding depth segment The statistical interval of data in each depth range is 0.5m. For example, if the surface wave depth is 2-4m, the statistical data are 2.5m, 3.0m, 3.5m, and 4.0m. Calculate the average velocity of the surface wave before the dynamic compaction in the depth range of 2-4m, and then calculate the average velocity of the surface wave before the dynamic compaction in each depth range of 0-2m, 2-4m, 4-6m, and so on.

[0093] (4) The average number of dynamic strikes before dynamic compaction in each depth section calculated in step (2) is As the number of dynamic strikes before strong compaction corresponding to the middle depth h of the depth segment, for example, the average wave velocity and the average surface wave velocity before strong compaction in the depth segment of 0-2m correspond to the average wave velocity and the average surface wave velocity before strong compaction in the middle depth of 1m; the average wave velocity and the average surface wave velocity before strong compaction in the depth segment of 2-4m correspond to the average wave velocity and the average surface wave velocity before strong compaction in the middle depth of 3m; according to the above rules, the middle depth h of multiple depth segments within the range of strong compaction depth of each strong compaction point and the average number of dynamic strikes before strong compaction in the corresponding depth segment are plotted curve;

[0094] The average velocity of the front wave of each depth segment calculated in step (3) is As the front wave velocity of the dynamic compaction front corresponding to the middle depth h of the depth segment, the specific rules are the same as the above. Then, the middle depth h of multiple depth segments within the dynamic compaction depth range of each dynamic compaction point and the average front wave velocity of the corresponding depth segment are plotted. curve;

[0095] (5) According to the same rules and methods as in step (2), the average number of dynamic strikes after dynamic compaction in each depth section is calculated. And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the dynamic compaction depth of each dynamic compaction point and the average value of the dynamic detection number after dynamic compaction of the corresponding depth segment. curve;

[0096] (6) According to the same rules and methods as in step (3), calculate the average wave velocity after the strong compaction at each depth section. And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth segment. curve;

[0097] (7) Based on the statistical data in the above steps, draw a curve showing the relationship between the average value of the dynamic detection number before and after dynamic compaction and the change of the intermediate depth h, as shown in the figure: Figures 6 to 10 As shown, the relationship curve between the average wave velocity before and after dynamic compaction and the intermediate depth h is drawn, as shown in Figures 11 to 15 As shown;

[0098] (8) Draw the same point at the same intermediate depth h in different test areas and The change relationship curve of Figure 16 As shown, curve fitting is performed to establish the logarithmic relationship between surface wave velocity and dynamic detection number, as shown in formula ④;

[0099] V R =aln(N 63.5 )+b④

[0100] Where: V R —Surface wave velocity (m / s)

[0101] N 63.5 —Number of dynamic detections (hits)

[0102] a, b—fitting coefficients

[0103] Among them: coefficient a = 38.04, b = 125.28.

[0104] The surface wave velocity and the number of dynamic soundings are in a logarithmic relationship, with a high degree of fit. According to the above formula, N 63.5 The corresponding surface wave velocity V when the number of hits is 5, 10, and 20 R The values ​​are 187, 213, and 239, respectively. Based on this, the judgment criteria for the density of fill soil in the site are obtained, as shown in Table 4:

[0105] Table 4 Criteria for judging the density of fill soil within the site

[0106]

[0107] The present invention provides a reliable theoretical basis and technical guidance for obtaining key indicators of deep fill and implementing dynamic compaction projects. Reasonable determination of the dynamic compaction reinforcement depth can greatly reduce project costs, and also provide a theoretical basis and reference significance for optimized design for similar projects in the future. It can save a lot of project investment for project construction parties, avoid unnecessary project construction costs, and has good economic benefits.

[0108] In summary, the content of the present application is not limited in the above-mentioned embodiments, and those skilled in the same field can easily propose other embodiments within the technical guiding ideology of the present application, but such embodiments are included in the scope of the present application.

Claims

1. A method for analyzing the variation of the depth and surface wave velocity of deep fill reinforcement by dynamic compaction, characterized in that The specific steps of the method are as follows: S1: In a deep fill site, select at least four test areas where the fill thickness is greater than the estimated or empirical value of the reinforcement depth. Conduct one set of heavy-duty dynamic penetration tests and one set of multi-channel transient surface wave tests in each test area. The locations of the heavy-duty dynamic penetration and multi-channel transient surface wave tests should be consistent. S2: Perform dynamic compaction at different energy levels for at least four test areas in step S1, including low, medium, high, and ultra-high energy levels. After the dynamic compaction, the site is left to stand for 5-10 days to level the site, and then vibrated and compacted 6-8 times using a 15-20t roller. S3: After step S2 is completed, a set of heavy-duty dynamic penetration tests and a set of multi-channel transient surface wave tests are conducted again for each test area. The test process and test point locations are consistent with the test process and test point locations before dynamic compaction in step S1. S4: Draw the dynamic penetration change curves of the fill before and after dynamic compaction in at least four test areas in step S1, calculate the growth rate of the dynamic penetration number before and after dynamic compaction at different depths in the heavy dynamic penetration test in each test area, and determine the first reinforcement depth H1 and the second reinforcement depth H2 of the dynamic compaction in each test area based on the growth rate δ of the dynamic penetration number. The specific process is as follows: (1) First, calculate the growth rate δ of the dynamic penetration number before and after dynamic compaction at different depths in each test area according to formula ①: ① In the above formula: δ—is the growth rate of the number of dynamic impacts before and after dynamic compaction; ∆N—is the increase in the number of dynamic impacts before and after dynamic compaction; N 63.5前 —Number of dynamic strikes before dynamic compaction; N 63.5后 —Number of dynamic strikes after dynamic compaction; (2) The dynamic penetration number growth rate δ before and after dynamic compaction at different depths in the heavy dynamic penetration test in each test area is divided, and the first reinforcement depth H1 and the second reinforcement depth H2 of the test area are determined; the maximum depth within the range of the dynamic penetration number growth rate δ ≥ 50% is the first reinforcement depth H1 of the test area, that is, the actual reinforcement treatment depth under the dynamic compaction energy level corresponding to the test area in engineering application; the maximum depth within the range of the dynamic penetration number growth rate 10% ≤ δ < 50% is the second reinforcement depth H2 of the test area, that is, the maximum impact depth under the dynamic compaction energy level corresponding to the test area in engineering application; S5: draw the surface wave velocity change curves of the fill before and after dynamic compaction in at least four test areas in step S1, calculate the average value of the surface wave velocity within the range of 0 to the first reinforcement depth H1 before and after dynamic compaction, and within the range of the first reinforcement depth H1 to the second reinforcement depth H2, and calculate the surface wave velocity growth rate before and after dynamic compaction; S6: Count the number of dynamic impacts and the corresponding surface wave velocity before and after dynamic compaction at the same position of at least four test areas in step S1, calculate the average value every 2m of vertical depth, establish a relationship curve between the surface wave velocity and the number of dynamic impacts of the fill, obtain the relationship formula between the surface wave velocity and the number of dynamic impacts by fitting, and derive the judgment standard of the fill density in the site.

2. The method for analyzing the variation of deep fill reinforcement depth and surface wave velocity according to claim 1, characterized in that: The fill thickness of the representative area selected in S1 is at least 10m greater than the estimated reinforcement depth or the empirical value; The heavy-duty dynamic penetration test adopts a continuous dynamic penetration test with a vertical spacing of 0.1m to obtain the number of dynamic penetrations corresponding to different fill depths; the multi-channel transient surface wave test obtains the surface wave velocity corresponding to different fill depths with an interval of 0.5m.

3. The method for analyzing the variation of deep fill reinforcement depth and surface wave velocity according to claim 1, characterized in that: The classification criteria for the dynamic compaction energy level E in step S2 are as follows: Low energy level: E≤4000 kN·m; medium energy level: 4000 kN·m<E≤6000 kN·m, high energy level: 6000 kN·m<E≤8000 kN·m, ultra-high energy level: E>8000 kN·m.

4. The method for analyzing the variation of deep fill reinforcement depth and surface wave velocity according to claim 1, characterized in that: The first reinforcement depth H1 in step S4 is the maximum depth among the depths corresponding to the dynamic probing change curve within the range of the dynamic probing number growth rate δ ≥ 50%. Within this depth range, the physical and mechanical indicators of the fill change significantly, achieving the established goals, and can be used as the actual reinforcement depth in engineering applications; The second reinforcement depth H2 is the maximum depth in the dynamic probing change curve corresponding to the depth within the range of 10%≤δ<50%. In this depth range, the growth rate of the soil dynamic probing number is limited, and the physical and mechanical indicators of the fill change. It is the maximum impact depth of dynamic compaction and can be used as a reinforcement depth for engineering safety reserve or further utilization; The values ​​of the dynamic detection number growth rate range of 0≤δ<10% are within the error range and can be ignored.

5. The method for analyzing the variation of the deep fill reinforcement depth and surface wave velocity according to claim 2 is characterized in that The specific calculation process of the wave velocity growth rate before and after the dynamic compaction in step S5 is as follows: (1) Count the surface wave velocity results every 0.5 m in the vertical direction within the range of 0 before dynamic compaction to the first reinforcement depth H1, and calculate the average value , calculate the surface wave velocity results of each 0.5m vertically within the range of the first reinforcement depth H1 to the second reinforcement depth H2 before dynamic compaction, and calculate the average value ; (2) Count the surface wave velocity results every 0.5 m in the vertical direction within the range of 0 to the first reinforcement depth H1 after dynamic compaction, and calculate the average value , calculate the surface wave velocity results of each 0.5m vertically within the range of the first reinforcement depth H1 to the second reinforcement depth H2 after dynamic compaction, and calculate the average value ; (3) According to formula ② and formula ③, the growth rate Δ1 of the surface wave velocity in the range of 0 to the first reinforcement depth H1 before and after dynamic compaction, and the growth rate Δ2 of the surface wave velocity in the range of the first reinforcement depth H1 to the second reinforcement depth H2 are calculated respectively: ② ③。 6. The method for analyzing the variation of the deep fill reinforcement depth and surface wave velocity according to claim 2 is characterized in that The specific process of establishing the relationship curve between the surface wave velocity and the number of dynamic soundings in step S6 and fitting the relationship between the surface wave velocity and the number of dynamic soundings is as follows: (1) The dynamic compaction depth of each dynamic compaction point in each test area was segmented, with a vertical interval of 2 m. The middle depth h of each depth segment of the dynamic compaction depth range of each dynamic compaction point in each test area was calculated, where h = n + (n + 2) / 2, where n = 0, 2, 4, 6, ..., n + 2; (2) Count the number of dynamic probing shots before dynamic compaction in each depth segment in step (1) and calculate the average number of dynamic probing shots before dynamic compaction in the corresponding depth segment. , the data statistical interval within each depth range is 0.1m; (3) Statistical step (1) The front wave velocity of each depth segment is calculated, and the average front wave velocity of the corresponding depth segment is calculated. , the data statistical interval within each depth range is 0.5m; (4) The average number of dynamic strikes before dynamic compaction in each depth section calculated in step (2) is As the number of dynamic probing shots corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the range of the dynamic compaction depth of each dynamic compaction point and the average value of the dynamic probing shots corresponding to the depth segment are plotted. curve; the average velocity of the front wave of each depth segment calculated in step (3) is As the front wave velocity of the dynamic compaction front corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the dynamic compaction depth range of each dynamic compaction point and the average front wave velocity of the corresponding depth segment are plotted. curve; (5) According to the same rules and methods as in step (2), calculate the average number of dynamic strikes after dynamic compaction in each depth section. ; And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the dynamic compaction depth of each dynamic compaction point and the average value of the dynamic detection number after dynamic compaction of the corresponding depth segment curve; (6) According to the same rules and methods as in step (3), calculate the average wave velocity after the strong compaction at each depth section. ; And according to the method in step (4), draw the middle depth h of multiple depth segments within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth segment curve; (7) Based on the statistical data in the above steps, draw the relationship curve between the average value of the dynamic probe number before and after the dynamic compaction and the intermediate depth h, and draw the relationship curve between the average value of the wave velocity before and after the dynamic compaction and the intermediate depth h; (8) Draw the same point at the same intermediate depth h in different test areas and The relationship curve of the surface wave velocity and the number of dynamic soundings is fitted to establish the logarithmic relationship between the surface wave velocity and the number of dynamic soundings, as shown in formula ④. ④ Where: V R —surface wave velocity; N 63.5 —Number of dynamic probes; a, b—fitting coefficients; (9) Calculate the number of heavy-duty dynamic penetration hammer blows N using formula ④. 63.5 Surface wave velocity V with hit numbers of 5, 10, and 20 R value, and determine the criterion for judging the density of fill within the site.

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