Deep filling dynamic compaction reinforcement depth and surface wave velocity change rule analysis method

Abstract

The invention provides a deep filling dynamic compaction reinforcement depth and surface wave velocity change rule analysis method. The method comprises the steps that in a deep and thick soil filling site, at least four test areas are selected to conduct dynamic compaction construction of different energy levels, the dynamic compaction energy levels comprise the low energy level, the medium energy level, the high energy level and the ultrahigh energy level, and heavy dynamic penetration tests and multiple transient surface wave tests are conducted on each area before and after dynamic compaction; a first reinforcement depth H1 and a second reinforcement depth H2 are determined through the dynamic detection impact number growth rate; and carrying out statistics on the dynamic probing numbers and the corresponding surface wave velocities before and after dynamic compaction at the same position of different test areas, establishing a relation curve of the surface wave velocities and the dynamic probing numbers of the filling soil, and determining a judgment standard of the compactness of the filling soil in the field. Reliable theoretical basis and technical guidance are provided for obtaining key mechanical indexes of deep and thick soil filling and reasonably determining the dynamic compaction reinforcement depth, a solid foundation is laid for design and construction of similar projects, and the application prospect is wide.

Description

Technical Field

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

[0002] With the expansion of mountainous cities, land use conflicts have become increasingly prominent, and the number of projects using the "opening mountains and filling valleys" method has increased, forming deep fill foundations. In the early stage of site backfilling, many of these deep fills were not planned and organized, but were randomly piled or dumped. These deep soft rock fills constantly generate very difficult geotechnical engineering problems during the construction process. The difficulty and cost of handling are too high. Therefore, sites with similar deep fills are in urgent need of solving such geotechnical engineering problems.

[0003] The dynamic compaction method is economical, effective and widely applicable. The dynamic compaction method is to repeatedly lift the rammer to a certain height and then let it fall freely. Its kinetic energy is converted into a large impact energy in the soil, which vibrates and compacts the soil, improves the bearing capacity of the foundation, and reduces the compressibility of the soil; at the same time, it enhances the uniformity of the soil and reduces uneven settlement. For the dynamic compaction treatment of deep fill, the existing specifications, regulations and various engineering manuals have put forward the purpose, methods and requirements for the investigation and detection of fill, but due to the lack of purpose, no key mechanical property indicators are provided, the means are single, and the depth and accuracy of the evaluation and analysis of fill are not enough, which leads to the inability to better guide the subsequent fill foundation treatment design and construction. First of all, there are many names for the "reinforcement depth" of the dynamic compaction reinforcement treatment of deep fill, including "effective reinforcement depth", "influence depth", "reinforcement range", "effective reinforcement range" or "reinforced soil layer thickness". Due to the different definitions of depth by experts and scholars at home and abroad, the concepts are often mixed, and there are some differences in the calculation of depths with different definitions, which makes it impossible to provide reliable dynamic compaction parameters for the project. Secondly, the exploration and detection methods of fill before and after dynamic compaction are not perfect, and there are few studies that combine dynamic in-situ testing with surface wave geophysical tests to verify the results. Therefore, it is necessary to provide a method for accurately analyzing and determining the reinforcement depth and surface wave velocity changes of deep fill with different energy levels of dynamic compaction. Summary of the invention

[0004] In order to solve the problem of inaccurate parameters of the reinforcement depth of dynamic compaction treatment in the existing engineering field, a method for accurately analyzing the reinforcement depth of dynamic compaction treatment 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 objectives, the present invention provides a method for analyzing the variation law of deep fill reinforcement depth and surface wave velocity, and the specific steps of the method are as follows:

[0006] 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, and conduct a set of heavy dynamic penetration tests and a set of multi-channel transient surface wave tests in each test area. The locations of the heavy dynamic penetration tests and multi-channel transient surface wave tests should be consistent.

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

[0008] S3: After the completion of step S2, a group of heavy dynamic penetration tests and a group of multi-channel transient surface wave tests are carried out again for each test area. The test process and test point locations are consistent with the test process and test point locations before strong compaction in step S;

[0009] S4: Draw the dynamic probing change curves of the backfill before and after the strong compaction in at least four test areas in step S1, calculate the growth rate of the dynamic probing hits before and after the strong 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 strong compaction in each test area according to the size of the growth rate δ of the dynamic probing hits; the specific process is as follows:

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

[0011]

[0012] In the above formula: δ—is the growth rate of the number of dynamic impacts before and after strong compaction (%);

[0013] ΔN—is the increase in the number of dynamic impacts before and after strong compaction (blows);

[0014] N 63.5前 —Number of strikes before dynamic compaction (strikes);

[0015] N 63.5后 —Number of dynamic strikes after strong compaction (strikes);

[0016] (2) The dynamic penetration number growth rate δ before and after the 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 of the test area 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 influence 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 soil before and after strong compaction in at least four test areas in step S1, and count the surface wave velocity change curves of the fill soil in the range of 0 to the first reinforcement depth H1 before and after strong compaction, and ... 1～ The average value of the surface wave velocity in the second reinforcement depth H2, and the growth rate of the surface wave velocity before and after the strong compaction are calculated;

[0018] S6: Count the number of dynamic impacts and the corresponding surface wave velocity before and after strong compaction at the same position of at least four test areas in step S1, calculate the average value every 2m of vertical depth, establish the 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 with an interval of 0.5m.

[0020] A further technical solution of the present invention: the classification criteria of the strong compaction energy level E in the S2 step 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 as follows: the first reinforcement depth H1 in the step S4 is the maximum depth in the dynamic exploration change curve corresponding to the dynamic exploration hit number growth rate δ≥50%, and 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 in the dynamic exploration change curve corresponding to the depth within the range of 10%≤δ<50%. The growth rate of the dynamic exploration number of the soil in this depth range is limited, and the physical and mechanical indicators of the fill change. It is the maximum impact depth of the strong tamping 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 0≤δ<10% are within the error range and can be ignored.

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

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

[0026] (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 Statistical results of surface wave velocity 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 strong 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 the step S6, a relationship curve between the surface wave velocity of the fill and the number of dynamic soundings is established, and the 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 is segmented, and the segmentation rule is 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 is counted, h = n + (n + 2) / 2, where n = 0, 2, 4, 6 ... n + 2;

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

[0033] (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 statistics interval within each depth segment 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 strikes before strong compaction corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the range of the strong compaction depth of each strong compaction point and the average value of the dynamic strikes before strong compaction in the corresponding depth segment are plotted. The curve of the front wave velocity of each depth segment calculated in step (3) is As the front wave velocity of the strong compaction corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the strong compaction depth range of each strong compaction point and the average wave velocity of the front wave of the strong compaction corresponding to the depth segment are plotted. The curve of

[0035] (5) According to the same rules and methods as in step (2), the average number of dynamic strikes after strong compaction in each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average value of the dynamic detection number after compaction of the corresponding depth section are plotted. The curve of

[0036] (6) According to the same rules and methods as in step (3), the average wave velocity after the strong compaction at each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth section are plotted. The curve of

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

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

[0039] V R=aln(N 63.5 )+b④

[0040] Where: V R —Surface wave velocity (m / s)

[0041] N 63.5 —Number of dynamic detection (hit)

[0042] a, b—fitting coefficients

[0043] (5) Calculate the number of heavy-duty dynamic penetration hammer blows N by using formula ④ 63.5 Surface wave velocity V with 5, 10, and 20 hits R Value, determine the criterion for judging the density of fill in the site.

[0044] Beneficial effects of the invention: The invention adopts the technical means of combining dynamic in-situ testing with surface wave geophysical testing and verifying each other, and carries out dynamic compaction tests within four energy levels (low energy level, medium energy level, high energy level, and ultra-high energy level), proposes the concept of the first reinforcement depth and the second reinforcement depth of dynamic compaction, and proposes a method of using heavy dynamic probing tests to accurately determine the first reinforcement depth and the second reinforcement depth of dynamic compaction, which can provide important standards for dynamic compaction evaluation of related projects at home and abroad. The changing law of the surface wave velocity of deep fill treated by dynamic compaction is accurately analyzed, and an empirical formula between the dynamic exploration number of deep fill and the surface wave velocity is proposed, which provides an engineering basis for the detailed stratification and determination of key mechanical indicators of similar deep fill foundations in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The dynamic exploration change curve of the backfill before and after the strong compaction with a compaction energy of 3000 kN·m in the embodiment;

[0046] Figure 2 The dynamic exploration change curve of the backfill before and after the strong compaction with a compaction energy of 6000 kN·m in the embodiment;

[0047] Figure 3 The dynamic exploration change curve of the backfill before and after the strong compaction with a compaction energy of 8000 kN·m in the embodiment;

[0048] Figure 4 The dynamic exploration change curve of the backfill before and after the strong compaction with a compaction energy of 12000 kN·m in the embodiment;

[0049] Figure 5 The dynamic exploration change curve of the backfill before and after the strong compaction with a compaction energy of 15000 kN·m in the embodiment;

[0050] Figure 6 In the embodiment, the tamping energy is 3000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0051] Figure 7 In the embodiment, the tamping energy is 6000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

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

[0053] Fig. 9 In the embodiment, the tamping energy is 12000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0054] Fig.10 In the embodiment, the tamping energy is 15000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0055] Fig.11 In the embodiment, the tamping energy is 3000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0056] Fig.12 In the embodiment, the tamping energy is 6000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0057] Fig.13 In the embodiment, the tamping energy is 8000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0058] Fig.14 In the embodiment, the tamping energy is 12000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0059] Fig.15 In the embodiment, the tamping energy is 15000 kN·m before and after the strong tamping of the backfill The relationship curve with the middle depth h;

[0060] Fig.16 The filling soil in the embodiment and The change relationship curve. DETAILED DESCRIPTION

[0061] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Figures 1 to 16The drawings are all of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The technical solutions shown in the following drawings are specific solutions of the embodiments of the present invention and are not intended to limit the scope of the invention claimed for protection. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] The classification standards of the dynamic compaction energy level E in the present invention 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.

[0063] The embodiment provides a method for analyzing the variation law of the deep fill reinforcement depth and the surface wave velocity. The test analysis is conducted on a specific deep fill site. The specific steps are as follows:

[0064] S1. In the deep fill site, select 5 representative areas where the fill thickness is much greater than the estimated value or empirical value of the reinforcement depth, and conduct a group of heavy dynamic penetration tests and a group of multi-channel transient surface wave tests in each test area; the cone dynamic penetration test uses a 63.5kg drop hammer, and the number of hammer strikes of the probe rod is 10 cm under the hammer energy of a drop distance of 76cm. The dynamic penetration number is corrected for the rod length; the dynamic probe adopts a continuous dynamic probe test with a vertical spacing of 0.1m, and the dynamic probe strikes corresponding to the fill depth of 0.1m, 0.2m, 0.3m, 0.4m, 0.5m, 0.6m...are obtained, and the dynamic probe strikes and depth curves of the fill are drawn. The multi-channel transient surface wave test uses the dispersion characteristics of Rayleigh waves propagating in the medium, and uses Rayleigh surface waves of multiple frequency components excited by artificial seismic sources to find the relationship between wave velocity and frequency. The shear wave propagation velocity at different depths of the stratum is obtained through interpretation, and then the uniformity of the reinforced soil is evaluated; the surface wave test adopts a single-ended excitation method, 12 detectors are arranged, the detector frequency is 4Hz, the track spacing is 1m, the offset distance is 5m, the number of sampling points is 2048 points, and the sampling interval is 250us. The surface wave velocities corresponding to the fill depths of 0.5m, 1m, 1.5m, 2.0m, 2.5m, 3.0m... are obtained through the test.

[0065] S2. For the five test areas mentioned above, five different levels of dynamic compaction construction were carried out, and the dynamic compaction energy levels were 3000kN·m, 6000kN·m, 8000kN·m, 12000kN·m, and 15000kN·m respectively. After the dynamic compaction construction was completed, the site was left to stand for 7 days, the site was leveled, and a 15-20t roller was used for vibration rolling 6-8 times; the dynamic compaction divisions are specifically shown in Table 1:

[0066] Table 1 Dynamic compaction test partition

[0067]

[0068] S3. After step S2 is completed, a set of heavy 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 S;

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

[0070] (1) First, the growth rate δ of the dynamic penetration number before and after dynamic compaction at different depths in each test area of ​​the heavy dynamic penetration test is calculated according to formula ①:

[0071]

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

[0073] ΔN—is the increase in the number of dynamic impacts before and after strong compaction (blows);

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

[0075] N 63.5后 —Number of dynamic strikes after strong compaction (strikes);

[0076] (2) The dynamic penetration test growth rate δ before and after the dynamic tamping at different depths 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 test growth rate δ≥50% is the first reinforcement depth H1 of the test area, that is, the actual reinforcement depth of the test area under the dynamic tamping energy level in the engineering application; the first reinforcement depth H1 is the maximum depth of the dynamic penetration test change curve corresponding to the dynamic penetration test growth rate δ≥50%. When δ≥50%, the soil dynamic penetration test increases significantly, and 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 project. The physical and mechanical indicators of the fill change significantly within this depth range, achieving the established goals; the dynamic penetration test 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 strong compaction energy level corresponding to the test area in engineering applications; the second reinforcement depth H2 is the maximum depth in the dynamic exploration change curve corresponding to the dynamic exploration blow growth rate in the range of 10%≤δ<50%. When 10%≤δ<50%, although the dynamic exploration blow number of soil increases, the increase is limited. At this time, the reinforcement depth is the second reinforcement depth H2, which is the maximum influence depth of strong 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 reserve or further utilization; when 0≤δ<10%, the dynamic exploration blow number of soil increases very little. Considering the deviation of the experimental testing means, the change of this part of the physical and mechanical indicators is negligible.

[0077] Through the above calculation process method, the first reinforcement depth and the 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 soil in the five test areas before and after strong compaction in step S1, and count the surface wave velocity change curves in the range of 0 to the first reinforcement depth H1 before and after strong compaction, and the surface wave velocity change curves in the range of 0 to the first reinforcement depth H1 and the first reinforcement depth H2 before and after strong compaction. 1～ The average value of the surface wave velocity in the second reinforcement depth H2 is calculated, and the surface wave velocity growth rate before and after strong compaction is calculated; the specific calculation process is as follows:

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

[0083] (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 strong 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:

[0084]

[0085]

[0086] According to the above calculation method, the wave velocity growth rates before and after strong compaction are calculated as shown in Table 3.

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

[0088]

[0089] S6. Count the dynamic impact numbers and corresponding surface wave velocities before and after strong compaction at the same positions in the five test areas in step S1, calculate the average value every 2m of vertical depth, establish the relationship curve between the surface wave velocity and the dynamic impact number of the fill, obtain the relationship between the surface wave velocity and the dynamic impact number by fitting, and obtain 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, and the segmentation rule is carried out according to the vertical interval of 2m, such as 0-2m, 2-4m, 4-6m..., and the middle depth h of each depth segment of the dynamic compaction depth range of each dynamic compaction point in each test area is counted, h = n + (n + 2) / 2, where 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) Count the number of dynamic strikes before strong compaction in each depth section in step (1), and calculate the average number of dynamic strikes before strong compaction in the corresponding depth section. The data statistics interval 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 the strong compaction in the depth section of 2-4m is calculated; the average value of the dynamic sounding number before the strong compaction in each depth section of 0-2m, 2-4m, 4-6m... is calculated in turn;

[0092] (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 statistics interval within each depth range is 0.5m; for example, the surface wave depth is 2-4m, and the statistical data are 2.5m, 3.0m, 3.5m, and 4.0m. The average surface wave velocity before the strong compaction in the depth range of 2-4m is calculated, and the average surface wave velocity before the strong compaction in each depth range of 0-2m, 2-4m, 4-6m, etc. is calculated in turn;

[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 section, for example, the average wave velocity and the average surface wave velocity before strong compaction in the depth section of 0-2m correspond to the average wave velocity and the average surface wave velocity before strong compaction at the middle depth of 1m; the average wave velocity and the average surface wave velocity before strong compaction in the depth section of 2-4m correspond to the average wave velocity and the average surface wave velocity before strong compaction at the middle depth of 3m; according to the above rules, the middle depths h of multiple depth sections within the strong compaction depth range of each strong compaction point and the average value of the dynamic strikes before strong compaction in the corresponding depth sections are plotted The curve of

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

[0095] (5) According to the same rules and methods as in step (2), the average number of dynamic strikes after strong compaction in each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average value of the dynamic detection number after compaction of the corresponding depth section are plotted. The curve of

[0096] (6) According to the same rules and methods as in step (3), the average wave velocity after the strong compaction at each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth section are plotted. The curve of

[0097] (7) Based on the statistical data in the above steps, a curve is drawn showing the relationship between the average value of the dynamic strike number before and after the strong compaction and the intermediate depth h, as shown in Figure 2. Figures 6 to 10 As shown in the figure, the relationship curve between the average wave velocity before and after the strong compaction and the intermediate depth h is drawn, as shown in the figure Figures 11 to 15 As shown;

[0098] (8) Draw the same points at the same intermediate depth h in different test areas and The change relationship curve of Fig.16 As shown, curve fitting is performed to establish the logarithmic relationship between the surface wave velocity and the number of dynamic probes, 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 detection (hit)

[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 detections are in a logarithmic relationship, with a high degree of fit. According to the above formula, N 63.5 The surface wave velocity V corresponding to the number of hits is 5, 10, and 20 R are 187, 213, and 239. 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 in the site

[0106]

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

[0108] In summary, the content of the present invention is not limited to the above-mentioned embodiments, and people with insight in the same field can easily propose other embodiments within the technical guiding ideology of the present invention, but such embodiments are all included in the scope of the present invention.

Claims

1. A method for analyzing the variation of the depth and surface wave velocity of deep fill reinforcement by strong tamping, 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, and conduct a set of heavy dynamic penetration tests and a set of multi-channel transient surface wave tests in each test area. The locations of the heavy dynamic penetration tests and multi-channel transient surface wave tests should be consistent. S2: Carry out dynamic compaction construction of different energy levels for at least four test areas in step S1, and the dynamic compaction energy levels include low energy level, medium energy level, high energy level and ultra-high energy level; after the dynamic compaction construction is completed, the site is left to stand for 5 to 10 days, the site is leveled, and a 15 to 20 t roller is used for vibration rolling 6 to 8 times; S3: After the completion of step S2, a group of heavy dynamic penetration tests and a group of multi-channel transient surface wave tests are carried out again for each test area. The test process and test point locations are consistent with the test process and test point locations before strong compaction in step S; S4: Draw the dynamic probing change curves of the backfill before and after the strong compaction in at least four test areas in step S1, calculate the growth rate of the dynamic probing hits before and after the strong 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 strong compaction in each test area according to the size of the growth rate δ of the dynamic probing hits; the specific process is as follows: (1) First, the growth rate δ of the dynamic penetration number before and after dynamic compaction at different depths in each test area of ​​the heavy dynamic penetration test was calculated according to formula ①: In the above formula: δ—is the growth rate of the number of dynamic impacts before and after strong compaction (%); ΔN—is the increase in the number of dynamic impacts before and after strong compaction (blows); N 63.5前 —Number of strikes before dynamic compaction (strikes); N 63.5后 —Number of dynamic strikes after strong compaction (strikes); (2) The dynamic penetration number growth rate δ before and after the 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 of the test area 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 influence 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 soil before and after strong compaction in at least four test areas in step S1, and count the surface wave velocity change curves of the fill soil in the range of 0 to the first reinforcement depth H1 before and after strong compaction, and ... 1～ The average value of the surface wave velocity in the second reinforcement depth H2, and the growth rate of the surface wave velocity before and after the strong compaction are calculated; S6: Count the number of dynamic impacts and the corresponding surface wave velocity before and after strong compaction at the same position of at least four test areas in step S1, calculate the average value every 2m of vertical depth, establish the 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 law of the deep fill reinforcement depth and the surface wave velocity according to claim 1, characterized in that: The thickness of the fill in 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 penetration test adopts a continuous dynamic penetration test with a vertical spacing of 0.1m to obtain the number of dynamic penetration hits corresponding to different fill depths; the multi-channel transient surface wave test obtains the surface wave velocities corresponding to different fill depths with an interval of 0.5m.

3. The method for analyzing the variation law of the deep fill reinforcement depth and the surface wave velocity according to claim 1, characterized in that: The classification standards of the strong 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.

4. The method for analyzing the variation law of the deep fill reinforcement depth and the surface wave velocity according to claim 1, characterized in that: The first reinforcement depth H1 in step S4 is the maximum depth in the dynamic exploration change curve corresponding to the dynamic exploration 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 exploration change curve corresponding to the depth within the range of 10%≤δ<50%. The growth rate of the dynamic exploration number of the soil in this depth range is limited, and the physical and mechanical indicators of the fill change. It is the maximum impact depth of the strong tamping 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 0≤δ<10% are within the error range and can be ignored.

5. The method for analyzing the variation law 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 strong 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 compaction to the first reinforcement depth H1, and calculate the average value Count the surface wave velocity results every 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 Count the surface wave velocity results every 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 strong 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:

6. The method for analyzing the variation law of the deep fill reinforcement depth and the 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 of the fill 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 is segmented, and the segmentation rule is 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 is counted, h = n + (n + 2) / 2, where n = 0, 2, 4, 6 ... n + 2; (2) Count the number of dynamic strikes before strong compaction in each depth section in step (1), and calculate the average number of dynamic strikes before strong compaction in the corresponding depth section. The data statistics interval within each depth segment 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 statistics interval within each depth segment 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 strikes before strong compaction corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the range of the strong compaction depth of each strong compaction point and the average value of the dynamic strikes before strong compaction in the corresponding depth segment are plotted. The curve of the front wave velocity of each depth segment calculated in step (3) is As the front wave velocity of the strong compaction corresponding to the middle depth h of the depth segment, the middle depth h of multiple depth segments within the strong compaction depth range of each strong compaction point and the average wave velocity of the front wave of the strong compaction corresponding to the depth segment are plotted. The curve of (5) According to the same rules and methods as in step (2), the average number of dynamic strikes after strong compaction in each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average value of the dynamic detection number after compaction of the corresponding depth section are plotted. The curve of (6) According to the same rules and methods as in step (3), the average wave velocity after the strong compaction at each depth section is calculated. According to the method in step (4), the middle depth h of multiple depth sections within the range of the compaction depth of each compaction point and the average wave velocity after the compaction of the corresponding depth section are plotted. The curve of (7) Based on the statistical data in the above steps, a curve of the relationship between the average value of the number of dynamic strikes before and after the strong compaction and the intermediate depth h is drawn, and a curve of the relationship between the average value of the wave velocity before and after the strong compaction and the intermediate depth h is drawn; (8) Draw the same points at the same intermediate depth h in different test areas and The curve of the change relationship is fitted to establish the logarithmic relationship between the surface wave velocity and the number of dynamic detections, as shown in formula ④; V R =aln(N 63.5 )+b④ Where: V R —Surface wave velocity (m / s) N 63.5 —Number of dynamic detection (hit) a, b—fitting coefficients (9) Calculate the number of heavy-duty dynamic penetration hammer blows N by using formula ④. 63.5 Surface wave velocity V with 5, 10, and 20 hits R Value, determine the criterion for judging the density of fill in the site.

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