A method and application of predicting the quality of late-stage dynamic compaction construction based on test compaction data in loess areas

Abstract

The present invention provides a method and application for predicting the quality of later strong compaction construction in the loess region based on test compaction data. First, a representative test compaction area in the actual construction site is selected to ensure that the soil quality and geological conditions in the test compaction area are similar to those of the entire actual construction site. The compaction settlement in the single-point test compaction, multi-point test compaction, and full test compaction stages and the dry density data after foundation reinforcement are estimated in advance, and a set of systematic quality assessment and control methods are proposed to assess the quality of later site construction under the test compaction parameters in advance, thereby solving the later quality problems to a great extent. In addition, the method can also improve the foundation elevation control quality of strong compaction construction, estimate the appropriate termination tamping surface elevation of strong compaction construction, make full use of the upper hard foundation soil layer formed by strong compaction, improve the foundation construction quality, and avoid or reduce the post-tamping workload of digging high and filling low in the strong compaction foundation, avoid borrowing or abandoning, improve the environmental protection requirements of the project, and save construction time and cost.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic compaction construction in loess regions, and in particular provides a method for estimating the quality of later dynamic compaction construction according to early test compaction data before large-scale dynamic compaction construction, and adjusting and optimizing dynamic compaction parameters using the estimated later dynamic compaction construction quality. Background Art

[0002] Loess strata have high porosity, are easily compressed and disintegrated, and collapsibility is the most typical engineering characteristic of this stratum. Engineering construction in loess areas usually requires foundation treatment. Dynamic tamping is a commonly used foundation treatment method, which uses the kinetic energy of a falling hammer to repeatedly tamp the foundation, compacting the soil layer within a certain depth below the tamping surface, thereby eliminating the collapsibility of the foundation soil, improving the bearing capacity of the foundation, and reducing the compressibility of the foundation. It has been applied and developed in China for more than 50 years.

[0003] After strong compaction, the foundation soil within the thickness of the foundation treatment is compacted, the pore volume is reduced, and the collapsibility is eliminated, which is specifically manifested as an increase in the dry density of the soil and tamping of the foundation. The greater the increase in the dry density of the foundation soil and the greater the amount of tamping, the deeper the depth of the foundation treatment will be, and the better the reinforcement effect within the scope of the foundation treatment. At present, in the strong compaction construction in the Loess Plateau, the trial compaction stage is mainly to preliminarily determine the feasibility of the strong compaction parameters. Quality control and testing are usually carried out after the strong compaction reinforcement of the entire site is completed. Once unqualified quality problems occur, re-reinforcement is difficult and costly. If an advance estimate can be made based on the tamping amount in the trial compaction stage and the dry density data after foundation reinforcement, and a set of systematic quality assessment and control methods can be proposed, measures can be taken in advance to adjust the strong compaction parameters, which can greatly solve the quality problems in the later stage, and has great application value. Summary of the invention

[0004] The present invention solves the deficiencies in the above-mentioned prior art and provides a method for predicting the quality of later strong compaction construction in advance based on test compaction data in the Loess Plateau, thereby improving the foundation elevation control quality of strong compaction construction, estimating the appropriate termination compaction surface elevation of strong compaction construction, making full use of the upper hard foundation soil layer formed by strong compaction, improving the foundation construction quality, eliminating or reducing the post-compacting workload of digging high and filling low in the strong compaction foundation, avoiding borrowing or abandoning ground, improving the environmental protection requirements of the project, and saving construction period and cost.

[0005] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0006] A method for predicting the quality of later dynamic compaction construction in loess regions based on test compaction data comprises the following steps:

[0007] (1) Select a representative test area in the actual construction site to ensure that the soil and geological conditions in the test area are similar to those of the entire actual construction site;

[0008] (2) Calculate the estimated foundation settlement △ based on the compaction thickness D required by the design drawings and the physical and mechanical indicators of the strata given in the geotechnical engineering investigation report d 估 , preliminarily determine the starting elevation B 1, B 1= B Z + △d 估 , B Z The elevation of the bottom surface of the foundation given in the design drawing;

[0009] (3) Preliminary formulation of test parameters, including rammer weight m、 diameter d , the center distance of tamping points in the tamping point layout method l and row spacing s ;

[0010] (4) Measure and verify the soil parameters in the test tamping area; Measure and verify the compaction thickness in the test tamping area D Optimum moisture content of inner soil layer oh op And the average actual moisture content oh ;

[0011] (5) Determine the optimal number of hits N by single-hole test tamping. After the single-hole test tamping is completed, the actual dry density of the soil layer at the bottom of the tamping pit is tested. r 1dk ;

[0012] (6) Optimal soil moisture content based on the single-hole tamping test results oh op , average actual moisture content oh and the actual dry density of the soil layer at the bottom of the ramming pit r 1dk , determine whether the set conditions are met. If the conditions are not met, adjust the test parameters and repeat the single-hole test until the set conditions are met;

[0013] (7) Multi-hole tamping test;

[0014] (8) Calculate the site settlement △ caused by point tamping based on the results of multi-hole tamping test d 1. Measure the dry density of the bottom soil layer of the porous test pit r jdk ;

[0015] (9) Test tamping by fully tamping and measuring the corresponding tamping sinking amount △ d 2. Dry density of the surface soil layer after full tamping r db , determine the full tamping energy level;

[0016] (10) Site settlement △ caused by test tamping d 实 Average dry density of the bottom of the ramming pit , judge whether it meets the qualified conditions. If it meets the qualified conditions, it is predicted that the quality of the later strong compaction construction meets the design requirements. If it does not meet the qualified conditions, it is predicted that the quality of the later strong compaction construction does not meet the design requirements; where △ d 实 =△ d 1+△ d 2;

[0017] (11) If it is predicted that the quality of the later dynamic compaction construction does not meet the design requirements, continue to adjust the test compaction parameters, reselect the test compaction site, and re-start the test compaction from step (3) until the qualified conditions are met;

[0018] (12) Based on the final settlement △ d 实 , before large-scale dynamic compaction construction, adjust the tamping surface elevation B 2. The test tamping is completed; B 2= B Z + △d 实 ; Carry out large-scale dynamic compaction construction according to the parameters determined by the trial compaction.

[0019] Furthermore, the size of the pilot tamping area in step (1) is not less than 20m×20m and not less than 1 / 100 of the entire actual construction site area; when the actual construction site area is greater than 10,000m 2 For every 8000m 2 One additional test ramming area is set up, and multiple test ramming areas are evenly distributed within the actual construction site.

[0020] Furthermore, the estimated tamping amount of the foundation in step (2) is d 估 Calculate according to the following formula:

[0021] ;

[0022] ;

[0023] In the formula, H i After the surface is cleared, the i The thickness of the soil layer; r imax , r id and G i are the maximum dry density, initial density and specific gravity of soil particles in the i-th layer of soil respectively; lis the compaction coefficient, which is between 0.93 and 0.96 according to the design parameters; H Ground elevation after clearing B 0 and the lower boundary elevation of compaction thickness B X Sure, H = B 0- B X = B 0-( B Z - D ), the first calculation H n The soil layer is only considered H n-1 Height from layer bottom to lower boundary of compaction thickness B X The thickness of the range is calculated in the second iteration only from the elevation B Z + △d 0估 Start counting down.

[0024] Furthermore, the optimal moisture content of the soil layer in the test tamping area in step (4) oh op Determined by heavy compaction test; the average actual moisture content oh Determined by single hole test tamping in step (5).

[0025] Furthermore, step (5) also includes testing the actual dry density of the soil layer at the bottom of the rammed pit after tamping. r 1dk At the same time, take no less than 3 soil samples at different depths on the side wall of the ramming pit to measure the moisture content and then calculate the average actual moisture content according to the following formula: oh :

[0026] ;

[0027] In the formula, oh k is the actual moisture content of the kth measuring point on the wall of the single-point test ramming pit; m is the number of measuring points, m≥3; h1 is the depth of the ramming pit for the single-point test ramming; α is the estimated moisture content increase coefficient of the soil layer below the ramming pit, when D≤8m α= 1. When D>8m, α= 1.5.

[0028] Furthermore, the setting conditions to be met in step (6) are:

[0029] ;

[0030] In the formula, r1max The maximum dry density of the first layer of soil within the compacted reinforcement thickness range; r 1dk If the requirements are not met, adjust the tamping energy and retest the tamping at a single point; if the moisture content is oh If the requirements are not met, measures should be taken or other foundation reinforcement solutions should be selected.

[0031] Furthermore, the site settlement △ caused by the multi-hole test tamping in step (8) d 1 Calculate according to the following formula:

[0032] ;

[0033] Where A is the reinforcement area corresponding to a single ramming pit, which is determined by the distance between the ramming pit and the l and row spacing s Calculate, A= s × l ; h j For the j The depth of the pit, R j and r j Respectively j The pit mouth radius and pit bottom radius of the inverted circular table ramming pit, the number of ramming pits for multi-point trial ramming is a≥6.

[0034] Furthermore, in step (9), the full tamping energy level W is 1 / 3 to 1 / 2 of the single-hole test tamping energy level, and the value of △d2 is between 0.1 and 0.4 m. The actual tamping amount △d2 corresponding to different strong tamping energy levels is greater than the estimated full tamping amount, satisfying the following requirements:

[0035] ;

[0036] In the formula, The average depth of several ramming pits tested; l is the compaction coefficient, when When ≤3m, l Take 0.95, when >3m, l Take 0.93.

[0037] Furthermore, the maximum dry density of the ground surface after full tamping in step (9) is r db satisfy r db ≥0.95 r 1max , otherwise the full tamping energy level should be increased until the above conditions are met.

[0038] Furthermore, in step (10), the site settlement △d实 Average dry density of the bottom of the multi-point test pit The qualifying conditions that should be met simultaneously are:

[0039] ;

[0040] like If the requirements are not met, adjustments can be made by increasing the tamping energy; if △d 实 Does not meet the requirements, through the tamping point center distance l and row spacing s Make adjustments.

[0041] Compared with the prior art, the method and application of predicting the quality of later strong compaction construction in loess regions based on test compaction data provided by the present invention have the following advantages: the present invention adopts the above-mentioned method and application of estimating construction quality based on test compaction data in loess regions, which reflects the actual stratum conditions on site, and makes advance estimates based on the compaction settlement amount in the single-point test compaction, multi-point test compaction, full compaction and test compaction stages, and the dry density data after foundation reinforcement, and proposes a set of systematic quality assessment and control methods to assess the quality of later site construction under the test compaction parameters in advance, and solve the quality problems in the later stage to a great extent. In addition, the method can also improve the foundation elevation control quality of strong compaction construction, estimate the appropriate termination compaction surface elevation of strong compaction construction, make full use of the upper hard foundation soil layer formed by strong compaction, improve the foundation construction quality, and avoid or reduce the post-compacting workload of digging high and filling low in the strong compaction foundation, avoid borrowing or abandoning, improve the environmental protection requirements of the project, and save construction period and cost. Compared with the prior art, the estimation result combined with on-site test compaction data is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of the method for estimating construction quality based on test ramming data;

[0043] Figure 2 A schematic diagram for estimating the site tamping settlement and preliminarily determining the tamping elevation;

[0044] Figure 3 It is a schematic diagram of the arrangement of single-point and multi-point test points;

[0045] Figure 4 This is a schematic diagram of the estimated tamping settlement amount for full tamping reinforcement. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0047] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0048] Example

[0049] See also Figure 1 The present invention provides a method and application for estimating construction quality based on test tamping data in loess regions, comprising the following steps:

[0050] Step 1: Select a representative test area to ensure that the soil and geological conditions of the test area are similar to those of the entire site. The size of the test area should not be less than 10m×10m and not less than 1 / 100 of the entire site area. The site area is greater than 10,000m 2 For every 8000m 2 One additional test ramming area should be set up and several test ramming areas should be evenly distributed within the site.

[0051] Step 2: Estimate the foundation tamping amount △ based on the compaction thickness D required by the design drawings and the physical and mechanical indicators of the stratum given in the geotechnical engineering investigation report d 估 , preliminarily determine the starting elevation B 1. Such as Figure 2 As shown. The foundation tamping amount △ d 估 Calculate according to the following formula:

[0052] ;

[0053] ;

[0054] In the formula, H i After the surface is cleared, the i The thickness of the soil layer; r imax , r id and G iare the maximum dry density, initial density and specific gravity of soil particles in the i-th layer of soil respectively; l is the compaction coefficient, which can be taken between 0.93 and 0.96 according to the design parameters; H Ground elevation after clearing B 0 and the lower boundary elevation of compaction thickness B X Sure, H = B 0- B X = B 0-( B Z - D ),in B Z The bottom elevation of the foundation given in the design; H n The soil layer is only considered H n-1 Height from layer bottom to lower boundary of compaction thickness B X The thickness of the range is calculated in the second iteration only from the elevation B Z + △d 0估 Start counting down.

[0055] The preliminary method for determining the tamping elevation is B 1= B Z + △d 估 .

[0056] Step 3: Preliminary formulation of test parameters, including rammer weight m、 diameter d , the center distance of tamping points in the tamping point layout method l and row spacing s .

[0057] Step 4: Measure and check the compaction thickness of the test area D Average optimum moisture content of inner soil layer oh op And the average actual moisture content oh Optimal moisture content oh op It is mainly determined by heavy compaction test during the geological survey stage to be as close as possible to the impact load form of strong compaction construction. Average actual moisture content oh Determined based on single hole test tamping.

[0058] Step 5: Single hole test tamping. In addition to determining the optimal number of hits N, the actual dry density of the soil layer at the bottom of the tamping pit should also be tested. r 1dk, and take no less than 3 soil samples at different depths on the side wall of the ramming pit to measure the moisture content and then obtain the following formula oh ,like Figure 3 As shown:

[0059] ;

[0060] In the formula, oh k is the actual moisture content of the kth measuring point on the wall of the single-point test ramming pit; m is the number of measuring points, m≥3; h1 is the depth of the ramming pit for the single-point test ramming; α is the estimated moisture content increase coefficient of the soil layer below the ramming pit, when D≤8m α= 1. When D>8m, α= 1.5.

[0061] Step 6. Preliminary judgement of the feasibility of the dynamic compaction method is made based on the results of the single-hole trial compaction test. It is estimated that the subsequent quality should meet the following conditions at the same time.

[0062] ;

[0063] In the formula, r 1max The maximum dry density of the first layer of soil within the compaction and reinforcement thickness range is: oh op and oh The compaction thickness is D The average optimum moisture content and average actual moisture content of the inner soil layer.

[0064] If it is not satisfied, the reasons should be analyzed and measures should be taken. r 1dk If the requirements are not met, adjust the tamping energy and retest the tamping at a single point; if the moisture content is oh If the requirements are not met, measures should be taken or other foundation reinforcement solutions should be selected.

[0065] Step 7: Test tamping with multiple holes.

[0066] Step 8: Calculate the site settlement △ caused by point tamping based on the results of multi-hole test tamping d 1. Measure the dry density of the bottom soil layer of the porous test pit r jdk The site settlement d1 caused by the flooding can be calculated according to the following formula:

[0067] ;

[0068] Where A is the reinforcement area corresponding to a single ramming pit, which can be calculated from the distance between the ramming pits. l and row spacing s Calculate, A= s × l ; hj For the j The depth of the pit, R j and r j Respectively j The pit mouth radius and pit bottom radius of the inverted circular table ramming pit, the number of ramming pits for multi-point trial ramming should be no less than 6.

[0069] Step 9: Full tamping and leveling test tamping is mainly to reinforce the soil filled after leveling within the tamping pit depth and the soil between the tamping pits. Figure 4 Therefore, the reinforcement depth is not less than the ramming pit depth. The corresponding ramming amount △ d 2. Dry density of the surface soil layer after full tamping r db The full tamping energy level W is 1 / 3~1 / 2 of the single-hole test tamping energy level. In general, the value of △d2 is between 0.1~0.4m. The actual tamping amount △d2 corresponding to different strong tamping energy levels should also be greater than the estimated full tamping amount, meeting the following requirements:

[0070] ;

[0071] In the formula, r imax , r id and G i are the maximum dry density, initial dry density and initial soil particle specific gravity of the i-th layer of soil respectively; is the average depth of several ramming pits in the test pit; l is the compaction coefficient, when When ≤3m, l Take 0.95, when >3m, l Take 0.93. When calculating H i It only covers the soil within the depth range of the ramming pit for multi-point trial ramming before the site is leveled.

[0072] Maximum dry density of the ground surface after full tamping r db Should meet r db ≥0.95 r 1max ,in r 1max It is the maximum dry density corresponding to the first layer of soil within the compaction and reinforcement thickness range, otherwise the full compaction energy level should be appropriately increased.

[0073] Step 10: Site settlement caused by test tamping d 实 and the dry density after dynamic compaction reinforcement, and comprehensively estimate the quality of later construction.

[0074] The site settlement caused by the test tamping is: d 实 =△ d 1+△ d 2;

[0075] Based on the test tamping data, the quality of later construction is estimated, and the site settlement △d 实 Average dry density of the bottom of the multi-point test pit The following requirements should be met at the same time:

[0076] .

[0077] Step 11. If the estimated construction quality does not meet the design requirements, adjust the test parameters, reselect the test site, and repeat the test from step 3 until it meets the relevant requirements.

[0078] Site settlement △d caused by test tamping 实 Average dry density of the bottom of the ramming pit from multi-point ramming tests If more than one of the above requirements cannot be met, the reasons should be identified, the compaction design and construction parameters should be adjusted, and the compaction test should be repeated until the requirements are met. If the requirements are not met, adjustments can be made mainly by increasing the tamping energy. 实 If the requirements are not met, the center distance of the tamping point is mainly l and row spacing s Make adjustments.

[0079] Step 12: Based on the final settlement △ d 实 , and adjust the ramming surface elevation before large-scale construction B 2, where B 2= B Z +△ d 实 , B Z The test tamping is completed at the foundation bottom elevation given by the design. Large-scale construction is carried out according to the parameters determined by the test tamping.

[0080] Project Examples

[0081] 1. Basic information of the venue

[0082] The building foundation in a loess area is planned to be reinforced by strong tamping. The site area is 13000m 2 After clearing, the ground elevation is 395.40m, the building foundation elevation is 390.20m, the compaction thickness D is not less than 6m, and the compaction lower boundary elevation is 384.20m. The physical and mechanical indicators of the soil layer below the clearing elevation are shown in the following table:

[0083]

[0084] 2. Specific Applications of the Invention

[0085] (1) The test area is determined to be 15×15m, which is less than 1 / 100 of the site area;

[0086] (2) Compaction coefficient l Take 0.95 to estimate the site settlement △d 估 .

[0087] First calculation:

[0088] ;

[0089] The second iteration calculation:

[0090] .

[0091] (3) The preliminary elevation of the tamping surface is B1=390.2+0.82=391.02m.

[0092] (4) Preliminary formulation of dynamic compaction parameters, taking the dynamic compaction energy level as 5000 kN.m, the compaction spacing as 5.2 m, the row spacing as 2.6 m, and the compaction hammer bottom diameter as d = 2.32 m.

[0093] (5) Single hole test tamping, the number of tamping times was determined to be 8 times. In addition, the measured tamping pit depth was 2.7 m, and the dry density of the soil layer at the bottom of the tamping pit was 1.7 g / cm 3 The actual moisture content of the soil samples at three locations on the pit wall is 16.8%, 17% and 16.9%. Calculate the average actual moisture content oh and oh op :

[0094] .

[0095] (6) Based on the test results of the single-hole test, the feasibility of the dynamic compaction method was preliminarily determined to be feasible:

[0096] .

[0097] (7) Carry out test tamping at multiple tamping points and calculate the site settlement △ d 1. The measured data of 8 ramming pits are as follows:

[0098]

[0099] .

[0100] (8) Carry out full tamping test at 1 / 3 of the spot tamping energy level and measure the tamping settlement after the site is leveled. d2 is 0.32m, compared with the estimated tamping amount after full tamping, the maximum dry density of the ground surface after full tamping r db satisfy r db =1.71>0.95 r 1max =1.65m, full tamping energy level and tamping amount meet the requirements:

[0101] .

[0102] (9) Calculate the tamping amount during the test:

[0103] .

[0104] (10) Calculation of the average dry density of the bottom of the multi-hole test pit :

[0105] .

[0106] (11) Estimate the quality of later construction based on the test tamping data, site settlement △d 实 Average dry density of the bottom of the multi-point test pit All meet the requirements, and it is estimated that the quality of later construction can also meet the requirements:

[0107] .

[0108] (12) According to the determined foundation tamping amount △ d 实 Finally, the tamping height B2 is determined and the tamping test is completed: B2 = B1 + △ d 实 =390.20+0.89=391.19m.

[0109] (13) Based on the final determined elevation of 391.19m for the tamping surface and the parameters determined by the trial tamping, large-scale construction is carried out, which is expected to guarantee the quality of subsequent construction to a large extent.

[0110] The present invention adopts the above-mentioned method and application of estimating construction quality based on the test tamping data in the loess region, which reflects the on-site combination of actual stratum conditions, and makes advance estimates based on the tamping settlement amount in the single-point test tamping, multi-point test tamping, full tamping and test tamping stages and the dry density data after foundation reinforcement, and proposes a set of systematic quality assessment and control methods to assess the quality of later site construction under the test tamping parameters in advance, and solve the later quality problems to a great extent. In addition, this method can also improve the foundation elevation control quality of strong tamping construction, estimate the appropriate termination tamping surface elevation of strong tamping construction, make full use of the upper hard foundation soil layer formed by strong tamping, improve the foundation construction quality, and avoid or reduce the post-tamping workload of strong tamping foundation digging high and filling low, avoid borrowing or abandoning, improve the environmental protection requirements of the project, and save construction period and cost. Compared with the prior art, the estimation result combined with on-site test tamping data is more accurate.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for predicting the quality of later dynamic compaction construction based on test compaction data in loess regions, characterized in that The following steps are involved: (1) Select a representative test area in the actual construction site to ensure that the soil and geological conditions in the test area are similar to those of the entire actual construction site; (2) Calculate the estimated foundation settlement △ based on the compaction thickness D required by the design drawings and the physical and mechanical indicators of the strata given in the geotechnical engineering investigation report d 估 , preliminarily determine the starting elevation B 1, B 1= B Z + △d 估 , B Z The elevation of the bottom surface of the foundation given in the design drawing; (3) Preliminary formulation of test parameters, including rammer weight m、 diameter d , the center distance of tamping points in the tamping point layout method l and row spacing s ; (4) Measure and verify the soil parameters in the test tamping area; Measure and verify the compaction thickness in the test tamping area D Optimal moisture content of inner soil layer ω op And the average actual moisture content ω ; (5) Determine the optimal number of hits N by single-hole test tamping. After the single-hole test tamping is completed, the actual dry density of the soil layer at the bottom of the tamping pit is tested. ρ 1dk ; (6) Optimal soil moisture content based on the single-hole tamping test results ω op , average actual moisture content ω and the actual dry density of the soil layer at the bottom of the ramming pit ρ 1dk , determine whether the set conditions are met. If the set conditions are not met, adjust the test parameters and repeat the single-hole test until the set conditions are met; (7) Multi-hole tamping test; (8) Calculate the site settlement △ caused by point tamping based on the results of multi-hole tamping test d 1. Measure the dry density of the bottom soil layer of the porous test pit ρ jdk ; (9) Test tamping by fully tamping and measuring the corresponding tamping sinking amount △ d 2. Dry density of the surface soil layer after full tamping ρ db , determine the full tamping energy level; (10) Site settlement △ caused by test tamping d 实 Average dry density of the bottom of the ramming pit , judge whether it meets the qualified conditions. If it meets the qualified conditions, it is predicted that the quality of the later strong compaction construction meets the design requirements. If it does not meet the qualified conditions, it is predicted that the quality of the later strong compaction construction does not meet the design requirements; where △ d 实 =△ d 1+△ d 2; (11) If it is predicted that the quality of the later dynamic compaction construction does not meet the design requirements, continue to adjust the test compaction parameters, reselect the test compaction site, and re-start the test compaction from step (3) until the qualified conditions are met; (12) Based on the final settlement △ d 实 , before large-scale dynamic compaction construction, adjust the tamping surface elevation B 2. The test tamping is completed; B 2= B Z + △d 实 ; Carry out large-scale dynamic compaction construction according to the parameters determined by the trial compaction.

2. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: The size of the pilot tamping area in step (1) shall not be less than 20m×20m and shall not be less than 1 / 100 of the actual construction site area. When the actual construction site area is greater than 10,000m 2 For every 8000m 2 One additional test ramming area is set up, and multiple test ramming areas are evenly distributed within the actual construction site.

3. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Estimated tamping amount of foundation in step (2) △ d 估 Calculate according to the following formula: ； ； In the formula, H i After the surface is cleared, the i The thickness of the soil layer; ρ imax , ρ id and G i are the maximum dry density, initial density and specific gravity of soil particles in the i-th layer of soil respectively; λ is the compaction coefficient, which is between 0.93 and 0.96 according to the design parameters; H Ground elevation after clearing B 0 and the lower boundary elevation of compaction thickness B X Sure, H = B 0- B X = B 0-( B Z - D ), the first calculation H n The soil layer is only considered H n-1 Height from layer bottom to lower boundary of compaction thickness B X The thickness of the range is calculated in the second iteration only from the elevation B Z + △d 0估 Start counting down.

4. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Step (4) Optimal moisture content of soil layer in pilot tamping area ω op Determined by heavy compaction test; the average actual moisture content ω Determined by single hole test tamping in step (5).

5. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Step (5) also includes testing the actual dry density of the soil layer at the bottom of the rammed pit after tamping. ρ 1dk At the same time, take no less than 3 soil samples at different depths on the side wall of the ramming pit to measure the moisture content and then calculate the average actual moisture content according to the following formula: ω : ； In the formula, ω k is the actual moisture content of the kth measuring point on the wall of the single-point test ramming pit; m is the number of measuring points, m≥3; h1 is the depth of the ramming pit for the single-point test ramming; α is the estimated moisture content increase coefficient of the soil layer below the ramming pit, when D≤8m α= 1. When D>8m, α= 1.

5.

6. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: The setting conditions in step (6) are: ； In the formula, ρ 1max The maximum dry density of the first layer of soil within the compacted reinforcement thickness range; ρ 1dk If the requirements are not met, adjust the tamping energy and retest the tamping at a single point; if the moisture content is ω If the requirements are not met, measures should be taken or other foundation reinforcement solutions should be selected.

7. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Site settlement caused by multi-hole tamping test in step (8) △ d 1 Calculate according to the following formula: ； Where A is the reinforcement area corresponding to a single ramming pit, which is determined by the distance between the ramming pit and the l and row spacing s Calculate, A= s × l ; h j For the j The depth of the pit, R j and r j Respectively j The pit mouth radius and pit bottom radius of the inverted circular table ramming pit, the number of ramming pits for multi-point trial ramming is a≥6.

8. The method for predicting the quality of late-stage dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: In step (9), the full tamping energy level W is 1 / 3 to 1 / 2 of the single-hole test tamping energy level, and the value of △d2 is between 0.1 and 0.4 m. The actual tamping amount △d2 corresponding to different strong tamping energy levels is greater than the estimated full tamping amount, satisfying the following requirements: ； In the formula, The average depth of several ramming pits tested; λ is the compaction coefficient, when When ≤3m, λ Take 0.95, when >3m, λ Take 0.

93.

9. The method for predicting the quality of later dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Dry density of the surface soil layer after full tamping in step (9) ρ db satisfy ρ db ≥0.95 ρ 1max , otherwise the full tamping energy level should be increased until the above conditions are met.

10. The method for predicting the quality of later dynamic compaction construction in loess regions based on test compaction data according to claim 1, characterized in that: Site settlement △d in step (10) 实 Average dry density of the bottom of the pit after multi-point tamping test The qualifying conditions that should be met simultaneously are: ； like If the requirements are not met, adjustments can be made by increasing the tamping energy; if △d 实 Does not meet the requirements, through the tamping point center distance l and row spacing s Make adjustments.

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