CN117574524B - Method for treating earth-rock dam foundation vibroflotation gravel pile - Google Patents
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Abstract
The invention belongs to the technical field of hydraulic engineering. The invention discloses a method for processing a dam foundation vibroflotation gravel pile of an earth-rock dam, which comprises investigation analysis, model building and simulation analysis, on-site monitoring data analysis, comparison evaluation and dam foundation deformation prediction analysis. The method adopts a mode of combining a numerical simulation calculation analysis result and a field monitoring analysis data analysis result, has reference and contrast to demonstrate the rationality of the change range of the vibroflotation gravel pile, and further provides scientific basis for the operation and maintenance of hydraulic engineering; the invention can provide a more scientific mode and basis for the design and construction of the dam foundation vibroflotation gravel pile for treating the foundation, improves the rationality of the combination of the design and the construction scheme, effectively reduces the uneven settlement of the foundation and ensures the exertion of the benefit of hydraulic engineering.
Description
Technical Field
The invention relates to a method for treating vibroflotation gravel piles, in particular to a method for treating vibroflotation gravel piles of a dam foundation of an earth-rock dam, which is specially used in the technical field of hydraulic engineering.
Background
Generally, earth-rock dams are a type of water retaining structure that is filled (rolled or compacted) with earth and rock material near the dam site, and are also referred to as "local material dams". The earth-rock dam has the advantages of low cost of local materials, strong adaptability to the topography and geological conditions, simple construction technology, rich experience of building the dam and the like, and is widely applied. According to the data of the international committee on dams, more than 800000 dams exist worldwide, wherein the proportion of earth-rock dams is about 83%, and the proportion of earth-rock dams in China is more than 95%.
With the wide application of earth and rockfill dams, a plurality of corresponding complex engineering problems also occur, and some problems can not be solved by means of traditional experience, such as foundation treatment, seepage analysis and the like. Unlike concrete dams, which have a higher adaptability to the foundation, earth-rock dams have a poorer adaptability to the foundation, and therefore, the earth-rock dams have a higher demand on the dam foundation. Before dam construction, the dam foundation needs to be fully reinforced, and statistics data show that the accident of earth and rockfill dam is caused by the dam foundation. Therefore, strengthening the reinforcement treatment research on the dam foundation is a practical requirement for maintaining the engineering safety of the dam.
The vibroflotation gravel pile is a discrete material pile constructed by a vibroflotation method, and is a common foundation treatment method. Specifically, under the action of horizontal vibration of a vibrator and high-pressure water or high-pressure air, loose foundation soil is vibrated and compacted, or after holes are formed in a foundation soil layer, hard coarse particle materials with stable performance are backfilled, and a reinforcing body and surrounding foundation soil are formed through vibration and compaction to form a composite foundation.
In the prior art, 1) a patent with publication number of CN112854144A discloses a construction structure of an earth-rock dam on a deep silt layer and a construction method thereof, and the technical scheme is that the construction structure is formed only by an actual construction mode, and the dam foundation settlement of a reservoir cannot be predicted and simulated without simulation, and the influence on a composite foundation when a gravel pile is processed cannot be judged relatively accurately; 2) The patent with publication number of CN113047236A discloses a method for treating deep soft soil of a soil-rock dam foundation and the soil-rock dam, wherein the method is just to treat the deep soft soil of the soil-rock dam foundation by an actual construction method, and the method can not analyze the dam foundation vibroflotation gravel pile treatment effect under various working states and can not predict and forecast the dam foundation settlement of a reservoir; 3) The patent with publication number of CN112195910A discloses a soft foundation treatment structure and a construction method of an earth-rock dam with reinforced vibroflotation gravel pile and rockfill, the construction method is just a treatment method in actual construction, the model is not combined with actual data, the dam foundation settlement cannot be analyzed and predicted, and the scientific rationality of construction cannot be guaranteed.
In addition, the vibroflotation gravel pile construction usually adopts a single vibroflotation process, and is carried out one by one according to four stages of pore-forming, pore-cleaning, filling and encryption; wherein, pore-forming and pore-cleaning are key procedures for ensuring smooth implementation of the vibroflotation gravel pile; and the filling and encryption are important procedures for ensuring the construction quality of the vibroflotation gravel pile. For silt, mucky soil and low liquid limit clay foundations, due to lower foundation soil bearing capacity, the problems of hole collapse, diameter reduction and the like frequently occur in the hole forming stage of the vibroflotation pile, in order to prevent the premature collapse of the hole wall, filling is often carried out in advance, broken stone is used for protecting the wall, the hole forming and hole forming can be ensured to be carried out continuously, but model analysis and monitoring data analysis are not established, construction is only carried out based on a traditional mode, and due to the fact that the physical process of vibroflotation is relatively complex, theoretical research, numerical models and the like can not meet engineering practice requirements yet. The design, parameter selection and the like in the current practical engineering application are still based on engineering experience and field practice, and the vibroflotation gravel pile can not meet the practical requirements under different practical conditions.
Disclosure of Invention
The invention aims to solve the problems that design, parameter selection and the like in the current practical engineering application are still based on engineering experience and field practice, and applicability of a vibroflotation technology under different conditions still needs to be further discussed and verified, and provides a method for processing a vibroflotation gravel pile of a dam foundation of an earth-rock dam.
The invention realizes the above purpose through the following technical scheme: a method for treating a dam foundation vibroflotation gravel pile of an earth-rock dam comprises the following steps:
step one, investigation and analysis are carried out, data of the dam foundation are collected, and the data are tidied and generalized;
establishing a model and simulating analysis, establishing an actual engineering numerical model by adopting numerical calculation analysis software, and performing a numerical simulation test based on the actual engineering numerical model to obtain a numerical simulation calculation analysis result;
thirdly, analyzing on-site monitoring data, namely performing a single pile vertical bearing capacity test of the vibroflotation gravel pile body and a soil vertical bearing capacity test between vibroflotation gravel pile bodies on the dam foundation by using an on-site monitoring instrument, performing dynamic sounding detection on the vibroflotation gravel pile bodies and an in-situ soil test between vibroflotation gravel pile bodies, monitoring actual engineering deformation, stress and leakage data, performing integral editing on the on-site monitoring data, and analyzing the change rule of the dam foundation according to the integral on-site monitoring data to obtain an on-site monitoring data analysis result;
step four, comparing and evaluating, namely comparing the numerical simulation calculation analysis result with the on-site monitoring data analysis result to prove the rationality of the change range of the vibroflotation gravel pile;
Analyzing dam foundation vibroflotation gravel pile treatment effects under various working conditions by adopting numerical simulation experiments and field monitoring data, determining the range of the vibroflotation gravel pile according to the analyzed composite foundation bearing capacity, deformation and shear strength indexes so as to determine the influence of the change of the range of the vibroflotation gravel pile on the foundation stability, and further predicting and forecasting dam foundation settlement in the reservoir operation process;
wherein, confirm the concrete including to the range of vibroflotation gravel stake:
1) Dividing the numerical simulation calculation analysis result, grading the applied load of the vertical bearing capacity of the single pile of the pile body, obtaining the simulated corresponding pile top settlement according to the model, grading the applied load of the vertical bearing capacity of the soil between the vibroflotation gravel piles, and obtaining the simulated corresponding pile top settlement according to the model;
2) Dividing pile foundation areas detected by pile body dynamic penetration detection, and obtaining simulated corresponding deformation modulus according to the model; dividing a bottom layer of the in-situ test of soil between vibroflotation gravel piles, and obtaining simulated corresponding shear strength, compression modulus and deformation modulus according to a model;
3) And analyzing and comparing the calculation results to determine the range of the vibroflotation gravel pile.
As a further technical scheme of the invention: the data comprises dam foundation soil types, and the dam foundation soil types are divided into:
fourthly, a flood deposit layer is arranged at the bottom of the old river bed of the upper dam line and is 5-20 m thick;
the fourth series of collapse and accumulation layers are distributed on the two sides and the bottom of the old river bed, and the thickness is 5-50 m;
a fourth system is a new system lake sediment accumulation layer I which is distributed on the right bank of the upper dam line and has a thickness of 7-25 m;
a fourth system is a brand new system lake sediment accumulation layer II which is distributed on the left bank of the lower dam line and has a thickness of 21-28 m;
the fourth system is a new system for flushing and depositing a pile layer, which is distributed on a modern riverbed and has a thickness of 5-15 m;
a totally new system collapse pile layer is distributed on the slope and the slope foot parts of two sides, and the thickness is 3-20 m;
and the fourth system is a novel system residual slope lamination layer which is distributed on the left bank slope and the slope toe part and has the thickness of 1.5-13 m.
As a further technical scheme of the invention: the lake sediment accumulation layer I of the fourth system is of a multilayer structure, and the lake sediment accumulation layer I sequentially comprises the following components from bottom to top: a first layer of a lake deposit, a second layer of a lake deposit, a third layer of a lake deposit, a fourth layer of a lake deposit and a fifth layer of a lake deposit;
wherein the first layer of the lake deposit is sand, and the thickness is 9.5-10.0 m; the second layer of the lake sediment is silt, and the thickness is 2.0-2.1 m; the third layer of the lake deposit is powdery clay, and comprises two layers, wherein the lower layer is 3.0-20.0 m thick, and the upper layer is 2.0-8.71 m thick; the fourth layer of the lake deposit is formed by crushing gravel by powdery clay, and the thickness of the crushed gravel is 2.2-2.4 m; the fifth layer of the lake deposit is gravel powder-contained clay, and the thickness is 4.3-7.5 m.
As a further technical scheme of the invention: the lake sediment accumulation layer II of the fourth system is of a multilayer structure, and the lake sediment accumulation layer II is sequentially formed from bottom to top: a first layer of a lake sediment layer II, a second layer of the lake sediment layer II, a third layer of the lake sediment layer II and a fourth layer of the lake sediment layer II;
wherein the first layer of the lake sediment accumulation layer II is powder clay crushed gravel, and the thickness is 1.1-6.0 m; the second layer of the lake sediment accumulation layer II is powdery clay, and the thickness is 13.5-16 m; the third layer of the lake sediment accumulation layer II is powder clay with the thickness of 1.8-3.7 m; the fourth layer of the lake sediment accumulation layer II is silt.
As a further technical scheme of the invention: the fourth system is a novel system flood deposit stacking layer with a multi-layer structure, and comprises a first flood deposit stacking layer and a second flood deposit stacking layer in sequence from bottom to top; wherein the first layer of the flood deposit stacking layer is gravel sand inclusion and has the thickness of 1.5-7 m; the second layer of the flood-flushing accumulation layer is made of sand, egg and gravel, and the thickness of the second layer is 5-13 m.
As a further technical scheme of the invention: the single pile vertical bearing capacity test of the vibroflotation gravel pile body and the inter-pile soil vertical bearing capacity test of the vibroflotation gravel pile specifically comprise:
step S1, loading by adopting an oil jack and a manual oil pump, measuring force by a standard pressure gauge, observing the settlement of a tested pile by adopting a dial indicator, applying loading load in 9 stages, wherein the loading load of the first stage is 2 times of the maximum stage loading, applying the loading load in stages later, measuring and reading the settlement of the tested pile immediately when the first stage loading is applied, and continuously applying the next stage loading if the settlement reaches the standard requirement;
Step S2, when one of the following conditions occurs, loading is terminated:
step S21, the settlement is increased sharply or the soil around the bearing plate is extruded laterally;
step S22, the accumulated settlement of the bearing plate is larger than 6% of the width or diameter of the bearing plate;
s23, when the limit load is not reached, and the maximum loading pressure of the composite foundation and the single pile load test is respectively 2.0 times and 2.5-3.0 times of the design requirement pressure value;
step S24, when one of the conditions of the step S21 or the step S22 is satisfied, the corresponding previous stage load is set as a limit load;
step S3, determining the bearing capacity characteristic value of the single pile:
when the limit load energy on the pressure-sedimentation curve is determined and the value of the limit load energy is not less than 2.0 times of the corresponding proportion limit, taking the proportion limit; when the value is smaller than 2.0 times of the corresponding proportion limit, taking half of the limit load;
step S4, result arrangement:
the deformation modulus of the foundation soil is calculated according to the following formula by the linear deformation section of the load test result P-S curve
E0=ωPb(1-μ 2 )／S
Wherein: e0 is foundation soil deformation modulus; omega is a parameter related to the shape of the bearing plate, the square plate takes 0.886, and the round plate takes 0.785; p is the pressure of a unit area under the bearing plate of the linear deformation section of the P-S curve, and for the slow deformation curve, the value is obtained after the linear fitting of the front 4-5 points; s is the settlement amount corresponding to P; b is the diameter or side length of the bearing plate; μ is the land poisson ratio.
As a further technical scheme of the invention: in step S1, a slow load maintaining method is adopted for loading load, which specifically includes:
step S11, measuring pile top settlement according to 10, 15, 30 and 30 minutes after each stage of load is applied;
step S12, relative stability standard of the measured pile settlement: the pile top settlement amount in each hour is not more than 0.1mm, and the pile top settlement amount appears twice continuously;
s13, when the sedimentation rate of the detected pile top reaches a relatively stable standard, applying a next-stage load;
and S14, unloading stages are half of loading stages, the unloading stages are performed in equal quantity, the rebound quantity is read and recorded at intervals of half an hour for each unloading stage, and the total rebound quantity is read and recorded at intervals of three hours after the whole load is unloaded.
As a further technical scheme of the invention: in step S3, the single pile bearing capacity characteristic value is determined according to the relative deformation value, and specifically includes:
step S31, when the foundation soil is mainly cohesive soil and silt soil, the pressure corresponding to the relative deformation S/b or S/d=0.015 is taken; when the foundation soil is mainly sand, the pressure corresponding to s/b or s/d=0.01 is taken, wherein s is the settlement of the bearing plate in the load test, b and d are the width and the diameter of the bearing plate respectively, and in addition, when the deformation value is more than 2m, the deformation value is calculated according to 2 m;
Step S32, for experienced areas, determining relative deformation values according to local experience, wherein the bearing capacity characteristic value determined according to the relative deformation values is not more than half of the maximum loading pressure.
As a further technical scheme of the invention: in the third step, the vibroflotation gravel pile body dynamic sounding detection and vibroflotation gravel pile inter-pile soil in-situ test specifically comprise:
1) Detecting by adopting an automatic drop hammer device, wherein the maximum deflection of the feeler lever is not more than 2%, the hammering penetration is continuously carried out, and meanwhile, the hammering eccentricity, the tilting and the lateral shaking of the feeler lever are prevented, the perpendicularity of the feeler lever is kept, and the hammering speed is 15-30 beats per minute;
2) Rotating the probe rod for one half turn every 1m of penetration, and rotating the probe rod once every 20cm of penetration when the penetration depth exceeds 10 m;
3) Light dynamic sounding, stopping the test when N10 is more than 100 or the penetrating speed is 15cm and the hammering number is more than 50; heavy power sounding, when N63.5 is more than 50 for three times, stopping the test or changing the heavy power sounding;
4) Rotary drilling is adopted for penetrating the test hole, the water level in the hole is kept higher than the underground water level, when the hole wall is unstable, mud is used for protecting the wall, the hole is drilled to a position 15cm above the test elevation, and the test is carried out after residual soil at the hole bottom is removed;
5) The free drop hammer method with automatic unhook is adopted for hammering, so that the friction force between the guide rod and the hammer is reduced, the eccentricity and lateral shaking during hammering are avoided, the perpendicularity of the connected penetrant, probe rod and guide rod is kept, and the hammering speed is less than 30 beats/min;
6) After the penetrometer is driven into the soil for 15cm, beginning to record the number of hammering 10cm, accumulating the number of hammering 30cm into the standard penetration test number N, recording the actual penetration depth of 50 hits when the number of hammering reaches 50 hits and the penetration depth is less than 30cm, converting into the number N of hammering equivalent to the standard penetration of 30cm, terminating the test, wherein the conversion formula is as follows:
N=30×50/△S
wherein: Δs is the penetration at 50 shots.
As a further technical scheme of the invention: in the fifth step, the calculation of the composite foundation bearing capacity, deformation and shear strength indexes specifically includes:
1) The composite foundation bearing capacity characteristic value comprises:
and according to the following formula, the single pile load test and the test result of soil between piles are calculated and determined:
fspk=mfpk+(1-m)fsk
m=d 0 2 /d e 2
wherein: fspk is a characteristic value of the bearing capacity of the composite foundation, and the unit is kPa; fpk is a bearing capacity characteristic value of the pile body in unit sectional area, and the unit is kPa; fsk is a characteristic value of soil bearing capacity between piles, and the unit is kPa; m is the area replacement rate; d, d 0 For the length of pilesAverage pile diameter in the periphery is m; d, d e The equivalent influence circle diameter of a single pile is given by m; wherein, equilateral triangle cloth piles d e =1.05s; square cloth pile d e =1.13 s; the rectangular cloth piles are arranged on the bottom of the rectangular cloth piles,the method comprises the steps of carrying out a first treatment on the surface of the s, s1 and s2 are respectively the spacing, longitudinal spacing and transverse spacing of the piles, and the unit is m;
2) The shear strength index of the composite foundation is calculated and determined according to the following formula:
tgφsp=muptgφp+（1-mup）tgφs
csp=（1-mup）cs
up=n/1+m(n-1)
wherein: phi sp is the equivalent internal friction angle of the composite soil body; phi P is the internal friction angle of the pile body material; phi s is the internal friction angle of soil between piles; csp is the equivalent cohesive force of the composite soil body, and the unit is kPa; cs is the soil cohesion between piles, and the unit is kPa; up is the stress concentration coefficient; n is pile soil stress ratio, 2-4 is taken when no actual measurement data exists, and a large value is taken when the soil intensity between piles is low and a small value is taken when the soil intensity between piles is high;
3) The compression modulus and the deformation modulus of the composite soil body are determined according to the following method;
compression modulus of composite soil body
Esp=[1+m(n-1)]Es
Wherein: esp is the compression modulus of the composite soil body, and the unit is MPa; es is the compression modulus of soil between piles, and the unit is MPa;
the deformation modulus of the composite soil body is calculated and determined according to the following formula through a single pile and inter-pile soil load test:
Eop=mEp+(1-m)Eo
Wherein: eop is the deformation modulus of the composite soil body, and the unit is MPa; ep is the deformation modulus of the pile body, and the unit is MPa; eo is the deformation modulus of the soil between piles, and the unit is MPa.
The beneficial effects of the invention are as follows:
1) The dam foundation model is established for simulation analysis, the actual engineering numerical model is established by adopting numerical calculation analysis software, and a numerical simulation test is carried out based on the model, so that the reinforcement range of the vibroflotation gravel pile and the concrete construction process can be judged with reference and contrast, the influence (the basis of the dam foundation vibroflotation gravel pile range) on the composite foundation when the gravel pile is processed can be more accurately judged, and the design and construction scientificity of dam foundation reinforcement treatment are improved;
2) Obtaining a change rule of a dam foundation through on-site monitoring data (monitoring data obtained in actual conditions), obtaining an analysis result of the on-site monitoring data based on analysis of the change rule, and simultaneously analyzing dam foundation vibroflotation gravel pile treatment effects under various working conditions by combining with a numerical simulation calculation analysis result to predict and forecast dam foundation settlement in the running process of a reservoir;
3) The invention does not adopt a single numerical simulation calculation analysis result, but adopts a mode of combining the numerical simulation calculation analysis result and the on-site monitoring analysis data analysis result, thereby proving the rationality of the change range of the vibroflotation gravel pile with reference and contrast, and further providing scientific basis for the operation and maintenance of hydraulic engineering;
4) The determination of the range of the vibroflotation gravel pile is based on the division of the numerical simulation analysis result, and the vertical bearing capacity of a single pile of the pile body and the vertical bearing capacity of soil among the vibroflotation gravel piles are respectively applied and respectively graded based on the same model, so that different corresponding pile top settlement amounts can be accurately obtained, and the corresponding reference value and grading value are provided; meanwhile, the same model is adopted to ensure the consistency of foundation stability and the determination of the range of the vibroflotation gravel pile based on the consistency of influencing factors or uncontrollable factors;
5) The invention can provide a more scientific mode and basis for the design and construction of the dam foundation vibroflotation gravel pile for treating the foundation, improves the rationality of the combination of the design and the construction scheme, effectively reduces the uneven settlement of the foundation and ensures the exertion of the benefit of hydraulic engineering.
Drawings
FIG. 1 is a schematic diagram of the overall flow of the present invention;
FIG. 2 is a graph of the strength of load versus settlement of test pile number 863 according to the present invention;
FIG. 3 is a graph showing the displacement dynamics of pile body vertical displacement versus pile load for detecting pile number 863# according to the present invention;
FIG. 4 is a graph of load strength versus settling volume for test pile number 1083# according to the present invention;
FIG. 5 is a dynamic graph of displacement versus pile load for detecting pile body vertical displacement of pile number 1083# according to the present invention;
FIG. 6 is a graph of load strength versus settling volume for test stake number 1422# in accordance with the present invention;
FIG. 7 is a graph showing the displacement dynamics of pile body vertical displacement versus pile load for detecting pile number 1422# according to the present invention;
FIG. 8 is a graph of load intensity versus settling amount for test points 970# and 916# according to the present invention;
FIG. 9 is a graph of the vertical displacement of the pile body versus the displacement dynamics of pile load at detection points 970#, 916 #;
FIG. 10 is a graph of load intensity versus settling between test points 1030#, 977#, 1004# according to the present invention;
FIG. 11 is a graph of the vertical displacement of the pile body versus the displacement dynamics of the pile load between the detection points 1030#, 977#, 1004#, according to the present invention;
FIG. 12 is a graph of load strength versus settling between test points 1562#, 1515#, 1539#, in accordance with the present invention;
fig. 13 is a dynamic graph of pile body vertical displacement versus pile load between test points 1562#, 1515#, 1539#, in accordance with the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment 1, as shown in fig. 1, a method for treating a broken stone pile of a dam foundation of an earth-rock dam by vibroflotation, the method comprising the following steps:
step one, investigation and analysis are carried out, data of the dam foundation are collected, and the data are tidied and summarized.
Investigation analysis includes investigation collection and analysis of data. The related data about the dam foundation (earth-rock dam foundation) is collected by various means such as visiting engineering sites, consulting the data and the like, and the data is sorted and summarized.
Taking a certain reservoir as an example, a normal water retaining building of the reservoir is a silty clay crushed gravel core wall ballast dam, the maximum dam height is 39.5m, and the dam top length is 297m. The dam foundation is provided with vibroflotation gravel piles, the quincuncial arrangement is realized, the pile spacing at the center part of the dam axis is 3m, the pile spacing at the other parts is 4m, the pile diameter is 1m, and the maximum treatment depth is about 29m. Table 1 shows the number and number of piles tested, as follows:
TABLE 1
The data of the collected dam foundation mainly aims at the type of the soil body of the dam foundation, and the type of the soil body of the dam foundation is tidied and generalized. The soil body of the dam foundation is mainly fourth-line collapse, slope and residual slope accumulation layers of silty clay, broken stone, block-broken stone soil, powder clay, solitary block-broken stone soil, river flood accumulation layers of sand, gravel, broken gravel, silty clay, silty soil, sand and the like.
The method is concretely divided into:
(1) Fourthly, a flood deposit layer is arranged at the bottom of the old river bed of the upper dam line and is 5-20 m thick;
(2) The fourth series of collapse and accumulation layers are distributed on the two sides and the bottom of the old river bed, and the thickness is 5-50 m;
(3) And a third system of novel system lake deposit stacking layers I which are distributed on the right bank of the upper dam line and are 7-25 m thick, wherein the layers are of a multi-layer structure and have the characteristic of partial layering, and the layers are sequentially as follows from bottom to top: a first layer of a lake deposit, a second layer of a lake deposit, a third layer of a lake deposit, a fourth layer of a lake deposit and a fifth layer of a lake deposit; wherein the first layer of the lake deposit is sand, and the thickness is 9.5-10.0 m; the second layer of the lake sediment is silt, and the thickness is 2.0-2.1 m; the third layer of the lake deposit is powdery clay, and comprises two layers, wherein the lower layer is 3.0-20.0 m thick, and the upper layer is 2.0-8.71 m thick; the fourth layer of the lake deposit is formed by crushing gravel by powdery clay, and the thickness of the crushed gravel is 2.2-2.4 m; the fifth layer of the lake deposit is gravel powder-contained clay, and the thickness is 4.3-7.5 m;
(4) And a fourth system is a brand new system lake deposition accumulation layer II which is distributed on the left bank of the lower dam line and is 21-28 m thick, wherein the layer is of a multi-layer structure and has a local layering characteristic, and the layers are sequentially as follows from bottom to top: a first layer of a lake sediment layer II, a second layer of the lake sediment layer II, a third layer of the lake sediment layer II and a fourth layer of the lake sediment layer II; wherein the first layer of the lake sediment accumulation layer II is powder clay crushed gravel, and the thickness is 1.1-6.0 m; the second layer of the lake sediment accumulation layer II is powdery clay, and the thickness is 13.5-16 m; the third layer of the lake sediment accumulation layer II is powder clay with the thickness of 1.8-3.7 m; the fourth layer of the lake sediment accumulation layer II is silt;
(5) The fourth system is a new system for flushing and depositing a pile layer, which is distributed on a modern riverbed and has a thickness of 5-15 m; the structure is a multi-layer structure, and a first layer of a flood deposit stacking layer and a second layer of the flood deposit stacking layer are sequentially arranged from bottom to top; wherein the first layer of the flood deposit stacking layer is gravel sand inclusion and has the thickness of 1.5-7 m; the second layer of the flood-flushing accumulation layer is made of sand, egg and gravel, and the thickness of the second layer is 5-13 m;
(6) A totally new system collapse pile layer is distributed on the slope and the slope foot parts of two sides, and the thickness is 3-20 m; the material is distributed on slopes and slope feet of two banks, which are formed by collapse and accumulation of recent bank slopes, the left bank and the right bank are distributed, the material composition surface layer is formed by crushing gravel by powdery clay, and the lower part is formed by solitary stone and block gravel soil, so that the structure can be loose or slightly dense;
(7) And the fourth system is a novel system residual slope laminate which is distributed at the left bank slope and the slope toe part and is formed by accumulating recent bank slope residual slope laminate with the thickness of 1.5-13 m, wherein the material composition surface layer is formed by crushing gravel by powdery clay, and the surface layer is provided with a plurality of solitary stones.
Establishing a model and simulating analysis, establishing an actual engineering numerical model by using numerical calculation analysis software, performing a numerical simulation test based on the actual engineering numerical model, performing numerical simulation calculation in combination with the actual situation, and performing analysis and evaluation on the calculation result to obtain a numerical simulation calculation analysis result.
The simulation analysis comprises the simulation analysis of foundation treatment effect before the range of the vibroflotation gravel pile is changed and the simulation analysis of foundation treatment effect after the range of the vibroflotation gravel pile is changed, and the comparison and evaluation of rationality of the range of the vibroflotation gravel pile are carried out.
And thirdly, analyzing on-site monitoring data, namely performing vibroflotation gravel pile body single pile vertical bearing capacity test and vibroflotation gravel pile inter-pile soil vertical bearing capacity test on the dam foundation by using an on-site monitoring instrument, performing vibroflotation gravel pile body dynamic sounding detection on the vibroflotation gravel pile body and performing in-situ soil test on the vibroflotation gravel pile inter-pile, monitoring actual engineering deformation, stress and leakage data, performing integral editing on the on-site monitoring data, and analyzing the change rule of the dam foundation according to the integral on-site monitoring data to obtain an on-site monitoring data analysis result.
The soil and rock dam foundation carries out the vertical bearing capacity test of single pile of vibroflotation gravel pile body and the vertical bearing capacity test of soil between vibroflotation gravel pile specifically comprises:
1. according to the test, an oil jack is matched with a manual oil pump for loading, a standard pressure gauge with 0.4-level precision is used for measuring force, a wide-range dial indicator is used for observing the sedimentation of a tested pile, the test load is applied in 9 levels, the first-level applied load is 2 times of the maximum level load, the test load is applied in steps later, the sedimentation quantity of a pile is measured immediately when the first-level load is applied, the sedimentation reaches the standard requirement, and the next-level load can be continuously applied;
The test adopts a slow load maintaining method, and specifically comprises the following steps:
1) The pile top settlement amount is measured at 10, 15, 30 and 30 minutes after each stage of load application (the time is referred to as, every 10 minutes, every 15 minutes, every 30 minutes, and every 30 minutes);
2) Relative stability standard for tested pile settlement: pile top settlement within each hour is not more than 0.1mm and occurs twice in succession (calculated as settlement observations every 30 minutes for three successive times of 1.5h from 30 minutes after the classification load is applied);
3) When the sedimentation rate of the pile top (the pile to be measured) reaches a relatively stable standard, the next stage of load is applied;
4) The unloading stage number can be half of the loading stage number, the unloading stage number is equal, the interval is half an hour, the rebound quantity is read and recorded, and the total rebound quantity is read and recorded three hours after the whole load is unloaded;
FIG. 3 shows a dynamic displacement curve of pile body vertical displacement-pile load for detecting pile number 863# for ten total stages of loading, ten total points (1-10); similarly, fig. 5 is a graph showing the displacement dynamics of the vertical displacement of the pile body and the pile load, fig. 7 is a graph showing the displacement dynamics of the vertical displacement of the pile body and the pile load, fig. 9 is a graph showing the displacement dynamics of the vertical displacement of the pile body and the pile load, fig. 11 is a graph showing the displacement dynamics of the vertical displacement of the pile body and the pile load, between the detection points 1030#, 977#, and 1004#, and fig. 13 is a graph showing the displacement dynamics of the vertical displacement of the pile body and the pile load, between the detection points 1562#, 1515#, and 1539#. The specific load classification is known from table 2.
The load classification conditions of the soil-rock dam foundation for the vibroflotation gravel pile body single pile vertical bearing capacity test are shown in the following table 2 and table 3, the table 2 is a load classification condition table of the soil-rock dam foundation for the vibroflotation gravel pile body single pile vertical bearing capacity test, and the table 3 is a load classification condition table of the soil vertical bearing capacity test between vibroflotation gravel piles.
TABLE 2
TABLE 3 Table 3
2. The loading may be terminated when one of the following occurs:
1) The settlement increases sharply or the soil around the bearing plate is extruded obviously sideways;
2) The accumulated settlement of the bearing plate is larger than 6% of the width or diameter of the bearing plate;
3) When the limit load is not reached, the maximum loading pressure of the composite foundation and the single pile load test is respectively 2.0 times and 2.5-3.0 times of the design requirement pressure value;
when one of the two conditions is satisfied, the corresponding previous stage load is set as a limit load;
3. determination of bearing capacity characteristic value of single pile
When the limit load energy on the pressure-sedimentation curve is determined and the value is not less than 2.0 times the corresponding proportion limit, the proportion limit is taken; when the value is less than 2.0 times the corresponding proportional limit, half of the limit load can be taken;
determination of relative deformation values
1) When the foundation soil is mainly cohesive soil and silt, the pressure corresponding to the relative deformation s/b or s/d=0.015 can be taken; when the foundation soil is mainly sand, the pressure corresponding to s/b or s/d=0.01 (s is the settlement amount of the bearing plate in the load test, b and d are the width and the diameter of the bearing plate respectively, and when the value is more than 2m, the value is calculated as 2 m).
2) For experienced areas, the relative deformation value can also be determined empirically locally, and the characteristic bearing capacity value determined according to the relative deformation value should not be greater than half of the maximum loading pressure;
4. result arrangement
The deformation modulus of the foundation soil is calculated according to the following formula by the linear deformation section of the load test result P-S curve
E0=ωPb(1-μ 2 )／S
Wherein: e0 is foundation soil deformation modulus (without limitation); omega is a parameter related to the shape of the bearing plate, the square plate takes 0.886, and the round plate takes 0.785; p is the pressure (load intensity) of a unit area under a linear deformation section bearing plate of a P-S (load intensity-settlement) curve, and for a slow deformation curve, the value is generally obtained after linear fitting is carried out on the front 4-5 points; s is the settlement amount corresponding to P; b is the diameter or side length (m) of the bearing plate; mu is the poisson ratio of the soil (clay 0.42, silty clay 0.38, silty soil 0.35, sand 0.30, gravel 0.27).
The dynamic sounding detection of the pile body of the vibroflotation gravel pile and the in-situ test of soil among the vibroflotation gravel pile specifically comprise:
1) Detecting by adopting an automatic drop hammer device, wherein the maximum deflection of the feeler lever is not more than 2%, and hammering penetration is continuously carried out; meanwhile, the hammering eccentricity, the inclination and the lateral shaking of the probe rod are prevented, and the perpendicularity of the probe rod is kept; the hammering speed is 15-30 beats per minute;
2) The probe rod is rotated for one half turn every time 1m is penetrated, and the probe rod is preferably rotated once every time 20cm is penetrated when the penetration depth exceeds 10 m;
3) For light dynamic sounding, when N10 is more than 100 or the number of the hammering of 15cm is more than 50, the test can be stopped; for heavy power sounding, when N63.5 is more than 50 for three times continuously, the test can be stopped or extra heavy power sounding can be used instead;
4) Rotary drilling is adopted for penetrating the test hole, the water level in the hole is kept slightly higher than the underground water level, when the hole wall is unstable, mud can be used for protecting the wall, the hole is drilled to a position 15cm above the test elevation, and the test is carried out after the residual soil at the hole bottom is removed;
5) The free drop hammer method with automatic unhook is adopted for hammering, the friction force between the guide rod and the hammer is reduced, the eccentric and lateral shaking during hammering are avoided, the perpendicularity of the connected penetrant, the probe rod and the guide rod is kept, and the hammering speed is less than 30 beats/min;
6) After the penetrometer is driven into the soil for 15cm, beginning to record the number of hammering 10cm, accumulating the number of hammering 30cm into the number of hammering N of the standard penetration test, when the number of hammering reaches 50 and the depth of penetration does not reach 30cm, recording the depth of Chen Guanru of 50, converting into the number of hammering N of the standard penetration test corresponding to 30cm according to the following formula, and terminating the test;
N=30×50/△S
Wherein: ΔS-penetration at 50 shots (cm).
Table 4 is a standard penetration test equipment specification table, and Table 5 is a table of results of pile compactness detection of the vibroflotation gravel pile.
TABLE 4 Table 4
TABLE 5
Table 6 is one of the results of the in-situ test of soil between vibroflotation gravel piles, table 7 is two of the results of the in-situ test of soil between vibroflotation gravel piles, and table 8 is three of the results of the in-situ test of soil between vibroflotation gravel piles, as shown below.
TABLE 6
TABLE 7
TABLE 8
And step four, comparing and evaluating, namely comparing the numerical simulation calculation analysis result with the on-site monitoring data analysis result, and fully proving and analyzing the rationality of the change of the range of the vibroflotation gravel pile.
Analyzing dam foundation vibroflotation gravel pile treatment effects under various working conditions by adopting numerical simulation experiments and field monitoring data, determining the range of the vibroflotation gravel pile according to the analyzed composite foundation bearing capacity, deformation and shear strength indexes so as to determine the influence of the change of the range of the vibroflotation gravel pile on the foundation stability, and further predicting and forecasting dam foundation settlement in the reservoir operation process;
wherein, confirm the concrete including to the range of vibroflotation gravel stake:
1) Dividing the numerical simulation calculation analysis result, grading the applied load of the vertical bearing capacity of the single pile of the pile body, obtaining the simulated corresponding pile top settlement according to the model, grading the applied load of the vertical bearing capacity of the soil between the vibroflotation gravel piles, and obtaining the simulated corresponding pile top settlement according to the model;
2) Dividing pile foundation areas detected by pile body dynamic penetration detection, and obtaining simulated corresponding deformation modulus according to the model; dividing a bottom layer of the in-situ test of soil between vibroflotation gravel piles, and obtaining simulated corresponding shear strength, compression modulus and deformation modulus according to a model;
3) And analyzing and comparing the calculation results to determine the range of the vibroflotation gravel pile.
The calculation of the composite foundation bearing capacity, deformation and shear strength indexes specifically comprises the following steps:
1) The characteristic value of the bearing capacity of the composite foundation is determined according to the following formula:
and according to the following formula, the single pile load test and the test result of soil between piles are calculated and determined:
fspk=mfpk+(1-m)fsk
m=d 0 2 /d e 2
wherein: fspk is a characteristic value of the bearing capacity of the composite foundation, and the unit is kPa; fpk is a bearing capacity characteristic value of the pile body in unit sectional area, and the unit is kPa; fsk is a characteristic value of soil bearing capacity between piles, and the unit is kPa; m is the area replacement rate; d, d 0 The unit is m (meters) which is the average pile diameter in the pile length range; d, d e The equivalent influence circle diameter of a single pile is given by m; wherein, equilateral triangle cloth piles d e =1.05s; square cloth pile d e =1.13 s; the rectangular cloth piles are arranged on the bottom of the rectangular cloth piles,the method comprises the steps of carrying out a first treatment on the surface of the s, s1 and s2 are respectively the spacing, longitudinal spacing and transverse spacing of the piles, and the unit is m;
2) The shear strength index of the composite foundation is calculated and determined according to the following formula:
tgφsp=muptgφp+（1-mup）tgφs
csp=（1-mup）cs
up=n/1+m(n-1)
wherein: phi sp is the equivalent internal friction angle of the composite soil body; phi P is the internal friction angle of the pile body material; phi s is the internal friction angle of soil between piles; csp is the equivalent cohesive force of the composite soil body, and the unit is kPa; cs is the soil cohesion between piles, and the unit is kPa; up is the stress concentration coefficient; n is pile soil stress ratio, 2-4 is taken when no actual measurement data exists, and a large value is taken when the soil intensity between piles is low and a small value is taken when the soil intensity between piles is high;
3) The compression modulus and the deformation modulus of the composite soil body can be determined according to the following method;
compression modulus of composite soil body
Esp=[1+m(n-1)]Es
Wherein: esp is the compression modulus of the composite soil body, and the unit is MPa; es is the compression modulus of soil between piles, and the unit is MPa;
the deformation modulus of the composite soil body is calculated and determined according to the following formula through a single pile and inter-pile soil load test:
Eop=mEp+(1-m)Eo
Wherein: eop is the deformation modulus of the composite soil body, and the unit is MPa; ep is the deformation modulus of the pile body, and the unit is MPa; eo is the deformation modulus of the soil between piles, and the unit is MPa.
Working principle: on the basis of numerical simulation calculation, fuzzy mathematics and artificial intelligence methods are adopted to study the influence of the vibroflotation gravel pile reinforcing range and the construction process on the bearing capacity of the composite foundation, the basis for determining the dam foundation vibroflotation gravel pile range is provided, the construction process is further optimized, the blindness of design and construction is reduced, and the scientificity of dam foundation reinforcing treatment design and construction is improved. And a numerical simulation test and field monitoring data are adopted to analyze the dam foundation vibroflotation gravel pile treatment effect under various working states, predict and forecast dam foundation settlement in the reservoir operation process, provide scientific basis for hydraulic engineering operation and maintenance, prolong the hydraulic engineering life cycle and ensure the exertion of hydraulic engineering benefits.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (10)
1. The method for treating the earth-rock dam foundation vibroflotation gravel pile is characterized by comprising the following steps of:
step one, investigation and analysis are carried out, data of the dam foundation are collected, and the data are tidied and generalized;
establishing a model and simulating analysis, establishing an actual engineering numerical model by adopting numerical calculation analysis software, and performing a numerical simulation test based on the actual engineering numerical model to obtain a numerical simulation calculation analysis result;
thirdly, analyzing on-site monitoring data, namely performing a single pile vertical bearing capacity test of the vibroflotation gravel pile body and a soil vertical bearing capacity test between vibroflotation gravel pile bodies on the dam foundation by using an on-site monitoring instrument, performing dynamic sounding detection on the vibroflotation gravel pile bodies and an in-situ soil test between vibroflotation gravel pile bodies, monitoring actual engineering deformation, stress and leakage data, performing integral editing on the on-site monitoring data, and analyzing the change rule of the dam foundation according to the integral on-site monitoring data to obtain an on-site monitoring data analysis result;
Step four, comparing and evaluating, namely comparing the numerical simulation calculation analysis result with the on-site monitoring data analysis result to prove the rationality of the change range of the vibroflotation gravel pile;
analyzing dam foundation vibroflotation gravel pile treatment effects under various working conditions by adopting numerical simulation experiments and field monitoring data, determining the range of the vibroflotation gravel pile according to the analyzed composite foundation bearing capacity, deformation and shear strength indexes so as to determine the influence of the change of the range of the vibroflotation gravel pile on the foundation stability, and further predicting and forecasting dam foundation settlement in the reservoir operation process;
wherein, confirm the concrete including to the range of vibroflotation gravel stake:
1) Dividing the numerical simulation calculation analysis result, grading the applied load of the vertical bearing capacity of the single pile of the pile body, obtaining the simulated corresponding pile top settlement according to the model, grading the applied load of the vertical bearing capacity of the soil between the vibroflotation gravel piles, and obtaining the simulated corresponding pile top settlement according to the model;
2) Dividing pile foundation areas detected by pile body dynamic penetration detection, and obtaining simulated corresponding deformation modulus according to the model; dividing a bottom layer of the in-situ test of soil between vibroflotation gravel piles, and obtaining simulated corresponding shear strength, compression modulus and deformation modulus according to a model;
3) And analyzing and comparing the calculation results to determine the range of the vibroflotation gravel pile.
2. The method according to claim 1, wherein the first step specifically comprises: the data comprises dam foundation soil types, and the dam foundation soil types are divided into:
fourthly, a flood deposit layer is arranged at the bottom of the old river bed of the upper dam line and is 5-20 m thick;
the fourth series of collapse and accumulation layers are distributed on the two sides and the bottom of the old river bed, and the thickness is 5-50 m;
a fourth system is a new system lake sediment accumulation layer I which is distributed on the right bank of the upper dam line and has a thickness of 7-25 m;
a fourth system is a brand new system lake sediment accumulation layer II which is distributed on the left bank of the lower dam line and has a thickness of 21-28 m;
the fourth system is a new system for flushing and depositing a pile layer, which is distributed on a modern riverbed and has a thickness of 5-15 m;
a totally new system collapse pile layer is distributed on the slope and the slope foot parts of two sides, and the thickness is 3-20 m;
and the fourth system is a novel system residual slope lamination layer which is distributed on the left bank slope and the slope toe part and has the thickness of 1.5-13 m.
3. A processing method according to claim 2, characterized in that: the lake sediment accumulation layer I of the fourth system is of a multilayer structure, and the lake sediment accumulation layer I sequentially comprises the following components from bottom to top: a first layer of a lake deposit, a second layer of a lake deposit, a third layer of a lake deposit, a fourth layer of a lake deposit and a fifth layer of a lake deposit;
Wherein the first layer of the lake deposit is sand, and the thickness is 9.5-10.0 m; the second layer of the lake sediment is silt, and the thickness is 2.0-2.1 m; the third layer of the lake deposit is powdery clay, and comprises two layers, wherein the lower layer is 3.0-20.0 m thick, and the upper layer is 2.0-8.71 m thick; the fourth layer of the lake deposit is formed by crushing gravel by powdery clay, and the thickness of the crushed gravel is 2.2-2.4 m; the fifth layer of the lake deposit is gravel powder-contained clay, and the thickness is 4.3-7.5 m.
4. A processing method according to claim 2, characterized in that: the lake sediment accumulation layer II of the fourth system is of a multilayer structure, and the lake sediment accumulation layer II is sequentially formed from bottom to top: a first layer of a lake sediment layer II, a second layer of the lake sediment layer II, a third layer of the lake sediment layer II and a fourth layer of the lake sediment layer II;
wherein the first layer of the lake sediment accumulation layer II is powder clay crushed gravel, and the thickness is 1.1-6.0 m; the second layer of the lake sediment accumulation layer II is powdery clay, and the thickness is 13.5-16 m; the third layer of the lake sediment accumulation layer II is powder clay with the thickness of 1.8-3.7 m; the fourth layer of the lake sediment accumulation layer II is silt.
5. A processing method according to claim 2, characterized in that: the fourth system is a novel system flood deposit stacking layer with a multi-layer structure, and comprises a first flood deposit stacking layer and a second flood deposit stacking layer in sequence from bottom to top; wherein the first layer of the flood deposit stacking layer is gravel sand inclusion and has the thickness of 1.5-7 m; the second layer of the flood-flushing accumulation layer is made of sand, egg and gravel, and the thickness of the second layer is 5-13 m.
6. A processing method according to claim 1, characterized in that: in the third step, the single pile vertical bearing capacity test of the vibroflotation gravel pile body and the soil vertical bearing capacity test between vibroflotation gravel piles specifically comprise:
step S1, loading by adopting an oil jack and a manual oil pump, measuring force by a standard pressure gauge, observing the settlement of a tested pile by adopting a dial indicator, applying loading load in 9 stages, wherein the loading load of the first stage is 2 times of the maximum stage loading, applying the loading load in stages later, measuring and reading the settlement of the tested pile immediately when the first stage loading is applied, and continuously applying the next stage loading if the settlement reaches the standard requirement;
step S2, when one of the following conditions occurs, loading is terminated:
step S21, the settlement is increased sharply or the soil around the bearing plate is extruded laterally;
step S22, the accumulated settlement of the bearing plate is larger than 6% of the width or diameter of the bearing plate;
s23, when the limit load is not reached, and the maximum loading pressure of the composite foundation and the single pile load test is respectively 2.0 times and 2.5-3.0 times of the design requirement pressure value;
step S24, when one of the conditions of the step S21 or the step S22 is satisfied, the corresponding previous stage load is set as a limit load;
Step S3, determining the bearing capacity characteristic value of the single pile:
when the limit load energy on the pressure-sedimentation curve is determined and the value of the limit load energy is not less than 2.0 times of the corresponding proportion limit, taking the proportion limit; when the value is smaller than 2.0 times of the corresponding proportion limit, taking half of the limit load;
step S4, result arrangement:
the deformation modulus of the foundation soil is calculated according to the following formula by the linear deformation section of the load test result P-S curve
E0=ωPb(1-μ 2 )／S
Wherein: e0 is foundation soil deformation modulus; omega is a parameter related to the shape of the bearing plate, the square plate takes 0.886, and the round plate takes 0.785; p is the pressure of a unit area under the bearing plate of the linear deformation section of the P-S curve, and for the slow deformation curve, the value is obtained after the linear fitting of the front 4-5 points; s is the settlement amount corresponding to P; b is the diameter or side length of the bearing plate; μ is the land poisson ratio.
7. The processing method according to claim 6, characterized in that: in step S1, a slow load maintaining method is adopted for loading load, which specifically includes:
step S11, measuring pile top settlement according to 10, 15, 30 and 30 minutes after each stage of load is applied;
step S12, relative stability standard of the measured pile settlement: the pile top settlement amount in each hour is not more than 0.1mm, and the pile top settlement amount appears twice continuously;
S13, when the sedimentation rate of the detected pile top reaches a relatively stable standard, applying a next-stage load;
and S14, unloading stages are half of loading stages, the unloading stages are performed in equal quantity, the rebound quantity is read and recorded at intervals of half an hour for each unloading stage, and the total rebound quantity is read and recorded at intervals of three hours after the whole load is unloaded.
8. The processing method according to claim 6, characterized in that: in step S3, the single pile bearing capacity characteristic value is determined according to the relative deformation value, and specifically includes:
step S31, when the foundation soil is mainly cohesive soil and silt soil, taking the pressure corresponding to the relative deformation S/b or S/d=0.015; taking the pressure corresponding to s/b or s/d=0.01 when the foundation soil is mainly sandy soil, wherein s is the settlement of the bearing plate of the load test, b and d are the width and the diameter of the bearing plate respectively, and in addition, calculating according to 2m when the deformation value is more than 2 m;
step S32, for experienced areas, determining relative deformation values according to local experience, wherein the bearing capacity characteristic value determined according to the relative deformation values is not more than half of the maximum loading pressure.
9. A processing method according to claim 1, characterized in that: in the third step, the vibroflotation gravel pile body dynamic sounding detection and vibroflotation gravel pile inter-pile soil in-situ test specifically comprise:
1) Detecting by adopting an automatic drop hammer device, wherein the maximum deflection of the feeler lever is not more than 2%, and the hammering penetration is continuously carried out, so that the hammering eccentricity, the tilting and the lateral shaking of the feeler lever are prevented, the perpendicularity of the feeler lever is kept, and the hammering speed is 15-30 beats per minute;
2) Rotating the probe rod for one half turn every 1m of penetration, and rotating the probe rod once every 20cm of penetration when the penetration depth exceeds 10 m;
3) Light dynamic sounding, stopping the test when N10 is more than 100 or the penetrating speed is 15cm and the hammering number is more than 50; heavy power sounding, when N63.5 is more than 50 for three times, stopping the test or changing the heavy power sounding;
4) Rotary drilling is adopted for penetrating the test hole, the water level in the hole is kept higher than the underground water level, when the hole wall is unstable, mud is used for protecting the wall, the hole is drilled to a position 15cm above the test elevation, and the test is carried out after residual soil at the hole bottom is removed;
5) The free drop hammer method with automatic unhook is adopted for hammering, so that the friction force between the guide rod and the hammer is reduced, the eccentricity and lateral shaking during hammering are avoided, the perpendicularity of the connected penetrant, probe rod and guide rod is kept, and the hammering speed is less than 30 beats/min;
6) After the penetrometer is driven into the soil for 15cm, beginning to record the number of hammering 10cm, accumulating the number of hammering 30cm into the standard penetration test number N, recording the actual penetration depth of 50 hits when the number of hammering reaches 50 hits and the penetration depth is less than 30cm, converting into the number N of hammering equivalent to the standard penetration of 30cm, terminating the test, wherein the conversion formula is as follows:
N=30×50/△S
Wherein: Δs is the penetration at 50 shots.
10. A processing method according to claim 1, characterized in that: in the fifth step, the calculation of the composite foundation bearing capacity, deformation and shear strength indexes specifically includes:
1) The composite foundation bearing capacity characteristic value comprises:
and according to the following formula, the single pile load test and the test result of soil between piles are calculated and determined:
fspk=mfpk+(1-m)fsk
m=d 0 2 /d e 2
wherein: fspk is a characteristic value of the bearing capacity of the composite foundation, and the unit is kPa; fpk is a bearing capacity characteristic value of the pile body in unit sectional area, and the unit is kPa; fsk is a characteristic value of soil bearing capacity between piles, and the unit is kPa; m is the area replacement rate; d, d 0 The unit is m, which is the average pile diameter in the pile length range; d, d e The equivalent influence circle diameter of a single pile is given by m; wherein, equilateral triangle cloth piles d e =1.05s; square cloth pile d e =1.13 s; the rectangular cloth piles are arranged on the bottom of the rectangular cloth piles,the method comprises the steps of carrying out a first treatment on the surface of the s, s1 and s2 are respectively the spacing, longitudinal spacing and transverse spacing of the piles, and the unit is m;
2) The shear strength index of the composite foundation is calculated and determined according to the following formula:
tgφsp=muptgφp+（1-mup）tgφs
csp=（1-mup）cs
up=n/1+m(n-1)
wherein: phi sp is the equivalent internal friction angle of the composite soil body; phi P is the internal friction angle of the pile body material; phi s is the internal friction angle of soil between piles; csp is the equivalent cohesive force of the composite soil body, and the unit is kPa; cs is the soil cohesion between piles, and the unit is kPa; up is the stress concentration coefficient; n is pile soil stress ratio, 2-4 is taken when no actual measurement data exists, and a large value is taken when the soil intensity between piles is low and a small value is taken when the soil intensity between piles is high;
3) The compression modulus and the deformation modulus of the composite soil body are determined according to the following method;
compression modulus of composite soil body
Esp=[1+m(n-1)]Es
Wherein: esp is the compression modulus of the composite soil body, and the unit is MPa; es is the compression modulus of soil between piles, and the unit is MPa;
the deformation modulus of the composite soil body is calculated and determined according to the following formula through a single pile and inter-pile soil load test:
Eop=mEp+(1-m)Eo
wherein: eop is the deformation modulus of the composite soil body, and the unit is MPa; ep is the deformation modulus of the pile body, and the unit is MPa; eo is the deformation modulus of the soil between piles, and the unit is MPa.
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