CN109255191B - Method for quantitatively calculating settlement generated after preloading of railway subgrade - Google Patents
Method for quantitatively calculating settlement generated after preloading of railway subgrade Download PDFInfo
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Abstract
The invention belongs to the technical field of railway roadbed construction, and particularly relates to a method for quantitatively calculating the settlement generated after preloading of a railway roadbed, 1) determining the relationship between the settlement S and the thickness h of foundation soil by a layered summation method; 2) making a longitudinal section diagram of the basement geology; 3) establishing a settlement S calculation formula model according to the relation between the settlement S and the thickness h of the base soil; 4) actually measuring the settlement S of the settlement observation section; 5) analyzing the thickness h of the foundation soil at the settlement observation section; 6) carrying out nonlinear fitting on the calculation formula model by using the data of the settlement S and the thickness h of the base soil to obtain a model coefficient; 7) and calculating the settlement of the railway roadbed in the adjacent area or the similar geological area after the preloading through a calculation formula model of the model coefficient and the settlement of the railway roadbed during the preloading. The method for quantitatively calculating the settlement can be used for acquiring the settlement at the position close to the observation-free section and making up the data loss of the sampling interval.
Description
Technical Field
The invention belongs to the technical field of railway roadbed construction, and particularly relates to a method for quantitatively calculating settlement of railway roadbed foundation soil after preloading according to the thickness of the railway roadbed foundation soil.
Background
The high-speed railway is high in running speed of the train, smoothness of the track is the key for optimizing the wheel track effect and is one of important factors for ensuring driving safety and passenger comfort, in order to operate safely and stably, the high-speed railway has strict requirements on the leveling state of the track surface, and settlement deformation of a structure has direct influence on the smoothness of the track. The study on the subgrade settlement characteristics of scholars at home and abroad discovers that subgrade settlement is caused by various factors, the difference between the subgrade treatment method and the structure type is one of the main factors influencing the longitudinal differential settlement of the soft soil subgrade, the subgrade soil type is also one of the factors influencing the settlement amount, and the various factors influence the change of the subgrade base soil state to further cause subgrade deformation and settlement. The common methods for calculating foundation settlement at present include a layered summation method, a calculation method according to stress history, a finite element method and the like, while calculation formulas of final foundation settlement adopted in foundation design specifications issued by departments such as buildings, railways, traffic, water conservancy and the like in China are different in form but are all based on the same basic assumption, namely the settlement of the foundation is assumed to be a result of compaction of a compression layer with limited thickness below a substrate under the condition of incapable lateral expansion under the effect of structural load, and the same method, namely the layered summation method, is basically adopted for calculating the settlement.
The subgrade settlement problem is always the root of the multiple diseases in the high-speed rail construction, especially the station subgrade section, the foundation treatment construction is complex, mostly high fill subgrades, the station subgrade settlement problem is always the potential safety hazard in the high-speed rail construction period and the operation period, but most of the settlement analysis of the subgrade foundation in China at present is only qualitatively analyzed, the quantitative analysis work is relatively less, and partial preliminary quantitative analysis is also only to analyze the settlement amount to obtain a qualitative result.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a method for quantitatively calculating the settlement generated after preloading of a railway roadbed, which can be used for calculating the settlement at the position adjacent to a non-observation section and making up the data loss of a sampling interval.
In order to achieve the purpose, the technical scheme of the invention is a method for quantitatively calculating the settlement generated after preloading of a railway subgrade, which comprises the following steps:
1) determining the relation between the settlement S and the thickness h of the foundation soil by a layering summation method;
2) establishing a railway roadbed settlement amount S calculation formula model during the surcharge preloading period according to the relation between the settlement amount S and the thickness h of the foundation soil;
3) surveying the railway subgrade needing preloading, drilling holes, sampling and collecting the geological data of the base of the railway subgrade, and making a longitudinal sectional view of the base geological data;
4) actually measuring the settlement S of the settlement observation section of the railway roadbed during the preloading period;
5) analyzing the thickness h of the foundation soil at the settlement observation section according to the longitudinal section diagram of the foundation geology;
6) carrying out nonlinear fitting on a calculation formula model of the railway subgrade settlement S during the preloading period by using the data in the step 4) and the step 5) to obtain a model coefficient;
7) and calculating the settlement S of the railway roadbed in the adjacent area or the similar geological area after the preloading of the railway roadbed by using the obtained model coefficient and a calculation formula model of the settlement S of the railway roadbed during the preloading.
Further, analyzing the soil quality type of the foundation soil of the railway roadbed according to the longitudinal section diagram of the foundation geology; according to the compressive strength of the foundation soil, the foundation soil of the railway roadbed is divided into two types: compression and non-compression soils;
when all the foundation soil is the anti-pressure soil or all the foundation soil is the non-anti-pressure soil, the settlement S of the railway subgrade during the surcharge preloading period is calculated by the following formula:
S＝(Xσz+Y)*eZh-(Xσz+Y) (1)
wherein S is the sedimentation amount, h is the thickness of the substrate soil,
mu isPoisson's ratio of the substrate soil, E is the elastic modulus of the soil structure, H is the elastic modulus of the soil structure related to the suction force of the substrate, K is the coefficient of static lateral pressure, uaIs pore gas pressure uwIs the pore water pressure, σzNormal stress in the Z direction, e is a natural constant, and Z is a constant;
carrying out nonlinear fitting on a calculation formula model of the railway subgrade settlement S during the preloading period by using the data in the step 4) and the step 5) to obtain a model coefficient (X sigma)z+ Y) and Z.
Further, when the foundation soil is partially anti-pressure soil and partially non-anti-pressure soil, the total settlement S of the railway subgrade during the preloading periodGeneral assemblyThe calculation formula model is:
Sgeneral assembly＝S1+S2 (2)
Wherein S isGeneral assemblyIs the total sedimentation amount, S1Amount of settlement for anti-crushing soil, S2The settlement of non-compressive soil, h1The thickness of the foundation soil for the anti-crushing soil,
mu is the Poisson's ratio of the substrate soil, E1Modulus of elasticity of soil structure to resist crushing, H1Modulus of elasticity of soil structure, K, related to suction of matrix for anti-crushing soil1Coefficient of static lateral pressure for resisting soil compression, ua1Pore gas pressure, u, to resist compactionw1Pore water pressure, σ, to resist compactionz1To resist normal stress in the soil Z direction, e is the natural constant, Z1Is a constant number h2The thickness of the foundation soil is not resistant to pressure,
E2modulus of elasticity, H, of soil structure for non-resistance to compression2Modulus of elasticity, K, of soil structure in relation to suction of matrix for non-compressive2Coefficient of static lateral pressure, u, for non-compressivea2Pore pressure, u, not against pressurew2Pore water pressure, σ, not withstanding pressurez2Is a normal stress in the non-compressive Z-direction, Z2Is a constant.
Furthermore, when the foundation soil is partially anti-pressure soil and partially non-anti-pressure soil, firstly, the actually measured settlement amount S of the anti-pressure soil during the preloading period is measured in the preloading railway roadbed section which is fully anti-pressure soil1And the thickness h of the soil of the anti-pressure soil1Performing nonlinear fitting to obtain model coefficient (X)1σz1+Y1) And Z1；
By model coefficient (X)1σz1+Y1) And Z1Calculating the thickness h of the base soil of the anti-pressure soil according to the formula (3)1Amount of settling of S1；
Using the measured total settlement S of the settlement observation section of the railway roadbed during the preloading periodGeneral assemblyMinus the amount of settlement S of the anti-crushing soil1Obtaining the settlement S of the non-anti-pressure soil2；
Analyzing the non-compressive subsoil thickness h at the settlement observation section according to the basement geological longitudinal section diagram2；
Settling amount S of non-compressive soil2Thickness h of non-compressive subsoil2Performing nonlinear fitting to obtain model coefficient (X)2σz2+Y2) And Z2；
By (X)2σz2+Y2) And Z2Calculating the settlement S of the non-anti-pressure soil according to the formula (4)2Then through the settlement S of the anti-pressure soil1And settling amount S of non-compressive soil2Calculating the total settlement S after the preloading of the railway roadbed in the adjacent area or the similar geological area according to the formula (2)General assembly。
Further, the compression-resistant soil comprises crushed soil; the non-compressive soil includes sandy soil, silt and clay.
Further, determining that the settlement S and the thickness h of the base soil in the step 1) are in a nonlinear relation and meet the requirement
Wherein, when h is 0, S is 0
Preferably, Matlab or SPSS is used for non-linear fitting in step 6).
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the method, a constitutive relation formula of a deduced soil structure is analyzed by researching a common settlement principle of the unsaturated soil of the foundation in practical engineering application under the preloading, a railway roadbed settlement amount S calculation formula model during the preloading is established, then nonlinear fitting is carried out according to the actually measured settlement amount S of a settlement observation section and the collected foundation soil thickness h, a model coefficient is obtained and is brought into the settlement amount S calculation formula model, and the settlement amount S is used for calculating the settlement amount S of the railway roadbed after the preloading of a near area or a similar geological area, so that the settlement amount of the railway roadbed without the observation section is obtained, and the data loss of a sampling interval is compensated;
(2) because settlement amounts of the compressive soil and the non-compressive soil generated under the condition of preloading are different, a railway roadbed settlement amount S calculation formula model during preloading is respectively established according to different types of foundation soils of the railway roadbed, model coefficients are fitted, settlement amounts S of the foundation soils of different types are respectively calculated, and errors are reduced.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a method for quantitatively calculating settlement of foundation soil of a railway roadbed after preloading according to the first embodiment;
FIG. 2 is a schematic view of a soil consolidation process;
FIG. 3 is a schematic illustration of a layered soil settling process;
FIG. 4 is a longitudinal section view of the basement geology;
fig. 5 is a flowchart of a method for quantitatively calculating the settlement of the foundation soil of the railway roadbed after preloading according to the second embodiment;
FIG. 6 is a non-linear fitting example chart of settlement and soil thickness of a substrate during a compressive soil preloading;
FIG. 7 is a sample graph of a nonlinear fit of the settlement during the non-compressive soil preloading and the thickness of the soil mass of the substrate.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
As shown in fig. 1, the present embodiment provides a method for quantitatively calculating the amount of settlement generated after preloading of a railway roadbed, which is characterized by comprising the following steps:
1) determining the relation between the settlement S and the thickness h of the foundation soil by a layering summation method, wherein the process is as follows:
firstly, establishing a soil body settlement calculation model;
the soil body settlement refers to that the volume of the soil body is gradually compressed when the stress state of the soil body is changed under the action of external force, meanwhile, partial water is discharged from the soil body, the external stress is correspondingly transmitted to the soil framework from pore water (and gas), and the pore water pressure is gradually dissipated to zero until the deformation is stable. The soil void ratio is the ratio of the void volume in the soil mass to the solid particle volume thereof, in terms of ekThe porosity ratio is expressed, and the indexes are used for explaining the structural characteristics of the soil body. In general, ekThe smaller the value, the more dense the soil and the lower the compressibility; e.g. of the typekThe larger the value, the looser the soil and the higher the compressibility.
Void ratio equation:
wherein ekIs the void ratio, VSIs the volume of soil, VVIs the pore volume;
as shown in FIG. 2, VSThe volume of the soil body is kept unchanged before and after preloading, the volume of the pores is changed after the soil is compressed, the pore ratio is changed, and the whole process follows the following formula:
wherein h isk0Thickness of base soil before preloading for surcharge, hk1Thickness of base soil after preloading for surcharge, ek0Porosity ratio of the foundation soil before preloading for surcharge, ek1The pore ratio of the base soil after the preloading loading is adopted, and S is the settlement amount after the preloading loading;
therefore, after the load is longitudinally applied to the soil, pore water can be gradually discharged, the effective pressure is increased, the soil body strength is increased, and the purpose of strengthening foundation treatment is achieved. According to the effective stress theory, the strength of soil texture increased by penetration consolidation is in direct proportion to the product of the additional total stress increment and the consolidation degree (assuming that the internal friction angle of the graph in the consolidation process is a constant, and therefore, the compression consolidation is the most direct cause of foundation settlement, and the theoretical settlement amount is S.
The layering summation method is that the foundation settlement is divided into a plurality of layers within the calculation depth range, the compression amount of each layer is calculated, and then the sum of the compression amounts is calculated. During calculation, the foundation settlement calculation depth is determined according to the basic load, the shape and the size of the foundation and relevant indexes of soil, layering is carried out within the foundation settlement calculation depth range, then the additional stress of the foundation is calculated, and the average value of the self-weight stress and the average value of the additional stress at the top surface and the bottom surface of each layering are calculated. FIG. 3 is a schematic illustration of a layered soil settling process;
the formula of a foundation soil settlement calculation model obtained according to the foundation settlement calculation layering summation method is as follows:
wherein S is the theoretical sedimentation amount, epsilonvjIs the total strain of the soil volume of the jth layer of soil under the roadbed, hjThe thickness of the j-th layer of soil under the roadbed, and M is the number of the soil layers.
Analyzing the constitutive relation of unsaturated soil;
in saturated soil mechanics, the effective stress variable sigma' sigma-u is proposed by the taisha basewThe elastic body metamorphic relation of the soil structure can be deduced, but the properties of unsaturated soil composed of a multi-phase mixture are more complicated than those of saturated soil, the water-gas interface (shrink film) of the unsaturated soil has surface tension, Fredlund, Morgensten and the like take the shrink film as the fourth phase of the unsaturated soil according to Hooke's law, and matrix suction (u) is introduceda-uw) Along with the state variables of stress (σ) in the three directions of compressive deformation of the soilx-ua)，(σy-ua) And (σ)z-uw) Together, the mechanical properties of unsaturated soils are described such that the constitutive relation of the soil structure with respect to normal strain in the x, y and z directions is:
in the formula, epsilonx、εyAnd εzNormal strain, σ, in the x, y, z directions, respectivelyx、σyAnd σzNormal stresses in the x, y, z directions, uaPore gas pressure (kPa), uwIs pore water pressure (kPa), ua-uwIs the substrate suction (kPa), mu is the Poisson's ratio of the soil, E is the soil structure elastic modulus (kPa), H is the soil structure elastic modulus (kPa) related to the substrate suction, E and H have negative signs, and the magnitude of the values changes for different incremental segments.
Whereby the total strain change epsilon of the soil volumevThe normal strain in the x, y, z directions is summed to give:
εv＝εx+εy+εz (107)
in consideration of lateral deformation, a railway embankment is loaded under a condition that the plane of the top surface of the roadbed is subjected to strain load, expands in the x direction (railway transverse direction), and has negligible deformation in the y direction (railway longitudinal direction) due to the strip-shaped load borne by the railway roadbed, i.e. epsilonyWhen the strain is 0, compressive sedimentation deformation or expansive deformation is generated in the z direction, namely the total strain change epsilonvCalculating formula:
assuming that the embankment soil is homogeneous and isotropic, the lateral pressure increase of the soil in the embankment may be considered as K times the vertical stress increase, K being defined as the static lateral pressure coefficient, i.e. the following equation:
σzK＝σx (109)
bringing formula (109) into formula (108) to obtain:
substituting equation 110 into equation 103 yields:
since the soil parameter Poisson's ratio mu does not vary with the porosity of the soil, K, E, H and ua-uwThe parameters can be statistically counted as comprehensive parameters of a soil body in the whole soil sedimentation process by inquiring historical data and field experiments to determine the reference values of the parameters according to various factors such as water content and compressibility of different soil structures:
substituting equations (112) and (113) into equation (111), we simplify to:
from the above formula, the effective stress σ can be seenzWill follow the soil layer hjIs subjected to different stresses and is finally accumulated into the total settlement, so that the series can be formulated as a double definite integral formula:
if the load capacity of the surcharge preloading is fixed and the load of the soil body is not considered, the load of the roadbed is fixed to be a constant, and the vertical effective stress sigma iszAnd correspondingly reduced to a constant, in which case the formula (115) can be reduced to a definite integral formula of the settlement S to the soil thickness h:
according to the definite integral law, S and h obtained by the integral calculation of the formula (116) belong to a nonlinear relation, the settling amount S is more than or equal to 0, and when h is 0, S is 0:
2) surveying the railway subgrade needing preloading, drilling holes, sampling and collecting the geological data of the base of the railway subgrade, and making a longitudinal sectional view of the base geological data; as shown in figure 4 of the drawings,
3) establishing a railway roadbed settlement amount S calculation formula model during the surcharge preloading period according to the relation between the settlement amount S and the thickness h of the foundation soil;
4) actually measuring the settlement S of the settlement observation section of the railway roadbed during the preloading period;
5) analyzing the thickness h of the foundation soil at the settlement observation section according to the longitudinal section diagram of the foundation geology;
6) carrying out nonlinear fitting on a calculation formula model of the railway subgrade settlement S during the preloading period by using the data in the step 4) and the step 5) to obtain a model coefficient;
7) and calculating the settlement S of the railway roadbed in the adjacent area or the similar geological area after the preloading of the railway roadbed by using the obtained model coefficient and a calculation formula model of the settlement S of the railway roadbed during the preloading.
Drawing a scatter diagram of the actually measured settlement amount of the settlement monitoring section and the soil thickness of the bottom layer of the section in statistical software such as Matlab or SPSS, and the like, and adopting the statistical software to indicate a exponential curve, a logarithmic curve, a polynomial and a power function pair formula
The model is subjected to nonlinear fitting and model parameters are calculated iteratively, the settlement S is larger as the settlement S is larger and the soil thickness is larger in consideration of the fact that the settlement S is larger than or equal to 0 in the actual situation, and the settlement S is 0 when h is 0, so that the exponential curve obtained through fitting can meet the requirements and has the best fitting precision, namely the best fitting precisionThe final determined railway subgrade settlement during the pre-loading period is calculated by the formula model of S ═ (X σ ═ S ═z+Y)*eZh-(Xσz+ Y), wherein (X σz+ Y) and Z are model coefficients, e is a natural constant, and the obtained model coefficients are substituted into a formula to calculate the settlement of similar roadbed sections after preloading.
According to the method, the settlement of unsaturated soil under the condition of roadbed preloading, which generally exists in actual engineering projects, is researched, a calculation formula model of the thickness and the settlement of the soil body is deduced by researching the mechanical property of a soil structure and based on a hierarchical summation method and combining the matrix suction of a soil shrinkage film and the constitutive relation related to normal strain in the x direction, the y direction and the z direction, and the model coefficient is fitted by using Matlab or SPSS statistical software, so that the vertical deformation of a similar soil body after preloading in actual engineering can be calculated.
Example two
As shown in fig. 5, the present embodiment provides a method for quantitatively calculating the amount of settlement generated after preloading of a railway roadbed, which is characterized by comprising the following steps:
1) determining the relation between the settlement S and the thickness h of the foundation soil by a layering summation method;
2) surveying the railway subgrade needing preloading, drilling holes, sampling and collecting the geological data of the base of the railway subgrade, and making a longitudinal sectional view of the base geological data;
3) because the settlement quantity of the compression-resistant soil and the non-compression-resistant soil is different under the condition of preloading, analyzing the soil quality type of the foundation soil of the railway roadbed according to the longitudinal cross section diagram of the foundation geology; the roadbed and foundation soil is divided into two types according to the compressive strength of the foundation soil: compression and non-compression soils; wherein, the compression-resistant soil comprises gravel soil, and the gravel soil comprises boulder soil, cobble soil, coarse gravel soil and the like; the non-compressive soil comprises sandy soil, silty clay and the like;
4) when the base soil is all the compression-resistant soil or all the non-compression-resistant soil, establishing a railway roadbed settlement amount S calculation formula model during the preloading according to the relation between the settlement amount S and the thickness h of the base soil:
S＝(Xσz+Y)*eZh-(Xσz+Y) (1)
wherein S is the sedimentation amount, h is the thickness of the substrate soil,
mu is the Poisson's ratio of the substrate soil, E is the elastic modulus of the soil structure, H is the elastic modulus of the soil structure related to the suction force of the substrate, K is the coefficient of static lateral pressure, uaIs pore gas pressure uwIs the pore water pressure, σzNormal stress in the Z direction, e is a natural constant, and Z is a constant;
actually measuring the settlement S of the settlement observation section of the railway roadbed during the preloading period;
analyzing the thickness h of the foundation soil at the settlement observation section according to the longitudinal section diagram of the foundation geology;
using the settlement S of the settlement observation section of the railway roadbed during the actual measurement of the preloading period and collecting data in the base soil thickness h at the settlement observation section to draw a scatter diagram by adopting statistical software such as Matlab or SPSS and the like, and carrying out nonlinear fitting on a calculation formula model of the settlement S of the railway roadbed during the preloading period in the Matlab or SPSS according to a formula (1) to obtain a model coefficient (X sigma)z+ Y) and Z; then passes through the model coefficient (X sigma)z+ Y) and Z and formula (1), calculating settlement S after preloading of the railway subgrade in the adjacent area or the similar geological area;
5) when the base soil is partially anti-pressure soil and partially non-anti-pressure soil, the total settlement S of the railway roadbed during the preloading period is established according to the relation between the settlement S and the thickness h of the base soilGeneral assemblyThe calculation formula model is:
Sgeneral assembly＝S1+S2 (2)
Wherein S isGeneral assemblyIs the total sedimentation amount, S1Amount of settlement for anti-crushing soil, S2The settlement of non-compressive soil, h1The thickness of the foundation soil for the anti-crushing soil,
mu is the Poisson's ratio of the substrate soil, E1Modulus of elasticity of soil structure to resist crushing, H1Modulus of elasticity of soil structure, K, related to suction of matrix for anti-crushing soil1Coefficient of static lateral pressure for resisting soil compression, ua1Pore gas pressure, u, to resist compactionw1Pore water pressure, σ, to resist compactionz1To resist normal stress in the soil Z direction, e is the natural constant, Z1Is a constant number h2The thickness of the foundation soil is not resistant to pressure,
E2modulus of elasticity, H, of soil structure for non-resistance to compression2Modulus of elasticity, K, of soil structure in relation to suction of matrix for non-compressive2Coefficient of static lateral pressure, u, for non-compressivea2Pore pressure, u, not against pressurew2Pore water pressure, σ, not withstanding pressurez2Is a normal stress in the non-compressive Z-direction, Z2Is a constant.
Under the general condition, the non-pressure-resistant soil has less pressure-resistant soil, otherwise, the area is not suitable for being used as a railway construction roadbed area, so that firstly, the settlement quantity S of the settlement observation section of the pressure-resistant soil during the preloading period is actually measured in the preloading railway roadbed section which is all the pressure-resistant soil1(ii) a Analyzing the thickness h of the foundation soil of the anti-pressure soil at the settlement observation section according to the longitudinal section diagram of the foundation geology1(ii) a The measured settlement S of the anti-pressure soil during the preloading period1And the thickness h of the soil of the anti-pressure soil1Drawing a scatter diagram on statistical software such as Matlab or SPSS according to a formula (3)Settlement S of railway bed during preloading in Matlab or SPSS1The calculation formula model is subjected to nonlinear fitting to obtain a model coefficient (X)1σz1+Y1) And Z1As shown in fig. 6;
by model coefficient (X)1σz1+Y1) And Z1Calculating the thickness h of the base soil of the anti-pressure soil according to the formula (3)1Amount of settling of S1；
Actually measuring total settlement S of settlement observation section of railway roadbed during preloadingGeneral assembly；
Using the measured total settlement S of the settlement observation section of the railway roadbed during the preloading periodGeneral assemblyMinus the amount of settlement S of the anti-crushing soil1Obtaining the settlement S of the non-anti-pressure soil2；
Analyzing the non-compressive subsoil thickness h at the settlement observation section according to the basement geological longitudinal section diagram2；
Settling amount S of non-compressive soil2Thickness h of non-compressive subsoil2Drawing a scatter diagram in statistical software such as Matlab or SPSS, and the settlement amount S of the railway roadbed during preloading period in Matlab or SPSS according to a formula (4)2The calculation formula model is subjected to nonlinear fitting to obtain a model coefficient (X)2σz2+Y2) And Z2As shown in fig. 7;
by (X)2σz2+Y2) And Z2Calculating the settlement S of the non-anti-pressure soil according to the formula (4)2Then through the settlement S of the anti-pressure soil1And settling amount S of non-compressive soil2Calculating the total settlement S after the preloading of the railway roadbed in the adjacent area or the similar geological area according to the formula (2)General assembly。
The settlement observation sections are arranged at intervals of 50-100 meters in the conventional settlement sampling method, so that the sampling rate cannot be guaranteed, the settlement of roadbed sections between the observation sections cannot be obtained, and the settlement model formula of the embodiment can be adopted to calculate the vertical deformation of an adjacent area or a similar geological area after preloading in actual engineering, so that the settlement of the adjacent observation-free sections can be calculated, and the data loss of the sampling intervals can be compensated. The method has the advantages that the vertical deformation of the soil body of the whole section of the preloading roadbed is predicted, the prevention and guidance effects on engineering are achieved, and a theoretical basis is provided for future researches on the estimation calculation of the settlement amount and the settlement influence of non-pressure-resistant geotechnical conditions such as silty clay after preloading.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A method for quantitatively calculating the settlement generated after preloading of a railway subgrade is characterized by comprising the following steps:
1) determining the relation between the settlement S and the thickness h of the foundation soil by a layering summation method;
2) surveying the railway subgrade needing preloading, drilling holes, sampling and collecting the geological data of the base of the railway subgrade, and making a longitudinal sectional view of the base geological data;
3) establishing a railway roadbed settlement amount S calculation formula model during the surcharge preloading period according to the relation between the settlement amount S and the thickness h of the foundation soil;
analyzing the soil quality type of the foundation soil of the railway roadbed according to the longitudinal section diagram of the foundation geology; according to the compressive strength of the foundation soil, the foundation soil of the railway roadbed is divided into two types: compression and non-compression soils;
when all the foundation soil is the anti-pressure soil or all the foundation soil is the non-anti-pressure soil, the settlement S of the railway subgrade during the surcharge preloading period is calculated by the following formula:
S＝(Xσz+Y)*eZh-(Xσz+Y) (1)
wherein S is the sedimentation amount, h is the thickness of the substrate soil,
mu is the Poisson's ratio of the substrate soil, E is the elastic modulus of the soil structure, H is the elastic modulus of the soil structure related to the suction force of the substrate, K is the coefficient of static lateral pressure, uaIs pore gas pressure uwIs the pore water pressure, σzNormal stress in the Z direction, e is a natural constant, and Z is a constant;
4) actually measuring the settlement S of the settlement observation section of the railway roadbed during the preloading period;
5) analyzing the thickness h of the foundation soil at the settlement observation section according to the longitudinal section diagram of the foundation geology;
6) carrying out nonlinear fitting on a calculation formula model of the railway subgrade settlement S during the preloading period by using the data in the step 4) and the step 5) to obtain a model coefficient;
7) and calculating the settlement S of the railway roadbed in the adjacent area or the similar geological area after the preloading of the railway roadbed by using the obtained model coefficient and a calculation formula model of the settlement S of the railway roadbed during the preloading.
2. The method for quantitatively calculating the amount of settlement generated after the preloading of the railroad bed as set forth in claim 1, wherein:
when the foundation soil is partially anti-pressure soil and partially non-anti-pressure soil, the total settlement S of the railway subgrade during the preloadingGeneral assemblyThe calculation formula model is:
Sgeneral assembly＝S1+S2 (2)
Wherein S isGeneral assemblyIs the total sedimentation amount, S1Amount of settlement for anti-crushing soil, S2The settlement of non-compressive soil, h1The thickness of the foundation soil for the anti-crushing soil,
mu is the Poisson's ratio of the substrate soil, E1Modulus of elasticity of soil structure to resist crushing, H1Modulus of elasticity of soil structure, K, related to suction of matrix for anti-crushing soil1Coefficient of static lateral pressure for resisting soil compression, ua1Pore gas pressure, u, to resist compactionw1Pore water pressure, σ, to resist compactionz1To resist normal stress in the soil Z direction, e is the natural constant, Z1Is a constant number h2The thickness of the foundation soil is not resistant to pressure,
E2modulus of elasticity, H, of soil structure for non-resistance to compression2Modulus of elasticity, K, of soil structure in relation to suction of matrix for non-compressive2Coefficient of static lateral pressure, u, for non-compressivea2Pore pressure, u, not against pressurew2Pore water pressure, σ, not withstanding pressurez2Is a normal stress in the non-compressive Z-direction, Z2Is a constant.
3. The method for quantitatively calculating the amount of settlement generated after the preloading of the railroad bed as set forth in claim 2, wherein: when the foundation soil is partially anti-pressure soil and partially non-anti-pressure soil, firstly, the actually measured settlement amount S of the anti-pressure soil during the preloading period is measured in the preloading railway roadbed section which is fully anti-pressure soil1And the thickness h of the soil of the anti-pressure soil1Performing nonlinear fitting to obtain model coefficient (X)1σz1+Y1) And Z1；
By model coefficient (X)1σz1+Y1) And Z1Calculating the thickness h of the base soil of the anti-pressure soil according to the formula (3)1Amount of settling of S1；
Using the measured total settlement of settlement observation section of railway roadbed during preloading periodSGeneral assemblyMinus the amount of settlement S of the anti-crushing soil1Obtaining the settlement S of the non-anti-pressure soil2；
Analyzing the non-compressive subsoil thickness h at the settlement observation section according to the basement geological longitudinal section diagram2；
Settling amount S of non-compressive soil2Thickness h of non-compressive subsoil2Performing nonlinear fitting to obtain model coefficient (X)2σz2+Y2) And Z2；
By (X)2σz2+Y2) And Z2Calculating the settlement S of the non-anti-pressure soil according to the formula (4)2Then through the settlement S of the anti-pressure soil1And settling amount S of non-compressive soil2Calculating the total settlement S after the preloading of the railway roadbed in the adjacent area or the similar geological area according to the formula (2)General assembly。
4. The method for quantitatively calculating the amount of settlement generated after the preloading of the railroad bed as set forth in claim 1, wherein: the compression-resistant soil comprises crushed soil; the non-compressive soil includes sandy soil, silt and clay.
5. The method for quantitatively calculating the amount of settlement generated after the preloading of the railroad bed as set forth in claim 1, wherein: determining that the settlement S and the thickness h of the base soil are in a nonlinear relation in the step 1), and meeting the requirement
Wherein, when h is 0, S is 0.
6. The method for quantitatively calculating the amount of settlement generated after the preloading of the railroad bed as set forth in claim 1, wherein: and 6) carrying out nonlinear fitting by adopting Matlab or SPSS.
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| CN111024034B (en) * | 2019-12-26 | 2022-04-15 | 江强 | Soft soil roadbed settlement prediction method and prediction system based on monitoring process data and storage medium |
| CN112989460B (en) * | 2021-02-22 | 2022-08-16 | 中国科学院武汉岩土力学研究所 | Subgrade settlement calculation method caused by subgrade construction and operation in soft soil area |
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