CN112964533A - Clay model foundation preparation method capable of recovering prototype state and strength - Google Patents
Clay model foundation preparation method capable of recovering prototype state and strength Download PDFInfo
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- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
Abstract
The invention discloses a clay model foundation preparation method for recovering prototype state and strength. Determining the total thickness and layering of a prototype foundation and a model foundation; obtaining the non-drainage shear strength of each layer of soil body of the prototype foundation; calculating to obtain state parameters of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation; determining the slopes of an indoor compression consolidation line and an unloading rebound line of the soil body of the prototype foundation, and obtaining the initial pore ratio of each layer of the soil body of the model foundation through reverse thrust; and carrying out layered preparation on the model foundation. On the premise of recovering the state and the strength of the prototype foundation, the invention improves the economy and the operability of model foundation preparation, enlarges the preparation range of the model foundation, overcomes the possible sensor dislocation problem in the preparation process of the centrifugal model, improves the economy of model preparation and the flexibility of sensor arrangement, and ensures the accuracy of the centrifugal model test.
Description
Technical Field
The invention belongs to the technical field of physical model test theories, and particularly relates to a clay model foundation preparation method for recovering prototype state and strength.
Technical Field
A large number of soft clay foundations exist in the engineering construction of China, and most of the soft clay foundations are distributed in the southeast coastal areas of China, such as the Zhujiang Delta, the Changjiang Delta and the like, the areas are relatively developed in economy, and a large number of infrastructures are already built or are being built. The soft clay has high natural water content, large porosity ratio, sensitivity and thixotropy, poor permeability, obvious reasons of structural property, low shear strength, poor physical and mechanical properties and the like, and instability and damage of clay foundations occur sometimes. Therefore, when large-scale geotechnical structures such as dam filling, high slope embankments, airport high fill and the like are built on clay foundations, if the bearing capacity of the foundations is insufficient, a greater disaster is often caused, and irreparable life and property loss is caused. In view of the above, people often study the response of the prototype foundation by means of physical model tests. The supergravity centrifugal model test has the advantage of reproducing a prototype stress field, so that the prototype response of the prototype soft clay foundation under the influence of large-scale geotechnical structure construction or extreme working conditions is reproduced by the supergravity centrifugal model test, and the test section is very reasonable and effective.
The centrifugal model test means that a test prototype is reduced by lambda times according to a certain geometric similarity proportion, and a corresponding reduced-size model is prepared by adopting materials meeting the similarity ratio. And placing the reduced scale model in an N-time original gravity field generated by the rotation of a centrifugal machine, further reproducing the stress level in the prototype, and obtaining the same model failure condition and failure mechanism as the prototype, thereby inverting the response of the prototype according to the response of the model and realizing the evaluation and design of the prototype stability. The method overcomes the problems in the model test in the conventional normal gravity field, such as unequal stress levels and unequal stress-strain characteristics under normal gravity, and has obvious advantages.
Whether the physical and mechanical properties of the model in the centrifugal model test can be reduced under the hypergravity field is a key factor for determining the accuracy of the test result of the centrifugal model. When the model is subjected to centrifugal test, the strength characteristic of the model is the same as that of the prototype, and the density and stress state of the model are consistent with those of the prototype. Therefore, the centrifugal model for preparing the clay foundation is required to be controlled to be consistent between the state of the centrifugal model in the original stress field and the prototype, and the model in the centrifugal state is also required to be controlled to be the same as the strength of the prototype, so that the real prototype foundation soil response rule is obtained.
At present, the common method for preparing clay foundation models is to prepare the models by pre-pressing and consolidating from a slurry state under normal gravity (1g) and then perform overload pre-pressing and consolidation under supergravity (ng) until the models are settled stably. The method can rapidly prepare the normal clay consolidation clay foundation model by compressing and consolidating through the centrifuge, but has a plurality of defects:
(1) preparation of clay foundation model by centrifugal consolidation a centrifuge is used for centrifugal consolidation lasting for more than ten hours. The complexity of the centrifuge operation not only imposes high technical requirements on the operator, but also leads to high energy consumption and high cost.
(2) The clay foundation model prepared by centrifugal consolidation is usually a normal consolidation model foundation or a model foundation with continuously changed soil body strength, the stress history of the prepared centrifugal model foundation is difficult to correctly recover, the condition of discontinuous distribution of the soil body state and the strength of the prototype foundation cannot be restored, and the application range of model preparation is limited.
(3) When the centrifugal consolidation is used for preparing the model, the sensor needs to be embedded in advance, and then the centrifugal consolidation is carried out. This may cause the sensor in the model to have a larger position deviation along with the soil consolidation settlement in the centrifugal consolidation process, resulting in a larger test error.
In order to overcome the defects of the centrifugal consolidation preparation method of the clay foundation model, the clay foundation model is controlled in a layering mode to be identical in state and strength to the middle of the soil body of each layer of the foundation of the prototype based on the idea of layered equivalent substitution, and therefore the centrifugal test result of the clay foundation model is guaranteed to be true response to the prototype foundation.
Disclosure of Invention
The invention discloses a clay model foundation preparation method for recovering prototype state and strength in order to solve the clay model foundation preparation problem in the large-scale problem of a simulated prototype field of a hypergravity physical model test.
The technical scheme adopted by the invention is as follows:
the method comprises the following steps:
determining the total thickness h of the prototype foundationpAnd total thickness h of model foundationmLayering the soil body of the prototype foundation and the soil body of the model foundation to obtain the soil body of each layer of the prototype foundation and the soil body of the same layer corresponding to the model foundation, wherein m represents the model foundation, and p represents the prototype foundation; h ispBy a factor of λ hm；
S2: carrying out an in-situ cross plate shear test on each layer of soil body of the prototype foundation to obtain the non-drainage shear strength of the middle part of each layer of soil body of the prototype foundationThe in-situ cross plate shear test belongs to the field of soil body in-situ test and aims at measuring the non-drainage shear strength of the soil body of the prototype foundation through the cross plate. The specific operation flow can refer to related test procedures.
S3: controlling the non-drainage shear strength of each layer of soil body of the model foundation to be equal to the non-drainage shear strength of the middle part of the soil body of the same layer corresponding to the prototype foundation, calculating the super-consolidation ratio of each layer of soil body of the prototype foundation according to the empirical relationship between the non-drainage shear strength of the middle part of each layer of soil body of the prototype foundation and the super-consolidation ratio, using the super-consolidation ratio as the super-consolidation ratio of the soil body of the same layer corresponding to the model foundation, and then calculating the state parameter of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation pressure stress of each;
s4: determining the slope lambda of a compression consolidation line and the slope kappa of an unloading rebound line of each layer of soil body of the prototype foundation under an e-lnp semilogarithmic coordinate system, drawing the state parameters of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation in an e-lnp coordinate system, and obtaining the initial pore ratio of each layer of soil body of the model foundation by reversely deducing the unloading rebound slope and the slope of the compression consolidation lineAs shown in fig. 2;
s5: and preparing the model foundation layer by layer according to the initial slurry state of each layer of soil body of the model foundation and the consolidation pressure stress of each layer of soil body of the model foundation, and preparing the gap embedding sensor in the model foundation layer by layer.
In step S1, the prototype foundation soil body and the model foundation soil body are layered to realize equivalent replacement of the prototype foundation layering by the model foundation layering, and the specific steps are as follows:
dividing the prototype foundation and the model foundation into n layers to obtain each layer of soil body of the prototype foundation and the soil body of the same layer corresponding to the model foundation, wherein the soil bodies can be divided evenly or unevenly, and the geometric similarity ratio of each layer of thickness of the model foundation to the same layer of thickness corresponding to the prototype foundation is determined to be lambda according to the total thickness of the prototype foundation and the size of a model box; the thickness of each layer of soil body of the prototype foundation isThe thickness of the model foundation corresponding to the soil body of the same layer is reduced by lambda timesWhere k is 1,2 … … n, k represents the number of soil layering from top to bottom, and n represents the total number of layering.
In step S3, the state parameters of the middle part of each layer of soil body of the prototype foundation are The pore ratio of the middle part of each layer of soil body of the prototype foundation is obtained;
the mean effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation; the determination of the state parameters of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation comprises the following steps:
s31: carrying out an indoor basic physical property test on each layer of soil body of the prototype foundation to obtain the specific gravity and the floating density of each layer of soil body of the prototype foundation;
the basic physical property test can obtain parameters such as specific gravity, floating density and the like of the prototype foundation soil body, and the specific operation method can refer to related test procedures.
S32: the effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation is obtained by adopting the following formula:
wherein k represents a soil layering number from top to bottom, and k is 1,2 … … n;the floating density of the j layer soil body of the prototype foundation; g is the local gravitational acceleration;the thickness of the k layer soil body of the prototype foundation; j represents the traversal sequence number of the soil body of the k layer, and j starts from 0;representing the effective self-weight stress of the middle part of the k-th layer soil body of the prototype foundation;represents the thickness of the j-th layer soil body of the prototype foundation,representing the floating density of the k layer soil body of the prototype foundation;
s33: calculating the porosity ratio of the middle part of each layer of soil body of the prototype foundation by adopting the following formula:
in the formula (I), the compound is shown in the specification,the pore ratio of the middle part of the k layer soil body of the prototype foundation;the floating density of the k layer soil body of the prototype foundation; rhowIs the density of water; dskThe specific gravity of the k layer soil body of the prototype foundation;
s34: obtaining the super-consolidation ratio of the middle part of each layer of soil body of the prototype foundation by adopting the following formula according to the experience between the normalized non-drainage shear strength and the super-consolidation ratio
In the formula (I), the compound is shown in the specification,the normalized non-drainage shear strength of the test slurry soil body during normal compression consolidation is shown, and NC represents normal consolidation;representing the undrained shear strength of the k-th soil body of the prototype foundation,representing the effective self-weight pressure stress of the kth layer soil body of the prototype foundation; b is undetermined parameters in an empirical formula, and can be evaluated by referring to related documents or performing indoor tests according to the types and pore ratios of soil bodies of all layers of the prototype foundation;
s35: the ultra-consolidation ratio of each layer of soil body of the control model foundation is equal to that of each layer of soil body of the corresponding prototype foundation, namelyIs equal toThen, calculating the effective consolidation compressive stress of each layer of soil body of the model foundation by adopting the following formula:
in the formula (I), the compound is shown in the specification,representing the ultra-consolidation ratio of each layer of soil body of the model foundation;representing the effective self-weight pressure stress of the kth layer soil body of the prototype foundation;
representing the effective consolidation compressive stress of the k-th layer soil body of the model foundation;
s36: respectively calculating the average effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation by the following formulas:
in the formula (I), the compound is shown in the specification,the mean effective dead weight compressive stress of the middle part of the kth layer soil body of the prototype foundation;
the average effective consolidation compressive stress of the k layer soil body of the model foundation; k0The static soil pressure coefficient of the prototype foundation soil body;the effective self-weight compressive stress of the middle part of the kth layer soil body of the prototype foundation;the effective consolidation compressive stress of the k layer soil body of the model foundation.
In step S4, the determination of the initial void ratio of each layer of soil body of the model foundation includes the following steps:
s41: taking a prototype foundation soil body indoors, preparing a slurry sample, and then carrying out an indoor compression consolidation test and an unloading rebound test on the slurry sample to obtain a compression consolidation line slope lambda and an unloading rebound line slope kappa, wherein the specific operation flow of the compression consolidation and the unloading rebound test can refer to related test procedures;
s42: the state parameters of the middle part of each layer of soil body of the prototype foundation obtained in the step S3 are processedAnd the average effective consolidation compressive stress of each layer of soil body of the model foundation is drawn under an e-lnp semilogarithmic coordinate system and passes throughPoint drawing parallel lines with the slope equal to the slope kappa of the unloading rebound line are respectively crossed with the average effective consolidation compressive stress of each layer of soil body of the model foundation
In thatWhereinState parameters of each layer of soil body of the model foundation under the action of respective average effective consolidation compressive stress;
s43: state parameter of each layer of soil body of over-model foundationDrawing compression and solidification parallel lines with the slope equal to the slope lambda of the compression and solidification line, and respectively intersecting the compression and solidification parallel lines with the vertical coordinate axisAt least one of (1) and (b); whereinThe initial pore ratio of each layer of soil body of the model foundation in a slurry state before consolidation and compression is set;
the step S5: in the method, the layered preparation process of the model foundation comprises the following specific steps:
s51: taking a prototype foundation soil body indoors, and obtaining initial water content according to the following formulaPreparing n groups of slurry soil bodies:
wherein the content of the first and second substances,representing the corresponding initial water content when each layer of soil body of the model foundation is in a slurry state before compression and consolidation when the model foundation is prepared in a layered mode; srIs the saturation; taking 100% of mud soil; dskThe specific gravity of the k layer soil body of the prototype foundation;the initial pore ratio of each layer of soil body of the model foundation in a slurry state before consolidation and compression; k represents the sequence number of the soil layering from top to bottom, and k is 1,2 … … n;
s52: obtaining the effective consolidation compressive stress of each layer of soil body of the model foundation according to the step S35And (4) respectively carrying out layered compression consolidation on the n groups of slurry soil bodies prepared in the step (S51) to finish the layered preparation of the model foundation, and burying a sensor at a specific position in a layered compression consolidation gap. The method specifically comprises the following steps: pouring the n group of mud soil bodies into the model box, and then according to the consolidation compressive stress corresponding to the n layer soil body of the model foundationCarrying out compression consolidation; after the compression consolidation is finished, pouring the slurry soil of the n-1 group into the slurry soil, and performing corresponding consolidation pressure stressAfter the lower consolidation is finished, the layered preparation of the model foundation is finished by analogy; meanwhile, when each layer of model foundation soil body is compressed and consolidated in a layered mode, a sensor is embedded at a specific position according to needs and used for response analysis of a subsequent centrifugal model test.
The method is based on the basic idea that the clay model foundation state and strength are layered equivalent to substitute the prototype, and the centrifugal test result of the model foundation is finally ensured to be the real reflection of the prototype foundation by controlling the state and the strength of each layer of soil body of the clay model foundation to be equivalent to the prototype under the original stress field.
The invention has the beneficial effects that:
1. the clay model foundation is prepared by layering, prepressing and consolidating, so that the use of complex centrifuge equipment is avoided, the operation difficulty and the complexity of the preparation process are reduced, meanwhile, the high energy consumption of the rotation of the centrifuge is avoided, the cost for preparing the centrifugal model foundation is greatly saved, and the economic benefit is remarkable.
2. The clay model foundation is prepared by layering, prepressing and consolidating, the strength of the prototype foundation can be recovered, the state of each layer of soil body of the model foundation can be ensured to be equivalent to the prototype foundation, meanwhile, the method is still applicable to the situation of discontinuous change of the soil body property of the prototype foundation, and the preparation range of the clay model foundation is greatly expanded.
3. The clay model foundation is prepared by layering, prepressing and consolidating, so that arrangement of sensors in the model foundation is enabled to have great flexibility and easy operability, and sensor dislocation possibly caused by clay consolidation settlement in a centrifugal consolidation preparation process is avoided, and accuracy of a centrifugal model test is improved.
In summary, the invention is suitable for researching the clay foundation stability problem in the construction of overlying large-scale geotechnical structures through a centrifugal model test, and provides a method for preparing a clay foundation centrifugal model through layered prepressing consolidation based on the idea of layered equivalent substitution to control the state and the strength of a layered model foundation in a centrifugal field to be equivalent to a prototype.
Drawings
FIG. 1 is a schematic diagram of a model foundation non-drainage shear strength layered equivalent substitute prototype;
FIG. 2 is a schematic diagram of the determination of initial pore ratio of each layer of soil body of the model foundation in the embodiment.
Detailed Description
The invention is further described with reference to the following figures and specific examples. The following examples are intended to illustrate the invention only and are not intended to limit the scope of the invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The examples of the invention are as follows:
in a specific embodiment, the prototype foundation soil can be simplified into a saturated clay foundation with the depth of 10m, the soil body type is mainly kaolin, and the static soil pressure coefficient is 0.5. The method provided by the patent is used for preparing a model foundation with the soil strength and state equivalent to a prototype in a centrifugal model test, and comprises the following specific steps:
the first step, the size of the prototype foundation is hp＝10m, selecting 30g centrifugal acceleration according to the performance of the centrifuge and the size of the model box, and determining the size h of the model when the corresponding geometric similarity scale lambda is 30mThe model and the model foundation are divided into 3 layers;
secondly, according to the indoor basic physical property test, the specific gravity of each layer of soil body of the prototype foundation is measured to be equal to ds2.65, the floating density of each layer is equal to 855kg/m3；
Thirdly, carrying out an in-situ cross plate shear test on the prototype foundation to determine the non-drainage shear strength of the middle part of each layer of soil body of the prototype foundation
Calculating the effective dead weight compressive stress at the corresponding position according to the formula (1)
Calculating the void ratio of the middle part of each layer of soil body of the prototype foundation according to the formula (2)According to the pore ratio of the prototype foundation and the soil body type, undetermined parameters in the formula (3) are determined and calculated to obtainControl ofAnd calculating the effective consolidation compressive stress of each layer of soil body of the model foundation according to the formula (4)Finally, respectively calculating the average effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation through a formula (5) and a formula (6)And average effective consolidation compressive stress of model foundation
In the formula, k represents a number of the soil layer layers from top to bottom, and k is 1,2 … … n.The floating density of the k-th layer soil body of the prototype is obtained; g is the local gravitational acceleration;the thickness of the k-th layer soil body of the prototype; j represents the traversal sequence number in the k-th layer soil body;
in the formula (I), the compound is shown in the specification,
the normalized unpopped shear strength of the test slurry consolidated to a specific pore ratio is shown, and B is the undetermined parameter in the empirical formula. The parameters can be evaluated by referring to relevant documents or carrying out indoor tests according to the types and the pore ratios of the soil bodies of all layers of the prototype foundation.
In the formula, K0Is the static soil pressure coefficient of the test soil body;effective dead weight pressure stress of the middle part of the k-th layer soil body of the prototype;effectively consolidating the compressive stress for the k-th layer of soil body of the model;
the mean effective dead weight stress at the middle part of the k-th layer soil body of the prototype is obtained;the average effective consolidation compressive stress of the k-th layer of soil body of the model is obtained;
fourthly, taking the prototype soil body to carry out indoor compression consolidation/unloading resilience test to obtain a compression consolidation line slope lambda of 0.256 and an unloading resilience line slope kappa of 0.029 under an e-lnp semilogarithmic coordinate system; state parameter of each layer of soil body of prototype foundationAs parallel lines for unloading rebound lines, and AC-DC linesState parameter points of each layer of soil body on model foundationPassing point
Drawing compression consolidation parallel lines with the slope of lambda, and intersecting the vertical coordinate axis
At least one of (1) and (b); whereinState parameters of each layer of soil body of the model foundation under the action of respective average effective consolidation compressive stress; wherein
The initial pore ratio of each layer of soil body of the model foundation in a slurry state before consolidation and compression is set;
fifthly, taking the prototype foundation soil body indoors and preparing the initial water contentN groups of slurry soil bodies which accord with the formula (7) are reserved:
wherein the content of the first and second substances,representing the initial water content S corresponding to each layer of soil in a slurry state before compression and consolidation when the model foundation is prepared in layersrFor saturation, 100% is taken for the mud soil body, subscript k represents the number of soil layering from top to bottom, k is 1,2 … … n;
according to the obtained vertical consolidation compressive stress of each layer of soil body of the model foundationAnd (4) respectively carrying out layered compression consolidation on the n groups of slurry soil bodies prepared in the fifth step to finish the layered preparation of the model foundation, and burying a sensor at a specific position in a layered compression consolidation gap. The method specifically comprises the following steps: pouring the n group of mud soil bodies into the model box, and then according to the consolidation compressive stress corresponding to the n layer soil body of the model foundationCarrying out compression consolidation; after the compression consolidation is finished, pouring the slurry soil of the n-1 group into the slurry soil, and performing corresponding consolidation pressure stressAfter the lower consolidation is finished, the layered preparation of the model foundation is finished by analogy; meanwhile, when each layer of model foundation soil body is compressed and consolidated in a layered mode, a sensor is embedded at a specific position according to needs and used for response analysis of a subsequent centrifugal model test.
To explain the concrete steps of the third, fourth and fifth steps in detail, the calculation process of the first layer soil is taken as an example and explained as follows:
(1) obtaining the non-drainage shear strength of the middle part of the first layer of soil body by an in-situ cross plate shear test
(2) Floating the first layer of soil mass to densityWith the thickness of the first layer foundation soilSubstituting the formula (1) to obtain the effective consolidation compressive stress of the middle part of the first layer foundation soil body
(3) The specific gravity d of the first layer of soil bodys12.65 and the floating density of the soilSubstituting the formula (2) to calculate the porosity ratio of the middle part of the first layer of soil body
(4) According to the obtained first layer soil body pore ratio and soil body type, determining through indoor test and reference related experience parameter table
B is 0.80. And will beAndobtained by bringing into an improved empirical formula (3)
(5) Control ofAnd mixing it withSubstituting the effective consolidation compressive stress of each layer of soil body of the model foundation into the formula (4) and calculating
(6) Will K0＝0.5、Respectively carrying the average effective dead weight stress in the middle of the first layer foundation soil body into the formulas (5) and (6) to obtain the average effective dead weight stressAnd the average effective consolidation compressive stress of the first layer soil body of the model foundation
(7) Under the e-lnp semilogarithmic coordinate system, the state point of the middle part of the first-layer foundation soil bodyMaking a parallel line with the slope equal to the unloading rebound line kappa equal to 0.029, and crossingAt model soil state pointsAt least one of (1) and (b);
(8) first-layer soil body state point of over-model foundationDrawing parallel lines with slope equal to compression bonding line lambda 0.256, and intersecting the vertical coordinate axis with the initial porosity ratio
(9) Will saturate Sr＝100％，
Substituting the parameters into a formula (7) to obtain the initial water content of the first layer of slurry soil body of the model foundation
The calculation process is a determination step of the initial mud state and the consolidation compressive stress of the first layer of soil body of the model foundation, and the calculation processes of the initial mud state and the consolidation compressive stress of the rest layers of soil bodies of the model foundation are the same and are not repeated here. The specific calculation result is shown in table 1, table 1 is a calculation parameter table of soil bodies of each layer of the prototype and model foundation, and the meanings of the formulas in the table are the same as the meanings in the previous step.
TABLE 1
And sixthly, after all layers of slurry soil bodies are prepared, pouring the prepared slurry soil bodies into the model box in sequence, carrying out layered consolidation according to the determined consolidation compressive stress, and pouring the next layer of slurry soil body into the model box for compression consolidation after the compression consolidation of the soil body at the bottommost layer is completed each time. In layered compression consolidation, sensors can be embedded at specific locations as desired. And completing the preparation of the whole model foundation after the soil bodies of all layers of the model foundation are sequentially compressed and consolidated.
Claims (5)
1. A clay model foundation preparation method for recovering prototype state and strength is characterized by comprising the following steps: the method comprises the following steps:
s1: determining the total thickness h of the prototype foundationpAnd total thickness h of model foundationmLayering the soil body of the prototype foundation and the soil body of the model foundation to obtain the soil body of each layer of the prototype foundation and the soil body of the same layer corresponding to the model foundation, wherein m represents the model foundation, and p represents the prototype foundation;
s2: carrying out an in-situ cross plate shear test on each layer of soil body of the prototype foundation to obtain the non-drainage shear strength of the middle part of each layer of soil body of the prototype foundation
S3: controlling the non-drainage shear strength of each layer of soil body of the model foundation to be equal to the non-drainage shear strength of the middle part of the soil body of the same layer corresponding to the prototype foundation, calculating the super-consolidation ratio of each layer of soil body of the prototype foundation according to the relation between the non-drainage shear strength of the middle part of each layer of soil body of the prototype foundation and the super-consolidation ratio, using the super-consolidation ratio as the super-consolidation ratio of each layer of soil body corresponding to the same layer of the model foundation, and then calculating the state parameter of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation pressure stress;
s4: determining the slope lambda of a compression consolidation line and the slope kappa of an unloading rebound line of each layer of soil body of the prototype foundation under an e-lnp semilogarithmic coordinate system, drawing the state parameters of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation in an e-lnp coordinate system, and obtaining the initial pore ratio of each layer of soil body of the model foundation by reversely deducing the unloading rebound slope and the slope of the compression consolidation line
S5: and preparing the model foundation layer by layer according to the initial slurry state of each layer of soil body of the model foundation and the consolidation pressure stress of each layer of soil body of the model foundation, and preparing the gap embedding sensor in the model foundation layer by layer.
2. The clay model foundation preparation method for recovering prototype state and strength according to claim 1, wherein:
in step S1, layering the prototype foundation soil body and the model foundation soil body, specifically including the steps of:
dividing the prototype foundation and the model foundation into n layers to obtain each layer of soil body of the prototype foundation and the soil body of the same layer corresponding to the model foundation, and determining the geometric similarity ratio of each layer of thickness of the model foundation to the same layer of thickness of the prototype foundation according to the total thickness of the prototype foundation and the size of a model box as lambda; the thickness of each layer of soil body of the prototype foundation isThe thickness of the model foundation corresponding to the soil body of the same layer is reduced by lambda timesWhere k is 1,2 … … n, k represents the number of soil layering from top to bottom, and n represents the total number of layering.
3. The clay model foundation preparation method for recovering prototype state and strength according to claim 1, wherein:
in step S3, the state parameters of the middle part of each layer of soil body of the prototype foundation are The pore ratio of the middle part of each layer of soil body of the prototype foundation is obtained;
mean effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation(ii) a The determination of the state parameters of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation comprises the following steps:
s31: carrying out an indoor basic physical property test on each layer of soil body of the prototype foundation to obtain the specific gravity and the floating density of each layer of soil body of the prototype foundation;
s32: the effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation is obtained by adopting the following formula:
wherein k represents a soil layering number from top to bottom, and k is 1,2 … … n;
the floating density of the j layer soil body of the prototype foundation; g is the local gravitational acceleration;the thickness of the k layer soil body of the prototype foundation; j represents the traversal sequence number of the soil body of the k layer, and j starts from 0;representing the effective dead weight compressive stress of the middle part of the kth layer soil body of the prototype foundation;represents the thickness of the j-th layer soil body of the prototype foundation,representing the floating density of the k layer soil body of the prototype foundation;
s33: calculating the porosity ratio of the middle part of each layer of soil body of the prototype foundation by adopting the following formula:
in the formula (I), the compound is shown in the specification,the pore ratio of the middle part of the k layer soil body of the prototype foundation;the floating density of the k layer soil body of the prototype foundation; rhowIs the density of water; dskThe specific gravity of the k layer soil body of the prototype foundation;
s34: the super consolidation ratio of the middle part of each layer of soil body of the prototype foundation is obtained by adopting the following formula
In the formula (I), the compound is shown in the specification,the normalized non-drainage shear strength of the test slurry soil body during normal compression consolidation is shown, and NC represents normal consolidation;
representing the undrained shear strength of the k-th soil body of the prototype foundation,representing the effective self-weight pressure stress of the kth layer soil body of the prototype foundation; b is a pending parameter;
s35: controlling the consolidation ratio of each layer of soil body of the model foundation to be equal to that of each layer of soil body of the corresponding prototype foundation, and then calculating the effective consolidation compressive stress of each layer of soil body of the model foundation by adopting the following formula:
in the formula (I), the compound is shown in the specification,representing the ultra-consolidation ratio of each layer of soil body of the model foundation;representing the effective self-weight pressure stress of the kth layer soil body of the prototype foundation;representing the effective consolidation compressive stress of the k-th layer soil body of the model foundation;
s36: respectively calculating the average effective dead weight compressive stress of the middle part of each layer of soil body of the prototype foundation and the average effective consolidation compressive stress of each layer of soil body of the model foundation by the following formulas:
in the formula (I), the compound is shown in the specification,the mean effective self-weight stress of the middle part of the kth layer soil body of the prototype foundation;
the average effective consolidation compressive stress of the k layer soil body of the model foundation; k0The static soil pressure coefficient of the prototype foundation soil body;is a prototypeEffective self-weight compressive stress of the middle part of the kth layer soil body of the foundation;
the effective consolidation compressive stress of the k layer soil body of the model foundation.
4. The clay model foundation preparation method for recovering prototype state and strength according to claim 1, wherein: in step S4, the determination of the initial void ratio of each layer of soil body of the model foundation includes the following steps:
s41: taking a prototype foundation soil body indoors, preparing a slurry sample, and then performing an indoor compression consolidation test and an unloading rebound test on the slurry sample to obtain a compression consolidation line slope lambda and an unloading rebound line slope kappa;
s42: the state parameters of the middle part of each layer of soil body of the prototype foundation obtained in the step S3 are processed
And the average effective consolidation compressive stress of each layer of soil body of the model foundation is drawn under an e-lnp semilogarithmic coordinate system and passes through
Point drawing parallel lines with the slope equal to the slope kappa of the unloading rebound line are respectively crossed with the average effective consolidation compressive stress of each layer of soil body of the model foundationIn thatWhereinState parameters of each layer of soil body of the model foundation;
s43: state parameter of each layer of soil body of over-model foundationDrawing compression and solidification parallel lines with the slope equal to the slope lambda of the compression and solidification line, and respectively intersecting the compression and solidification parallel lines with the vertical coordinate axisAt least one of (1) and (b); whereinThe initial pore ratio of each layer of soil body of the model foundation in a slurry state before consolidation and compression is obtained.
5. The clay model foundation preparation method for recovering prototype state and strength according to claim 1, wherein: the step S5: in the method, the layered preparation process of the model foundation comprises the following specific steps:
s51: taking a prototype foundation soil body indoors, and obtaining initial water content according to the following formula
Preparing n groups of slurry soil bodies:
wherein the content of the first and second substances,representing the corresponding initial water content when each layer of soil body of the model foundation is in a slurry state before compression and consolidation when the model foundation is prepared in a layered mode; srIs the saturation; dskThe specific gravity of the k layer soil body of the prototype foundation;
the initial pore ratio of each layer of soil body of the model foundation in a slurry state before consolidation and compression; k represents the sequence number of the soil layering from top to bottom, and k is 1,2 … … n;
s52: obtaining the effective consolidation compressive stress of each layer of soil body of the model foundation according to the step S35
And (4) respectively carrying out layered compression consolidation on the n groups of slurry soil bodies prepared in the step (S51) to finish the layered preparation of the model foundation, and burying a sensor in a layered compression consolidation gap.
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