CN108931422B - Measuring and calculating method for lateral extrusion deformation of foundation under roadbed load - Google Patents
Measuring and calculating method for lateral extrusion deformation of foundation under roadbed load Download PDFInfo
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- CN108931422B CN108931422B CN201810392251.7A CN201810392251A CN108931422B CN 108931422 B CN108931422 B CN 108931422B CN 201810392251 A CN201810392251 A CN 201810392251A CN 108931422 B CN108931422 B CN 108931422B
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- G01—MEASURING; TESTING
- 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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/32—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring the deformation in a solid
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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
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0256—Triaxial, i.e. the forces being applied along three normal axes of the specimen
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Abstract
A method for measuring and calculating lateral extrusion deformation of a foundation under roadbed loading relates to a method for synchronously measuring and calculating the lateral extrusion deformation of the foundation under a roadbed slope toe through vertical settlement measured by a settlement plate in a medium-compressibility consolidated soil foundation. The method is mainly designed for solving the problem of large error of modeling calculation by adopting finite element and finite difference software at present. Determining the change rule of the in-situ soil poisson ratio at each depth along with the confining pressure through in-situ sampling and an indoor triaxial test, and determining the poisson ratio according to the roadbed load and the overlying soil layer load; determining the lateral extrusion deformation area of the foundation under the slope toe at each layer depth by a formula: the method is based on a large amount of local layered settlement observation results and combined with theoretical calculation results to correct, so that for a normal consolidated soil area, the value is determined through the theoretical correction coefficient of the layered settlement percentage, and the lateral extrusion deformation in the medium-compressibility normal consolidated soil foundation in the area is determined. The method has the advantage of more accurate measurement and calculation results.
Description
The technical field is as follows:
the invention relates to a method for synchronously measuring and calculating lateral extrusion deformation of a foundation under a roadbed slope toe through vertical settlement measured by a settlement plate in a medium-compressibility consolidated soil foundation.
Background art:
the bearing capacity of the medium-compressibility soil foundation is high, and the foundation settlement is smaller compared with that of soft soil. The distribution area is wide, and the soil is mostly normal consolidated soil (namely, the soil is basically layered according to geological times and is completely consolidated under the existing dead weight pressure, namely, the existing dead weight pressure is equal to the prior consolidation pressure.)
Because the foundation is settled under the load of the roadbed, the soil body synchronously generates lateral extrusion deformation, the deformation has larger influence on side piles and buildings at the slope toe, is particularly obvious in soft soil and has more research data at present; in the medium-compressibility soil, the deformation is often ignored, and hidden troubles are easily brought to roadbed engineering under the condition of a natural foundation.
At present, due to the non-homogeneous and anisotropic foundation and the non-linear characteristic of stress-strain, the lateral extrusion deformation is difficult to accurately predict by the existing calculation means. In the design process, more finite elements and finite difference software are adopted for modeling calculation, but even if the finite elements and the finite difference software are adopted, larger errors exist due to the difficulty in accurate parameter value taking and the limitation of analyzing the actual soil body problem by the elastoplastic model.
In the process of analyzing lateral deformation, the value of the Poisson ratio v is crucial, for the medium-compressive soil body, the value is usually 0.3-0.35 according to experience, practice basis is lacked, and the result is greatly influenced. In fact, for the soil body, the poisson ratio is not a fixed value in the process of compression consolidation, and the change rule of the poisson ratio is accurately determined through a triaxial test.
The invention content is as follows:
the invention aims to solve the technical problem that the lateral extrusion deformation corresponding to observed settlement is calculated by a specific formula on the basis of the Poisson ratio of the observed settlement and the corresponding load state aiming at the defects of the existing measuring and calculating method. Compared with the current elastic theory calculation method, the calculation result is more accurate, the formula is simple and convenient, the required parameters are less, and the calculation method can adapt to the lateral extrusion deformation of the foundation under the roadbed load required by the actual engineering.
The above object is achieved by:
firstly, determining the change rule of the in-situ soil poisson ratio at each depth along with the confining pressure through in-situ sampling and an indoor triaxial test, and determining the poisson ratio according to the roadbed load and the overlying soil layer load; the sampling depth is preferably layered according to foundation soil, 1 group of samples can be taken when the layering thickness is less than 4m, 1 group of samples can be taken when the layering thickness exceeds 4 m;
secondly, determining the lateral extrusion deformation area of the foundation under the toe at each layer depth by the following formula:
in the formula (I), the compound is shown in the specification,
maximum lateral extrusion deformation of the ith layer, wherein hiThe layering thickness of the ith layer is determined by considering the soil layer interface during calculation, and when the thickness of the same type of soil is more than 2m, the layering calculation thickness is not more than 2 m;
RSi-the percentage of the compression of the ith layer of soil in the road relative to the observed value of the settlement plate (i.e. the measured total settlement);
B1/2-1/2 of the length of the roadbed base;
vithe poisson ratio of the ith layer of soil under the current load state is determined by the step (one);
s, observing a settlement value of a foundation surface at the center of the roadbed by a settlement plate;
the method is based on the observation results of a large amount of local stratified settlement and combined with the theoretical calculation results to correct, so that the stratified settlement percentage R of the normal consolidated soil area is obtainedSiTheoretical correction coefficient Δ βR(ii) + 3.12%, to determine R in the formulaSiAnd taking values, and further determining the lateral extrusion deformation in the medium-compressibility common consolidated soil foundation in the region.
The invention has the advantages that: aiming at the defects of complex formula, large error, high instrument observation cost investment and the like of the conventional measuring and calculating method, the method is provided for calculating the lateral extrusion deformation corresponding to the observed settlement through a specific formula on the basis of the Poisson ratio of the observed settlement and the corresponding load state. Compared with the current elastic theory calculation method, the calculation result is more accurate, the calculation is simple and convenient, the required parameters are less, and the method can meet the actual engineering requirements.
Description of the drawings:
FIG. 1 is a depth profile of Poisson's ratio for an embodiment of the present invention;
FIG. 2 is a graph comparing the calculated and measured fractional compression percentages along the depth distribution in the embodiment of the present invention;
FIG. 3 is a depth profile of calculated and measured lateral deformation values according to an embodiment of the present invention.
The specific implementation mode is as follows:
a method for measuring and calculating lateral extrusion deformation of a foundation under roadbed loading comprises the following steps:
firstly, determining the change rule of the in-situ soil poisson ratio at each depth along with the confining pressure through in-situ sampling and an indoor triaxial test, and determining the poisson ratio according to the roadbed load and the overlying soil layer load; the sampling depth is preferably layered according to foundation soil, 1 group of samples can be taken when the layering thickness is less than 4m, 1 group of samples can be taken when the layering thickness exceeds 4 m;
secondly, determining the lateral extrusion deformation area of the foundation under the toe at each layer depth by the following formula:
in the formula (I), the compound is shown in the specification,
maximum lateral extrusion deformation of the ith layer, wherein hiThe layering thickness of the ith layer is determined by considering the soil layer interface during calculation, and when the thickness of the same type of soil is more than 2m, the layering calculation thickness is not more than 2 m;
RSi-the percentage of the compression of the ith layer of soil in the road relative to the observed value of the settlement plate (i.e. the measured total settlement);
B1/2-1/2 of the length of the roadbed base;
vithe poisson ratio of the ith layer of soil under the current load state is determined by the step (one);
s, observing a settlement value of a foundation surface at the center of the roadbed by a settlement plate;
the method is based on the observation results of a large amount of local stratified settlement and combined with the theoretical calculation results to correct, so that the stratified settlement percentage R of the normal consolidated soil area is obtainedSiTheoretical correction coefficient Δ βR(ii) + 3.12%, to determine R in the formulaSiAnd taking values, and further determining the lateral extrusion deformation in the medium-compressibility common consolidated soil foundation in the region.
Example (b): the main soil layers in the area are as follows: the surface layer is mostly clay or silty clay, hard and hard, the thickness is 2-8 m, and the local part is gravel soil. The following layers of the surface layer are impact soil layers: cohesive soil, sand, gravel and pebble soil are used as main materials, the alluvial thickness is generally 5-30 m, and the local thickness exceeds 50 m. The roadbed filling adopts A, B groups of filling to fill, the roadbed design filling height is 6.4m, the roadbed bottom width B is 46m, and the gradient is 1: 1.5. The underground water line is 4.0m, and the foundation is normal consolidated soil;
2. poisson ratio indoor test determination:
in order to measure and calculate the extrusion condition of the foundation soil body under the slope toe on both sides by combining the settlement observation result, the measuring and calculating method is adopted, and firstly, an indoor triaxial test is carried out on an original state soil sample (saturated sample below the water level line) obtained in situ. According to the results of the indoor continuous loading triaxial consolidation test, under the load state of the working condition, the Poisson ratio is distributed along the depth as shown in figure 1;
calculating the lateral extrusion deformation:
the thickness of the layered calculation is taken to be 2m, and the layered calculation is substituted into the formula provided by the invention to solve the problem:
the total settlement S before the roadbed center is cut off and the track is paved can be measured by a settlement plate buried in the ground before the roadbed is filled, wherein the total settlement S is 122mm and the half width B of the roadbed bottom is 122mm1/223m according toThe layered settlement calculation is carried out by the standard method in the existing building foundation basic design standard GB 50007-2011, and a compensation correction coefficient delta β is adoptedRAlgebraically correct for + 3.12%, then the compression percentage R of each layer is calculatedsiThe distribution with depth is shown in figure 2;
the calculation result of the maximum lateral extrusion deformation at the slope toe of each layer can be obtained after the formula is substituted, and the calculation result is shown in figure 3 by comparing with the actually measured lateral deformation of the inclinometer.
In conclusion, due to the characteristic that the lateral extrusion deformation is calculated in a layered mode by the method, the fact that the depth and the size of the lateral deformation measurement and calculation are very close to those of the lateral extrusion deformation of the foundation under the slope toe of the roadbed observed by the inclinometer is guaranteed, and the method combining theoretical calculation and empirical parameters effectively avoids serious errors of the theoretical value and the measured value of the lateral deformation in the aspects of depth, size and the like in elastic calculation and elastoplastic simulation calculation.
Claims (1)
1. The measuring and calculating method of the lateral extrusion deformation of the foundation under the roadbed load is characterized by comprising the following steps:
firstly, determining the change rule of the in-situ soil poisson ratio at each depth along with the confining pressure through in-situ sampling and an indoor triaxial test, and determining the poisson ratio according to the roadbed load and the overlying soil layer load; the sampling depth is layered according to foundation soil, 1 group of samples are taken when the layering thickness is less than 4m, 1 group of samples are taken when the layering thickness exceeds 4 m;
secondly, determining the lateral extrusion deformation area of the foundation under the toe at each layer depth by the following formula:
in the formula (I), the compound is shown in the specification,
maximum lateral extrusion deformation of the ith layer, wherein hiThe layering thickness of the ith layer is determined by considering the soil layer interface during calculation, and when the thickness of the same type of soil is more than 2m, the layering calculation thickness is not more than 2 m;
RSi-the percentage of the compression of the ith layer of soil in the road relative to the observed value of the settlement plate;
B1/2-1/2 of the length of the roadbed base;
vithe poisson ratio of the ith layer of soil in the current load state is determined by the first step;
s, observing a settlement value of a foundation surface at the center of the roadbed by a settlement plate;
based on the observation results of a large amount of local stratified settlement, the theoretical calculation results are combined for correction, so that the stratified settlement percentage R of the normal consolidated soil area is obtainedSiTheoretical correction coefficient Δ βR(ii) + 3.12%, to determine R in the formulaSiAnd taking values, and further determining the lateral extrusion deformation in the medium-compressibility common consolidated soil foundation in the region.
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| CN109211669A (en) * | 2018-10-26 | 2019-01-15 | 淮阴工学院 | The often measuring method that lateral extrusion deforms in consolidation batt ground |
| CN110567429A (en) * | 2019-09-25 | 2019-12-13 | 辽宁工程技术大学 | Device and method for measuring actual Poisson ratio of foundation soil body under lateral limit stress condition |
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