RU2631445C2 - Method for determining number of workings while conducting engineering and geological surveys - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method for determining the number of workings while conducting engineering and geological surveys includes driving the workings within the spot of a building or a structure to be projected, determining the soil deformation modulus, finding the settlement of the building or the structure at each working and the settlement unevenness between the workings, finding the base stiffness coefficient at each working at the predetermined sizes in the plan of the building or the structure and the load on the base, using at that Shephard's function for the base hardness coefficient in the form of a reduced dependence.

EFFECT: improving the accuracy of engineering and geological surveys, reducing the labour intensity and expanding the scope of application.

3 cl, 1 tbl, 6 dwg

Description

The invention relates to the field of construction and is intended to determine the number of workings, precipitation and roll of buildings during engineering and geological surveys.

There is a method of determining the zone of possible failure in soils according to the copyright certificate SU No. 1752869 A1 (IPC E02D 1/02, 08/07/1992), including testing the soil at several points of the studied area, determining its characteristics, their mathematical processing and determining the location and size of the failure zones, soil testing is carried out by sensing to determine the penetration resistance of the probe cone into the soil and determine the coordinates of the center of the circular zone, inside which will be the center of a possible failure.

The disadvantage of this method is that soil testing is performed by immersing the cone of the probe with the determination of the conditional dynamic resistance of the soil without determining the required number of sensing points and workings.

There is a method of determining the number of workings in engineering-geological surveys for the design and installation of pile foundations and determining the volume of surveys (Instructions for engineering-geological and surveys in Moscow, 2004), in which the volume of surveys depends on three categories of complexity of soil conditions depending on soil uniformity according to bedding conditions and properties.

The first category includes a single-layer or multilayer composition of the thickness of soils with almost horizontal or slightly inclined layers (slope no more than 0.05), and within each layer, the soils are uniform in properties.

The second category includes a single-layer or multilayer composition of the thickness of soils with insufficiently maintained boundaries between the layers (slope of not more than 0.1), and within the layers the soils are heterogeneous in properties.

The third category includes soil strata with a multilayer composition and heterogeneous properties with unstable boundaries between the layers (slope greater than 0.1), and individual layers can wedge out.

Moreover, the assessment of the category of complexity of soil conditions at the construction site is based on the materials of geological funds.

The disadvantage of this method is that at the initial stage of the survey, stratigraphy of the soil stratum is unknown and it is impossible to determine the category of complexity of soil conditions in the absence of geological funds, which takes place in undeveloped territories.

Closest to the technical nature of the invention is a method for determining the number of workings described in SP 47.13330 (Engineering surveys for construction, 2013). According to this method, the number of workings and the distances between them are determined by regulatory requirements using tabular values depending on the complexity category of engineering and geological conditions.

According to the method, the number of workings within the contour of each building and structure is determined: for category I complexity of engineering and geological conditions - 1-2 workings; for category II - at least 3-4; for category III - the number of mine workings is determined by the construction of a particular foundation, the loads on the foundation and the engineering and geological conditions, but not less than 4-5, taking into account the geometric dimensions of the object. Depending on the complexity category of engineering and geological conditions, the distance between the workings (wells, pits, pipes, etc.) varies from 25 to 100 m.

The disadvantages of this method include the fact that the complexity categories of engineering and geological conditions are given on the basis of geological and hydrogeological processes that affect the conditions of construction and operation of buildings and structures. These conditions do not have a quantitative description and are not related to factors determining the behavior of buildings during their construction and subsequent operation, such as settlement and roll of a building or structure, which can lead to a violation of the normal operating conditions of buildings. The number of workings, in this case, is determined without taking into account the interaction of soils with the building or structure and the properties of soils, which can significantly differ in soils between workings. In most cases, the “envelope” rule is used for buildings and structures - four workings around the perimeter of the projected object and one in the center of the development spot. The working depths are assigned according to tabular values depending on the type of foundation, the magnitude of the expected load and varies from 4 to 26 m, but does not depend on the type of soil, its properties and the distribution of additional stresses in the base from the load.

Performing geotechnical surveys (ISI), geologists take measurements in the workings in the field or by testing selected monoliths in the laboratory, i.e. in an extremely small relative volume of soil under the structure (of the order of millionths of the volume of the soil mass under the building or structure). Then, these IGI data are randomly and subjectively (i.e. ambiguously) extrapolated to the entire base volume when constructing stratifications in the form of engineering geological elements (IGE) and / or calculated geological elements (EGE). Moreover, at close points of the base, the determined characteristics can vary greatly, but the repeatability of the test results when performing the ISI is not checked despite the wide variation in the measured values.

The technical task of the present invention is to improve the accuracy of engineering and geological surveys, reducing the complexity and expanding the scope.

The problem is solved in that the required number of workings and their depth are determined based on the calculation of draft, uneven draft and roll of the designed building directly in the process of driving the workings.

The method is as follows.

A drilling rig is installed at the site of engineering and geological surveys and development is conducted, for example, in the form of a well anywhere on the spot of the designed building or structure. In the process of excavation, the soil is tested with a stamp, for example, by the method of drilling sounding according to patent RU No. 233314 C1 (IPC E02D 1/02 of 07/27/2012) with the determination of the deformation modulus at specified intervals in depth. Take a building or structure together with the foundation for a rigid block with specified dimensions in terms of plan and load on the base and calculate the draft by the method of layer-by-layer summation. The stiffness coefficient of the base for a given output is calculated. Arbitrarily, within the spot of a building or structure, for example, at corner points, new workings pass with the determination of draft and stiffness coefficient of the base. Use the Shepard function and found on the workings of the stiffness factors of the base for extrapolation to the entire surface of the base under the building or structure. Tunneling and soil testing continue until, when the number of excavations is three or more, with different values of the shape parameter of the Shepard function approximation, the distribution of the stiffness coefficient of the base, an acceptable representative scatter of the calculated values of the average and uneven building sediments and their heels is reached.

The proposed method eliminates the disadvantages of traditional methods of engineering and geological research:

- Uncertainty when choosing the number of workings associated with the exclusion of soil properties, sizes and additional stresses in the base from the loads of the designed building or structure at their designation;

- excludes the selection of monoliths, their transportation and laboratory tests, which reduces the complexity of engineering and geological research, since all studies are carried out in the field on soils with undisturbed structure;

- the scope of application is expanding, so in the process of engineering and geological research, the precipitation and banks of the building and structures are determined, which designers can use when assigning the dimensions of the foundations;

- excludes the presentation of engineering-geological sections with the allocation of IGE. This subjective operation is performed during desk processing of survey materials for a limited amount of soil with an arbitrary extrapolation of the values of soil characteristics between excavations, the accuracy of which depends only on the experience of the geologist and is not related to the properties of the studied soils.

The invention is illustrated by graphic materials, which show the following:

in FIG. 1 shows a plan of the designed building with the location of the normative workings;

in FIG. Figure 2 shows an example of the depth distribution of the deformation modulus in a mine;

in FIG. 3 shows the results of calculating the settlement of the foundation according to the results of studies on one mine;

in FIG. 4 shows the results of calculating the draft and heel of the foundation according to the results of studies on two workings;

in FIG. 5 shows a plan of the designed building with the location of additional workings;

in FIG. Figure 6 shows an example of a map of isopoles of the stiffness coefficient of a base constructed from nine workings for a structure 40 × 20 m in size.

An example of the implementation of a technical solution.

As an example of the implementation of the proposed method, the determination of the number of workings during engineering and geological surveys at the construction site of a residential building is considered:

- the building is rectangular in plan with dimensions in plan L = 40 m and b = 20 m and average pressure on the base q = 300 kPa;

- a slab foundation with dimensions equal to the dimensions of a residential building in plan;

- the plan of the designed building with the location of the normative workings is shown in FIG. one.

Engineering and geological surveys are carried out by digging workings in the form of wells and soil tests according to the following procedure.

1. The first mine is drilled anywhere on the spot of the building, for example, in the center of the projected building. Production number 1 (B1) in FIG. one.

2. In the process of sinking at the depths specified by the technical task, for example, through 0.5 m in depth, the soil deformation modulus is determined by one of the known methods, for example, by the method of drilling sounding according to patent RU 2541977 C2 (IPC E02D 1/02 of 07/27/2012 )

3. Using the found values of the deformation moduli, a profile of the change in the deformation modulus with depth is constructed (Fig. 2). Such profiles can be obtained at any point of the spot of a building or structure, including along the perimeter of the building, for example, in the workings shown in FIG. 1 and FIG. 6.

4. The building is accepted together with the foundation as a rigid block with the given width (b) and length (L) and average pressure under the sole (q).

5. The settlement of the base of the building (s) is found using the design scheme in the form of a linearly deformable half-space according to SP 22.13330-2011 (Foundations of buildings and structures, 2011):

where E _i is the deformation modulus;

σ _{zp, i} - stresses from pressure under the sole of the foundation at the i-th depth of h _i tests;

Δh _i = h _i -h _i-1 .

When determining the draft, the additional stresses σ _zp in the base vertically passing through the center of the sole of the foundation of the building or structure (Fig. 3) are found in accordance with SP 22.13330-2011 (Foundation of buildings and structures, 2011) by the expression

σ _zp = α⋅q,

where α is the tabular coefficient;

q is the average pressure on the base.

6. Excavation of the mine continues, testing of the soil, determination of the deformation modulus, and calculation of settlement of the building or structure until the difference in settlement ΔS = S _i -S _i-1 reaches a predetermined accuracy parameter, for example, 3-5%. Depth H in FIG. 3, 4.

7. The work is repeated according to points 2-6 at the next additional development, at any point on the spot of a building or structure, for example, at a corner point, development B2 (Fig. 1). When determining the precipitation of the corner point of a building or structure, additional stresses σ _{zp, c} in the base are determined in accordance with SP 22.13330-2011 (Foundation of buildings and structures, 2011) by the expression

σ _{zp, c} = α⋅q / 4.

If the new mine is located near an existing building or structure, then to account for the influence of neighboring buildings, additional stresses are determined in accordance with SP 22.13330-2011 (Foundations of buildings and structures, 2011) by the expression:

where σ _{zp, αi} are the vertical stresses from the neighboring foundation or loads;

k is the number of influencing foundations or loads.

8. Using the found values of sediment on the previous and new development find the difference in sediment (Fig. 4)

ΔS = S _B1 -S _B2 ;

and the relative difference in precipitation according to SP 22.13330-2011 (Foundations of buildings and structures, 2011) from the expression

- расстояние между выработками В1 и В2.Where

- the distance between the workings B1 and B2.

9. Perform work according to points 2-8 at the following workings, which are introduced arbitrarily within the spot of the building, for example, at corner points, or around the perimeter of the building or structure.

10. Using the found values of the sediment of the building or structure for each mine, find the corresponding stiffness factors of the base in the mine. Such workings 5 in the first case (Fig. 1) and 9 in the second (Fig. 5). The stiffness coefficients of the base in the workings are found from the expression

where s is the sediment found in paragraph 5;

11. The found values of the stiffness coefficients of the base and the Shepard function are used (D. Shepard. A two dimensional interpolation function for irregularly-spaced data // ACM National Conference, 1968, pp 517-524), the stiffness factors K _i found in the workings are extrapolated on the entire contact surface of the soles of the foundation of the building or structure with the base.

where X, Y are the coordinates of the workings;

x, y - the current coordinates of the approximation points between the workings;

n is the parameter of the shape of the distribution of the interpolation function between the workings;

N + 1 - the number of workings;

K _i - stiffness coefficient of the base on the i-th output;

For the case of N = 9 workings, the result is shown in FIG. 6.

12. Find the precipitation and heel of the building or structure, taking into account all the workings completed, from solving the system of equations of equilibrium of the building or structure under the action of an average pressure q = 300 kPa applied to the base with a distribution of stiffness coefficient KK (x, y, n, N) , the resultant of which Q = P⋅L⋅B = 40 × 20 × 300 = 24000 kN, from a building with dimensions in plan L = 40 m and B = 20 m. The solution to this problem is reduced to solving a system of three linear equilibrium equations for a rigid structure at basis characterized by a variable stiffness coefficient over the contact area of the building or a construction with a base. This system of equations in matrix notation has the form

G × a = F,

where G is the equilibrium matrix;

a - determined rolls and draft;

F is a column of free terms defined as moments around the X, Y axes and the resultant of the external load Q;

In the matrix, the roll values are shown from top to bottom: longitudinal - around the Y axis and transverse - around the X axis, in the bottom line of the draft of the lower left corner of the building. The positive directions of the rolls coincide with the positive directions of the coordinate axes (X, Y).

The terms of the matrix G are found from the expression

Calculations of sediments and rolls of the structure were performed at various values of the parameter of the shape of the distribution of the values of the stiffness coefficient of the base n between the workings.

The calculation results are presented in table 1.

The values of the transverse rolls significantly depend on the value of the parameter n, which determines the shape of the distribution of the stiffness coefficient of the soil of the base between the workings, where the soil test was not performed.

In the considered example, the values of the transverse rolls differ by a factor of two for n = 1 and n = 4. The permissible roll, according to SP 22.13330-2011 (Foundations of buildings and structures, 2011), is 0.003.

This example shows that the distribution of values of soil parameters at the base is impractical to represent as stratification with IGE / EGE, they are not in FIG. 3 and FIG. 4. It is advisable to exclude this operation, and present the data of engineering-geological surveys in the form of a distribution of the stiffness coefficient of the base and carry out a calculation for each number of mines that have been completed, which can be done in the process of engineering-geological surveys, in the field, using the above-described algorithm for calculating sediments and rolls of the building, built into an automated installation for driving workings. This will reduce the time of work due to the abandonment of laboratory tests of soil samples, other office work while increasing the economic efficiency of engineering and geological surveys.

In addition, this will ensure close interaction between survey geologists and design engineers, since in the process of engineering and geological surveys the values of draft and heel of the designed building or structure will be found.

This invention is industrially feasible, has new, wider functionality, increases accuracy and reduces the complexity of engineering and geological surveys.

Claims (7)

1. A method for determining the number of workings during engineering and geological surveys includes driving workings within the spot of the designed building or structure, determining the soil deformation modulus of the workings, finding the draft of the building or structure at each workout and uneven settlement between workings, finding the stiffness coefficient of the base on each development at a given size in the plan of the building or structure and the load on the base, using the Shepard function for the stiffness coefficient innovations in the form of

2. A method for determining the number of workings during geotechnical surveys according to claim 1, characterized in that the draft and the heels of the building or structure are found by solving the system of equilibrium equations with a variable stiffness coefficient of the base according to the contact area of the foundation of the building or structure with the base G × a = F,

3. A method for determining the number of workings during engineering and geological surveys according to claim 1, characterized in that, according to the stiffness coefficient values found in the workings, using Shepard's approximating function with free shape parameter (s), several options for the distribution of the base stiffness coefficient are determined , vary the values of the shape parameter (s) and for each of them, solving a system of three equations of equilibrium of a rigid block in displacements, find the draft and heels, and if the resulting spread is not permissible, then additional production is introduced, and the process is repeated until representative values of the sediments and rolls of the building or structure are obtained.

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