Mudstone lateral expansive force tester and mudstone roadbed deformation calculation method

Abstract

The invention discloses a mudstone lateral expansive force tester and a mudstone roadbed deformation calculation method, the mudstone lateral expansive force tester comprises a fixing system and a measuring system, and the mudstone roadbed deformation calculation method comprises the step of calculating mudstone vertical elastic extrusion deformation and mudstone center soil body bending deformation. The mudstone lateral expansive force tester disclosed by the invention can quickly measure the lateral expansive force of mudstone under humidification deformation, the structure is simple, the applicability is wide, and when the mudstone roadbed deformation is calculated based on the lateral expansive force, the calculation error can be further reduced, and the actual expansive deformation can be accurately estimated.

Description

Technical Field

[0001] The invention belongs to the technical field of roadbed engineering, and relates to a mudstone lateral expansion force tester and a mudstone roadbed deformation calculation method. Background Art

[0002] The deformation problem of mudstone roadbed has always been one of the major engineering problems in the field of geotechnical engineering and engineering geology. When mudstone encounters water or becomes wet, its volume will expand, which will cause a series of problems such as roadbed cracking and deformation. In addition, its distribution range is extremely wide, which has a great negative impact on the construction of roadbed and pavement structure, and also poses a great safety hazard to the later use of roads.

[0003] The existing methods for measuring swelling force include swelling counterpressure method, balanced pressure method and constant volume method. Compared with other measurement methods, the measurement results of constant volume method are more accurate and more referenceable. However, among the many measuring instruments currently available, they all measure the vertical swelling force of clay and original soil, and there is no instrument for detecting the lateral swelling force of mudstone. Therefore, there is an urgent need for a lateral swelling force measuring device for mudstones with different water contents.

[0004] For the calculation of wetting deformation of mudstone roadbed, the existing prediction and evaluation methods are mainly the following:

[0005] (1) Use the improved swelling and shrinking instrument to carry out swelling and shrinking experiments on some soil samples;

[0006] (2) Establish a finite element model through numerical simulation to predict the expansion deformation of mudstone roadbed, and perform prediction analysis based on the model output results;

[0007] (3) An empirical formula is used to reflect the deformation characteristics of mudstone roadbed.

[0008] Although the above method can be used to predict the expansion deformation of mudstone roadbed, it still has many shortcomings and deficiencies. For example, the boundary conditions of the numerical model are difficult to set, and the roadbed deformation under actual conditions cannot be accurately predicted by experiments alone. The empirical formula has low calculation accuracy, and the calculated deformation is uniform deformation, which does not conform to the actual deformation of the project and is difficult to accurately predict the actual expansion deformation.

[0009] Therefore, it is particularly important in the field of roadbed engineering to design a device to measure the lateral expansion force of mudstone with different water contents and a method to calculate the deformation of mudstone roadbed at different wetting depths. Summary of the invention

[0010] The purpose of the present invention is to provide a mudstone lateral expansion force instrument and a mudstone roadbed deformation calculation method to solve the problem that the current expansion force tester cannot measure the lateral expansion force of mudstone and the calculation result of the wetting expansion deformation of the mudstone roadbed is inaccurate.

[0011] The technical solution adopted by the present invention is a mudstone lateral expansion force tester, comprising an L-shaped fixed base, a square groove is provided in the L-shaped fixed base, a storage chamber is arranged in the square groove, the interior of the storage chamber is hollow, openings are arranged at the left and right ends of the storage chamber and the middle opening of the top plate, the mudstone to be tested is arranged inside the storage chamber, a left permeable stone is arranged at the opening at the left end of the storage chamber, and a right permeable stone is arranged at the opening at the right end of the storage chamber, and the storage chamber is connected to a humidistat through a hose arranged at the opening on one side of the top plate.

[0012] Furthermore, a perforated partition is arranged on the upper ends of the left permeable stone and the right permeable stone, and the bottom of the micrometer passes through the middle opening of the top plate of the storage chamber and the perforated partition in sequence to contact the mudstone to be measured. A left mechanical sensor is arranged on the outside of the left permeable stone, and a right mechanical sensor is arranged on the outside of the right permeable stone. A hole is arranged at one end of the L-shaped fixed base, and one end of the screw passes through the hole of the L-shaped fixed base and the knob contacts one of the mechanical sensors. The knob drives the screw to be screwed out and screwed in, and the other end of the screw is fixed to the outside of the L-shaped fixed base through a nut.

[0013] Another technical solution adopted by the present invention is a method for calculating the deformation of a mudstone roadbed based on a mudstone lateral expansion force tester. The mudstone roadbed includes mudstone and its overlying surface layer. When significant bedding can be observed in the mudstone, the calculated thickness is calculated according to the thickness of each bedding layer. Since the mudstone absorbs water and expands, the calculated bedding thickness is calculated according to the thickness after wetting deformation. When calculating by layers, the thickness of each layer is s. i =d i +d i ε c , where s i is the thickness of each layer divided after wetting deformation, d i is the thickness of each layer before wetting deformation, i is the number of layers, from top to bottom: 1, 2, ..., i-1, i, ε c is the deformation strain of mudstone due to wetting, c is the displacement of mudstone after wetting deformation, δ is the thickness of mudstone before wetting deformation, and the implementation is as follows:

[0014] S1. The lateral expansion stress of mudstone is measured using a mudstone lateral expansion force tester;

[0015] S2, calculate the vertical elastic extrusion deformation of mudstone based on the lateral expansion force of mudstone;

[0016] S3. Calculate the bending deformation of the soil in the center of the mudstone based on the lateral expansion force of the mudstone.

[0017] Furthermore, in S2, calculating the vertical elastic compression deformation of mudstone includes the following steps:

[0018] S21. Calculate the strain ε of the measured mudstone layer ii for:

[0019]

[0020] σ yi =γ 1 h+γ 2 z i =ρ 1 gh+ρ 2 gz i

[0021] Where E is the elastic modulus of mudstone, σ yi is the vertical stress of the i-th layer of bedding, υ is Poisson's ratio, p is the lateral expansion stress of mudstone, γ 1 is the weight of the overlying surface layer, γ 2 is the weight of mudstone, h is the thickness of the overlying layer, z i The depth of the i-th bedding layer from the top of the mudstone embankment, ρ 1 is the density of the overlying surface, ρ 2 is the density of mudstone, g is the acceleration due to gravity;

[0022] S22. Calculate the vertical displacement of the bedding:

[0023] y i =ε i s i

[0024]

[0025] In the formula, y i is the vertical displacement of the i-th layer, α is the moisture expansion coefficient, Δω is the change in mudstone moisture content; s i is the thickness of the i-th bedding plane;

[0026] S23. Calculate the vertical elastic extrusion deformation y of mudstone as:

[0027]

[0028] Where n represents the total number of layers.

[0029] Furthermore, in S3, calculating the bending deformation of the mudstone center soil mass includes the following steps:

[0030] S31. Calculate the mudstone stiffness D as:

[0031]

[0032] In the formula, is the deflection coefficient of mudstone, υ is Poisson’s ratio, E is the elastic modulus of mudstone, and I is the moment of inertia of the section;

[0033] S32. Calculate the bending deformation f(x) of the mudstone center soil as:

[0034] f(x)=f 1 (x)+f 2 (x)

[0035] f 1 (x) represents the deflection deformation of mudstone under lateral compression, f 2 (x) represents the deflection deformation of the mudstone overlying layer under load, and x represents the position of the lateral coordinate of the mudstone roadbed.

[0036] Furthermore, in S32, the deflection deformation of the mudstone under lateral pressure is calculated, specifically:

[0037] Taking the width of mudstone roadbed L as unit 1, the lateral compressive stress σ of the soil in the center of the i-th layer is i for:

[0038]

[0039] Where p is the lateral expansion stress of mudstone, K 1 is the static lateral pressure coefficient of the overlying layer, K 2 is the static lateral pressure coefficient of mudstone, γ 1 is the weight of the overlying surface layer, γ 2 is the weight of mudstone, z i The depth of the i-th bedding layer from the top of the mudstone roadbed, h is the thickness of the overlying surface layer;

[0040] When the soil at the center of the bedding is under pressure at both ends, the bending deformation can be approximately regarded as a slender rod with hinged constraints at both ends, and the deflection relationship can be expressed as:

[0041] f 1 "(x)+k i 2 f 1 (x) = 0

[0042]

[0043] In the formula, k i F i The square root of the ratio to D is an intermediate parameter with no practical significance; i is the horizontal external force acting on the soil at the center of the i-th layer; EI is the bending stiffness of the soil layer;

[0044] When x=0 or x=L, the deflection deformation is 0, and the deflection relationship can be obtained by analytical calculation:

[0045]

[0046] Among them, Ai To simplify the parameter values,

[0047] Furthermore, in S32, the deflection deformation of the mudstone under the overlying load is calculated, specifically:

[0048] If the thickness of each layer is the same, the size of the upwarp deformation of each layer is equal, the layers are in contact with each other and there is no compression, that is, the horizontal external force F on each layer is equal, and the simplified parameter value A of each layer is i Under the reduction effect of the upper surface layer on the lower deformation, the layers interact with each other and produce the same deformation. At this time, the deflection deformation of the soil at the center of each layer is the same, and the reduction value of the upper surface layer load is evenly distributed in each layer, then:

[0049]

[0050] Where q is the self-weight stress of the bedding, m 层 is the bedding quality, q t is the average reduction value of the overlying surface load, q m is the overlying surface load reduction value, m is the mass of the overlying surface layer, and L is the width of the mudstone roadbed;

[0051] If the thickness of each layer is different, the layers are squeezed against each other, and the overburden load is the overburden surface load and the overburden layer load, then the overburden load q on the i-th layer is i for:

[0052]

[0053] In the formula, ρ 1 is the density of the overlying surface, ρ 2 is the density of mudstone, h is the thickness of the overlying surface layer, g is the gravity acceleration, and n is the total number of layers;

[0054] When i=1, the deflection deformation of the first layer of bedding under the overlying load is:

[0055]

[0056] When 1<i≤n, the deflection deformation of the i-th layer of bedding under the overlying load is preliminarily calculated as:

[0057]

[0058] The preliminary calculation of the soil deflection deformation at the center of the i-th layer is:

[0059]

[0060] Determine whether the i-1th layer and the ith layer squeeze each other:

[0061] If f i-1 (x)≥f i (x), then the i-1th layer does not compress with the ith layer, and the final deflection deformation of the overlying mudstone layer under load is f 2(i-1) (x);

[0062] If f i-1 (x) <f i (x), the i-1th layer and the i-th layer squeeze each other, and the load of the upper surface layer is redistributed to the first i layers. The distribution relationship of each layer is:

[0063]

[0064] In the formula, q mi is the load reduction value of the upper surface layer of the i-th layer;

[0065] At this time, the deflection deformation under the overlying load of the first i layers is equal. After redistribution, the deflection deformation under the overlying load of the i-th layer is:

[0066]

[0067] The deflection and deformation of the soil in the center of the first i layers are equal. After redistribution, the deflection and deformation of the soil in the center of the i-th layer is:

[0068]

[0069] Determine whether the i-th layer is squeezed by the i+1-th layer:

[0070] If f mi (x)≥f i+1 (x), then the i-th layer does not compress with the i+1-th layer, and the final deflection deformation of the mudstone overlying layer under load is f 2i (x).

[0071] The beneficial effects of the present invention are:

[0072] (1) The present invention provides a mudstone lateral expansion force instrument, which can quickly and conveniently measure the lateral expansion force of mudstone under different humidity conditions while keeping the rock sample volume unchanged, thus filling the gap in the current lack of lateral expansion force measurement and can simultaneously measure the vertical deformation displacement of mudstone. The device has a simple structure and wide applicability, can be placed on any type of rock, has low cost, and can detect data quickly and accurately, thus solving the current problem of lack of lateral expansion force detection of mudstone;

[0073] (2) The present invention provides a method for calculating the deformation of a mudstone roadbed, which comprehensively considers the vertical elastic extrusion deformation of the mudstone roadbed and the bending deformation of the central soil of the mudstone, and calculates the stiffness of the mudstone by the deflection of a rock thin plate. The method is closer to the actual deformation of the mudstone roadbed and has a small relative error with the actual measurement result. The method meets the requirements for calculating the deformation of the mudstone roadbed and improves the accuracy of the wet deformation of the mudstone roadbed. Compared with the traditional calculation method, the method can more accurately and efficiently estimate the wet deformation of the mudstone roadbed and is in line with the actual deformation of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0075] Figure 1 It is a schematic diagram of a mudstone lateral expansion force tester of the present invention;

[0076] Figure 2 It is a schematic diagram of the base of the mudstone lateral expansion force tester of the present invention;

[0077] Figure 3 is a schematic diagram of the road cross-section structure in Test Example 1 of the present invention;

[0078] Figure 4 Schematic diagram of rainwater infiltration depth Z of the road in Test Example 1 of the present invention.

[0079] In the figure, 1 is a perforated partition, 2 is a storage chamber, 3 is a left mechanical sensor, 4 is a left permeable stone, 5 is an L-type fixed base, 6 is a right mechanical sensor, 7 is a knob, 8 is a screw, 9 is a nut, 10 is a right permeable stone, 11 is a hose, 12 is a computer, 13 is a humidistat, 14 is a square groove, 15 is a hole, and 16 is a micrometer. DETAILED DESCRIPTION

[0080] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0081] The present invention provides a mudstone lateral expansion force tester, such as Figure 1 and Figure 2As shown, it includes a fixing system and a measuring system, wherein the fixing system includes an open-hole partition 1, a storage chamber 2, a left permeable stone 4, an L-shaped fixing base 5, a knob 7, a screw 8, a nut 9, a right permeable stone 10, a hose 11, a humidistat 13, and a square groove 14; the measuring system includes a left mechanical sensor 3, a right mechanical sensor 6, a computer 12, a hole 15, and a micrometer 16;

[0082] The L-shaped fixed base 5 has a square groove 14 in which a storage chamber 2 is arranged. The storage chamber 2 is hollow inside, and openings are arranged at the left and right ends of the storage chamber 2 and the middle opening of the top plate. The measured mudstone is arranged inside the storage chamber 2. A left permeable stone 4 is arranged at the opening at the left end of the storage chamber 2, and a right permeable stone 10 is arranged at the opening at the right end of the storage chamber 2. The storage chamber 2 is connected to a humidistat 13 through a hose 11 arranged at an opening on one side of the top plate. Openings are arranged at the upper ends of the left permeable stone 4 and the right permeable stone 10. The bottom of the micrometer 16 passes through the middle opening of the top plate of the storage chamber 2 in sequence, and the perforated partition 1 contacts the mudstone to be measured. A left mechanical sensor 3 is arranged on the outside of the left permeable stone 4, and a right mechanical sensor 6 is arranged on the outside of the right permeable stone 10. One end of the L-shaped fixed base 5 has a hole, one end of the screw rod 8 passes through the hole of the L-shaped fixed base 5, and the knob 7 contacts one of the mechanical sensors. The knob 7 drives the screw rod 8 to be screwed out and screwed in together, and the other end of the screw rod 8 is fixed to the outside of the L-shaped fixed base 5 through a nut.

[0083] The storage chamber 2 is made of steel, and the internal cavity size is 33cm×15cm×5cm. The two sides of the rock sample to be tested are tightly fitted with the left permeable stone 4 and the right permeable stone 10;

[0084] The thickness of the left permeable stone 4 and the right permeable stone 10 is 1.5 cm;

[0085] The perforated partition plate 1 can move vertically according to the deformation of the rock sample being measured.

[0086] The steps for using the mudstone lateral expansion force tester are as follows:

[0087] (1) Inspect all parts of the instrument and ensure the cleanliness of the entire instrument. Assemble the device, debug the computer-related software and the micrometer and return them to zero. Cut the mudstone to be tested into test blocks of 30 cm × 15 cm × 5 cm. Load the test blocks into the instrument from the right end of storage chamber 2. Then install the permeable stones on both sides and the corresponding mechanical sensors as required, and carry out subsequent measurements.

[0088] (2) Turn on the humidistat and adjust it to the humidity required for measurement. At the same time, turn on the computer and collect the data of the mechanical sensor. Water enters the interior through the small holes on the perforated partition 1, gradually humidifying the mudstone. The mudstone absorbs water and expands. The data collected by the mechanical sensors on both sides are collected and the data collected at each time period are transmitted to the computer 12. When the expansion force does not change significantly, the lateral expansion force of the mudstone under a certain humidity can be obtained. At this time, the micrometer 16 is read to obtain the vertical deformation displacement of the mudstone.

[0089] The mudstone roadbed includes mudstone and its overlying surface layer. The lateral expansion force of the mudstone measured by the present invention is used to calculate the deformation of the mudstone roadbed, including the vertical elastic extrusion deformation of the mudstone and the bending deformation of the central soil of the mudstone. When the measured mudstone can be observed with obvious bedding, the calculated thickness is calculated according to the thickness of each bedding. When the measured mudstone cannot be observed with obvious bedding, the calculated thickness of the mudstone deformation is 1 / 10 of the roadbed width. Taking the measured mudstone with obvious bedding as an example, since the mudstone absorbs water and expands, the calculated thickness should be calculated based on the thickness after wetting deformation. When calculating by layers, the thickness of each layer is s. i =d i +d i ε c , where s i is the thickness of each layer divided after wetting deformation, d i is the thickness of each layer before wetting deformation, i is the number of layers, from top to bottom: 1, 2, ..., i-1, i, ε c is the deformation strain of mudstone due to wetting, c is the displacement of mudstone due to wetting deformation, and δ is the thickness of mudstone before wetting deformation;

[0090] The specific calculation steps are as follows:

[0091] S1. The lateral expansion stress of mudstone is measured using a mudstone lateral expansion force tester;

[0092] S2, calculate the vertical elastic extrusion deformation of mudstone based on the lateral expansion force of mudstone;

[0093] S21. Calculate the strain ε of the measured mudstone layer i under lateral load and overburden load i for:

[0094]

[0095] σ yi =γ 1 h+γ 2 z i =ρ 1 gh+ρ 2 gz i

[0096] Where E is the elastic modulus of mudstone, σ yi is the vertical stress of the i-th layer of bedding, υ is Poisson's ratio, p is the lateral expansion stress of mudstone, γ 1 is the weight of the overlying surface layer, γ 2 is the weight of mudstone, h is the thickness of the overlying layer, z i The depth of the i-th bedding layer from the top of the mudstone embankment, ρ 1 is the density of the overlying surface, ρ 2 is the density of mudstone, g is the acceleration due to gravity;

[0097] S22. Calculate the vertical displacement of the bedding:

[0098] y i =ε i s i

[0099]

[0100] In the formula, y i is the vertical displacement of the i-th layer of bedding, α is the moisture expansion coefficient, and Δω is the change in the moisture content of mudstone;

[0101] S23. Calculate the vertical elastic extrusion deformation y of mudstone as:

[0102]

[0103] Where n represents the total number of layers.

[0104] S3. Calculate the bending deformation of the soil in the center of the mudstone based on the lateral expansion force of the mudstone.

[0105] S31. Calculate the mudstone stiffness D as:

[0106]

[0107] In the formula, is the rock deflection coefficient, I is the moment of inertia of the section;

[0108] S32. Calculate the bending deformation f(x) of the mudstone center soil as:

[0109] f(x)=f 1 (x)+f 2 (x)

[0110] f 1 (x) represents the deflection deformation of mudstone under lateral compression, f 2 (x) represents the deflection deformation of the mudstone overlying layer under load, and x represents the position of the lateral coordinate of the mudstone roadbed.

[0111] (1) Calculate the deflection deformation of mudstone under lateral pressure, specifically:

[0112] Taking the width of mudstone roadbed L as unit 1, the lateral compressive stress σ of the soil in the center of the i-th layer is i for:

[0113]

[0114] In the formula, K 1 is the static lateral pressure coefficient of the overlying layer, K 2 is the static lateral pressure coefficient of mudstone;

[0115] When the soil at the center of the bedding is under pressure at both ends, the bending deformation can be approximately regarded as a slender rod with hinged constraints at both ends, and the deflection relationship can be expressed as:

[0116] f 1 "(x)+k i 2 f 1 (x) = 0

[0117]

[0118] In the formula, k i F i The square root of the ratio to D is an intermediate parameter with no practical significance; i is the horizontal external force acting on the soil at the center of the i-th layer; when the mudstone width is taken as unit 1, F i The value of is equal to σ x s i , EI is the bending stiffness of the soil layer;

[0119] When x = 0 or x = L, the two ends of the mudstone are constrained and its deflection deformation is 0. The deflection relationship is analyzed and calculated as follows:

[0120]

[0121] Among them, A i To simplify the parameter values,

[0122] (2) Calculate the deflection deformation of mudstone under overburden load, specifically:

[0123] If the thickness of each layer is the same, the size of the upwarp deformation of each layer is equal, the layers are in contact with each other and there is no compression, that is, the horizontal external force F on each layer is equal, and the simplified parameter value A of each layer is i =A. When the upper surface layer reduces the deformation of the lower part, the layers interact with each other and produce the same deformation. At this time, the deflection deformation of the soil at the center of each layer is the same, and the load reduction value of the upper surface layer is q mEvenly distributed in each layer, then:

[0124]

[0125] Where q is the self-weight stress of the bedding, m 层 is the bedding quality, q t is the average reduction value of the overlying surface load, m is the mass of the overlying surface layer, and L is the width of the mudstone roadbed;

[0126] The deflection deformation of the mudstone center soil at this time is expressed as:

[0127]

[0128] If the thickness of each layer is different, the layers are squeezed against each other, and the overburden load is the overburden surface load and the overburden layer load, then the overburden load q on the i-th layer is i for:

[0129]

[0130] When i=1, the deflection deformation of the first layer of bedding under the overlying load is:

[0131]

[0132] The deflection deformation of the mudstone center is:

[0133]

[0134] When i>1, the deflection deformation of mudstone under the overburden load of the i-th layer is preliminarily calculated as:

[0135]

[0136] The preliminary calculation of the soil deflection deformation at the center of the i-th layer is:

[0137]

[0138] Determine whether the first layer and the second layer squeeze each other:

[0139] If f 1 (x)≥f 2 (x), the first layer does not compress against the second layer, that is, the deflection deformation of the first layer under the overburden load is the deflection deformation of the final mudstone under the overburden load, which is f 21 (x), the final deflection deformation of the mudstone center is f 1 (x);

[0140] If f 1 (x) <f2 (x), the first layer and the second layer are squeezed against each other, and the deformation reduction effect of the overlying surface layer load is redistributed according to the bedding thickness of each layer. Since the elastic modulus of each layer is equal to the longitudinal length, the distribution ratio of the first layer and the second layer can be expressed as:

[0141]

[0142] In the formula, q m1 The overburden load reduction value assigned to the first layer of bedding, q m2 The overburden load reduction value assigned to the second layer of bedding, At this time, the deflection deformation of the first two layers under the overlying load is equal. After redistribution, the deflection deformation of the first two layers under the overlying load is f 22 (x) is:

[0143]

[0144] At this time, the deflection deformation of the first two layers of soil is equal, and the deflection deformation of the second layer of soil is f m2 (x) is:

[0145]

[0146] Determine whether the second layer is squeezed by the third layer:

[0147] If f m2 (x)≥f 3 (x), the second layer does not squeeze the third layer, and the final deflection deformation of the mudstone under the overlying load is f 22 (x), the final deflection deformation of the mudstone center is f m2 (x);

[0148] If f m2 (x) <f 3 (x), the second and third layers are mutually squeezed, and the load reduction value of the overlying layer needs to be redistributed among the first three layers. The deformation values ​​of the first three layers under the overlying load are calculated to determine whether there is squeezing with the fourth layer. The distribution relationship of each layer is:

[0149]

[0150] At this time, the load reduction values ​​of the upper surface layers of each layer are:

[0151]

[0152] At this time, the deflection deformation of the first three layers under the overlying load is equal. After redistribution, the deflection deformation of the first three layers under the overlying load is:

[0153]

[0154] At this time, the deflection deformation of the central soil of the first three layers is equal, and the deflection deformation of the central soil of the third layer is:

[0155]

[0156] Determine whether the third layer is squeezed by the fourth layer:

[0157] If f m3 (x)≥f 4 (x), the third layer does not squeeze the fourth layer, and the final deflection deformation of the mudstone under the overlying load is f 23 (x), the final deflection deformation of the mudstone center is f m3 (x).

[0158] By analogy, to determine whether the i-1th layer and the ith layer are squeezed against each other, 1<i≤n, n is the total number of bedding layers, which is:

[0159] The deflection deformation of the i-th layer of bedding under the overburden load is preliminarily calculated as:

[0160]

[0161] The preliminary calculation of the soil deflection deformation at the center of the i-th layer is:

[0162]

[0163] If f i-1 (x)≥f i (x), then the i-1th layer does not compress with the i-th layer, and the deflection deformation of the i-1th layer under the overlying load is f 2(i-1) (x), which is consistent with the deflection deformation under the final mudstone overburden load. The final deflection deformation of the soil in the center of the mudstone is f i-1 (x);

[0164] If f i-1 (x) <f i (x), the i-1th layer and the i-th layer squeeze each other, and the load reduction value of the upper surface layer is redistributed among the first i layers. The distribution relationship of each layer is:

[0165]

[0166] At this time, the deflection deformation under the overlying load of the first i layers is equal. After redistribution, the deflection deformation under the overlying load of the i-th layer is:

[0167]

[0168] The deflection and deformation of the soil in the center of the first i layers are equal. After redistribution, the deflection and deformation of the soil in the center of the i-th layer is:

[0169]

[0170] Determine whether the i-th layer is squeezed by the i+1-th layer:

[0171] If f mi (x)≥f i+1 (x), then the i-th layer does not compress with the i+1-th layer, and the final deflection deformation of the overlying mudstone layer under load is f 2i (x), the final deflection deformation of the mudstone center is f mi (x);

[0172] When i = n, the final deflection deformation of the mudstone center is f mn (x).

[0173] Test Example 1

[0174] This test case uses the mudstone roadbed section of the Hebai Expressway as a sample. The roadbed of this section deforms under the action of rainwater. The measurement shows that the roadbed width of this section is 24m, the thickness of the overlying surface layer is 0.5m, and its structure is as follows: Figure 3 As shown, the wetting depth Z is Figure 4 shown.

[0175] Cylindrical samples with a diameter of 100 mm and a height of 200 mm were taken from the mudstone roadbed. The elastic modulus E, Poisson's ratio υ and initial water content ω of the samples were tested. 0 , and then take the mudstone sample wetted by water infiltration on site to test the water content after wetting ω 1 , calculate the change in moisture content, sample the overlying surface material to test its density, and observe the rainwater infiltration depth H 1 And record, the mudstone roadbed detection parameters and the density of the overlying surface layer material are shown in Table 1:

[0176] Table 1 Mudstone roadbed parameters and overlying surface material density

[0177]

[0178] According to the mudstone lateral expansion force tester provided by the present invention, the lateral expansion force p of the mudstone sample is measured to be 6.3Mpa when the wetted water content is 27%. The mudstone roadbed has 5 layers of bedding, with a total thickness of 0.63m. The thickness of each layer is 0.15m, 0.10m, 0.13m, 0.10m, and 0.15m respectively. The deformation of the mudstone roadbed is calculated according to the following steps:

[0179] (1) Calculate the vertical elastic compression deformation of mudstone. Substitute the bedding thickness into the calculation formula of the vertical elastic compression deformation of mudstone to calculate the vertical displacement of each layer of mudstone, as shown in Table 2:

[0180] Table 2 Vertical deformation of mudstone layers

[0181] Number of layers Vertical displacement(cm) 1 0.17 2 0.12 3 0.15 4 0.11 5 0.17

[0182] The vertical elastic compression deformation of mudstone is:

[0183]

[0184] The actual vertical displacement of the mudstone sample after wetting and deformation is measured, as shown in Table 3:

[0185] Table 3 Changes in thickness of each layer before and after wetting

[0186] Number of layers Thickness before humidification (cm) Thickness after wetting (cm) Actual vertical displacement (cm) 1 15.0 16.8 0.18 2 10.0 11.2 0.12 3 13.0 14.6 0.16 4 10.0 11.2 0.12 5 15.0 16.8 0.18

[0187] It can be seen that the actual wetting deformation thickness of the mudstone sample is 0.76 cm. The calculation method for the vertical elastic extrusion deformation of mudstone proposed in this application has an error of 5.3% compared with the actual measurement, which has high accuracy.

[0188] (2) Calculate the layered bending deformation of the central mudstone soil. Select the road center point x = 12m and calculate the deflection values ​​of the 1st, 2nd, 3rd, 4th and 5th layers, as shown in Table 4:

[0189] Table 4 Deflection value of each layer (cm)

[0190] <![CDATA[f 1 (x)]]> <![CDATA[f 2 (x)]]> <![CDATA[f 3 (x)]]> <![CDATA[f 4 (x)]]> <![CDATA[f 5 (x)]]> 3.90 4.84 4.35 4.84 4.17

[0191] Because f 1 (x) <f 2 (x), so it is determined that the first layer is in contact with and squeezed by the second layer, and the load reduction value of the upper surface layer is redistributed, that is:

[0192]

[0193] The load reduction value q of the upper surface layer is calculated m =10kN, then

[0194]

[0195] Recalculate the bending deformation of the soil at the center of the first two layers f m2 (x), we get:

[0196]

[0197] After judgment, f m2 (x)>f 3(x), so there is no relative compression between the first two layers and the third layer. The load reduction effect of the overlying surface layer only acts on the first and second layers. The deformation values ​​of the two layers are equal. Finally, the deflection deformation of the mudstone center soil is f m2 (x).

[0198] According to f m2 (x) Calculate the deflection value of the mudstone center soil under different x, and measure the actual deformation value. The results are shown in Figure 5:

[0199] Table 5 Calculated deformation value and actual deformation value

[0200] x(m) Calculated deformation value (cm) Actual deformation value (cm) Calculated and actual relative error 0.5 0.32 0.36 11.1％ 1.0 0.63 0.58 8.6％ 1.5 0.94 0.93 1.1％ 2.0 1.24 1.33 6.8％ 2.5 1.53 1.50 2.0％ 3.0 1.81 1.68 7.7％ 3.5 2.09 1.94 7.7％ 4.0 2.35 2.18 7.8％ 4.5 2.61 2.45 6.5％ 5.0 2.85 2.60 9.6％ 5.5 3.08 2.91 5.8％ 6.0 3.29 3.12 5.4％ 6.5 3.49 3.35 4.2％ 7.0 3.68 3.54 4.0％ 7.5 3.85 3.66 5.2％ 8.0 4.00 3.80 5.3％ 8.5 4.14 3.91 5.9％ 9.0 4.26 4.05 5.2％ 9.5 4.36 4.20 3.8％ 10.0 4.45 4.33 2.8％ 10.5 4.51 4.48 0.7％ 11.0 4.56 4.61 1.1％ 11.5 4.59 4.68 1.9％ 12.0 4.61 4.73 2.5％

[0201] Comparing the calculation results, the relative error between the calculation results and the actual measurement is controlled within 15%, which meets the calculation requirements of mudstone roadbed deformation within the allowable error range, indicating that the calculation method has a high prediction accuracy and can accurately calculate the uneven deformation of mudstone.

[0202] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0203] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A mudstone lateral expansion force tester, comprising an L-shaped fixed base (5), It is characterized in that The L-shaped fixed base (5) has a square groove (14) in it, a storage chamber (2) is arranged in the square groove (14), the storage chamber (2) is hollow inside, openings are arranged at the left and right ends of the storage chamber (2) and the middle of the top plate is opened, the mudstone to be tested is arranged inside the storage chamber (2), a left permeable stone (4) is arranged at the opening at the left end of the storage chamber (2), and a right permeable stone (10) is arranged at the opening at the right end of the storage chamber (2), and the storage chamber (2) is connected to a humidistat (13) through a hose (11) arranged at an opening on one side of the top plate.

2. The mudstone lateral expansion force tester according to claim 1, It is characterized in that A perforated partition plate (1) is arranged at the upper end of the left permeable stone (4) and the right permeable stone (10); the bottom of the micrometer (16) passes through the middle opening of the top plate of the storage chamber (2) and the perforated partition plate (1) in sequence to contact the mudstone to be measured; a left mechanical sensor (3) is arranged on the outer side of the left permeable stone (4); a right mechanical sensor (6) is arranged on the outer side of the right permeable stone (10); a hole is arranged at one end of the L-shaped fixed base (5); one end of the screw rod (8) passes through the hole of the L-shaped fixed base (5) and the knob (7) contacts one of the mechanical sensors; the knob (7) drives the screw rod (8) to be screwed out and screwed in together; the other end of the screw rod (8) is fixed to the outer side of the L-shaped fixed base (5) by a nut.

3. A method for calculating the deformation of a mudstone roadbed using the mudstone lateral expansion force tester as claimed in claim 1 or 2, It is characterized in that Mudstone roadbed includes mudstone and its overlying surface layer. When significant bedding is observed in mudstone, the thickness is calculated according to the thickness of each bedding layer. Since mudstone absorbs water and expands, the thickness of the bedding layer is calculated according to the thickness after wetting and deformation. When calculating by layers, the thickness of each layer is s. i =d i +d i ε c , where s i is the thickness of each layer divided after wetting deformation, d i is the thickness of each layer before wetting deformation, i is the number of layers, from top to bottom: 1, 2, ..., i-1, i, ε c is the deformation strain of mudstone due to wetting, c is the displacement of mudstone due to wetting deformation, and δ is the thickness of mudstone before wetting deformation; After that, follow these steps to implement it: S1. The lateral expansion stress of mudstone is measured using a mudstone lateral expansion force tester; S2, calculate the vertical elastic extrusion deformation of mudstone based on the lateral expansion force of mudstone; S3. Calculate the bending deformation of the soil in the center of the mudstone based on the lateral expansion force of the mudstone.

4. The method for calculating deformation of mudstone roadbed according to claim 3, It is characterized in that In S2, calculating the vertical elastic compression deformation of mudstone includes the following steps: S21. Calculate the strain ε of the measured mudstone layer i i for: s yi =c 1 h+g 2 z i =ρ 1 gh+r 2 gz i Where E is the elastic modulus of mudstone, σ yi is the vertical stress of the i-th layer of bedding, υ is Poisson's ratio, p is the lateral expansion stress of mudstone, γ 1 is the weight of the overlying surface layer, γ 2 is the weight of mudstone, h is the thickness of the overlying layer, z i The depth of the i-th bedding layer from the top of the mudstone embankment, ρ 1 is the density of the overlying surface, ρ 2 is the density of mudstone, g is the acceleration due to gravity; S22. Calculate the vertical displacement of the bedding: y i =e i s i In the formula, y i is the vertical displacement of the i-th layer, α is the moisture expansion coefficient, Δω is the change in mudstone moisture content; s i is the thickness of the i-th bedding plane; S23. Calculate the vertical elastic extrusion deformation y of mudstone as: Where n represents the total number of layers.

5. The method for calculating mudstone roadbed deformation according to claim 3, It is characterized in that In S3, calculating the bending deformation of the central soil mass of the mudstone includes the following steps: S31. Calculate the mudstone stiffness D as: In the formula, is the deflection coefficient of mudstone, υ is Poisson’s ratio, E is the elastic modulus of mudstone, and I is the moment of inertia of the section; S32. Calculate the bending deformation f(x) of the mudstone center soil as: f(x)=f 1 (x)+f 2 (x) f 1 (x) represents the deflection deformation of mudstone under lateral compression, f 2 (x) represents the deflection deformation of the mudstone overlying layer under load, and x represents the position of the lateral coordinate of the mudstone roadbed.

6. The method for calculating bending deformation of mudstone central soil according to claim 5, It is characterized in that In S32, the deflection deformation of the mudstone under lateral pressure is calculated, specifically: Taking the width of mudstone roadbed L as unit 1, the lateral compressive stress σ of the soil in the center of the i-th layer is i for: Where p is the lateral expansion stress of mudstone, K 1 is the static lateral pressure coefficient of the overlying layer, K 2 is the static lateral pressure coefficient of mudstone, γ 1 is the weight of the overlying surface layer, γ 2 is the weight of mudstone, z i The depth of the i-th bedding layer from the top of the mudstone roadbed, h is the thickness of the overlying surface layer; When the soil at the center of the bedding is under pressure at both ends, the bending deformation can be approximately regarded as a slender rod with hinged constraints at both ends, and the deflection relationship can be expressed as: In the formula, k i F i The square root of the ratio to D is an intermediate parameter with no practical significance; F i is the horizontal external force acting on the soil at the center of the i-th layer; EI is the bending stiffness of the soil layer; When x=0 or x=L, the deflection deformation is 0, and the deflection relationship can be obtained by analytical calculation: Among them, A i To simplify the parameter values, 7. The method for calculating bending deformation of mudstone central soil according to claim 5, It is characterized in that In S32, the deflection deformation under the overlying load of the mudstone is calculated, specifically: If the thickness of each layer is the same, the size of the upwarping deformation of each layer is equal, the layers are in contact with each other and there is no compression, that is, the horizontal external force F on each layer is equal, and the simplified parameter value A of each layer is i Under the reduction effect of the upper surface layer on the lower deformation, the layers interact with each other and produce the same deformation. At this time, the deflection deformation of the soil at the center of each layer is the same, and the reduction value of the upper surface layer load is evenly distributed in each layer, then: Where q is the self-weight stress of the bedding, m 层 is the bedding quality, q t is the average reduction value of the overlying surface load, q m is the overlying surface load reduction value, m is the mass of the overlying surface layer, and L is the width of the mudstone roadbed; If the thickness of each layer is different, the layers are squeezed against each other, and the overburden load is the overburden surface load and the overburden layer load, then the overburden load q on the i-th layer is i for: In the formula, ρ 1 is the density of the overlying surface, ρ 2 is the density of mudstone, h is the thickness of the overlying surface layer, g is the gravity acceleration, and n is the total number of layers; When i=1, the deflection deformation of the first layer of bedding under the overlying load is: When 1<i≤n, the deflection deformation of the i-th layer of bedding under the overlying load is preliminarily calculated as: The preliminary calculation of the soil deflection deformation at the center of the i-th layer is: Determine whether the i-1th layer and the ith layer squeeze each other: If f i-1 (x)≥f i (x), then the i-1th layer does not compress with the ith layer, and the final deflection deformation of the overlying mudstone layer under load is f 2(i-1) (x); If f i-1 (x) <f i (x), the i-1th layer and the i-th layer squeeze each other, and the load of the upper surface layer is redistributed to the first i layers. The distribution relationship of each layer is: In the formula, q mi is the load reduction value of the upper surface layer of the i-th layer; At this time, the deflection deformation under the overlying load of the first i layers is equal. After redistribution, the deflection deformation under the overlying load of the i-th layer is: The deflection and deformation of the soil in the center of the first i layers are equal. After redistribution, the deflection and deformation of the soil in the center of the i-th layer is: Determine whether the i-th layer is squeezed by the i+1-th layer: If f mi (x)≥f i+1 (x), then the i-th layer does not compress with the i+1-th layer, and the final deflection deformation of the mudstone overlying layer under load is f 2i (x).

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