A method for measuring local stress of annular geotube bags and a method for calculating their bearing capacity

Abstract

The present invention provides a method for measuring the local stress of an annular geotextile tube bag and a method for calculating the bearing capacity, including: measuring the stress-strain relationship curve of geotextiles; dividing the surface of an unfilled annular geotextile tube bag into orthogonal grids along the annular direction and radial direction, and recording the initial lengths of each section to be measured along the annular direction and radial direction respectively; measuring the lengths of each section to be measured along the annular direction and radial direction after the geotextile bag is filled and stacked respectively; calculating the strains occurring in each section; selecting multiple sections along the annular direction and radial direction respectively to measure and obtain the local strain and calculate the total strain; calculating the bearing capacity of the geotextile bag in the current state. The present invention solves the problem that the local stress of annular geotextile tube bags is difficult to measure and the calculation method of the overall bearing capacity is lacking, improves the measurement accuracy of the local stress of annular geotextile tube bags, expands the measurement range, and realizes the real-time monitoring of the stress state of key parts of the annular geotextile tube bags in the service state and the accurate calculation of the overall bearing capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of geosynthetics, and in particular relates to a method for measuring local stress of an annular geotube bag and a method for calculating the pressure bearing capacity. Background Art

[0002] Geobags are widely used in civil engineering and environmental engineering due to their high overall strength, flexibility, adaptability, ease of construction, environmental friendliness and economy. Their main applications include flood control and disaster relief, slope protection, foundation reinforcement, filling engineering, retaining wall construction, environmental restoration, etc. Annular geobags are a new form of geobags. The annular geobag yard structure is a new and efficient dredging technology. The structure consists of several layers of annular geobags and silt stacked in the ring. Compared with the strip geobag structure, the stacking structure can not only rely on the friction between the geobag layers, but also give full play to the tension of the geobag itself to maintain structural stability. In practical applications, the annular geobag yard may cause the overall instability of the structure due to the tension failure of a single geobag in the structure, which leads to great safety risks and economic losses. Therefore, it is necessary to monitor the tension of the key parts of the annular geobag in the most unfavorable state under service, evaluate the current working state and safety of the geobag in real time, and predict the damage distance of the geobag.

[0003] Although there are many existing methods for monitoring local stress and strain of geobags, their applications are extremely limited. For example, fiber Bragg grating sensor technology (FBG) can embed distributed optical fibers into geobags, monitor strain by measuring the wavelength change of the optical fiber, and thus calculate tension. Although this method has high sensitivity, it is costly, delicate and complex to operate, and is not easy to promote and use on a large scale. Another example is the strain gauge method, which is to paste strain gauges on key parts of geobags, measure strain by the resistance change of the strain gauges, and then calculate tension based on the mechanical properties of the material. This method is relatively simple, but the reliability of the bond between the strain gauges and geotechnical materials needs to be studied. At the same time, as the shape of the geobags and external environmental factors change, the strain gauges will also have great errors due to the influence of bending moments and external stresses. The more important problem is that the measurement range of the strain gauge is 2%, which is far from the breaking tensile strain of general flexible geotechnical materials. In summary, there is currently no accurate, comprehensive, economical, simple, fast, and widely promoted local stress measurement method in the service process of annular geotubes. Summary of the invention

[0004] Based on the above problems, the present invention proposes a method for measuring the local stress of annular geotextile tube bags and a method for calculating the overall bearing capacity. The method is suitable for measuring the local stress of annular geotextile tube bags, can monitor the stress state of key parts of annular geotextile tube bags in real time, is accurate and comprehensive, economical and reasonable, and easy to operate. Substituting the local tensile stress measurement results into the stress-strain formula of the annular geotextile tube bag proposed by the present invention, the overall bearing capacity of the tube bag can be further calculated; substituting the ultimate tensile strain, the ultimate bearing strength of the tube bag as a whole can be determined.

[0005] In order to achieve the above object, the present invention provides a method for measuring the local stress of an annular geotube bag, comprising the following steps:

[0006] Step S1: Based on the tensile test, respectively measure the stress-strain relationship curves of the geotextile constituting the annular geotube along the circumferential direction and the radial direction, and obtain the tensile modulus of the geotextile along the circumferential direction and the radial direction based on the stress-strain relationship curves of the geotextile;

[0007] Step S2: Dividing the surface of the unfilled annular geotube bag into orthogonal grids along the annular and radial directions to form different measuring sections, and recording the initial length of each measuring section;

[0008] Step S3: After the annular geotube bags are filled and stacked, the length of each measuring section after deformation is measured;

[0009] Step S4: calculating the strain of each measuring section based on the initial length of each measuring section of the annular geotube bag and the length after filling and stacking;

[0010] Step S5: Based on the stress-strain relationship curve and tensile modulus of the geotextile along the circumferential and radial directions measured in step S1, the strain of the measuring section is converted into stress along the measuring section direction, that is, the local tensile stress of the annular geotube.

[0011] Furthermore, in step S1, a segmented measurement method is used to measure the stress-strain relationship curve of the geotextile constituting the annular geotube bag, the geotextile strain is measured by a strain gauge in the low tensile strain segment, and the geotextile strain is measured by a marking method in the high tensile strain segment, wherein the critical value range of the low tensile strain segment and the high tensile strain segment is 1.5%-2% tensile strain.

[0012] Furthermore, in step S1, the strain of the geotextile is measured by the strain gauge in the low tensile strain section, and the strain of the geotextile is measured by the marking method in the high tensile strain section. Finally, the measurement result of the low tensile strain section is corrected based on the measurement result of the high tensile strain section. The drawing coordinates of each section after correction are expressed as:

[0013]

[0014] Among them, ε iis the strain value of the strain gauge under the i-th level of tension, ε 0 is the initial strain value of the strain gauge, l k is the length of the k-th level tension measuring section, in m, l i is the length of the measured section under the i-th level of tension, in m, l 0 is the initial length of the measuring section, in m, T i is the i-th level tension, in kN / m, B i is the width of geotextile under the i-th level of tension;

[0015] Based on the above coordinates, the stress-strain relationship curve of the geotextile is obtained by plotting and fitting.

[0016] On the other hand, the present invention provides a method for calculating the pressure bearing capacity of annular geotube bags, comprising the following steps:

[0017] Step 1: Based on the tensile test, the stress-strain relationship curves of the geotextiles constituting the annular geotube bag along the circumferential direction and the radial direction are measured respectively, and the tensile modulus and the ultimate tensile strain of the geotextiles along the circumferential direction and the radial direction are obtained based on the stress-strain relationship curves of the geotextiles;

[0018] Step 2: Divide the surface of the unfilled annular geotube bag into orthogonal grids along the annular and radial directions to form different measuring sections, and record the initial length of each section to be measured;

[0019] Step 3: After the annular geotubes are filled and stacked, the lengths of each measuring section after deformation along the annular and radial directions are measured respectively;

[0020] Step 4: Calculate the strain of each measuring section based on the initial length of each measuring section in the annular geotube along the annular direction and the radial direction and the length of each measuring section after filling and stacking;

[0021] Step 5: Select multiple local segments belonging to the same tube bag profile section along the circumferential direction and radial direction as measurement segments for measurement to obtain local strains, and perform weighted average of these local strains to represent the total strain of the entire profile section along the circumferential direction and radial direction;

[0022] Step 6: After the annular geotube is filled, substitute the three-dimensional stress-strain formula of the annular geotube or the two-dimensional stress-strain formula of the annular geotube into the total strain of the annular geotube measured in step 5 along the annular and radial directions to obtain the current bearing capacity of the geobag; substitute the annular and radial ultimate tensile strains of the annular geotube measured in step 1 to obtain the ultimate bearing strength of the geobag, compare the current bearing capacity of the geobag with its ultimate bearing strength, evaluate the safety of the current geobag, and estimate its damage distance.

[0023] Furthermore, the total strains of the entire profile section in the circumferential and radial directions in step 4 are respectively:

[0024]

[0025] Among them, ε is , ε il They represent the total strains of the tube bag along the radial direction and along the circumferential direction under the i-th level load, respectively; n represents the total number of radial measurement sections, and m represents the total number of radial measurement sections;

[0026] S ij , L iq They represent the lengths of the j-numbered radial and q-numbered measuring sections under the i-th load level, in meters.

[0027] S 0j , L 0q They represent the initial lengths of the j-numbered measuring segment along the radial direction and the q-numbered measuring segment along the circumferential direction, respectively, in meters.

[0028] Furthermore, in step 6, the additional stress provided by the tension of the annular geotube bag can be decomposed into three directions of x, y, and z, and the unit vectors along the x, y, and z coordinate axes are obtained.

[0029] Furthermore, the three-dimensional stress-strain formula of the annular geotextile tube bag derived from the three-dimensional stress state analysis of the annular geotextile tube bag in step 6 is as follows:

[0030]

[0031] Where σ is the external stress field represented by a three-dimensional second-order tensor, E s E is the radial elongation modulus of the geobag, in MPa. l is the elongation modulus of the geobag along the hoop, unit MPa, B and H represent the equivalent width and height of the hoop geobag section, unit m, x, y, z are unit vectors along the x, y, z directions of the coordinate axes, represents the tensor product of two vectors, K is the stiffness coefficient of the geobag filling material, written in the fourth-order tensor form, : represents the second-order contraction of the tensor, and ε is the strain of the filling material in the geobag.

[0032] Furthermore, in step 6, the radial cross section of the annular geotube bag is set to an ideal plane strain state, and according to its two-dimensional stress state analysis, the two-dimensional stress-strain formula of the annular geotube bag is obtained:

[0033]

[0034] where σ' is the external stress field represented by a two-dimensional second-order tensor.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The local tension of the geobag is converted into local strain, which makes the tension visual and convenient for real-time monitoring of the working status of the geobag; 2. The calculation method can reflect the influence of different factors on the bearing strength of the annular geobag, which is more accurate and comprehensive; 3. The two methods can verify each other. Substituting the overburden load of the geobag can obtain the strain of the geobag along the annular and radial directions under the bearing strength, which can be verified with the direct measurement results to reduce errors. This method is fast to operate, economical and convenient, and the calculation is accurate and comprehensive. It meets the needs of the project and solves the problem that the existing technology cannot accurately measure and calculate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 For geotextile tensile testing;

[0038] Figure 2 The stress-strain relationship curve measured by the tensile test of the present invention;

[0039] Figure 3 Schematic diagram of radial and circumferential directions of an annular geotube bag in an embodiment of the present invention;

[0040] Figure 4 It is a schematic diagram of the orthogonal grid division and marking method of the annular geotube bag in the example of the present invention;

[0041] Figure 5 This is a schematic diagram of the radial grid division position of the AA section of the annular tube bag;

[0042] Figure 6 It is a schematic diagram of the plane stress state of the AA section of the annular tube bag.

[0043] In the figure, 1. tensile testing machine fixture; 2. geotextile; 3. strain gauge; 4. strain acquisition instrument; 5. computer analysis system; 6. measuring section; 7. strain gauge along the annular direction; 8. strain gauge along the radial direction; 9. measuring section along the annular direction; 10. measuring section along the radial direction; 11. annular geotube bag; 12. annular geotube bag; 13. soil filling in the bag. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 of the present invention without making creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for measuring the local stress of an annular geotube bag, comprising the following steps:

[0047] Step S1: Based on the tensile test, respectively measure the stress-strain relationship curves of the geotextile constituting the annular geotube along the circumferential direction and the radial direction, and obtain the tensile modulus of the geotextile along the circumferential direction and the radial direction based on the stress-strain relationship curves of the geotextile;

[0048] Since the tensile stress and tensile strain of the geotextile are close to a linear relationship before the geotextile bag is broken, its stress-strain relationship curve and tensile modulus can be determined through tensile tests.

[0049] Step S2: Divide the surface of the unfilled annular geotube bag into orthogonal grids along the annular and radial directions to form different measuring sections, and record the initial length L of each measuring section 0 The measuring section is generally the line segment between two intersection points of the grid, and the initial length L of each measuring section is measured with a high-precision soft ruler. 0 .

[0050] Step S3: After the annular geotube bags are filled and stacked, the length L of each measuring section after deformation is measured. i .

[0051] Step S4: calculating the strain of each test segment based on the initial length of each test segment of the annular geotube bag and the length of each test segment after deformation after filling and stacking;

[0052] In one embodiment, the strain definition is The strain along the measuring section direction is calculated.

[0053] Where:

[0054] L i is the length of the measuring section under the i-th level load,

[0055] L 0 is the initial length of the measurement section.

[0056] In another embodiment,

[0057] First, use a paint pen to mark the measuring section 6 on the geotextile along the stretching direction. Figure 1 , record the initial length l 0 When applying the i-th level of tension T i Then, use a high-precision tape measure to measure the length l of the measuring section in this state. i , and record the tensile width B of the geotextile under this level of tension i According to the test data, the following coordinates can be used By drawing and fitting, the stress-strain curve of geotextile can be obtained.

[0058] Although this measurement method can obtain a stress-strain relationship curve in a larger range, it is insufficient in accuracy. Strain gauges can be pasted on geotextiles to obtain the strain of the low tensile strain segment. A more precise stress-strain relationship curve can be obtained by adopting a segmented measurement method. The strain of geotextiles is measured by strain gauges in the low tensile strain segment, and the strain of geotextiles is measured by a marking method in the high tensile strain segment. The critical value range of the low tensile strain segment and the high tensile strain segment is 1.5%-2% tensile strain. In this embodiment, the critical value of the low tensile strain segment and the high tensile strain segment is 2% tensile strain.

[0059] The specific operation method is: firstly, the strain gauge 3 is pasted on the unstretched geotextile 2. The adhesive is recommended to be a high elasticity and low modulus silicone glue to reduce the error. The geotextile 2 is installed on the tensile test machine fixture 1. The strain gauge 3 is connected to the strain acquisition instrument system 4. The strain value is obtained after being processed by the computer analysis system 5. Record the initial strain value ε 0 and strain ε under various levels of tension i , according to the following coordinates The stress-strain relationship curve of the low tensile strain section can also be obtained by fitting. It is worth noting that since the strain of the tube bag is indirectly transmitted to the strain gauge by the silicone grease, the strain of the strain gauge may be smaller than the strain of the tube bag. It is necessary to correct the stress result of the low tensile strain section by the strain measurement result of the high tensile strain section. The correction method is to determine the strain ε of the strain gauge under the kth level of tension. k (The kth level tension is best taken as the tension corresponding to the highest point of the linear segment in the stress-strain relationship curve measured by the strain gauge). At this time, the length of the measuring section of the measuring tube bag is l k The low tensile strain segment has the following coordinates The remaining high tensile strain segment starts from point Start drawing fitting, the drawing coordinates are In summary, the coordinates for drawing the stress-strain relationship curve of geotextiles are:

[0060]

[0061] Among them, ε i is the strain value of the strain gauge under the i-th level of tension, ε 0 is the initial strain value of the strain gauge, l k is the length of the measured section under the k-th level of tension, in m, l i is the length of the measured section under the i-th level of tension, in m, l 0 is the initial measurement section length, in m, T i is the i-th level tension, in kN / m, B i is the width of geotextile under the i-th level of tension;

[0062] Based on the above coordinate plotting, the stress-strain relationship curve of the geotextile is obtained.

[0063] Step S5: Based on the stress-strain relationship curve and tensile modulus of the geotextile along the circumferential and radial directions measured in step S1, the strain of the measuring section is converted into stress along the measuring section direction, that is, the local tensile stress of the annular geotube.

[0064] Example 2

[0065] The difference between Example 2 and Example 1 is that the pressure bearing capacity of the annular geobag is calculated based on the stress measurement method in Example 1, specifically:

[0066] Step 1: Based on the tensile test, the stress-strain relationship curve of the geotextile used for woven geobags in the circumferential direction and radial direction is measured, and the tensile modulus of the geotextile in the circumferential direction and radial direction is obtained based on the stress-strain relationship curve of the geotextile;

[0067] Step 2: Divide the grid on the unfilled annular geotube bag and record the initial lengths of each section to be measured along the annular direction and radial direction respectively;

[0068] Step 3: After the geobags are filled and stacked, measure the lengths of each measuring section after deformation along the circumferential and radial directions respectively;

[0069] Step 4: Calculate the strain of each test section based on the initial length of each test section in the circumferential and radial directions of the geobag and the length of each test section after deformation after filling and stacking;

[0070] Step 5: Select multiple local segments belonging to the same tube bag profile section in the circumferential direction and radial direction as measurement segments to measure and obtain local strains, and perform weighted average of these local strains to represent the total strain of the entire profile section in the circumferential direction and radial direction;

[0071] Step 6: After the annular geotube is filled, substitute the three-dimensional stress-strain formula of the annular geotube or the two-dimensional stress-strain formula of the annular geotube into the total strain of the annular geotube measured in step 5 along the annular and radial directions to obtain the current bearing capacity of the geobag; substitute the annular and radial ultimate tensile strains of the annular geotube measured in step 1 to obtain the ultimate bearing strength of the geobag, compare the current bearing capacity of the geobag with its ultimate bearing strength, evaluate the safety of the current geobag, and estimate its damage distance.

[0072] Furthermore, in step 6, the additional stress provided by the tension of the annular geotube bag can be decomposed into three directions of x, y, and z, and the unit vectors along the x, y, and z coordinate axes are obtained.

[0073] like Figure 3 Shown is a schematic diagram of the radial and circumferential directions of the geotextile annular tube bag; Figure 4, Figure 5 A specific example of the grid division of the annular geotextile tube 11 is given in detail. The grids are divided along the annular measurement section 9 and the radial measurement section 10 respectively to determine the measurement section L. iq , S ij (i=1…n), the initial length of the measuring segment. Where L iq , S ij They represent the lengths of the measuring sections numbered q along the circumferential direction and j along the radial direction under the i-th level of load. Their positions are detailed in Figure 4 , Figure 5 Indicated in the middle.

[0074] Select multiple measurement sections for measurement, for example Figure 5 The A, B, C, and D measurement segments are local segments of the same tube bag profile section. At this time, these local strains are weighted averaged to represent the overall strain of the profile section. Generally, the initial length of the measurement segment is the same, so the formula can be written as:

[0075]

[0076] Among them, ε is , ε il They represent the total strains of the tube bag along the radial direction and along the circumferential direction under the i-th level load, respectively; n represents the total number of radial measurement sections, and m represents the total number of radial measurement sections;

[0077] S ij , L iq They represent the lengths of the j-numbered radial and q-numbered measuring sections under the i-th load level, in meters.

[0078] S 0j , L 0q They represent the initial lengths of the j-numbered measuring segment along the radial direction and the q-numbered measuring segment along the circumferential direction, respectively, in meters.

[0079] When the load strength is low and the annular geotube bag 11 does not have a large shape change, it can also be used according to Figure 4 , 5 The method for posting strain gauges is as shown in the circumferential strain gauge 7 and the radial strain gauge 8. The strain gauges are posted to measure the local strain of the tube bag, and the average value is taken to obtain the radial and circumferential strains of the tube bag. After the annular tube bag is filled, the three-dimensional stress state of the annular geotextile tube bag in step 6 is detailed in Figure 6 , the three-dimensional stress-strain formula of the annular geotube bag derived by analysis is as follows:

[0080]

[0081] Where σ is the external stress field expressed as a second-order tensor, E s E is the radial elongation modulus of the geobag, in MPa.l is the elongation modulus of the geobag along the hoop, unit MPa, B and H represent the equivalent width and height of the hoop geobag section, unit m, x, y, z are unit vectors along the coordinate axis xyz direction, represents the tensor product of two vectors, K is the stiffness coefficient of the geobag filling material, written in the fourth-order tensor form, : represents the second-order contraction of the tensor, and ε is the strain of the filling material 13 in the geobag.

[0082] The radial section of the annular geotube is set to an ideal plane strain state. According to the two-dimensional stress state analysis, the two-dimensional stress-strain formula of the annular geotube is obtained:

[0083]

[0084] where σ' is the external stress field represented by a two-dimensional second-order tensor.

[0085] Figure 6 Medium 1f , σ 3f is the component of the external stress σ.

[0086] The calculation process of the external stress field represented by the second-order tensor is as follows:

[0087] 1. Assume that the stress on the soil in the geobag 12 is the linear superposition of the external stress and the additional stress provided by the geobag tension. From this, we can get:

[0088] σ s =σ+σ b (1)

[0089] Where σ s is the stress of the sand in the bag, σ is the external stress, σ b It is the additional stress provided by the geobag tension.

[0090] 2. The geobag is attached to the outside of the soil and has a small volume. Assuming that the volume of the bag is ignored, the strain of the geobag as a whole is approximately equal to the strain of the soil itself. Write as:

[0091] ε=ε s (2)

[0092] Where ε is the strain of the geobag as a whole, ε s is the strain of the soil in the bag.

[0093] The additional stress provided by the geobag tension can be decomposed into three directions, namely along Figure 4 Coordinates in x, y, and z directions:

[0094] σ b =σ bx +σ bz +σby (3)

[0095] Take the cross section of the annular geotube bag for analysis ( Figure 6 ), the geotextile tension T distributed around the bag s Transformed into additional stress in the horizontal direction (along the x-axis direction) and vertical direction (along the z-axis direction) of the sand in the bag:

[0096] σ bx =2T s / H (4)

[0097] σ bz =2T s / B (5)

[0098] The cross section of the annular tube bag is approximately regarded as an ellipse, and the lengths of its major and minor semi-axes are B / 2 and H / 2 respectively. The geotextile tension T distributed along the circumference l It can be converted into an additional stress perpendicular to the cross section of the tube bag (along the y-axis direction) and evenly distributed:

[0099] σ by =4T l [πH+2(BH)] / BH (6)

[0100] Substituting (4)(5)(6) into (3) we can obtain:

[0101]

[0102] Due to the linear elasticity of geotextile bags, the tension can be obtained by the following formula:

[0103] T=Eε (8)

[0104] Where E is the elongation modulus of the tube bag, and ε is the strain of the tube bag.

[0105] Substituting the tension force formula (8) into the above formula (7), we can obtain:

[0106]

[0107] The total stress level of the soil can be calculated according to the method of elastic-plastic mechanics:

[0108] σ s =Kε s (10)

[0109] Where K is the stiffness coefficient of the soil, ε s is the strain of the soil.

[0110] It can be seen from the assumption in the above equation (2) that the soil strain and the overall strain of the tube bag are equal. Combining the above (1)(2)(9)(10) can establish the equation. In the soil, the stiffness coefficient is usually in the form of a fourth-order tensor. After combining the above equations, it is necessary to balance the tensor orders on both sides of the equation, and we can get:

[0111]

[0112] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0113] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0114] Other parts not described in detail are all prior art.

Claims

1. A method for measuring local stress of an annular geotube bag, characterized in that: The following steps are involved: Step S1: Based on the tensile test, respectively measure the stress-strain relationship curves of the geotextile constituting the annular geotube along the circumferential direction and the radial direction, and obtain the tensile modulus of the geotextile along the circumferential direction and the radial direction based on the stress-strain relationship curves of the geotextile; In step S1, the stress-strain relationship curve of the geotextile constituting the annular geotube bag is measured by a segmented measurement method, the strain of the geotextile is measured by a strain gauge in the low tensile strain section, and the strain of the geotextile is measured by a marking method in the high tensile strain section, wherein the critical value range of the low tensile strain section and the high tensile strain section is 1.5%-2% tensile strain; in step S1, the strain of the geotextile is measured by a strain gauge in the low tensile strain section, and the strain of the geotextile is measured by a marking method in the high tensile strain section, and finally the measurement result of the low tensile strain section is corrected based on the measurement result of the high tensile strain section, and the drawing coordinates of each section after correction are expressed as: Among them, ε i is the strain value of the strain gauge under the action of the i-th level tension, ε0 is the initial strain value of the strain gauge, l k is the length of the k-th level tension measuring section, in m, l i is the length of the measuring section under the i-th level of tension, in m, l0 is the initial length of the measuring section, in m, T i is the i-th level tension, in kN / m, B i is the width of geotextile under the i-th level of tension; Based on the above coordinates, a stress-strain relationship curve of the geotextile is obtained by drawing and fitting; Step S2: Dividing the surface of the unfilled annular geotube bag into orthogonal grids along the annular and radial directions to form different measuring sections, and recording the initial length of each measuring section; Step S3: After the annular geotube bags are filled and stacked, the length of each measuring section after deformation is measured; Step S4: calculating the strain of each measuring section based on the initial length of each measuring section of the annular geotube bag and the length after filling and stacking; Step S5: Based on the stress-strain relationship curve and tensile modulus of the geotextile along the circumferential and radial directions measured in step S1, the strain of the measuring section is converted into stress along the measuring section direction, that is, the local tensile stress of the annular geotube.

2. A method for calculating the overall pressure bearing capacity of an annular geotube bag, characterized in that: The steps include: Step 1: Based on the tensile test, the stress-strain relationship curves of the geotextiles constituting the annular geotube bag along the circumferential direction and the radial direction are measured respectively, and the tensile modulus and the ultimate tensile strain of the geotextiles along the circumferential direction and the radial direction are obtained based on the stress-strain relationship curves of the geotextiles; Step 2: Divide the surface of the unfilled annular geotube bag into orthogonal grids along the annular and radial directions to form different measuring sections, and record the initial length of each section to be measured; Step 3: After the annular geotubes are filled and stacked, the lengths of each measuring section after deformation along the annular and radial directions are measured respectively; Step 4: Calculate the strain of each measuring section based on the initial length of each measuring section in the annular geotube along the annular direction and the radial direction and the length of each measuring section after filling and stacking; Step 5: Select multiple local segments belonging to the same tube bag profile section along the circumferential direction and radial direction as measurement segments for measurement to obtain local strains, and perform weighted average of these local strains to represent the total strain of the entire profile section along the circumferential direction and radial direction; Step 6: After the annular geotextile tube is filled, the three-dimensional stress-strain formula of the annular geotextile tube is substituted into the total strain of the annular geotextile tube in the current circumferential and radial directions measured in step 5 to obtain the current pressure-bearing capacity of the geotextile tube; the ultimate tensile strain of the annular geotextile tube in the circumferential and radial directions measured in step 1 is substituted into the ultimate pressure-bearing strength of the geotextile tube, and the current pressure-bearing capacity of the geotextile tube is compared with its ultimate pressure-bearing strength to evaluate the safety of the current geotextile bag and estimate its damage distance; In step 6, the additional stress provided by the tension of the annular geotube bag can be decomposed into three directions: x, y, and z, and the unit vectors along the x, y, and z coordinate axes are obtained; The three-dimensional stress-strain formula of the annular geotube bag derived from the three-dimensional stress state analysis of the annular geotube bag in step 6 is as follows: Where σ is the external stress field represented by a three-dimensional second-order tensor, E s E is the radial elongation modulus of the geobag, in MPa. l is the elongation modulus of the geobag along the hoop, unit MPa, B and H represent the equivalent width and height of the hoop geobag section, unit m, x, y, z are unit vectors along the x, y, z directions of the coordinate axes, represents the tensor product of two vectors, K is the stiffness coefficient of the soil filling in the geobag, written in the form of a fourth-order tensor, representing the second-order contraction of the tensor, and ε is the strain of the soil filling in the geobag; is , ε il They represent the total strain of the tube bag along the radial direction and the circumferential direction under the i-th level load respectively.

3. A method for calculating the pressure bearing capacity of annular geotube bags according to claim 2, characterized in that: The total strains of the entire profile section in the circumferential and radial directions in step 5 are: Among them, ε is , ε il They represent the total strain of the tube bag in radial direction and in circumferential direction under the i-th level load, respectively; n represents the total number of radial measurement sections, and m represents the total number of radial measurement sections; S ij , L iq They represent the lengths of the j-numbered radial and q-numbered measuring sections under the i-th load level, in meters. S 0j , L 0q They represent the initial lengths of the j-numbered measuring segment along the radial direction and the q-numbered measuring segment along the circumferential direction, respectively, in meters.

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