CN117071651A - Aeolian sand-loess mixture blending ratio design method based on steel-soil interface shear test - Google Patents
Aeolian sand-loess mixture blending ratio design method based on steel-soil interface shear test Download PDFInfo
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- E—FIXED CONSTRUCTIONS
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- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- E—FIXED CONSTRUCTIONS
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- E02D1/00—Investigation of foundation soil in situ
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Abstract
The application belongs to the technical field of engineering, and particularly relates to a method for designing the mixing ratio of aeolian sand-loess mixture based on a steel-soil interface shear test. By combining the study of the blending proportion of the aeolian sand-loess mixture on the physical and mechanical properties of the aeolian sand-loess mixture, and taking the large deformation shear mechanical characteristics between the aeolian sand-loess mixture and a steel interface as study key points, the residual shear strength and deformation rules of the aeolian sand-loess mixture and the steel interface are summarized, and based on the rules, the method can be used for better determining the blending sand rate threshold value in the foundation, so that the treatment difficulty of the pure aeolian sand foundation is greatly reduced. And the method provides powerful data support for foundation treatment and pile foundation construction of the region where the north part of loess plateau meets the desert. In the subsequent foundation treatment and pile foundation investigation design construction process, proper loess can be doped into the aeolian sand, and proper sand doping rate is selected, so that the bad physical and mechanical characteristics of the aeolian sand are reduced.
Description
Technical Field
The application belongs to the technical field of engineering, and particularly relates to a method for designing a mixing ratio of aeolian sand-loess mixture based on a steel-soil interface shear test.
Background
Loess plateau is the most representative loess distribution area, but loess plateau north edge is bordered with many deserts, has formed extensive aeolian sand-loess distribution area. The zone is distributed with typical land features such as sand hill sand land, sand hill grass beach, sand hill loess beam, etc., and shallower stratum mainly has the firstFour-system brand new system aeolian sand (Q) 4 eol ) And fourth on-line update of the Coomassie loess (Q) 3 eol )。
As is well known, loess has a certain collapsibility and often brings potential hidden danger to engineering, but loess has good construction mechanical properties in the construction engineering, and is easy to compact so as to form a good artificial foundation. The physical and mechanical characteristics of the aeolian sand are greatly different from those of loess, and the aeolian sand has the characteristics of fine particles, no viscosity, low water content, poor water retention and the like, so that the compactibility of the aeolian sand is always a difficult problem in construction, and an automobile or a compacting device is often sunk into an aeolian sand foundation, which is closely related to serious shortage of the binding force of the aeolian sand. Under the action of the resultant force of the vertical force and the horizontal force of the travelling crane for a long time, the aeolian sand is extruded out laterally, and the pavement surface layer is sunken and cracked to be destroyed, so that the compaction technology of the aeolian sand becomes the key point of success and failure of the land construction engineering of the area. Researchers combine mechanical optimization configuration through field test, and adopt dry compaction technology, the representative value of the wind-packed sand compaction degree reaches 96%, but in practice, the dry compaction method can not compact in the range of 10cm floating dry sand, which is related to factors such as windy climate and dry environment in the desert, so that the surface layer of the wind-packed sand is difficult to saturate water, and the like, which brings great difficulty to wind-packed sand foundation construction.
By researching the contact mechanical property of aeolian sand-loess transitional molding loess and a rigid interface, more quantitative and accurate data guidance can be provided for reasonably treating the aeolian sand foundation.
Disclosure of Invention
The application aims at: aiming at the technical defects that the aeolian sand is difficult to utilize in the mixed distribution area of aeolian sand-loess in the prior art and the quality of the foundation in the area is poor, the design method for the aeolian sand-loess mixture blending ratio is provided, the blending ratio of the aeolian sand is scientifically and reasonably determined, aeolian sand resources are better utilized to improve the foundation, and the construction quality of engineering and building is improved.
In order to achieve the above purpose, the technical scheme adopted by the application is as follows:
a design method of an aeolian sand-loess mixture blending ratio comprises the following steps:
step 1, examining a target construction foundation, and making a mechanical research test scheme of a steel soil interface;
step 2, taking the residual shear strength as an investigation index, and carrying out an influence rule test of sand doping rate and vertical pressure on the residual shear strength of the aeolian sand-loess mixture and steel interface respectively;
and step 3, determining the optimal blending ratio of the aeolian sand-loess mixture meeting the investigation index according to the experimental result of the step 2.
The inventor finds that loess is mixed in certain proportion into aeolian sand to form aeolian sand-loess mixture, and the poor engineering characteristics of loose and non-sticky aeolian sand are treated by using excellent bonding and compaction characteristics of loess, so that the aim of treating soil with 'soil' is fulfilled. The more problems of the construction site are prominent in the contact mechanical characteristics of the soil and steel interface, and the interface mechanical behaviors are generated between the steel piles such as the ground movement of crawler-type machinery, the running of a road roller, the contact resistance between the steel piles and the surrounding soil of the piles, the construction of a sinking pipe compaction pile and the like, so that the large deformation mechanical characteristics of the soil-steel interface can be better realized by means of a ring shear test. In order to better utilize the aeolian sand resources to improve the foundation and improve the construction quality of engineering construction, the application adopts the technical scheme that the research on the physical and mechanical characteristics of the aeolian sand-loess mixture is combined, the large deformation shearing mechanical characteristics between the aeolian sand-loess mixture and a steel interface are taken as research emphasis, the residual shearing strength and deformation rules of the aeolian sand-loess mixture and the steel interface, namely the sand doping rate, the vertical pressure and the shearing rate, are summarized, and based on the rules, the method can be used for better determining the mixed sand doping rate threshold value in the foundation, so that the treatment difficulty of the pure aeolian sand foundation is greatly reduced. The construction of foundation treatment of the building and pile in the area provides powerful data support. The aeolian sand-loess mixture can be selected, and the proper sand doping rate is selected, so that the bad physical and mechanical characteristics of aeolian sand are reduced.
In the step 1, soil samples including a target construction area are collected for foundation investigation, and the maximum dry density and the optimal water content of the mixture are obtained.
The aeolian sand-loess mixture under different sand blending rate conditions has different physical and mechanical properties, and the mixture can have different changes along with the increase of the sand blending rate, such as physical characteristics of dry density, hydraulic limit and the like, and mechanical properties of strength, compression and the like, so that the aeolian sand-loess bordering area is necessary to be studied deeply, and a certain technical support is provided for engineering construction of the aeolian sand-loess bordering area. For large area construction projects, it is critical to obtain maximum dry density and optimum water content of the mix, which are important parameter bases for controlling the mix compaction. The aeolian sand-loess mixed material foundation is also often contacted with other engineering equipment (steel interfaces and rubber interfaces) in the construction process, and the mixed material foundation is contacted with other structures (such as a concrete foundation, a pile foundation and anchor rods) in the use process, and the two contacts belong to interfacial mechanical behaviors, so that the application is used for researching the interfacial mechanical behaviors by selecting a ring shear test as a preferable scheme of the application.
Further preferably, the maximum dry density and the optimal water content are obtained according to the following test:
collecting test soil materials in a target construction area, and respectively preparing aeolian sand-loess mixed soil materials with the same water content and different sand contents according to a mode of firstly dry mixing and then humidifying; the aeolian sand-loess mixed soil material comprises samples with sand content of 0%, 20%, 40%, 60%, 80% and 100%, wherein 0% refers to a pure loess sample and 100% refers to a pure aeolian sand sample; specifically, all the soil materials are dried and then screened by a 1mm sieve, the quality of the dry loess and the dry wind sand required by each sample is calculated respectively, and then the water content is increased in the prepared mixture according to the definition of the water content, so that the corresponding sample is obtained.
The sand mixing rate is represented by Rs, and the mass ratio of the dry wind sand to the sum of the dry wind sand and the dry loess is used;
Rs＝m sand and sand /(m Sand and sand +m Soil )；①
Wherein: m is m Sand and sand Representing the mass of the dry aeolian sand in units of: g; m is m Soil Representing the mass of dry loess in units of: g; both water contents were 0%.
The water content of the aeolian sand-loess mixture refers to the ratio of the sum of the mass of water in the aeolian sand and loess to the sum of the dry aeolian sand and the dry loess:
w＝m w /(m sand and sand +m Soil )；②
Wherein: m is m w Represents the sum of the mass of the aeolian sand and the water in loess, and the unit: g.
carrying out static compaction on a sample with sand doping rate of more than 80 percent (including 80 percent) to obtain maximum dry density;
and (3) compacting the sample with the sand doping rate lower than 80% to obtain the maximum dry density.
The dry density is maximum when the water content is 10% through the test; thus, the water content was set to 10% and the compactibility was set to 0.93 during the test.
As a preferable technical scheme of the application, the annular shear test comprises annular shear tests under different vertical pressure conditions, and the interval of the vertical pressure is 50-400kPa.
As a preferable technical scheme of the application, the test instrument in the ring shear test is a KTL-TTS type interface shear instrument. Compared with the traditional direct shear apparatus, the apparatus can ensure that the shearing surface is invariable and the stress is uniform all the time in the shearing process, and the base can rotate at an unlimited angle, namely the shearing angle is arbitrary.
As the preferable technical scheme of the application, after the annular shearing test is finished, observing the particle distribution characteristics and particle crushing characteristics of the mixture test pieces with different sand doping rates through a scanning electron microscope; and obtaining the sand mixing rate, the residual shear strength of the vertical pressure on the aeolian sand-loess mixture and the steel interface and the deformation rule.
As a preferable technical scheme of the application, the optimal sand blending rate of the aeolian sand-loess mixture ranges from 60% to 80%. Within this range, the residual strength between the aeolian sand-loess mixture and the steel interface remains stable. With the improvement of the mixing ratio of the aeolian sand, the bonding effect is reduced, the biting effect of aeolian sand particles and the steel plate is improved, the reduction of friction capacity caused by bonding performance is made up, and the reduction amplitude of the internal friction angle of the whole mixture interface is smaller. The sand blending rate is 60% -80%, and the construction difficulty of aeolian sand can be effectively reduced.
Further preferably, both of the above-mentioned shearing tests require control of the degree of compaction and the moisture content of the aeolian sand-loess mixture to be kept uniform.
Preferably, the compactness refers to the ratio of the dry density of the aeolian sand-loess mixture sample to the maximum dry density; it is required to obtain the maximum dry density of the aeolian sand-loess mixture under the condition of different sand blending rates.
In the technical scheme of the application, the maximum dry density and the optimal water content are tested according to the following modes:
the compaction method is suitable for aeolian sand-loess mixture samples with high sand doping rate, and the static compaction method is suitable for aeolian sand-loess mixture samples with low sand doping rate, and the critical value range of the sand doping rate is 60% -80%.
The maximum dry density and the optimal water content of the mixture under the condition of aeolian sand and soil materials and high sand doping rate cannot be obtained by a compaction method, and the sample cannot be effectively compacted. Therefore, the soil material can attempt to acquire corresponding indexes by adopting a static compaction method. The improvement of the sand doping rate has an important influence on compaction or compaction characteristics of the mixture, and the mixture is easy to generate rubber soil in the compaction process, so that the mixture cannot be effectively bonded. The minimum dry density of the aeolian sand is shown by a mixture compaction characteristic curve obtained by compacting the mixture by adopting static force under the condition that the sand doping rate is 80% or more. Studies have shown that the compaction or compaction performance of non-sticky soils is best in saturated and dry conditions. Preferably, the critical value range of the sand doping rate is 60% -80%.
In summary, due to the adoption of the technical scheme, the beneficial effects of the application are as follows:
according to the technical scheme, the design method of the system about the optimal sand doping rate is finally formed through experimental researches on different parameters and the study on aeolian sand-loess blends with different sand doping rates by using a ring shear test. Summarizing the residual shear strength and deformation rule of the sand mixing rate, the vertical pressure and the shear rate on the aeolian sand-loess mixture and steel interface, and based on the rule, the method can be used for better determining the mixed sand mixing rate threshold value in the foundation, so that the treatment difficulty of the pure aeolian sand foundation is greatly reduced. The method provides powerful data support for foundation treatment and pile foundation construction of the area. The aeolian sand-loess mixture can be selected, and the proper sand doping rate is selected, so that the bad physical and mechanical characteristics of aeolian sand are reduced.
Drawings
FIG. 1 is a graph showing the relationship between the dry density and the water content of the aeolian sand-loess mixture with different sand incorporation rates; (the sand doping rate of the figure 1 (a) is 0-60 percent, and the sand doping rate of the figure 1 (b) is 80-100 percent);
FIG. 2 is a graph showing the change of shear stress with shear displacement in the process of shearing an aeolian sand-loess mixture interface under the condition of different sand doping rates of samples No. 1-24; ((a) 1) # -4 # 、(b)5 # -8 # 、(c)9 # -12 # 、(d)13 # -16 # 、(e)17 # -20 # 、(f)21 # -24 # )；
FIG. 3 is a graph showing the change of vertical strain with shear displacement in the process of shearing an aeolian sand-loess mixture interface under the condition of different sand doping rates of samples No. 1-24; ((a) 1) # -4 # 、(b)5 # -8 # 、(c)9 # -12 # 、(d)13 # -16 # 、(e)17 # -20 # 、(f)21 # -24 # )；
FIG. 4 is a graph showing the relationship between the interfacial residual strength index and the sand doping rate (a) interfacial residual cohesion and (b) interfacial residual internal friction angle;
FIG. 5 is a view of images of the aeolian sand-loess mixture at 300 times electron microscope (a) 0%, (b) 20%, (c) 30%, (d) 60%, (e) 80%, (f) 100%;
Detailed Description
The present application will be described in detail with reference to the accompanying drawings.
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
Example 1
Aiming at the technical defects that the aeolian sand is difficult to utilize in the aeolian sand-loess mixed distribution area and the quality of the foundation in the area is poor in the prior art, the application provides the design method for the aeolian sand-loess mixture blending ratio, which is used for scientifically and reasonably determining the blending ratio of the aeolian sand, better utilizing aeolian sand resources to improve the foundation and improving the construction quality of engineering and building.
Specifically, northern part of certain city of Shaanxi province is a mao wusu sandy desert wind sand transition region, southern part is a loess plateau region, the region has a larger range of wind-deposited sand-loess interweaving zones, typical land features such as sand hill sand land, sand hill grass beach, sand hill loess beam and the like are distributed, and shallower stratum mainly has fourth-system brand new wind-deposited sand (Q 4 eol ) And fourth on-line update of the Coomassie loess (Q) 3 eol ) Aeolian sand and loess interweaving in these areas are buried and exposed.
In this region, aeolian sand and loess used for the sample were obtained from a county of Shaanxi province. Aeolian sand (Q) 4 eol ) Pale yellow, loose-slightly dense and slightly wet, and contains quartz and feldspar as main ingredients, and has uniform granule, poor grading, and C c ＝1.98，C u =1.01, soil particle relative density 2.66. Loess (Q) 3 eol ) Brown yellow, compact, slightly wet, pore developed, uniform soil quality, wind-packed loess, classification as silt, soil particle relative density of 2.72, plastic limit of 11.86%, liquid limit of 17.66%, and natural repose angle of wind-packed sand of 31.3 ° in dry state.
At present, engineering personnel are averted to the wind-blown sand, the wind-blown sand with small area can be processed by avoiding, but the avoidance of the wind-blown sand with large area tends to increase the engineering cost, so that the engineering characteristics of the wind-blown sand are very important for the safety and economy of engineering, and how to reasonably utilize the wind-blown sand and study the wind-blown sand are important.
Based on the above situation, a design method for the optimal blending ratio of the aeolian sand-loess mixture is provided, which specifically comprises the following steps:
step 1, examining a target construction foundation, and making a mechanical research test scheme of a steel soil interface; specifically, the foundation investigation comprises soil sample collection of a target construction area, and the maximum dry density and the optimal water content of the mixture are obtained.
In this example, the dry mixing and then humidification method was adopted to prepare the aeolian sand-loess mixed soil material having a water content of 10% and sand contents of 0% (loess), 20%, 40%, 60%, 80% and 100%, respectively. Wherein 0% refers to a pure loess sample and 100% refers to a pure aeolian sand sample. All the soil materials are dried and then screened by a 1mm sieve, the required mass of the dry loess and the dry wind deposited sand is calculated according to the definition of the sand doping rate, and then the water content is increased in the prepared mixture according to the definition of the water content so as to meet the requirement.
The sand mixing rate is represented by Rs, and the mass ratio of the dry wind sand to the sum of the dry wind sand and the dry loess is used;
Rs＝m sand and sand /(m Sand and sand +m Soil )；①
Wherein: m is m Sand and sand Representing the mass (g) of the dry aeolian sand; m soil represents the mass (g) of dry loess; both water contents were 0%.
The water content of the aeolian sand-loess mixture refers to the ratio of the sum of the mass of water in the aeolian sand and loess to the sum of the dry aeolian sand and the dry loess:
W＝m w /(m sand and sand +m Soil )；②
Wherein: m is m w Represents the sum (g) of the mass of the aeolian sand and the water in loess.
The test uses compaction (heavy compaction) and static compaction (8.5 MPa) to test the maximum dry density and the optimal water content. The main reason is that the maximum dry density and the optimal water content of the aeolian sandy soil material and the mixture under the condition of high sand doping rate cannot be obtained by compaction, and the sample cannot be effectively compacted. Therefore, the soil material can attempt to acquire corresponding indexes by adopting a static compaction method. Compaction and compaction curves as shown in FIG. 1, it can be seen from FIG. 1 that the increase in sand incorporation has an important effect on compaction or compaction characteristics of the mix, and that 80% sand content of the mix is not able to complete a heavy compaction test at 80% and that the mix is prone to compaction during compactionAnd generating rubber clay, and the mixture cannot be bonded effectively. The mixture compaction profile obtained with static compaction of the mixture at 80% and 100% indicates that there is a minimum dry density of the aeolian sand. From the test results, it is shown that: the maximum dry densities obtained for 60% and 80% were 1.78g/cm, respectively 3 And 1.76g/cm 3 This also indicates that the mixture at this time has transitioned to cohesionless soil, but it is noted that 60% can be compacted and 80% cannot be compacted. So that a threshold value exists when the mixture is between 60 and 80 percent, and marks the transition of the mixture from the loess state to the sandy state.
Step 2, taking the residual shear strength as an investigation index, and carrying out a rule test of influence of sand doping rate and vertical pressure on the residual shear strength of the aeolian sand-loess mixture and steel interface; specifically, the interfacial mechanical behavior research is carried out through a ring shear test, wherein the test instrument of the ring shear test is a KTL-TTS interfacial shear instrument. The maximum shearing speed of the instrument is 125 degrees/min, the maximum vertical pressure can reach 1200kPa, wherein the vertical displacement precision can reach 0.0001mm, and the aeolian sand-loess mixture annular samples with different sand doping rates can be prepared by accurately recording the shearing expansion and shearing contraction characteristics; compared with the traditional direct shear apparatus, the apparatus can ensure that the shearing surface is invariable and the stress is uniform all the time in the shearing process, and the base can rotate at an unlimited angle, namely the shearing angle is arbitrary. The torque during the shearing process is automatically collected by a computer.
And carrying out annular shear tests of the aeolian sand-loess mixture and steel interfaces under different vertical pressure conditions. The annular shear test needs to control the compactness and the moisture content of the aeolian sand-loess mixture to be uniform. After the annular shearing test is finished, observing the particle distribution characteristics and particle crushing characteristics of the mixture test pieces with different sand doping rates through a scanning electron microscope; and obtaining the residual shear strength and deformation rule of the sand mixing rate, vertical pressure and shear rate on the aeolian sand-loess mixture and steel interface.
Specifically, in example 1, first, an aeolian sand-loess mixture having a compaction degree of 0.93 and a water content of 10% was prepared, six types of earth materials having a sand doping rate of 0, 20, 40, 60, 80, 100% and the like were respectively set, shearing tests were performed under conditions of vertical pressures of 50, 100, 200, and 400kPa, the shearing rate was controlled to be 1 °/min, and 24 tests were performed in total, and the numbers were 1# -24 respectively.
The test soil materials are screened and dried, corresponding weight is prepared and weighed according to the convention of sand doping rate (formula (1)), then water is sprayed according to 10% of the water content set by the test (formula (2)), and whether the water content meets the requirement or not is checked for use. The preparation of the mix was performed at a design compaction of 0.93, giving a total of 24 samples. Of which 17 # -20 # The samples were all mixtures with a sand blending rate of 80%, and the following table 1 shows the summarized parameters of the aeolian sand-loess mixture samples:
and step 3, determining the optimal blending ratio of the aeolian sand-loess mixture meeting the investigation index according to the experimental result of the step 2. In this embodiment, the critical value range of the sand doping rate is 60% -80%.
Table 1 shows the summarized parameters of the aeolian sand-loess mixture samples
Table 2 is a summary of the ring shear protocol
Through the above test, the relationship between the shear stress and the shear displacement of the 1-24# sample is shown in fig. 2, and it is found by analyzing fig. 2 that the shear stress exhibits a two-stage development with the change of the shear displacement. When the shear displacement is developed to 1-2.5mm, the shear stress is rapidly increased to a considerable peak value; secondly, the shear stress development becomes gentle, and the value thereof shows a very slow increasing trend with increasing shear displacement. The shear stress increases slightly but with very limited magnitude from 5mm up to 30 mm. This also means that the shearing at this point has already entered the residual phase and that the contact between the steel interface and the mix no longer has a wide range of strength variations. Can take 30mm shearing displacement pairStress τ of shear n This value can be used to analyze the residual strength characteristics between the steel interface and the mix, which is the residual strength between the aeolian sand-loess mixture-steel interface.
The relationship curve between the vertical strain and the shear displacement of the No. 1-24 samples is shown in FIG. 3, and as can be seen from FIG. 3, the aeolian sand-loess mixture samples show 3-section (compression-shear expansion-compression) development change characteristics under the action of lower pressure of 50-100 kPa. The chance of the mix developing shear at low pressure will increase with increasing sand incorporation. Under the same vertical pressure condition, the residual strength is reduced due to the improvement of the sand doping rate; under the condition of uniform sand mixing rate, the improvement of vertical pressure can increase the residual strength.
The relationship between the residual internal friction angle of the mixture-steel interface, the residual cohesion of the mixture-steel interface and the sand inclusion rate is plotted in fig. 4. In FIG. 4 (a), the residual cohesion is shown to decrease drastically between 0 and 70% in sand doping rate, and after more than 70%, the interfacial residual cohesion is maintained substantially constant, for example, the cohesion is less than 1kPa at 80% and 100%. The clay has a decisive effect on cohesive force when the sand doping rate is lower, but the clay content is reduced after the sand doping rate is increased, at the moment, the contact proportion of a steel interface and the clay is smaller and smaller, the proportion of aeolian sand is larger and larger, and the cohesive force of the aeolian sand-loess interface is always the false cohesive force formed by embedding and meshing between sand particles and interfaces.
In fig. 4 (b), the residual internal friction angle at the interface between the mix and the steel showed a decreasing trend with increasing sand incorporation rate, but the decrease was not very significant. Under the condition of high sand mixing rate, the binding effect is reduced, the meshing effect of the aeolian sand particles and the steel plate is improved, the reduction of friction capacity caused by the binding performance is made up, the sand particles are crushed in the grinding and shearing processes, fine particles fill interface pores, the friction effect is affected to a certain extent, and the friction effect is also an important reason that the reduction amplitude of the friction angle in the interface of the mixture is not large.
The samples were subjected to electron microscope scanning under different sand doping rates, and the results are shown in fig. 5. The image at 300 times is shown in the figure, sand particles are gradually increasing, and loess particles are decreasing, which also demonstrates the influence mechanism of the sand doping rate on the interfacial shear strength.
Through experimental researches on different parameters, the application finally discovers that the design method of the system about the optimal sand doping rate is finally formed through the researches on aeolian sand-loess blends with different parameters and different sand doping rates through a ring shear test. Summarizing the law of sand mixing rate, residual shear strength of vertical pressure on aeolian sand-loess mixture and steel interface and deformation, based on the law, the method can be used for better determining the mixed sand mixing rate threshold value in the foundation, and the treatment difficulty of the pure aeolian sand foundation is greatly reduced. The construction of foundation treatment of the building and pile in the area provides powerful data support. In the subsequent foundation treatment process, the selection of the proper sand doping rate can be performed according to the data of the ground building.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.
Claims (10)
1. The design method of the aeolian sand-loess mixture blending ratio is characterized by comprising the following steps of:
step 1, examining a target construction foundation, and making a mechanical research test scheme of a steel soil interface;
step 2, taking the residual shear strength as an investigation index, and carrying out a rule test of influence of sand doping rate and vertical pressure on the residual shear strength of the aeolian sand-loess mixture and steel interface;
and step 3, determining the optimal blending ratio of the aeolian sand-loess mixture meeting the investigation index according to the experimental result of the step 2.
2. The method for designing an optimal blending ratio of an aeolian sand-loess mixture according to claim 1, wherein in step 2, interfacial mechanical behavior research is performed by a ring shear test.
3. The method for designing an optimal blending ratio of an aeolian sand-loess mixture according to claim 1, wherein in step 1, the foundation investigation includes soil sample collection of a target construction area, and the maximum dry density and the optimal water content of the mixture are obtained.
4. The method for designing an optimal blending ratio of aeolian sand-loess mixture as set forth in claim 3, wherein the test includes: a. performing compaction or compaction tests on the mixture under different sand blending rate conditions to obtain the maximum dry density and the optimal water content of the aeolian sand-loess mixture; b. preparing aeolian sand-loess mixture annular samples with different sand doping rates; and carrying out annular shear tests of aeolian sand-loess mixtures and steel interfaces under different sand doping rates and vertical pressure conditions.
5. The method for designing an optimal blending ratio of an aeolian sand-loess mixture according to claim 4, wherein the annular shear test requires control of compactness and moisture content of the aeolian sand-loess mixture to be maintained uniformly.
6. The method for designing the optimal blending ratio of the aeolian sand-loess mixture according to claim 3, characterized in that after the completion of the annular shearing test, the particle distribution characteristics and the particle crushing characteristics of the mixture test pieces with different sand blending ratios are observed through a scanning electron microscope; and obtaining the sand mixing rate, the residual shear strength of the vertical pressure on the aeolian sand-loess mixture and the steel interface and the deformation rule.
7. The method for designing an aeolian sand-loess mixture blend ratio as set forth in claim 3, characterized in that the maximum dry density is tested as follows: the compaction method is suitable for aeolian sand-loess mixture samples with high sand doping rate, and the static compaction method is suitable for aeolian sand-loess mixture samples with low sand doping rate, and the critical value range of the sand doping rate is 60% -80%; collecting test soil materials in a target construction area, and respectively preparing aeolian sand-loess mixed soil materials with the same water content and different sand contents according to a mode of firstly dry mixing and then humidifying; the aeolian sand-loess mixed soil material comprises samples with sand content of 0%, 20%, 40%, 60%, 80% and 100%, wherein 0% refers to a pure loess sample and 100% refers to a pure aeolian sand sample.
8. The method for designing the mixing ratio of aeolian sand to loess mixture according to claim 7, characterized in that all the earth materials are dried and then screened by a 1mm sieve, the mass of the dry loess and the mass of the dry aeolian sand required by each sample are calculated respectively, and then the water content is increased in the prepared mixture according to the definition of the water content, so as to obtain the corresponding samples:
the sand mixing rate is represented by Rs, and the mass ratio of the dry wind sand to the sum of the dry wind sand and the dry loess is used;
Rs＝m sand and sand /(m Sand and sand +m Soil )；①
Wherein: m is m Sand and sand Representing the mass of the dry aeolian sand, wherein the unit is g; m soil represents the mass of dry loess in g; the water content of the two is 0%;
the water content of the aeolian sand-loess mixture refers to the ratio of the sum of the mass of water in the aeolian sand and loess to the sum of the dry aeolian sand and the dry loess:
w＝m w /(m sand and sand +m Soil )；②
Wherein: m is m w Represents the sum of the mass of the aeolian sand and the water in loess, and the unit is g.
9. The method for designing the mixing ratio of the aeolian sand to the loess mixture according to claim 2, characterized in that the ring shear test includes ring shear tests under different vertical pressure conditions, and the interval of the vertical pressure is 50 to 400kPa.
10. The method for designing an air-blown sand-loess mixture as recited in claim 4, wherein the critical value of the sand doping rate is in the range of 60% -80%.
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| CN117647451A (en) * | 2024-01-19 | 2024-03-05 | 中国电建集团西北勘测设计研究院有限公司 | Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces |
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| CN117647451A (en) * | 2024-01-19 | 2024-03-05 | 中国电建集团西北勘测设计研究院有限公司 | Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces |
| CN117647451B (en) * | 2024-01-19 | 2024-04-12 | 中国电建集团西北勘测设计研究院有限公司 | Device and method for testing shearing strength of undisturbed loess multi-group shearing surfaces |
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