CN114855748B - Output torque-based cement mixing pile soil layer identification method - Google Patents
Output torque-based cement mixing pile soil layer identification method Download PDFInfo
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Abstract
A cement mixing pile soil layer identification method based on output torque comprises the following steps: determining a plurality of soil layer types contained in a construction area through reconnaissance, and acquiring physical and mechanical parameters of each soil layer type; obtaining a design construction depth, and dividing the design construction depth into a plurality of depth sections; before construction, acquiring friction torque between the pile embracing device and a drill rod corresponding to each depth section; in the construction process, when the stirring head descends to the bottom end of each depth section, recording the corresponding depth section as a target depth section, and calculating the driving torque for damaging each soil layer type when the stirring head is at the target depth section according to a preset calculation rule; and acquiring an actually measured torque measured by the torque sensor, and determining the soil layer type of the target depth section based on the driving torque and the actually measured torque obtained by calculation. According to the method, the soil layer types corresponding to different depths are identified through different torques required by the stirring head to destroy different soil layer types and the actually measured torques of the torque sensors.
Description
Technical Field
The invention belongs to the technical field of mixing pile construction, and particularly relates to a cement mixing pile soil layer identification method based on output torque.
Background
A deep cement-soil mixing pile is a mode of foundation treatment, and it uses cement as solidifying agent, and utilizes a special mixing machine to mix the solidifying agent with peripheral soil body by means of slurry-spraying mode in the deep portion of foundation, then produces physical and chemical reaction to make the soft soil be hardened into the excellent and good foundation with integrity, water stability and a certain strength. Different technological parameters need to be adopted for different soil layers during construction of the deep cement mixing pile, only 1 investigation borehole is usually adopted in one construction area in engineering practice, and all mixing pile constructions adjust the construction technological parameters according to the soil layer distribution conditions of the investigation borehole. However, a large number of engineering soil layers are complicated in distribution, and the actual construction soil layer distribution is not consistent with the exploration holes, so that the construction process parameters are not suitable for the soil layers, so that the construction quality of partial pile sections is poor, and even the piles are not formed.
Disclosure of Invention
The invention aims to provide a cement mixing pile soil layer identification method based on output torque, which identifies soil layer types corresponding to different depths through different torques required by a mixing head to damage different soil layer types and actual measurement torques of torque sensors.
The invention is realized by the following technical scheme:
a cement mixing pile soil layer identification method based on output torque comprises a mixing assembly, wherein the mixing assembly comprises a pile embracing device, a plurality of drill rods arranged on the pile embracing device and a power head connected with the drill rods and used for driving the drill rods to rotate, a mixing head is arranged at the bottom end of each drill rod, a plurality of layers of blades are arranged on the outer side wall of the mixing head, a cutting blade is arranged at the bottom end of the mixing head, the cement mixing pile soil layer identification method further comprises an intelligent terminal, a torque sensor used for measuring the torque of the drill rods is arranged between the drill rods and the power head, and the intelligent terminal is connected with the torque sensor;
the method comprises the following steps:
surveying a construction area, determining various soil layer types contained in the construction area, and acquiring physical and mechanical parameters of each soil layer type;
obtaining a design construction depth, and dividing the design construction depth into a plurality of depth sections;
before construction, acquiring friction torque between the pile gripper and the drill rod when the stirring head descends to the bottom end of each depth section, and acquiring the friction torque corresponding to each depth section;
in the construction process, when the stirring head descends to the bottom end of each depth section, recording the depth section where the stirring head is located as a target depth section, and calculating the driving torque for damaging each soil layer type when the stirring head is in the target depth section according to a preset calculation rule on the basis of the physical mechanical parameters of each soil layer type and the friction torque corresponding to the target depth section;
and acquiring the actual measurement torque measured by the torque sensor when the stirring head is in the target depth section, and determining the soil layer type of the target depth section based on the driving torque for destroying each soil layer type when the stirring head is in the target depth section and the actual measurement torque measured by the torque sensor.
Further, the physical and mechanical parameters comprise cohesion, friction angle, weight, friction coefficient and lateral pressure coefficient;
the step of calculating the driving torque for damaging each soil layer type when the stirring head is at the target depth section according to the preset calculation rule comprises the following steps:
sequentially selecting a target soil layer type from the multiple soil layer types, and calculating the driving torque of the stirring head for damaging the target soil layer type in the target depth section according to the following formula to obtain the driving torque of the stirring head for damaging each soil layer type in the target depth section:
M drive the ＝M 1 +M 2 +M 3 (4)
In the formula, M 2 The friction torque of soil and the drill rod, d is the diameter of the drill rod, n' is the number of layers of the overburden layer above the target depth section, and sigma zi Vertical effective stress, k, of soil body in the i-th overlying soil layer si Is the lateral pressure coefficient of the soil of the overburden layer on the ith layer, mu si The friction coefficient of the soil layer on the ith layer and the drill rod, h i Thickness of the topsoil layer of the i-th layer, c u Shear strength, c cohesive strength of the target soil layer type,
friction angle for target soil type, σ overburden pressure above target depth section, M 3 Is a stirring head and soilTorque between l 1 Length of cutting blade, B 1 Is the width of the cutting blade, θ 1 For the angle of inclination of the cutting blade, V Through the tube For the head descent speed, n for the head rotation speed, S t For soil sensitivity, k is the number of leaf layers, l 2 Is the length of the blade, B 2 Is the width of the blade, theta 2 Angle of inclination of the blade, M Drive the Drive torque, M, for the power head to drive the drill rod 1 And the friction torque corresponding to the target depth section.
Further, the derivation process of equation (3) is as follows:
according to the principle of a cross plate shear test, the method comprises the following steps:
in formula (II) to' 1 For overcoming the moment, M ', required for the shear strength of the cylindrical soil mass' 2 The moment required for overcoming the shear strength of the top surface soil body and the bottom surface soil body, M is the total moment for overcoming the shear strength of the soil body, d is the diameter of the drill rod, l is the length of the blade or the length of the cutting blade, B is the width of the blade or the width of the cutting blade, and theta is the blade inclination angle or the cutting blade inclination angle;
in the construction process, the relation that the cutting blade stirs and destroys the soil body is as follows:
h 1 ＝B 1 sinθ 1 -h 2 (9)
in the formula, h 2 Stirring the raw material for cutting bladeThickness of the soil, h 1 Thickness of disturbed soil for cutting blade agitation;
substituting equation (8) and equation (9) into equation (7) in consideration of the lowering of the stirring head yields:
in the formula, M Through 1 Is the torque of the cutting blade;
calculating the torque of the blade:
in the formula, M Through 1 Is the torque of the blade;
the torque between the stirring head and the soil is as follows:
M 3 ＝M tubular pipe 1 +kM Through 2 (12)；
Substituting equation (10) and equation (11) into equation (12) yields:
further, the friction torque between the pile gripper and the drill rod when the stirring head descends to the bottom end of each depth section is obtained, and the step of obtaining the friction torque corresponding to each depth section comprises the following steps:
determining a test point in the construction area, and determining the actual soil layer distribution in the design construction depth range below the test point to obtain the actual soil layer type corresponding to each depth section;
constructing the test points through the stirring assembly, and recording the depth section where the stirring head is located as a target depth section when the stirring head descends to the bottom end of each depth section;
based on physical and mechanical parameters of an actual soil layer type, calculating friction torque between soil and a drill rod when a stirring head descends to a target depth section according to a formula (1), and calculating torque between the stirring head and the soil when the stirring head descends to the target depth section according to a formula (2) and a formula (3);
acquiring an actual measurement torque measured by a torque sensor when the stirring head descends to a target depth section;
calculating friction torque corresponding to the target depth section according to a formula (4) based on the actually measured torque, the friction torque between the soil and the drill rod obtained through calculation and the torque between the stirring head and the soil;
and obtaining the friction torque corresponding to each depth section based on the friction torque corresponding to the target depth sections.
Compared with the prior art, the invention has the beneficial effects that:
(1) In the construction process, driving torques required by the stirring head to damage different soil layers are calculated layer by layer from top to bottom, soil layer types corresponding to different depths are sequentially identified according to actual measurement torques measured by the torque sensor, and the accuracy of soil layer type judgment is improved;
(2) The method provides soil layer type division data for the targeted construction of each mixing pile, provides a basis for adjusting process parameters of each mixing pile, and can effectively improve the uniformity of the whole mixing pile and reduce the construction cost.
Drawings
FIG. 1 is a flow chart illustrating steps of a method for identifying a soil layer of a cement mixing pile based on output torque according to the present invention;
fig. 2 is a schematic structural diagram of a stirring assembly in the output torque-based cement stirring pile soil layer identification method.
In the figure, 1-pile gripper, 2-drill rod, 3-power head, 4-stirring head, 5-blade, 6-cutting blade and 7-torque sensor.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not construed as indicating or implying relative importance.
It should be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships conventionally put in use of products of the present invention, and are only for convenience of description and simplification of description, but do not indicate or imply that the devices or elements referred to must have specific orientations, be constructed in specific orientations, and be operated, and thus, should not be construed as limiting the present invention.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a stirring assembly in the output torque-based cement stirring pile soil layer identification method of the present invention. The utility model provides a cement mixing pile soil horizon identification method based on output torque, including the stirring subassembly, the stirring subassembly includes the pile gripper, set up many drilling rods on the pile gripper and be connected with many drilling rods and be used for driving the rotatory unit head of drilling rod, the bottom of drilling rod is equipped with the stirring head, be equipped with the multilayer blade on the stirring head lateral wall, the stirring head bottom is equipped with cutting blade, still include intelligent terminal, be equipped with the torque sensor who is used for measuring the drilling rod moment of torsion between drilling rod and the unit head, intelligent terminal is connected with torque sensor.
Referring to fig. 1, fig. 1 is a flowchart illustrating steps of a method for identifying a soil layer of a cement mixing pile based on an output torque according to the present invention. The invention relates to a cement mixing pile soil layer identification method based on output torque, which comprises the following steps:
s1, surveying a construction area, determining various soil layer types contained in the construction area, and acquiring physical and mechanical parameters of each soil layer type;
s2, obtaining a design construction depth, and dividing the design construction depth into a plurality of depth sections;
s3, before construction, acquiring friction torque between the pile gripper and the drill rod when the stirring head descends to the bottom end of each depth section, and acquiring the friction torque corresponding to each depth section;
s4, in the construction process, when the stirring head descends to the bottom end of each depth section, recording the depth section where the stirring head is located as a target depth section, and calculating the driving torque for damaging each soil layer type when the stirring head is in the target depth section according to a preset calculation rule based on the physical and mechanical parameters of each soil layer type and the friction torque corresponding to the target depth section;
and S5, acquiring actual measurement torque measured by the torque sensor when the stirring head is in the target depth section, and determining the soil layer type of the target depth section based on the driving torque for damaging each soil layer type when the stirring head is in the target depth section and the actual measurement torque measured by the torque sensor.
In the step S1, the soil layer distribution in the construction area is surveyed by a drilling survey method, several soil layer types in the construction area are determined to obtain various soil layer types included in the construction area, and then the physical mechanical parameters of each soil layer type are tested to obtain the physical mechanical parameters corresponding to each soil layer type.
In the step S2, the design construction depth is the length of the mixing pile, the design construction depth is divided into a plurality of depth sections, the setting of the depth sections can be determined according to the required identification precision, generally, soil layers smaller than 0.5 m in geotechnical investigation cannot be divided into soil layer types alone, that is, even if there are two different types of soil within 0.5 m, the soil layers are treated as one soil layer type in practical application, and therefore the depth sections should not be smaller than 0.5 m. In this embodiment, the depth segment is taken to be 0.5 meters.
In the step S3, the pile gripper controls the drill rod to keep vertical, friction force exists between the drill rod and the pile gripper, the friction force is mainly influenced by tightness degree and rotation speed, the tightness degree and the rotation speed are not greatly changed in the construction process, and friction torque between the pile gripper and the drill rod can be processed according to different depths. Before soil layer identification, friction torque between the pile gripper and the drill rod when the stirring head descends to the bottom end of each depth section is acquired for subsequent calculation.
Further, the physical and mechanical parameters include cohesive force, friction angle, gravity, friction coefficient and lateral pressure coefficient, and in step S3, the friction torque between the pile gripper and the drill rod when the stirring head descends to the bottom end of each depth section is obtained, and the step of obtaining the friction torque corresponding to each depth section includes:
s31, determining a test point in a construction area, and determining actual soil layer distribution in a design construction depth range below the test point to obtain actual soil layer types corresponding to each depth section;
s32, constructing the test points through the stirring assembly, and recording the depth section where the stirring head is located as a target depth section when the stirring head descends to the bottom end of each depth section;
s33, based on physical and mechanical parameters of the actual soil layer type, calculating the friction torque between the soil and the drill rod when the stirring head descends to a target depth section according to a formula (1), and calculating the torque between the stirring head and the soil when the stirring head descends to the target depth section according to a formula (2) and a formula (3);
s34, acquiring an actually measured torque measured by the torque sensor when the stirring head descends to a target depth section;
s35, calculating to obtain a friction torque corresponding to the target depth section according to a formula (4) based on the actually measured torque, the friction torque between the soil and the drill rod obtained through calculation and the torque between the stirring head and the soil;
and S36, obtaining the friction torque corresponding to each depth section based on the friction torque corresponding to the target depth sections.
In the step S31, since in the step S1, it is determined that there are several soil layer types in the construction area by the drilling exploration method in the construction area, the test point may select a drilling position of the drilling exploration method, and therefore, the actual soil layer types corresponding to each depth section below the test point may be obtained by taking out soil samples at different depths of the test point through the exploration hole, that is, dividing the actual soil layer distribution at the test point.
In the step S32, the test point is constructed by using the stirring assembly, and the depth sections are numbered according to the depth sequence, for example, when the stirring head descends to 0.5 meter below the ground, that is, when the stirring head descends to the bottom end of the first depth section, the first depth section is recorded as the target depth section, then the stirring head continues descending to 1 meter below the ground, that is, the stirring head descends to the bottom end of the second depth section, and the second depth section is recorded as the target depth section, so that the depth sections are sequentially recorded as the target depth sections through the continuous descending of the stirring head.
In the step S33, since the actual soil layer distribution within the designed construction depth range below the test point is known, when the stirring head descends to the bottom end of the target depth section, the number of the overburden layers above the target depth section can be known according to the actual soil layer distribution, and the vertical effective stress σ of the soil body of each overburden layer can be known zi Lateral pressure coefficient mu of earth si Thickness h of the soil i And the diameter d of the drill rod mayMeasured directly, and thus according to formula (1)
Calculating the friction torque M of the soil and the drill rod when the stirring head descends to the target depth section 2 . And similarly, obtaining the overburden pressure sigma above the target depth section according to the number of the overburden above the target depth section, the actual soil type of each overburden, the thickness of each overburden and the gravity of each overburden, wherein if the construction area is below the water surface, the overburden pressure sigma above the target depth section is added with the water pressure, and the water pressure is equal to the gravity of the water multiplied by the depth of the water. Specifically, taking the construction area below the water surface as an example, the overburden pressure σ above the target depth section is calculated by the following formula:
in the formula, gamma Water (W) Is the gravity of water, h Water (I) Is the depth of water, n' is the number of overburden layers above the target depth section, gamma Soil i Is the severity of the overburden on the ith layer, h Soil i The thickness of the overburden layer on the ith layer is shown, wherein i =1, 2, 8230, n ′ 。
The cohesive force c and the friction angle can be obtained according to the actual soil layer type corresponding to the target depth section
Thus according to formula (2)
Calculating the shear strength of the actual soil layer type corresponding to the target depth section when the stirring head descends to the target depth section, and combining the soil sensitivity of the actual soil layer type corresponding to the target depth section with the size and the number of layers of the cutting blade and the blade on the stirring head according to a formula (3)>
Calculating the torque M between the actual soil layer type soil corresponding to the target depth section and the stirring head when the stirring head descends to the target depth section 3 。
In step S34, an actually measured torque measured by the torque sensor is obtained, where the actually measured torque is a driving torque required by the power head to drive the drill rod to rotate when the stirring head descends to the target depth section.
In the above step S35, formula (4) M Drive the ＝M 1 +M 2 +M 3 Variation to give M 1 ＝M Drive the -M 2 -M 3 Driving torque M obtained in step S34 Drive the And the friction torque M of the soil and the drill rod obtained in the step S33 2 And the torque M between the stirring head and the soil layer 3 Substituting to obtain the friction torque between the pile gripper and the drill rod when the stirring head descends to the target depth section, and obtaining the friction torque M corresponding to the target depth section 1 。
In step S36, the stirring head is lowered to the design construction depth, and the friction torques corresponding to the plurality of target depth sections are sequentially calculated from step S33 to step S35, that is, the friction torques corresponding to the respective depth sections are obtained.
In the step S4, the depth segments are numbered according to the depth sequence, and in the construction process, if the stirring head descends to 0.5 meter below the ground, that is, the stirring head descends to the bottom end of the first depth segment, the first depth segment is recorded as the target depth segment, then the stirring head continues to descend to 1 meter below the ground, that is, the stirring head descends to the bottom end of the second depth segment, and the second depth segment is recorded as the target depth segment, so that the depth segments are sequentially recorded as the target depth segments through the continuous descending of the stirring head. And then calculating the driving torque for damaging each soil layer type when the stirring head is in the target depth section according to a preset calculation rule based on the physical and mechanical parameters of each soil layer type and the friction torque corresponding to the target depth section.
Further, in step S4, the physical mechanical parameters include cohesion, friction angle, weight, friction coefficient, and lateral pressure coefficient;
the step of calculating the driving torque for damaging each soil layer type when the stirring head is in the target depth section according to the preset calculation rule comprises the following steps:
s41, sequentially selecting a target soil layer type from the multiple soil layer types, and calculating the driving torque for damaging the target soil layer type when the stirring head is in the target depth section according to the following formula to obtain the driving torque for damaging each soil layer type when the stirring head is in the target depth section:
M drive the ＝M 1 +M 2 +M 3 (4)
In the formula, M 2 The friction torque of soil and the drill rod, d is the diameter of the drill rod, n' is the number of layers of the overburden layer above the target depth section, and sigma zi The vertical effective stress k of the soil body of the soil layer covering the ith layer si Is the lateral pressure coefficient of the soil of the overburden layer on the ith layer, mu si The friction coefficient h between the soil of the soil layer covering the ith layer and the drill rod i Thickness of the overburden on the i-th layer, c u Shear strength, c cohesive strength of the target soil layer type,
friction angle for target soil type, σ overburden pressure above target depth section, M 3 Is the torque between the stirring head and the soil, l 1 Length of cutting blade, B 1 Width of cutting blade, theta 1 Angle of inclination of cutting blade, V Through tube For stirringHead descent speed, n being the rotational speed of the mixing head, S t For soil sensitivity, k is the number of leaf layers, l 2 Is the length of the blade, B 2 Is the width of the blade, θ 2 Angle of inclination of the blade, M Drive the Drive torque, M, for driving the drill rod by the power head 1 And friction torque corresponding to the target depth section.
In the step S41, when the stirring head descends to the target depth section, the soil layer type of the depth section above the target depth section is identified and known, and the soil layer type corresponding to the target depth section is unknown, so that one target soil layer type is sequentially selected from the plurality of soil layer types, the target soil layer type is assumed as the soil layer type of the target depth section, thereby determining the number of the soil layer types contacting the drill rod, and determining the soil body vertical effective stress σ of each soil layer type zi Lateral pressure coefficient k of earth si Coefficient of friction mu between soil and drill rod si And thickness of the soil, thereby according to the formula (1)
Calculating to obtain the friction torque M of the soil and the drill rod when the stirring head descends to the target depth section when the soil layer type corresponding to the target depth section is the target soil layer type 2 Similarly, the overburden pressure sigma above the target depth section can be obtained according to the number of the overburden above the target depth section, the soil type of each overburden, the thickness of each overburden and the weight of each overburden, and the cohesive force c and the friction angle/greater can be obtained according to the target soil type corresponding to the target depth section>
Therefore according to formula (2)>
Calculating the shear strength of the target soil layer type when the stirring head descends to the target depth section, and calculating the shear strength of the target soil layer type according to the target soil layer typeThe soil sensitivity is combined with the size of a cutting blade on the stirring head and the size and the layer number of blades on the stirring head according to a formula (3)
Calculating to obtain the torque M between the stirring head and the soil of the target soil layer type when the soil layer type corresponding to the target depth section is the target soil layer type and the stirring head descends to the target depth section 3 Then according to the friction torque corresponding to the target depth section, obtaining the friction torque M between the pile gripper and the drill rod when the stirring head descends to the target depth section 1 According to the formula (4) M Drive the ＝M 1 +M 2 +M 3 Calculating to obtain a driving torque M for damaging the target soil layer type when the stirring head is at the target depth section Drive the . And assuming a plurality of soil layer types contained in the construction area as the soil layer types of the target depth section in sequence, and obtaining the driving torque for damaging each soil layer type when the stirring head is in the target depth section. />
Further, in step S41, the derivation process of equation (3) is as follows:
according to the cross plate shear test principle, the torque can be divided into two parts, one part is used for overcoming the soil shear strength of the side surface formed into a cylindrical surface, and the other part is used for overcoming the soil shear strength of the top surface and the bottom surface formed into a ring, so that the torque is obtained:
m 'in the formula' 1 For overcoming the moment, M ', required for the shear strength of the cylindrical soil mass' 2 The moment required for overcoming the shear strength of the top surface soil body and the bottom surface soil body, M is the total moment for overcoming the shear strength of the soil body, d is the diameter of the drill rod, l is the length of the blade or the length of the cutting blade, B is the width of the blade or the width of the cutting blade, and theta is the blade inclination angle or the cutting blade inclination angle;
in the work progress, in the soil body that cutting blade stirring destroyed, the soil body of cutting blade bottom destruction is original state soil, and when cutting blade upper portion got into the soil body stirring, the soil body was the disturbed soil of process cutting blade bottom stirring, and consequently the relation that cutting blade stirring destroyed the soil body was:
h 1 ＝B 1 sinθ 1 -h 2 (9)
in the formula, h 2 Thickness of undisturbed soil for cutting blade stirring, h 1 Thickness of disturbed soil for cutting blade agitation;
considering the condition that the stirring head descends, the stirring head is driven to move 1 And h 2 Substituting into formula (7) and considering the soil sensitivity after soil layer construction disturbance to obtain:
substituting equation (8) and equation (9) into equation (13) yields:
in the formula, M Tubular pipe 1 Is the torque of the cutting blade;
the soil body of blade stirring cutting all is the disturbed soil after the cutting blade stirring, consequently need consider the soil body sensitivity after the soil layer construction disturbance, calculates the moment of torsion of blade:
in the formula, M Tubular pipe 1 Is the torque of the blade;
the torque between the stirring head and the soil is as follows:
M 3 ＝M through 1 +kM Tubular pipe 2 (12)；
Substituting equation (10) and equation (11) into equation (12) yields:
in the step S5, the driving torque of the mixing head that damages each soil type in the target depth section may obtain a one-to-one correspondence relationship between a plurality of soil types and a plurality of driving torques in the target depth section, then the torque sensor may obtain an actual measurement torque of the mixing head in the target depth section, where the actual measurement torque is a torque of the mixing head that drives the drill rod in the target depth section, and the actual measurement torque may be compared with the driving torque of the mixing head that damages each soil type in the target depth section to obtain a driving torque closest to the actual measurement torque, and the soil type corresponding to the driving torque closest to the actual measurement torque may be used as the soil type in the target depth section. Therefore, when the stirring head descends to the designed construction depth, the soil layer types of different depth sections can be sequentially confirmed from top to bottom, so that the soil layer types of all the depth sections can be obtained, and the identification of the stirring pile construction soil layer is realized.
Compared with the prior art, the invention has the beneficial effects that:
(1) In the construction process, driving torques required by the stirring head to damage different soil layers are calculated layer by layer from top to bottom, soil layer types corresponding to different depths are sequentially identified according to actual measurement torques measured by the torque sensor, and the accuracy of soil layer type judgment is improved;
(2) The method provides soil layer type division data for the targeted construction of each mixing pile, provides a basis for adjusting process parameters of each mixing pile, and can effectively improve the uniformity of the whole mixing pile and reduce the construction cost.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention will still fall within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.
Claims (3)
1. A cement mixing pile soil layer identification method based on output torque comprises a mixing assembly, wherein the mixing assembly comprises a pile embracing device, a plurality of drill rods arranged on the pile embracing device and a power head connected with the drill rods and used for driving the drill rods to rotate, a mixing head is arranged at the bottom end of each drill rod, a plurality of layers of blades are arranged on the outer side wall of the mixing head, and a cutting blade is arranged at the bottom end of the mixing head;
the method comprises the following steps:
surveying a construction area, determining various soil layer types contained in the construction area, and acquiring physical mechanical parameters of each soil layer type, wherein the physical mechanical parameters comprise cohesive force, a friction angle, gravity, a friction coefficient and a lateral pressure coefficient;
obtaining a design construction depth, and dividing the design construction depth into a plurality of depth sections;
before construction, acquiring friction torque between the pile gripper and a drill rod when the stirring head descends to the bottom end of each depth section, and acquiring the friction torque corresponding to each depth section;
in the construction process, when the stirring head descends to the bottom end of each depth section, recording the depth section where the stirring head is located as a target depth section, and calculating the driving torque for damaging each soil layer type when the stirring head is in the target depth section according to a preset calculation rule on the basis of the physical and mechanical parameters of each soil layer type and the friction torque corresponding to the target depth section; wherein, the step of calculating the driving torque for damaging each soil layer type when the stirring head is at the target depth section according to a preset calculation rule comprises the following steps:
sequentially selecting a target soil layer type from the multiple soil layer types, and calculating the driving torque of the stirring head for damaging the target soil layer type in the target depth section according to the following formula to obtain the driving torque of the stirring head for damaging each soil layer type in the target depth section:
M drive the ＝M 1 +M 2 +M 3 (4)
In the formula, M 2 The friction torque of soil and the drill rod, d is the diameter of the drill rod, n' is the number of layers of the overburden layer above the target depth section, and sigma zi The vertical effective stress k of the soil body of the soil layer covering the ith layer si Is the lateral pressure coefficient of the soil of the overburden layer on the ith layer, mu si The friction coefficient of the soil layer on the ith layer and the drill rod, h i Thickness of the overburden on the i-th layer, c u Shear strength, c cohesive strength of the target soil layer type,
friction angle for target soil type, σ overburden pressure above target depth section, M 3 For the torque between the stirring head and the soil,/ 1 Length of cutting blade, B 1 Width of cutting blade, theta 1 Angle of inclination of cutting blade, V Through the tube For the head descent speed, n for the head rotation speed, S t As a soil bodySensitivity, k is the number of leaf layers,/ 2 Is the length of the blade, B 2 Is the width of the blade, theta 2 As angle of inclination of the blades, M Drive the Drive torque, M, for the power head to drive the drill rod 1 Friction torque corresponding to the target depth section;
and acquiring the actual measurement torque measured by the torque sensor when the stirring head is in the target depth section, and determining the soil layer type of the target depth section based on the driving torque for destroying each soil layer type when the stirring head is in the target depth section and the actual measurement torque measured by the torque sensor.
2. The output torque-based cement mixing pile soil layer identification method according to claim 1, characterized in that the derivation process of the formula (3) is as follows:
according to the principle of a cross plate shear test, the method comprises the following steps:
m 'in the formula' 1 For overcoming the moment, M ', required for the shear strength of the cylindrical soil mass' 2 The moment required for overcoming the shear strength of the top surface soil body and the bottom surface soil body, M is the total moment for overcoming the shear strength of the soil body, d is the diameter of the drill rod, l is the length of the blade or the length of the cutting blade, B is the width of the blade or the width of the cutting blade, and theta is the blade inclination angle or the cutting blade inclination angle;
in the construction process, the relation that the cutting blade stirs and destroys the soil body is as follows:
h 1 ＝B 1 sinθ 1 -h 2 (9)
in the formula, h 2 Thickness of undisturbed soil for cutting blade stirring, h 1 Thickness of disturbed soil for cutting blade agitation;
substituting equation (8) and equation (9) into equation (7) in consideration of the lowering of the stirring head yields:
in the formula, M Tubular pipe 1 Is the torque of the cutting blade;
calculating the torque of the blade:
in the formula, M Tubular pipe 1 Is the torque of the blade;
the torque between the stirring head and the soil is as follows:
M 3 ＝M tubular pipe 1 +kM Tubular pipe 2 (12)；
Substituting equation (10) and equation (11) into equation (12) yields:
3. the method for identifying the soil layer of the cement mixing pile based on the output torque as claimed in claim 1, wherein the step of obtaining the friction torque between the pile gripper and the drill rod when the mixing head descends to the bottom end of each depth section to obtain the friction torque corresponding to each depth section comprises:
determining a test point in the construction area, and determining the actual soil layer distribution in the design construction depth range below the test point to obtain the actual soil layer type corresponding to each depth section;
constructing the test points through the stirring assembly, and recording the depth section where the stirring head is located as a target depth section when the stirring head descends to the bottom end of each depth section;
based on physical and mechanical parameters of an actual soil layer type, calculating friction torque between soil and a drill rod when the stirring head descends to a target depth section according to a formula (1), and calculating torque between the stirring head and the soil when the stirring head descends to the target depth section according to a formula (2) and a formula (3);
acquiring an actual measurement torque measured by a torque sensor when the stirring head descends to a target depth section;
calculating friction torque corresponding to the target depth section according to a formula (4) based on the actually measured torque, the friction torque of the soil and the drill rod obtained through calculation and the torque between the stirring head and the soil;
and obtaining the friction torque corresponding to each depth section based on the friction torque corresponding to the target depth sections.
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