140 results about "Suction stress" patented technology

A slope safety and stability analysis method based on an integrated sensor and an intelligent algorithm comprises the following steps: acquiring initial values of geometric parameters (including height, gradient and width) of a slope and basic physical parameters (weight, internal friction angle and cohesive force) of a soil body through a method of combining in-situ static sounding and an indoor test; an improved integrated sensor slope state monitoring device is adopted to continuously obtain state parameters such as water content, matrix suction, internal three-way displacement, an inclination angle and soil pressure of a slope soil body, and multi-dimensional dynamic monitoring is achieved; basic physical parameters of a soil body are updated in real time based on data collected by a sensor, and the slope stability safety coefficient is predicted through a semi-supervised learning model; safety early warning is triggered in a grading mode according to prediction results, model prediction values and measured values are recorded and analyzed, and the system evaluates the long-term stability and applicability of the model; through multi-source data fusion and intelligent analysis, theoretical support and technical guarantee are provided for safety monitoring and early warning of the loess slope.

The invention provides an intelligent debris flow early warning method and system based on a physical model and an algorithm, and belongs to the technical field of geological disaster monitoring, and the method comprises the steps: S1, carrying out an indoor soil physical mechanics test, building a physical model, and carrying out the parameter calibration of the physical model through combining a stability criterion equation of a rainfall infiltration-matrix suction coupling effect; s2, simulating different conditions, and generating and outputting debris flow occurrence process data under different working conditions by the physical model; s3, taking the generation process data and the real-time monitoring data as input, constructing a two-channel input network, and training a correction model to obtain corrected response data; s4, on the basis of an SHAP interpretability framework, constructing a Bayesian probability early warning model driven by multi-source heterogeneous data; and S5, triggering real-time early warning of the early warning platform according to the debris flow real-time occurrence probability of the monitoring point, and constructing a mapping relation between soil deformation and critical parameters through dynamic simulation of a physical model on a soil mechanical behavior.

The invention discloses a method for rapidly predicting and dynamically regulating and controlling the quality of a flow field of a gas compressor under a low Reynolds number. According to the method, firstly, pressure gradient parameters Ks of a blade suction surface laminar flow separation point under different Reynolds numbers are obtained through high-precision performance testing / numerical calculation, and then experience prediction models of the Ks, an incoming flow Reynolds number Re, a separation point momentum thickness Reynolds number Re theta s, a blade surface separation scale and boundary layer development characteristics are sequentially established; and the influence of the low Reynolds number effect on the separation bubble structure and the boundary layer growth rate is quantified, so that the performance degradation degree of the gas compressor under the low Reynolds number can be quickly predicted. Based on the model, parameters such as excitation frequency of the front edge deformation surface of the blade are optimally configured, periodic pressure disturbance waves are induced to be generated, and dynamic regulation and control of large-scale separation flow under the low Reynolds number are achieved. The prediction speed of the performance variation of the gas compressor under the low Reynolds number is increased, and support is provided for aerodynamic design and performance regulation and control of the high-altitude gas compressor.

A marine foundation such as a jacket or a tripod foundation for a wind turbine comprises suction piles that are subjected, in service, to cyclical loading of compression phases and tension phases in alternation. Each pile has a one-way valve that opens and closes autonomously in response to pressure differentials between the internal chamber and the surrounding water. The valve opens during the compression phases to effect fluid communication between an internal chamber of the pile and surrounding water. Water is thereby ejected from within the chamber through the valve. Conversely, during the tension phases, the valve closes and water is admitted into the pile only through soil within a skirt of the pile. Thus, a unidirectional, generally upward flow of water is driven through the soil within the skirt during the compression and tension phases, maximising water flow friction and reducing the risk of liquefaction of the soil.

The invention discloses a practical method for calculating additional settlement of a foundation by considering a'pot cover effect ', and relates to the technical field of geotechnical engineering.The method comprises the steps that the increment of the moisture content and the suction variation of soil bodies with different depths caused by the'pot cover effect' are calculated; unsaturated soil model parameters are constructed through an indoor triaxial test; and with the UH constitutive model of the unsaturated soil as a core, performing foundation settlement calculation based on a layering sum algorithm. According to the method, the suction variation of soil bodies with different depths is calculated, soil property parameters determined by indoor tests are combined, an unsaturated soil UH constitutive model is taken as a core, and a calculation method for the additional settlement of the foundation correctly reflecting the influence of the pot cover effect is established on the basis of a layering sum algorithm; practical calculation of foundation additional settlement caused by the pot cover effect is achieved for the first time.

The application relates to a suction cylinder sinking resistance calculation method and relates to the technical field of suction cylinder foundation construction, which comprises the following steps: calculating the clay content index of a clay-sand mixed soil layer by using a pore pressure static sounding test structure; calculating the upper limit value of the side resistance coefficient of the suction cylinder, the lower limit value of the side resistance coefficient of the suction cylinder, the upper limit value of the end resistance coefficient of the suction cylinder and the lower limit value of the end resistance coefficient of the suction cylinder according to the clay content index; and calculating the first sinking resistance based on the above resistance coefficients and by using a formula. The application establishes a suction cylinder sinking resistance calculation method for the clay-sand mixed soil layer, clearly defines the quantitative relationship between the clay content index of the clay-sand mixed soil layer and the sinking resistance coefficient (including the end resistance coefficient and the side resistance coefficient), solves the problem that the calculation parameters of the suction cylinder sinking resistance in the clay-sand mixed soil layer are not clear in the existing norms, and improves the accuracy of the sinking resistance calculation result.

A subsea foundation exemplified by a monopile or a suction pile comprises an embeddable body that extends along an upright embedment axis. A plurality of fins extend outwardly from the body in directions transverse to the embedment axis. At least some fins of the plurality are at least partially embedded in seabed soil. The plurality of fins is divided into an upper array of upper fins and a lower array of lower fins. The arrays may be spaced apart or overlap along the embedment axis, and may be angularly aligned or angularly offset with respect to each other about that axis.

The invention discloses a slope stability prediction method in heavy rainfall weather, and relates to the technical field of road slopes. The method comprises the following steps: collecting soil characteristic data before and after rainfall in a road slope sub-region, and fitting a water-soil characteristic function and a saturated permeation function through a least square method; the method comprises the following steps: establishing a road slope three-dimensional model by using a laser radar, obtaining soil parameters of each point of the road slope three-dimensional model based on an inverse distance square weighting method, and obtaining simulated initial soil matrix suction and simulated initial unsaturated permeability coefficients; simulating moisture movement through an unsaturated seepage control equation to obtain simulated soil moisture saturation and simulated pore water pressure of each point, screening risk points through a preset threshold value, and generating risk clusters through density clustering; and searching a potential sliding surface in the risk cluster by adopting a particle swarm optimization algorithm, calculating the safety coefficient of the sliding surface in combination with a soil strip method, and quantifying the area of the sliding surface. And fusing the safety coefficient and the area proportion to calculate a slope risk index and divide stability grades.

The invention provides a static sounding-based test device and a static sounding-based test method for researching mounting and upward pulling of a suction bucket, and aims to research mounting and upward pulling processes of the suction bucket. The test device comprises a model box, a sample preparation system, an in-situ test system and a suction bucket installation test system. The model box simulates a marine environment and accommodates sandy soil samples with different relative densities. The sample preparation system consists of a crane and a sand rain device and is responsible for preparing sand; the in-situ testing system comprises a static sounding device, a flat spade side expansion penetration device and a hydraulic device and is used for obtaining in-situ mechanical parameters of the soil body. In addition, the suction bucket installation test system simulates the negative pressure penetration process of the suction bucket foundation and comprises a suction bucket model and a negative pressure adjusting system. According to the test device, CPT and DMT data are collected through in-situ testing, the penetration resistance of the suction bucket foundation is jointly estimated, a scientific basis is provided for design and construction of the suction bucket foundation, and high precision and stability of the test are ensured.

The trestle structure of the underwater suction pile foundation of the subsea pipeline comprises a trestle mechanism, penetration structures are arranged on the two sides of the trestle mechanism, at least one penetration structure is arranged to be a suction pile, and a negative pressure generator is arranged in the suction pile. By means of the trestle structure, pipelines can be fully protected, closed protection and open supporting exist, workers can conveniently conduct various selections, and the trestle structure has the advantages of being short in construction period, low in construction difficulty, wide in application range and the like. The design structure can effectively bear huge horizontal and vertical loads and bending moment. Besides, the suction pile foundation further has multiple remarkable advantages such as investment cost saving, foundation installation period shortening and reutilization, the overall penetration depth can be adjusted by adjusting the internal negative pressure generator, and the suction pile foundation is suitable for various geological units and geological types such as covering sludge, clay, silt and sandy soil.

The invention discloses an intelligent stability control method, system and device for a red soil slope, and relates to the technical field of monitoring control, and the method comprises the steps: S1, constructing a multi-scale hydraulic-mechanical coupling model and a special parameter library for red soil; s2, monitoring and collecting data information in real time; s3, the seepage-deformation coupling behavior of the slope and the shearing strength of unsaturated soil are analyzed; s4, dynamically predicting an air inlet value parameter alpha (t) and slope suction evolution, and updating a safety coefficient; s5, predicting seepage and deformation response of the side slope; s6, correcting the parameters of the special parameter library for the red layer soil, and returning to S2; s7, triggering a dynamic control module according to the safety coefficient; s8, adjusting the control measures according to the safety coefficient; s9, an executing mechanism corresponding to the dynamic control module works according to the adjusted control measures, and the step S2 is executed again; according to the method, the slope stability evaluation precision and the control efficiency are remarkably improved, and an efficient, intelligent and sustainable solution is provided for red soil slope disaster prevention and control.

The invention relates to a test device and method capable of testing mechanical properties of hydrophilic and hydrophobic unsaturated soil, the test device comprises a pressure chamber, the pressure chamber is located at the center position of the whole device, an axial loading system is located below the pressure chamber, and the axial loading system is connected with the pressure chamber through a loading frame; the axial loading system is connected with the information acquisition system; the pneumatic control system is positioned on the side of the pressure chamber and connected with the pressure chamber through a pipeline; the data acquisition system is positioned beside the console or the computer and is connected with the sensor at each unit; the data processing system is connected with the air pressure control system and the back pressure control system, and the data processing system is connected with the axial loading system; the sample is positioned in the center of the pressure chamber; the hydrophobic soil suction control unit and the hydrophilic suction control unit are located at the upper end and the lower end of the sample, make close contact with the sample, ensure uniform pressure transmission and are connected with the air pressure control system through pipelines. According to the invention, the accuracy and wide applicability of the mechanical property test of the unsaturated soil are improved.

The invention discloses a single pile, tripod and suction pile combined fan foundation structure, the single pile, tripod and suction pile combined fan foundation structure comprises a central stand column and a lower support, an inclined strut is connected between the lower support and the central stand column, a connection reinforcing section is arranged between the inclined strut and the central stand column, the lower support is connected to the suction pile, and the lower support is connected to the suction pile. The suction piles are inserted into seabed soil, so that the central stand column is stably arranged on the seabed; steel pipe piles are inserted into the center stand column, one ends of the steel pipe piles are connected with fans, and the ends, away from the fans, of the steel pipe piles are inserted into seabed soil so that the fans can be stably arranged on the sea. According to the single pile, tripod and suction pile combined fan foundation structure, the tripod structure is stably placed on the seabed at the preset position through the lifting appliance, then all the suction piles penetrate into the soil body and reach the designed depth, it is guaranteed that the overall perpendicularity and levelness meet the design requirement, and the construction efficiency is improved. And the steel pipe pile is hoisted to penetrate through the center stand column till the bottom end to be inserted into seabed soil.

The invention provides a self-cleaning method of cleaning equipment and the cleaning equipment. The cleaning equipment comprises a dirt suction assembly and a control device, the dirt suction assembly comprises a sewage tank used for recycling dirt, a dirt suction pipeline communicated with the sewage tank and a suction device acting on the dirt suction pipeline, and the control device can control the suction device to generate negative pressure suction force in the dirt suction pipeline so as to suck the dirt into the sewage tank through the dirt suction pipeline. The self-cleaning method comprises the steps that in response to starting operation of a self-cleaning mode, the self-cleaning mode is executed; and under the condition that the self-cleaning mode indicates that the sewage suction pipeline is self-cleaned, the suction device is controlled to be started and alternately operates at first power and second power smaller than the first power, and cleaning liquid used for cleaning the sewage suction pipeline forms surge in the sewage suction pipeline. According to the self-cleaning method of the cleaning equipment, the dirt suction pipeline of the cleaning equipment can be self-cleaned, the service life of the cleaning equipment is prolonged, and the user satisfaction degree is improved.

The present application relates to a kind of suction bucket foundation multidirectional coupling bearing capacity evaluation method considering associated plastic flow of marine clay.The method is based on the associated flow characteristics of undrained clay plastic material,firstly, the numerical model of static loading of suction bucket foundation in undrained clay is established;Secondly, by displacement probe method, the bearing capacity of foundation under different proportional displacement loading is obtained;Finally, based on the rule of associated plastic flow, the same as the outer normal of bearing capacity envelope surface and displacement increment direction vector is used as the criterion, the bearing capacity envelope surface of suction bucket foundation (i.e. the maximum bearing capacity of foundation under multidirectional coupling load) is determined.Compared with prior art, the present application has the effect of considering the associated plastic flow of undrained clay plastic material, the method has clear physical meaning and is easy to implement, and can solve the problem that the existing model cannot accurately evaluate the bearing capacity envelope surface.

The invention relates to the technical field of ocean energy development, in particular to an underwater suction pile foundation rock-soil spring stiffness analysis method considering the heterogeneous characteristic of sea soil. The method comprises the following steps: S1, establishing a shear modulus depth change model based on a sea soil heterogeneous characteristic, and introducing a rigidity dimensionless parameter to perform regularization processing in consideration of a wall thickness factor of a suction pile apron board; s2, based on a Doherty method, estimating a stiffness dimensionless coefficient group in each direction of the spring through linear interpolation; s3, calculating the dimensionless rigidity values of the springs in all directions based on the rigidity dimensionless coefficient groups in all directions obtained in the S2; and S4, based on the calculation result of S3, converting the dimensionless stiffness value into the actual spring stiffness with dimensions through a dimensionalization formula. By establishing the model of which the shear modulus changes along with the depth, the actual heterogeneity of sea and soil can be reflected more accurately, so that the accuracy of predicting the bearing behavior of the suction pile foundation is improved.

This utility model discloses a device for measuring changes in matrix suction gradient, including a soil tensiometer body; a clay head is fixedly installed at the bottom of the soil tensiometer body, an electronic tensiometer is fixedly installed at the end of the soil tensiometer body away from the clay head, and a water inlet pipe is fixedly installed on one side of the soil tensiometer body, communicating with the soil tensiometer body, with a threaded cap threaded onto the water inlet pipe; this utility model, by fitting two semi-circular chucks onto the soil tensiometer body and fixing the two semi-circular chucks with pins, places the end of the support rod away from the semi-circular chucks on the ground, and inserts the rod into the support rod insertion hole to limit and fix the fixing plate, the cooperation of the support rod and the semi-circular chucks can provide support for the soil tensiometer body, preventing it from tilting due to collisions with external objects, making the device safer when continuously monitoring outdoors, and allowing the clay head at the bottom of the soil tensiometer body to maintain stable contact with the soil.

The invention belongs to the technical field of geotechnical engineering, and particularly discloses a full-automatic high-precision deformable red soil-water characteristic curve measuring system and method. The double-layer pressure chamber of the system is of a double-layer structure, water is filled between the double-layer pressure chamber and the inner layer which is not filled with water, the image recognition measuring device captures deformation characteristics in the sample dehumidification process, and the automatic bubble washing device controls opening and closing of an electromagnetic valve through a computer and efficiently washes bubbles in a pipeline through an air source. Reciprocating type accurate flushing and bubble collection of pipeline bubbles are achieved; the computer is connected with the evaporation compensation device and can accurately collect the evaporation capacity. The method comprises the steps of test preparation, data and image acquisition, bubble scouring, multi-stage suction force application, data processing and SWCC. The device has the advantages of being simple in structure, high in automation degree and accurate in result, especially can measure the volume change of the soil body in the dehumidification process in real time, and provides a highly valuable, efficient and reliable measurement means and technical scheme for the field of unsaturated soil research.

The present invention provides a calculation method for the soil-water characteristic curve of unsaturated soil, which includes: 1) collecting dewetting test data points and fitting them to obtain a continuous "initial dewetting curve"; 2) dividing the "initial dewetting curve" into N intervals equally within the soil suction range, and calculating the water content of each interval taking into account the hysteresis effect; 3) collecting test data points on the "main infiltration curve", fitting them with the calculated value in step 2, and determining the correction parameter k; 4) calculating the "infiltration scanning curve" or "dewetting scanning curve" under any initial state. The calculation results of this method are highly accurate and can effectively meet the engineering precision requirements. Compared with the use of experimental methods to obtain data throughout the process, this calculation method only requires part of the test data to calculate the "infiltration scanning curve" or "dewetting scanning curve" starting from any initial soil suction, which is relatively low in cost.

The invention discloses a device and method for measuring a relative permeability curve of a soil body, the device comprises a cutting ring, a sleeve, a stainless steel electrode, a water delivery module, a vacuum drying system and a resistivity acquisition control module, the resistivity is monitored in real time through an electrode hole, and a sealing structure ensures that the system is stable. The method is based on an unsaturated seepage and electrical conduction theory and comprises the following steps: firstly drying a soil sample, then injecting water, collecting resistivity data, inverting a soil-water characteristic curve through a resistivity-moisture content-matric suction relation model, calculating a permeability coefficient in combination with a Darcy law, and fitting to obtain a permeability curve. The device and the method overcome the limitation that a traditional experiment is tedious in operation and prone to interference, have the advantages of being portable, easy and convenient to operate, high in automation degree, suitable for field measurement and the like, and can achieve efficient and accurate measurement of the permeability characteristic of the unsaturated soil body.

The present invention discloses a model test system for studying critical conditions for instability of a vegetated slope under rainfall, wherein a vegetated slope model is provided in a centrifugal environment double-layer seepage model box; a graded rainfall feedback simulation system simulates the requirements of specific rainfall intensity and duration, and induces changes in the internal moisture field conditions of the vegetated slope model; an artificial root strain analysis system simulates the physical soil consolidation effect of the root system on the slope surface and the regulating effect of matrix suction; a high-speed camera system for slope surface cracks records the entire rainwater infiltration and slope surface scouring of the test slope, and clearly captures the entire process of development, extension and penetration of slope surface cracks; a rock and soil moisture content monitoring system realizes the response of the slope moisture field in real time under different rainfall and artificial root working conditions. The present invention is used to carry out model tests for studying critical conditions for instability of a vegetated slope under rainfall conditions, and provides an effective testing means for evaluating the influence of vegetation on slope stability under rainfall conditions.

This invention relates to the field of slope stability analysis technology, and in particular to a method, device, and storage medium for measuring the stability of unsaturated soil slopes. The unsaturated soil slope stability measurement method of this invention is based on the soil-water characteristic curve of unsaturated soil and uses the finite element method to solve the Richards equation to obtain the transient seepage field distribution of the unsaturated soil slope. This method is more consistent with reality than the seepage field assumed by empirical formulas in the past. While the SMP criterion proposed by Songgang-Zhongjing considers the influence of intermediate principal stress, the SMP criterion is only suitable for cohesive soil failure criteria. Therefore, this invention modifies the SMP criterion by considering the influence of cohesion, friction angle, and matrix suction, making it applicable to unsaturated cohesive soil slopes. Based on the calculation of the slope's self-weight stress, and using a modified SMP material model, we conduct stability analysis of unsaturated soil slopes using the strength reduction method, considering the influence of the intermediate principal stress of the soil, resulting in more reasonable results.

The invention discloses a rapid soil-water characteristic curve testing method based on water-gas two-phase flow, which comprises the following steps: S1, constructing a rapid soil-water characteristic curve testing system which comprises a pressure control system, an automatic control and data acquisition system and a soil sample device; s2, an unsaturated seepage test is carried out, and the change process of pore pressure and overflow water quantity along with time in the seepage process of the soil sample is obtained in real time; s3, on the basis of the test data, an inversion analysis method combining water-gas two-phase flow numerical simulation and a grid search method is adopted, and the optimal parameter value of the soil-water characteristic curve of the soil body is obtained through calculation; according to the invention, the soil-water characteristic curve of the soil sample can be rapidly obtained, and the test result can comprehensively reflect the water-gas coupling characteristic of the unsaturated soil in a wide matrix suction range and is closer to the macroscopic soil-water characteristic of the soil body.

The present disclosure provides an apparatus and a system of removing sand to prevent sand encroachment. In an embodiment, the apparatus can include a main arm (101), a movable arm (102) connected to one end of the main arm (101), and a plurality of flexible robotic arms (103) connected to the movable arm (102). The plurality of flexible robotic arms (103) can include a suction end with vacuum means for suctioning out grains of sand from a location.

The invention discloses a drilling and fixing integrated drilling device and method for a deep sea natural gas hydrate exploitation system. The drilling device comprises a hollow drill rod, a plurality of continuous pipe separation units and a hollow drill bit which are fixedly connected from top to bottom in the axial direction, and according to the method, the multi-well guiding suction anchor, the rope soil taking equipment, the drilling device and the seabed drilling machine are lowered to a seabed to be positioned and leveled through a small and medium-sized workboat and are fixedly connected with the multi-well guiding suction anchor; the seabed drilling machine controls the drilling device to drill along the multi-well guide suction anchor, and the rope soil taking equipment takes soil; and the pipe is replaced until the target depth is drilled, the drilling device conducts self well cementation and well completion through the self-expansion packer and the pre-filled gravel screen pipe, and the drilling device is completed after equipment is recycled. The device has continuous and integrated operation capacity of well drilling, soil taking, well cementation and well completion, the cost is effectively reduced, the efficiency is remarkably improved, rapid construction, convenient well cementation and economic well completion of a deep sea hydrate mining system are achieved, and a new thought and method are provided for safe and efficient mining of deep sea hydrates.

The invention provides a frost heaving control method based on cold source temperature dynamic adjustment. The frost heaving control method comprises the following steps that 1, the influence of temperature evolution on driving force is analyzed; 1.1, the migration driving force of the thin film water is obtained; step 1.2, influence of temperature rise on migration driving force; step 2, analyzing freeze-thaw hysteresis of segregated ice; step 2.1, setting formation conditions of segregation ice; step 2.2, determining melting conditions of segregation ice; step 3, analyzing a water insulation mechanism of segregated ice; step 3.1, calculating a conversion relation between pressure-suction stress; step 3.2, influence of temperature rise on surface adsorption force; 4, discovering a segregation expansion control mechanism; step 4.1, influence of temperature evolution of a warm end of segregated ice on frost heaving; and step 4.2, a frost heaving control model of segregated ice is established. In order to solve the problem that frost heaving diseases are difficult to prevent and control in the stratum freezing process, frost heaving control mechanism research on frozen soil is carried out.

The invention provides an automatic pressurization type test device for inhibiting rainfall from infiltrating into a side slope through a capillary barrier layer. The automatic pressurization type test device comprises a model tank, a protection side slope, the capillary barrier layer, a rainfall system, a soil matrix suction monitoring system and an automatic pressurization system. The model groove comprises a model cavity and a wedge body arranged at the bottom of the model cavity, the bottom of the model cavity is filled with cohesive soil to form a protective slope, the protective slope is filled with various kinds of soil to form a capillary barrier layer, and the capillary barrier layer sequentially comprises a coarse grain layer, a transition layer and a fine grain layer from bottom to top; the automatic pressurization system is used for injecting set air pressure into the coarse grain layer when the soil matrix suction value, monitored by the soil matrix suction monitoring system, in the fine grain layer is smaller than a critical value, so that certain air pressure is formed in the coarse grain layer, and it is restrained that rainfall breaks through a fine grain layer / transition layer interface; rainwater is moved and discharged from the fine particle layer above the fine particle layer / transition layer interface. According to the invention, the coarse grain layer can be automatically pressurized, so that the capillary barrier layer can completely block rainfall infiltration.

The present invention discloses a shear wave velocity calculation method based on the matrix suction of unsaturated fine-grained soil. The method obtains the soil-water characteristic curve of the sample by carrying out a pressure plate instrument test on the unsaturated fine-grained soil sample; then, the test data is fitted based on the VG model to obtain the matrix suction under different saturations; then, the shear wave velocity test of the sample in the continuous dehumidification process under different saturations is carried out based on the bending element method to obtain the evolution law of the shear wave velocity with the saturation; finally, according to the empirical model, a prediction model of the shear wave velocity based on the matrix suction of the unsaturated fine-grained soil is proposed to realize the calculation of the shear wave velocity of the sample in the dehumidification process through the matrix suction. The method avoids the shortcomings of the existing equipment such as complex operation and high cost. The model is applicable to fine-grained soils such as clay and silt, and is helpful to characterize the evolution law of the shear wave velocity of the unsaturated soil with the matrix suction in a wide suction range, which is of great significance for analyzing the change mechanism of the shear wave velocity in the dehumidification process of the unsaturated soil.

The invention provides a system reliability and sensitivity analysis method for double piles in spatial variation expansive soil, and belongs to the technical field of pile foundation engineering reliability analysis. The method comprises the following steps: establishing a double-pile foundation model and a soil property parameter random field model; element reliability indexes and element sensitivity indexes of the three failure modes of the double piles are calculated; and calculating a double-pile system reliability index and a system sensitivity index. According to the method, three failure modes of double-pile pulling resistance or compression resistance failure and double-pile settlement differential failure under complex conditions are given, a system reliability and sensitivity analysis method of the double-pile foundation is established, and the influence of expansive soil space variability, double-pile interaction, pile-soil interface nonlinear relation and matric suction change is considered. The method has high calculation precision and low calculation cost, and is beneficial for rock and soil practitioners to carry out safer reliability evaluation and design on the double-pile foundation under complex geological conditions.

The present invention discloses a method for calculating the effective stress of unsaturated soil based on fluid dynamics theory. Based on the fluid dynamics theory, the present invention analyzes the effective stress of unsaturated soil based on thermodynamics theory, introduces concepts such as chemical potential and free energy, and describes the effective stress of unsaturated soil from the perspective of physical and chemical principles based on the fluid dynamics theory. Compared with the commonly used method of calculating the effective stress coefficient as saturation, the present invention reveals the intrinsic connection between the water-holding characteristics of unsaturated soil and the effective stress coefficient, and indirectly reflects the influence of the microscopic pore structure on the matrix suction in the expression of effective stress. If only the correlation between matrix suction and saturation is considered, the effective stress coefficient will be restored to the value of saturation. In addition, the present invention can take into account influencing factors such as porosity ratio to more reasonably predict the effective stress and strength index of unsaturated soil, and provide theoretical support for unsaturated soil related engineering applications.