Permeability distribution measurement method of freeze-thaw soft clay based on CPTU

Abstract

The present invention relates to a CPTU-based permeability coefficient distribution measurement method for frozen-thaw soft clay. The method explores the permeability coefficient changes at different locations before and after the freezing of the soft clay layer. A test box is built and covered with insulation material. A model soil system and a freezing system are designed according to an engineering case. A test soil temperature monitoring system is designed based on the optical fiber temperature measurement principle. A permeability coefficient acquisition device for different areas of the test soil is designed based on the micro-pore pressure static penetration test (CPTU) method. The relevant data acquisition areas and acquisition points are designed according to engineering requirements and the actual test temperature field. Compared with the prior art, the present application can more accurately obtain the permeability change distribution of different areas of thixotropic soft clay before and after freezing and thawing, reducing the influence of manual sampling disturbance in the original relevant permeability coefficient acquisition process. It provides a reference for the permeability coefficient change value of the area after the actual freezing method construction, and provides a basis for judging areas prone to leakage.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering, and in particular to a method for measuring the permeability distribution of freeze-thaw soft clay using a micro piezoresistance penetration test (CPTU). Background Art

[0002] As urban underground infrastructure construction progresses, artificial ground freezing (ASF) has been widely adopted as a green construction method for underground projects such as subway sidewalks and cross-river tunnels in areas with weak soft clay strata, such as Shanghai. However, as the number of projects increases, problems such as leakage in some areas and uneven settlement after the ground completely melts have emerged.

[0003] The soil permeability coefficient is a parameter that directly reflects the permeability of the soil and is of great significance for studying ground settlement and leakage problems caused by freezing. Therefore, accurately obtaining the soil permeability coefficient in the study area is the key to solving the problems caused by freezing.

[0004] In China, the primary method for determining soil permeability is to perform an indoor permeability test using a ring cutter sample after the test. However, for easily disturbed soft clay, which becomes fragile after freeze-thaw, this method inevitably causes disturbance during sampling, fails to accurately simulate actual field conditions, and is time-consuming and expensive.

[0005] Therefore, it is necessary to propose a soil permeability distribution measurement scheme for freeze-thaw soft clay. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a CPTU-based method for measuring the permeability distribution of freeze-thaw soft clay.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A CPTU-based method for measuring permeability distribution of freeze-thaw soft clay includes:

[0009] Build a test box and cover it with insulation material;

[0010] Preset the position of the freeze curtain boundary in the test chamber;

[0011] A freezing tube is provided in the test chamber, the freezing tube being arranged in the center of the test chamber in a plane parallel to the side wall of the test chamber. A soil sample is placed in the test chamber, the soil sample on the first side of the freezing tube is used for temperature measurement, and the soil sample on the second side of the freezing tube is used for penetration. A transverse temperature measurement optical fiber group I is buried in the soil sample on the first side of the freezing tube according to a pre-set freezing curtain boundary, and a longitudinal temperature measurement optical fiber group II is respectively arranged on multiple planes selected along the freezing front advancing direction on the first side of the freezing tube;

[0012] Connect the freezing pipe through the circulation pump to start the freezing operation, and use the transverse temperature measurement optical fiber group I to detect whether the freezing curtain boundary of the soil has reached the preset freezing curtain boundary. If it has reached, the freezing operation is stopped, otherwise, this step is repeated;

[0013] The temperature zones of the soil are divided based on the measurement data of the longitudinal temperature measurement optical fiber group II in multiple planes, and the locations of the various penetration points are determined;

[0014] After the soil returns to room temperature, the probes of the micro-pore pressure static penetration system are distributed and extended to various penetration points to obtain the pore water pressure, probe penetration velocity and cone resistance.

[0015] The permeability coefficient of each penetration point is calculated based on the pore water pressure, probe penetration velocity and cone resistance. Furthermore, the permeability coefficient is calculated as follows:

[0016] πa 2 U=S'·K·i

[0017] Where a is the probe radius, U is the probe penetration velocity, S' is the probe water flow surface area, K is the soil permeability coefficient, and a circumscribed sphere is formed to wrap around the probe during the probing process. i is the hydraulic gradient at the surface of the sphere.

[0018] Furthermore, the water flow surface area of the probe is:

[0019]

[0020] Where α is the probe cone angle.

[0021] Furthermore, the micro-pore pressure static penetration system includes a first movable frame, a first driving mechanism, a second movable seat, a second driving mechanism, a penetration mechanism, a probe rod and a probe;

[0022] Two ends of the first movable frame are connected to two parallel side walls of the test box, and the first driving mechanism is connected to the first movable frame for driving the first movable frame to slide along the two parallel side walls of the test box;

[0023] The second movable seat is installed on the first movable frame, and the second driving mechanism is connected to the second movable seat and is used to drive the second movable seat to slide on the first movable frame, and the running tracks of the first movable frame and the second movable seat are perpendicular;

[0024] The penetration mechanism is arranged on the second movable seat, one end of the probe rod is connected to the penetration mechanism, and the other end is connected to the probe.

[0025] Furthermore, a rack structure is provided on the surface of the probe rod.

[0026] Furthermore, the micro-pore pressure static penetration system also includes a controller, which is connected to the first driving mechanism, the second driving mechanism, the penetration mechanism and the sensor on the probe.

[0027] Furthermore, the transverse temperature measurement optical fiber group I is arranged on a preset freezing curtain boundary plane, and includes three temperature measurement optical fibers with different depths.

[0028] Furthermore, three groups of longitudinal temperature measurement optical fiber groups II are provided in each plane, each group of longitudinal temperature measurement optical fiber group II includes three temperature measurement optical fibers with the same depth as the transverse temperature measurement optical fiber group I, and the three groups of longitudinal temperature measurement optical fiber groups II are sequentially arranged at different positions on the plane.

[0029] Furthermore, the temperature measuring optical fiber is connected to a thermometer.

[0030] Furthermore, it also includes a master control terminal, which is connected to the temperature meter, the circulation pump and the micro-pore pressure static penetration system.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The permeability coefficient of soft clay after freeze-thaw is measured by micro-pore pressure penetration test (CPTU), which can avoid the large disturbance of sampling to the fragile soft soil structure after freeze-thaw, and the disturbance to the original soil is small. The obtained permeability coefficient is highly accurate, and the in-situ permeability coefficient distribution can be measured, providing a reference basis for the precise positioning of grouting after freezing method.

[0033] (2) CPTU determination of soil permeability coefficient takes less time, has a shorter test cycle, and is less expensive than traditional methods.

[0034] (3) The temperature field in the soil is symmetrically distributed, and the temperature measurement area and the probe area are symmetrically distributed, which avoids the influence of temperature monitoring on the probe area, further reduces disturbance, and improves measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a connection diagram of the test chamber and related equipment;

[0036] Figure 2 This is a schematic diagram of the temperature zone division of the test chamber;

[0037] Figure 3 This is a schematic diagram of the penetration point;

[0038] Figure numerals: 1. Penetration mechanism, 2. Second movable seat, 3. First movable frame, 4. Probe, 5. Freezing tube, 6. Circulation pump, 7. Test chamber, 8. Chamber base, 9. Horizontal temperature measurement optical fiber group I (freezing curtain boundary), 10. Longitudinal temperature measurement optical fiber group II (freezing area monitoring), 11. Thermometer, 12. Master control terminal. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operating process. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and the protection scope of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0040] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The dimensions and thicknesses of each component shown in the drawings are arbitrary and are not limited by the present invention. To enhance clarity and illustrate the coordination between components, some components in the drawings are scaled, and the distances between components are increased or decreased.

[0041] "One embodiment" or "embodiment" referred to herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. In the description of the present invention, it should be understood that the terms "first", "second" and "third" in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units that are inherent to these processes, methods, products or devices.

[0042] In the description of the embodiments of the present invention, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the application is conventionally placed when in use, or are the orientation or position relationship conventionally understood by those skilled in the art. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0043] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0044] Example 1:

[0045] A method for measuring the permeability distribution of frozen-thaw soft clay based on micro piezocone penetration test (CPTU) includes:

[0046] (1) Build a test box 7 and cover the test box 7 with insulation material. The test box 7 is made of steel, the lower part is sealed and provided with a box base 8, the box base 8 is filled with insulation material, and the side walls of the test box 7 are covered with insulation material to isolate the influence of external temperature on the soil inside the test box 7;

[0047] (2) Determine the scale of the model based on the actual engineering case and the size of the test chamber 7, and clarify the position of the freezing curtain boundary in the test chamber 7. The freezing curtain boundary here is a pre-set rough position and is not the actual freezing curtain boundary in subsequent experiments;

[0048] The freezing curtain boundary is the boundary between the freezing zone near the freezing pipe 5 and the phase change zone far from the freezing pipe 5. According to engineering specifications, the freezing zone temperature is lower than -10°C, and the phase change zone temperature is between -10°C and 0°C.

[0049] (3) Figure 1 As shown, a freezing tube 5 is provided in a test box 7. The freezing tube 5 is arranged in the center of the test box 7 in a plane parallel to the side wall of the test box 7. A soil sample is placed in the test box 7. The soil sample on the first side of the freezing tube 5 is used for temperature measurement, and the soil sample on the second side of the freezing tube 5 is used for penetration. A transverse temperature measurement optical fiber group I 9 is buried in the soil sample on the first side of the freezing tube 5 according to the preset freezing curtain boundary. A plurality of planes are selected on the first side of the freezing tube 5 along the advancing direction of the freezing front and longitudinal temperature measurement optical fiber groups II 10 are respectively provided.

[0050] Based on an actual engineering case study, the fourth layer of silty clay in Shanghai was used. A slurry method was used to prepare a saturated reshaped sample, which was then filled into a test chamber 7 in layers. Temperature-sensing optical fibers were then arranged in layers. A thermometer 11 connected the temperature-sensing optical fibers to a master control terminal 12, acquiring measurement data from the optical fibers and transmitting it to the master control terminal 12 for initial temperature verification. After filling, the soil sample was pre-loaded using a pre-loading method. After pre-loading, the sample reached stable settlement. Once settlement met the required value, the next step was performed.

[0051] The de-loop freezing pipe 5 is located at the bottom center of the test box 7, welded and runs through the test box 7, so as to achieve symmetrical distribution of the internal temperature field of the test box 7 along the freezing pipe 5 during the freezing process. This arrangement can make the freezing pipe 5 a planar freezing source, and the temperature field on both sides of the freezing pipe is evenly distributed. Ideally, the temperature is the same at the same depth, and the temperature is the same at the same horizontal distance from the freezing pipe 5.

[0052] According to the temperature distribution during the test, it can be divided into three main areas: frozen area, phase change area and unfrozen area (such as Figure 2 In order to be as close as possible to the freezing situation of an actual engineering case, a preset freezing curtain boundary is determined according to the actual engineering case, and the transverse temperature measurement optical fiber group I 9 is set on the preset freezing curtain boundary plane. It includes three temperature measurement optical fibers at different depths, which are mainly used to determine whether the actual freezing curtain boundary during the freezing process reaches the preset freezing curtain boundary. Therefore, it is only necessary to set temperature measurement optical fibers at different depths on the preset freezing curtain boundary plane.

[0053] In order to clearly define the temperature distribution during the test, three groups of longitudinal temperature measurement optical fiber groups II10 are set in each plane along the direction of the freezing front. Each group of longitudinal temperature measurement optical fiber group II10 includes three temperature measurement optical fibers with the same depth as the transverse temperature measurement optical fiber group I9. The three groups of longitudinal temperature measurement optical fiber groups II10 are sequentially arranged at different positions on the plane. In this way, multiple groups of longitudinal temperature measurement optical fiber groups II10 arranged at multiple points can fully measure the temperature distribution of the soil and obtain the temperature field conditions inside the soil. Ideally, the boundary between the frozen zone, phase change zone, and unfrozen zone is a straight line. However, in actual tests, since the side walls of the test chamber 7 cannot achieve absolute insulation, the external ambient temperature will affect the boundary between the frozen zone, phase change zone, and unfrozen zone, causing the boundary to have an arc. Therefore, each group of transverse temperature measurement optical fiber group I9 can be fine-tuned, and the three groups of longitudinal temperature measurement optical fiber groups II10 on the same plane can be in the same arc surface. Similarly, when selecting the probing point on the second side of the freezing pipe 5, a slight arc can also be set, such as Figure 3 shown.

[0054] Assemble the micro-pore pressure static penetration system. Guide rails are set on the upper part of the two parallel side walls of the test box 7. The two ends of the first mobile frame 3 are respectively connected to the guide rails on the upper part of the two side walls, and the first mobile frame 3 is driven by the first driving mechanism to move along the guide rails; the second mobile seat 2 is installed on the first mobile frame 3, and the second driving mechanism drives the second mobile seat 2 to slide on the first mobile frame 3, and the first mobile frame 3 and the second mobile seat 2 are perpendicular to the running track; the penetration mechanism 1 is set on the second mobile seat 2, and the first mobile frame 3 and the second mobile seat 2 can realize the horizontal and vertical movement of the penetration mechanism 1. One end of the probe rod is connected to the penetration mechanism 1, and the other end is connected to the probe 4. The penetration mechanism 1 can drive the probe rod and the probe 4 on it to extend into different depths of the soil at different speeds, and extend the probe 4 to various penetration points of the soil sample on the second side of the freezing pipe 5 for measurement. The probe rod has a rack structure on the surface, and the probe 4 is a conical probe 4. The probe 4 is equipped with sensors for measuring parameters such as the cone head resistance and the pore water pressure behind the cone head. The controller connects the first drive mechanism, the second drive mechanism, and the penetration mechanism 1, and the master control terminal 12 realizes the lateral displacement, longitudinal displacement and penetration depth of the probe 4 through the controller. The controller connects to the sensor in the probe 4, obtains the measurement data of the sensor and sends it to the master control terminal 12.

[0055] Perform initial position calibration on the first movable frame 3, the second movable seat 2 and the penetration mechanism 1 of the micro-pore pressure static penetration system. After calibration, install the penetration rod and the penetration probe 4 to check whether the penetration process is normal, and check the penetration rate and penetration position control.

[0056] The master control terminal 12 is connected to the temperature meter 11, the circulation pump 6 and the micro-pore pressure static penetration system; the test temperature field changes can be fed back in real time through the temperature meter 11, and the penetration position and penetration process can be automatically operated by the controller.

[0057] (4) The circulating pump 6 is connected to the freezing pipe 5 to start the freezing operation. The horizontal temperature measuring optical fiber group I 9 is used to detect whether the freezing curtain boundary of the soil body has reached the preset freezing curtain boundary. If it has reached the preset freezing curtain boundary, the freezing operation is stopped. Otherwise, this step is repeated.

[0058] Connect the freezing pipe 5 to the circulating pump 6 and check the freezing liquid circulation to see if there are any leaks or poor freezing liquid circulation. Ensure that each freezing pipe 5 can maintain the freezing liquid circulation. The constant temperature circulating pump 6 is connected to the freezing pipe 5 to provide refrigeration for the freezing process and ensure the required temperature difference between the refrigerant and the refrigerant circuit.

[0059] Circulation pump 6 is turned on to lower the freezing liquid temperature before circulating the freezing liquid. During the test, temperature data is collected and a temperature field distribution diagram is plotted. Circulation pump 6 is stopped after transverse temperature measurement fiber group I 9 (freezing curtain boundary) reaches the preset temperature. At this point, the actual soil freezing conditions are considered consistent with those in the actual engineering case, completing the soil freezing simulation for the actual engineering case.

[0060] (5) The temperature zone of the soil is divided according to the measurement data of the longitudinal temperature measuring optical fiber group II10 in multiple planes, and the locations of each penetration point are determined; the test personnel can determine the final location of the pore pressure static penetration test based on the obtained temperature field distribution, such as Figure 3 shown.

[0061] (6) After the soil returns to room temperature, the probe 4 of the micro-pore pressure static penetration system is distributed and extended to each penetration point. When the probe 4 penetrates the specified position, the pore water pressure change is measured. After penetrating to the specified depth, the excess pore water pressure dissipation process is monitored. Finally, the obtained data are summarized and recorded to obtain data such as pore water pressure, probe 4 penetration speed, and cone resistance;

[0062] (7) The permeability coefficient of each probe point is calculated based on the pore water pressure, the penetration velocity of probe 4 and the cone resistance.

[0063] According to the principle of pore pressure static penetration, during the penetration process, the cone tip forms a circumscribed sphere that just covers the cone tip. The surface area S' of the water flow at the cone tip is a fraction of the surface area S of the circumscribed sphere. The surface area S' of the sphere is related to the cone tip diameter a and the cone tip angle α. Since the volume penetration velocity is equal to the spherical radial flow velocity, we can get:

[0064] πa 2 U=S'·K·i

[0065]

[0066] Where a is the radius of the pore pressure static penetration test probe 4, α represents the cone angle of the probe 4, U is the penetration velocity of the probe 4, S' is the water flow surface area of the cone head, K is the soil permeability coefficient, and i is the hydraulic gradient at the sphere surface, which can be determined by combining the pore water pressure ratio and cone tip resistance obtained from CPTU data.

[0067] The present invention provides a CPTU-based permeability coefficient distribution measurement method for frozen-thaw soft clay. The method explores the permeability coefficient changes at different locations before and after the freezing of the soft clay layer. A test box is built and covered with insulation material. A model soil system and a freezing system are designed according to an engineering case. A test soil temperature monitoring system is designed based on the optical fiber temperature measurement principle. A permeability coefficient acquisition device for different points in the test soil is designed based on the micro-pore pressure static penetration test (CPTU) method. The relevant data acquisition areas and acquisition points are divided and designed according to engineering requirements and the actual test temperature field. The soil permeability coefficient is calculated using the measurement data of the micro-pore pressure static penetration test system. Compared with the prior art, the present application can more accurately obtain the permeability change distribution of different areas of thixotropic soft clay before and after freezing and thawing, reducing the influence of manual sampling disturbance in the original relevant permeability coefficient acquisition process. It provides a reference for the change value of the regional permeability coefficient after the actual freezing method construction and provides a basis for judging the areas prone to leakage.

[0068] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU, characterized in that: include: Build a test box and cover it with insulation material; Preset the position of the freeze curtain boundary in the test chamber; A freezing tube is provided in the test chamber, the freezing tube being arranged in the center of the test chamber in a plane parallel to the side wall of the test chamber. A soil sample is placed in the test chamber, the soil sample on the first side of the freezing tube is used for temperature measurement, and the soil sample on the second side of the freezing tube is used for penetration. A transverse temperature measurement optical fiber group I is buried in the soil sample on the first side of the freezing tube according to a pre-set freezing curtain boundary, and a longitudinal temperature measurement optical fiber group II is respectively arranged on multiple planes selected along the freezing front advancing direction on the first side of the freezing tube; Connect the freezing pipe through the circulation pump to start the freezing operation, and use the transverse temperature measurement optical fiber group I to detect whether the freezing curtain boundary of the soil has reached the preset freezing curtain boundary. If it has reached, the freezing operation is stopped, otherwise, this step is repeated; The soil temperature zones are divided based on the measurement data of the longitudinal temperature measurement optical fiber group II in multiple planes, and the various penetration points are determined; the temperature zones include frozen zones, phase change zones, and unfrozen zones; the penetration points are distributed in each temperature zone; the frozen curtain is the boundary between the frozen zone and the phase change zone; After the soil returns to room temperature, the probes of the micro-pore pressure static penetration system are distributed and extended to various penetration points to obtain the pore water pressure, probe penetration velocity and cone resistance. The permeability coefficient of each penetration point is calculated based on the pore water pressure, probe penetration velocity and cone resistance.

2. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 1, characterized in that: The calculation formula of the permeability coefficient is: in is the probe radius, U is the probe penetration velocity, S' is the water flow surface area of the probe, K is the soil permeability coefficient. During the penetration process, a circumscribed sphere is formed that wraps around the probe. is the hydraulic gradient at the surface of the sphere.

3. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 1, characterized in that: The water flow surface area of the probe is: in, Indicates the probe cone angle, S is the surface area of the sphere circumscribed by the cone head.

4. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 1, characterized in that: The micro-pore pressure static penetration system includes a first moving frame, a first driving mechanism, a second moving seat, a second driving mechanism, a penetration mechanism, a probe rod and a probe; Two ends of the first movable frame are connected to two parallel side walls of the test box, and the first driving mechanism is connected to the first movable frame for driving the first movable frame to slide along the two parallel side walls of the test box; The second movable seat is installed on the first movable frame, and the second driving mechanism is connected to the second movable seat and is used to drive the second movable seat to slide on the first movable frame, and the running tracks of the first movable frame and the second movable seat are perpendicular; The penetration mechanism is arranged on the second movable seat, one end of the probe rod is connected to the penetration mechanism, and the other end is connected to the probe.

5. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 4, characterized in that: A rack structure is provided on the surface of the probe rod.

6. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 4, characterized in that: The micro-pore pressure static penetration system further includes a controller, which is connected to the first driving mechanism, the second driving mechanism, the penetration mechanism and the sensor on the probe.

7. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 1, characterized in that: The transverse temperature measurement optical fiber group I is arranged on a preset freezing curtain boundary plane and includes three temperature measurement optical fibers of different depths.

8. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 1, characterized in that: Three groups of longitudinal temperature measurement optical fiber groups II are provided in each plane. Each group of longitudinal temperature measurement optical fiber group II includes three temperature measurement optical fibers with the same depth as the transverse temperature measurement optical fiber group I. The three groups of longitudinal temperature measurement optical fiber groups II are sequentially arranged at different positions on the plane.

9. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 7 or 8, characterized in that: The temperature measuring optical fiber is connected to a thermometer.

10. The method for measuring the permeability distribution of freeze-thaw soft clay based on CPTU according to claim 9, characterized in that: It also includes a master control terminal, which is connected to the temperature measuring instrument, the circulation pump and the micro-pore pressure static penetration system.

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