In situ planetary thermal conductivity measurements are typically made using a long needle-like probe, which measures effective thermal conductivity in the probe’s radial (horizontal) direction. The desired effective vertical thermal conductivity for heat flow calculations is assumed to be the same as the measured effective horizontal thermal conductivity. However, it is known that effective thermal conductivity increases with increasing compressive pressure on granular beds and the horizontal stress in a granular bed under gravity is related to the vertical stress through Jaky’s at rest earth pressure coefficient. The objectives of this study were to examine the validity of the isotropic property assumption and to develop a fundamental understanding of the effective thermal conductivity of a dry, noncohesive granular bed under uniaxial compression. A model was developed to predict the increase in effective vertical and horizontal thermal conductivity with increasing compressive vertical applied pressure. An experiment was developed to simultaneously measure the effective vertical and horizontal thermal conductivities of particle beds with needle probes. Measurements were made as compressive vertical pressure was increased to show the relationship between increasing pressure and effective vertical and horizontal thermal conductivity. The results of this experiment showed quantitatively the conductivity anisotropy for two different materials and validated the developed model. This model can be used to predict the anisotropic effective thermal conductivity of granular materials under uniaxial compressive pressures, and evaluate the uncertainties in lunar heat flow measurements.

Compressive pressure dependent anisotropic effective thermal conductivity of granular beds

The invention discloses an undisturbed soil sample expansion force testing device capable of controlling the saturation. The device comprises a base supporting system, wherein a lower disc is fixed on the base supporting system, a cutting ring base and a cutting ring are arranged on the lower disc, and the upper part of the cutting ring base is provided with an upper cover; a central circular groove and an annular groove are formed on the lower disc, a soil pressure sensor is arranged in the central circular groove, an annular water penetration plate is arranged in the annular groove, water-immersion circular grooves are formed on the annular water penetration plate, water-permeable stones are uniformly placed in the water-immersion circular grooves, and the bottom of the annular groove is connected with an external water injection system through a pipeline; a soil sample is placed between the lower disc and the cutting ring, and a water-permeable plate base which is provided with a water-permeable plate and water-permeable holes is arranged on the top of the soil sample; and a plunger, overflow equipment and vacuum extraction equipment are arranged on the upper cover. The device effectively solves the problems that testing devices for an expansion back pressure method, a pressurization expansion method and a balance pressurization method have relatively large disturbance on soil sample structures, cannot effectively control strict saturation states and are relatively long in testing time consumption.

Undisturbed soil sample expansion force testing device capable of controlling saturation

The invention relates to the technical field of preparation of triaxial experiment samples in rock mechanics and discloses a triaxial sample preparation device for low-liquid limit silty soil and a sample preparation method. The device comprises a sample tube, a smoothening device, a vibrator and a loading device. The method comprises the following steps: sleeving a rubber diaphragm in a split cavity; gradually pouring soil sample; controlling the initial dry density through the smoothening device and the vibrator; filling carbon dioxide and air-free water from a base until saturation; and carrying out sample consolidation process according to a secondary dry density. According to the invention, the problem of producing uniform silty soil sample is solved, the split cavity integrates the functions of positioning and sealing so as to improve the dimensional precision and the sealing effect of the sample; a rubber-steel combined vibrating head is adopted to improve the vibration and densification effect; and the matching with a current triaxial apparatus is realized, which reduces the equipment investment; and through the two-stage control of the initial dry density and the secondary dry density, the density of the sample can be optionally appointed within a certain range.

Triaxial sample preparation device for low-liquid limit silty soil and sample preparation method

The invention discloses a method and a device for preparing a silty soil triaxial-test test sample. The method comprises the following steps: adding distilled water into silty soil and stirring to enable soil samples to be in a flow plastic state, namely slurry; precipitating the slurry in a split round die under the action of self weight; applying dead loads to the upper part of the test sample, removing the dead loads at the upper part of the test sample and enabling the test sample to be further solidified by adopting a vacuum negative pressure of minus 40 kPa, wherein in the process of applying the dead loads, to guarantee that the slurry does not overflow, the loads are slowly and gradually loaded and a next-stage load is applied after the soil samples complete solidification and drainage under a current load; and finally, removing the negative pressure and the split round die and completing preparation of the test sample, so that triaxial test equipment can be assembled to carry out static triaxial or dynamic triaxial test. The method and the device are simple to operate; the technical method is easy to master; equipment required for preparing the test sample is very simple; required test sample preparation cost is low; uniformity inside the soil samples is very good; reproduction degree between the soil samples is high; a microstructure of a soil layer in the nature can be reproduced to a higher degree; the soil samples do not need to be cut; disturbance is reduced; and the test result has high credibility.

Method and device for preparing silty soil triaxial-test test sample

The invention discloses a test method of mechanical properties of a soil-structure contact surface. The test method comprises the following steps of: 1) preparing a sample; 2) applying confining pressure; 3) saturating cyclic soil samples; 4) dewatering the cyclic soil samples; 5) circularly saturating and dewatering the cyclic soil samples; 6) applying a static load or dynamic load onto the bottom end or top end of a cylindrical structure sample; 7) applying a static load or dynamic load onto the top end or bottom end of a cylindrical structure sample; 8) repeating shear load cycles; and 9) ending the test. The invention also discloses a test device of the mechanical properties of the soil-structure contact surface. According to the test method and the test device of the mechanical properties of the soil-structure contact surface, the mechanical properties of the contact surface among unsaturated soil, saturated soil, and saturated-dewatering circulating soil-structure under complex situations can be simulated, a shear load and a repeated shear load can be applied onto the contact surface between a cyclic soil sample and a cylindrical structure sample, and the mechanical properties of the soil-structure contact surface under the complex conditions can be simulated.

Test method and test device of mechanical properties of soil-structure contact surface

The invention relates to quick preparation device and method of a saturated soil sample. Saturated clay is extruded by utilizing a load-vacuum combined consolidation principle so as to obtain a saturated clay sample with a low water content (the water content is lower than a plastic limit). The device comprises a sleeve, a base, a piston, a vacuum cavity and a fixing sleeve, wherein the sleeve is sequentially and respectively provided with a slide-fit piston, a cylindrical porous stone internally embedded with a horizontal pressure sensor and the fixing sleeve; the piston, the base and the sleeve are respectively provided with upper draining holes, lower draining holes and side draining holes; and a vacuum extraction hole is arranged on the vacuum cavity. The draining process of the saturated clay is accelerated under the extruding effect of the piston through the negative pressure (about 101.325kPa) condition of the vacuum cavity, and meanwhile, horizontal stress and vertical stress applied on the saturated clay are obtained through the horizontal pressure sensor and a vertical pressure sensor so as to further obtain a coefficient k0 of earth pressure at rest (a specific value of the horizontal pressure to the vertical pressure applied to the soil sample under the condition of no lateral deformation).

Quick preparation device and method of saturated soil sample

In this study consecutive consolidated isotropically drained triaxial tests for the coefficient of earth pressure at rest (K0) were carried out to investigate its rules of evolution as well as its strength characteristics for normal, consolidated saturated silt under high pressure. The tests results indicate that: 1) for normal, consolidated saturated silt, K0 values increase as the consolidation stress increases at high pressure levels, while the nonlinear characteristics of K0 are inconspicuous compared to cohesive soils; 2) the Jaky and Roscoe equations, used to calculate K0, are only suitable for certain soils, but cannot represent these values for normal, consolidated saturated silt due to the variation in bilinear strength at high pressure; and 3) there are close relations between the nonlinear characteristics of K0 and the void ratio, measured in the tests. Both share the same functional form while under pressure. Based on our experimental results, we developed an empirical linear model to interpret the rules of nonlinear variation for the coefficient of earth pressure at rest.

Coefficient of earth pressure at rest for normal, consolidated soils

The invention relates to a device and a method for testing the coefficient of a static earth pressure. The device comprises a base, a pressure chamber, a piston, a radially-deformed resistive strain gauge and a hydraulic sensor, wherein a sample is arranged on the base; the pressure chamber is covered on the sample base; the piston is arranged in the centre of the top part of the pressure chamber and is matched with the pressure chamber in a sliding way; the radially-deformed resistive strain gauge sensor is fixed on the middle section of the sample; and the hydraulic sensor is connected to the base. The section of the piston is as large as and of the same shape as that of the sample to be specifically tested in the pressure chamber. The internal volume of the pressure chamber is adjusted by nesting a plurality of sleeves which are all equal in height and thickness. The volume of the pressure chamber is varied to improve the rigidity thereof, reduce the amount of compression of liquid in the pressure chamber and finally obtain the pressure chamber meeting a condition on the ratio Kopt of the volume of the optimal pressure chamber to the volume of the sample, namely the condition that the maximum of the variable of the diameter of the sample corresponding to different liquid pressures does not exceed 10 microns at the premise of a certain volume of the initial liquid within the pressure chamber, thereby improving the testing accuracy of the coefficient K0 of the static earth pressure.

Device and method for testing coefficient of static earth pressure

Fracture controlling of vertical shaft lining using grouting into neighboring soil deposits: A case study

The invention discloses a freezer with the adjustable freezing section length and a freezing method for the freezer. The freezer comprises a liquid supplying pipe, a liquid returning pipe, an auxiliary pipe, an inner freezing pipe, an outer freezing pipe and a plurality of annular separation boards, wherein the inner freezing pipe is arranged inside the outer freezing pipe, wherein the top end of the inner freezing pipe and the top end of the outer freezing pipe are simultaneously sealed by an upper sealing plate; the bottom end of the outer freezing pipe is sealed by a lower sealing plate; the bottom of the inner freezing pipe and the bottom of the outer freezing pipe are communicated; the annular separation boards are arranged in a cavity formed by the inner freezing pipe and the outer freezing pipe along the axial direction at intervals; a plurality of one-way valves are uniformly arranged on each annular separation board; the liquid supplying pipe and the liquid returning pipe extend into the inner freezing pipe from the outside; the liquid supplying pipe downwards extends to the bottom of the inner freezing pipe; the auxiliary pipe extends into the cavity formed by the inner freezing pipe and the outer freezing pipe from the outside; a base cone is arranged at the bottom end of the outer freezing pipe. According to the freezer and the freezing method, the effective utilization rate of refrigerating capacity is greatly improved, and the starting power of a refrigerating station is reduced. Compared with a general freezer, the freezer disclosed by the invention is more environment-friendly, economic, energy-saving and efficient.

Kuang Lianfei

Papers

Quick preparation device and method of saturated soil sample

Coefficient of earth pressure at rest for normal, consolidated soils

Device and method for testing coefficient of static earth pressure

Fracture controlling of vertical shaft lining using grouting into neighboring soil deposits: A case study

Freezer with adjustable freezing section length and freezing method for freezer