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 triaxial mechanical test device and method capable of simulating a formation condition of deep-buried artificial frozen soil. The device comprises a main body loading system,a freezing system and a sample testing system. In the main body loading system, a flange plate, a pressure bearing cylinder and a chassis form a pressure bearing shell, and the pressure bearing shellis provided with an outlet pipe and connected with an external existing hydraulic source. The freezing system is composed of a side wall freezing solution circulation channel and a bottom freezing solution circulation channel which are connected with an external existing cold source separately. In the sample testing system, an optical fiber sensor string pre-embedded in a sample is connected withan existing testing instrument and used for monitoring temperature and strain. The triaxial mechanical test device is matched with the existing servo control hydraulic source, the low-temperature cold source and the testing instrument or matched with an existing triaxial servo mechanical test machine (system), the formation condition of the deep-buried artificial frozen soil can be simulated, long-time high-pressure triaxial solidification of a soil sample is completed under the state of simulating original ground strain at first, then the soil sample is frozen under the pressure condition toform a frozen soil sample, and a triaxial mechanical test for the frozen soil sample is conducted.

Triaxial mechanical test device and method capable of simulating formation condition of deep-buried artificial frozen soil

The invention discloses a pneumatic type coupling system for preparing large remolded clay and performing one-dimensional consolidation test, which can be used for preparing a large-size cylindrical sample or hollow cylindrical sample of remolded clay in geotechnical engineering, and also can be used for performing one-dimensional consolidation test of a large clay sample. The pneumatic type coupling system comprises a displacement measuring system, a combined pressure cavity, a pore-pressure measuring system, a discharged-water volume measuring system, a pneumatic loading system and an axial tightening member. The pneumatic type coupling system disclosed by the invention has the advantages that the loading is carried out by a pneumatic mode, the pressurization is stable, uniform, measurable and controllable, the loading pressure can be more than 1.6MPa and the defect of difficult application of high pressure in weight loading is effectively overcome; a vertical metal permeable stone is embedded into a rigid and transparent sleeve to form a vertical water discharging channel, so that the defects of single water discharging channel and slow consolidation speed of traditional consolidation equipment are overcome; the pressure cavity of the pneumatic type coupling system is the rigid and transparent sleeve, so that the pneumatic type coupling system has visibility and overcomes the defect of invisibility of a traditional consolidometer.

Pneumatic type coupling system for preparing large remolded clay and performing one-dimensional consolidation test

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).

Jinrong Ma

Papers

Quick preparation device and method of saturated soil sample