SU1322149A1 - Method and apparatus for determining dynamic characteristics of ground - Google Patents

Abstract

The invention relates to the field of construction and is intended to determine the dynamic properties of soils under the conditions of the stress state of npocTpaHCTBeliHoro. The aim of the invention is to improve the accuracy and reduce the complexity of determining the dilatant part of the bulk deformation of the soil under dynamic action. The dynamic characteristics of the soil are determined under static and dynamic loads of the soil sample with preservation of the average stress (b), with constant if the condition is met (Jo (&, + 2G) / 3, where G, is the axial depth ( L 00 1C to NU SB

Description

load, MPa; G - radial load MPa. The application of axial and radial dynamic loads to the soil sample is made with the oscillation of one of them lagging by half the period of oscillation of the other load. The determination of the din of the soil characteristics is carried out using a device comprising a stabilometer with a working chamber 2 for placing the soil sample 3f with static axial and radial loading tools, a loading hydraulic cylinder 5 and a hydraulic pulsator. The latter is made in the form of a vibrator 8 with a pusher 9, a rocker arm 10 and a pair of hydrocypindra 11 and 12,

one

The invention relates to construction and is intended to determine the dynamic properties of soils under complex stress conditions under seismic effects.

The aim of the invention is to improve the accuracy and reduce the complexity of the determination of the dilatant part of the bulk strain.

FIG. 1 is a general diagram of the device J in FIG. 2 - stabilometer diagram

The device includes a stabilometer with a rod 1 and a working chamber 2 for the soil sample 3, mounted on the table 4, a loading hydraulic cylinder 5 mounted on the stabilometer housing and connected to a static axial loading hydraulic cylinder 6, a hydraulic cylinder 7 for static radial loading, connected to the working chamber 2 and a hydro pulsator for dynamic loading, made in the form of a vibrator 8 with a pusher 9 pivotally connected to the rocker arm 10 and a pair of hydraulic cylinders 11 and

12 mounted on the frame 13 by means of a carriage 14, allowing the cylinders to be moved along the bed

13. The rods of the hydraulic cylinders 11 and 12 are pivotally connected to the ends of the rocker arm 10 pivotally attached to the frame 13. The hydraulic cylinder 5 is loaded: the canopy is mounted on the stabilometer body, its rod is made in one piece with the rod 1 of the stabilometer, and the hydraulic cylinders are fixed to the frame 13 using a carriage 14. The rods of the hydraulic cylinders 11 and 12 and the pusher 9 are pivotally connected to the rocker arm 10, which is attached to the frame 13 pivotally. The loading hydraulic cylinder 5 is installed on the stabilizer case, the cylinder 1 of which is integral with the hydraulic cylinder rod, loading 5. The hydraulic cylinders 12 and 11 are connected with the working chamber 2 and the loading hydraulic cylinder 5, respectively. The latter is connected with the hydraulic cylinder 6 for static axial loading. 2 sec. and 1 hp ffly table 2, 2 ill.

river pulsator 1 1 and 12 pipelines are shared respectively with the hydraulic cylinder 5 loading and with the working chamber 2 of the stabilometer. At the base

soil sample 3 and in the working chamber 2 of the stabilometer are placed pressure sensors 15 and 16, and displacement sensors 17 and 18 are located on the rod 1 of the stabilometer and on the rod of the hydraulic cylinder 7. The sensors are connected by wires to amplifiers 19 connected to a recorder 20. Working chamber 2 is equipped with upper 21 and lower 22 dies, between which sample of soil 3 is installed in a rubber sheath 23. Pipelines connecting working chamber 2 and loading hydraulic cylinder 5 with hydraulic cylinders 6, 7, 11 and 12 have cranes 24, 25, 26, 27.

The method for determining the dynamic characteristics of the soil is carried out as follows.

For soil sample 3, placed

In the working chamber 2 of the stabilometer, axial and radial static loads are applied, for example, in steps of 0.01-0.1 MPa. After reaching a predetermined isotropic state, characterized by equality of axial (b,) and radial ((5,) loads between each other, they begin to increase the axial load by the indicated steps while simultaneously reducing by half the radial load steps,

meanwhile preserving the value of the environments31

its voltage C is constant, provided that G (G, + 2G j) / 3. Dowdy the stress state of a soil sample to a given one, axial and radial dynamic loads of a given amplitude of the order of 0.05–0.2 MPa are applied to it, and frequencies of the order of 5–10 Hz varying in accordance with the harmonic law, lagging the oscillations of one of them are by half the period of oscillations of the other load, thereby achieving the value of the mean voltage o, constant under the condition Cd (G, + 2b) / 3. The specified number of cycles of dynamic loading is performed (10-50 depending on the earthquake force), after which the dynamic load is removed. Then, the soil sample is brought to fracture, increasing the axial static load by the steps, at the same time reducing the radial load by the steps, thereby maintaining the value

G constant o

In the course of the experiment, the values of axial and radial stresses and deformations are recorded and the volumetric deformation of the soil sample, which occurred under the dynamic effect, is determined (-.Dip,

(si), which constitutes the dilatant part of the volumetric strain under dynamic action.

from the ratio

ANN

rain . (ga-

D - volumetric deformations about

 the soil sample i is a part of the volume deformation of the soil sample due to uniform, all-round compression by the load GP (0, + 2G j) / 3;

part of the bulk deformation of the soil sample due to particle repacking (the dilatant part).

A device for determining the dynamic characteristics of the soil works as follows.

A soil sample in a rubber sheath 23 is installed in the working chamber 2 of the stabilometer between the lower 22 and L upper 21 stamps. The chamber is stabilized with the hydraulic cylinders 7, opening the taps 24 and 25 and, through the valve 25, is filled with their working fluid, such as water. Hydraulic loading cylinder 5 communicates with hydraulic cylinder 94

Frames 6 and 11, opening the taps 26 and 27, and through the valve 26 also fill them with a working fluid. Sensors 15-18 are connected by wires to amplifiers 19 and to a recorder 20. Zero readings of sensors are recorded on a recorder, and later, during the whole experiment, the specified stresses and strains of the soil sample are automatically recorded. The application of axial and radial static loads is carried out by loading the cylinders 6 and 7, respectively, with the help of weights. To apply a dynamic load to a soil sample, a hydropulsator is included. When moving the pusher 9 of the vibrator 8 up the left shoulder of the rocker arm 10 loads the hydraulic cylinder 11, this increases the axial dynamic load, while the right shoulder of the balancer unloads the hydraulic cylinder 12 and reduces the radial dynamic load on the sample. When moving the pusher down, the opposite effect occurs, i.e. the axial dynamic load decreases and the radial load increases. Thus, the required number of loading cycles is performed.

Example 1 A medium-grained, medium-density sandy soil is studied in an air-dry state.

 - 0.67 - porosity coefficient, specific gravity J 1.70 g / cm, humidity W 0.1%. The measurement results are shown in Table. one.

). 0.33 + 0.01 0.34%,

Dilatans part of the volumetric strain of 0.34%,

Example 2. Sandy soil, medium-grained, medium density, porosity coefficient 0.61, specific gravity of 1.9 t / m, oscillation frequency 40 Hz, amplitude of voltage variation 0.2 kg / cm, duration of dynamic effect 1 h. The measurement results are shown in Table. 2

one

 (.) 0.27% -0.17% 0.10%,

five . 13

The dilatans part of the volume strain is 0.10%.

The invention makes it possible to increase the accuracy and reduce the laboriousness in studying the dilatant properties of soils, which significantly affect their behavior under dynamic effects, and to take these properties into account when analyzing the seismic stability of soil foundations and structures.

Claims (2)

1. A method for determining the dynamic characteristics of a soil, including compressing a soil sample in a stabilometer by applying axial and radial static loads in equal steps to a predetermined value, applying a stepwise increasing axial static load to a predetermined stress state, applying an axially varying axial change and radial dynamic loads given by the amplitude of the individual frequency and the number of cycles with the measurement of axial and radial deformations, bringing the soil sample to ruin neither by applying an axial static load and determining the dilatation part of the volumetric strain under dynamic impact, which is characterized by the fact that, in order to increase the accuracy and reduce the laboriousness of determining the dilatagous part of the volumetric strain, the stepwise increasing axial static load condition is produced with a simultaneous decrease of the radial load, and the application of axial and radial dynamic loads is made with the lag of oscillations of one of them olovinu period other load oscillations at , „ 5 o  5 20 - 35 40 45 25 In this case, the application of axial static load while reducing the radial load and the application of dynamic loads are produced while maintaining the average stress of the soil sample G constant with the condition  0 (C5, + 2b,) / 3, where G, - axial load, MPa; Gj - radial load, MPa. 2. A device for determining the dynamic characteristics of the soil, including a stabilometer with a rod and a working chamber for placing the soil sample, tools for static axial and radial loading, a hydro pulsator for dynamic loading, mounted on a frame, a loading hydraulic cylinder connected to it and different measuring devices the fact that hydropulsator is made in the form of a vibrator with a pusher, rocker arms and a pair of hydraulic cylinders mounted on the frame with the possibility of horizontal displacement , Wherein the hydraulic cylinder and plunger rods vibrator pivotally connected with a yoke, fastened pivotably on the frame, the stress is set cylinder on the stabilometer housing, and the rod of the latter is made in one piece with the loading cylinder of the hydraulic cylinder, while the hydraulic cylinders of the hydropulsator are connected respectively to the loading hydraulic cylinder and the working chamber of the stabilometer. 3, the apparatus according to claim 2, wherein the device for static axial loading is made in the form of a hydraulic cylinder communicated with the loading hydraulic cylinder. Table 1 / / 7 FIG. 2 VNIIPI Order 2856/39 Circulation 776 Subscription Arv-polygr. pr-tie, Uzhgorod, st. Project, 4