As the mathematical model that integrates data training, optimization, learning, and feedback prediction is adopted, bp neural network model shows great advantages in data utilization. The basis of this test is that a sample radially constrained is axially loaded and the change in height of the specimen is measured over a period of time. In this test method a soil specimen is restrained laterally and. Characteristics and causes of the preconsolidation stress of. Preconsolidation pressure an overview sciencedirect topics. Comparative analysis on the methods for determination of consolidation and creep parameters using custom software master thesis juan antonio rebollo parada msc. Soil testing lab, laboratory services geotesting geocomp. Sample quality in the database varies from very excellent to fair i. The change in void ratio is computed using only th e primary consolidation portion of the test data and phase relationships shown in section 10. Characteristics and causes of the preconsolidation stress. Must read the concept at the end a soil mass if kept in a state free from pressure other than atmospheric and gravitational pressure has voids, or is having a scope for consolidation. The consolidation software has different data recording columns each assigned to the consolidation cells and they can. The method consists of plotting both the pressure p and corresponding void ratio e in logarithmic scale. A method to perform a field correction to consolidation curves is presented.
Utest consolidation software usoft0300 is developed according to astm d2435, d3877, d4546, bs 77. Several researchers established different methods for obtaining c from the consolidation tests. Oedometer tests are performed by applying different loads to a soil sample and measuring the deformation response. Elastic settlement and primary consolidation settlement. Mar 08, 2019 the consolidation test software automatically records and graphs consolidation or swell of soil samples during incremental loading. The data helps to determine the compression and recompression index, coefficient of consolidation and coefficient of secondary consolidation, as well as the preconsolidation pressure. Tech structures, vjti, mumbai under the guidance of prof. On the basis of research on consolidation test about the lakeside new district soft clay of hefei by high pressure consolidation apparatus, and conformed to casagrande method, the paper adopts quartic polynomial and least square method to fit the compression curve, and the preconsolidation pressure of the lakeside new distract soft clay of.
The software features full reduction of timeconsolidation data, including both square root and log of time methods. A new method called the loglog method has been proposed for a more accurate determination of preconsolidation pressure. Astm d2435 testing services standard test method for one. From a geotechnical point of view, preconsolidation stress has great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. Preconsolidation pressure is the maximum effective vertical overburden stress that a particular soil sample has sustained in the past. After every disturbance simulation circle, the specimens are reconsolidated using shansep technique, well into the virgin compression line vcl, to erase all the previous effects of disturbance. It is a time dependent behavior of soil deformation. Preconsolidation pressure for clay bigh geotechnical 2 jul 18 08.
Estimation of the preconsolidation pressure in soils using. Fig 3 shows comparison of predicted and measured over consolidation ratio. This happens because soil is a twophase material, comprising soil grains and pore fluid, usually groundwater. The consolidation test software automatically records and graphs consolidation or swell of soil samples during incremental loading.
Coefficient of primary and secondary consolidation, void ratios, compression and recompression indices, preconsolidation and swell pressures, t 0, t 50, t 90 and t 100, and swellcollapse percentages are calculated and reported. Filter element the porous element inserted into the cone penetrometer to allow transmission of pore water pressure to the pore pressure sensor, while maintaining the correct dimensions of the cone penetrometer. The preconsolidation pressure cannot be determined. Comparative tests on one organic silt indicate that the coefficients of consolidation from the back pressure test are lower than those from the standard test below the preconsolidation load. Our automated equipment permits us to run any type of consolidation, triaxial, or direct shear test a client specifies.
Jul 25, 2009 preconsolidation stress p is the maximum effective stress that a soil has suffered throughout its life. Preconsolidation pressure, c is commonly defined as the highest pressure to which the soil had been exposed in the past. The preconsolidation stress p c is determined from highquality oedometer test results by a variety of interpretation methods. The results from these tests are used to predict how a soil in the field will deform in response to a change in effective stress. Predicted preconsolidation pressure is also compared with preconsolidation pressure using ann as shown in fig 2. Consolidation test results and porosity rebound janice c.
Civ e 353 geotechnical engineering i consolidation. Preconsolidation pressure determination casagrande, 1936 1. Consolidation is the term that refers to slow expulsion of wate. Log log method for determination of preconsolidation pressure.
Following are the results of a laboratory consolidation test on a sample of undisturbed clay obtained from the field. Following are the results of a laboratory consolidation. Mar 30, 2018 the graphical method to estimate the preconsolidation pressure is demonstrated and explained. The log e log p plots result in two distinct straight lines. Consolidation test report cive334 nebraska studocu. The validity of this prediction procedure is demonstrated by test results on soils from the chicago area. The user can determine and assign different time intervals or select fixed time intervals and stresses for the calculation of the consolidation test data. The basis of this test is that a sample radially constrained is axially loaded and the change in. The relationships between the constrained moduli, the normal pressures and the preconsolidation pressures of temperatezone soils have also been established.
Soil office bearing capacity software sofoundation. The height of the specimen at the beginning of the test was 1. From the average of the cp4, pcp2, and pcp3 data, an average line is drawn and then, adopting a single standard deviation, upper and lower bound lines are drawn. Astm d2435 testing services standard test method for. Following are the results of a laboratory consolidation test. Preconsolidation pressure for clay geotechnical engineering. Presentation on 3dimensional consolidation test on soft marine clay under vacuum preloading with pvd by pankaj dhangare roll no. A simple procedure for estimating preconsolidation pressure. Summary of onedimensional consolidation test results 58 3a tp5 41. Pierce department of crop and soil sciences, michigan state university, east lansing, mi 48824, usa received 29 december 1994.
Recently, the trend has been to carry out this determination using the constrained modulus method. The effect of different isa disturbance amplitudes baligh et al. Alternative names for the preconsolidation pressure are preconsolidation stress, precompression stress, precompaction. The maximum effective past pressure is called the preconsolidation pressure. Estimate the compression index and the preconsolidation pressure from the e log.
Series of conventional consolidation tests were carried out on saturated specimens of five different. A simple procedure for estimating preconsolidation. Middle depth of the layer is considered as the layers. E ls ev i e r soil technology 8 1995 9151 soil technology a simple procedure for estimating preconsolidation pressure from soil compression curves m. Strength increase below an old test embankment in finland. Alternative names for the preconsolidation pressure are preconsolidation. Humboldt has an extensive line of consolidation testing apparatus to satisfy the needs of any soils laboratory.
This test is designed to determine the rate and magnitude of volume decrease that a soil sample undergoes when subjected to different vertical loads. The preconsolidation pressure is an important index to determine the stress history of soil and also a major calculation parameter for the analysis of soil stratums deformation in the different stress history. Preconsolidation pressure can be calculated by 3 methods, auto and specified by the user p. An oedometer test is a kind of geotechnical investigation performed in geotechnical engineering that measures a soils consolidation properties. Four tests can be recorded independently per window, each with. Dissipation test a test when the decay of the pore pressure is monitored during a pause in penetration. Determining preconsolidation pressure of the lakeside new.
The preconsolidation pressure of a laterite soil springerlink. The effects of sample disturbance on preconsolidation. Gilson consolidation test data acquisition software hma. Displacement transducers are connected to interface unit and interface unit is connected to pc by rs232 serial output. Consolidation soil mechanics utest material testing equipment.
Secondary consolidation usually estimated from a lab consolidation test. Tests on a second organic silt indicate values from the back pressure test are higher throughout the load range. Estimation of the preconsolidation pressure in soils. The one dimensional consolidation test is the commonly used test of this type in a laboratory due to the relative ease of the test procedure and simplicity of the test equipment. The software features full reduction of time consolidation data, including both square root and log of time methods. This quantity is important in geotechnical engineering, particularly for finding the expected settlement of foundations and embankments. Gilson consolidation test data acquisition software hma608. A modified loading procedure for the consolidation test is described using uniform pressure increments in the early stages. Dec 24, 20 this feature is not available right now.
The secondary consolidation portion of the consolidation curve is approximately linear on an elog time plot. The present overburden pressure is less than the soil has experienced in the past. Factors on consolidation time 1 degree of saturation. When soil saturated with water is subjected to an increase in pressure, the high volumetric stiffness of water compared to the soil matrix means that the water. Casagrade method is worldwide applied to determine the preconsolidation pressure. We provide these services in support of all types of earthwork applications. From our fullyautomated odeometer, the conmatic ipc machine, which automates the consolidation testing process, to our pneumatic or deadweight consolidation testing machines, we have consolidation testing for soil covered. For example, if clay that had been normally consolidated under an effective overburden pressure of 1 ksf is to be loaded by an embankment that will exert an additional pressure of 2 ksf, the consolidation test need not be continued beyond a load of 8 ksf to fulfill the purpose of the test. The preconsolidation pressure of a soil is often determined in the oedometer using the casagrande method. The exact cause of secondary consolidation is unknown, but is possibly a readjustment of the double water layer surrounding the clay particles. Morag gambles method for simple abundance our permaculture life duration. Wetting cycles cons can proceses data from tests that involve sample saturation, including calculating the following values. The relations developed herein were done so using field instrumentation, laboratory data and cone penetrometer soundings.
Preconsolidation pressure article about preconsolidation. Key words preconsolidation stress, compressibility, soft clays, settlement. Results show that the five methods applied give very similar p c. Newland and allely 3 discussed the influence of consolidation pressure on the secondary consolidation coefficient c. In this test method a soil specimen is restrained laterally and loaded axially with total stress increments.
Consolidation test results are considered the main laboratory test that can be used for determining the value of c. The elog plot is used to determine the preconsolidation pressure. Test method title standard test method for onedimensional consolidation properties of soils reference number astm d2435 material. Comparative analysis on the methods for determination of. The graphical method to estimate the preconsolidation pressure is demonstrated and explained.
The exact cause of secondary consolidation is unknown, but is possibly a readjustment of. Chapter 3 laboratory tests and index properties of soils. Fig 1 shows comparison of pre consolidation pressure from test results and correlations. On the basis of research on consolidation test about the lakeside new district soft clay of hefei by. Oedometer test last updated november 25, 2019 two oedometers at the university of cambridge. Preconsolidation stress p is the maximum effective stress that a soil has suffered throughout its life.
The est imation of preconsolidation pre ssure is greatly. Gtxs fully equipped laboratories perform more than 100 different soils tests to determine physical properties. Stress increase due to footing load is calculated by 3 methods, boussinesq, westergaard and approximate 2v. Preconsolidation pressure from soil index and plasticity. Descriptors microcomputers data acquisition soil tests consolidation con solidometer preconsolidation pressure settlement void ratio timedependent anal ysis casagrande construction casagrandes logarithm of timefitting method.
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