1、soils and foundations

soils and foundations發(fā)音

英：　　美：

soils and foundations中文意思翻譯

常見(jiàn)釋義：

土壤和地基

soils and foundations雙語(yǔ)使用場(chǎng)景

1、permafrost or seasonal frozen soils are undesirable engineering geologic condition and the frost heave and thawing settlement will influence the stability of foundations.───凍土和季節性?xún)鐾翆儆诓涣脊こ痰刭|(zhì)條件，其物理特性、力學(xué)和熱學(xué)性能決定了凍脹和融沉工程病害對線(xiàn)路基礎穩定性的影響程度。

2、Dynamics of Soils and Foundations───土基礎動(dòng)力學(xué)

3、Lessons Learned from Damages of Soils and Foundations during Several Strong Earthquakes───幾次大地震中地基基礎震害的啟示

4、In this paper the dynamic influence depth and the soil mass of participating in vertical vibration are researched for inhomogeneous base soils under machine foundations.───在不均質(zhì)地基上的機器基礎的動(dòng)力影響深度問(wèn)題以及地基土的參振質(zhì)量問(wèn)題進(jìn)行了初步的研究。

soils and foundations相似詞語(yǔ)短語(yǔ)

1、terms and conditions───條款和條件；合同條款；費率表

2、solid foundation───基礎雄厚；實(shí)體基礎

3、ring wall foundations───環(huán)形墻基礎

4、build a foundation───建立基礎

5、tank foundations───儲罐基礎；液艙座

6、build foundations───建立基礎

7、shaky foundations───地基不穩

2、Shear Strength Tests

The shear strength of a soil is a basic geotechnical engineering parameter and is required for the analysis of foundations，earthwork，and slope stability problems. The shear strength of the soil can be determined in the field ( e. g. ，by a vane shear test) or in the laboratory.

There are many types of shear strength tests that can be performed in the laboratory. The objective is to obtain the shear strength of the soil. Laboratory tests are generally divided into two categories:

Shear strength tests based on total stress. The purpose of these laboratory tests is to obtain the undrained shear strength suof the soil or the failure envelope in terms of total stress ( total cohesion c and total friction angle φ) . These types of shear strength tests are often referred to as undrained shear strength tests.

Shear strength tests based on effective stress. The purpose of these laboratory tests is to obtain the effective shear strength of the soil based on the failure envelope in terms of effective stress ( effective cohesion c' and effective friction angle φ') . These types of shear strength tests are often referred to as drained shear strength tests.

The types of common laboratory tests used to obtain the shear strength of the soil are as follows:

Vane Tests. The vane shear test ( VST ) can be performed in the field to obtain the undrained shear strength suof clay. The miniature vane or torvane device could also be used in the laboratory to obtain the undrained shear strength suof clay.

Unconfined compression test. The unconfined compression test is a very simple type of test that consists of applying a vertical compressive pressure to a cylinder of laterally unconfined clay. The vertical compressive pressure that causes shear failure of the clay is termed the unconfined compressive strength qu. Some clays are so plastic that instead of shearing，they deform and bulge，and in these cases the unconfined compressive strength quis defined as the vertical compressive pressure at 15% axial strain.

The unconfined compressive test should not be performed on dry and crumbly soils， fissured or varved clays，silts，peat，and all types of granular material. The ratio of height to diameter of the cylinder of clay should be between 2 and 2. 5. The clay specimen should also be tested in standard laboratory equipment that can accurately record the force applied to the top of the clay specimen as well as record the vertical deformation of the specimen as it is loaded. Typical loading rates of the clay specimen are 0. 5 to 2 percent of the initial height L0per minute.

Unconsolidated undrained triaxial compression test. The unconsolidated undrained triaxial compression test is similar to the unconfined compression test，except that clay specimens are subjected to a confining fluid pressure in a triaxial chamber. The cylindrical clay specimen is placed in the center of the chamber，sealed with a rubber membrane，and subjected to a confining fluid pressure. A vertical pressure is slowly applied to the top of the specimen by slowly loading the piston. No drainage of the clay specimen is allowed during the test. The clay specimen is sheared in compression without drainage at a constant rate of axial deformation ( strain controlled) .

If the clay specimens are saturated，the confining pressure will not change the wet density of the specimen. Therefore，if several identical clay specimens are tested，they will all have approximately the same undrained shear strength ( failure envelope will be a horizontal line) . Since this test does not provide any additional information for saturated clay specimens，it is used much less frequently than the unconfined compression test.

Consolidated undrained triaxial compression test. The consolidated undrained triaxial compression test is similar to the unconsolidated undrained compression test，except that the clay specimen is first consolidated prior to shearing. This test can also be used to measure the excess pore water pressures that develop within the clay as it is sheared. The shear strength based on total stress or based on effective stress ( by measuring the pore water pressure during shear) can be obtained from this laboratory test. The test is quite complicated and should be performed only by experienced personnel. This test has been used to study the shear behavior of all types of soil.

Direct shear test. The direct shear test，first used by Coulomb in 1776，is the oldest type of shear testing equipment. The direct shear test is also the most common testing method to obtain the drained shear strength of a soil. Figure 5. 2 shows the direct shear testing device. The testing procedure is as follows:

1) The soil specimen ( typical diameter = 63. 5 mm and height = 25. 4 mm ) is placed on top of a porous plate in the center of the direct shear apparatus.

2) A porous plate is placed on the top of the specimen and a dial gauge is set up to measure vertical deformation.

3) A loading device is used to apply a vertical force to the soil specimen. This vertical force，also known as the normal force，is converted to a stress by dividing the vertical force by the cross-sectional area of the soil specimen.

4) A surrounding container allows the soil specimen to be submerged in distilled water.

5) The soil specimen is allowed to equilibrate or fully consolidate under the applied vertical stress.

6) A dial gauge is set up to measure horizontal deformation and then an increasing force is applied to the upper half of the direct shear apparatus. The shear force can be applied by using deadweights placed on a hanger ( stress-controlled test) or by a motor acting through gears( strain-controlled test) .

7) The soil specimen is slowly sheared in half ( a single shear plane) .

8) The maximum shear force required to shear the sample is recorded and the shear strength is defined as this shear force divided by the cross-sectional area of the soil specimen.

9) The shear strength versus the vertical stress can be plotted and a failure envelope is obtained.

Figure 5. 2 Direct shear apparatus

It is important to shear the soil specimen slowly enough that excess pore water pressures do not develop within the soil specimen. For clean sands，the total elapsed time to failure should be about 10 minutes，while for silty sands the total elapsed time to failure should be about 60 minutes. For clean sands and silty sands，the setup and actual testing operation is relatively quick and simple，which is the main reason for the test's popularity.

Drained residual shear strength. The previous shear strength tests have described methods to obtain the undrained shear strength suor the shear strength parameters ( c or c' and φ or φ') that define the failure envelope. These tests normally determine the shear strength of the soil， which is defined as the shear stress at failure ( i. e. ，the peak shear strength) .

For some projects，it may be important to obtain the residual shear strength of fine- grained soil， which is defined as the remaining ( or residual ) shear strength after a considerable amount of shear deformation has occurred. For example，a clay specimen could be placed in the direct shear box and then sheared back and forth several times to develop a well-defined shear failure surface. Once the shear surface is developed，the drained residual shear strength would be obtained by performing a final，slowshear of the specimen. The drained residual shear strength can be applicable to many types of soil or rock conditions where a considerable amount of shear deformation has already occurred. For example，the stability analysis of ancient landslides，slopes in overconsolidated fissured clays，and slopes in fissured shales will often be based on the drained residual shear strength of the failure surface.

Skempton stated that the residual shear strength ( friction angle ) is independent of the original shear strength，water content，and liquidity index，and depends only on the size， shape，and mineralogical composition of the constituent particles. Besides the direct shear equipment，the drained residual shear strength can be determined by using a modified Bromhead ring shear apparatus. Back calculations of landslide shear strength indicate that the residual shear strength from the ring shear test is reasonably representative of the slip surface. The ring shear specimen is annular with an inside diameter of 7cm ( 2. 8in) and an outside diameter of 10cm ( 4in) . Drainage is provided by annular bronze porous plates secured to the bottom of the specimen container and the loading platen.

Remolded specimens are often used for the ring shear testing. A typical testing procedure is as follows:

1) The remolded specimen is typically obtained by air drying the soil，crushing it with a mortar and pestle，ball milling the crushed material，and processing it through the United States Standard Sieve No. 200.

2) Distilled water is added to the processed soil until water content approximately equal to the liquid limit is obtained. The specimen is then allowed to rehydrate for 7 days in a moist room. A spatula is used to place the remolded soil paste into the annular specimen container.

3) To measure the drained residual shear strength，the ring shear specimen is often consolidated at a high vertical pressure ( such as 700 kPa) and then the specimen is unloaded to a much lower vertical pressure ( such as 50 kPa) .

4) The specimen is then presheared by slowly rotating the ring shear base for one complete revolution using the hand wheel.

5) After preshearing，the specimen is sheared at a slowdrained displacement rate ( such as 0. 02 mm / min) . This slowshear displacement rate has been successfully used to test soils that are very plastic.

6) After a drained residual strength condition is obtained at the lowvertical pressure， shearing is stopped and the normal stress is increased to a higher pressure ( such as 100 kPa) . After consolidation at this higher pressure，the specimen is sheared again until a drained residual condition is obtained.

7) This procedure is also repeated for other effective normal stresses. The slowshear displacement rate ( 0. 02 mm / min) should be used for all stages of the multistage test.

Figure 5. 3 presents the drained residual failure envelope. It can be seen in the figure that the failure envelope is nonlinear，which is a common occurrence for residual soil.

Figure 5. 3 Drained residual shear strength envelope from ring shear test on slide plane material