Geotechnical studies, zoning and field explorations of the Soil Mechanics and Technical Laboratory

Geotechnical Studies, Zoning, and Desert Explorations

This department began its activities simultaneously with the establishment of the Technical and Soil Mechanics Laboratory under the name of the Local Research Division. The main activities of the office currently include conducting geotechnical studies in the Technical and Soil Mechanics Laboratory by performing drilling operations to depths exceeding 1500 meters using metric and wireline methods with modern facilities and equipment. This includes soil sampling, field tests, cement injection tests, exploratory gallery drilling, soil mechanics laboratory, and in-situ testing.

Geotechnical Engineering Services:

Introduction:

The Geotechnical Studies, Zoning, and Desert Explorations Office, with over 50 years of experience in conducting geotechnical drilling operations and providing engineering reports, is ready to provide geotechnical study services. The office has 30 semi-deep and deep drilling rigs and is engaged in drilling operations throughout Iran.

Geotechnical Study Services:

1- Geotechnical Studies:

1.1. Drilling boreholes and in-borehole tests (SPT, Lefranc, and Lugeon) and in-borehole geophysics.

1.2. Laboratory tests of soil, rock, and construction materials.

1.3. Interpretation of the results of all geotechnical engineering operations.

1.4. Geological and seismic engineering studies.

1.5. Identification of groundwater resources.

2- Determination of the safe bearing capacity and calculation of allowable settlement for various types of surface, semi-deep, and deep foundations (piles).

3- Determination of the coefficient of subgrade reaction of the soil.

4- Providing lateral pressure coefficients of soil.

5- Categorization of soil types based on the Road and Railways Bridges Design Code against earthquakes (Code No. 463).

6- Determination of the type of cement used in piles based on the results of chemical tests on water and soil.

7- Providing results of laboratory tests for structures and underground installations such as tunnels, shafts, caves, and similar structures.

8- Special geotechnical engineering studies:

8.1. Performing CPTU tests and providing the results of the tests, including:

• Providing a continuous soil profile.
• Determining the value of N60 (SPT) equivalent to CPTU at the desired depth.
• Shear strength of cohesive soils (Su).
• Relative density of sandy soils (Dr).
• Friction angle of sandy soils (φ).
• Total stress and effective stress.
• Permeability rate in cm/s.

8.2. Using CPTU test results for:

• Determining the bearing capacity of surface and deep foundations (piles).
• Estimating the settlement of surface piles.
• Soil compaction and improvement control.
• Investigating the phenomenon of liquefaction.

8.3. Determining the elastic modulus of in-situ soil using Pressueremeter tests and analyzing the results.

8.4. Analysis and design of deep foundations (piles) using AllPile software.

8.5. Determining the safe bearing capacity and allowable settlement for surface piles on rock.

8.6. Determining the safe bearing capacity and allowable settlement for piles socketed into rock (Piles socketed into rock).

Drilling and In-Situ Tests

Drilling services at considerable depths

With regard to the needs of different clients and consultants in the fields of geotechnical engineering and mining, and the demand for deep borehole drilling, after comprehensive technical assessments, this department is equipped with three full hydraulic drilling rigs capable of drilling up to 1500 meters using the wireline method.

These drilling rigs are crawler-mounted, equipped with 25-ton winches with a wireline capacity of 1500 meters and high winch speed (119 meters per minute). The rigs are powered by Volvo Super D6 engines with 262 horsepower, allowing drilling with sizes PQ up to 600 meters, HQ up to 1000 meters, and NQ up to 1500 meters. They can be moved within the worksite in challenging terrains without the need for a crane.

Additionally, besides the full hydraulic rigs, the office also possesses mechanical drilling rigs (SKB and Longyear) capable of drilling boreholes up to 300 meters in depth.

Pressiometry Test

The pressiometry test is one of the in-situ tests used in geotechnical engineering to estimate the stress-strain behavior of soil. It can be conducted in various soil types with careful consideration of implementation factors. The test involves drilling a borehole, inserting and applying pressure through water and nitrogen gas to expand the probe against the borehole wall. Parameters such as soil ultimate strength and pressiometric modulus can be obtained from this test, which can be used in the design of shallow and deep foundations.

Parameters extractable from the results obtained from the device:

1- Menard modulus (Em)

2- Initial pressure (Po)

3- Creep pressure (Pf)

4- Ultimate pressure (PL)

Cone Penetration Test (CPTU)

The Cone Penetration Test (CPTU) is a field test that has gained significant attention in recent years among geotechnical engineers. This test provides valuable data for various applications, including identifying soil layers, estimating bearing capacity, settlement prediction for piles, and assessing liquefaction potential in sands. CPTU can be conducted in both dry and marine environments and is suitable for soft to medium-soft and silty soils. It is performed in accordance with ASTM D5778 standard.

Some of the advantages of CPTU testing are as follows:

• High speed and consistency in determining soil parameters.
• Reproducibility and obtaining reliable data.
• Economical to perform the test.
• Strong theoretical basis for interpreting the results.
• Operator-independent results presentation by the device (all charts and recorded data).
• Equipped with a sensor to control the maximum deviation angle (up to 15 degrees).
• Equipped with software for parameter measurements.
• Conducting the test of dissipation of pore pressure (testDissipation) at various depths.

Parameters measurable by the device:

• Recording separate graphs of qc, fs, and u2 with a resolution of cm1, exportable in Excel format.
• Providing a continuous soil profile.
• Estimating N60 value equivalent to SPT at the desired depth.
• Undrained shear strength (Su) of cohesive soils.
• Relative density (Dr) of sandy soils.
• Friction angle (φ) of sandy soils.
• Total stress and effective stress.
• Permeability rate in cm/s.

Dilatometer Test

Dilatometer test results are used in geotechnical investigations of piles, dams, tunnels, caverns, and more. The test involves using an expanding probe to apply pressure to the borehole wall, and a displacement sensor measures the dilation within the borehole. The stress distribution range in the dilatometer test is smaller compared to other methods such as plate loading tests or small-scale radial jack tests. However, its results are closer to reality when compared to undisturbed laboratory specimens. This test is applicable in rocks with low fractures and fissures (high RQD).

Parameters that can be measured:

The dilatometer test allows the calculation of the modulus of deformability for the rock mass from the relationship between pressure and dilation.

Parameter measurable:

In this test, the modulus of deformability of the rock mass can be calculated from the relationships between pressure and dilation.

Parameter measurable:

From the obtained data of incremental and cyclic loading, the modulus of deformability and elasticity of the rock mass can be calculated. The shear parameters of the rock mass are also obtained from the displacement-time graphs.

Cement Injection Test

Cement injection is a method used to stabilize and improve the soil and rock mass. It involves injecting cement grout under controlled pressure into the ground, which enhances the material's strength. The injection process fills voids, cavities, fractures, etc., present in the rock and soil, resulting in increased resistance, reduced deformability, and permeability.

Parameters measurable:

The following parameters can be determined in cement injection tests:

• Determining the type and approximate amount of cement required during the execution phase.
• Determining the mix design of the consumed cement.
• Determining the distance and arrangement of injection points and their coverage by calculating the injection radius.
• Specifying the conditions of curtain injection and water barrier wall.
• Determining the permeability of injection points.

The injection equipment used in this office includes:

• Mixers (1500 RPM mixer)
• Agitators (50 RPM mixer)
• Injection pump with a pressure of 100 bar and a flow rate of 1500 liters
• Digital and mechanical stabilizers
• Single and double packers
• And other accessories such as water gauges, pressure gauges, pressure breakers, hoses, etc.

Soil Mechanics Laboratory

The laboratory performs various laboratory tests to study soil mechanics, aiming to accelerate the testing process of large-scale projects. Some of the tests conducted in the laboratory include:

• Determining the relative moisture content of soil according to ASTM D2216.
• Soil and aggregate grain size analysis according to ASTM C136.
• Hydrometer, liquid, and plastic limits tests according to ASTM D422 and ASTM D4318.
• Direct shear test on coarse-grained soils using a large shear box according to ASTM D3080.

Rock Mechanics Laboratory

Uniaxial Compression Test Machine for Rock

ASTM D2938, D4555, ISRM

ISIRI 17194

This uniaxial compression test machine is used for measuring the confined compressive strength of rock specimens. In this test, axial load is continuously applied by a hydraulic jack. The hydraulic jacks used in the rock uniaxial test in the laboratory are fully automatic and have capacities of 2000 KN. The loading rate is selected by the user. The automatic control of the loading rate is performed by the hydraulic jacks. Additionally, the device has the capability of adding strain gauges (strain gauges or LVDT) to the specialized mold for measuring elastic modulus and Poisson's ratio.

Rock Direct Shear Apparatus

Astm D5607, ISRM

This method is a simple and practical test for determining the strength and stability of rock discontinuities. The direct shear apparatus is suitable for testing specimens with a maximum surface area of 125x115 mm or core samples up to 101mm in diameter. The shear box consists of two parts: the upper box, which includes a vertical force transfer arm for applying compressive load, and the lower box, which has two force transfer arms for generating reversible shear. The force applied by the horizontal arm is balanced with the center of the box and the discontinuity region of the specimen. The pressures applied to the force transfer arms are done using manual hydraulic pumps. The vertical force is measured by a force gauge with a capacity of 50KN and an accuracy of 1KN, and the horizontal displacement is measured by a dial gauge with a range of 25mm and an accuracy of 0.01mm.

Rock Triaxial Apparatus

ASTM D2664, ISRM

The triaxial apparatus for rocks is used to determine the strength of cylindrical rock specimens under triaxial compressive loading. The laboratory's triaxial jacks are of type RO100 - jack 2000 KN, fully automatic, with automatic control of confining pressure synchronized with cell pressure and automatic control. The apparatus is equipped with a manual auxiliary pump (60MPA), hoses, couplings, a 600BAR gauge, and a cell hook, along with a membrane that can be connected to a computer to plot stress-strain diagrams, Mohr's circles, and calculate shear strength parameters.

The hydraulic jack features include:

• Uniform loading rate with pre-set initial setting.
• Ability to record specimen dimensions and calculate axial stress.
• Sending data to the computer and storing them in PDF and XLS formats.
• OVERLOAD software for system cut-off.
• Oil tank level indication.
• Steel and stone pressure plates with a hardness of up to 60HRC.
• Software calibration capability.

If necessary, the apparatus can be equipped with STRAIN GAUGE for calculating the modulus of elasticity and Poisson's ratio of the rock. The apparatus has an intelligent stabilizing system for uniform confining pressure during the test.