This paper presents a multidisciplinary approach for the determination of these two factors and for the construction of a reliable model of the subsoil for the slope stability analysis. Evaluating and maintaining piezometers, relief wells, and drains charles n. Inclinometers are the most commonly used instrument type when attempting to measure small levels of ground creep or shear zone movement, particularly between 0. All geosense vw piezometers carry a unique identification serial number which is located on the cable close to the piezometer body and at the free end of the cable see right. Rst vibrating wire piezometers provide excellent longterm accuracy, stability of readings and reli ability under demanding geotechnical conditions. Vibrating wire piezometers are the electrical piezometers of choice as the frequency output of vw devices is immune to external electrical noise, and able to tolerate wet wiring common in. A slope stability calculation, the be used to calculate approximate factor of safety fos values slip planes whilst changing other the infinite slope method assumes the following. Guideline for installation of pneumatic piezometer. Reducer couplings can also be used to connect to other sizes of riser pipe or casing. These guidelines provide the minimum standard of care for installation of pneumatic piezometers on alberta transportation projects. Rst vibrating wire piezometers are shipped with extremely tough polyurethanejacketed foilshielded cable for maximum endurance in field conditions. This paper concentrates on the slope stability issues related to ground water. This engineer manual em provides guidance for analyzing the static stability of slopes of earth and rockfill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock.
Instrumentation for slope stability experience from an urban area. The effects of ground water, slope stability, and seismic. Monitoring porewater pressures to evaluate slope stability. Vw piezometers applications vw piezometers are used to monitor porewater pressure and water levels. Pore water pressures and slope stability oxford academic journals. It is concerned with 1 the characteristics and critical aspects of various types of slope stability problems, 2 geologic studies and site investigation procedures, 3 methods of designing slopes, including field observations and experience, slope stability. As mentioned above, two casagrande piezometers have. The valdez marine terminal was constructed between 1974 and 1977 at the southern end of the 800 mile long transalaska pipeline.
Piezoresistive piezometers have a filter tip that prevents small particles of soil from entering the chamber in front of the diaphragm. Slope indicator s automated, precision calibration system ensures that these sensors meet or exceed specifications. The standard 601 piezometer tip lengths available are. Next to gravity, water is the most important factor in slope stability. The 60micron filter in the 601 piezometer is also ideal for air sparging and metals sampling.
Guide to geotechnical instrumentation durham geo slope indicators. Hydraulic piezometers the tubes are used to circulate water through the system, removing air and ensuring that the reservoir remains full of water. The rst vibrating wire piezometer provides excellent longterm accuracy, stability of readings and reliability under demanding geotechnical conditions. The zor develops according to the excavation schedule and is generally more permeable than the in situ rock. Piezometers are the geotechnical sensors that are used to measure pore water pressure piezometric level in the ground. Top, right existing slope failure on mdot trunkline. The effects of ground water, slope stability, and seismic hazard on the stability of the south fork castle creek blockage in the mount st. Slope stability, wick drains, horizontal slope drains, slope remediation, intenal drains no restrictions 19.
Inclinometers and piezometers have been installed at a number of locations and. Center, right 16inch diameter steel pile driving at proposed bridge abutment. All vw piezometers are supplied with individual calibration sheets that include their serial numbers and these will shipped with the piezometers. Unsaturated and transient seepage analysis of san luis dam timothy d.
To assess the stability of slopes under shortterm often during construction and longterm conditions. Multipoint piezometer strings allow for multiple vibrating wire piezometers to be connected on a single cable. Alternative types may be driven or pushed into soft soil. A set of 5 basic slope stability problems, together with 5 variants, was distributed in the australian geomechanics profession and overseas as part of a survey sponsored by acads association for computer aided design, in 1988. A change in the stability of a slope can be caused by a number of. Due to the angle of the embankments, access to the piezometers and dataloggers was impractical and could have been dangerous and so each piezometer was connected to a single channel vw wisos 480 node so that groundwater monitoring could be done wirelessly. The use of the investigation data to evaluate the type of movement, the. If the piezometric profile is near or above the ground surface, slope stability may be reduced, or seepage may appear at the surface. Chapter 10 slope stability analysis nysdot geotechnical page 104 january 21, 2014 design manual 10. It consists of filter tip joined to a riser pipe that extends to the surface. Simulation of threedimensional porepressure distribution. Multipoint piezometers comprise of several piezometers connected together on a common cable which allows multiple piezometers to be simply and reliably installed in a single borehole.
Slope stability analysis requires accurate information of soil stratigraphy and strength. Piezometers in the downstream zones can show whether the drains are working properly. In general, if stable slopes will be cut back into an existing slope 10 feet or less and at the same or flatter angle of inclination, the slope height does not increase significantly because of. They are made up of low air entry porous plastic or ceramic elements which are connected to standpipe tubing and lowered into a predrilled borehole. Typical applications include evaluating slope stability, dewatering and drainage schemes, overpressure in silt and clay soils, permeability and hydraulic gradients in dams. In recognition of his years of guidance and support as a mentor and friend to geotechnical specialists in the northwest, we dedicate these volumes, a summary of what we have. Due to the angle of the embankments, access to the piezometers and dataloggers was impractical and could have been dangerous and so each piezometer was connected to a single channel vw wisos 480 node so that groundwater monitoring could. Methods for analysis of slope stability are described and are illustrated by examples in the appendixes. To assess the possibility of landslides involving natural or existing engineered. The effect of water on cut and fill slope stability is briefly discussed below.
In cohesionless soils, water does not affect the angle of internal friction. Monitoringporewaterpressuresto determine safe rates of fill or excavation. After the standpipe piezometer is installed to depth, groundwater enters through the porous filter and into the riser pipe, allowing water level monitoring, metals sampling, permeability measurements, slope stability tests, etc. Monitoring of ground water pressure, using stand pipe piezometers, in drained.
Three types of boundary conditions were assigned to the. Slope stability analysis stability analyses stability analyses were performed on eight cross sections of the proposed midbarataria sediment diversion mbsd to assess the potential for stability concerns or problems along the channel alignment from the inlet system to the western end of the conveyance channel. It is excellent for metals sampling, as it is composed of a preformed porous polyethylene tube set inside a perforated pvc piezometer tip. Vibrating wire piezometers applications vw piezometers are used to monitor porewater pressure. Slide is a slope stability software with builtpackage in finite element groundwater seepage. Well suited for water level monitoring, permeability measurements, construction control, dewatering drainage operations, and. In the stability analysis of slopes, as a part of the geotechnical analyses, many. Vw piezometers respond very quickly to changes in porewater pressure. The fieldready peristaltic pump is ideal for shallow groundwater sampling using drivepoint or standpipe piezometers. Pdf role of realtime monitoring in slope stability researchgate. Effect of climatic changes on slopes can be assessed using realtime monitoring. Mar 21, 2016 the aims of slope stability analyses are to understand the development and form of natural slopes and the processes responsible for different natural features. Deviations from these guidelines may be permitted by the director of geotechnical and materials section, technical standards branch.
Vw piezometers were installed on steep embankments. A thermistor is built into the piezometer body to permit temperature measurement and temperature compensation of the piezometer. Slope stability verification manual deep excavation llc page 11 e. It is designed to measure pore water pressure in the soil, earthrock fills, foundations and concrete structures. Potential failure surface parallel to the ground surface assumes gravity is the primary factor. Department simplified users forest service guide to. Vibrating wire piezometers are used to monitor porewater pressure in soils. After excavation, a zor layer generally develops to a certain depth below the pit surface. The pores in the filter allow entry of water, but not particles of soil. Pdf importance of pore pressure monitoring in high walls.
Monitor dam performance, rate of construction, slope stability assessment, ground improvements. This type of analysis is also utilized to determine. Bottom, left graphical 3d representation of aerial lidar data collected on federal highway route. Importance of water next to gravity, water is the most important factor in slope stability. The wick drains are intended to promote the rate of settlement and to minimize pore pressure increases. There are too many sensors for timely manual readings. Haug, department of civil and geological engineering, university of saskatchewan. Several geotechnical instruments such as piezometer, tensiometer. A case study of groundwater modeling and slope stability analysis in the panama canal m. Center, left drill crew drilling with a cme 850 atv. Dam safety instrumentation plates 4 when and where to use. Chapter 10 soil cut design washington state department.
Standpipe piezometers casagrande standpipe piezometers are a simple and economic method for measuring groundwater pressures in soil and rock. Simplified users guide to timedomainreflectometry monitoring of slope stability figure 4basic tdr system components. The pump features one convenient dial for reversible flow and sampling flow rates from 40 mlmin to 3. They are typically sealed in boreholes but can also be embedded in fills, or suspended in a well. In some cases, the stability andor durability of the existing embankment fill may be questionable because the fill materials are suspect or because slope instability in the form of raveling, downslope lobes, or slope failures have been observed during the site reconnaissance phase. Special specification 5990 vibrating wire and standpipe. Stability and movements of openpit lignite mines in northern. Ask the regional maintenance engineer about any stability erosion problems with the existing cut slopes.
For example, a standpipe piezometer is a reliable indicator of porewater pressure in soil with high. This kind of filter is standard with most piezometers and is known as an lae filter, to distinguish it from an hae filter. Simplified users guide to timedomainreflectometry monitoring of slope stability figure 9 identifies the beginning and end of the cable. Based on conventional slope stability studies bishop.
Installation of piezometers shall be coordinated with the placement location and schedule for all monitoring instrumentation and wick drains as indicated. The end or any break in the cable is when the signal goes up dramatically. It is essential that the engineering geologist be intimately familiar with all of these methods because they provide ways of determining, relatively unambiguously, whether a. The piezometer string and grout pipe are placed in the borehole and cementbentonite grout is pumped until the borehole is filled. The valdez marine terminal was constructed between 1974 and 1977 at the southern end of. The 601 tip connects to the surface with 34 id pvc riser pipe using slipfit couplings. Geological cross section of model slope showing core borings and piezometers table 1. Stability of underwater slopes realized by means of a suction dredger.
Monitoring pore pressures to check the performance of earth fill dams. A technique for the calculation of slope stability based upon the assumption of a plane surface of failure through the toe of the slope has been proposed by culmann see taylor, 1948. Some embankments constructed of material that is susceptible. The recommended layout for a monitoring system, types and design of piezometers, data collection and use of the pore pressure data are presented. The aims of slope stability analyses are to understand the development and form of natural slopes and the processes responsible for different natural features. Piezometers and water pressure cells were placed at a safe sp. Chapter 10 soil cut design washington state department of. Pdf groundwater and associated pore pressure represent elements. Monitoringporewaterpressuresto determine slope stability. In cases where the stability failure mode is not well modeled by limit equilibrium techniques, a more sophisticated analysis may be necessary using finite elementdifference methods such as the computer program flac. The beginning is where the signal becomes more or less stable.
Instrumental record of debris flow initiation during. Monitoring dewatering systems and wick drains at construction sites. Vibrating wire piezometers are the electrical piezometers of choice as the frequency output of vibrating wire devices is immune to external electrical noise, and able to tolerate wet wiring common. Cable tester a cable tester that has been used successfully for slope stability tdr measurements is the tektronix metallic timedomain reflectometer model 1502b. A seepage cutoff such as a clayfilled trench may be constructed through a sand layer to slow the seepage and lower the piezometric elevation under the downstream slope as shown in figure 3. Unsaturated and transient seepage analysis of san luis dam. Long range displacement transducers survey the movements of the slope, while special piezometers and temperature sensors, designed to withstand the high temperatures and acidic conditions, monitor the temperatures and water levels at depths of up to 50 m. Chapter 9 embankments washington state department of. They are certainly major factors in cut slope stability and in the stability of fill slopes involving both internal and external slope failures. Solinst also offers the model 615 stainless steel drivepoint piezometer, which is designed to be pushed into the soil below the bottom of a borehole. Piezometers measure pressure the measurand and are used to confirm pore water pressure andor ground water levels which are used in several calculations computations to quantify other parameters which influence the performance of soil and rock.
Slope stability is influenced by many factors, among which are subsoil structure and pore water pressure distribution. Use of inclinometers for geotechnical instrumentation on. Stability of underwater slopes realized by means of a. Sometimes referred to as pwp, pore water pressure is one of the major parameters to be measured when monitoring the slope stability of any earthen mass and is vital in calculating the stress state in the ground soil mechanics pore water pressure can be measured through water level measurement, pneumatic piezometry and vibrating wire piezometry. Instrumentation for slope stability semantic scholar. How do friction and cohesion work together to stabilize slopes. The effect of gravity is known, therefore, water is the key factor in assessing slope stability.
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