Sustainable Thoughts in Ground Improvement and Soil Stability

Preservation of monuments all around the world and increasing their stability against earthquakes is a matter of great importance. Main purpose of the present study is to investigate the dynamic characteristics of the underground monuments at the ancient sites in Alexandria, Egypt (Catacomb of Kom El-Shoqafa, El-Shatbi Necropolis, and Necropolis of Mustafa Kamil, Amd El-Sawari site (Serapium and ancient library)) and identify the main damage mechanism, in order to evaluate the risk of structure damage or collapse in case of future events using microtremors recordings. Array measurements at three sites in the city of Alexandria were performed to estimate the Vs velocity of soil/rock formations for site effect analysis. Our study includes a detailed geological and geotechnical survey of the areas, measurement, analysis and interpretation of ambient noise data using the refraction microtremor (ReMi) method.

A thorough assessment of shallow shear velocity is important to both earthquake-hazard assessment and efficient foundation design. The only standard procedure for determining shear velocity, crosshole seismic (ASTM D4428), requires at least two boreholes with high-precision positional logs. The refraction microtremors method is based on recording ambient ground noise on simple seismic refraction equipment (as in ASTM D5777). Wave field analysis of the noise allows picking of Rayleigh-wave phase velocities. It works well in dense urban areas and transportation corridors.

The shear velocities estimated from ReMi method is a fast commercial effective method as borehole velocities for estimating 30- m depth-averaged shear velocity for foundation design and other purposes.

The importance of soil shear wave velocity (Vs) can not be over emphasized in engineering work. Because of its vital importance, many field and lab techniques have been devised to obtain soil Vs including, SPT, CPT, SCPT, P-S logging, suspension logging, cross-hole, seismic refraction and reflection (e.g. Imai 1981; Japan Road Association 1990; AIJ 1993; Kramer 1996). All of these techniques are inaccurate, costly, intrusive (require boring), laborious, time-consuming, or not urban-friendly.

Current commonly used techniques of estimating shallow shear velocities for assessment of earthquake site response are too costly for use in most urban areas. They require large sources to be effective in noisy urban settings, or specialized independent recorders laid out in an extensive array. The refraction microtremor (ReMi) method overcomes these problems by using standard P-wave recording equipment and ambient noise to produce average one-dimensional shear-wave profiles down to 100 m depths. The combination of commonly available equipment, simple recording with no source, a wave field transformation data processing technique, and an interactive Rayleigh-wave dispersion modeling tool exploits the most effective aspects of the microtremor, spectral analysis of surface wave (SASW), and multichannel analysis of surface wave (MASW) techniques. The slowness-frequency wave field transformation is particularly effective in allowing accurate picking of Rayleigh-wave phase-velocity dispersion curves despite the presence of waves propagating across the linear array at high apparent velocities, higher-mode Rayleigh waves, body waves, air waves, and incoherent noise. It has been very effective for quickly and cheaply determining 30-m average shear wave-velocity (V30).

Use of “active source” methods such as seismic reflection and refraction. In geotechnical applications in particular, seismic refraction with surface seismic sources has gained widespread acceptance as a viable investigation tool (Whiteley 1994). The effectiveness of this approach, especially in urban situations, is limited by the presence of seismic noise and in the choice of a source with sufficient energy to achieve the required depth penetration. Additionally, the seismic refraction method is inherently “blind” to the presence of a velocity inversion (Whiteley and Greenhalgh 1979).

An alternative approach is to use “natural” microtremors (the “noise” in traditional seismic surveying), as a source of wave energy. The measurement of high-frequency seismic noise, or microtremors, is a well-established method of estimating the seismic resonance characteristics of relatively thick (tens of metres and above) unconsolidated sediments. This approach is described by Nakamura (1989), where the fundamental resonance period (TS) of a site can be obtained from surface waves and used in the assessment of potential seismic hazard to structures founded in soft soils.

The refraction microtremor technique is based on two fundamental ideas. The first is that common seismic refraction recording equipment, set out in a way almost identical to shallow P-wave refraction surveys, can effectively record surface waves at frequencies as low as 2 Hz. The second idea is that a simple, two-dimensional slowness-frequency (p-f) transform of a microtremor record can separate Rayleigh waves from other seismic arrivals, and allow recognition of true phase velocity against apparent velocities.

Two essential factors that allow exploration equipment to record surface-wave velocity dispersion, with a minimum of field effort, are the use of a single geophone sensor at each channel, rather than a geophone “group array,” and the use of a linear spread of 12 or more geophone sensor channels. Single geophones are the most commonly available type, and are typically used for refraction rather than reflection surveying. The advantages of ReMi from a seismic surveying point of view are several, including the following: It requires only standard refraction equipment already owned by most consultants and universities; it requires no triggered source of wave energy; and it will work best in a seismically noisy urban setting. Traffic and other vehicles, and possibly the wind responses of trees, buildings, and utility standards provide the surface waves this method analyzes.

One of the major problems related to civil engineering structures is that of ground movements with amplitude ranges from a few millimeters to a few meters. Soil treatment by vibroflotation is a recent technique for improving soil with poor geo-mechanical properties. In addition, this treatment minimizes the risk of liquefaction and settlement. This Article is interested to establish diagnostic and monitoring of vibroflottation works, basing on the results of SPT tests, laboratory tests and quality control as well as the details of bathymetric and the properties of seabed soils before and after treatment. On the other hand, the work consists in making a in-situ monitoring using topographic hardware carried out on the treated soil, in order to verify its influence on the stability of the vertical breakwaters. The tests results will be compared with in-situ measurements.

Aging of the asphalt cement in the pavement changes the quality of asphalt concrete from flexible to stiff and the pavement will be susceptible to all types of distresses. Recycling is considered as a good alternative to enhance the pavement for additional service life. Recycling agent can provide the required flexibility and increase its micro crack healing potential. In this investigation, aged asphalt concrete was recycled with two types of additives, carbon black CB and styrene Butadiene rubber SBR. Two set of Cylindrical specimens have been prepared, the first set has 102 mm diameter and 63.5 mm height while the second set has 102 mm diameter and 102 mm height. The first set was subjected to repeated indirect tensile stresses (ITS) at 25 °C and tested under stress level of 138 kPa, while the second set practices repeated compressive stresses (CS) at 40 °C and tested under three stress levels of (69, 138, and 207) kPa. All the specimens were tested in the pneumatic repeated load system PRLS and constant loading frequency of 60 cycles per minute. The loading sequence for each cycle is 0.1 s of load duration and 0.9 s of rest period. After 1000 load repetitions which allowed for the initiation of micro cracks, the test was terminated. Specimens were stored in an oven for 120 min at 60 °C to allow for crack healing by external heating. Specimens were returned to the PRLS chamber and subjected to another cycle of stresses repetition. The impact of crack healing was measured in terms of the change in Resilient Modulus Mr under ITS and permanent deformation under CS before and after healing for each recycling agent. It was concluded that Mr under repeated ITS increases by (25, 30, and 20) % for aged, CB treated and SBR treated mixtures respectively after healing. On the other hand, the permanent deformation under repeated CS decreases by (31, 43, and 45) %, (6, 49, and 10.6), (19, 24.5, and 13.2) % for aged, CB treated and SBR treated mixtures under stress levels of (69, 138, and 207) kPa respectively after healing.

The subgrade soil is the foundation for the roadway structure, its responsibility is to provide the required stability for the overlaying pavement and to limit the deformation due to traffic load repetitions by furnishing homogeneous stress distribution layer. Asphalt stabilization technique is usually used to control and improve poor subgrade soil condition. In this work, the unconsolidated undrained Triaxial test was implemented for comparatively assessing the impact of asphalt stabilization on shear strength and stiffness of asphalt stabilized subgrade soil. Soil samples have been treated with cutback asphalt using various water and liquid asphalt percentages. The loose asphalt stabilized soil samples were subjected to aeration periods ranging from one to five hours at room temperature of 20 ± 2 °C before compaction. Cylindrical Specimens with height and diameter of (77.4 and 38) mm respectively have been prepared in the laboratory after aeration periods using static compaction to achieve a target density. The compacted Specimens have been subjected to curing at room temperature of 20 ± 2 °C for a curing period ranging from seven to ninety days, then tested in the Triaxial apparatus to determine the shear strength and modulus of elasticity properties. Data were analyzed and compared. It was concluded that the optimum aeration period was two hours while the reasonable curing period is seven days. It was observed that the shear strength and the modulus of elasticity increases by (211 and 251) % respectively with increasing cutback asphalt percentage up to 8% asphalt content, as compared with natural soil. It was concluded that the effect of variation in fluid content in the range of 0.5% above or below the optimum has increased the shear strength by (663, and 662) % respectively as compared with natural subgrade soil.

The construction of Rockfill Embankments, although considered as a process of low difficulty, it presupposes the compliance of the design study with rigorous specifications. In this regard, a meticulous and systematic method of construction is required to ensure the optimum performance of this type of geostructure. In this paper, some basic requirements concerning the design and construction of rockfill embankments, as well as some engineering recommendations for a successful construction, are presented and commented. Advantages and weaknesses of rockfill embankment, in comparison to the traditional earthfill structures are also illustrated and the relevant fields of application are defined. Finally, a case study, dealing with the construction of a high motorway geostructure, consisting of crushed rock material at its lowest part and of reinforced earthfill at the top, is briefly presented.

The southwest area of Khoy County, in the Northwest of Iran, due to geological conditions and its location in Sanandaj-Sirjan geological zone, is one of the hazardous regions regarding to landslides. Geology formations of this area are consisting of sedimentary, metamorphic and volcanic rocks. In this paper, first, the geological characterizations of the study area have been presented, and then the instable slopes are introduced. The reasons of slopes instability have been discussed. The main factors of slope instabilities in this area are groundwater, rock weathering, dynamic shocks and road/railway construction are known. In this paper, the conditions and factors (characterizations) of landslide activity have been analyzed. In south west of Khoy, some landslides in road slopes occur after heavy rainfalls. There are some historical landslides along roads slopes and rural residential areas. Main historical landslide is Gougerd in the south of the Avrin Mountain. The mechanism of most landslides in soil slopes are rotational, the depth of slide surface is ranging from 3 to 45 m. The height road slope slides reaches to 50 m and in mountain areas reach 1100 m. The results showed that the main factors of landslides are precipitation and groundwater table rising, erosion of slope foot by the rivers and dynamic loads such as of railway and road traffic.

In this research, it was aimed to investigate the potential landslide induced by spillway construction activities at Durhasanlı reservoir site located in Manisa province of Turkey and provide a feasible stabilization measure. Since the site reconnaissance revealed that some deformations on spillway concrete members and the development of tension cracks at the head of hillside on the right bank of spillway, five inclinometers were immediately placed at critical points and the possible slope movement was observed for 40 days. It was found out that the mass movement were going on at a rate of about 0.1 mm per day. With the help of inclinometers’ data, the depth of sliding mass was also determined. Accordingly, based on geotechnical properties obtained from surface and subsurface investigations, a number of slope stability analyses were carried out taking into account such factors as the tension cracks, earthquake loading, reduction of slope weight and pile reinforcement. As a result, the secured solution for the stability of mobilized slope was suggested by terracing the hillside, pile reinforcement, and effective drainage system.

India’s present energy need from coal reserves contribute about 55% of the total power generation. Indian coal has high ash contents and presently about 200 million tonnes of ash is generated annually. The generated ash has become a subject of worldwide interest in recent years because of its diverse uses in manufacture of cement, bricks and concrete block, filling of underground cavities, mine voids etc. The present ash utilisation is about 69% and the balance ash is stored safely in ash ponds. The utilization of ash is strongly related to economy of its use, which changes with time. There may not be users in sight today, but after some time there could be bulk users.

The most economic and commonly used method to dispose ash is by hydraulic transport, in the form of slurry, to the ash pond. At the ash pond, storage space is created by constructing dyke embankments all around, within which ash particles will be allowed to settle and the decanted water is allowed to escape for recirculation back to plant. Based on the type of the soil available for the embankment construction, mostly, it is a homogeneous section with internal drainage arrangement of sand chimney and sand blanket. The dyke embankments are designed as water retaining structures as per relevant Indian Standards applicable for earth dams. For internal drainage in these embankments, natural river sand or crushed stone sand is generally used. To create sustainable and environment friendly infrastructure, NTPC has recently explored the use of bottom ash as filter material with respect to pond ash as base material. Based on laboratory tests, it is found that bottom ash possess the required filter ability, internal stability, drainage capacity, self healing properties and does not segregate. Accordingly, bottom ash has been adopted as an alternate filter material in internal drainage system of dyke embankments of various plants of NTPC. The above have been successfully implemented and found to be safe under operating phase. This use of bottom ash as a filter material has also saved the time and cost over runs and most importantly is echo- friendly.

This paper highlights the use of bottom ash as filter material in water retaining structures such as dyke embankments/earth dams in a sustainable manner to entire world.

This keynote paper focuses on the long-term settlement (creeping) of highly compressible soils, considering also soft sludge. Long-term oedometer tests lasted up to 42 years and were performed on silty sand, (organic) clayey silt, peat and (pre-treated) sewage sludge. Secondary consolidation (creep) could be observed in all cases, lasting over many years and occurring widely linear with the logarithm of time. However, temporary acceleration may also be observed, indicating a discontinuous nature of internal deformations due to accelerated rearrangement in the fabric – mainly in very soft soils with peaty components. This long-term phase is followed by tertiary creeping with a long lasting fading out period. In both phases microcrystalline sliding occurs.

In addition to the laboratory tests results of comprehensive field measurements are summarized, showing the influence of different ground improvement methods on the creeping behaviour of highly compressible fine-grained soils (partly organic). Most data were collected from a highway junction with embankments on very soft, heterogeneous ground (locally 15 m deep and with a natural water content up to 1000%), constructed between 1972 and 1974, and monitored since. Different ground improvement methods were compared, disclosing details of primary, secondary and tertiary settlement: Deep dynamic compaction/consolidation (heavy tamping), vibro-flotation (piled embankments), temporary surcharge loading, and local combinations of the previous methods, including also vertical drains.

The authors previously published two papers to study the influence of using non-standard hammer-weight (W_i) on the obtained blow counts, (N_i) during the SPT test. The current study is an extension to the past work; here the hammer drop height (H_i) has been changed to investigate its effect on the obtained blow counts, (N_i). Then, the multiple action of changing non-standard energy (W_i.H_i) is also investigated. The hammer weight, its drop height and the machine efficiency ( ) present the three main variables during the study.

The study methodology is experimental work and the method is physical model simulates the behavior of SPT-Rig. It has been designed and manufactured in house. The model is capable to change the hammer weight, its drop height and the overall machine efficiency. Five hammer weights, five drop heights and six different efficiencies have been changed all together; individually as well as in groups. The hammer weight ratios (W_i/W_s) and drop height ratios (H_i/H_s) each has been changed to cover the spans of 0.2, 0.4, 0.6, 0.8 and 1.0. Furthermore, six efficiencies ( ) have been changed with every change of the above ratios to cover the scope of,  = 35%, 50%, 60%, 70%, 85% and 100%. Reconstituted well graded clean silicate dense sand (SW) is used for modeling the soil.

Novel procedure has been advised as well as empirical equations have been proposed to re-adjust the incorrect blow counts (N_i) obtained using non-standard SPT parameters or uses machines of a low efficiency. Also, a simplified method fast and costless has been suggested to sort out the problem of machines owing low efficiencies. Finally, some modifications to well-known formula are advised.

Friction losses are short term losses in Post-Tensioned systems. The friction created at the interface of tendons and ducts during the stretching of a curved or straight tendon in a post-tensioned member leads to a drop in the prestress along the member from the stretching end. The purpose of this research is to study the friction losses between tendons and plastic ducts. Moreover, it has been shown that “corrugated steel ducts will fracture at cyclically opening cracks across the duct. Plastic ducts have been shown to perform better under similar conditions” [2]. This proves that plastic ducts are good ducts in durability and corrosion protection. Thus, the friction parameters for plastic ducts system will be evaluated in this research paper. The analysis results presented that the average wobble coefficient and the average curvature one for plastic ducts of 0.005/m and 0.1/rad, respectively, which are less than the values for steel ducts. Plastic ducts reduce the friction losses to 41% in comparison with the steel ducts at site work. In addition, plastic ducts reduce the friction losses to 33% in comparison with the steel ducts at laboratory work as presented in this paper. The values of (k) and (μ) for only metal sheathings, rigid metal ducts, and other types are introduced in PCI (Fig. 2)³. The primary goal of this research was to conduct an experimental evaluation of the friction losses between post-tensioned strands and plastic ducts. Moreover, in the (Fig. 14) below, the values of (k) and (μ) for only metal sheathings, rigid metal ducts, and other types are introduced [3]. In this research, the values for (k) and (μ) will be evaluated for plastic ducts in order to introduce values for (k) and (μ) for plastic ducts in the (Fig. 2).

Present study discusses the behavior of an anchored sheet pile wall supporting a wide excavation based on the analysis using a computational tool based on the finite element method. The soil is modeled using the Mohr-Coulomb material and the sheet pile wall is modeled using the plate elements. A parametric study using numerical modelling is performed to investigate the behavior of an anchored sheet pile wall. The anchoring system is modeled by a combination of connectors (which do not interact with the soil) and geo-grids (which do interact with the soil and are used to account for grouting). The stability of the structure assessed using Strength Reduction Method and factor of safety for various combinations are calculated in the upper and lower bounds analysis. Results obtained from the parametric study indicate that the embedded depth of sheet pile wall, positioning of anchor, and length of anchors, inclination of the anchor govern the overall stability of structures studies in the present study. Moreover, the present study captures the failure modes of the anchored sheet pile wall system with the inclusion of multiple complex interfaces and supports conditions.

Soil reinforcement using Geogrid in the retaining wall is used to strengthen the overall structure to improve the stability of the retaining wall system as well as the behavior of the structure under the seismic loading. With reference to the construction of a conventional rigid retaining wall, the provision of geogrid reinforcement is much appreciated in terms of the performance of the overall structure. Modular (segmental) blocks are used for the construction of such geosynthetic-reinforced soil retaining walls. Such structures offer a wide range of aesthetic finishes, while resulting in more economical structures compared to conventional rigid retaining walls. The present study discusses the effect of the provision of geogrid length in multiple layers on the stability of reinforced retaining wall using numerical modeling under the gravity and seismic loading conditions. This study further investigates the development of a number of failure modes of reinforced soil wall with varying geogrid length configuration. It is established that variation in the length of geogrid not only increases the factor of safety of the wall system but also modifies the failure mode of the reinforced soil retaining wall.

Plate anchors play a significant role in the stabilization of various geotechnical structures. In recent years, the use of helical anchors has extended beyond their traditional use in the foundations. Faster installation and instant loading capabilities have increased their use in multiple infrastructure applications. Through the past few decades, researches have been carried out many studies to determine the pull-out capacity of plate anchor, which has led to the development of many analytical solutions. Unfortunately, the current understanding of helical anchors is unsatisfactory to lay the appropriate framework to be followed by practicing engineers. To have an economic and safer design which leads to increased confidence in design, this study is aimed to use numerical modeling techniques to understand the behavior of helical anchors in the sand and their failure mechanism. Subsequently, the present study focuses on the numerical investigation of pullout capacity of helical anchors with the consideration of various important parameters like embedment depth (H) and anchor plate diameter, D provisioned in the sands of the wide range of relative density i.e. loose, medium and dense sand. It is noted from the results of the present study that the pullout capacity of an anchor provided at sufficiently high value of embedment ratio (H/D) is in excellent agreement with the exact solution proposed by previous researchers. Moreover, a numerical analysis using finite element method with consideration of upper and lower bound limit analysis is carried out for the evaluation of the pull-out capacity of plate anchor (q_u) in multi-layered sand deposit and the variation of q_u with H/D ratio is also presented. Furthermore, the associated failure mechanism of the plate anchors is also analyzed and discussed thoroughly in the present work.