Journal of Geotechnical and Geoenvironmental Engineering

Pile jacking is a piling technique that provides a noise- and vibration-free environment in the construction site. To improve termination criteria for pile jacking and to better understand the behavior of jacked piles, two steel H piles were instrumented, installed at a weathered soil site, and load tested. A set of termination criteria was applied to the test piles, which includes a minimum blow count from the standard penetration test, a specified final jacking force, a minimum of four loading cycles at the final jack force, and a specified maximum rate of pile settlement at the final jacking force. The two test piles passed all required acceptance criteria. Punching shear failure occurred at the failure load for both piles and the shaft resistance consisted of approximately 80% of the pile capacity. Based on the results of field tests in Hong Kong and Guangdong and several centrifuge tests, a relation between the ratio of the pile capacity $P_{\mathrm{ult}}$ to the final jacking force $P_J$ and the pile slenderness ratio is established. The $P_{\mathrm{ult}}∕P_J$ ratio is larger than 1.0 for long piles but may be smaller than 1.0 for short piles. A regression equation is established to determine the final jacking force, which is suggested as a termination criterion for jacked piles. The final jacking force can be smaller than 2.5 times the design load for very long piles, but should be larger than 2.5 times the design load for piles shorter than 37 times the pile diameter.

Compared to geosynthetic-reinforced soil (GRS) retaining walls, GRS abutment walls are generally subjected to much greater intensity surface loads that are fairly close to the wall face. A major issue with the design of GRS abutments is the allowable bearing pressure of the bridge sill on the abutments. The allowable bearing pressure of a bridge sill over reinforced soil retaining walls has been limited to $200\mathrm{kPa}$ in the current NHI and Demo 82 design guidelines. A study was undertaken to investigate the allowable bearing pressures of bridge sills over GRS abutments with flexible facing. The study was conducted by the finite element method of analysis. The capability of the finite element computer code for analyzing the performance of GRS bridge abutments with modular block facing has been evaluated extensively prior to this study. A series of finite element analyses were carried out to examine the effect of sill type, sill width, soil stiffness/strength, reinforcement spacing, and foundation stiffness on the load-carrying capacity of GRS abutment sills. Based on the results of the analytical study, allowable bearing pressures of GRS abutments were determined based on two performance criteria: A limiting displacement criterion and a limiting shear strain criterion, as well as the writers’ experiences with GRS walls and abutments. In addition, a recommended design procedure for determining the allowable bearing pressure is provided.

Objects placed on the seabed sink in because of the momentary liquefaction of the seabed due to wave loading. The depth of the momentary liquefaction depends on the pore pressure propagation which is governed by wave and seabed properties. A large-scale one-dimensional experimental investigation program was carried out with particular attention given to the momentary liquefaction of the seabed. Approximately a $1.4\mathrm{m}$ thick sand bed and a $1.1\mathrm{m}$ of water column above the sand bed were subjected to a series of waves. The experimental variables were sand bed density, degree of saturation, dynamic pressure amplitude, and frequency of wave loading. The measured pore pressure response within the sand bed was found to attenuate with significant phase lag, which increased the likelihood of the momentary liquefaction. Pore pressure response at a particular location within the sand bed was found to increase with an increase in wave period, an increase in degree of saturation, and an increase in permeability of the sand bed. With other parameters remaining the same, the likelihood of the momentary liquefaction of the seabed increases with decreasing wave period, decreasing degree of saturation, and decreasing permeability of the seabed. An object placed on the sand bed was found to progressively sink into the momentarily liquefied sand bed. The rate of sinking of the object during loading and unloading phases of waves was measured and discussed.

Seasonal deformation of unsurfaced roads was observed over several years and was studied using pavement deterioration models and finite-element analysis. The Mathematical Model of Pavement Performance is a model designed for pavement deterioration prediction and was successfully used for seasonal deterioration modeling because of its flexibility in defining the pavement structure, properties, and seasonal impact. However, these types of models are designed for highways and are somewhat limited in soils characterization and manipulation of the forces at the road–tire interface. Therefore, a three-dimensional dynamic finite-element model of a wheel rolling over soil was applied to simulate local vehicle traffic on a secondary unpaved road. These simulations were used to study the effects of vehicle speed, load, suspension system, wheel torque, and wheel slip on rutting and washboard formation. Modeling results are compared to field measurements and observations.

This paper documents a novel filtration technology that incorporates low-stiffness filter matrix particles. The application of isotropic stresses leads to the compression of particles and ensuing pore throat size reductions in the filter matrix. The filtration capacity of the matrix is improved with increasing confinement because the retention of filtrate particles increases due to particulate plugging and bridging on the reduced pore throats. Conversely, relaxing the applied stresses renders system expansion, increased pore throat sizes, and enhanced flushing of entrapped particles from the filter. Experimental results indicate that this technology is most efficient in cases where particle retention occurs due to geometrical constraints (i.e., bridging); however, the system can also render filtration by surface deposition due to the net electrical attraction between the filtrate and filter. Experimental results are analyzed by considering particle-scale filtration mechanisms.

Leachate levels within a landfill must often be controlled for environmental and/or regulatory reasons by means of pumping from wells. Conventional vertical wells are usually used for this purpose, but there is a perception that they are inefficient. In this paper, the feasibility of using directional drilling to install horizontal wells for leachate control in landfills is investigated with reference to pilot and full scale field trials at Rainham, U.K. The difficulties of well-screen design and installation in a landfilled waste are discussed; the insights gained during trial installation are described; and the effectiveness of three trial wells is assessed with reference to the leachate flow rates and drawdowns achieved, in comparison with conventional vertical wells. It is concluded that the drilling rig used must be sufficiently powerful to cope with the likelihood of at least partial borehole collapse around the well-screen during installation; that the screen slot size can be based on at least the $D_{30}$ particle size of the waste and a natural filter allowed to develop around the well (provided that the resulting well screen is strong enough); and that as experience with the technology grows, directionally drilled horizontal wells could represent a viable, cost effective alternative to conventional vertical wells for leachate control in landfills.

This paper describes the experimental methods developed to understand the self-healing or progressive erosion of core cracks in earth dams. Concentrated leaks through two types of core cracks are simulated experimentally in flow cells of different configurations. Results of experimental investigations indicate that the current empirical filter criterion for base soils with fines content more than 85%, which stipulates that $(D_{15F}∕d_{85B})$ should be less than 9, is conservative. However, analysis of experimental results suggests that the $(D_{15F}∕d_{85B})$ ratios can not indicate the rate of self-healing or progressive erosion. It also leads to a conclusion that mechanistic understanding, rather than another improved empirical criterion, may be needed for quantitative prediction of self-healing or progressive erosion. In this study, we identified two groups of quantitative parameters influencing the mechanism of self-healing: (1) characteristics of base soils and filters, and (2) hydraulic, geometric, and physicochemical conditions. Experimental methods are presented to evaluate these parameters for which no standardized methods are reported in the current literature.

This paper describes a mechanistic model developed to understand the self-healing mechanism of two types of cracks in impervious cores of earth dams; Type A core cracks which extend from the interior of the core to the downstream filter, and Type B core cracks which extend from the upstream face of the core to the downstream filter. The base soil-crack-filter system is idealized using a four-element one-dimensional continuum to consider various processes in the core and the filter. The model is numerically implemented to predict self-healing in the idealized domain. The model predictions are validated using results from experimental investigations. A parametric study conducted with the model indicates two conditions essential to foster self-healing: a nominal erosion of the base soil, and a seepage velocity in the filter that is less than its critical seepage velocity. This study suggests that the mechanism leading to different rates of self-healing is the interplay of several parameters, viz, characteristics of base soils and filters, geometrical features of cracks, hydraulic conditions, etc. Application of the one-dimensional mechanistic model to a three-dimensional field-scale scenario is demonstrated.

This paper presents the results of a systematic well designed experimental investigation carried out to study the engineering properties of the soft Bangkok clay heated up to $90°\mathrm{C}$ from room temperature $(25°\mathrm{C})$ . Details of modified oedometer and triaxial test apparatus that can handle temperatures up to $100°\mathrm{C}$ are also presented. In the range of temperatures investigated, soft Bangkok clay exhibited temperature induced volume changes that depend mainly on the stress history, reduction in the conventional elastic zone, stiffening, and increased hydraulic permeability with increasing temperature as well as apparent overconsolidation state after subjecting the normally consolidated specimen to heating/cooling cycle. The results of this study provide additional data that can enhance the understanding of the thermohydromechanical behavior concepts of saturated clays.

Seismic site response analysis is typically performed using a suite of rock acceleration-time histories prescribed at the base of a soil column and propagated to the ground surface. To develop statistically stable estimates of the site response, a large number of input motions are required. Alternatively, random vibration theory (RVT) can be used to predict statistically stable estimates of the surface response spectrum in one analysis without the need to prescribe the input rock motion in the time domain. Thus, the critical and time consuming activity of choosing appropriate input ground motions and fitting them to a target spectrum is avoided. This paper describes the RVT approach, its analytical background and input requirements, and provides a site-specific validation of the procedure against traditional site response predictions. The single-corner frequency Brune source spectrum is used in the RVT procedure to describe the input motion in the frequency domain. RVT site response predictions using the Brune spectrum as input are compared with those from traditional site response analyses that incorporate different suites of input rock motions. Results indicate that RVT site response analysis can provide a response spectrum that is similar to the median response spectrum from analyses performed using a suite of input rock motions. However, the favorable comparison is obtained only when the seismological parameters used to describe the RVT input motion are carefully chosen to be consistent with the suite of input rock motions.

Two commonly encountered saprolitic soils in Hong Kong, weathered volcanic tuff (WT) and weathered granite (WG), were studied using high-quality intact samples. The intact samples exhibited quasi-preconsolidation pressure or yield stress under isotropic compression due to their bonded structures, but the yield was progressive and not abrupt. As the stress increased, significant volumetric changes were measured. These changes resembled clay-type behavior. The soils also exhibited anisotropic deformation under isotropic loading and unloading, which was associated with the features of their parent rocks. During the drained tests, shearing at the in situ stress-state produced peak strength and volumetric dilation. Undrained shearing showed complicated stress paths and dilatancy behavior in these soils. Phase transformation states and dilative shear failure were readily seen, which resembles typical sand-type behavior. Distinct shear band(s) appeared in the WT specimens during shearing, whereas a bulging type of failure appeared in the WG specimens. The soils ultimately approached the corresponding state guided by a unique critical state line, regardless of their complex initial states in relation to the bonded structure and drainage conditions.

The present study was undertaken to compare the capabilities of four of the known methods; more specifically, ${\mathrm{N}}_2$ adsorption, methylene blue (MB)-titration, MB-spot test, and ethylene glycol monoethyl ether (EGME) methods were evaluated to determine the specific surface area (SSA) of 16 different clayey soils. The study showed that ${\mathrm{N}}_2$ adsorption method underpredicts the SSA of soils, especially for smectitic soils. No significant differences were observed between ${\mathrm{N}}_2$ SSA, MB SSA-titration, or MB-spot test for kaolinitic soils. The SSA estimates of MB-titration and MB-spot test methods were highly correlated for all soils. The EGME method has a very different procedure from the MB methods; however, it was highly correlated with MB methods $(r^2=0.95)$ . The ${\mathrm{N}}_2$ adsorption method had no correlation to other methods. The cation exchange capacity of tested soils was highly correlated to the SSA, as high as $r^2=0.77$ . No unique relationship was determined between the clay fraction and SSA.

A vertical drain radial consolidation equation based on a parabolic reduction in permeability toward the drain is presented. The proposed equation, based on Hansbo’s equal strain theory, is compared with settlement data from a laboratory test in a large scale consolidometer.

In this study, the extent of the smear zone and the reduction of permeability and water content within the smear zone were investigated using a large-scale consolidometer. The installation of vertical drains by means of a mandrel causes significant disturbance of the subsoil surrounding the mandrel, resulting in a smear zone. The extent of the smear zone for Moruya clay (New South Wales, Australia) was estimated on the basis of normalized permeability and the reduction of water content by taking undisturbed samples (horizontally and vertically) at different locations. This study reveals that a significant reduction in water content and horizontal permeability takes place towards the drain, whereas the variation in the vertical permeability is negligible. The smear zone for Moruya clay was found to be 2.5 times the equivalent radius of the mandrel with the horizontal permeability varying from 1.09 to 1.64, an average of 1.34 times smaller than that of the undisturbed zone. Finally, a correlation between the permeability decrease and water content reduction within smear zone is proposed.