Lateral Ground Research Articles

Differential leg function in a sprawled-posture quadrupedal trotter

Legs of sprawled-posture, quadrupedal trotting geckos (Hemidactylus garnotii) each functioned differently during constant average-speed locomotion. The center of mass decelerated in the first half of a step and accelerated in the second half, as if geckos were bouncing in fore-aft and side-to-side directions. Forelegs decelerated the center of mass only in the fore-aft direction. Hindlegs provided all the acceleration in the latter half of the step. Lateral ground reaction forces were always directed toward the midline and exceeded the magnitude of fore-aft forces. The differential leg function of sprawled-posture geckos resembled sprawled-posture hexapods more than upright-posture quadrupeds. The pattern of leg ground reaction forces observed may provide passive, dynamic stability while minimizing joint moments, yet allow high maneuverability. Integrating limb dynamics with whole body dynamics is required to resolve the trade-offs, if any, that result from stable sprawled-posture running with differential leg function.

Distributions of ground movements parallel to deep excavations in clay

An empirical procedure for fitting a complementary error function (erfc) to settlement and lateral ground movement data in a direction parallel to an excavation support wall is proposed based on extensive optical survey data obtained around a 12.8 m deep excavation in Chicago. The maximum ground movement and the height and length of an excavation wall define the erfc fitting function. The erfc fit is shown to apply to three other excavation projects where substantial ground movement data were reported.Key words: excavations, clays, ground movements, performance data.

Simulation models of human vertical jumping: case settled?

Professional dancers sustain a high number of injuries. Epidemiological studies have suggested that performing on inclined “raked” stages increases the likelihood of injury. However, no studies have examined if biomechanical differences exist between inclined and flat surfaces during functional tasks, such as landing from a jump. Such differences may provide a biomechanical rationale for differences in injury risk for raked stages.Eight professional dancers performed drop jumps from a 40 cm platform on flat and inclined surfaces while forces, lower extremity kinematics, and electromyographic activity were collected in a controlled laboratory environment.Dancers landed on the laterally inclined surface with significantly higher knee valgus (4°), peak knee flexion (9°), and medial–lateral ground reaction force (GRF) (13.4% body weight) compared to the flat condition. The posterior GRF was higher in the anterior inclined condition compared to the flat condition. In the anterior inclined condition, subjects landed with 1.4° higher knee valgus, 4° more plantarflexion at initial contact, and 3° less dorsiflexion at the end of landing.Biomechanical variables that have been suggested to contribute to injury in previous studies are increased in the inclined floor conditions. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.

Kinetic asymmetry in female runners with and without retrospective tibial stress fractures

Gait asymmetry may be linked to the tendency for runners to sustain chronic overuse injuries. This paper compares gait asymmetry in female runners who have never sustained a running-related injury to those who have sustained unilateral tibial stress fractures. The symmetry index was used to characterize asymmetry in the kinetics of both subject groups. There were three aims to this study: (1) to report natural levels of asymmetry for healthy, never-injured female runners, (2) to compare asymmetry levels between never-injured runners and those who have sustained stress fractures, and (3) to examine the kinetics between the involved and uninvolved limbs of runners who have sustained stress fractures. In all three aims, peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and peak instantaneous vertical loading rates, and peak shock were examined. In the never-injured runner group, natural levels of asymmetry ranged from 3.1% for peak vertical ground reaction force up to 49.8% for peak lateral ground reaction force. Symmetry indices were not significantly different in the runners who had previously sustained stress fractures. The involved limb of the previously injured runners demonstrated higher values for braking and vertical impact ground reaction force and peak shock. Interestingly, these runners appeared to have bilaterally-elevated lateral ground reaction forces and loading rates as compared to the never-injured group, although this was not statistically tested. This suggests that previously injured runners may be closer to the injury threshold and, thus, more susceptible. Asymmetry may simply influence the side on which they become injured.

Introduction of T. L. Youd

Dr. Les Youd, Professor Emeritus of Civil Engineering at Brigham Young University, presented the Fifth Seed Lecture at a special session and banquet sponsored by the San Francisco Section of the Geo-Institute of ASCE in 2003. It is especially appropriate that Professor Youd was selected to present the Seed lecture, as he was a leading pioneer in the investigation and use of field performance case histories in geotechnical earthquake engineering, and his expertise and uncanny ability to distill and recall vital data and observations were highly admired by the late Professor Seed. Professor Youd received his BS degree in Civil Engineering from Brigham Young University, and his PhD from Iowa State University. From 1967 to 1984 he served as a Research Civil Engineer with the U.S. Geological Survey. In 1984 he joined the faculty of the Department of Civil Engineering at Brigham Young University, where he served as Chairman from 1994 through 2000. He retired formally in June of 2003, but continues to be actively involved as a Professor Emeritus. Professor Youd was an early leader in geotechnical postearthquake investigations, and has served as a member of postearthquake investigation teams following 11 major earthquakes on four continents. He established high standards for postearthquake studies, and these have been widely emulated, to the considerable benefit of the profession. He also set important standards for study of earlier, “historic” occurrences of seismically induced soil liquefaction. Professor Youd was a pioneer in the development of techniques for mapping of seismic soil liquefaction hazard, and he continues to be an important figure in this field. He has also developed widely used methods for prediction of liquefactioninduced lateral ground movements and corollary damages to

Repeatability of lower extremity kinetics and kinematics for standardized and self-selected running speeds

The purpose of this study was to determine the effects of self-selected versus standardized running speeds on within-day and between-day repeatability of lower extremity kinematics and kinetics for running gait. Subjects (six female, six male, age 18-35) were recreational athletes with no lower extremity injuries. The following study variables were analyzed using the coefficient of variation (CV): the peak angles for knee internal rotation, external rotation, varus, valgus, flexion, and extension; peak angles for ankle dorsiflexion and plantar flexion; peak impact force and propulsive force; and peak anterior, posterior, medial, and lateral ground reaction forces (GRFs). Data for the entire stance phase were analyzed using the coefficient of multiple correlation (CMC) for the following variables: anterior-posterior, medial-lateral, and vertical GRF; the angles and angular velocities for knee internal-external rotation, valgus-varus, flexion-extension, and ankle dorsiflexion-plantar flexion. Each variable was analyzed using a 2 x 2 (speed x day) repeated measures ANOVA (alpha = 0.05). The within-day repeatability for all of the significantly different variables was greater than the between-day repeatability. For variables with a significant difference based on speed, the standardized running speed had greater repeatability. Within-day repeatability is generally greater than between-day repeatability. Running speed had little effect on the repeatability of any study variable. Having subjects run at a standardized speed may not be as important as previously thought.

International standard (ISO) on seismic actions for designing geotechnical works–An overview

The seismic performance of geotechnical works is significantly affected by ground displacement. In particular, soil–structure interaction and effects of liquefaction play major roles and pose difficult problems for engineers. An International Standard, ISO23469, is being developed for addressing these issues in a systematic manner within a consistent framework. The objective of this paper is to give an overview of this International Standard. In this International Standard, the seismic actions are determined through two stages. The first stage determines basic seismic action variables, including the earthquake ground motion at the site, the potential for earthquake-associated phenomena such as liquefaction and induced lateral ground displacement. These basic variables are used, in the second stage, for specifying the seismic actions for designing geotechnical works. In the second stage, the soil–structure interaction plays a major role. Types of analyses are classified based on a combination of static/dynamic analyses and the procedure for soil–structure interaction classified as follows: – simplified: soil–structure interaction of a global system is modeled as an action on a substructure; – detailed: soil–structure interaction of a global system is modeled as a coupled system.

Kinetic Asymmetry In Female Runners With And Without Retrospective Tibial Stress Fractures

The tendency for a runner to become injured on a particular side is not well understood. It has been suggested that it may be due, in part, to asymmetry in their mechanics. PURPOSE The purposes of this study were (1) to compare the levels of kinetic asymmetry in runners who have previously sustained a tibial stress fracture (TSF) and those who have not (CON) and (2) to compare loading parameters between the involved and uninvolved sides of the TSF runners. It was hypothesized that the TSF group would be more asymmetric than the CON group and that they would exhibit greater loading on the involved side. METHODS Twenty-five CON and 24 TSF subjects were eligible for this study. CON subjects reported to have never sustained a running injury. TSF subjects were included if they had sustained one or more tibial stress fractures on a single side of their body. Subjects were asked to run along a 25 meter runway at a speed of 3.65 m/s (± 5%), striking a force platform (Bertec Corp., Worthington, OH) at its center. Data were sampled at 960 Hz. The speed was monitored with photoelectric cells placed 2.86 m apart. Five trials were collected for both the left and right sides. Any trials indicative of targeting were discarded. The same type of neutral running shoe was worn by each subject during data collection. Peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and instantaneous vertical loading rates, and peak shock were measured in each subject. Symmetry Index (SI) was used to quantify asymmetry: SI = (XL – XR)/0.5*(XL+ XR). A 1-tailed, independent t-test was used to compare SI values between the TSF and CON groups. A 1-tailed, dependent t-test was used to compare loading values between the involved and uninvolved sides of the TSF group. RESULTS SI values were not significantly different between the CON and TSF groups for any of the parameters. The peak vertical impact ground reaction force and peak shock were both significantly higher on the involved side in the TSF subjects (p = 0.04 and 0.02 respectively). CONCLUSIONS These results indicate that while CON and TSF subjects have similar levels of asymmetry, those in the TSF group may have elevated loading values, bilaterally, that predispose them to injury.

Bilateral Lower Leg Pain - Softball

HISTORY An 18-year old freshmen softball player presenting with bilateral peroneal pain during running and lateral motions. Pain developed during mid-fall while conditioning for the spring softball season. She reported bilateral burning sensation on the lower leg. She was initially treated with typical modalities and modification of training practices, with no alleviation of the symptoms. PHYSICAL EXAMINATION Examination by the athletic trainer revealed no difference in lower leg appearance, no edema or discoloration. All pain and point tenderness were along the lateral shin. Muscle tightness was noticeable on the soleus and peroneals. Abnormal running mechanics were suspected as a result of the bilateral nature of the pain and inability to alleviate symptoms with normal treatment and training modifications. The athlete was referred to a biomechanist for treatment recommendations. DIFFERENTIAL DIAGNOSIS Shin Splints Compartment Syndrome TEST AND RESULTS The player underwent a biomechanical evaluation to assess running mechanics and make recommendations for functional orthotics. The test revealed a 15% Body Weight (BW) difference between the braking and propulsive forces during running. The right side lateral ground reaction forces were 5% BW higher than the left. The center of pressure path was asymmetrical between right and left sides. The right side showed a shorter path and the left showed a noticeable medial to lateral deviation. FINAL WORKING DIAGNOSIS Compartment Syndrome (resulting from poor biomechanics) TREATMENT AND OUTCOMES The athlete was instructed to ice and cross-train reducing the amount of running until reduction of symptoms. Functional orthotics were designed to address some of the mechanical deficiencies shown in the biomechanics evaluation. A follow-up biomechanical evaluation was performed to address recurring pain on the left during indoor training. At this time the use of the functional orthotics was limited to her running shoes. Due to the identification of developing loading asymmetries two other follow-up biomechanical evaluations were recommended. The first follow-up evaluation was performed prior to her summer break. She was free of lower extremity pain, and her mechanics were improved showing symmetry of loading patterns. She was instructed to continue using the orthotics in her running shoes throughout the summer. The second follow-up evaluation was performed prior to fall training. Her mechanics were symmetrical and consistent with her last evaluation. Treatment of symptoms combined with modification of biomechanics resulted in a pain free return to training and competition during her second season.

Bilateral Lower Leg Pain - Softball

HISTORY An 18-year old freshmen softball player presenting with bilateral peroneal pain during running and lateral motions. Pain developed during mid-fall while conditioning for the spring softball season. She reported bilateral burning sensation on the lower leg. She was initially treated with typical modalities and modification of training practices, with no alleviation of the symptoms. PHYSICAL EXAMINATION Examination by the athletic trainer revealed no difference in lower leg appearance, no edema or discoloration. All pain and point tenderness were along the lateral shin. Muscle tightness was noticeable on the soleus and peroneals. Abnormal running mechanics were suspected as a result of the bilateral nature of the pain and inability to alleviate symptoms with normal treatment and training modifications. The athlete was referred to a biomechanist for treatment recommendations. DIFFERENTIAL DIAGNOSIS Shin Splints Compartment Syndrome TEST AND RESULTS The player underwent a biomechanical evaluation to assess running mechanics and make recommendations for functional orthotics. The test revealed a 15% Body Weight (BW) difference between the braking and propulsive forces during running. The right side lateral ground reaction forces were 5% BW higher than the left. The center of pressure path was asymmetrical between right and left sides. The right side showed a shorter path and the left showed a noticeable medial to lateral deviation. FINAL WORKING DIAGNOSIS Compartment Syndrome (resulting from poor biomechanics) TREATMENT AND OUTCOMES The athlete was instructed to ice and cross-train reducing the amount of running until reduction of symptoms. Functional orthotics were designed to address some of the mechanical deficiencies shown in the biomechanics evaluation. A follow-up biomechanical evaluation was performed to address recurring pain on the left during indoor training. At this time the use of the functional orthotics was limited to her running shoes. Due to the identification of developing loading asymmetries two other follow-up biomechanical evaluations were recommended. The first follow-up evaluation was performed prior to her summer break. She was free of lower extremity pain, and her mechanics were improved showing symmetry of loading patterns. She was instructed to continue using the orthotics in her running shoes throughout the summer. The second follow-up evaluation was performed prior to fall training. Her mechanics were symmetrical and consistent with her last evaluation. Treatment of symptoms combined with modification of biomechanics resulted in a pain free return to training and competition during her second season.

Factors affecting stepladder stability during a lateral weight transfer: A study in healthy young adults

A fall from a stepladder is often initiated by a loss of lateral stability. An inverted pendulum model of the human, validated by experiment, was used to determine the feasible range of whole-body center of mass (COM) states for which weight can be transferred laterally on a ladder tread without a ladder rail losing contact with the ground (“no lift-off” stability region). The results show that the size of the feasible no lift-off region was inversely proportional to the height of the tread above the ground, the distance of the stance foot from the ipsilateral rail, and lateral ground inclination angle. For given initial COM kinematics on a tread height equal to 40% human body height, a stance-foot location equal to one-eighth tread width and a 3.5° ground inclination had approximately equivalent effects on the no lift-off region size. Ladder stability was three times more sensitive to tread height than to foot location. Laterally-exerted impulsive hand-tool forces should generally be limited to 8% body weight. These findings can lead to improved ladder designs and safety instructions for stepladder users.

The role of 3-D geomagnetic induction in the determination of the ionospheric currents from the ground geomagnetic data

Abstract. The geomagnetic field variations measured at the surface of the Earth are composed of both internal and external parts. The external field arises from the sources in the magnetosphere and ionosphere, whereas the internal field is generated by the currents induced within the Earth. The internal part may in some situations comprise a notable part of the measured total field and thus a blind usage of geomagnetic field recordings potentially produces significant errors to estimated ionospheric currents. In this paper the role of geomagnetic induction in auroral ionospheric studies is investigated by modeling the induction using simultaneously the realistic ionospheric source and a realistic three-dimensional Earth conductivity structure. The modeling results imply that the effects of the lateral ground conductivity anomalies on ionospheric equivalent current patterns are, though clearly detected, less severe than anticipated for fields varying with periods from 5 to 120min. However, the amplification of the determined currents caused by induction is significant, leading to an overestimation of up to 30% of the main current flow intensities, with the overestimation increasing sharply when moving away from the region of the main flow. In addition to the 3-D modeling, a simple method is introduced to help estimate the internal contribution to the measured variations of the IL index (local variant of the AL index). A test with the 26 June 1998 substorm event indicates that the method can help to extract the internal contribution from the IL index.

Lateral Pipe–Soil Interaction in Sand with Reference to Scale Effect

This paper investigates the pipe.soil interaction for pipes buried in cohesionless soil when subjected to lateral ground movement. A review and reappraisal of the literature is conducted to identify some inconsistencies and shortcomings of previous studies. The effects of model scale, stress level (via burial depth), burial depth ratio, and soil properties are systematically addressed through finite element analyses. The study concludes that the effects of pipe size and burial depth must be taken into account to properly estimate the maximum pipe.soil interaction forces induced by lateral ground movement. A unique equation considering scale and the effect of burial depth is proposed to determine the maximum pipe-soil interaction forces at various burial depth ratios.

Characterization of V-groove coupled microshield line

A new membrane supported air-filled V-groove coupled microshield has been investigated using finite element method. The even- and odd-mode characteristic impedances and the effective dielectric constants have been computed. The dependence on various dimensions has been studied. The crosstalk levels between adjacent lines have been compared with that in coupled microstrip lines, coupled microstrip lines with lateral ground planes, and V-groove structures with and without metallization in the groove.

Compact asymmetric coplanar waveguide filter

The design and implementation of a novel asymmetric coplanar waveguide (ACPW) band rejection filter using defected ground structure (DGS) is presented. The proposed ACPW DGS technology provides bandgap characteristics with only one cell in the lateral ground plane. The equivalent circuit model of the proposed DGS unit section is described. Measurements of ACPW DGS showed good agreement with simulation and the proposed model.

Geology seismotectonics and soil liquefaction susceptibility of Ilgın (west-central part of Turkey) residential area

In this study, soil liquefaction susceptibility of the Ilgın residential area, that is located in the first-degree earthquake zone in the central part of Turkey, was investigated. Safety factors of soil liquefaction were calculated by using standard penetration test (SPT) blow counts, which are determined in different levels of 45 boreholes, measured groundwater level data and fines content (FC) of soil which is determined through laboratory tests. Soil liquefaction safety factors were calculated by using earthquake magnitude (ML=6) and different earthquake peak lateral ground accelerations (PGA) such as 0.1, 0.2, 0.3 and 0.4 g. In the soil, up to 12 m depth, if liquefaction is likely to occur for 0.1, 0.2, 0.3 or 0.4 g of earthquake lateral peak ground acceleration, soil liquefaction susceptibility is classified as “very high”, “high”, “medium” or “low”, respectively. If liquefaction does not occur in the soil for 0.4 g of PGA, then soil liquefaction susceptibility is classified as “very low” or “non-liquefiable soil”. Based on this classification, soil liquefaction susceptibility maps of Ilgın residential area are prepared for depths of 2, 4, 6, 8, 10 and 12 m. The cumulative liquefaction susceptibility ratio of soil (the number of analyses is determined/the total number of analyses) below the groundwater table is determined to be 63%, 87%, 80%, 80%, 64% and 56% for depths of 2, 4, 6, 8, 10 and 12 m, respectively. Significant liquefaction can be expected in the soils having the same characteristics in the Ilgın residential area and its surroundings in case of an earthquake with magnitude of 6–6.5. Much property may happen in case of an earthquake as a result of this soil liquefaction. Therefore, precautions must be taken in order to prevent losses in Ilgın and its vicinity.

Liquefaction-Induced Lateral Spreading at Izmit Bay During the Kocaeli (Izmit)-Turkey Earthquake

This paper presents a study of liquefaction-induced lateral ground displacements along the coast of Izmit Bay during the 1999 Kocaeli (Izmit)-Turkey earthquake. The paper discusses: (1) observed ground displacements after the earthquake, (2) the results of field investigations by means of borings and in situ index tests, including standard penetration tests, static cone penetration tests, and piezocone tests, (3) analyses of expected lateral displacements using two empirical models and one semiempirical model, and (4) comparisons between observed and calculated lateral ground movements. The three models provide inconsistent predictions of observed lateral ground displacements, with one method overpredicting and two methods both overpredicting and underpredicting observed lateral ground displacements by large amounts. Thus, it appears that there is a need for improved engineering tools for prediction of small to moderately significant lateral ground displacements (lateral displacements of approximately 0.1–2.5 m) at soil sites with similar ground characteristics to the case history sites presented herein.

Damage due to the Mw 7.7 Kutch, India earthquake of 2001

This paper presents a study of the damage due to the M w 7.6–7.7 intraplate Kutch earthquake of 26 January 2001. It was a powerful earthquake with a high stress drop of about 20 MPa. Aftershocks (up to M 4) have continued for 2.5 years. The distribution of early aftershocks indicates a rupture plane of 20–25 km radius at depths of 10–45 km along an E–W-trending and south-dipping hidden fault situated approximately 25 km north of the Kutch Mainland Fault. The moment tensor solution determined from regional broadband data indicates reverse motion along a south-dipping (by 47°) fault. The earthquake is the largest event in India in the last 50 years and the most destructive in the recorded history in terms of socioeconomic losses with 13,819 deaths (including 14 in Pakistan), collapse/severe damage of over a million houses and US$10 billion economic loss. Surface faulting was not observed. However, intense land deformations have been observed in a 40×20-km meizoseismal area. These include lateral spreading, ground uplifts (about a meter), ground slumping and deep cracks. Liquefaction with ejection of sand and copious water was widespread in the Banni grassland, Rann areas (salt plains), along rivers and also in the coastal areas up to 200 km distance from the epicenter in areas of intensity VII to X+. Stray incidences of liquefaction have occurred up to distances of at least 300 km. For the first time in India, multistory buildings have been destroyed/damaged by an earthquake. The maximum acceleration is inferred to be 700 cm/s 2 and intensities are 1–3 units higher in soil-covered areas than expected from the decay rate of acceleration for hard rock.

側方流動地盤における群杭基礎の地盤反力発生メカニズム

Two series of shaking table tests, i.e., one had a quay wall and the other had not, are conducted to clarify a lateral ground force acting on piles in liquefied and laterally spreading soils. It is shown that (1) The lateral ground force acting on a pile in laterally spreading soil as well as that in liquefied soil has character of solid ground due to decrease of excess power water pressure and recovery of effective normal stress after liquefaction; (2) The lateral ground force acting on a pile near quay wall becomes nine times larger than the maximum inertial force at a pile head in laterally spreading soil.

２次元弾性解と個別要素解析によるトンネル支保特性曲線の考察

Active mobilization of bearing capacity of rock mass surrounding an underground opening characterizes the NATM (New Austrian Tunneling Method) concept of supporting. There have been many attempts to give quantitative expressions for this capacity but no one has ever completely solved the question. In the first part of this paper the theoretical relations between support pressure and tunnel wall displacements are briefly discussed. We derive a simplified solution of a circular lined-tunnel in an elastic ground under the plain strain for full-slip and no-slip conditions. These two conditions at the ground-lining interface make it possible to explain the effects of shear stress transmission and relative shear displacement. The lateral free-field ground stresses for this solution are restricted to a fixed value of the vertical stresses (σV*=-p, σH*=-kp). An actual tunnel opening is excavated and supported after the load corresponding to the free-field stresses. We introduce an assumption of the actual “excavation unloading” conditions that occur during tunneling. By advancing this derivation, the strict solution is utilized successfully to construct a theoretical characteristic curve of tunneling. The characteristic curve shows clearly the bearing capacities of a tunnel lining, the surrounding ground and the total by using an index, “relative-support-stiffness”.The elastic theory of the stress distribution around tunnels demonstrates that the deviatoric stresses are maximum at the periphery of the excavation. Therefore, the rock mass may yield in the overstressed zone surrounding the excavation. Discussion here should include the dependence of the characteristic curve on the zone of yielded ground and the discontinuity in the ground. We have carried out numerical simulations for a discontinuous ground with Distinct Element Modeling. The realistic ground reaction curves by the analyses are examined with the theoretical solution derived above. We will learn that while the ground may work, more or less, as a load bearing structural component to the load corresponding to the free-field stresses, overestimation must be avoided.