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This article discusses the effects of leaching on soluble soil particles. Topics include permeameter testing, foundation engineering, and soil liquefaction.

The criteria directing silty sand shear strength are discussed and rated. These include whether the fines are plastic or nonplastic, and how sandy soils are categorized, which helps calculate load deformation resistance and friction rates.

A discussion is presented comparing the advantages and disadvantages of using piles or piers to stabilize soil slopes. Topics include minimization of moment and shear forces and vibrations caused by driving piles, as opposed to drilling piers.

An exploration is presented on the impact of mine subsidences on surrounding structures. Settlement cracks were observed near structure corners, rather than their centers; recommendations for releveling include the installation of thin reinforcing plates, hydraulic jacks, and strap retrofitting applied to foundation walls.

Different types of failures are examined for excavated slopes in clay soils. These include surficial failures, degree of slope-face weathering prior to excavation, desiccation cracking and slaking due to drying and wetting, and seepage parallel to the slope.

A study on the development of a modified Newmark model for determining the permanent displacement of slopes in earthquakes is evaluated. It is argued that other cases exist where earthquake deformation is underpredicted. Two examples are presented. The first involves the reduction of shear strength during the California Northridge earthquake on Jan 17, 1994. Another involves slope movement caused by loose cohesionless soil deformation.

Authors M.C. McBrayer, M. Mauldon, E.C. Drumm and G.V. Wilson conclude their study on the hydraulic conductivity of compacted clay subjected to cycles of of wetting-drying or freezing-thawing with the observation that cracks due to these cycles do not fully heal upon hydration. Several other studies, however, have shown that cracks due to wetting-drying or freezing-thawing cycles actually do heal completely upon wetting. The type of clay mineral is believed to be a significant factor in the healing of cracks upon wetting.

The purpose of this paper is to describe the settlement behavior of posttensioned slab-on-grade. The two case studies illustrate that the amount of damage to the structure depends on how the posttensioned slab-on-grade deforms. For the first case study, about one-half of the posttensioned slab-on-grade was unaffected by soil movement and remained relatively level, whereas the remaining one-half of the slab settled. This caused the development of a slab crack and hinge point, where moderate damage occurred in the area parallel to the slab crack. The Skempton and MacDonald settlement criteria and the severity of damage versus foundation deformation parameters were applicable for this case. For the second case study, which was the settlement of deep fill, there was a tendency for the posttensioned slab-on-grade to tilt uniformly (no hinge point). This resulted in substantially less damage than the first case study, even though the maximum differential settlement was greater for the second case. The severity of damage versus foundation deformation parameters were not applicable for this case. One advantage of posttensioned slab-on-grade that was common for both cases was that the slab cracks were relatively small, due to the posttensioning (compression) effect, which enabled the slab to resist the tension forces due to fill settlement.

A seven-step procedure to be used in determining the severity of ground-movement-related building damage based on approximate crack width may be inaccurate when cracking is hidden or patched or when other factors contribute to the crack widths. The severity of the damage should be based on a number of factors, which include crack widths, differential settlement, and angular distortion of the foundation.

A study was conducted on the confining pressure-caused crushing of granular particles. Results show that particle crushing is reduced by enhancing mineral hardness and that smaller amounts of breakage for a given stress is achieved with stronger or harder particles. Results are consistent with those obtained from the crushing of sedimentary rock-derived oversized particles.

Laterally-loaded drilled shafts in clay have been modeled. Construction data reveal that shafts are usually short and stubby and frequently behave as rigid parts when experiencing lateral loads. However, lateral load tests are not performed in a majority of scenarios for the design of laterally loaded shafts, mainly due to cost constraints posed by field tests.

A case study of Northridge Earthquake induced movement of landslide debris is presented. Based on the width of the observed cracks, the estimated earthquake-induced lateral movement of the landslide debris was 6-12 mm (0.25-0.5 in.). Associated with the lateral movement of the landslide debris, there was a differential movement of 102 mm (4.0 in.) of the house foundation and 69 mm (2.7 in.) for the pool. There was severe damage to the house and the appurtenant structures due to the landslide debris movement. Inclinometer readings indicate that the landslide debris continued to move after the earthquake. Because the house was built in 1956, there probably was no geologic investigation which would have detected the unstable geologic condition at the site.

This paper describes the failure of the Desert View Drive fill embankment in La Jolla, Calif. The embankment was built in late 1960 or early 1961. Other than a report of surficial instability in 1977, the embankment was marginally stable (factor of safety of 1.15) until 1990, when an excavation group cut into the embankment to construct a building pad and house. The resulting failure of the Desert View Drive fill embankment was a progressive failure, starting as a circular mode and eventually increasing to a wedge type movement of the entire fill embankment. The legal theories used as the basis to sue the city of San Diego were that (1) the city officials were aware of the defective condition (poor compaction) of the embankment, but they did not fix this condition; and (2) they failed to provide subjacent support to the homeowners property. The repair of the fill embankment consisted of the construction of 40 massive piers anchored in the underlying Ardath shale.

A case history of pavement deterioration is described. There were three pavement concerns: an inadequate pavement section, seepage of water through the base material, and settlement of utility backfill. The main pavement deficiency was the aggregate base, which in some locations was much less than the original pavement recommendations. Water migrated into the base causing the compacted clay subgrade to become wet with a corresponding reduction in shear strength. Because of the thin aggregate base, the pavement section could not sustain the traffic loads, resulting in alligator cracks, rutting and, in some cases, complete disintegration of the pavement. It was also observed that water was flowing through the aggregate base. For inclined pavements with a permeable aggregate base constructed on top of a clay subgrade, theoretical analysis indicates that the majority of water will flow through the base material instead of into the subgrade.

In order to resist sulfate in soil or ground water, concrete must be of high quality, be well consolidated, be as impermeable as possible, and have sulfate-resistant cement. This paper describes the damage to concrete flatwork caused by sulfate attack. Four of six laboratory tests indicated that the silty clay fill supporting the concrete flatwork had a 'severe' concentration of soluble sulfate. Expansion of the silty clay fill probably uplifted and cracked the concrete flatwork. Then moisture migrated up through the flatwork cracks and upon evaporation, the salts were deposited on the concrete crack faces. This increased the soluble sulfate concentration causing the concrete paste to literally dissolve away. One method to prevent the concentration of sulfate at flatwork cracks is to provide a capillary break, such as a layer of 2 cm (3/4 in.) open-graded gravel, beneath the concrete flatwork.

The authors presented a well-researched and thought-provoking paper about the risk of housing damage caused by expansive soils. Their observation that the problem has not been addressed by the civil engineering establishment is largely due to the fact that there have been few victims of expansive soil. Moreover, the slow process of foundation heave ensures that any damage manifests itself years after a house is constructed.

A case study of the settlement of gravelly sand backfill is presented. Flatwork, which had been constructed on top of the backfill, was damaged due to the settlement. It is likely that the cause of the settlement was improper compaction methods and/or too low of a compaction standard. Laboratory tests were performed to investigate the settlement behavior of the gravelly sand. If the gravelly sand had 0-20% oversize particles, there were not enough oversize particles to interfere with compaction and the settlement behavior depends on the matrix dry density. For 20-40% oversize particles, they begin to interfere with compaction, but the settlement behavior still depends on the matrix dry density. For 40-70% oversize particles, they continue to interfere with compaction, and the settlement behavior is very complex and depends on the proportion of vertical stress carried by the oversize particles. For 70-100% oversize particles, the compaction energy is absorbed by the oversize particles and the settlement behavior depends on the compression behavior of the oversize particles.

This paper describes the reactivation of an ancient landslide during the construction of a fill buttress. Even though precautions were taken during construction of the buttress, such as excavating it in 30-m-long (100-ft-long) segments, the ancient landslide nevertheless was reactivated. The reactivated landslide moved laterally about 5-8 cm (2-3 in.), which resulted in significant damage, such as cracking to building foundations, walls, and ceilings, as well as distortion of door frames and windows. An interesting observation was that the ancient landslide, once activated, did not stop immediately after the buttress had been backfilled. The lateral movement continued for about 10 months, at a decreasing rate of movement. This movement was probably due to the slow closure of the ground cracks as well as the deformation of the landslide into the buttress. This case history illustrates the disadvantage of using a buttress to stabilize an ancient landslide, especially when the excavation is below the rupture surface.

This paper discusses the preparation of written documents with the goal of reducing potential liability. Guidelines for the preparation of reports are summarized in Appendix I and phrases or clauses, which should be added to reports to reduce potential liability, are presented in Appendix II. Reports and field memos should be well-thought-out documents that reflect field conditions accurately. Hastily written reports or self-incriminating field memos, such as those in which the engineer admits to not following the plans or specifications, can increase potential liability. If an engineer is involved in a lawsuit, the information contained in the file will be available to all parties. The file should contain correspondence, testing, photographs, analysis, reports, and maps. Items that should be discarded include old drafts of reports or letters, personal documents, rough notes or calculations, and inappropriate or unrelated material.

The paper describes a case history of severe damage to a house due to the settlement of fill containing organic matter. As the organic matter in the fill decomposed, the house settled, causing 10 cm. (4 in.) of foundation differential movement. The fill settled so much that open voids developed beneath the footings and the rear yard flatwork. One-dimensional compression tests were performed on soil samples with different percentages of organic matter, where the organic matter was allowed to decompose, and the corresponding settlement was measured. The laboratory tests indicate an empirical relationship in which percent organics equals percent settlement, for a condition of complete decomposition. The amount of settlement was similar for organic matter distributed throughout the sample or placed as one layer at the center. The detrimental effects of organics in fill include a reduction in soil density, increased compressibility during loading, and time dependent settlement as the nonhumic substances decompose and compress.

It is important for civil engineers to use language with care because some word have a specific meaning in the law. Examples include 'guarantee,' 'warrant,' 'certify,' and 'ensure.' These words should be avoided in reports because they can have legal definitions that increase the liability of the civil engineer. Other words such as 'control,' 'inspect,' and 'supervise' can be legally interpreted to mean a level of project involvement well beyond the intent of th author. Superlatives, such as 'maximum,' 'minimum,' and 'always,' are frequentl used by civil engineers in reports, but these words imply an absolute or ultimate condition, with no margin for error. Some technical words can give false impressions, and they should also be avoided or clearly defined.

The main advantages of gunite brow ditches are cost, ease of construction, durability, and simple flow-capacity equations. The main disadvantages are weakness due to shrinkage cracks; rigidity, which makes them vulnerable to soil movement; susceptibility to chemical attack; aesthetics; and maintenance, which is required to keep them clear of obstruction that can clog pathways. The standard specifications require a setback from the top-of-slope of 0.3 m (12 in.). This setback should be adequate for slopes in rock and for compacted sand and gravels. But slopes composed of compacted clay will creep if the slope face is wet to saturated. The three parameters that determine the primary zone of creep for this condition are shear strength, slope height, and slope inclination. An empirical equation [(1)] can be used to estimate the gunite bro ditch top-of-slope setback distance for compacted-clay slopes.

A debris flow is defined as soil with entrained water and air that moves readily as a fluid on low slopes. A case history of a debris flow adjacent to the Pauma Indian Reservation is described. Two contributing factors in the debris flow were the cutting down of trees and the construction of haul roads. The debris flow travelled a long way (370 m) in the depositional area before striking a house. Fortunately, by the time the debris flow reached the house, the energy was nearly spent and there was no damage to the structural frame. The material involved in the debris flow was classified as silty sand. Results of laboratory tests indicate that this type of soil is susceptible to debris flow. There is a range of coefficient of permeability from about [10.sup.-2] to [10.sup.-6] cm/s that corresponds to soils that have an optimum soil permeability for long-distance flow in the depositional area. Based on the historical method, it is probable that there will be future debris flow in this area.

In the United States, a practicing engineer cannot perform services without the fear of a lawsuit. Some strategies for avoiding civil liability include assessing the risk before accepting the assignment, purchasing errors-and-omissions insurance, and using limitation-of-liability clauses in contracts. Each strategy has advantages and disadvantages. For example, by purchasing insurance, the insurance company will have to pay the attorneys fees, provide the legal defense, and pay judgments up to the limits of the policy. But insurance can be very expensive, and some engineers believe that having insurance invites lawsuits. Another common strategy is to use a higher factor of safety in the design, which may cost the client more but will reduce the risk of failure. The trend in the United States is toward a more litigious society, one where failure will not be accepted without a lawsuit.

A slab-on-grade must be designed to resist two types of expansive soil movement: the short-term cyclic heave/shrinkage around the perimeter of the foundation and the long-term progressive swelling beneath the center of the slab. The purpose of the conventional slab-on-grade on expansive soils is to provide deepened perimeter footings that are below the active zone of seasonal swell/shrinkage and to soak the soil subgrade in order to reduce the long-term progressive swelling beneath the center of the slab. Two common problems with this foundation are that the perimeter footings are not deep enough to resist the short-term cyclic heave/shrinkage and the presoaking beneath the slab is not done properly. The purpose of the design of the posttensionred slab-on-grade is to build a foundation that is strong and rigid enough to resist the expansive soil forces using the centerlift and edge-lift deformation configurations. Three potential problems are that the expansive soil movement is cyclic, the edge moisture variation distance is based solely on climate, and the center-lift deformation may be underestimated.

There have been different standards of care throughout history. Hammurabi's legal standard was that if a house collapsed and killed the owner, then the builder would be killed. The Napoleonic code stated that if a structure had a serviceability problem within 10 years of its completion, the builder would be sent to prison. The contemporary standard of care is commonly defined as that level of skill and competence ordinarily and contemporaneously demonstrated by professionals of the same discipline, practicing in the same locale, and faced with the same or similar facts and circumstances. This standard must take into account the engineer's learning and skill, the location where the engineer practices, the availability of facilities, and whether the civil engineer qualifies as a specialist, in which case the standard of care may be higher. In a court of law an expert witness determines the standard of care based on investigations, a review of reports and records, or opinions of other professionals performing the same or similar services at the time in question.

Water can migrate through basement walls due to hydrostatic pressure, capillary action, and vapor pressure. The purpose of this paper is to describe a case history of moisture migration through basement walls at a condominium project. The results of subsurface exploration revealed that the upper 0.4-0.5 m of the basement wall did not have a waterproofing membrane. This allowed moisture to seep in near the top of the basement walls. An attempt was made by the developer to stop the leakage through the basement walls by applying a waterproofing membrane to the interior wall surface, but this did not stop the moisture infiltration. The problem could have been avoided if the developer had noticed the height of the waterproofing membrane in relation to the final finish ground surface during construction.

In a recent surficial slope failure in a compacted silty sand fill slope it was observed that the failure plane had developed just beneath the bottom of the grass roots. Results of drained direct shear tests performed at low normal stresses indicated that root-permeated fill had a much higher shear strength than the same root-free soil. The results of surficial stability analyses showed that live roots will significantly increase the factor of safety. The live roots provided mechanical reinforcement of the slope and thus the failure surface developed beneath the bottom of the roots. Although a factor of safety of 1.5 is generally the minimum value for new construction, a lower factor of safety may be acceptable in recognition that deep-rooting plants will increase the long-term surficial stability of a slope.

Adobe is an uncemented to weakly cemented material, which makes it susceptible to erosion or disintegration from rainfall, periodic flooding, or the presence of a shallow ground-water table. This paper deals with the Guajome Ranch house, in Vista, Calif., a National Historic Landmark, which was primarily built during the period 1852-54. It was constructed of adobe walls 0.6-1.2 m (2-4 ft) thick. Both the interior and exterior of the Guajome Ranch house have considerably deteriorated due to a lack of maintenance. Drainage of the main courtyard is accomplished by simply letting water flow in ditches beneath the interior floor-boards. This has resulted in severe deterioration where the water has come in contact with the adobe foundation. The results of laboratory tests on original adobe material demonstrated the rapid deterioration of the adobe when it is subjected to wetting-drying cycles. A new surface drainage system is proposed for the Guajome Ranch house in order to prevent surface water from coming in contact with the adobe foundation.