Saprolitic Soils Research Articles

Data-enhanced design charts for efficient reliability-based design of geotechnical systems

This paper proposes a new design chart approach for reliability assessment, which enables clear visualization of the representative soil shear strength parameters under various reliability levels and effective stress levels. Utilizing the design charts, reliability assessment or reliability-based design can be performed with significantly reduced numbers of evaluations of the geotechnical system response. The design charts are established solely based on the probability distributions of soil parameters, and are applicable to a variety of geotechnical problems involving the same soil type. For practical illustration of the proposed approach, design charts are produced from the shear strength databases of saprolitic soils and colluvial soils in Hong Kong, and then applied to the reliability-based design of a slope with soil nail reinforcements. The ensuing design solutions require much fewer soil nails compared to the conventional design practice, while also achieving a better system reliability. The same charts are then applied to the reliability-based design of a retaining wall, where a series of design options are identified with equivalent reliability index against overturning failure and pullout failure. Through the proposed approach, the use of design charts promotes efficient reliability-based design of geotechnical systems with rational incorporation of reliability concepts.

Maximum shear modulus estimative from SPT for some Brazilian tropical soils

Maximum shear modulus (G0) has been used in various geotechnical jobs (e.g., seismic site assessment, machine vibration and pile driven). Laboratory and in situ determination of G0 is not a current practice in Brazil. G0 can be estimated from empirical correlations based on in situ tests like Standard Penetration Test (SPT) and Cone Penetration Test (CPT) in the preliminary design phase. Several empirical correlations to estimate G0 from SPT N value have been developed and are available in the literature. However, most of these correlations were established based on experience with well-behaved soils formed in temperate and glacial zones, which may not always be used for tropical soils. This paper assessed and discussed the applicability of some correlations for G0 estimative from SPT data in lateritic and saprolitic soils. The classical correlations for sedimentary soils underestimated G0 of tropical soils. After updating the database, the tropical soils correlations reasonably estimated G0 for the lateritic ones, which was not the case for the saprolitic soils. It was observed that differentiating the soils only as lateritic or saprolitic was not adequate for a good G0 estimate for the saprolitic sandy soils. It was found that only the lateritic soils correlation can be used with caution as a preliminary attempt to estimate G0 from SPT N value in soils with similar characteristics to the ones presented in this paper.

Preferential flow patterns in forested hillslopes of east Tibetan Plateau revealed by dye tracing and soil moisture network

AbstractPreferential flow (PF) through soil and regolith results in a rapid vertical and lateral water movement within the profile. This study focused on quantifying PF in contrasting forested hillslopes of the Hailuo Valley, located on China's east Tibetan Plateau. Quantifying PF in this region is challenging since the underlying matrix is complex, with shallow soils, thick underlying saprolite, and the combined effect of moraines and weathered residual material. We developed new methods that integrated dye tracing with a high‐frequency soil moisture monitoring network to characterise PF pathways and quantity PF frequency on contrasting forested hillslopes (coniferous and broadleaved). Dye tracing experiments showed that soil‐root interfaces in the upper soil layer (10–50 cm) and soil‐rock interfaces in the deeper soil layer (50–100 cm) were the primary PF pathways and that large rocks strongly influence the percolation depth of water. The high‐frequency soil moisture network revealed that the mean PF frequency was 67.8% and 71.7% in the coniferous and broadleaved forests, respectively. The frequency of PF in the deeper soil layer increased from upslope to the downslope locations on both forested hillslopes, highlighting the tendency for PF to occur downslope. In addition to matrix conditions (e.g., stony saprolite soil), the total amount and maximum intensity of precipitation (as throughfall in this study) were identified as factors that control PF occurrence. In contrast, the initial soil water conditions (at 10, 50 and 100 cm depth) were insignificant in predicting PF occurrence. Results of this field‐based study highlight that PF is a ubiquitous and critical subsurface flow mechanism that regulates rainfall‐runoff relationships in forests of the Tibetan Plateau, underscoring the need to consider PF in hillslope hydrological modelling.Highlights Combined dye tracing and soil moisture monitoring network were applied to explore PF on forested hillslopes. Root networks and rock fragments constituted the main PF paths. PF frequency increased from upslope to downslope in two forest types. Initial soil moisture conditions showed no controlling effect on PF occurrence.

Difference in Soil Biogeochemical Properties of Agricultural Highland by Topographical Characteristic and Soil Management

In agricultural highland, soil properties change over time due to soil management methods, soil erosion, and cultivation. The objective of this study was to investigate the differences in soil properties according to land management in agricultural highland. As a result of the soil analysis, Anbandegi, Maebongsan, Yeongwol, and Jeongseon, located near the top of the mountain, had low bulk densities, and organic matter, CEC, exchangeable cation, water stable aggregation rate, and dehydrogenase activity, were relatively higher than those of Daegwallyeong and Punch bowl. In the Daegwallyeong and Punch bowl, saprolite soil was periodically piled to replace eroded top-soil, and as a result, soil characteristics differed significantly from those located near the top of the mountain. In the principal component analysis result, organic matter showed the largest eigenvalue in PC1, and pH was selected as PC2. The distribution of soil clusters by sampling point was PC1, and Daegwallyeong and Punch bowl were classified differently from highland areas near the top of the mountain, and coastal basins and Daegwallyeong were classified by PC2. In conclusion, highland soil showed different soil properties for each region, which was the result of differences according to the soil management methods. And considering the relationship between soil characteristics, it was confirmed that organic matter was the most important factor in the soil management methods. Coefficients of each variable for PC1 and PC2 through the PCA of agricultural highland soils.

Soil physical properties and slope stability in Serra do Mar, southeastern Brazil

Soil physical properties play an important role in landslide rupture mechanisms, since changes in soil texture, structure, and porosity can affect slope permeability. This study characterized a granitic weathering profile and assessed the changes in the properties of the materials related to the main mechanisms that trigger landslides. The study identified three layers with distinctive particularities in macromorphological and micromorphological terms: mature residual soil (well-developed), young residual soil (saprolitic soil), and saprolite. Morphological characterization was carried out in addition to textural analysis, and soil porosity and saturated hydraulic conductivity (Ksat) tests. The weathering profile presented clear differences in morphology, pore size and soil texture, which could indicate distinct weathering grades. The results suggested that continuous heavy rainfall could contribute to the increase in pore-water pressure between mature residual soil and young residual soil, favoring the occurrence of slope failure.

Geotechnical and micro-structural characteristics of phyllite derived soil; implications for slope stability, Lesser Himalaya, Uttarakhand, India

Collapses of hill slopes along critical roadways are of dire consequence. Large literature is available on the stability assessment of hill slopes composed of rock and soils; however, a lacuna exists when it comes to geotechnical appraisal and instability aspects of slopes composed of in-situ saprolitic soils. The present study examines the physical, micro-structural and geotechnical characteristics of soil derived phyllite, and its ensuing influence on the instability of hill slopes at certain sections along National Highway-7, Uttarakhand, India. Four distinct locations along the highway were selected for the study. After field survey, the laboratory investigation was carried out to ascertain the geotechnical, chemical and mirco-structural parameters of the representative phyllitic soil samples. Eventually, stability analysis was carried out using Limit Equilibrium Method, Finite Element Method, and Finite Difference method, for the four locations. The analysis for location 2 & 4 showed them to be in a critical - unstable state, whereas, location 1 & 3 demonstrated stability in the present state. Compared to other techniques, FDM analysis results were in close congruence with the ground truth. The present study also sheds significant insight into the composition and deformation behaviour of the soils derived from the weathering of phyllite. The research may have enormous ramifications for the future assessment of similar soils and their possible use as admixtures in construction industry.

Experimental investigation of both the disturbed and undisturbed granitic saprolite soil

Granitic saprolites are abundant in many regions around the world and they are widely employed in various engineering projects. Behavior of such kinds of soils is not sufficiently understood and our knowledge about the fundamental behavior of saprolites is to a far less extent than the sedimentary soils. Owing to the limited knowledge, many problems occurred in the engineering applications that used saprolites as a construction material. This study presents results of a set of conventional drained and undrained triaxial compression shearing tests on the granitic saprolites in both the disturbed and undisturbed conditions. This study showed that the soil fabric was the paramount factor governing on the soil stress–strain response rather than the soil bonds. Under the drained shearing condition, the undisturbed soil revealed a strain-softening behavior with a dilative response at the low consolidation stress level, while a contractive response was present at the high consolidation stress levels. However, the disturbed soil showed a strain-hardening behavior with a contractive response, regardless of the consolidation stress levels during the drained shearing. The undrained response was complicated, as the soil showed both the contractive and dilative responses with phase transformation points, regardless of the soil condition (i.e., disturbed or undisturbed) and the consolidation stress levels. The bond effect of the intact soil persisted during the consolidation stage; however, its effect did not extend to the large strain-controlled shearing stage, where the tangential stiffness suddenly decreased at the axial strain of 1.5%.

Analysis of compressibility and mechanical behavior of red clay considering structural strength

Red clay is the main geometrical as the foundation of buildings, dam, and excavation which are usually designed and constructed without concern of its structure with depth, leading to a design which is not reasonable and a massive waste of resources. The research reports investigations carried out on red clay to study its compressibility, strength and stress path, and their variation with depth. The effect of structure with depth on red clay has been discussed and the mechanics were investigated by undrained consolidated triaxial tests, X-ray diffraction, and one-dimensional compression tests. This research determined a gradual destructuration process by a new normalized method. The change of structure with depth has been analyzed which is different from saprolitic soil caused by its special weathering process. Higher strength parameters were consistent with regular clay content. The compressibility and strength were shown to strongly depend on the depth, and hardening phenomenon has been observed for all specimens at the laboratory scale. In addition, triaxial tests with a varying number of consolidations were conducted to assess the influence of the consolidation. The results revealed a marked type of ultimate steady state (USS). The strength increases by 12.7%, 33.8%, and 2.67% for axial strain (20%) under the confining pressures of 200, 300, and 400 kPa, respectively.

Neolithic geoarchaeology at Penedo dos Mouros Rockshelter: Mid‐Holocene site formation, diagenesis and human activity at the foothills of Serra da Estrela (Portugal)

AbstractThe Neolithic occupation of Penedo dos Mouros in the foothills of Serra da Estrela, Portugal's highest mountain, dates to the 5th to 4th millennia cal B.C. The site's faunal assemblage is extremely rare in the regional prehistoric archaeological record, due to the acidity of the granitic geology. This underlines Penedo dos Mouros importance as a reference site for understanding early pastoralism in the region. Due to the insufficient survival of bone collagen for radiocarbon dating and the homogeneity of the stratigraphy, where most visible contacts are due to post‐depositional processes, we chose micromorphology to address the reasons behind the bone preservation and to assess the stratigraphic integrity of the prehistoric deposit. Reworking of eroding saprolitic soils was a major factor in the sediment accumulation, with remains of short human occupation events. Possible evidence for clearance fires linked to the first occurrences of pastoralism practised in the region, creating open spaces for grazing, was identified. Post‐depositional carbonate cementation derived from ashes, identifiable at the microscopic scale, enabled bone preservation. Carbonate and spodic‐like features document water saturation once the sedimentation ceased. This sedimentary dynamic has broader geomorphological implications, such as an inferred post‐Neolithic incision of the stream valley adjacent to the site.

Influence of Rainfall Patterns on the Slope Stability of the Lumwana (the Malundwe) Open Pit

Malundwe open pit has experienced slope failures in the pit’s upper stack during rain-season since mining started in 2008. Laboratory and numerical model investigation methods were performed to investigate the influence of the rainfall pattern on the stability of the upper stack having saprolite domains. The saprolite soil was classified using the British soil classification system as slightly clayey, silty, sand with fine gravel which are of low plasticity. The water retention test using pressure test conducted on saprolite, reveals that the saprolite soil could not dry up completely as it contains about 9% volumetric content of water with the matric suction of 300 kPa during the most dehydrated month. The rainfall patterns at the mine site increase the groundwater level on the saprolite material. The rising of the groundwater table leads to the reduced matric suction and increased volumetric water content in saprolite domain. The reduced matric suction in the saprolite soils reduce the saprolite soil’s shear strength effectively leading to slope instability. Therefore, rainfall infiltration is the facilitator for initiating the failure of the upper slope at Malundwe open pit.

Determinação dos Parâmetros de Erodibilidade de um Talude de Corte na Sub-Bacia Rio Sana (Macaé, RJ, Brasil)

The issues associated to soil erosion include losses of arable lands and slopes destabilization. Thus, obtaining indexes which reflect the soil erodibility of a region can provide a better occupational planning in poorly degraded areas. In this work, a soil profile exposed at a cut slope face which reflects the regional geology was studied by Sana river sub-basin (Macae/RJ) pedological (B) and saprolitic soils (C) analysis. In order to do so, field recognition of erosive features was carried out, in which was found the predominance of cattle-tracks. In addition, disturbed and undisturbed soils samples were collected for physical, mineralogical and geotechnical characterization through direct shear tests with natural moisture content and flooded samples. The results of the direct shear tests, by means of cohesion variation acquired in these two moisture states show that the saprolitic soils are more erodible than the pedological ones, which was also corroborated by classification indexes related to grain size distribution and consistency and field observations which concluded that erosive features are predominant in C horizons. So, the study region is very susceptible to erosion unless there is an appropriate management and occupation policy, because the local pedological soils are very shallow and their erosion allow C horizons exposure, which are more erodible.

Long-term sorption and desorption of uranium in saprolite subsoil with nanoporous goethite

Long-term (2–3 months) batch U(VI) sorption-desorption experiments were conducted to understand the long-term sorption-desorption behavior of U(VI) in saprolite subsoils from Oak Ridge Field Research Center (ORFRC), Tennessee, which contained naturally occurring nanoporous goethite. Three subsoil samples containing a range of dithionite-citrate-bicarbonate (DCB) extractable Fe oxide content (7138, 11,161, and 22,582 mg Fe/kg) were used for the experiments. Sorption of 50 μM U(VI) to the subsoils in the presence of Ca2+ and HCO3− at circumneutral pH occurred rapidly during the first 2 days, after which slow U(VI) sorption continued over 3 months. U(VI) desorption from the soils by 10 mM NaHCO3 solution exhibited an initial fast desorption step during the first 24 h, followed by slower desorption over a week. Sorption of 50 μM U(VI) for 1 day to 3 months in the presence or absence of Ca2+ consistently resulted in higher U(VI) sorption to saprolite soil with higher amount of nanoporous goethite, while desorption of U(VI) for 1 week to 2 months was consistently lower in saprolite soil with higher amount of nanoporous goethite. Saprolite subsoils containing higher amounts of nanoporous goethite exhibited more resistant U(VI) desorption, and the proportions of irreversible U(VI) sorption increased with longer residence time with soils. These results indicates that more U(VI) became bound to the internal surfaces of nanoporous iron oxides during long-term sorption. This study suggests that naturally occurring nanoporous goethite may exert a significant role in controlling the mobility and transport of U(VI) in historically contaminated sites that have existed over decades.

Spatial variability of saprolitic soil properties and relationship with joint set orientation of parent rock: Insights from cases in Hong Kong

Geomaterials are known to be associated with significant heterogeneity, and the natural variations in properties can affect the occurrence of landslides and failure of engineering structures. While these variations are often observed to be spatially correlated, the correlation patterns and their relationships with the geological origins of the materials are not well understood. This study utilizes a three-dimensional spatial variability model to investigate the correlation features in mechanical properties of saprolitic soils, which are products of chemical weathering of granite. Rigorous geostatistical analyses are performed for soil test data at four locations in Hong Kong, each also consisting of extensive rock joint survey information. The analyses show that the principal directions of spatial variability in saprolitic soils correlate well with joint set orientations in the parent rock, providing quantitative evidence that soil heterogeneity partly arises from the different rates of weathering along various directions relative to the rock discontinuities.

Land Use‐Dependent Preferential Flow Paths Affect Hydrological Response of Steep Tropical Lowland Catchments With Saprolitic Soils

AbstractForested catchments in Central Panama can produce more base flow during the dry season compared to pasture catchments—the so‐called “forest sponge effect.” During rainfall events, peak storm runoff rates and storm runoff coefficients can be lower for forested catchments than pasture catchments, even when they have similar topographic characteristics, underlying geology, and soil texture. The internal mechanism of these differences in hydrological response due to land use is yet to be fully understood. A distributed model explicitly simulating preferential flow paths (PFPs), which is referred to as “PFPMod,” is used to explain the hydrological response caused by land use using data from three catchments with distinct land covers in Central Panama. Input parameters of forest and pasture land covers were identified using field observations and literature values. Multiple satisfactory objective criteria demonstrate that the two end‐member land cover parameter sets are adequate to explain the observed difference in dry‐season base flow and storm runoff coefficients. Field measurements of matrix infiltrability using soil cores and plot‐scale infiltration capacity enabled estimating the number of vertical macropores that fully penetrate the root zone. Model simulation results demonstrate that fast drainage through lateral PFPs in the early wet season and high flow in vertical PFPs to recharge deep groundwater in the late wet season contribute to the observed differences in peak storm runoff and the “forest sponge effect” during the dry season. This study provided insights to the mechanism by which reforestation may help to restore ecosystem services and water security in tropical settings.

Construction of Viable Soil Defined Media Using Quantitative Metabolomics Analysis of Soil Metabolites.

Exometabolomics enables analysis of metabolite utilization of low molecular weight organic substances by soil bacteria. Environmentally-based defined media are needed to examine ecologically relevant patterns of substrate utilization. Here, we describe an approach for the construction of defined media using untargeted characterization of water soluble soil microbial metabolites from a saprolite soil collected from the Oak Ridge Field Research Center (ORFRC). To broadly characterize metabolites, both liquid chromatography mass spectrometry (LC/MS) and gas chromatography mass spectrometry (GC/MS) were used. With this approach, 96 metabolites were identified, including amino acids, amino acid derivatives, sugars, sugar alcohols, mono- and di-carboxylic acids, nucleobases, and nucleosides. From this pool of metabolites, 25 were quantified. Molecular weight cut-off filtration determined the fraction of carbon accounted for by the quantified metabolites and revealed that these soil metabolites have an uneven quantitative distribution (e.g., trehalose accounted for 9.9% of the <1 kDa fraction). This quantitative information was used to formulate two soil defined media (SDM), one containing 23 metabolites (SDM1) and one containing 46 (SDM2). To evaluate the viability of the SDM, we examined the growth of 30 phylogenetically diverse soil bacterial isolates from the ORFRC field site. The simpler SDM1 supported the growth of 13 isolates while the more complex SDM2 supported 15 isolates. To investigate SDM1 substrate preferences, one isolate, Pseudomonas corrugata strain FW300-N2E2 was selected for a time-series exometabolomics analysis. Interestingly, it was found that this organism preferred lower-abundance substrates such as guanine, glycine, proline and arginine and glucose and did not utilize the more abundant substrates maltose, mannitol, trehalose and uridine. These results demonstrate the viability and utility of using exometabolomics to construct a tractable environmentally relevant media. We anticipate that this approach can be expanded to other environments to enhance isolation and characterization of diverse microbial communities.

Paleoproterozoic orogenesis and quartz-arenite deposition in the Little Chino Valley area, Yavapai tectonic province, central Arizona, USA

New field mapping and laboratory studies of Paleoproterozoic rock units around Little Chino Valley in central Arizona clarify the timing of magmatism, deformation, and sedimentation in part of the Yavapai tectonic province and yield new insights into sources of sands and weathering environments. Mafic lavas, calc-silicate rocks, and pelitic and psammitic strata in the Jerome Canyon area west of Little Chino Valley were deposited, deformed, and intruded by the 1736 ± 21 (2σ) Ma Williamson Valley Granodiorite. U-Pb geochronologic analysis of detrital zircons from a sample of psammitic strata yielded a maximum depositional age of ca. 1738 Ma. Approximately 25% of the detrital-zircon grains were derived from a ca. 2480 Ma source, as previously identified in Grand Canyon schist units. Kolmogorov-Smirnov statistical comparison of the Jerome Canyon detrital-zircon analyses with Grand Canyon schist analyses indicates that three of the 12 samples analyzed by Shufeldt et al. (2010) are statistically indistinguishable from the Jerome Canyon sample at the 95% confidence level and supports the concept that the Jerome Canyon sequence and Paleoproterozoic schists in the eastern and western Grand Canyon are part of the same tectonostratigraphic terrane. The Del Rio Quartzite on the northeast side of Little Chino Valley, previously considered an outlier of Mazatzal Quartzite, consists of poorly sorted quartz arenite, pebbly quartz arenite, and conglomerate deposited in a braided-stream environment. Microscope examination of 32 thin sections stained for potassium and calcium failed to identify any feldspar, mica, or mafic silicate grains. Similarly, conglomerate clasts consist entirely of vein quartz and less abundant argillite and jasper. A rock unit interpreted as a paleosol beneath the Del Rio Quartzite contains no surviving minerals except quartz, some of which is embayed and rounded as in corrosive saprolitic soils. U-Pb geochronologic analyses of detrital zircons from the 1400-m-thick Quartzite indicate maximum depositional ages of ca. 1745 Ma for the base and ca. 1737 Ma for the top. The unit is folded but is unaffected by the penetrative deformation and metamorphism that affected other Paleoproterozoic volcanic and sedimentary strata in the area, and it is probably significantly younger. We infer that the physically immature but chemically super-mature Del Rio Quartzite was deposited during a time of extreme weathering during a hot, humid climate with exceptionally high atmospheric CO 2 concentrations and associated corrosive rainwater rich in carbonic acid.

Mechanisms of compression in well-graded saprolitic soils

Soils originating from weathering processes present considerable heterogeneity in their composition, which can make it difficult to analyse their behaviour in a systematic way. For the granitic saprolites discussed in this paper, based on a trend between soil density and weathering degree, there appears to be two different domains of behaviour, a granular domain and a clay matrix one, according to the degree of weathering reached. Recognition of these domains can reduce the apparent scatter of data for the engineering behaviour of weathered soils. A number of one-dimensional compression tests are presented for saprolitic soils from Hong Kong having different weathering degrees. In addition, isotropic and one-dimensional compression tests from the literature on other saprolites from Hong Kong and around the world were reanalysed and used to identify possible trends in the mechanisms of compression for these two domains. From practical considerations, the trends considered were between compressibility and common engineering grading descriptors. An attempt was also made to provide the physical explanations behind the behaviour observed, and the particle breakage was investigated in detail, both from a quantitative and qualitative point of view. It was found that the values of relative breakage (Hardin in ASCE J Geotech Geoenviron Eng 111(10):1177–1192, 1985), for a same stress level, might be very similar for soils having different compressibility values and different initial gradings. When studying particle breakage in further detail, it can be observed that it is linked to the amount of large particles and their characteristics. The maximum particle size, rather than the amount of fines in a mixture, may be a better predictor for differences in compressibility and breakage.

Influence of structure in the soil-water characteristic curves of two residual soils of granite

This paper discusses the influence of structure in the soil-water characteristic curves (SWCC) of two residual soils of granite formed in a subtropical environment. One soil has a saprolitic nature (named GrSp) and the other shows lateritic behavior (named GrLt). Both materials occur on a slope which presents a extensive history of landslides in the municipality of Sao Jose, Southern Brazil. SWCC of undisturbed and remolded specimens were determined using the filter-paper technique. Undisturbed specimens were collected and remolded specimens were produced by static compression of disintegrated soil to the same void ratio and moisture content of undisturbed specimens. SWCC of saprolitic soil showed curves which were modelled as unimodal but the lateritic soil required the use of bimodal curves because of the structure developed in micro and macro levels. Suction levels measured in GrLt soil were higher than in saprolitic soil. Remolding process changed the levels of suction achieved, which is due to the structure and more specifically to the size of pores in the remolded soils. Hysteresis were verified in both materials, but were far more pronounced in the lateritic soil. Analysis of mercury intrusion porosimetry were carried out in GrSp soil. They showed that remolding generates a different pore distribution from the existing in the undisturbed soil.

Solos: Subsídio Para Estudos de Geologia de Engenharia

The objective of this paper was to discuss in simplified and multidisciplinary terms and through an engineering geology point of view the different variables related to the development of residual, transported, organic, expansive and lateritic soils, contributing to standardize concepts of geotechnical interest mineralogical and chemical data from five profiles whose respective saprolitic soils were formed by the action of weathering processes on gneissic metamorphic rocks in tropical and subtropical climatic environment were presented and discussed. The residual soils developed from these rock, besides the great abundance in the state of Rio de Janeiro, have thicknesses greater than 10 meters, being associated with large landslides and mass movements occurred in the last 50 years both in that state and in others. The article emphasizes finally that the presence of relict heterogeneities in saprolitic soils and saprock inherited from their source rocks should not be discarded in the analysis of slope stability and foundations projects.

Field investigation of deformation characteristics and stress mobilisation of a soil slope

Stress mobilisation and deformation of a slope are important for engineers to carry out reliable design of retaining systems. However, most case histories reported mainly on the response of pore water pressure (PWP), whereas knowledge about the stress deformation characteristics of slope is limited. In this study, a saprolitic soil slope was instrumented to monitor not only the responses of PWP but also horizontal stress and horizontal displacement. To assist in the interpretation of field data, a series of laboratory tests was conducted to characterise volume change behaviour of the soil taken from the site, under the effects of both net stress and suction. During a rainstorm event when positive PWP built up, a remarkably large displacement of 20 mm was recorded between 5.5- and 6-m depths, and the top 5 m of the slope exhibited translational downslope movement. This caused an increase in Bishop’s effective horizontal stress by 350 %, which reached a peak value close to 40 % of a Bishop’s effective passive stress. During the subsequent dry season when suction was recovered, an upslope rebound of 10 mm was recorded. Comparison of field and laboratory data reveals that the rebound was attributed to suction-induced soil shrinkage. This rebound led to a decrease in the Bishop’s effective horizontal stress previously built up during the storm event.